GNVC Genvec, Inc.

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

TO BE HELD ON JUNE 15, 2017

TO THE SHAREHOLDERS OF GENVEC, INC.:

Notice is hereby given that a special meeting of the shareholders of GenVec, Inc., a Delaware corporation, referred to herein as GenVec, will be held at 8:30 a.m. Eastern Daylight Time, on June 15, 2017 at GenVec’s offices located at 910 Clopper Road, Suite 220N, Gaithersburg, Maryland 20878.

The purposes of the meeting are to:

The proxy statement/prospectus accompanying this notice, including the annexes thereto, contains further information with respect to the business to be transacted at the special meeting. We encourage you to read the accompanying proxy statement/prospectus, including any documents incorporated by reference, and the annexes carefully. The accompanying proxy statement/prospectus is a part of this notice.

GenVec’s board of directors has fixed the close of business on April 28, 2017 as the record date for the determination of shareholders entitled to notice of, and to vote at, the special meeting and at any adjournment of the special meeting. A complete list of shareholders of record of GenVec entitled to vote at the special meeting will be available for ten days prior to the special meeting at GenVec’s executive offices and principal place of business at 910 Clopper Road, Suite 220N, Gaithersburg, Maryland 20878, for inspection by shareholders of GenVec during ordinary business hours for any purpose germane to the special meeting. The list will also be available at the special meeting for examination by any shareholder of record of GenVec present at the special meeting.

You are cordially invited to attend the special meeting. Your proxy is being solicited by GenVec’s board of directors. Adoption of the merger agreement requires the affirmative vote of the holders of a majority of the outstanding shares of GenVec common stock. Your vote is very important. We cannot complete the merger unless the merger agreement is adopted by the affirmative vote of the holders of a majority of the outstanding shares of GenVec common stock. A failure to vote on the proposal to adopt the merger agreement has the same effect as a vote by you AGAINST the adoption of the merger agreement. Whether or not you expect to attend the special meeting in person, we urge you to review the enclosed materials and request that you submit your proxy as promptly as possible (i)  by telephone according to the instructions on the enclosed proxy card or (ii)  by completing, signing, dating and returning the enclosed proxy card. Your proxy may be revoked by you at any time before the vote at the special meeting by following the procedures outlined in the accompanying proxy statement/prospectus. If your shares are held in “street name,” meaning that your shares are held by a broker, bank, or other nominee, you should follow the instructions provided by such nominee.

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THE BOARD OF DIRECTORS OF GENVEC UNANIMOUSLY RECOMMENDS THAT YOU VOTE “FOR” THE MERGER PROPOSAL, “FOR” THE COMPENSATION PROPOSAL, AND “FOR” THE ADJOURNMENT PROPOSAL.

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Additional information

This proxy statement/prospectus incorporates important business and financial information about Intrexon from other documents filed with the U.S. Securities and Exchange Commission, referred to herein as the SEC, that are not included in or delivered with this proxy statement/prospectus. For a listing of documents incorporated by reference into this proxy statement/prospectus, see the section entitled “Where you can find more information.” This information is available to you without charge upon your request. This information is available for you to review at the SEC’s public reference room located at 100 F Street, N.E., Room 1580, Washington, DC 20549, and through the SEC’s website at www.sec.gov. You can also obtain the documents incorporated by reference into this proxy statement/prospectus by requesting them in writing or by telephone from Intrexon at the following address and telephone number:

Intrexon Corporation

20374 Seneca Meadows Parkway

Germantown, MD 20876

(301) 556-9900

Attn: Investor Relations

Investors may also consult Intrexon’s website for more information concerning Intrexon and the merger described in this proxy statement/prospectus. Intrexon’s website is www.dna.com . Information included on Intrexon’s website is not incorporated by reference into this proxy statement/prospectus.

To receive timely delivery of requested documents in advance of the special meeting of GenVec shareholders, please make your request no later than June 8, 2017 (five business days before the date of the special meeting).

About this document

This document, which forms part of a Registration Statement on Form S-4 filed by Intrexon with the SEC, constitutes a prospectus of Intrexon under Section 5 of the Securities Act of 1933, as amended, which we refer to as the Securities Act, with respect to the shares of Intrexon common stock to be issued to GenVec shareholders pursuant to the merger agreement. This document also constitutes a proxy statement of GenVec under Section 14(a) of the Securities Exchange Act of 1934, as amended, which we refer to as the Exchange Act, with respect to the special meeting of GenVec shareholders at which such shareholders will be asked to vote upon the proposal to adopt the merger agreement, among other proposals.

No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this proxy statement/prospectus and neither Intrexon nor GenVec takes any responsibility for any information that others may give you. You should not assume that the information contained in, or incorporated by reference into, this proxy statement/prospectus is accurate as of any date other than the date of this proxy statement/prospectus or the date of the SEC filing incorporated by reference herein, as applicable. Neither the mailing of this proxy statement/prospectus to GenVec shareholders nor the issuance by Intrexon of common stock in connection with the merger will create any implication to the contrary.

This proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction in which or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Information contained in this proxy statement/prospectus regarding Intrexon has been provided by Intrexon and information contained in this proxy statement/prospectus regarding GenVec has been provided by GenVec.

All references in this proxy statement/prospectus to: “GenVec” refer to GenVec, Inc., a Delaware corporation; “Intrexon” refer to Intrexon Corporation, a Virginia corporation, and its subsidiaries; “Merger Sub” refer to Intrexon GV Holding, Inc., a Delaware corporation and a wholly owned subsidiary of Intrexon formed solely for

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the purpose of effecting the merger as described in this proxy statement/prospectus; and the “combined company” refer to Intrexon and each of its subsidiaries, including GenVec, immediately following completion of the transactions contemplated by the merger agreement.

All references in this proxy statement/prospectus to the “merger agreement” refer to the Agreement and Plan of Merger, dated as of January 24, 2017, by and among Intrexon, Merger Sub and GenVec, a copy of which is included as Annex A to this proxy statement/prospectus, as it may be amended from time to time, and all references to the “merger” refer to the merger of Merger Sub with and into GenVec, with GenVec continuing as the surviving corporation.

Although Delaware law generally refers to the term “stockholders” and Virginia law generally refers to the term “shareholders” to specify holders of the capital stock of a corporation, for convenience such holders are referred to in this proxy statement/prospectus as shareholders in accordance with the Virginia law terminology.

As described in further detail below in the section entitled “GenVec management’s discussion and analysis of financial condition and results of operations—Liquidity and Capital Resources—NASDAQ Notifications and Reverse Stock Split,” on December 1, 2016, GenVec effected a reverse stock split, which we refer to as the reverse stock split, of its outstanding common stock at a ratio of one-for-ten, whereby each ten shares of common stock were combined into one share of common stock. Unless otherwise noted, all share and per share amounts relating to GenVec common stock, GenVec stock options or warrants to purchase GenVec common stock, and the respective exercise prices of each such option or warrant, included within this proxy statement/prospectus have been retroactively adjusted to reflect the reduced number of shares resulting from the reverse stock split.

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Questions and answers about the special meeting

The following are some questions that you, as a shareholder of GenVec, may have regarding the special meeting of GenVec shareholders, which we refer to as the special meeting, the merger and the other matters being considered at the special meeting, as well as brief answers to those questions. GenVec urges you to read carefully the remainder of this proxy statement/prospectus because the information in this section does not provide all the information that might be important to you with respect to the special meeting, the merger and the other matters being considered at the special meeting. Additional important information is also contained in the annexes to and the documents incorporated by reference into this proxy statement/prospectus. See the section entitled “Where you can find more information.”

You are receiving this proxy statement/prospectus because you have been identified as a shareholder of GenVec as of the close of business on the record date for the special meeting, which is April 28, 2017. This document serves as both a proxy statement of GenVec, used to solicit proxies for the special meeting of GenVec shareholders, and as a prospectus of Intrexon, used to offer shares of Intrexon common stock to GenVec shareholders in exchange for shares of GenVec common stock pursuant to the terms of the merger agreement. This document contains important information about the merger, the shares of Intrexon common stock to be issued and contingent payment rights, which we refer to as CPRs, to be received pursuant to the merger and the special meeting of GenVec shareholders, and you should read it carefully. The enclosed proxy materials allow GenVec shareholders to submit their proxy without attending the special meeting in person.

In addition, you are being asked to vote on a proposal to approve, on a non-binding, advisory basis, compensation that will or may become payable to GenVec’s named executive officers in connection with the merger, which we refer to as the merger-related compensation proposal.

You are also being asked to vote on a proposal to adjourn the special meeting, if necessary or appropriate, to solicit additional proxies in favor of the merger proposal, which we refer to as the adjournment proposal.

Your vote is important. We encourage you to vote as soon as possible.

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GenVec shareholders will not receive any fractional shares of Intrexon common stock in the merger. Instead, any shareholder who would otherwise be entitled to a fractional share of Intrexon common stock will be entitled to receive an amount in cash, without interest, equal to the product of such fraction multiplied by the last reported sale price of Intrexon common stock on the New York Stock Exchange, referred to herein as NYSE, on the last complete trading day prior to the effective time of the merger.

In particular, each CPR represents the right to receive an amount in cash (or, as described below, in certain circumstances, shares of Intrexon common stock) equal to (i) 50% of (a) all milestone payments, if any, received by Intrexon or the surviving corporation for milestones that are achieved or occur under the NVS License Agreement during such 36-month contingent payment period, and (b) all royalty payments, if any, received by Intrexon or the surviving corporation under the NVS License Agreement during such 36-month contingent payment period, divided by (ii) all then-outstanding CPRs.

See the section entitled “Contingent payment rights agreement.” You should also read the form of the contingent payment rights agreement included as Annex B to this proxy statement/prospectus for more information on the terms of the CPRs.

On January 23, 2017, the last trading day prior to the public announcement of the proposed merger, the closing price of Intrexon common stock on the NYSE was $22.09 per share. On May 8, 2017, the latest practicable date before the date of this proxy statement/prospectus, the closing price of Intrexon common stock on the NYSE was $19.36 per share. We encourage you to obtain a current market quotation before voting your shares.

The amount of consideration payable to GenVec shareholders in connection with the CPRs will ultimately depend on (i) whether any milestones are achieved or occur under the NVS License Agreement within 36 months after the effective time of the merger, and, if so, whether any milestone payments are made under the NVS License Agreement with respect to such milestones, and (ii) whether any royalty payments are made under the NVS License Agreement within 36 months after the effective time of the merger. If such milestone or royalty payments are made, then the amount of consideration so payable will depend on the aggregate amount of (a) milestone payments received by Intrexon or the surviving corporation for milestones that are achieved or occur, and (b) royalty payments received by Intrexon or the surviving corporation, in each case, under the NVS License Agreement within 36 months after the effective time of the merger. See the section entitled “Contingent payment rights agreement.”

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A holder of a CPR will be entitled to receive payments from Intrexon, if (i) Intrexon or the surviving corporation receives milestone payments for milestones that are achieved or occur and/or (ii) Intrexon or the surviving corporation receives royalty payments, in each case, during the 36-month period following the effective time of the merger.

At the effective time of the merger, each outstanding, unexpired and unexercised warrant to purchase shares of GenVec common stock will be assumed by Intrexon and converted into a warrant to purchase, at an aggregate exercise price equal to the aggregate exercise price of the warrant as of immediately prior to the effective time of the merger, and in lieu of the shares of GenVec common stock otherwise issuable upon exercise of such warrant, the applicable merger consideration (including shares of Intrexon common stock and CPRs) that would have been receivable upon consummation of the merger by the holder of such warrant if such warrant had been exercised immediately prior to the effective time of the merger. The other pre-existing terms of the warrants will continue to apply in accordance with their terms following the merger. See the section entitled “The merger agreement—Treatment of GenVec stock options and warrants.”

If the merger agreement is terminated under specified circumstances, GenVec would be required to pay Intrexon a termination fee of $550,000 or reimburse Intrexon for its reasonable out-of-pocket expenses (not to exceed $400,000). In addition, if (i) GenVec willfully breaches certain pre-closing covenants in the merger agreement and (ii) GenVec is otherwise required to reimburse Intrexon’s out-of-pocket expenses as described in the foregoing sentence, then GenVec would also be obligated to pay Intrexon an additional $200,000. See the section entitled “The merger agreement—Termination fee” and the section entitled “The merger agreement—Costs and expenses.”

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Voting by Proxy

Registered shareholders may vote by mail or by telephone:

If your shares are held of record in “street name,” meaning that your shares are held by a broker, bank or other nominee, you should follow the separate instructions that such nominee provides to you. Although most banks and brokers now offer telephone and Internet voting, availability and specific processes will depend on their voting arrangements.

If the special meeting is postponed or adjourned for any reason, at any subsequent reconvening of the special meeting all proxies will be voted in the same manner as the proxies would have been voted at the original convening of the special meeting, except for any proxies that have at that time effectively been revoked or withdrawn, even if the proxies had been effectively voted on the same or any other matter at a previous meeting.

Voting in Person at the Special Meeting

If you are a registered holder and attend the special meeting and wish to vote in person, you may request a ballot when you arrive. If your shares are held in street name by a broker, bank or other nominee, and you would like to vote in person at the special meeting, you must bring to the special meeting (i) a letter, account statement or other evidence from such broker, bank or other nominee indicating that you were the beneficial owner of the shares on the record date for the special meeting and (ii) a legal proxy from the record holder of the shares of GenVec common stock (i.e., your broker, bank or nominee) authorizing you to vote at the special meeting.

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The GenVec board of directors unanimously recommends that GenVec’s shareholders vote “ FOR ” the merger proposal, “ FOR ” the merger-related compensation proposal and “ FOR ” the adjournment proposal.

If you are a shareholder of record and vote “Abstain” on the merger proposal, the merger-related compensation proposal or the adjournment proposal, it will have the same effect as voting against such proposal. Likewise, if your shares are held in street name and you instruct your broker, bank or other nominee to vote “Abstain” on the merger proposal, the merger-related compensation proposal or the adjournment proposal, it will have the same effect as voting against such proposal.

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If your shares are held in “street name,” meaning that your shares are held by a broker, bank or other nominee, you should contact such broker, bank or other nominee to change your vote.

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Risk factors

By voting in favor of the merger proposal, GenVec shareholders will be choosing to invest in Intrexon common stock following the consummation of the merger. An investment in Intrexon common stock involves a high degree of risk. In addition to the other information included and incorporated by reference in this proxy statement/prospectus, including the matters addressed in the section entitled “Cautionary note regarding forward-looking statements”, you should carefully consider the following risks described below in evaluating whether to vote to approve the merger proposal. In addition, you should read carefully and consider the risks associated with the businesses of each of Intrexon and GenVec because these risks will also affect the combined company. Information on risks associated with GenVec’s business can be found below. Information on risks associated with Intrexon’s business can be found in Intrexon’s Annual Report on Form 10-K for the year ended December 31, 2016 as updated by any subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, which are filed with the SEC and incorporated by reference into this proxy statement/prospectus. For further information regarding the documents incorporated into this proxy statement/prospectus by reference, see the section entitled “Where you can find more information.” Realization of any of the risks described below, any of the events described under “Cautionary note regarding forward-looking statements” or any of the risks or events described in the documents incorporated by reference could have a material adverse effect on Intrexon’s, GenVec’s, or the combined company’s businesses, financial condition, cash flows and results of operations and could result in a decline in the trading prices of their respective common units.

Risks related to the merger

Failure to consummate the merger could negatively impact the stock price and the future business and financial results of Intrexon and GenVec.

The merger agreement contains a number of customary conditions to closing, including the accuracy of Intrexon’s and GenVec’s representations and warranties to varying standards, the performance of each company’s covenants, the absence of any legal prohibitions to closing, the adoption of the merger agreement by GenVec shareholders and certain other conditions. Many of the conditions to closing are not within either Intrexon’s or GenVec’s control and neither company can predict when or if these conditions will be satisfied.

If any condition to the merger is not satisfied or waived, it is possible that the merger will not be consummated in the expected time frame or at all. In addition, Intrexon and GenVec may terminate the merger agreement under certain circumstances even if the merger agreement is adopted by GenVec shareholders, including if the merger has not been completed, subject to certain conditions, on or before July 24, 2017. If the merger is not completed for any reason, the ongoing businesses of Intrexon and GenVec may be adversely affected and the companies will be subject to several risks, including the following:

If the merger agreement is terminated, Intrexon or GenVec may be unable to find another party willing to engage in a similar transaction on terms as favorable as those set forth in the merger agreement, or at all. The negative publicity that could accompany such a termination could adversely impact GenVec’s ability to find an alternate partner for a strategic transaction or to obtain required financing for any such transaction.

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In addition, although Intrexon and GenVec are not aware of any material governmental approvals, waivers or actions that are required to complete the merger, if any such approvals, waivers or actions are required, there can be no assurance, that any such waivers, approvals or actions will be obtained.

Failure to complete the merger could result in a decrease in the market price of GenVec common stock to the extent that the current market price of those shares reflects a market assumption that the merger will be completed. In addition, neither company would realize any of the expected benefits of having completed the merger. Further, failure to complete the merger could result in damage to GenVec’s reputation and business relationships. GenVec could also be subject to litigation related to any failure to consummate the merger or related to any enforcement proceedings commenced against GenVec to perform its obligations under the merger agreement.

Therefore, a failure to consummate the merger could materially and adversely affect Intrexon’s or GenVec’s business, financial results and stock price, and could limit each company’s ability to pursue its strategic goals.

GenVec has suffered recurring losses from operations and has an accumulated deficit, which raises substantial doubt about its ability to continue as a going concern, and, if the merger is not consummated, absent additional financing, GenVec may be unable to remain a going concern.

GenVec has suffered recurring losses from operations and has an accumulated deficit. If the merger is not consummated and GenVec is unsuccessful in its efforts to raise additional capital, based on GenVec’s current levels of operating expenses, GenVec’s current capital is not expected to fund its operations for the next twelve months. These conditions raise substantial doubt about GenVec’s ability to continue as a going concern. The Report of Independent Registered Public Accounting Firm at the beginning of the GenVec’s audited financial statements included in this proxy statement/prospectus includes an explanatory paragraph about GenVec’s ability to continue as a going concern.

The financial statements of GenVec included herein were prepared on the basis of a going concern, which contemplates that GenVec will be able to realize its assets and discharge liabilities in the normal course of business. GenVec’s financial statements do not include any adjustments that might be necessary if GenVec is unable to continue as a going concern. In addition, GenVec’s financial situation and the presence of an explanatory paragraph about GenVec’s ability to continue as a going concern could make it more difficult to raise the capital necessary to address GenVec’s current needs.

Because the market price of Intrexon common stock will fluctuate, you cannot be sure of the market value of the shares of Intrexon common stock you will receive in the merger.

Upon completion of the merger, each share of GenVec common stock that you hold will be converted into the right to receive the per share merger consideration consisting of (i) 0.297 shares of Intrexon common stock plus (ii) one CPR. There will be no adjustment to the per share merger consideration due to changes in the market price of either shares of GenVec common stock or shares of Intrexon common stock and the merger agreement does not provide for any price-based termination right. Accordingly, the market value of the shares of Intrexon common stock that you will be entitled to receive upon completion of the merger will depend on the market value of the shares of Intrexon common stock at the time of the completion of the merger and could vary significantly from the market value on the date of this proxy statement/prospectus or the date of the special meeting. In addition, the market value of the shares of Intrexon common stock that you will be entitled to receive in the merger with respect to the stock consideration also will continue to fluctuate after the completion of the merger and you could lose the value of your investment in Intrexon common stock.

Such variations could be the result of changes in the business or operations of GenVec or Intrexon prior to the merger and Intrexon following the merger, market assessments of the likelihood that the merger will be completed or the timing of the completion of the merger, general market and economic conditions and other

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factors both within and beyond the control of GenVec or Intrexon. Because the merger will be completed after the special meeting, at the time of the meeting you will not know the value of the merger consideration that you will receive upon completion of the merger.

The contingent payment rights may not result in payments to holders.

Under the terms of the merger agreement, each share of GenVec common stock issued and outstanding immediately prior to the effective time of the merger (other than shares with respect to which appraisal rights are properly exercised or shares owned by Intrexon, any of its subsidiaries or GenVec), and each share of GenVec common stock underlying a warrant to purchase shares of GenVec common stock that is converted into a warrant to purchase merger consideration in connection with the merger, will, upon the effective time of the merger or, with respect to a warrant, upon the exercise of such warrant, be converted into the right to receive 0.297 of a share of Intrexon common stock and a CPR that entitles the holder to receive, without interest and subject to applicable withholding tax, a portion of (i) milestone payments received by Intrexon or the surviving corporation for milestones that are achieved or occur, and (ii) royalty payments received by Intrexon or the surviving corporation, in each case, under the NVS License Agreement within 36 months after the closing of the merger. As of the date hereof, the first four development and regulatory milestones under the NVS License Agreement have been met. As of the date hereof, GenVec has not received any royalty payments from Novartis under the NVS License Agreement. GenVec cannot determine whether any milestones will be achieved or occur within the 36-month period after the closing of the merger, and it does not expect that any royalty payments will be made during that period. Accordingly, neither Intrexon nor GenVec can assure you that any milestone or royalty payments will be received by Intrexon or the surviving corporation after the date hereof. If these payment events do not occur, no payments will be made under the contingent payment rights agreement. Accordingly, the CPRs may ultimately have no value and expire without yielding any payments to holders of CPRs. It is difficult to value the CPRs, and the amount of actual payments on the CPRs is highly speculative.

You will not be able to determine the amount of payment (if any) to be received under the contingent payment rights until certain milestone or royalty payments have been made by Novartis.

If any payment is made on the CPRs, it will not be made until certain milestones are achieved or occur or certain royalty payments are earned under the NVS License Agreement and Intrexon or the surviving corporation has received payments for such milestones or royalties. GenVec cannot determine whether any milestones will be achieved or occur within the 36-month period after closing of the merger, and it does not expect that any royalty payments will be made during that period. After receipt of such amounts (if any), the holders of the CPRs would collectively be entitled to receive 50% of the amounts received by Intrexon or the surviving corporation in respect of such milestone or royalty payments. There is no guarantee that any milestones will be achieved or occur or that any milestone or royalty payments will be made under the NVS License Agreement.

The contingent payment rights are not registered and may not be transferred except in certain limited circumstances.

The CPRs that will be issued as part of the merger consideration, or upon exercise of each warrant to purchase shares of GenVec common stock that is converted into a warrant to purchase merger consideration in connection with the merger, will not be registered under the Securities Act and will not be listed on any exchange. Intrexon does not intend to, and is not obligated to, register the CPRs or list them on an exchange. Subject to certain limited exceptions, holders of CPRs will not be able to transfer or sell the CPRs. As a result, GenVec shareholders should anticipate holding the CPRs until such time as they expire. In addition, until such time as any royalty or milestone payments are made under the NVS License Agreement (if any), the CPRs will be difficult to value and may not ultimately result in any additional amounts being payable to the GenVec shareholders.

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The U.S. federal income tax treatment of the merger depends, in part, upon the aggregate amount of the consideration received by the holders of the GenVec common stock and the aggregate amount of such consideration that is paid in cash (rather than shares of Intrexon common stock).

Pursuant to the terms of the merger agreement, Intrexon and GenVec agreed not to take any action that would reasonably be expected to prevent or impede the merger from qualifying as a “reorganization” within the meaning of Section 368(a) of the Code. However, the qualification of the merger as a reorganization depends on compliance with numerous technical requirements of these provisions of the Code not all of which can be finally determined at this time, most specifically whether holders of GenVec common stock will receive a sufficient amount of Intrexon voting common stock to satisfy the “control test” set forth in Section 368(a)(2)(E) of the Code.

Under the contingent payment rights agreement, the holders of the GenVec common stock are entitled to receive 50% of the amounts actually received by GenVec under the NVS License Agreement as royalty payments or milestone payments during the 36-month period following the signing of the merger agreement. As of the date hereof, GenVec has not received any royalty payments from Novartis under the NVS License Agreement. In addition, as of the date hereof, GenVec cannot determine whether any milestones under the NVS License Agreement will be achieved or occur within the 36-month period after the closing of the merger. Neither Intrexon nor GenVec can assure you that any milestone or royalty payments will be received by Intrexon or the surviving corporation after the date hereof. Accordingly, at the effective time of the merger, the aggregate amount of consideration to be received by the holders of the GenVec common stock will not be known (and will not be determinable) because the aggregate amount (if any) paid to the holders of the GenVec common stock will not be known until after the expiration of the 36-month period following the signing of the merger agreement.

Moreover, the contingent payment rights agreement provides that the CPRs are to be paid in cash unless any such payment would prevent the transactions contemplated by the merger agreement from being treated as a tax free reorganization, in which case Intrexon would issue shares of its common stock in lieu of payment in cash of such amounts determined to be payable under the contingent payment rights agreement. But, the contingent payments rights agreement also limits the number of Intrexon common shares that may be issued in connection with the reorganization. Once this limit is met, all additional payments under the contingent rights agreement will be made in cash. As a result, the actual amount of consideration to be received by the holders of the GenVec common stock and the amount of such consideration that is paid in cash is not currently known (and will not be known) until following the expiration of the 36-month period.

Tax matters are very complicated, and the tax consequences of the merger to a particular GenVec shareholder will depend in part on such shareholder’s circumstances. Accordingly, you are urged to consult your own tax advisor for a full understanding of the tax consequences of the merger to you, including the applicability and effect of federal, state, local and foreign income and other tax laws.

Due to these uncertainties, the tax treatment of the merger is unclear and uncertain.

Moreover, the U.S. federal income tax treatment of the contingent payment rights is unclear.

The tax treatment of CPRs could impact whether or not the merger will qualify as a reorganization under Section 368(a) of the Code. In that regard, there is no legal authority directly addressing the U.S. federal income tax classification of a CPR or the treatment of payments that may be received pursuant to a CPR. Accordingly, the impact of CPRs on the tax treatment of the merger and the amount, timing and character of any gain, income or loss with respect to the CPRs are uncertain. Due to the legal and factual uncertainties regarding the tax treatment of CPRs, GenVec shareholders are urged to consult their own tax advisers to determine the timing and characterization of income, gain or loss resulting from receipt of payments (if any) pursuant to the CPRs. See the section entitled “Material U.S. federal income tax consequences of the merger.”

Tax matters are very complicated, and the tax consequences of the merger to a particular GenVec shareholder will depend in part on such shareholder’s circumstances. Accordingly, you are urged to consult your own tax

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advisor for a full understanding of the tax consequences of the merger to you, including the applicability and effect of federal, state, local and foreign income and other tax laws.

If the merger is consummated, Intrexon may not realize the anticipated benefits of the merger.

The success of the GenVec acquisition, if completed, will depend, in part, on Intrexon’s ability to realize the anticipated benefits from combining GenVec’s business with Intrexon’s business, including the ability to expand on GenVec’s expertise in adenoviral vectors and the current Good Manufacturing Practices, which we refer to as cGMP, of the U.S. Food and Drug Administration, which we refer to as the FDA, drug product manufacturing to enhance Intrexon’s gene transfer capabilities and to expedite the design and production of vectors that complement Intrexon’s multigene programming and focus on safety with limited off-target effect. The combined company will require additional resources to accomplish Intrexon’s goals for the merger, and Intrexon may not have the resources to accomplish these goals, or may choose to spend those resources on other business opportunities.

Integrating operations will be complex and will require significant efforts and expenditures on the part of both Intrexon and GenVec. Intrexon’s management might have its attention diverted while trying to integrate operations and corporate and administrative infrastructures. GenVec will continue to operate independently of Intrexon until the closing of the acquisition, which is expected to take place in the second quarter of 2017. The integration process could result in the loss of key employees, the disruption of each company’s ongoing businesses, tax costs or inefficiencies, or inconsistencies in standards, controls, information technology systems, procedures and policies, any of which could adversely affect Intrexon’s and GenVec’s ability to maintain relationships with customers, employees or other third parties or Intrexon’s ability to achieve the anticipated benefits of the GenVec acquisition and could harm Intrexon’s financial performance.

If Intrexon is unable to successfully or timely integrate the operations of GenVec’s business into Intrexon’s business, Intrexon may be unable to realize the anticipated benefits resulting from the proposed acquisition and its business and results of operations could be adversely affected.

The pendency of the merger could adversely affect the business and operations of each of Intrexon and GenVec.

Some customers and collaborators of each of Intrexon and GenVec may delay or defer decisions because of uncertainties or lack of understanding about the merger’s potential effect on their businesses, which could negatively impact the revenues, earnings, cash flows and expenses of Intrexon and/or GenVec, regardless of whether the merger is completed. Similarly, current and prospective employees of Intrexon and GenVec may experience uncertainty about their roles with the combined company following the merger, which may materially adversely affect the ability of each of Intrexon and GenVec to attract, retain and motivate key personnel during the pendency of the merger and which may materially adversely divert attention from the daily activities of Intrexon and GenVec’s existing employees.

Intrexon will incur significant transaction costs as a result of the merger.

Intrexon expects to incur significant one-time transaction costs related to the merger. These transaction costs include legal and accounting fees and expenses and filing fees, printing expenses and other related charges. Intrexon may also incur additional unanticipated transaction costs in connection with the merger. A portion of the transaction costs related to the merger will be incurred regardless of whether the merger is completed. Additional costs will be incurred in connection with integrating the two companies’ businesses. Costs in connection with the merger and integration may be higher than expected. These costs could adversely affect Intrexon’s financial condition, operating results or prospects of the combined company.

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The merger agreement limits GenVec’s ability to pursue alternatives to the merger.

Under the merger agreement, GenVec agreed not to, beginning on the date of the merger agreement, (i) solicit alternative acquisition proposals or (ii) engage or participate in discussions or negotiations with, or provide non-public information to, any person relating to any such alternative acquisition proposal, subject to certain limited exceptions. Intrexon generally has an opportunity to offer to modify the terms of the proposed merger in response to any competing acquisition proposal that may be made before the GenVec board of directors may withdraw or change its recommendation to GenVec’s shareholders.

If the merger agreement is terminated in certain circumstances, GenVec would be required to pay Intrexon a termination fee equal to $550,000. See the section entitled “The merger agreement—Covenants regarding alternative acquisition proposals” and “The merger agreement—Termination fee.” In addition, if the merger agreement is terminated under certain circumstances, GenVec would be required to compensate Intrexon for its actual reasonable out-of-pocket costs and expenses up to $400,000, plus an additional expense amount equal to $200,000. See the section entitled “The merger agreement—Costs and expenses.”

These provisions could discourage a third party that might have an interest in acquiring all or a significant part of GenVec from considering or proposing such an acquisition, even if it were prepared to pay consideration with a higher per share cash or market value than that market value proposed to be received or realized in the merger, or could result in a third party proposing to pay a lower price than it might otherwise have proposed to pay because of the added expense of the termination fee (or the expense reimbursement and additional expense amount) that becomes payable to Intrexon in certain circumstances.

If the merger agreement is terminated and GenVec decides to seek another business combination, it may not be able to negotiate a transaction with another party on terms comparable to, or better than, the terms of the merger.

Under the terms of the merger agreement, GenVec is subject to certain restrictions on its business activities.

The merger agreement generally requires GenVec to operate its business in the ordinary course pending consummation of the merger, and restricts GenVec from taking certain specified actions until the merger is completed. These restrictions may prevent GenVec from making desirable expenditures, including capital expenditures, pursuing otherwise attractive business opportunities and making other changes to its business prior to completion of the merger or termination of the merger agreement. See the section entitled “The merger agreement—Covenants—Interim conduct of GenVec’s business.”

Certain executive officers and directors of GenVec may have interests in the merger that may differ from, or are in addition to, the interests of GenVec shareholders.

Executive officers of GenVec negotiated the terms of the merger agreement and the GenVec board of directors unanimously determined that the merger agreement, the merger and the other transactions contemplated by the merger agreement are fair and advisable to, and in the best interest of, GenVec and its shareholders, unanimously approved the execution, delivery and performance by GenVec of the merger agreement and the consummation of the merger and the other transactions contemplated by the merger agreement, and unanimously recommended that the GenVec shareholders vote in favor of the adoption and approval of the merger agreement. In considering these facts and the other information contained in this proxy statement/prospectus, you should be aware that GenVec’s executive officers and directors may have interests in the merger that are different from, or in addition to, the interests of GenVec shareholders generally. For a detailed discussion of the special interests that GenVec’s directors and executive officers may have in the merger, see the section entitled “The Merger—Interests of GenVec’s directors and executive officers in the merger.”

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The market price of Intrexon common stock after the merger may be affected by factors different from those currently affecting the financial condition, results of operations and business of GenVec.

Upon completion of the merger, holders of GenVec common stock will become holders of Intrexon common stock. Intrexon’s business differs from that of GenVec in important respects, and, accordingly, the financial condition and operating results of the combined company and the market price of Intrexon common stock after the completion of the merger may be affected by factors different from those currently affecting the financial condition and operating results of GenVec.

The issuance of Intrexon common stock in connection with the merger could decrease the market price of Intrexon common stock.

At the completion of the merger, Intrexon expects to issue up to approximately 696,281 shares of Intrexon common stock, or approximately 0.58% of the number of shares of Intrexon common stock outstanding as of the record date, to GenVec shareholders in the merger. The issuance of the Intrexon common stock may result in fluctuations in the market price of Intrexon common stock, including a stock price decline.

The foregoing assumes that no shares of Intrexon common stock are issued to holders of CPRs. If shares of Intrexon common stock are issued to holders of CPRs, such additional issuances may result in further fluctuations in the market price of Intrexon common stock.

The shares of Intrexon common stock to be received by GenVec shareholders as a result of the merger will have different rights from the shares of GenVec common stock.

Upon completion of the merger, GenVec shareholders will become Intrexon shareholders and their rights as shareholders will be governed by Intrexon’s amended and restated articles of incorporation, Intrexon’s amended and restated bylaws, and Virginia law. Certain of the rights associated with GenVec common stock are different from, and may be viewed as more favorable than, the rights associated with Intrexon common stock. See the section entitled “Comparison of rights of shareholders of Intrexon and GenVec” for a discussion of the different rights associated with Intrexon common stock.

The issuance of additional equity securities by Intrexon in capital raising transactions or strategic transactions after completion of the merger would result in additional dilution to existing shareholders.

To the extent Intrexon raises additional capital by issuing equity securities, including in a debt financing where Intrexon issues convertible notes or notes with warrants, or issues additional equity in a strategic transaction, Intrexon’s shareholders may experience substantial dilution. Intrexon may, from time to time, issue common stock in one or more transactions at prices and in a manner it determines. If Intrexon issues common stock, existing shareholders may be materially diluted. In addition, new investors could gain rights superior to existing shareholders, such as liquidation and other preferences.

GenVec shareholders will have a reduced ownership and voting interest in Intrexon as compared with their interest in GenVec and will exercise less influence over management.

GenVec shareholders currently have the right to vote in the election of directors of GenVec and on certain other matters affecting GenVec. Based on the number of GenVec shares of common stock outstanding as of May 8, 2017, Intrexon expects to issue approximately 696,281 shares of its common stock to GenVec shareholders in the merger (assuming no shares of Intrexon common stock are issued to the holders of CPRs). The actual number of shares of Intrexon common stock to be issued in the merger will be determined at the completion of the merger based on the number of GenVec shares outstanding at the time of the consummation of the merger, subject to adjustment as described herein. Immediately after the consummation of the merger, and based on the number of shares of Intrexon common stock outstanding as of the record date, it is expected that former GenVec

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shareholders will own approximately 0.58% of the 119,565,470 shares of Intrexon common stock then outstanding. Because of this, GenVec’s shareholders will have substantially less influence on the management and policies of Intrexon than they now have with respect to the management and policies of GenVec.

If the proposed merger is not completed, GenVec will have incurred substantial costs that could adversely affect GenVec’s financial results and operations and the market price of GenVec common stock.

If the merger is not completed, the on-going business of GenVec may be adversely affected. Without having realized any of the benefits of the merger, GenVec will be subject to a number of risks, including:

GenVec may also be subject to litigation related to any failure to complete the merger. If the merger is not completed, these risks may materialize and may adversely affect GenVec’s business and financial results and the market price of GenVec common stock.

Lawsuits have been filed, and other lawsuits may be filed, against Intrexon, GenVec and members of GenVec’s board of directors challenging the merger, and an adverse ruling in any such lawsuit may delay or prevent the completion of the merger or result in an award of damages against Intrexon or GenVec.

Four putative class actions, referred to herein as the Stockholder Actions, were filed against GenVec and members of GenVec’s board of directors, referred to herein as Individual Defendants, in connection with GenVec’s proposed merger with Intrexon. The complaints in the Stockholder Actions allege that GenVec and the Individual Defendants violated Section 14(a) of the Securities Exchange Act of 1934, and Rule 14a-9 promulgated thereunder, by failing to disclose in the draft proxy statement included in the Registration Statement on Form S-4 filed by Intrexon on March 17, 2017 in connection with the merger certain information regarding alleged potential conflicts of interest, events leading up to the signing of the merger agreement with Intrexon and Merger Sub, certain financial data regarding GenVec, and certain inputs regarding Roth’s fairness opinion. The complaints in the Stockholder Actions also allege the Individual Defendants violated Section 20(a) of the Securities Exchange Act of 1934 as control persons who had the ability to prevent the Registration Statement from being false and misleading. Two of the Stockholder Actions also allege that Intrexon and Merger Sub violated Section 20(a) of the Exchange Act. The actions seek, among other things, an injunction preventing consummation of the merger with Merger Sub, an award of damages, and an award of costs and expenses, including attorneys’ fees. On April 19, 2017, the plaintiffs in two of the Stockholder Actions voluntarily dismissed their claims. On April 25, 2017, the plaintiff in one of the Stockholder Actions filed a pre-motion letter, referred to herein as the April 25 Letter, advising the court of his intention to file a motion for preliminary injunctive relief. On May 2, 2017, the parties to the Stockholder Actions entered into a Memorandum of Understanding, referred to herein as the MOU, that calls for, among other things: (1) certain additional disclosures to be included in the proxy statement mailed to GenVec stockholders in connection with the merger; (2) the withdrawal of the April 25 Letter; and (3) dismissal of the remaining Stockholder Actions immediately following the vote by GenVec stockholders on the merger. On May 4, 2017, in accordance with the MOU, the plaintiffs in the remaining Stockholder Actions advised the court of the MOU, filed stipulations seeking to stay

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those actions and withdrew the April 25 Letter. Intrexon, GenVec and the Individual Defendants believe the remaining Stockholder Actions are without merit and, if those actions are not voluntarily dismissed pursuant to the MOU, intend to vigorously defend them.

Additional lawsuits arising out of or relating to the merger agreement or the merger may be filed in the future. The results of complex legal proceedings are difficult to predict and could delay or prevent the completion of the merger. The existence of litigation relating to the merger could impact the likelihood of obtaining stockholder approval of the merger. Moreover, the pending litigation is, and any future additional litigation could be, time consuming and expensive and could divert management’s attention away from its regular business.

If the proposed merger is not completed, GenVec’s ability to continue as a stand-alone company may be uncertain.

GenVec’s ability to continue as a stand-alone company, including its ability to secure necessary funding for its operations, may face uncertainty if the merger is not completed. GenVec’s ability to execute on its operating strategy may also be affected by the failure to complete the merger. For example, potential licensees or other collaborators may be reluctant to enter into arrangements with GenVec on terms that are acceptable to it, or at all, because of any concerns regarding GenVec’s long-term stability and plans raised by entering into the merger agreement and then failing to complete the merger. Accordingly, GenVec may not be able to successfully execute its operating strategy.

In addition, if the merger is not completed and the GenVec board of directors seeks another merger or business combination, GenVec shareholders cannot be certain that GenVec will be able to find a party willing to offer equivalent or more attractive consideration than the per share merger consideration Intrexon has agreed to provide in the merger.

The integration of GenVec and other acquired businesses may present significant challenges to Intrexon.

Achieving the anticipated benefits of the merger will depend in part upon whether GenVec and Intrexon can integrate their businesses in an efficient and effective manner. The combination of two independent businesses is a complex, costly and time-consuming process. The integration of GenVec and any future businesses that Intrexon may acquire involves a number of risks, including, but not limited to:

Many of these factors are outside of the control of Intrexon and GenVec, and will be outside the control of the combined company, and any one of them could result in increased costs, decreased expected revenues and diversion of management time and energy, which could materially impact the business, financial condition and results of operations of the combined company. In addition, even if the operations of the businesses of Intrexon and GenVec are integrated successfully, the full benefits of the merger may not be realized, including, among others, the synergies, cost savings or sales or growth opportunities that are expected. These benefits may not be

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achieved within the anticipated time frame, or at all. Further, additional unanticipated costs may be incurred in the integration of the businesses of Intrexon and GenVec. All of these factors could cause dilution to the earnings per share of the combined company, decrease or delay the expected accretive effect of the merger, and negatively impact the price of the combined company ordinary shares. As a result, it cannot be assured that the combination of Intrexon and GenVec will result in the full realization of the benefits anticipated from the transaction within the anticipated time frames or at all.

Risks related to Intrexon and its business

You should read and consider the risk factors specific to Intrexon’s business that will also affect the combined company after the merger. These risks are described in Part I, Item 1A of Intrexon’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016, Part II, Item 1A of Intrexon’s Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2017, and in other documents that are incorporated by reference into this proxy statement/prospectus. See the section entitled “Where you can find more information” for the location of information incorporated by reference in this proxy statement/prospectus.

Risks related to GenVec and its business

GenVec has a history of losses and anticipates future losses.

GenVec has incurred net losses in each year since its inception in December 1992, including a net loss of $5.8 million for the year ended December 31, 2016. As of March 31, 2017, GenVec had an accumulated deficit of approximately $294.9 million. GenVec is unsure if or when it will become profitable. The size of GenVec’s net losses will depend on its revenues and its expenses.

GenVec has derived its revenues primarily from payments from collaborations with corporations and government entities and expects to do so for the foreseeable future. It may be years, if ever, before GenVec recognizes revenue from product candidate sales or royalties. While GenVec has taken efforts to control costs throughout 2016 and into 2017, a large portion of its expenses are fixed, including expenses related to facilities, equipment and personnel, and GenVec’s ability to continue to meaningfully reduce costs is limited. In addition, GenVec expects to continue to spend significant amounts to fund research and development to advance its programs and to enhance its core technologies. As a result of its operating expenses, GenVec will need to generate significant additional revenue to achieve profitability. Even if GenVec does achieve profitability, it may not be sustainable.

GenVec is a biopharmaceutical company deploying unproven technologies, and it may never be able to develop, obtain regulatory approval of, or market any of its product candidates.

Gene-based products are new and rapidly evolving medical approaches, which have not been shown to be effective on a widespread basis. Only a limited number of gene-based products have been successfully developed and commercialized to date. In addition, no gene therapy product has received regulatory approval in the U.S. None of GenVec’s product candidates has been approved for sale in the U.S. or elsewhere. Gene-based products may be susceptible to various risks, including undesirable and unintended side effects from genes or the delivery systems, unintended immune responses, inadequate therapeutic efficacy, or other characteristics that may prevent or limit their approval or commercial use. Successful products require significant development and investment, including a lengthy and uncertain period of testing to show their safety and effectiveness before their regulatory approval or commercialization. Other than GenVec’s limited conditional approval with respect to its foot-and-mouth disease (which we refer to as FMD) vaccine, GenVec has not proven its ability to develop, obtain regulatory approval of, or commercialize gene-based medicines or vaccines.

If GenVec or its collaborators fail to adequately show the safety and efficacy of GenVec’s product candidates, GenVec will not be able to obtain FDA approval of its product candidates.

GenVec faces the risk of failure involved in developing therapies based on new technologies and the difficulties generally associated with drug development. CGF166 is the only product candidate that GenVec and its

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collaborators currently have in clinical trials. Novartis initiated dosing in a Phase 1/2 clinical trial of CGF166 in October 2014. On January 8, 2016, GenVec was notified by Novartis that enrollment in the clinical trial had been paused, based on a review of data by the trial’s Data Safety Monitoring Board, referred to herein as its DSMB, in accordance with criteria in the trial protocol, and the FDA placed the clinical trial on hold. The FDA lifted the clinical hold on July 25, 2016 and the Phase 1/2 clinical trial of CGF166 is currently ongoing. In February 2017, GenVec was notified that the first patient in the fourth cohort of the trial had been dosed.

Significant additional research and animal testing, referred to as preclinical testing, will need to be conducted before any of GenVec’s other product candidates currently under active development can advance to clinical trials. It may take GenVec many years to complete preclinical testing or trials, and GenVec expects that doing so will be dependent on its ability to enter into collaborations. Drug development is an uncertain scientific and medical endeavor, and failure could occur at any stage of development. Acceptable results in early testing or trials might not be repeated later. Not all products in preclinical testing or early stage clinical trials will become approved products, and historically there is a high rate of attrition for product candidates in preclinical and clinical trials due to scientific feasibility, safety, efficacy, changing standards of medical care and other variables. Before an application can be filed with the FDA for product approval, GenVec or its collaborators must show that a particular product candidate is safe and effective. Even with respect to product candidates that advance to clinical trials, GenVec or its collaborators must demonstrate the safety and efficacy of those product candidates before FDA approval can be secured. The failure to adequately show the safety and effectiveness of GenVec’s product candidates would prevent FDA approval of its products. Any one of GenVec’s product candidates could fail at any time, as clinical development of drug candidates presents numerous unpredictable and significant risks and is very uncertain at all times prior to regulatory approval by the FDA or health authorities in other major markets.

Because regulatory approval must be obtained to market GenVec’s products, GenVec cannot predict whether or when its products will be commercialized; failure to comply with applicable regulations can also harm its business and operations.

Biologic products are subject to stringent regulation by a wide range of governmental authorities. GenVec cannot predict whether GenVec or its collaborators will obtain regulatory approval for any of GenVec’s products. No one can market a biologic product in the U.S. until it has completed rigorous preclinical testing, clinical trials, and an extensive regulatory approval process implemented by the FDA. To date, the FDA has not approved a gene therapy product for sale in the U.S. Satisfaction of regulatory requirements typically takes many years, is dependent upon the type, complexity, and novelty of the product, and requires the expenditure of substantial resources. Of particular significance are the requirements covering research and development, testing, manufacturing, quality control, labeling, and promotion of drugs for human use.

Before commencing clinical trials, GenVec or its collaborators must submit an investigatory new drug application, which we refer to as an IND, to the FDA and wait for the IND to become effective 30 days following its receipt by the FDA. Even after an IND becomes effective, however, a clinical trial is subject to continuing oversight by an Institutional Review Board, referred to herein as an IRB, and the FDA, and in some cases by a DSMB, or a Data Monitoring Committee, referred to herein as a DMC.

Clinical trials are also subject to:

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Delays or rejections in the regulatory approval process may be encountered because of additional government regulation from future legislation or administrative action or changes in FDA policy during the period of product development, clinical trials, or FDA regulatory review.

Failure to comply with applicable FDA or other regulatory requirements may result in criminal prosecution, civil penalties, recall or seizure of products, total or partial suspension of production, or injunction, as well as other regulatory action against GenVec’s product candidates or GenVec. If regulatory approval of a product is granted, this approval will be limited to those disease indications for which the product has been shown through clinical trials to be safe and effective. Even if approved, a product may not be approved for the indications that are necessary or desirable for successful commercialization, or the FDA may impose restrictions on distribution of the product that may materially impact GenVec’s operations. The FDA also strictly regulates promotion and labeling after approval. Outside the U.S., the ability to market a product is also contingent upon receiving clearances from the appropriate regulatory authorities. This non-U.S. regulatory approval process includes risks similar to those associated with FDA clearance described above and is subject to the independent judgments, policies, priorities and decisions of the applicable regulatory authorities, which may differ from those of the FDA.

GenVec or its collaborators may experience delays in conducting GenVec’s clinical trials.

Clinical trials may be delayed or prematurely terminated by many factors, including: (i) limited number of, and competition for, suitable patients for the particular clinical trial; (ii) slower than expected rate of patient recruitment and enrollment; (iii) failure of patients to complete the trial; (iv) inability to obtain sufficient quantities of acceptable materials for use in clinical trials; (v) delay or failure in reaching agreement on contract terms with prospective study sites or other third-party vendors who are supporting GenVec’s clinical trials; (vi) inability to reach agreement with the FDA on a trial design that GenVec is able to execute; (vii) difficulty in adequately following up with patients after treatment; and (viii) changes in laws, regulations, regulatory policy or clinical practices. GenVec’s ability or the ability of its collaborators to enroll appropriate patients for any clinical trials for GenVec’s product candidates also may be adversely affected by trials being conducted by GenVec’s competitors for similar disease indications. The failure of any clinical trials to meet applicable regulatory standards, or the standards of the relevant reviewing bodies could cause such trials to be delayed, suspended or terminated, which could further delay the development of any of GenVec’s product candidates. Any such delays increase GenVec’s product development costs, with the possibility that GenVec could be required to raise additional funds. Delays in one clinical trial also can adversely affect GenVec’s ability and the ability of its collaborators to launch clinical trials for similar or different indications. Consequently, if such delays are significant they could negatively affect GenVec’s financial results and the commercial prospects for its products.

Additionally, clinical trials may be suspended or terminated at any time by the FDA, an IRB, a DSMB or DMC, other regulatory authorities, or by GenVec for a variety of reasons, including safety. In January 2016, Novartis paused enrollment in the clinical trial of CGF166, based on a review of data by the trial’s DSMB in accordance with criteria in the trial protocol, and the FDA placed the clinical trial on hold. The FDA lifted the clinical hold on July 25, 2016, and the Phase 1/2 clinical trial of CGF166 is currently ongoing. In February 2017, GenVec was notified that the first patient in the fourth cohort of the trial had been dosed. Any failure or significant delay in completing clinical trials for GenVec’s product candidates could harm its financial results and commercial prospects for its product candidates.

Any clinical trial may fail to produce results satisfactory to the FDA. Preclinical and clinical data can be interpreted in different ways, and the FDA may not agree with GenVec’s interpretations, which could delay, limit or prevent regulatory approval. Negative or inconclusive results or adverse medical events during a clinical trial could cause a trial to be delayed or repeated or a program to be terminated.

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GenVec does not currently have any late stage clinical trials in its therapeutic product or vaccine development programs and, therefore, GenVec does not have any near-term prospects of generating revenues from the commercial sale of its therapeutic or vaccine products.

GenVec does not currently have any therapeutic products or vaccines in late stage clinical programs, and the one product of GenVec’s that has received some approval is its FMD vaccine, for which a conditional license was issued that is applicable in certain emergency or similar situations. Accordingly, GenVec does not have any near-term prospects of generating revenues from the commercial sale of its product candidates in its therapeutic product or vaccine programs. In October 2014 Novartis initiated dosing in a Phase 1/2 clinical trial of CGF166. In January 2016, Novartis paused enrollment in the clinical trial, and the FDA placed the clinical trial on hold. The FDA lifted the clinical hold on July 25, 2016. The Phase 1/2 clinical trial of CGF166 is currently ongoing. However, there can be no assurance that CGF166 will successfully complete that trial, much less enter or successfully complete any other clinical trial. There also can be no assurance that any of GenVec’s other therapeutic products or its vaccines will enter or successfully complete the clinical trials required for commercialization.

GenVec does not know if its strategy will be successful.

GenVec’s operating strategy focuses on working with leading companies and organizations such as Novartis and the U.S. government to leverage GenVec’s proprietary gene-delivery technologies to address the prevention and treatment of significant health concerns. This strategy includes working with Novartis to facilitate the development of first-in-class products for the treatment of hearing and balance disorders, developing a sustainable revenue base by licensing rights to GenVec’s proprietary vector and cell line technologies to additional companies and organizations, licensing its preclinical vaccine candidates for the prevention of respiratory syncytial virus, which we refer to as RSV, and the treatment of herpes simplex virus 2, which we refer to as HSV-2, infection, and minimizing its cash burn by operating its business in a cost-efficient manner. This operating strategy may not be successful, and is largely dependent on the success of GenVec’s collaboration agreement with Novartis, of which there can be no assurance, and GenVec’s ability to enter into additional collaborations, which GenVec has only been able to do to a limited extent.

A central aspect of GenVec’s business strategy is to enter into collaborations with other companies to develop, obtain regulatory approval of, and commercialize its potential products, and if GenVec is unable to find collaborators or sustain existing relationships, GenVec may not be able to generate revenue and advance its products.

A central aspect of GenVec’s business strategy is to enter into collaborations to support the development of its products. GenVec’s lead program, in the field of regenerative medicine and licensed to Novartis, is for the development of novel treatments for hearing loss and balance disorders. In addition to this program, GenVec intends to license rights to its proprietary vector and cell line technologies to additional companies and organizations and license its preclinical vaccine candidates for the prevention of RSV and the treatment of HSV-2 infection. There can be no assurance that GenVec will be able to enter into licensing and other collaboration agreements on terms that are acceptable to GenVec, or at all. If GenVec is not able to enter into and sustain license or other collaboration agreements, it would not be able to develop a sustainable revenue base, and it would need to raise additional funds for the development and commercialization of GenVec’s product candidates and technologies and develop additional capabilities in testing, manufacturing, marketing and sales, among other areas. If GenVec is not able to enter into successful collaborations or obtain additional funds through other means, it would have to delay, curtail or abandon the development and commercialization of certain product candidates and technologies.

GenVec intends to continue to seek support for its government funded contracts and collaborations for the development of new vaccines, but GenVec’s existing agreements are subject to termination and uncertain future funding and there is no certainty that GenVec will be able to enter into new agreements.

In addition to corporate collaborations, GenVec has historically entered into agreements with U.S. government agencies, such as the National Institute of Allergy and Infectious Diseases of the National Institutes of Health,

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the U.S. Department of Homeland Security, the U.S. Department of Agriculture, herein referred to as USDA, and the U.S. Naval Medical Research Center to support GenVec’s vaccine research. These and similar agreements have historically accounted for a substantial portion of GenVec’s revenues, and GenVec intends to continue entering into these agreements in the future. GenVec’s business strategy is partially dependent on collaboration agreements with U.S. government agencies and on the ability of these government agencies to perform under these agreements, which performance depends on adequate continued funding of the agencies and their programs.

GenVec has no control over the resources and funding government agencies may devote to any collaboration agreements with GenVec, which may be subject to annual renewal and which generally may be terminated by the government agencies at any time. Any significant reductions in the funding of U.S. government agencies or in the funding areas targeted by GenVec’s business could materially and adversely affect its business, results of operations, and financial condition. If GenVec was to fail to satisfy its contractual obligations to deliver in the manner required by a collaboration agreement with a U.S. government agency, the applicable Federal Acquisition Regulations allow the agency to cancel the agreement in whole or in part, and GenVec may be required to perform corrective actions, including but not limited to delivering to the government any uncompleted or partially completed work. The performance of these corrective actions could have a material adverse impact on GenVec’s financial results in the period or periods affected. Government agencies may fail to perform their responsibilities under these agreements, which could materially impact GenVec’s financial results.

In addition, GenVec’s contract-related costs and fees, including allocated indirect costs, are subject to audits and adjustments by negotiation between GenVec and the U.S. government. As part of the audit process, the government audit agency verifies that all charges made by a contractor against a contract are legitimate and appropriate. Audits may result in recalculation of contract revenues and non-reimbursement of some contract costs and fees. Any audits of GenVec’s contract-related costs and fees could result in material adjustments to its revenues. In addition, U.S. government contracts are conditioned upon the continuing availability of Congressional appropriations. Congress usually appropriates funds on a fiscal year basis even though contract performance may take several years. Consequently, at the outset of a major program, the contract is usually incrementally funded and additional funds are normally committed to the contract by the procuring agency as appropriations are made by Congress for future fiscal years. Any failure of such agencies to continue to fund such contracts could have a material adverse effect on GenVec’s business, results of operations, and financial condition.  

GenVec applies for and has received funding from government agencies under Small Business Technology Transfer and Small Business Innovation Research grants. Eligibility of public companies to receive such grants is based on size and ownership criteria that are under review by the Small Business Administration. As a result, its eligibility may change in the future and additional funding from this source may not be available.

GenVec depends, and anticipates depending further, on corporate collaborators for the development of GenVec’s product candidates.

When GenVec signs a collaboration agreement, license agreement or similar agreement with a collaborator to develop a product candidate, it will generally expect the collaborator to further the development of the product candidate, which could include the design and conduct of clinical trials, the preparation and filing of documents necessary to obtain regulatory approval, and the manufacturing, sale, marketing and other commercialization of the product if it obtains regulatory approval. GenVec may also grant the collaborator certain rights. For example, under the terms of the NVS License Agreement, GenVec granted Novartis certain exclusive, worldwide rights in specified intellectual property related to GenVec’s atonal gene program and atonal adenovectors, as well as non-exclusive, world-wide rights to certain other intellectual property related to GenVec’s hearing loss and balance disorders program and its adenovector platform related to the atonal gene. Novartis has the right to

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develop and commercialize any products related to the licensed intellectual property. GenVec’s dependence on a corporate collaborator, such as Novartis, subjects GenVec to a number of risks, including that:

Given these risks, the success of GenVec’s current and future collaborations is highly unpredictable and can have a substantial negative or positive impact on its business. If GenVec’s collaborations fail, its product development or commercialization of product candidates could be delayed or cancelled, which would negatively impact GenVec’s business, results of operations and financial condition.

Collaborations might produce conflicts that could delay or prevent the development or commercialization of GenVec’s potential product candidates and negatively impact its business and financial condition.

An important part of GenVec’s strategy involves conducting multiple product development programs. GenVec may pursue opportunities in fields that conflict with those of its collaborators. In addition, disagreements with GenVec’s collaborators could develop over rights to its intellectual property or rights to technology developed with its collaborators. The resolution of such conflicts and disagreements may affect ownership of intellectual property to which GenVec believes GenVec is entitled. In addition, any disagreement or conflict with GenVec’s collaborators could reduce GenVec’s ability to obtain future collaboration agreements and negatively impact GenVec’s relationship with existing collaborators. Such a conflict or disagreement could also lead to delays or termination of collaborative research, development, regulatory approval, or commercialization of various products or could require or result in litigation or arbitration, which would be time consuming, expensive, lead to a diversion of management attention and resources and could have a significant negative impact on GenVec’s business, financial condition, and results of operations.

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GenVec’s collaboration agreements may prohibit GenVec from conducting research in areas that may compete with GenVec’s collaboration products, while its collaborators may not be limited to the same extent. This could negatively affect GenVec’s ability to develop products and, ultimately, prevent GenVec from achieving a continuing source of revenues.

GenVec anticipates some of its corporate or academic collaborators will be conducting multiple product development efforts within each disease area that is the subject of their collaborations with GenVec. In certain circumstances GenVec has agreed not to conduct independently, or with any third party, certain research and development activities that are competitive with the research and development activities conducted under GenVec’s collaborations. Therefore, GenVec’s collaborations may limit the areas of research and development GenVec may pursue alone or with others. Some of GenVec’s collaborators, however, may develop, either alone or with others, products in related fields that are competitive with the products or potential products that are the subject of their collaborations with GenVec. In addition, competing products, either developed by the collaborators or to which the collaborators have rights, may result in their withdrawing support for GenVec’s product candidates.

Agreements with government agencies may lead to claims against GenVec under the Federal False Claims Act, and these claims could result in substantial fines and other penalties.

The biopharmaceutical industry is, and in recent years has been, under heightened scrutiny as the subject of government investigations and enforcement actions. GenVec’s agreements with U.S. government agencies or any arrangement that implicates the payment of government funds may be subject to substantial financial penalties under the Federal Civil Monetary Penalties Act and the federal False Claims Act. Under the False Claims Act’s “whistleblower” provisions, private enforcement of fraud claims against businesses on behalf of the U.S. government has increased due in part to amendments to the False Claims Act that encourage private individuals to sue on behalf of the government. These whistleblower suits, known as qui tam actions, may be filed by private individuals, including present and former employees. The federal False Claims Act provides for treble damages and civil penalties of up to $11,000 per false claim. If GenVec’s operations are found to be in violation of any of these laws, or any other governmental regulations that apply to GenVec, GenVec may be subject to penalties, damages, fines, exclusion from federal healthcare programs like Medicare and Medicaid, and the curtailment or restructuring of GenVec’s operations. Any penalties, damages, fines, exclusions, curtailment or restructuring of GenVec’s operations could adversely affect its ability to operate its business and its financial results.

If successful large-scale manufacturing of gene-based medicines is not possible, GenVec or its collaborators may be unable to manufacture enough of GenVec’s product candidates to achieve regulatory approval or market its products.

Few companies to date have demonstrated successful large-scale manufacturing of gene-based medicines, including those that have had significantly more resources than GenVec does and it is anticipated that significant challenges will be faced in the scale-up of GenVec’s manufacturing process for commercial production. There are a limited number of contract manufacturers qualified to perform large-scale manufacturing of gene-based medicines. GenVec or its collaborators may be unable to manufacture commercial-scale quantities of gene-base medicines or receive appropriate government approvals on a timely basis or at all. Failure to successfully manufacture or obtain appropriate government approvals on a timely basis or at all would prevent GenVec from achieving its business objectives.

If regulatory approvals are not obtained for a manufacturing facility for GenVec’s products, GenVec may experience delays, be unable to meet demand, and may lose potential revenues.

Completion of clinical trials for and commercialization of GenVec’s product candidates require access to, or development of, facilities to manufacture a sufficient supply of its product candidates. GenVec has limited experience manufacturing any of its gene-based products in the volumes that will be necessary to support large-

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scale clinical trials or commercial sales, and GenVec expects that it will rely on its collaborators for manufacturing capabilities. Before GenVec or its collaborators can begin commercial manufacturing of any of its product candidates, GenVec or its collaborators must obtain regulatory approval of the manufacturing facility and process. Manufacturing of GenVec’s proposed products must comply with cGMP requirements and similar non-U.S. regulatory requirements. The cGMP requirements govern, among other things, personnel, buildings and facilities, equipment, control of components and drug product containers and closures, production and process controls, packaging and labeling controls, holding and distribution, laboratory controls and records and reports. Among other things, complying with cGMP and comparable non-U.S. regulatory requirements will require GenVec to expend time, money and effort in production, record keeping, and quality control to ensure the product meets applicable specifications and other requirements. GenVec or its collaborators must also pass a preapproval inspection before FDA approval. Significant capital will likely need to be expended on the development of manufacturing capacity for a product candidate even before GenVec knows if the FDA will approve the product for commercialization. Furthermore, if GenVec or its collaborators materially fail to comply with these requirements, its product candidates likely would not be approved. If GenVec or its collaborators fail to comply with these requirements after approval, GenVec would be subject to possible regulatory action (including warning letters, restrictions on the product, product recalls, suspension or withdrawal of approval, seizures, injunctions, civil fines, and criminal sanctions), and GenVec may be limited in the jurisdictions in which GenVec is permitted to sell its products. The FDA and non-U.S. regulatory authorities generally have the authority to perform unannounced periodic inspections of manufacturing facilities to ensure compliance with cGMP and non-U.S. regulatory requirements.

GenVec relies on a limited number of suppliers for some of its manufacturing materials. Any problems experienced by any of these suppliers could negatively impact GenVec’s operations.

GenVec relies on third-party suppliers and vendors for some of the materials used in the manufacture of GenVec’s product candidates. Some of these materials are available from only one supplier or vendor. For supply of early clinical trial materials, GenVec relies on one supplier, Thermo Fisher Scientific Corporation, for its cell culture medium and another supplier, Lonza Walkersville, Inc., for custom buffers. The cell culture medium is used to grow the cells within which GenVec’s product candidates are produced. GenVec does not currently have supply agreements with any of its suppliers. Any significant problem experienced by one of GenVec’s suppliers could result in a delay or interruption in the supply of materials to GenVec until such supplier resolves the problem or an alternative source of supply is located. GenVec has limited experience with alternative sources of raw materials. Any delay or interruption would likely lead to a delay or interruption of manufacturing operations, which could negatively affect GenVec’s operations.

GenVec faces substantial competition from other companies and research institutions that are developing products to treat the same diseases that GenVec’s product candidates target, and GenVec may not be able to compete successfully.

GenVec competes with pharmaceutical and biotechnology companies pursuing other forms of treatment for the health concerns GenVec’s product candidates target. GenVec may also face competition from companies that may develop competing technology internally or acquire it from the government, universities or other research institutions. As these companies develop their technologies, they may develop proprietary positions, which may prevent or limit GenVec’s product commercialization efforts.

Some of GenVec’s competitors are established companies with greater financial and other resources than GenVec’s. GenVec’s competitors may succeed in:

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While GenVec seeks to expand its technological capabilities to remain competitive, research and development by others may render its technology or product candidates obsolete or noncompetitive or result in treatments or cures superior to any therapy developed by GenVec.

In addition, GenVec’s products, if approved, may subsequently face competition from biosimilar products that are approved via an abbreviated process on the basis of a showing that the product is highly similar to its approved product. The Biologics Price Competition and Innovation Act provides periods of exclusivity during which abbreviated applications may not be submitted to, or approved by, the FDA, but the statute then allows approval by an abbreviated pathway and, if certain standards are met, a finding by the FDA that the biosimilar product is interchangeable with the reference product. A similar abbreviated approval process for biosimilars (but without the possibility of an interchangeability determination) is available in Europe. If competitors are able to obtain marketing approval for biosimilars under an abbreviated regulatory approval process in the U.S. or Europe, GenVec’s products may become subject to additional competition with the attendant pricing pressure. GenVec also could face or be forced to bring litigation with respect to the validity or scope of patents relating to GenVec’s products.

If GenVec is unable to adequately protect its intellectual property rights, its competitors may be able to take advantage of its research and development efforts to compete with GenVec.

GenVec’s commercial success will depend, in part, on obtaining patent protection for GenVec’s products and other technologies and successfully defending these patents against third party challenges. GenVec’s patent position, like that of other biotechnology firms, is highly uncertain and involves complex legal and factual questions. The laws, rules, and regulations affecting biotechnology patent protection in the U.S. and other countries are uncertain and are currently undergoing review and revision. Changes in, or different interpretations of, patent laws in the U.S. and other countries might allow others to use GenVec’s discoveries or to develop and commercialize its products without any compensation to GenVec.

GenVec’s ability to develop and protect a proprietary position based on biotechnological innovations and technologies involving genes and gene delivery systems, methods of use, production, formulations, and the like is particularly uncertain. The U.S. Patent and Trademark Office, as well as patent offices in other countries, have often required that patent applications concerning biotechnology-related inventions be limited or narrowed substantially. GenVec’s disclosures in its patent applications may not be sufficient to meet the statutory requirements for patentability in all cases. In addition, other companies or institutions possess issued patents and have filed and will file patent applications that cover or attempt to cover genes, vectors, cell lines, and methods of making and using gene therapy products that are the same as or similar to the subject matter of GenVec’s patent applications. For example, although GenVec has pending patent applications pertaining to particular adenovectors that cannot reproduce themselves and adenovectors modified to alter cell binding characteristics, GenVec is aware of issued patents and pending patent applications of other companies and institutions relating to the same subject matter. Patents and patent applications of third parties may have priority over GenVec’s issued patents and its pending or yet to be filed patent applications. Proceedings before the U.S. Patent and Trademark Office and other patent offices to determine who properly lays claim to inventions are costly and time consuming, and GenVec may not win in any such proceedings.

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The issued patents GenVec already has or may obtain in the future may not provide commercially meaningful protection against competitors. Other companies or institutions may challenge GenVec’s or its collaborators’ patents in the U.S. and in other countries. In the event a company, institution or researcher infringes upon GenVec’s or its collaborators’ patent rights, enforcing these rights may be difficult, expensive and time consuming, with no guarantee that GenVec’s or its collaborators’ patent rights will be upheld. Others may be able to design around these patents or develop unique products providing effects similar to GenVec’s products. In addition, GenVec’s competitors may legally challenge GenVec’s patents, and they may be considered invalid. For example, GenVec is also aware of issued patents and pending patent applications of third parties relating to aspects of production, purification, quality assessment, and formulation technology. It could be alleged that GenVec’s production, purification, quality assessment, and formulation technology conflict with such existing or future patents.

Various components used in developing gene therapy products, such as particular genes, vectors, promoters, cell lines, and construction methods, used by others and by GenVec, are available to the public. As a result, GenVec is unable to obtain patent protection with respect to such components, and third parties can freely use such components. Third parties may develop products using such components that compete with GenVec’s potential products. Also, with respect to some of GenVec’s patentable inventions, GenVec or its collaborators have decided not to pursue patent protection outside the U.S. Accordingly, GenVec’s competitors could develop, and receive non-U.S. patent protection for, gene therapies or technologies for which GenVec or its collaborators have or are seeking U.S. patent protection. GenVec’s competitors may be free to use these gene therapies or technologies outside the U.S. in the absence of patent protection.

GenVec also relies to a limited extent on trade secrets to protect its technology. However, trade secrets are difficult to protect. While GenVec has entered into confidentiality agreements with employees and collaborators, it may not be able to prevent the disclosure or use of GenVec’s trade secrets. In addition, other companies or institutions may independently develop substantially equivalent information and techniques.

If GenVec’s technologies and potential products conflict with intellectual property rights of competitors, universities, or others, then GenVec may be prevented from licensing those technologies, developing those product candidates or both.

Other companies and institutions have issued patents and have filed or will file patent applications that may issue into patents that cover or attempt to cover genes, vectors, cell lines, and methods of making and using gene and gene-based therapy products used in or similar to GenVec’s product candidates and technologies. GenVec also is aware of other issued patents and pending patent applications that relate to various aspects of GenVec’s manufacture of its product candidates and systems, and it could be alleged that GenVec’s manufacture of these product candidates or licensure of those technologies conflicts with these patents. GenVec has not conducted freedom-to-use patent searches on all aspects of GenVec’s technologies, product candidates or potential product candidates, and GenVec may be unaware of relevant patents and patent applications of third parties. In addition, the freedom-to-use patent searches that have been conducted may not have identified all relevant issued patents or pending patent applications that could issue into patents, particularly in view of the characterizations of the subject matter of issued patents and pending patent applications, as well as the fact that pending patent applications can be maintained in secrecy for a period of time and, in some circumstances, until issuance as patents.

An issued patent gives rise to a rebuttable presumption of validity under U.S. law and under the laws of some other countries. The holder of a patent to which GenVec or its collaborators do not hold a license could bring legal actions against GenVec’s collaborators or GenVec for damages or to stop GenVec or its collaborators from using the affected technology, which could limit or preclude its ability to license its technologies or to develop and commercialize its product candidates. If any of GenVec’s potential products are found to infringe a patent of a competitor or third party, GenVec or its collaborators may be required to pay damages and to either obtain a license in order to continue to develop and commercialize the potential products or, at the discretion of the

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competitor or third party, to stop development and commercialization of the potential products. Similarly, if any of GenVec’s out-licensed technologies are found to infringe a patent of a competitor or third party, GenVec or its collaborators may be required to pay damages and to either obtain a license in order to continue to utilize the technologies or, at the discretion of the competitor or third party, to stop utilizing the technologies. Since GenVec has concentrated its resources on licensing certain of its technologies and developing only a limited number of products, the inability to license one of its technologies or to market one of its products would disproportionately affect GenVec as opposed to a competing company with many products in development.

GenVec believes there will be significant litigation in its industry regarding intellectual property rights. Many of GenVec’s competitors have expended and are continuing to expend significant amounts of time, money and management resources on intellectual property litigation. If GenVec becomes involved in litigation, it could consume a substantial portion of GenVec’s resources and could adversely affect its business, financial condition and results of operations, even if GenVec ultimately is successful in such litigation.

If GenVec loses its rights to use intellectual property it licenses from others, or those rights are not enforceable, then GenVec’s ability to develop and commercialize its product candidates will be harmed.

GenVec relies, in part, on licenses to use some technologies material to its business. For example, to create GenVec’s product candidates GenVec combines its adenovectors with genes intended to produce therapeutic proteins. In most instances GenVec does not own the patents or patent applications that cover these genes and certain methods of use thereof which underlie these licenses. For these genes, GenVec does not control the enforcement of the patents. GenVec relies upon its licensors to properly prosecute and file those patent applications and defend and enforce any issued patents.

While many of the licenses under which GenVec has rights provide it with exclusive rights in specified fields, the scope of GenVec’s rights under these and other licenses may be subject to dispute by its licensors or third parties. In addition, GenVec’s rights to use these technologies and practice the inventions claimed in the licensed patents and patent applications are subject to GenVec’s licensors abiding by the terms of those licenses and not terminating them. Any of GenVec’s licenses may be terminated by the licensor if GenVec is in breach of a term or condition of the license agreement or in certain other circumstances. In addition, some of GenVec’s licenses are contingent upon its achievement of specific development milestones.

Legal proceedings to obtain, enforce, and defend patents, and litigation of third-party claims of intellectual property infringement could require GenVec to spend money and could impair GenVec’s operations.

GenVec’s success will depend, in part, on GenVec’s ability to obtain patent protection for its products and processes, both in the U.S. and in other countries. The patent positions of biotechnology and pharmaceutical companies, however, can be highly uncertain and can involve complex legal and factual questions. Therefore, it is difficult to predict the breadth of claims allowed in the biotechnology and pharmaceutical fields.

Protecting intellectual property rights can be expensive and time consuming. Litigation may be necessary to enforce patents issued to GenVec or to determine the scope and validity of third party proprietary rights. Moreover, if a competitor were to file a patent application claiming technology also invented by GenVec, GenVec would have to participate in an interference proceeding before the U.S. Patent and Trademark Office to determine the priority of invention. GenVec may be drawn into interferences with third parties or may have to provoke interferences by itself to challenge third-party patent rights to allow GenVec or its licensees to commercialize products based on GenVec’s technologies. Litigation could result in substantial costs and diversion of management efforts regardless of the results of the litigation. An unfavorable result in litigation could subject GenVec to significant liabilities to third parties, require disputed rights to be licensed, or require GenVec to cease using some technologies.

GenVec’s products and processes may infringe, or be found to infringe, patents not owned or controlled by GenVec. Patents held by others may require GenVec to alter its products or processes, obtain licenses or stop

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activities. If relevant claims of third-party patents are upheld as valid and enforceable, GenVec could be prevented from practicing the subject matter claimed in the patent. In addition, GenVec may be required to obtain licenses, redesign its products or processes to avoid infringement or pay money damages. As a result, GenVec’s business may suffer if GenVec is not able to obtain licenses at all or on commercially reasonable terms to GenVec or GenVec is required to redesign its products or processes to avoid infringement.

GenVec is exposed to potential product liability claims.

GenVec’s business exposes GenVec to potential product liability risks inherent in the clinical testing and manufacturing and marketing of pharmaceutical products, and GenVec may not be able to avoid significant product liability exposure. A product liability claim or recall could be detrimental to GenVec’s business. Although GenVec currently maintains product liability and clinical trial insurance, GenVec’s present product liability and clinical trial insurance may be inadequate. Any successful product liability claim may prevent GenVec from obtaining adequate product liability and clinical trial insurance in the future on commercially desirable or reasonable terms. In addition, product liability and clinical trial coverage may cease to be available in sufficient amounts or at an acceptable cost. An inability to obtain sufficient insurance coverage at an acceptable cost or otherwise to protect against potential product liability claims could prevent or inhibit the commercialization of GenVec’s products. A successful product liability claim could have a material adverse effect on GenVec’s reputation, business, financial condition and results of operations.

Adverse events in the field of gene therapy may negatively affect regulatory approval or public perception of GenVec’s products or product candidates.

Most of GenVec’s product candidates under development could be broadly described as recombinant DNA therapies. A number of clinical trials are being conducted by other biotechnology and pharmaceutical companies involving related therapies, including compounds similar to or competitive with, GenVec’s product candidates. The announcement of adverse results from these clinical trials, such as serious adverse events or unexpected side effects attributable to the treatment, or any response by the FDA or other similar regulatory authority to such clinical trials, may impede the timing of GenVec’s clinical trials, delay or prevent GenVec from obtaining regulatory approval, impede GenVec’s ability to secure additional funding, or negatively influence public perception of its product candidates. As a result, these conditions could harm GenVec’s business and results of operations.

The commercial success of GenVec’s product candidates will depend, in part, on public acceptance of the use of gene therapies for the prevention or treatment of significant health concerns. Public attitudes may be influenced by claims that gene therapy is unsafe, and gene therapy may not gain the acceptance of the public or the medical community. Negative public reaction to gene therapy could result in greater government regulation and stricter clinical trial oversight and commercial product labeling requirements of gene therapy products and could cause a decrease in the demand for any products GenVec may develop.

GenVec’s product candidates involve new technologies and therapeutic approaches in the field of gene therapy, which is a new and evolving field. As discussed above, no gene therapy product has received regulatory approval in the U.S., and adverse events in this field may negatively affect public perception of GenVec’s product candidates. Even if GenVec’s product candidates attain regulatory approval, its success will depend upon the medical community, patients, and third-party payers accepting gene therapy products in general, and its product candidates in particular, as medically useful, cost-effective, and safe. In particular, GenVec’s success will depend upon whether physicians who specialize in the diseases GenVec’s product candidates target decide to prescribe treatments that involve the use of GenVec’s product candidates in lieu of, or in addition to, existing treatments they are already familiar with and for which greater clinical data may be available. Even if the clinical safety and efficacy of GenVec’s product candidates is established, physicians may elect not to recommend its products for a variety of reasons, including the reimbursement policies of government and third-party payers. Furthermore, third-party payers, such as health insurance plans, may be reluctant to authorize and pay for new forms of treatment they may deem expensive and less proven than existing treatments. Even if gene therapy products, and

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GenVec’s product candidates in particular, are accepted by the medical community and third-party payers, the public in general, or patients in particular, may be uncomfortable with new therapies, including GenVec’s product candidates, and it could take substantial time for them to accept gene therapy products as a viable treatment alternative, if ever. If gene therapy and GenVec’s product candidates do not gain widespread acceptance, GenVec may be unable to generate significant revenues, if any, which would adversely affect its results of operations. In addition, even if GenVec’s product candidates achieve market acceptance, GenVec may not be able to maintain that market acceptance over time if new products or technologies are introduced that are more favorably received than GenVec’s product candidates or that render them obsolete.

GenVec uses hazardous biological materials in GenVec’s business; any liability or disputes relating to improper handling, storage or disposal of these materials could be time consuming and costly.

GenVec’s research and development processes involve the use of hazardous biological materials. Such materials include human and animal cell lines and viruses, such as adenoviruses and animals infected with human viruses. Some of the biological material may be novel, including viruses with novel properties. GenVec cannot eliminate the risk of accidental contamination or discharge or injury from these materials. Federal, state and local laws and regulations govern the use, manufacture, storage, handling and disposal of these materials. GenVec could be subject to civil damages in the event of an improper or unauthorized release of, or exposure of individuals to, these hazardous materials. In addition, claimants may sue GenVec for injury or contamination that results from GenVec’s use or the use by third parties of these materials, and GenVec’s liability may exceed its total assets.

Although GenVec has general liability insurance, these policies contain exclusions from insurance against claims arising from pollution from chemical or radioactive materials. GenVec’s collaborators are working with these types of hazardous materials in connection with its collaborations. In the event of a lawsuit or investigation, GenVec could be held responsible for any injury it or its collaborators cause to persons or property by exposure to, or release of, any hazardous materials. Although GenVec believes it is currently in compliance with all applicable environmental and occupational health and safety regulations, compliance with environmental laws and regulations may be expensive and current or future environmental regulations may impair its research, development, or production efforts.

GenVec’s revenue is primarily derived from GenVec’s collaboration agreements, which can result in significant fluctuation in GenVec’s revenue from period to period, and GenVec’s past revenue is therefore not necessarily indicative of GenVec’s future revenue.

GenVec’s revenue is primarily derived from GenVec’s collaboration agreements with corporate partners, institutions, and governmental entities under which GenVec may receive grants, milestone payments based on clinical progress, regulatory progress or net sales achievements, royalties, manufacturing revenue or payment for GenVec’s development activities on behalf of third parties. GenVec is particularly dependent on its agreement with Novartis, pursuant to which GenVec is facilitating the development of first-in-class products for the treatment of hearing and balance disorders. On February 11, 2014, Novartis informed GenVec that the third milestone under GenVec’s agreement with Novartis had been achieved after Novartis filed an IND with the FDA for the clinical development of CGF166, the lead product candidate under the collaboration between GenVec and Novartis. The IND was deemed effective on February 7, 2014, triggering a $2 million milestone payment to GenVec. On October 28, 2014, the fourth milestone under GenVec’s agreement with Novartis was achieved after the first patient was dosed in the Phase 1/2 clinical trial of CGF166, triggering a $3 million milestone payment to GenVec. Significant variations in the timing of receipt of cash payments and GenVec’s recognition of revenue can result from the timing of clinical, regulatory or sales events which result in milestone payments and the timing and success of the commercial launch of new products by GenVec’s collaboration partners. The amount of GenVec’s revenue derived from collaboration agreements in any given period will depend on a number of unpredictable factors, including GenVec’s ability to find and maintain suitable collaboration partners, the timing of the negotiation and conclusion of collaboration agreements with such partners, whether and when GenVec or its collaboration partner achieve clinical, regulatory and sales milestones, whether the collaboration is exclusive

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or whether GenVec can seek other partners, the timing of regulatory approvals in one or more major markets and the market introduction of new products or generic versions of the approved product, as well as other factors.

GenVec depends on a limited number of collaborators for a significant portion of its revenues, and the loss of or significant reduction in business with those business partners could materially adversely affect GenVec’s business and operating results.

Novartis and the U.S. government accounted for approximately 80% and 83% of GenVec’s revenues for the years ended December 31, 2016 and 2015, respectively. While the concentration of GenVec’s business with a small number of collaborators may provide certain benefits to us, it also exposes GenVec to adverse effects in the event of a disruption in GenVec’s relationship with any of them. GenVec is particularly dependent on its agreement with Novartis. If Novartis or the U.S. government decreases business with GenVec, fails to fulfill its obligations to GenVec, or terminates its relationship with GenVec, GenVec could experience material adverse effects on its business, operating results and financial condition.

Changes in healthcare law and implementing regulations, including those based on recently enacted legislation, as well as changes in healthcare policy, may impact GenVec’s business in ways that GenVec cannot currently predict, and these changes could have a material adverse effect on GenVec’s business and financial condition if GenVec is able to commercialize its candidate products.

Healthcare costs have risen significantly over the past decade. The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, which we refer to collectively as PPACA, substantially changes the way health care is financed by both governmental and private insurers and significantly impacts the pharmaceutical industry. PPACA contains a number of provisions that are expected to impact GenVec’s business and operations, in some cases in ways GenVec cannot currently predict. Changes that may affect GenVec’s business include those governing enrollment in federal and private healthcare programs, increased rebates and taxes on pharmaceutical products, and revised fraud and abuse and enforcement requirements. These changes will impact existing government healthcare programs and will result in the development of new programs.

GenVec anticipates that if and when it or its collaborators commercialize GenVec’s products in the U.S., a significant portion of GenVec’s revenue and the revenue from its collaborators from sales of its products will be derived from government payers, including Medicare, Medicaid, and Department of Defense, referred to herein as DoD, programs. Reimbursement rates to purchasers of GenVec’s drugs and its net revenues for sales of drugs used by these programs can be altered by legislation or regulation. PPACA and other federal law require rebates on certain drugs utilized under Medicare, Medicaid, and DoD programs and require discounts on certain drugs furnished to Medicare beneficiaries. For example, as part of PPACA’s provisions closing a funding gap that currently exists in the Medicare Part D prescription drug program (commonly known as the “donut hole”), once GenVec or its collaborators participate in the Medicare program, it or its collaborators will be required to provide a 50% discount on branded prescription drugs dispensed to beneficiaries within this donut hole.

PPACA also made changes to the Medicaid drug rebate program, discussed further herein, including changing the definition of AMP, expanding rebate liability from fee-for-service Medicaid utilization to include the utilization of Medicaid managed care organizations as well, and increasing the minimum rebate from 15.1% to 23.1% of the AMP for most innovator products and from 11% to 13% for non-innovator products. GenVec expects that the increased minimum rebate of 23.1% will apply to GenVec’s products following commercialization, if successful, in the U.S. Furthermore, PPACA requires pharmaceutical manufacturers of branded prescription drugs to pay a branded prescription drug fee to the federal government. Each individual pharmaceutical manufacturer pays a prorated share of the branded prescription drug fee of $4.0 billion in 2017, based on the dollar value of its branded prescription drug sales to certain federal programs identified in the law.

The effects of reforms under PPACA will be shaped significantly by implementing regulations and by state government decisions. On February 1, 2016, the Centers for Medicare and Medicaid Services, referred to herein

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as CMS, the federal agency that administers the Medicare and Medicaid programs, issued a final regulation to implement the changes to the Medicaid drug rebate program under PPACA. This regulation became effective on April 1, 2016. Many states have not chosen to expand their Medicaid programs by raising the income limit to 133% of the federal poverty level, as is permitted by PPACA. It is unclear whether these states will choose to expand their programs in the future and whether there will be more uninsured patients than anticipated when Congress passed PPACA. For each state that does not choose to expand its Medicaid program as permitted by PPACA, there will be fewer insured patients overall. The reduction in the number of insured patients could impact the sales, business and financial condition following the commercialization, if successful, of GenVec’s products in the U.S.

PPACA also expanded the Public Health Service’s 340B drug pricing discount program. A pharmaceutical manufacturer must participate in the 340B drug pricing program in order for federal funds to be available to pay for the pharmaceutical manufacturer’s drugs under Medicaid and Medicare Part B. Under this program, the participating pharmaceutical manufacturer agrees to charge statutorily-defined covered entities no more than the 340B discounted ceiling price for the pharmaceutical manufacturer’s covered outpatient drugs. PPACA obligates the Secretary of the Department of Health and Human Services to create regulations and processes to improve the integrity of the program and to ensure the agreement that manufacturers must sign to participate in the program obligates a manufacturer to offer the ceiling price to covered entities if the manufacturer makes the drug available to any other purchaser at any price and to report to the government the ceiling prices for its drugs. In addition, legislation may be introduced that, if passed, could further expand the 340B drug pricing program to include additional covered entities or could require participating manufacturers to agree to provide 340B discounted pricing on drugs used in the inpatient setting. To the extent that PPACA and subsequent legislation, as discussed above, causes the statutory and regulatory definitions of AMP and the Medicaid rebate amount to change, these changes also impact the 340B discounted ceiling price.

Legislative changes to PPACA and new or revised regulations remain possible and appear likely in the 115th Congress and under the Trump Administration. These changes could affect all of the PPACA-related policies discussed above and could have a significant effect on the number of insured patients in the U.S., the breadth of coverage under insurance plans, financing of healthcare, and reimbursement rates, which could impact GenVec’s sales, business, and financial condition following the commercialization, if successful, of GenVec’s products in the U.S. GenVec expects that PPACA, as currently enacted or as it may be amended in the future, and other healthcare reform measures that may be adopted in the future, could have a material adverse effect on GenVec’s industry generally and on its ability to successfully commercialize its product candidates, if approved.

In addition to PPACA, there will continue to be proposals by legislators at both the federal and state levels, regulators and third-party payers to keep these costs down while expanding individual healthcare benefits. Certain of these changes could impose limitations on the prices GenVec will be able to charge for any product candidates that are approved or the amounts of reimbursement available for these products from governmental agencies or third-party payers, or may increase the tax obligations on life sciences companies such as GenVec’s.

The healthcare industry, and thus GenVec’s business, continues to be subject to extensive federal, state, local and foreign regulation. Some of the pertinent laws have not been definitively interpreted by the regulatory authorities or the courts, and their provisions are open to a variety of interpretations. In addition, these laws and their interpretations are subject to change. Applicable federal and state health care fraud and abuse laws and regulations may affect GenVec’s ability to operate GenVec’s business, particularly once third-party reimbursement becomes available for one or more of GenVec’s products. These laws and regulations include, but are not limited to:

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If GenVec’s operations are found to be in violation of any of the laws described above or any other governmental regulations that apply to GenVec, GenVec may be subject to significant civil, criminal and administrative penalties, damages, fines, imprisonment, exclusion from government-funded healthcare programs like Medicare and Medicaid, and the curtailment or restructuring of GenVec’s operations, any of which could adversely affect its ability to operate its business and its financial results. Although compliance programs can mitigate the risk of investigation and prosecution for violations of these laws, the risks cannot be entirely eliminated. Any action against GenVec for violation of these laws or regulations, even if GenVec successfully defends against it, could cause GenVec to incur significant legal expenses and divert its management’s attention from the operation of its business. Moreover, achieving and sustaining compliance with applicable federal and state privacy, security and fraud laws could result in government enforcement actions and create liability for GenVec (which could include civil and/or criminal penalties), private litigation and/or adverse publicity that could negatively affect GenVec’s operating results and business.

If third party payers do not provide coverage or reimbursement for GenVec’s products, those products will not be widely accepted, which would have a negative impact on GenVec’s business, results of operations and financial conditions.

Even if a product of GenVec’s receives regulatory approval, GenVec’s success will depend, in part, on the extent to which coverage and reimbursement will be available from third party payers such as Medicare, Medicaid, other government health programs, private health insurers, managed care programs, and other organizations. Third party payers are increasingly challenging the price and cost-effectiveness of medical products and services, and this trend is expected to continue. Therefore, significant uncertainty exists as to the pricing approvals for, and the coverage or reimbursement status of, newly approved healthcare products. Additional federal or state health care legislation may be adopted in the future, any products that GenVec seeks to commercialize may not be

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considered cost-effective, and limitations on coverage and the amount of reimbursement for GenVec’s products could be imposed. Adequate third-party insurance coverage may not be available for GenVec to establish and maintain price levels that are sufficient for realization of an appropriate return on GenVec’s investment in product development. Moreover, the existence or threat of cost control measures, including a reduction in reimbursement rates could cause potential corporate collaborators to be less willing or able to pursue research and development programs related to GenVec’s product candidates. GenVec cannot be certain that, if and when GenVec’s products become commercialized, the pertinent reimbursement amounts or formulary status for GenVec’s products will be sufficient to enable GenVec to market and sell its products.

GenVec’s business involves animal testing and changes in laws, regulations, accepted clinical procedures, or social pressures could restrict GenVec’s use of animals in testing and adversely affect its research and development efforts.

Many of the research and development efforts GenVec sponsors involve the use of laboratory animals. Changes in laws, regulations, or accepted clinical procedures may adversely affect these research and development efforts. Social pressures that would restrict the use of animals in testing or actions against GenVec or its partners by groups or individuals opposed to testing using animals could also adversely affect these research and development efforts. In addition, preclinical animal studies conducted by GenVec or third parties on its behalf may be subject to the FDA’s Good Laboratory Practices regulations and the USDA regulations for certain animal species. Failure to comply with applicable regulations could extend or delay clinical trials conducted for its drug candidates.

GenVec depends on its key technical and management personnel to advance its technology and implement its business strategy, and the loss of these personnel could impair the development of its products and business.

GenVec relies, and will continue to rely, on its key management and scientific staff, all of whom are employed at will. GenVec’s success depends upon the ability of its senior management to implement its business strategy. The loss of key personnel could have a material adverse effect on GenVec’s business and results of operations. There is intense competition from other companies, research and academic institutions and other organizations for qualified personnel. GenVec may not be able to continue to attract and retain the qualified personnel necessary for the development of its business. If GenVec does not succeed in retaining and recruiting necessary personnel or developing this expertise, its business could suffer significantly. Furthermore, changes in its senior management may lead to instability for GenVec which could cause its business to suffer significantly.

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Cautionary note regarding forward-looking statements

This proxy statement/prospectus contains forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act with respect to the businesses, strategies and plans of Intrexon and GenVec, their expectations relating to the merger and their future financial condition and performance. Forward-looking statements generally relate to future events or future financial or operating performance. In some cases, you can identify forward-looking statements because they contain words such as “may,” “will,” “should,” “would,” “expects,” “plans,” “anticipates,” “could,” “intends,” “target,” “projects,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these words or other similar terms or expressions that concern Intrexon’s and GenVec’s expectations, strategies, plans or intentions. Intrexon’s and GenVec’s expectations and beliefs regarding these matters may not materialize, and actual results in future periods are subject to risks and uncertainties that could cause actual results to differ materially from those projected, including but not limited to:

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Forward-looking statements may also concern Intrexon’s expectations relating to its subsidiaries and other affiliates. Intrexon and GenVec also caution you that the foregoing list may not contain all of the forward-looking statements made in this proxy statement/prospectus.

Due to these risks and uncertainties, there can be no assurances that the results anticipated by the forward-looking statements of Intrexon or GenVec will occur, that their respective judgments or assumptions will prove correct or that unforeseen developments will not occur. Furthermore, if these forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you are cautioned not to place undue reliance upon any forward-looking statements of Intrexon or GenVec, which speak only as of the date made. Intrexon and GenVec undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future events, changed circumstances or otherwise, except as required by law.

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The GenVec special meeting

This section contains information about the special meeting of GenVec shareholders that has been called to consider and vote on the merger proposal, the merger-related compensation proposal and the adjournment proposal. This proxy statement/prospectus is being furnished to GenVec shareholders in connection with the solicitation of proxies by the GenVec board of directors for use at the special meeting and any postponements or adjournments of such special meeting.

This proxy statement/prospectus and the enclosed proxy card are first being mailed to GenVec shareholders on or about May 15, 2017. This proxy statement/prospectus provides GenVec shareholders with information about the special meeting and should be read carefully in its entirety.

Date, time and place of the special meeting

The special meeting will be held on June 15, 2017, at 8:30 a.m., Eastern Daylight Time, at 910 Clopper Road, Suite 220N, Gaithersburg, Maryland 20878.

Purpose of the special meeting

At the special meeting you will be asked to consider and vote upon:

At the special meeting, GenVec may also conduct any other business properly brought before the special meeting and any adjournment or postponement thereof.

Recommendations of the GenVec board of directors

The GenVec board of directors reviewed and considered the terms and conditions of the merger agreement and the transactions contemplated thereby, including the merger and, after careful consideration, has unanimously:

The GenVec board of directors unanimously recommends that GenVec’s shareholders vote “ FOR ” the merger proposal, “ FOR ” the merger-related compensation proposal and “ FOR ” the adjournment proposal.

Record date; stock entitled to vote

The GenVec board of directors has fixed the close of business on April 28, 2017 as the record date for the determination of shareholders entitled to notice of, and to vote at, the special meeting and at any adjournment or

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postponement of the special meeting. At the close of business on the record date, there were 2,273,632 shares of GenVec common stock outstanding and entitled to vote held by 17 holders of record. As of the record date, the directors and executive officers of GenVec and their affiliates as a group owned and were entitled to vote 72,437 shares of GenVec common stock, or approximately 3.2% of the shares of GenVec common stock outstanding and entitled to vote as of that date.

A list of shareholders of record of GenVec entitled to vote at the special meeting will be available for ten days prior to the special meeting at GenVec’s office at 910 Clopper Road, Suite 220N, Gaithersburg, Maryland 20878, for inspection by shareholders of GenVec during ordinary business hours for any purpose germane to the special meeting.

Quorum

A quorum is necessary to conduct business at the special meeting. The presence, in person or by proxy, of the holders of a majority of the outstanding shares of GenVec common stock entitled to vote is necessary to constitute a quorum for action on any subject matter at the special meeting.

Shareholders of record who are present at the special meeting in person or by proxy and who abstain from voting are considered present and count toward the quorum. If your shares are held in “street name,” meaning that your shares are held by a broker, bank or other nominee, your broker, bank or other nominee may not vote your shares on “non-routine” matters without instructions from you. As each of the proposals to be voted upon at the special meeting is considered “non-routine,” your broker, bank or other nominee does not have discretion to vote on any proposal for which they do not receive instructions from you. As a result, if you fail to provide your broker, bank or other nominee with any instructions regarding how to vote your shares, your shares will not be considered present at the special meeting, will not be counted for purposes of determining the presence of a quorum and will not be voted on any of the proposals. If you provide instructions to your broker, bank or other nominee that indicate how to vote your shares with respect to certain proposals but not with respect to a particular proposal, your shares will be considered present at the special meeting and will be counted for purposes of determining the presence of a quorum, but they will not be voted with respect to that particular proposal (this is referred to as a “broker non-vote”).

Required vote

Voting rights

Each GenVec shareholder is entitled to one vote on each matter to be acted upon at the special meeting for each share of GenVec common stock owned by such shareholder as of the record date.

Abstentions and broker non-votes

If you are a shareholder of record and vote “ABSTAIN” on the merger proposal, the merger-related compensation proposal or the adjournment proposal, it will have the same effect as voting “AGAINST” such

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proposal. Likewise, if your shares are held in “street name,” meaning that your shares are held by a broker, bank or other nominee, and you instruct your broker, bank or other nominee to vote “ABSTAIN” on the merger proposal, the merger-related compensation proposal or the adjournment proposal, it will have the same effect as voting “AGAINST” such proposal.

If you are a shareholder of record and do not vote by completing your proxy card, by telephone or in person at the special meeting (as described below in the section entitled “Voting at the special meeting”), your shares will not be voted. This will have the same effect as voting “AGAINST” the merger proposal, but it will have no effect on the outcome of the merger-related compensation proposal or the adjournment proposal.

If your shares are held in street name and you do not provide your broker, bank or other nominee with instructions as to how to vote your shares on a particular proposal, your shares will not be voted on that proposal (as noted above, this is referred to as a “broker non-vote”). This will have the same effect as voting “AGAINST” the merger proposal, but it will have no effect on the outcome of the merger-related compensation proposal or the adjournment proposal.

Voting at the special meeting

Whether or not you plan to attend the special meeting, please promptly vote your shares of GenVec common stock by proxy or, if you hold your shares in street name, instruct your broker, bank or other nominee how to vote, to ensure your shares are represented at the meeting. You may also vote in person at the special meeting.

Voting in person

If you plan to attend the special meeting and wish to vote in person, you will be given a ballot at the special meeting. Please note, however, that if your shares of GenVec common stock are held in “street name,” meaning that your shares are held by a broker, bank or other nominee, and you wish to vote in person at the special meeting, you must bring to the special meeting (i) a letter, account statement or other evidence from such broker, bank or other nominee indicating that you were the beneficial owner of the shares on the record date for the special meeting and (ii) a legal proxy from the record holder of the shares of GenVec common stock (i.e., your broker, bank or nominee) authorizing you to vote at the special meeting.

Voting by proxy; voting instructions

Shareholders of Record : You should vote your proxy even if you plan to attend the special meeting. You can always change your vote at the special meeting. Registered shareholders may vote by mail or by telephone.

Your enclosed proxy card includes specific instructions for voting your shares of GenVec common stock. When the accompanying proxy card is returned properly executed, the shares of GenVec common stock represented by it will be voted at the special meeting or any adjournment thereof in accordance with the instructions contained in the proxy card.

If you return your signed proxy card without indicating how you want your shares of GenVec common stock to be voted with regard to a particular proposal, your shares will be voted as recommended by the GenVec board of

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directors. The GenVec board of directors has unanimously recommended that GenVec’s shareholders vote “ FOR ” the merger proposal, “ FOR ” the merger-related compensation proposal and “ FOR ” the adjournment proposal. Proxy cards that are returned without a signature will not be counted as present at the special meeting and cannot be voted.

If the special meeting is postponed or adjourned for any reason, at any subsequent reconvening of the special meeting all proxies will be voted in the same manner as the proxies would have been voted at the original convening of the special meeting, except for any proxies that have at that time effectively been revoked or withdrawn, even if the proxies had been effectively voted on the same or any other matter at a previous meeting.

Shares Held in Street Name : If your shares are held of record in “street name,” meaning that your shares are held by a broker, bank or other nominee, you should follow the separate instructions that such broker, bank or other nominee provides to you. Although most banks and brokers now offer telephone and Internet voting, availability and specific processes will depend on their voting arrangements.

Revocation of proxies or voting instructions

If you are a registered holder and give your proxy card to GenVec or vote by telephone, you have the power to revoke your proxy or change your vote by taking any of the following actions before your proxy is voted at the special meeting:

If your shares are held in street name by your broker, bank or other nominee, you should contact them to change your vote.

Notice of revocation or your new proxy must be delivered to GenVec’s Corporate Secretary at 910 Clopper Road, Suite 220N, Gaithersburg, Maryland 20878, Attention: Corporate Secretary.

Other matters

As of the date of this proxy statement/prospectus, the GenVec board of directors is not aware of any other business to be presented for consideration at the special meeting.

Solicitation of proxies

The GenVec board of directors is soliciting proxies to provide an opportunity to all GenVec shareholders to vote on agenda items at the special meeting, whether or not the shareholders are able to attend the special meeting or an adjournment or postponement thereof. GenVec will pay all costs incurred in connection with the solicitation of proxies from its shareholders on behalf of its board of directors. In addition to solicitation by mail, the directors, officers and regular employees of GenVec may, without any additional compensation for their services, solicit proxies from shareholders in person or by telephone, facsimile or otherwise.

Arrangements also will be made with brokers, banks, trustees and other custodians, nominees and fiduciaries for the forwarding of solicitation material to the beneficial owners of stock held of record by such persons, and GenVec will reimburse such custodians, nominees and fiduciaries for their reasonable out-of-pocket expenses in connection therewith.

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GenVec has retained Saratoga to assist it in the solicitation of proxies. The fee payable to Saratoga in connection with the proxy solicitation is $12,500 and an additional fee of $4.00 per telephonic contact, plus reimbursement for reasonable out-of-pocket expenses.

Additional questions

If you have questions about the merger agreement, the merger or the merger proposal or the other matters to be voted on at the special meeting or desire additional copies of this proxy statement/prospectus or additional proxy cards, please contact Saratoga by calling toll-free at (888) 368-0379. Banks, brokerage firms, and other nominees may call collect at (212) 257-1311.

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The companies

Intrexon Corporation    

Intrexon believes it is a leader in the field of synthetic biology, an emerging and rapidly evolving discipline that applies engineering principles to biological systems to enable rational, design-based control of cellular function for a specific purpose. Using its suite of proprietary and complementary technologies, Intrexon designs, builds and regulates gene programs, which are DNA sequences that consist of key genetic components. A single gene program or a complex, multi-genic program is fabricated and stored within a DNA vector. Vectors are segments of DNA used as a vehicle to transmit genetic information. DNA vectors can, in turn, be introduced into cells in order to generate a simple or complex cellular system, which are the basic and complex cellular activities that take place within a cell and the interaction of those systems in the greater cellular environment. It is these genetically modified cell systems that can be used to produce biological effector molecules, or be employed directly to enable the development of new and improved products and manufacturing processes across a variety of end markets, including health, food, energy, environment and consumer. Intrexon’s synthetic biology capabilities include the ability to precisely control the amount, location and modification of biological molecules to control the function and output of living cells and optimize for desired results at an industrial scale.

Working with its collaborators, Intrexon seeks to create more effective, less costly and more sustainable solutions than can be provided through current industry practices. Intrexon believes its approach to synthetic biology can enable new and improved biotherapeutics, increase the productivity and quality of food crops and livestock, create sustainable alternative energy sources and chemical feedstocks, utilize biologically-based applications for the delivery of innovative consumer products and provide for a diverse set of environmental solutions. Intrexon’s business model is to commercialize its technologies through ECCs with collaborators that have industry expertise, development resources and sales and marketing capabilities to bring new and improved products and processes to market.

Intrexon is incorporated in Virginia. Intrexon’s common stock is traded on the NYSE under the symbol “XON.” The principal executive offices of Intrexon are located at 20374 Seneca Meadows Parkway, Germantown, Maryland 20876, and its telephone number is (301) 556-9900.

For more information regarding Intrexon’s business, see Item 1 of Intrexon’s Annual Report on Form 10-K for its 2016 fiscal year and the other documents incorporated by reference into this proxy statement/prospectus. For information on how you can view Intrexon’s Annual Report on Form 10-K and other documents incorporated by reference into this proxy statement/prospectus, see the section entitled “Where you can find more information.”

GenVec, Inc.

GenVec is a clinical-stage biopharmaceutical company with an entrepreneurial focus on leveraging its proprietary AdenoVerse™ gene delivery platform to develop a pipeline of cutting-edge therapeutics and vaccines. GenVec is a pioneer in the design, testing and manufacture of adenoviral-based product candidates that can deliver on the promise of gene-based medicine. GenVec’s lead product candidate, CGF166, is licensed to Novartis and is currently in a Phase 1/2 clinical study for the treatment of hearing loss and balance disorders. In addition to its internal and partnered pipeline, GenVec also focuses on opportunities to license its proprietary technology platform, including vectors and production cell lines, to potential collaborators in the biopharmaceutical industry for the development and manufacture of therapeutics and vaccines.

GenVec is incorporated in Delaware. GenVec’s common stock is traded on NASDAQ under the symbol “GNVC.” The principal executive offices of GenVec are located at 910 Clopper Road, Suite 220N, Gaithersburg, Maryland 20878, and its telephone number is (240) 632-0740.

For more information regarding GenVec’s business, see the section entitled “Description of GenVec’s business.”

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Intrexon GV Holding, Inc.

Merger Sub is a wholly owned subsidiary of Intrexon formed solely for the purpose of effecting the merger. Merger Sub is incorporated in Delaware.

Merger Sub has not conducted any activities other than those incidental to its formation and the matters contemplated by the merger agreement, including the preparation of applicable regulatory filings in connection with the merger. The principal executive offices of Merger Sub are located at 20374 Seneca Meadows Parkway, Germantown, Maryland 20876, and its telephone number is (301) 556-9900.

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The merger

(Proposal 1)

Effects of the merger

The shareholders of GenVec are being asked to adopt the Agreement and Plan of Merger, dated as of January 24, 2017, by and among GenVec, Intrexon, and Merger Sub.

Pursuant to the terms and subject to the conditions of the merger agreement, at the closing of the proposed transactions contemplated by the merger agreement, Merger Sub will be merged with and into GenVec. GenVec will continue as the surviving corporation of the merger, but it will become a wholly owned subsidiary of Intrexon. At the effective time of the merger, each share of GenVec common stock (other than shares with respect to which appraisal rights are properly exercised or shares owned by Intrexon, any of its subsidiaries or GenVec) will be converted into the right to receive 0.297 of a share of Intrexon common stock (with cash paid in lieu of fractional shares) and one CPR. For information regarding the treatment of GenVec stock options and warrants in the merger, see the section entitled “The merger agreement—Treatment of GenVec stock options and warrants.”

The merger agreement does not contain any provision that would adjust the exchange ratio that applies to the stock consideration based on fluctuations in the market value of Intrexon’s common stock. Because of this, the implied value of the stock consideration to GenVec shareholders will fluctuate between now and the completion of the merger and will depend on the market value of Intrexon common stock at the time the merger is completed. For information regarding the CPRs, see the section entitled “Contingent payment rights agreement.”

Background of the merger

Introduction

GenVec is a biopharmaceutical company whose business had been developing novel, gene-based therapeutic drugs and vaccines. In March 2010, GenVec discontinued a pivotal Phase 3 clinical trial for TNFerade, its then lead and only clinical stage human therapeutic product candidate. As a result of discontinuing that trial and the early stage nature of GenVec’s other programs, GenVec began reevaluating its business strategy. In June 2010, GenVec retained Wells Fargo Securities, LLC to conduct a comprehensive review of strategic alternatives aimed at enhancing shareholder value. As part of that process, GenVec solicited proposals for strategic transactions, including for the disposition of some or all of GenVec’s assets, or for the sale or merger of the entire entity. When GenVec did not receive acceptable proposals for strategic transactions by November 2010, the board of directors of GenVec announced that it would continue to explore strategic opportunities while focusing on GenVec’s core business.

Despite GenVec’s efforts to seek strategic opportunities, between November 2010 and April 2013, it had no programs that offered any near-term prospects for significant revenues or meaningful value-creating achievements. By April 2013, GenVec had begun taking significant steps to reduce its cash burn rate, including by cutting back on development programs, employee headcount and related expenses. Regardless, GenVec continued to lack prospects to achieve significant revenues in the near term and had limited prospects to achieve significant additional revenues before GenVec would use its existing capital resources. Without meaningful prospects, in May 2013 the GenVec board of directors held a meeting for the purpose of considering the liquidation and dissolution of GenVec. At this meeting, the GenVec board of directors unanimously determined that the liquidation and dissolution of GenVec was fair and in the best interests of GenVec and its shareholders.

On August 8, 2013, GenVec filed a preliminary proxy statement pursuant to Section 14(a) of the Exchange Act for the purpose of giving notice of a special meeting of the shareholders to approve the liquidation and dissolution of GenVec. However, on September 4, 2013, GenVec announced that the GenVec board of directors unanimously withdrew the plan of complete liquidation and dissolution for GenVec that was previously adopted

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on May 24, 2013, announcing that it would instead pursue a strategy focused on maximizing the value of its technology and assets, including its collaboration with Novartis to develop a novel gene-therapy treatment for hearing loss and balance disorders.

Over the next three years GenVec focused its efforts on assisting Novartis with developing CGF166, an adenoviral vector engineered to express the human atonal gene for patients with severe hearing loss, and engaging third parties, including governmental entities and universities, to research and develop new therapies in collaboration with GenVec using its proprietary adenovirus vector technology. Additionally, GenVec continued to support its operations through equity financings.

In December 2013, GenVec announced approval of the protocol for initiation of a Phase 1 study of CGF166. Between December 2013 and January 2016, GenVec and Novartis continued clinical development of CGF166.

Prior to and during this period, GenVec and Intrexon were in communication at several points regarding various potential collaborations and transactions. For example, prior to the decision to pursue a dissolution in 2013, GenVec and Intrexon had shared information in consideration of a potential strategic transaction. In January 2014, Intrexon and GenVec entered into a material transfer agreement pursuant to which GenVec would incorporate certain transgenes developed by Intrexon into GenVec’s proprietary adenovirus based vectors for gene delivery applications for Intrexon’s oncology programs. However, subsequent to entering into the material transfer agreement, Intrexon elected not to pursue the research covered under the agreement. During 2014, GenVec was approached by Intrexon regarding the possibility of amending the material transfer agreement to instead focus on animal health applications of GenVec’s proprietary gene delivery technology. Following these discussions, the parties were not able to agree to mutually acceptable terms and negotiations ended in December 2014. In August 2015 GenVec was approached by Intrexon regarding a potential exclusive channel collaboration with respect to a product concept being explored by Intrexon not related to GenVec’s proprietary technology platform. On August 14, 2015, GenVec and Intrexon entered into a confidentiality agreement to permit the parties to engage in discussions regarding this potential collaboration. Following these discussions, GenVec notified Intrexon that it did not wish to pursue the project and discussions ended in September 2015.

During this period, GenVec continued its business development efforts and, on March 23, 2015, it announced a new collaboration with TheraBiologics, Inc. to develop cancer therapeutics leveraging both GenVec’s proprietary gene delivery platform and TheraBiologics’ proprietary neural stem cell technology. In order to further ongoing business development efforts, in December 2015, GenVec’s board of directors approved the establishment of a business development committee to review, evaluate and recommend to GenVec’s board of directors business development transactions. Despite its extensive business development and clinical research efforts, GenVec was unable to establish any major pipeline programs outside of its Novartis collaboration that provided GenVec the potential for substantial revenues in the near term. In connection with its business development efforts, GenVec regularly enters into confidentiality and similar agreements to facilitate discussions between parties, however, none of those confidentiality or similar agreements contain any “standstill” or similar provisions that are still in effect.

On January 8, 2016, Novartis notified GenVec that it was pausing enrollment in the Phase 1/2 trial of CGF166 to conduct a safety review of patient data, based on the recommendation of the trial’s data safety monitoring board. Following the public announcement of the clinical hold on January 11, 2016, the price of GenVec’s common stock dropped from a closing price of $1.72 on the Nasdaq Capital Market (which price does not take into account the reverse stock split) on January 8, 2016, the day prior to the announcement, to a closing price of $0.72 on the trading day of the announcement. As a result of this price drop, on February 24, 2016 GenVec received notice from NASDAQ that the minimum bid price of its common stock had remained below $1.00 for 30 consecutive business days, and it therefore was not in compliance with the minimum bid price requirement for continued listing.

In May 2016, GenVec announced that it expected that the trial of CGF166 would resume, and GenVec undertook capital raising efforts to address its cash needs. On May 4, 2016, GenVec entered into a Securities Purchase Agreement with certain investors for the sale of approximately 547,196 shares of GenVec’s common stock (as

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adjusted for the reverse stock split), at a purchase price of $9.1375 per share and the concurrent sale of warrants to purchase approximately 410,397 shares of common stock for aggregate gross proceeds of approximately $5 million.

On July 25, 2016, Novartis notified GenVec that the FDA had lifted the clinical hold on the trial.

In order to regain compliance with the minimum bid price requirement, effective December 1, 2016 GenVec effected a one-for-ten reverse stock split of its outstanding common stock. After the reverse stock split, on December 15, 2016 GenVec received notice from the Listing Qualifications Department of NASDAQ stating that it had regained compliance with the $1.00 minimum bid price requirement for continued listing.

Through the first half of May 2016, GenVec continued with its business development and clinical research efforts, but did not enter into any agreements or identify any opportunities that were likely to result in opportunities in the near term.

Detailed Timeline of Events

On May 18, 2016, Thomas Reed, Ph.D., Founder and Chief Science Officer of Intrexon, contacted Douglas Swirsky, President and Chief Executive Officer of GenVec, asking for a meeting with Mr. Swirsky. The next day, Mr. Swirsky and Dr. Reed met to discuss the possibility of a strategic transaction between GenVec and Intrexon. On the following day, Mr. Swirsky e-mailed Dr. Reed a non-confidential presentation regarding GenVec’s AdenoVerse technology platform. Dr. Reed and Mr. Swirsky then corresponded regarding the differences between GenVec’s AdenoVerse technology platform and the delivery platform of a third party.

On May 26, 2016, Dr. Reed requested a meeting between the GenVec and Intrexon teams to discuss GenVec’s technology, programs and capabilities; in response, Mr. Swirsky provided support for the meeting and confirmed that the confidentiality agreement entered into by the parties in August 2015 remained effective. The meeting was held at Intrexon’s offices in Germantown, Maryland on June 3, 2016. Following this meeting, Dr. Reed and Mr. Swirsky exchanged e-mails regarding GenVec’s technology, experience and capabilities in human and animal health vaccines.

Dr. Reed and Mr. Swirsky met in Palm Beach, Florida on June 22, 2016, at which time Dr. Reed reiterated Intrexon’s interest in a strategic transaction involving GenVec. However, Dr. Reed also explained that Intrexon had certain competing interests and priorities that would delay further discussions between the parties for several weeks.

Despite the delay in further negotiations, on August 14, 2016 GenVec and Intrexon executed an amendment to the confidentiality agreement previously entered into in August 2015 to extend confidentiality obligations thereunder until August 14, 2017.

Between August and November of 2016, consistent with its strategic plan, GenVec continued to engage in discussions with third parties regarding potential business development and capital raising transactions. On September 2, 2016, based on potential business development opportunities with other parties Mr. Swirsky sent Dr. Reed an e-mail stating that a strategic transaction was no longer a preferred outcome for GenVec and inquiring as to Intrexon’s interest in a more focused collaboration.

GenVec continued to pursue other business development opportunities. However, GenVec’s business development efforts during this time did not eventually result in any near-term developments, and, on November 2, 2016, Mr. Swirsky contacted Dr. Reed via e-mail to follow up on prior discussions. That same day, Dr. Reed and Mr. Swirsky spoke about GenVec’s business development efforts that were maturing at a slow pace relative to its capital needs and Mr. Swirsky expressed a willingness to revisit a possible strategic transaction with Intrexon. On this call Dr. Reed requested that Mr. Swirsky provide an outline of the licensing transactions for the AdenoVerse technology that GenVec was exploring. Mr. Swirsky provided a redacted version of this outline to Dr. Reed on November 6, 2016.

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After these initial discussions with Mr. Swirsky, Dr. Reed introduced Mr. Swirsky via e-mail to Nir Nimrodi, Intrexon’s Senior Vice President of Corporate Development. On November 9, 2016, Mr. Swirsky spoke with Mr. Nimrodi to discuss logistics for Intrexon’s evaluation of GenVec’s technology, programs and capabilities. The following day Mr. Swirsky sent Mr. Nimrodi an overview of GenVec’s financial projections to provide information on GenVec’s cost structure. For information regarding the treatment of GenVec’s financial projections, see the section entitled “The merger agreement—Certain financial projections of GenVec’s management.”

Over the following few weeks, Intrexon continued to review GenVec’s technology, programs, capabilities and financial outlook and to assess a potential strategic transaction between the two companies. On November 22, 2016, Intrexon delivered to GenVec a letter expressing interest in pursuing a strategic transaction with GenVec and requesting that the two companies negotiate an exclusivity agreement to provide Intrexon with an exclusive period of time to evaluate the opportunity and to conduct due diligence on GenVec.

On November 25, 2016, the GenVec board of directors met by telephone to consider the request for the exclusive negotiating period requested by Intrexon. The GenVec board of directors discussed the scope of the exclusivity requested, the time period during which the exclusive due diligence and negotiating period would apply, and the potential that another transaction would need to be considered within this period. Following these discussions, the GenVec board of directors authorized Mr. Swirsky to enter into the exclusivity agreement, but to negotiate the shortest period that Intrexon would be willing to agree to for the period of the agreement.

On November 29, 2016, GenVec and Intrexon executed an exclusivity agreement, which provided that, between November 29, 2016 and January 23, 2017, GenVec would refrain from (i) soliciting or accepting any offers for the acquisition of 20% or more of its outstanding securities or all of its assets, (ii) disclosing any non-public information to any entity with respect to such offers or (iii) entering into any agreement relating to such offers. Under the terms of this agreement, GenVec was permitted to request Intrexon’s confirmation that it was pursuing a transaction in good faith and, if Intrexon did not make such confirmation, GenVec could terminate the exclusivity at any time after December 26, 2016.

Immediately after executing the exclusivity agreement, Intrexon sent to GenVec’s outside counsel, Hogan Lovells US LLP, referred to herein as Hogan Lovells, Intrexon’s preliminary due diligence request list. On December 8, 2016, Mr. Swirsky sent GenVec’s responses to the preliminary due diligence request list to Intrexon. The following day, multiple members of the Intrexon business and technical teams were granted access to GenVec’s virtual data room.

On December 9, 2016, executives from Intrexon, including Dr. Reed; Donald Lehr, Chief Legal Officer; Mr. Nimrodi; Christian Ulrich, Chief M&A Counsel and several members of the scientific team at Intrexon, attended in person meetings at GenVec’s headquarters. This meeting was led by Mr. Swirsky, who was joined by members of GenVec’s corporate and scientific teams, including Douglas Brough, Ph.D., Chief Scientific Officer, Bryan Butman, Ph.D., Executive Vice President, Development, and James Lambert, Senior Director, Accounting & Financing, as well as representatives of Hogan Lovells. At this meeting, GenVec’s executive team presented its responses to Intrexon’s technical and non-technical diligence questions and answered additional questions from the Intrexon team. Additionally, Intrexon’s scientific team was offered the opportunity to tour GenVec’s facilities.

Between December 9 and December 21, the parties engaged in a due diligence process with respect to GenVec’s scientific, legal and financial matters. On December 13, Mr. Swirsky sent Mr. Nimrodi an e-mail confirming that GenVec had added a significant amount of information to the virtual data room and had opened the technical and scientific portion of the virtual data room. Mr. Ulrich then sent Mr. Swirsky on December 16 a list of supplemental due diligence requests based on Intrexon’s preliminary review of the documents uploaded to the virtual data room. GenVec sent Intrexon responses to the supplemental requests on December 20 and 21.

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On December 28, 2016, GenVec received a non-binding proposal from Intrexon to acquire 100% of the issued and outstanding stock of GenVec, in a stock-for-stock transaction, at an implied price of between $3.75 and $3.85 per share.

The board of directors of GenVec convened a telephonic meeting on December 30, 2016 at which all directors were in attendance, as well as representatives of Hogan Lovells. Mr. Swirsky opened this meeting by describing the background of discussions with Intrexon to date and then discussed the letter of intent provided by Intrexon. A representative of Hogan Lovells then provided background on discussions with Intrexon’s legal department. Mr. Swirsky highlighted for the GenVec board of directors management’s views on the limited business development and strategic transaction opportunities. The GenVec board of directors members agreed that it was not in the best interests of GenVec or its shareholders to accept the proposal from Intrexon and authorized Mr. Swirsky to respond to Mr. Nimrodi indicating the same. Additionally, the GenVec board of directors authorized Mr. Swirsky to request that Intrexon release GenVec from exclusivity on the basis that the offer was not acceptable to the GenVec board of directors. The GenVec board of directors also approved enabling a business development committee to engage in future strategic discussions with Intrexon and other parties, if any. Following the meeting of the GenVec board of directors, Mr. Swirsky sent Mr. Nimrodi a letter stating that GenVec believed that the parties were too far apart on perceived deal value to continue discussions and requested an early termination of the exclusivity period given the valuation gap.

On January 5, 2017, Mr. Nimrodi contacted Mr. Swirsky by email to schedule a telephone call, and they spoke later that day. During the conversation, Mr. Nimrodi stated that Intrexon intended to submit another offer rather than provide early termination of the exclusivity agreement.

In connection with the annual J.P. Morgan Healthcare Conference, both Mr. Swirsky and Dr. Reed were in San Francisco in the first part of January 2017. They met for dinner on January 8, 2017 and were joined by Dr. Brough. During dinner, Dr. Reed indicated that the Intrexon team was working on a revised proposal and the parties discussed the complementary technologies of the two companies.

Between January 9 and January 12, 2017, Mr. Swirsky, Dr. Brough, and members of GenVec’s business development team met with various potential business development and strategic partners who were also in San Francisco for meetings related to the J.P. Morgan Healthcare Conference in San Francisco. In parallel, GenVec continued to engage in discussions with third parties with respect to financing opportunities for GenVec through the capital markets.

After failing to receive a new offer from Intrexon by January 10, 2017, and with no business development transactions expected to occur in the near term, GenVec’s management determined that GenVec should engage in capital raising efforts both in order to meet its near-term cash needs and also to potentially help make GenVec a more attractive partner in business development efforts. On January 12, 2017, after discussions with management, the GenVec board of directors delegated full authority of the GenVec board of directors to a pricing committee to take actions necessary to authorize and issue up to $10 million of common stock at no less than $4.00 per share, together with warrants.

While GenVec was proceeding with capital raising efforts, at the direction of management, on January 13, 2017, representatives of Hogan Lovells contacted Mr. Lehr to inquire as to the status of Intrexon’s interest. Mr. Lehr indicated again that Intrexon was planning on presenting an offer to GenVec, but that Intrexon had not yet determined the proposed terms.

On January 17, 2017, GenVec concluded that the revised proposal discussed by Intrexon was unlikely, and entered into an engagement letter with an investment bank to assist GenVec with an offering of equity securities. As part of the engagement and at the recommendation of the bank, GenVec authorized the bank to contact potential investors for a private placement of preferred stock and warrants. During the afternoon of January 19, 2017, GenVec began negotiations with an institutional investor in connection with the proposed private

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placement transaction. GenVec and the potential investors continued negotiations throughout the evening of January 19, 2017 with the goal of announcing a transaction prior to the market opening on Friday, January 20, 2017. However, GenVec and the investors were unable to reach agreement on the transaction terms for the private placement prior to market open on January 20 and the parties agreed to continue to negotiate with the intent of announcing the financing during intra-day trading if the terms could be resolved. By mid-day on January 20, the investor had agreed to the terms of a private placement that would have provided GenVec with gross proceeds of approximately $6.5 million, before fees and expenses. In the private placement, GenVec would have issued 6,500 shares of a newly created series of convertible preferred stock at $1,000 per share (and convertible into GenVec common stock at an initial conversion price of $5.00 per share) and warrants to purchase up to 1,300,000 shares of common stock at an exercise price of $5.00 per share. Assuming the issuance of common stock on conversion of the preferred stock and the full exercise of the warrants, the securities issued in the offering would have represented approximately 53% of the outstanding shares of common stock of GenVec.

Prior to executing documents with respect to the private placement, on the afternoon of January 20, 2017, Mr. Nimrodi delivered to Mr. Swirsky a non-binding proposal from Intrexon to acquire 100% of the issued and outstanding stock of GenVec at a price of $6.00 per share delivered in the form of Intrexon common stock plus a contingent payment right covering the next milestone to be received under the NVS License Agreement. Upon receiving this offer, Mr. Swirsky convened a telephonic meeting of the available members of the GenVec board of directors. The directors available for the meeting agreed that Mr. Swirsky should negotiate with Intrexon to improve the terms of the offer while maintaining the possibility of completing the financing transaction.

In accordance with the GenVec board of directors’ direction, Mr. Swirsky responded to Intrexon’s offer indicating that the GenVec board of directors would be more likely to approve the transaction at a price of $8.00 per share plus up to $15 million in contingent payments based on the achievement of the milestones under the NVS License Agreement. Mr. Nimrodi responded to Mr. Swirsky stating that Intrexon was willing to increase the offer to a value of $7.00 per share payable in Intrexon common stock, but with no contingent payments. Mr. Swirsky then spoke with Randal Kirk, Chairman and Chief Executive Officer of Intrexon, regarding the potential strategic transaction and reached agreement on the key terms of the offer. Shortly after this discussion, Mr. Nimrodi formally communicated an offer of Intrexon common stock having a value of $7.00 per share of GenVec common stock plus 50% of the milestone payments received under the NVS License Agreement during the next 36 months. Mr. Swirsky responded to Mr. Nimrodi indicating that he thought that the companies should move forward on negotiating transactions documents under those terms and that he would meet with the GenVec board of directors the next morning. Mr. Nimrodi informed Mr. Swirsky that Intrexon wanted to execute a definitive agreement and to announce the transaction prior to the opening of the stock markets on Monday, January 23, 2017.

Mr. Swirsky reached out to the investors in the private placement following discussions with Intrexon to confirm that GenVec did not intend to sign the private placement transaction on January 20, 2017.

On the morning of January 21, 2017, the GenVec board of directors convened to discuss the status of discussions with Intrexon regarding the proposed strategic transaction and parallel discussions with the investors in the proposed financing transaction. The GenVec board of directors discussed the alternatives of a strategic transaction and a financing transaction, and asked Mr. Swirsky to discuss where GenVec stood with its other ongoing business development efforts. Following the discussion, the GenVec board of directors determined that, based on several factors, including the additional dilution to existing GenVec shareholders associated with a financing transaction and the limited prospects of completing an alternative business development transaction in the near-term, it was in the best interests of the GenVec shareholders to continue discussions with Intrexon regarding the potential strategic transaction. In discussing the financing transaction and the substantial dilution that would result, the GenVec board of directors considered the impact of the dilution on the existing stockholders, that the implied price of a share of common stock in the financing was at a lower value than that implied by the offer price in the strategic transaction, and that if there were a strategic transaction in the future,

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then the value paid by any third party would be split among a greater number of shareholders, which would require a greater overall premium to be paid in order to provide the same value to the existing shareholders. The GenVec board of directors also noted that the financing transaction would result in the existing and new shareholders having continued exposure to the uncertain outcome of GenVec’s research and development activities, while at the same time providing less of a benefit to existing shareholders from any ultimate upside of those activities. Also in attendance at this meeting were representatives of Hogan Lovells who discussed with the GenVec board of directors its legal obligations associated with a strategic transaction with Intrexon. The GenVec board of directors then discussed engaging a financial advisor to assess the proposed transaction with Intrexon, in order to deliver to GenVec an opinion as to the financial fairness of the transaction. Following this discussion, the GenVec board of directors formally approved resolutions to form a special committee, comprised of Stefan D. Loren, Ph.D., Marc R. Schneebaum and Michael Richman, authorized to consider the terms of and negotiate the Intrexon transaction. The special committee was created in the interest of efficiency so that the full board would not always be required to convene in connection with the negotiation of the Intrexon transaction. Additionally, the GenVec board of directors formally authorized Mr. Swirsky to engage Roth as GenVec’s financial advisor to provide a fairness opinion with respect to the transaction. Mr. Swirsky then left the meeting so that the GenVec board of directors could meet in an executive session. During the executive session, the representatives of Hogan Lovells advised the GenVec board of directors of its considerations in connection with a potential conflict of interest if Intrexon were to offer the executives of GenVec employment with Intrexon prior to the closing of the transaction with Intrexon.

That afternoon, Mr. Swirsky contacted representatives of Roth to discuss whether Roth would prepare an analysis and opinion for the GenVec board of directors as to the fairness, from a financial point of view, of the per share merger consideration to be received by the holders of GenVec common stock in the merger based on the proposed terms of the agreement and its analysis thereof. Roth agreed to perform such analysis and to render an opinion to the GenVec board of director with respect to the fairness, from a financial point of view, of the per share merger consideration to be received by the holders of GenVec common stock in the merger.

In the afternoon on January 21, 2017, Mr. Swirsky contacted the GenVec board of directors to update them on the proposed key terms of the transaction and to inform them that he expected to receive a draft merger agreement from Intrexon that evening. Mr. Swirsky also scheduled calls with the special committee of the GenVec board of directors and with the entire board of directors at 10:00 a.m., and 10:00 p.m., respectively, on January 22, to discuss the status of the transaction.

Later that evening of January 21, 2017, Mr. Ulrich sent Hogan Lovells a draft of the merger agreement, which included a number of open discussion items. Intrexon indicated that it planned on sharing a draft contingent payment rights agreement the next day. During the evening of January 21, 2017, GenVec and Hogan Lovells began reviewing the merger agreement and preparing disclosure schedules.

On the morning of January 22, 2017, the strategic transaction committee of the GenVec board of directors met via telephone conference, with representatives of Hogan Lovells in attendance, to discuss the material issues in the merger agreement. Representatives of Hogan Lovells summarized the material terms of the merger agreement, including the proposal by Intrexon that the purchase price of the GenVec common stock be determined using an exchange ratio calculated based on the 20-day volume weighted average price, referred to herein as VWAP, of Intrexon’s common stock as of the close of business on January 20, 2017 (which valued each share of Intrexon common stock at $24.716 per share), and that the exchange ratio would be fixed and therefore the value to be received by GenVec’s shareholder would “float” based on the value of a share of Intrexon common stock. The strategic transaction committee then discussed with counsel those terms, as well as others, including termination rights, the ability of GenVec to entertain offers from third parties following signing, circumstances under which GenVec would be required to pay the expenses of Intrexon and the importance of ensuring the certainty of the purchase price and the closing of the merger. Of additional discussion among the committee members were provisions with respect to employment matters, treatment of outstanding options and warrants and GenVec’s ability to operate its business between signing and closing. The transaction committee

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then provided guidance to GenVec’s management and outside counsel regarding the material outstanding terms, particularly pricing, termination rights, termination fee, expense reimbursement and closing certainty provisions.

In accordance with the directives from the strategic transaction committee, representatives of Hogan Lovells held a telephone conference with Mr. Lehr, Mr. Ulrich and representatives of Thompson Hine LLP, referred to herein as Thompson Hine, outside counsel to Intrexon, to discuss the material open issues in the merger agreement from GenVec’s point of view. Specifically, representatives of Hogan Lovells proposed a “go-shop” provision that would have provided GenVec the ability to seek alternative proposals after signing of the transaction with a termination fee of $250,000, an exchange ratio with a “floor” of $6.50 per share using the closing price of Intrexon’s common stock on January 21, 2017, a termination fee of $450,000 and no repayment of expenses in the event that the shareholders of GenVec do not approve the merger.

During the afternoon of January 22, 2017, GenVec received a draft of the proposed contingent payment rights agreement as well as a draft press release with respect to the merger.

Mr. Lehr and representatives of Hogan Lovells had further conversations with respect to the terms of the transaction throughout the afternoon, and in the evening the Intrexon team communicated revised terms, confirming that Intrexon was willing to discuss decreasing the termination fee from $1.25 million to $1 million, but was not amenable to a “go-shop” provision or a price floor, and that it required an expense reimbursement of up to $750,000 in the event of termination in certain circumstances, including if the GenVec shareholders did not approve the merger.

Later in the evening of January 22, 2017, representatives of Hogan Lovells held a telephone conference with the entire GenVec board of directors to further consider the proposed transaction and to provide feedback from the telephone calls with Intrexon. Representatives of Hogan Lovells reported on the discussion with Intrexon and its counsel and the revised terms that Intrexon had communicated. The GenVec board of directors discussed the pricing of the transaction, and particularly the relative importance of certainty around the price per share under the merger agreement. The GenVec board of directors agreed that a fixed price per share would provide GenVec’s shareholders with greater certainty regarding the payments under the merger agreement, but that it would be reasonable to accept a floating exchange ratio, particularly in light of the view of the GenVec board of directors of the potential benefits from a combination of the two companies. The GenVec board of directors also discussed the historical volatility of both Intrexon and GenVec’s common stock and concluded that it would be willing to determine the value of Intrexon common stock based on a shorter VWAP period, such as a five-day period ending on the day prior to signing the merger agreement.

The GenVec board of directors further discussed the termination provisions, concluding that the strategic value of the combination made it such that a go-shop provision was not necessary, but that it was still appropriate to have the reasonable ability to terminate the merger agreement if GenVec received a “superior proposal,” including by ensuring that any termination fee was reasonable. The GenVec board of directors agreed that a termination fee of $1 million or more was unacceptable and emphasized that it must be decreased in order for the GenVec board of directors to approve and recommend the transaction. The GenVec board of directors then discussed the proposals regarding the CPRs and that a structure using cash for the payment of those rights would make it difficult for the transaction to qualify as a tax free reorganization. Prior to adjourning the meeting, the directors agreed to meet again in the evening of January 23, 2017 to discuss the status of the transaction after further negotiations.

In the morning on January 23, 2017, Hogan Lovells delivered revised drafts of the merger agreement and the contingent payment rights agreement and initial drafts of ancillary documents. The revised draft of the merger agreement proposed a price based on the five-day VWAP of Intrexon’s common stock, provisions relating to employee benefit arrangements, a termination fee of $450,000, an expense reimbursement for termination for GenVec’s breach of its covenants of up to $250,000 (but not on a no-vote by GenVec’s shareholders), and carve-outs from the material adverse effect definition for certain events with respect to GenVec’s programs that are outside of GenVec’s control.

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In the evening of January 23, 2017, Thompson Hine sent further revised drafts of the merger agreement and related documents to Hogan Lovells. After reviewing the material revisions to the documents, representatives of Hogan Lovells and Thompson Hine, Mr. Lehr and Mr. Ulrich met via teleconference to discuss the open items in the agreements. During the call, the parties agreed to setting the exchange ratio based on the five-day VWAP, which would result in a fixed exchange ratio of 0.297 of a share of Intrexon common stock, plus a CPR. However, the parties were unable to agree with respect to certain provisions relating to termination of the merger agreement, including an associated break-up fee and expense reimbursement, and left the call to meet with their respective business teams.

Following the call with the legal teams, the GenVec board of directors convened a meeting to discuss the status of the transaction. Representatives of Hogan Lovells updated the GenVec board of directors on the agreed pricing and the differences between the parties with respect to termination provisions. The GenVec board of directors discussed the various termination provisions and agreed that the representatives of Hogan Lovells should continue discussions with the Intrexon representatives, including to limit GenVec’s exposure in the event that the merger is not consummated. After providing specific guidance to the Hogan Lovells team, the GenVec board of directors scheduled a call at 6:30 a.m. on January 24, 2017 and Mr. Swirsky informed the members of the GenVec board of directors that representatives of Roth had indicated that they would be available at that time to present their fairness opinion, if requested.

Later that evening, after further discussions with Intrexon’s legal representatives, Hogan Lovells sent further revised drafts of the merger agreement and related documents to Thompson Hine. The draft of the merger agreement proposed a termination fee of $550,000, an expense reimbursement of up to $400,000 for termination for breach by GenVec and an additional $200,000 expense reimbursement if GenVec willfully breaches the non-solicitation provision. The draft did not include an expense reimbursement in the event that the GenVec shareholders did not approve the transaction. And, it provided that the GenVec board of directors could, in certain circumstances, terminate the merger agreement if it had a change of recommendation. After further discussions through the night, Intrexon agreed to the material terms of the draft provided by Hogan Lovells.

That same night, Mr. Swirsky and Dr. Stefan Loren, a director of GenVec, engaged in discussions with Mr. Lehr and Mr. Rick L. Sterling, Intrexon’s Chief Financial Officer, regarding certain diligence matters with respect to Intrexon.

Throughout the night of January 23 and into the early morning of January 24, the parties continued finalizing the documents for the transaction.

On the morning of January 24, 2017, the GenVec board of directors met, with representatives of Roth and Hogan Lovells in attendance at various points in the meeting, to consider approving the merger, pending results of the latest updates from its advisors regarding the negotiations of the material terms of the merger agreement. Representatives of Hogan Lovells updated the GenVec board of directors with respect to the current status of certain terms of the merger agreement that remained open as of the prior GenVec board of directors meeting, including that Intrexon had made material concessions with respect to termination fees. Representatives of Hogan Lovells then answered questions from the GenVec board of directors regarding the terms of the merger agreement and summarized the material terms of the other documents included in the transactions contemplated by the merger agreement.

Roth then joined the meeting and reviewed with the GenVec board of directors its financial analysis of the merger consideration and rendered an oral opinion, confirmed by the delivery of a written opinion, dated January 24, 2017, to the GenVec board of directors to the effect that, as of such date and based on and subject to various assumptions made, procedures followed, matters considered and limitations and qualifications on the review undertaken, the merger consideration to be received by the holders of GenVec common stock pursuant to the merger agreement and contingent payment rights agreement was fair, from a financial point of view, to such holders.

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Following the foregoing discussion, representatives of Hogan Lovells reviewed proposed resolutions approving the merger and the other transactions contemplated by the merger agreement. In addition to approving the execution, delivery and performance of the merger agreement, the resolutions contained, among other matters, resolutions approving the contingent payment rights agreement and other ancillary matters. At this point, Mr. Swirsky left the meeting, so that the GenVec board of directors could meet in an executive session. During the executive session, the GenVec board of directors considered that, as a result of the merger, Mr. Swirsky will be entitled to certain benefits, including acceleration of options held by Mr. Swirsky and a potential 18-month severance package if he experiences a qualifying termination of employment in the two-year period following the merger. The GenVec board of directors acknowledged that Mr. Swirsky’s interests may be viewed as different than the other shareholders, but the GenVec board of directors agreed that Mr. Swirsky had not acted inconsistent with the best interests of the shareholders taken as a whole. Mr. Swirsky then rejoined the meeting.

The GenVec board of directors, following a review of the proposed resolutions, unanimously adopted resolutions and, among other things, (i) determined that the merger agreement, the merger, and the other transactions contemplated by the merger agreement were fair and advisable to, and in the best interests of, GenVec and its shareholders, (ii) approved the execution, delivery and performance by GenVec of the merger agreement and the consummation of the merger and the other transactions contemplated by the merger agreement, (iii) approved the contingent payment rights agreement and (iv) resolved to recommend that the shareholders of GenVec adopt and approve the merger agreement.

On the morning of January 24, 2017, GenVec, Intrexon and Merger Sub signed the merger agreement and GenVec and Intrexon issued a joint press release announcing the merger prior to the opening of regular trading on the NASDAQ Capital Market.

Recommendation of the GenVec board of directors; GenVec’s reasons for the merger

The GenVec board of directors, at a meeting held on January 24, 2017, unanimously:

In evaluating the merger, the GenVec board of directors consulted with GenVec’s senior management and outside legal advisors, considered the limited available alternatives to enhance GenVec’s competitive position in the pharmaceutical industry and to increase shareholder value and considered a number of factors that it believed supported its decision to enter into the merger agreement and consummate the merger. These discussions included executive sessions with outside legal advisors without management and financial advisors present.

In that process, the GenVec board of directors considered, among other things, the following factors (not in any relative order of importance) as generally supporting its decision to approve the merger agreement and recommend that GenVec shareholders approve the merger proposal:

Financial Considerations

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Strategic Considerations

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Transaction Terms and Other Considerations

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In the course of its deliberation, the GenVec board of directors also considered the following risk factors relating to entering into the merger agreement and consummating the merger and the other transactions contemplated thereby, but determined that the benefits of the transactions substantially outweighed such risks:

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In addition, the GenVec board of directors was aware of and considered the interests of its directors and executive officers that are different from, or in addition to, the interests of GenVec shareholders generally, including the treatment in the merger of GenVec stock options and other equity awards described in the section entitled “Interests of GenVec’s directors and executive officers in the merger” and Intrexon’s agreement to indemnify GenVec directors and officers against certain claims and liabilities.

The foregoing discussion of information and factors considered by the GenVec board of directors is not exhaustive, but includes the material factors considered by the GenVec board of directors, including factors that support the merger and the other transactions contemplated by the merger agreement as well as those against them. In view of the wide variety of factors considered by the GenVec board of directors in connection with its evaluation of the merger and the other transactions and the complexity of these matters, the GenVec board of directors did not consider it practical to, nor did it attempt to, quantify, rank or otherwise assign relative weights to the specific factors that it considered in reaching its decision. Rather, the GenVec board of directors based its recommendation on the totality of the information presented to and considered by it. The GenVec board of directors evaluated the factors described above with the assistance of GenVec’s senior management and legal advisors. In considering the factors described above, individual members of the GenVec board of directors may have given different weights to other or different factors.

This explanation of the factors considered by the GenVec board of directors is in part forward-looking in nature, and, therefore, should be read in light of the factors discussed in the sections of this proxy statement/prospectus entitled “Cautionary statement on forward-looking statements” and “Risk factors.”

After careful consideration, the GenVec board of directors unanimously determined that the merger agreement, the merger and the other transactions contemplated by the merger agreement are fair and advisable to, and in the best interests of, GenVec and its shareholders, and approved the execution, delivery and performance by GenVec of the merger agreement and the consummation of the merger and the other transactions contemplated by the merger agreement.

Accordingly, the GenVec board of directors unanimously recommends that GenVec shareholders vote “ FOR ” the merger proposal, “ FOR ” the merger-related compensation proposal and “ FOR ” the adjournment proposal.

Opinion of Roth Capital Partners as GenVec’s financial advisor

The GenVec board of directors retained Roth on January 21, 2017 to render an opinion as to the fairness, from a financial point of view, to the holders of GenVec common stock of the consideration to be received by such holders in the merger.

On January 24, 2017, Roth rendered its oral opinion to the GenVec board of directors (which was subsequently confirmed in writing by delivery of Roth’s written opinion dated the same date) to the effect that, based upon and subject to the assumptions, factors, qualifications and limitations set forth in the written opinion described herein, as of January 24, 2017, the consideration to be received by the holders of GenVec common stock in the merger was fair, from a financial point of view, to such holders.

Roth’s opinion was prepared for the information of the GenVec board of directors for its use in connection with its consideration of the merger and only addressed the fairness, from a financial point of view, to the holders of GenVec common stock of the consideration to be received by such holders in the merger. Roth was not requested to opine as to, and Roth’s opinion does not address, the relative merits of the merger or any alternatives to the merger, GenVec’s underlying decision to proceed with or effect the merger, or any other aspect of the merger. Roth’s opinion does not address the fairness of the merger to the holders of any other class of securities, creditors or other constituencies of GenVec and is not a valuation of GenVec or its assets or any class of its securities. Roth did not express an opinion about the fairness of the amount or nature of any compensation payable or to be paid to any of the officers, directors or employees, of GenVec, whether or not relative to the merger.

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The summary of Roth’s opinion in this proxy statement/prospectus is qualified in its entirety by reference to the full text of its written opinion, which is included as Annex E to this proxy statement/prospectus and sets forth the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered by Roth in preparing its opinion. Roth’s opinion was prepared for the information of the GenVec board of directors for its use in connection with its consideration of the merger. Neither Roth’s written opinion nor the summary of its opinion and the related analyses set forth in this proxy statement/prospectus are intended to be, and they do not constitute, advice or a recommendation to any shareholder as to how such shareholder should act or vote with respect to any matter relating to the merger or any other matter.

In connection with rendering the opinion described above and performing its related financial analyses, Roth, among other things:

In arriving at its opinion, Roth relied upon and assumed, without independent verification, the accuracy and completeness of all information that was publicly available or was furnished, or otherwise made available to Roth or discussed with or reviewed by or for Roth, and further assumed that the financial information provided to Roth had been prepared on a reasonable basis in accordance with industry practice, and that management of GenVec was not aware of any information or facts that would make any information provided to Roth incomplete or misleading.

With respect to the financial forecasts, estimates and other forward-looking information reviewed by Roth, Roth assumed that such information had been reasonably prepared based on assumptions reflecting the best currently available estimates and judgments of GenVec’s management as to the expected future results of operations and financial condition of GenVec. Roth was not engaged to assess the achievability of any such financial forecasts, estimates or forward-looking information or the assumptions on which they were based, and Roth expressed no opinion as to such information or assumptions. In addition, Roth did not assume any responsibility for, and did not perform, any appraisals or valuation of any specific assets or liabilities (fixed, contingent or other) of GenVec, nor was Roth furnished or provided with any such appraisals or valuations. Without limiting the generality of the foregoing, Roth was not engaged to perform, and did not undertake, any independent analysis of any pending or threatened litigation, regulatory action, possible unasserted claims or other contingent liabilities, to which GenVec or any of their respective affiliates is a party or may be subject, and at the direction of the GenVec board of directors and with its consent, Roth’s opinion made no assumption concerning, and did not consider, the possible assertion of claims, outcomes or damages arising out of any such matters.

Roth relied upon and assumed, without independent verification, that the representations and warranties of all parties set forth in the merger agreement and all related documents and instruments that are referred to therein are

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true and correct, that each party will fully and timely perform all of the covenants and agreements required to be performed by such party, that the merger will be consummated pursuant to the terms of the merger agreement, without amendment, and that all conditions to the consummation of the merger will be satisfied without waiver thereof. Roth further assumed that the merger agreement was in all material respects identical to the draft of the merger agreement provided to Roth. Finally, Roth also assumed that all the necessary regulatory approvals and consents required for the merger, including the approval of the shareholders of GenVec, will be obtained in a manner that will not adversely affect GenVec or the contemplated benefits of the merger.

In connection with its opinion, Roth assumed and relied upon, without independent verification, the accuracy and completeness of all of the financial, legal, regulatory, tax, accounting and other information provided to, discussed with or reviewed by it. Roth’s opinion does not address any legal, regulatory, tax or accounting issues. Roth’s fairness opinion was approved by its fairness committee prior to delivering it to GenVec.

Roth’s opinion is necessarily based upon the information available to Roth and facts and circumstances as they existed and were subject to evaluation as of January 24, 2017, which is the date of the Roth opinion. Although events occurring after the date of the Roth opinion could materially affect the assumptions used in preparing the opinion, Roth does not have any obligation to update, revise or reaffirm its opinion and Roth expressly disclaims any responsibility to do so. Roth did not express any opinion as to the price at which shares of Intrexon common stock may trade following announcement of the merger or at any future time.

The consideration to be paid by GenVec in the merger was determined through negotiations between GenVec and Intrexon. Roth did not provide advice to the GenVec board of directors during these negotiations, and the decision to enter into the merger agreement was solely that of the GenVec board of directors. Roth’s opinion and its presentation to the GenVec board of directors was one of many factors taken into consideration by the GenVec board of directors in connection with its consideration of the merger. Consequently, the analyses as described herein should not be viewed as determinative of the opinion of the GenVec board of directors with respect to the consideration to be received by holders of GenVec common stock in the merger or of whether the GenVec board of directors would have been willing to agree to different consideration.

The following is a summary of the material financial analyses performed by Roth in connection with the preparation of its fairness opinion, which opinion was rendered orally to the GenVec board of directors (and subsequently confirmed in writing by delivery of Roth’s written opinion dated the same date) on January 24, 2017. The preparation of analyses and a fairness opinion is a complex analytic process involving various determinations as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances and, therefore, such an opinion is not readily susceptible to summary description and this summary does not purport to be a complete description of the analyses performed by Roth or the delivery of Roth’s opinion to the GenVec board of directors.

In furnishing its opinion, Roth did not attempt to combine the analyses described herein into one composite valuation range, nor did Roth assign any quantitative weight to any of the analyses or the other factors considered. Furthermore, in arriving at its opinion, Roth did not attribute any particular weight to any analysis or factor considered by it, but rather made qualitative judgments as to the significance and relevance of each analysis and factor in light of one another. Accordingly, Roth has stated that it believes that its analyses must be considered as a whole and that considering any portion of its analyses, without considering all of the analyses, could create a misleading or incomplete view of the process underlying its opinion or the conclusions to be drawn therefrom.

This summary includes information presented in tabular format. In order to fully understand the financial analyses presented by Roth, the tables must be read together with the text of each analysis summary and considered as a whole. The tables alone do not constitute a complete summary of the financial analyses. Considering any portion of such analyses and of the factors considered, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Roth’s opinion.

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In conducting the analysis as to the fairness, from a financial point of view, to the holders of GenVec common stock of the consideration to be received by such holders in the merger, Roth evaluated the equity valuation of GenVec using a number of valuation metrics. Roth also estimated the value of the CPRs to be received by holder of GenVec common stock. Roth then compared the total consideration to be paid by Intrexon to an estimate of the equity value of GenVec.

The results of the application by Roth of each of the valuation methodologies utilized in connection with its fairness opinion are summarized below. The order in which such valuation methodologies are described below does not represent the relative importance or weight given to those methodologies by Roth. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed on January 23, 2017.

Estimated GenVec equity valuation

Roth evaluated the value of GenVec using the following valuation methodologies:

Utilizing these valuation methodologies, Roth estimated equity valuations of GenVec as follows: (i) $4.40 per share to $5.95 per share utilizing the Public Market Valuation; (ii) $7.33 per share to $8.89 per share utilizing the Public Comparable Analysis; (iii) $6.64 per share to $7.00 per share utilizing the Precedent M&A Premiums Analysis; and (iv) $4.64 per share to $4.77 per share utilizing the Discounted Cash Flow Analysis. Roth determined that these estimates resulted in an average equity valuation of $5.75 per share to $6.65 per share.

The results of Roth’s analyses are summarized as follows:

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Notes:  (1)—Equity Value assumes a net cash position of $6.6 million

(2)—Based on fully-diluted share count of 2,344,381.6 shares

(3)—Enterprise value based on the discounted cash flow analysis of the CGF166 and FMD programs; For the purposes of the analysis, GenVec’s assets in the discovery or preclinical development stages were not included in the Discounted Cash Flow Analysis due to the early nature of the programs and lack of strategic partner validation

Public market valuation

Roth noted that since January 1, 2016, the price of GenVec common stock had declined 75%, closing on January 23, 2017 at $4.54, reflecting a public market valuation of $10.3 million.

Utilizing the five-day high ($6.13 on January 17, 2017) and five-day low ($4.54 on January 23, 2017) of the price of GenVec common stock, and assuming a net cash position of $6.6 million, Roth determined that GenVec’s implied enterprise value ranged from $3.7 million to $7.3 million.

Public comparable analysis

Roth reviewed the total enterprise values of publicly traded companies that Roth deemed comparable to GenVec. The comparable companies’ analysis uses data from comparable companies to develop a measure of current value for GenVec. The rationale for using a public comparable analysis is that companies in the same industry with similar operating characteristics should have certain valuation benchmarks in common. The goal of the analysis is to develop a premise for relative value, which when coupled with other valuation approaches, presents a foundation for determining a range of values for a company.

Although none of the following companies is identical to GenVec, Roth selected these companies because they had publicly traded equity securities and were deemed to be similar to GenVec in one or more respects, including their businesses, their size and their operating characteristic. Roth obtained the following publicly available information for each selected company from Biomed Tracker, Capital IQ, and Evaluate Pharma and, as reflected

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below, determined that the selected companies had a median and mean enterprise value of $10.6 million and $14.2 million, respectively: