Prospectus Filed Pursuant to Rule 424(b)(5) (424b5)

Filed pursuant to Rule 424(b)(5)
Registration No. 333-222699

Prospectus Supplement

(To Prospectus dated February 5, 2018)

LOGO

Tetraphase Pharmaceuticals, Inc.

300,000 Shares of Common Stock

Pre-Funded Warrants to Purchase up to 1,830,493 Shares of Common Stock

Common Stock Warrants to Purchase up to 2,130,493 Shares of Common Stock

We are offering to a healthcare focused institutional investor (i) 300,000 shares of our common stock and accompanying common stock warrants to purchase up to an aggregate of 300,000 shares of our common stock and (ii) pre-funded warrants to purchase up to an aggregate of 1,830,493 shares of our common stock and accompanying common stock warrants to purchase up to an aggregate of 1,830,493 shares of common stock. We are also offering the shares of our common stock issuable from time to time upon exercise of the warrants being offered by this prospectus supplement. Each share of common stock and accompanying common stock warrant are being sold together at a combined price of $3.755, and each pre-funded warrant and accompanying common stock warrant are being sold together at a combined price of $3.745.

The shares of common stock and pre-funded warrants, on the one hand, and the accompanying common stock warrants, on the other hand, are immediately separable and will be issued separately, but can only be purchased together in this offering. Each pre-funded warrant will have an exercise price per share of common stock equal to $0.01 and is exercisable at any time after its original issuance until exercised in full. Each common stock warrant will have an exercise price per share of common stock equal to $3.62 and will be immediately exercisable and will expire five years from the date of issuance. The pre-funded warrants and the common stock warrants are referred to collectively as the warrants.

Our common stock is listed on The Nasdaq Global Select Market under the symbol “TTPH.” There is no established trading market for any of the warrants, and we do not expect a market to develop. We do not intend to apply for a listing for any of the warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the warrants will be limited.

The last reported sale price of our common stock on October 29, 2019, was $3.62 per share.

This investment involves risk. See “Risk Factors” beginning on page S-6 and in filings with the U.S. Securities and Exchange Commission that are incorporated by reference into this prospectus supplement.

We have engaged H.C. Wainwright & Co., LLC, or the placement agent, as our exclusive placement agent in connection with this offering. The placement agent has no obligation to buy any of the securities from us or to arrange for the purchase or sale of any specific number or dollar amount of securities. We have agreed to pay the placement agent the placement agent fees set forth in the table below. See “Plan of Distribution” beginning on page S-27 of this prospectus supplement for more information regarding these arrangements.


	Per Share and Accompanying Common Stock Warrant		Per Pre-Funded Warrant and Accompanying Common Stock Warrant		Total
Offering Price	$	3.755	$	3.745	$	7,981,696
Placement Agent Fees(1)	$	0.262	$	0.262	$	560,000
Proceeds, before expenses, to us(2)	$	3.492	$	3.483	$	7,421,696

(1)	In addition, we have agreed to reimburse the placement agent for certain out-of-pocket expenses. See “Plan of Distribution” beginning on page S-27 of this prospectus supplement.

(2)	The amount of the offering proceeds to us presented in this table does not give effect to any exercise of the warrants being issued in this offering.

Delivery of the securities offered hereby is expected to occur on or about November 1, 2019, subject to the satisfaction of certain closing conditions.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

H.C. Wainwright & Co.

The date of this prospectus supplement is October 29, 2019

TABLE OF CONTENTS


Prospectus Supplement

About This Prospectus Supplement		S-ii
Prospectus Supplement Summary		S-1
Risk Factors		S-6
Cautionary Note Regarding Forward-Looking Statements		S-9
Use of Proceeds		S-10
Dividend Policy		S-11
Capitalization		S-12
Dilution		S-14
Description of Securities We Are Offering		S-16
Material U.S. Federal Tax Considerations for Holders of Our Common Stock, Pre-Funded Warrants and Common Stock Warrants		S-20
Plan of Distribution		S-27
Legal Matters		S-28
Experts		S-28
Where You Can Find More Information		S-29
Incorporation by Reference		S-30

Prospectus

	Page
ABOUT THIS PROSPECTUS		1
RISK FACTORS		1
WHERE YOU CAN FIND MORE INFORMATION		1
INCORPORATION BY REFERENCE		3
FORWARD-LOOKING STATEMENTS		4
TETRAPHASE PHARMACEUTICALS, INC.		5
CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES		7
USE OF PROCEEDS		8
DESCRIPTION OF DEBT SECURITIES		8
DESCRIPTION OF CAPITAL STOCK		17
DESCRIPTION OF WARRANTS		21
FORMS OF SECURITIES		22
PLAN OF DISTRIBUTION		24
LEGAL MATTERS		27
EXPERTS		27

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference herein. The second part, the accompanying prospectus, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement and the information contained in the accompanying prospectus or any document incorporated by reference therein filed prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement; provided that if any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

We have not, and the placement agent has not, authorized anyone to provide you with information other than that which is contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus or in any free writing prospectus that we have authorized for use in connection with this offering. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you.

This prospectus supplement and the accompanying prospectus do not constitute an offer to sell, or a solicitation of an offer to purchase, the securities offered by this prospectus supplement and the accompanying prospectus in any jurisdiction to or from any person to whom or from whom it is unlawful to make such offer or solicitation of an offer in such jurisdiction. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and in any free writing prospectus that we have authorized for use in connection with this offering is accurate only as of the date of those respective documents. It is important for you to read and consider all information contained in this prospectus supplement and in the accompanying prospectus, including the documents incorporated by reference herein and therein, in making your investment decision. You should also read and consider the information in the documents to which we have referred you in the sections entitled “Where You Can Find More Information” and “Incorporation by Reference” in this prospectus supplement and in the accompanying prospectus.

We are offering to sell, and seeking offers to buy, our securities only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the accompanying prospectus and the offering of our securities in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of our securities and the distribution of this prospectus supplement and the accompanying prospectus outside the United States. This prospectus supplement and the accompanying prospectus do not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

Unless the context otherwise indicates, all references in this prospectus supplement and the accompanying prospectus to “we,” “us,” “our,” “Tetraphase,” “the Company” and similar designations refer, collectively, to Tetraphase Pharmaceuticals, Inc., a Delaware corporation, and, where appropriate, its consolidated subsidiaries.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary does not contain all of the information that you should consider before investing in our securities. You should read this entire prospectus supplement and the accompanying prospectus carefully, including the financial statements and other information incorporated by reference into this prospectus supplement and the accompanying prospectus, before making an investment decision. In addition, please read the “Risk Factors” section of this prospectus supplement beginning on page S-6 and the risk factors contained in our Quarterly Report on Form 10-Q for the three months ended June 30, 2019.

Overview

We are a biopharmaceutical company using our proprietary chemistry technology to develop and commercialize novel tetracyclines for serious and life-threatening conditions, including bacterial infections caused by many multidrug-resistant, or MDR, bacteria. There is a medical need for new antibiotics as resistance to existing antibiotics increases. Our commercial product, Xerava^TM (eravacycline), a fully synthetic fluorocycline, is an intravenous, or IV, antibiotic that is approved for use as a first-line empiric monotherapy for the treatment of MDR infections, including those found in complicated intra-abdominal infections, or cIAI.

On August 27, 2018, the United States Food and Drug Administration, or FDA, approved Xerava for the treatment of cIAI in adults. Approval of Xerava was based on our IGNITE (Investigating Gram-Negative Infections Treated with Eravacycline) phase 3 program. In the first pivotal phase 3 trial in the IGNITE program in patients with cIAI, twice-daily IV Xerava met the primary endpoint by demonstrating statistical non-inferiority of clinical response compared to ertapenem, a carbapenem and a standard of care treatment for cIAI, and was well-tolerated. We refer to this trial as IGNITE1. In our other pivotal phase 3 clinical trial of Xerava in patients with cIAI, twice-daily IV Xerava met the primary endpoint by demonstrating statistical non-inferiority of clinical response compared to meropenem, another standard of care treatment, and was well-tolerated. We refer to this trial as IGNITE4. In both IGNITE1 and IGNITE4, Xerava achieved high clinical cure rates in patients with poly-microbial infections (Gram-negative, Gram-positive and anaerobic infections), including resistant isolates.

In October 2018, we commenced sales of Xerava in the United States. We are commercializing Xerava in the United States using small, targeted commercial and medical affairs groups to build and promote access to Xerava. As of September 30, 2019, we have approximately 35 sales representatives, five regional business directors, two strategic market access executives and approximately six medical affairs personnel in the field supporting Xerava in the United States. To date, a majority of our sales have occurred in the hospital setting.

On September 20, 2018, based on the results of the IGNITE phase 3 clinical program, the European Commission, or EC, granted marketing authorization for Xerava for the treatment of cIAI in adults in all 28 countries of the European Union, or EU, plus Norway, Iceland and Liechtenstein. In February 2018, we entered into a license agreement with Everest Medicines Limited, or Everest Medicines, which was amended in July 2019, granting Everest Medicines commercialization rights to eravacycline in China and other Asian territories. In June 2018, Everest Medicines submitted an investigational new drug application, or IND, to the National Medical Products Administration (formerly CHINA FDA) for a phase 3 clinical trial of eravacycline in cIAI. Everest Medicines began enrolling patients in this phase 3 clinical trial in the second quarter of 2019.

We believe that the ability of Xerava to cover MDR Gram-negative bacteria, as well as MDR Gram-positive, anaerobic and atypical bacteria, may enable Xerava to become the drug of choice for first-line empiric treatment of patients with cIAI. Xerava has demonstrated the ability to cover a wide variety of MDR Gram-negative bacteria, including MDR Klebsiella pneumoniae and MDR Acinetobacter in in vitro studies. Multidrug-resistant Klebsiella pneumoniae is one of the carbapenem-resistant Enterobacteriaceae (or CREs) listed as an

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urgent threat and MDR Acinetobacter is listed as a serious threat by the Centers for Disease Control and Prevention in a September 2013 report. They are also listed as “Priority 1; Critical Pathogens” in the World Health Organization’s priority pathogens list for R&D, published in February 2017. CREs were a confirmed area of great concern by the World Health Organization in an April 2014 global surveillance report. Gram-negative bacteria that are resistant to multiple available antibiotics are increasingly common and a growing threat to public health.

In addition to Xerava, we have also developed other fluorocycline antibiotic compounds, TP-6076 and TP-271, and a tetracycline for the treatment of acute myeloid leukemia, TP-2846. We developed TP-6076, a fully synthetic fluorocycline derivative, as a lead candidate under our second-generation program to target unmet medical needs, including MDR Gram-negative bacteria such as carbapenem-resistant Enterobacteriaceae and carbapenem-resistant Acinetobacter baumanii. To date, we have completed phase 1 single-ascending and multiple-ascending dose studies evaluating the safety, tolerability and pharmacokinetics of IV TP-6076 in healthy volunteers. We also conducted a Phase 1 study to assess the bronchopulmonary disposition, pharmacokinetics, and safety of TP-6076 in healthy volunteers. TP-271 is a fully synthetic fluorocycline that we developed for respiratory disease caused by bacterial biothreat and antibiotic-resistant public health pathogens, as well as bacterial pathogens associated with community-acquired pneumonia. To date, we have completed single- and multiple-ascending dose trials for the IV and oral formulations of TP-271. We have recently initiated pre-clinical toxicology studies in TP-2846 and intend to file an IND with the FDA for TP-2846. We are seeking to out-license each of these product candidates and do not plan to continue the development of these product candidates by ourselves.

On June 12, 2019, we announced a restructuring of our organization, including a 20% reduction in headcount, designed to focus our cash resources on commercializing Xerava primarily in the hospital setting. This reorganization included the elimination of our internal research function and an exploration of out-licensing opportunities for all of our pipeline of early-stage antibiotics and oncology product candidates. The reduction in headcount did not reduce any headcount in our commercial organization. Following the restructuring, over 50% of our full-time employees are commercial and medical affairs personnel.

We commenced business operations in July 2006. Our operations to date have been limited to organizing and staffing our company, business planning, raising capital, acquiring and developing our proprietary chemistry technology, identifying potential product candidates, undertaking preclinical studies and clinical trials of our product candidates and initiating commercial sales of Xerava. Prior to October 2018, when we commenced sales of Xerava in the United States, we had not generated any product revenues.

Additional Financial Information

We have not yet completed our financial statements for the period ended September 30, 2019, but we currently estimate (i) that net sales of Xerava were between approximately $1.0 million and $1.1 million for the three months ended September 30, 2019 and (ii) that our cash and cash equivalents as of September 30, 2019 were approximately $24.5 million. Our estimates of net sales of Xerava and our cash and cash equivalents as of September 30, 2019 have been prepared by management in good faith based upon internal reporting and expectations. However, because the financial statements for the period ended September 30, 2019 have not yet been finalized, these estimates are preliminary, are subject to change and may be revised as a result of management’s further review of our financial results for the period ended September 30, 2019. As a result, there can be no assurance that the final results for this period will not differ materially from these estimates.

We believe, based on our current operating plan and prior to the receipt of any proceeds from this offering, that our existing cash and cash equivalents and our projected revenues from sales of Xerava will be sufficient to fund our operations into the second quarter of 2020, and that with the proceeds of this offering, will be sufficient to

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fund our operations into the third quarter of 2020. In either case, we will be required to obtain further funding through public or private equity offerings, debt financings, collaborations and licensing arrangements or other sources to fund our operations beyond such time. In light of our limited cash resources, we may also determine to explore strategic alternatives to maximize stockholder value, including the potential sale or merger of us or our assets.

We have based our projections of operating capital requirements and revenues on assumptions that may prove to be incorrect, and we may use all of our available capital resources sooner than we expect. However, because of the numerous risks and uncertainties associated with the commercialization of pharmaceutical products such as Xerava, our estimates of our operating capital requirements may be incorrect. If we are unable to raise capital when needed or if our product revenue does not meet our current projections, or if we determine to explore strategic alternatives but are unable to consummate such a transaction or transactions on a timely basis or at all, we could be forced to significantly scale back or discontinue the commercialization of Xerava and reduce other expenditures, seek collaborators at an earlier stage than otherwise would be desirable or on terms that are less favorable than might otherwise be available, and relinquish or license, potentially on unfavorable terms, our rights to Xerava and our other product candidates. In addition, in such circumstance, we would consider seeking protection under the bankruptcy laws in order to continue to pursue potential transactions and conduct a wind-down of our company. If we decide to seek protection under the bankruptcy laws, we would expect that we would file for bankruptcy at a time that is significantly earlier than when we would otherwise exhaust our cash resources.

Our Corporate Information

We were incorporated under the laws of the State of Delaware on July 7, 2006. Our principal executive offices are located at 480 Arsenal Way, Watertown, Massachusetts 02472, and our telephone number is (617) 715-3600. Our website address is www.tphase.com. The information contained or accessible through our website is not incorporated by reference into, and is not considered a part of, this prospectus supplement. Information found on, or accessible through, our website is not a part of, and is not incorporated into, this prospectus supplement and the accompanying prospectus, and you should not consider it part of this prospectus supplement and the accompanying prospectus. Our website address is included in this document as an inactive textual reference only.

The trademarks, trade names and service marks appearing in this prospectus supplement are the property of their respective owners.

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The Offering

Common stock offered by us pursuant to this prospectus supplement

300,000 shares of common stock. Each share of common stock and accompanying common stock warrant are being sold together at a combined price of $3.755.

This prospect supplement also relates to the offering of shares of our common stock issuable upon exercise of the warrants, as discussed below.

Pre-funded warrants offered by us pursuant to this prospectus supplement

Pre-funded warrants to purchase up to an aggregate of 1,830,439 shares of common stock. We are offering the pre-funded warrants to an institutional investor whose purchase of shares of common stock in this offering would otherwise result in the purchaser, together with its affiliates and certain related parties, beneficially owning more than 4.99% (or, at the election of the purchaser, 9.99%) of our outstanding common stock immediately following the closing of this offering. Each pre-funded warrant is exercisable for one share of our common stock. Each pre-funded warrant and accompanying common stock warrant are being sold together at a combined price of $3.745. Each pre-funded warrant will have an exercise price per share of common stock of $0.01, and will be immediately exercisable and may be exercised at any time until exercised in full.

This prospectus supplement also relates to the shares of common stock issuable upon exercise of any pre-funded warrants sold in this offering.

Common stock warrants offered by us pursuant to this prospectus supplement

Common stock warrants to purchase up to an aggregate of 2,130,493 shares of common stock. Each common stock warrant is exercisable for one share of our common stock. Each common stock warrant will have an exercise price per share of common stock of $3.62, will be immediately exercisable and will expire on the fifth anniversary of its date of issuance.

This prospectus supplement also relates to the offering of shares of our common stock issuable upon exercise of the common stock warrants.

Common stock to be outstanding after this offering

3,015,824 shares of common stock, assuming no exercise of any warrants included in this offering.

Use of proceeds

We intend to use the net proceeds from this offering for the commercialization of Xerava, as well as for working capital and other general corporate purposes. See “Use of Proceeds” on page S-10 of this prospectus supplement for more information.

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Risk factors

See “Risk Factors” beginning on page S-6 and the other information included in, or incorporated by reference into, this prospectus supplement and the accompanying prospectus for a discussion of certain factors you should carefully consider before deciding to invest in our securities.

Nasdaq Global Select Market symbol

The number of shares of our common stock to be outstanding after this offering is based on 2,715,824 shares of our common stock issued and outstanding as of September 30, 2019 and excludes:

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20,718 shares of our common stock issuable upon the exercise of warrants outstanding as of September 30, 2019, at a weighted-average exercise price of $43.44 per share;

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269,689 shares of our common stock issuable upon the exercise of stock options outstanding as of September 30, 2019, at a weighted-average exercise price of $244.04 per share;

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141,716 shares of our common stock issuable upon the vesting of restricted stock units outstanding as of September 30, 2019;

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119,217 and 15,000 additional shares of our common stock available for future issuance, as of September 30, 2019, under our 2013 stock incentive plan and our 2014 employee stock purchase plan, as amended, respectively; and

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11,152,678 shares of common stock available for sale as of September 30, 2019 under our sales agreement in respect of our “at-the-market” program (based on an aggregate of $40.4 million of common stock available for sale under the sales agreement, as amended, and assuming sales at a price of $3.62 per share, which was the closing price of our common stock on The Nasdaq Global Select Market on October 29, 2019).

Except as otherwise noted, all information in this prospectus supplement assumes:

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no exercise of the outstanding stock options or warrants and no vesting of the restricted stock units described above; and

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a one-for-20 reverse stock split of our common stock split effected on September 26, 2019.

In addition, unless otherwise indicated, all information in this prospectus supplement assumes no exercise of the warrants issued and sold in this offering.

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RISK FACTORS

Investing in our securities involves a high degree of risk. Before investing in our securities, you should carefully consider the risks and uncertainties described below and in Part II, Item IA “Risk Factors” of our most recent quarterly report on Form 10-Q filed with the SEC on August 8, 2019, together with the other information contained in this prospectus supplement, the accompanying prospectus and in the documents incorporated by reference herein and therein and any free writing prospectus we may authorize for use in connection with this offering. If any of these risks occur, our business, financial condition, results of operations and future growth prospects could be materially and adversely affected. In these circumstances, the market price of our common stock could decline, and you may lose all or part of your investment.

Risks Related to This Offering

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of the net proceeds from this offering and could spend the proceeds in ways that do not improve our results of operations or enhance the value of our common stock. The failure by our management to apply these funds effectively could result in financial losses, and these financial losses could have a material adverse effect on our business, cause the price of our common stock to decline and delay the development of our product candidates. We may invest the net proceeds from this offering, pending their use, in a manner that does not produce income or that loses value.

If you purchase securities in this offering, you will suffer immediate dilution in the book value of your investment.

The offering prices of (i) our common stock and the accompanying common stock warrants and (ii) the pre-funded warrants and accompanying common stock warrants, are each substantially higher than the pro forma as adjusted net tangible book value per share of our common stock. Therefore, if you purchase securities in this offering, you will pay an effective price per share that substantially exceeds our pro forma as adjusted net tangible book value per share after giving effect to this offering. Based on an offering price of $3.755 per share of common stock and accompanying common stock warrant and assuming no exercise of the common stock warrants included in this offering, that no value is attributed to such warrants and that such warrants are classified and accounted for as equity, you will experience immediate dilution of $(10.265) per share, representing the difference between the offering price and our pro forma as adjusted net tangible book value per share after giving effect to this offering. In addition, there can be no assurance that any warrants issued in this offering will be classified and accounted for as equity. Furthermore, if any of our outstanding options or warrants are exercised at prices below the offering price, we grant additional options or other awards under our equity incentive plans or issue additional warrants, the warrants issued in this offering are accounted for as liabilities or we issue additional shares of common stock in the future, you may experience further dilution of your investment. See the section entitled “Dilution” below for a more detailed illustration of the dilution you would incur if you participate in this offering.

The price of our common stock may be volatile and fluctuate substantially, which could result in substantial losses for purchasers of our common stock in this offering.

Our stock price may be volatile. The stock market in general and the market for smaller pharmaceutical and biotechnology companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. For example, our stock traded within a range of a high price of $1,058.00 per share and a low price of $3.62 per share during the period beginning March 20, 2013, our first day of trading on the Nasdaq Global Select Market, through October 29, 2019. As a result of this volatility, you may not be able to sell your common stock at or above the offering price. The market price for our common stock may be influenced by many factors, including:

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revenues related to Xerava;

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the filing and approval of marketing applications for our product candidates by future collaborators;

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the timing and results of clinical trials of any product candidates that we license to third parties;

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regulatory actions by the FDA or equivalent authorities in foreign jurisdictions with respect to Xerava and any product candidate that we license to a third party;

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failure or discontinuation of any development programs of our future collaborators;

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the success of existing or new competitive products or technologies;

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results of clinical trials of product candidates of our competitors;

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regulatory or legal developments in the United States and other countries;

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developments or disputes concerning patent applications, issued patents or other proprietary rights;

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the recruitment or departure of key personnel;

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the results of our efforts to out-license our product candidates;

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actual or anticipated changes in estimates as to financial results, development timelines or recommendations by securities analysts;

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announcement or expectation of additional financing efforts or licensing or other strategic transactions;

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sales of our common stock by us, our insiders or other stockholders;

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variations in our financial results or those of companies that are perceived to be similar to us;

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changes in estimates or recommendations by securities analysts, if any, that cover our stock;

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changes in the structure of healthcare payment systems;

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market conditions in the pharmaceutical and biotechnology sectors;

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general economic, industry and market conditions; and

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the other factors described in this “Risk Factors” section and in Part II, Item 1A “Risk Factors” of our most recent quarterly report on Form 10-Q filed with the SEC on August 8, 2019.

There is no public market for the warrants to purchase common stock being offered by us in this offering.

There is no established public trading market for the warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to apply to list the warrants on any securities exchange or other nationally recognized trading system, including The Nasdaq Global Select Market. Without an active trading market, the liquidity of the warrants will be limited.

Holders of warrants purchased in this offering will have no rights as common stockholders until such holders exercise their warrants and acquire our common stock.

Until holders of warrants acquire shares of our common stock upon exercise of the warrants, such holders will have no rights with respect to the shares of our common stock underlying such warrants. Upon exercise of the warrants, the holders thereof will be entitled to exercise the rights of common stockholders only as to matters for which the record date occurs after the exercise date.

The warrants are speculative in nature.

The warrants do not confer any rights of common stock ownership on their holders, such as voting rights or the right to receive dividends, but rather merely represent the right to acquire shares of common stock at a fixed price for a limited period of time. Specifically, commencing on the date of issuance, holders of (i) the common stock warrants may exercise their right to acquire the common stock subject to such warrants and pay an exercise price per share equal to $3.62, subject to certain adjustments, prior to the fifth anniversary of the date of issuance, at which time they will be automatically exercised on a cashless basis, and (ii) the pre-funded warrants may exercise their right to acquire the common stock subject to such warrants and pay an exercise price per share equal to $0.01, subject to certain adjustments, at any time until such pre-funded warrants are exercised in full.

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Moreover, following this offering, the market value of the warrants, if any, is uncertain. There can be no assurance that the market value of the warrants will equal or exceed their offering price. The warrants will not be listed or quoted for trading on any market or exchange. There can be no assurance that the market price of the common stock will ever equal or exceed the exercise price of the warrants, and consequently, it may not ever be profitable for holders of the warrants to exercise the warrants.

If you purchase securities in this offering, you may also experience future dilution as a result of future or additional equity offerings.

To raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price paid by investors in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions may be higher or lower than the price paid by investors in this offering. For example, we may, from time to time, issue and sell shares of our common stock having up to an aggregate offering price of $80,000,000 under a sales agreement through an “at the market offering” program. We have agreed with the purchaser in this offering not to sell any securities, including under the sales agreement, for a period of up to 90 days following this offering. We may resume sales following the earlier of the expiration of, or release from, this lock-up period. As of October 29, 2019, we had sold 305,522 shares of our common stock under the sales agreement at an average price of $129.70 per share for an aggregate offering price of $39.6 million, before deducting sales commissions and offering expenses.

Because we do not anticipate paying any cash dividends on our capital stock in the foreseeable future, capital appreciation, if any, will be your sole source of gain.

We have never declared or paid cash dividends on our capital stock. We currently intend to retain all of our future earnings, if any, to finance the growth and development of our business. As a result, capital appreciation, if any, of our common stock will be your sole source of gain for the foreseeable future.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents we incorporate by reference herein and therein include forward-looking statements. Any statement contained in this prospectus supplement, the accompanying prospectus or in the documents we incorporate by reference herein and therein, other than a statement of historical fact, may be a forward-looking statement, including statements regarding our and our collaborators’ future discovery, development and commercialization efforts, strategy, future operations, future financial position, future revenue, projected costs, prospects, plans and objectives of management. In some cases, you can identify forward-looking statements by such terms as “anticipate,” “believe,” “could,” “estimate,” “expect,” “forecast,” “intend,” “might,” “may,” “plan,” “project,” “should,” “target,” “will,” “would” or other words that convey uncertainty of future events or outcomes to identify these forward-looking statements. Forward-looking statements may include, but are not limited to, statements about:

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the period in which we anticipate that existing cash and cash equivalents will enable us to fund our current and planned operations;

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revenue received from commercial sales of Xerava;

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our estimates regarding expenses, capital requirements and needs for additional financing;

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our ability to enter into collaborations, licensing, marketing, distribution or other arrangements with respect to Xerava and our product candidates, and the terms and timing of any such arrangements into which we enter;

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the timing and costs of manufacturing and other activities in connection with the commercialization of Xerava;

•

our competitive position;

•

our intellectual property position;

•

developments and projections relating to our competitors and our industry;

•

our ability to continue as a going concern; and

•

our intended use of proceeds from this offering.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included in this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein, particularly the “Risk Factors” section of this prospectus supplement and in Part II, Item 1A of our most recent quarterly report on Form 10-Q that could cause actual results or events to differ materially from those indicated by these forward-looking statements. We do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

If one or more of these factors materialize, or if any underlying assumptions prove incorrect, our actual results, performance or achievements may vary materially from any future results, performance or achievements expressed or implied by these forward-looking statements.

You should consider these factors and the other cautionary statements made in this prospectus supplement, the accompanying prospectus and the documents we incorporate by reference herein and therein as being applicable to all related forward-looking statements wherever they appear in this prospectus supplement, the accompanying prospectus, or the documents incorporated by reference. While we may elect to update forward-looking statements wherever they appear in this prospectus supplement, the accompanying prospectus, or the documents incorporated by reference herein and therein, we do not assume, and specifically disclaim, any obligation to do so, whether as a result of new information, future events or otherwise, unless required by law.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $7.0 million, in each case after deducting the estimated placement agent fees and estimated offering expenses payable by us. These estimates exclude the proceeds, if any, from the exercise of the warrants sold in this offering. If all of the warrants sold in this offering were to be exercised in cash at their exercise price, we would receive additional proceeds of approximately $7.8 million.

We intend to use the net proceeds from this offering, together with our existing cash and cash equivalents, for the commercialization of Xerava, as well as working capital and other general corporate purposes. We are undertaking this transaction in part to extend our ability to fund our operating expenses and capital expenditure requirements.

We believe, based on our current operating plan and with the receipt of any proceeds from this offering, that our existing cash and cash equivalents and our projected revenues from sales of Xerava will be sufficient to fund our operations into the third quarter of 2020.

This expected use of net proceeds from this offering represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the commercialization of Xerava, as well as any additional collaborations that we may enter into with third parties for our product candidates, and any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from this offering. We intend to invest the proceeds, pending their use as described above, in short-term, interest-bearing, investment-grade securities.

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DIVIDEND POLICY

We have never declared or paid cash dividends on our common stock. We currently intend to retain all available funds and any future earnings to fund the development and expansion of our business and we do not anticipate paying any cash dividends in the foreseeable future. Any future determination to declare and pay dividends will be made at the discretion of our board of directors and will depend on then-existing conditions, including our results of operations, financial condition, contractual restrictions, capital requirements, business prospects and other factors our board of directors may deem relevant.

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CAPITALIZATION

The following table sets forth our consolidated cash and cash equivalents and capitalization as of June 30, 2019, as follows:

•

on a pro forma basis giving effect to (i) the repayment in full and termination of, on August 30, 2019, our loan and security agreement with Solar Capital Ltd. and the other lenders party thereto and (ii) the one-for-20 reverse stock split of our common stock that was effected on September 26, 2019; and

•

on a pro forma as adjusted basis to give further effect to the issuance and sale of (i) 300,000 shares of common stock and accompanying common stock warrants to purchase up to an aggregate of 300,000 shares of our common stock and (ii) pre-funded warrants to purchase up to an aggregate of 1,830,439 shares of common stock and accompanying common stock warrants to purchase up to an aggregate of 1,830,439 shares of our common stock in this offering, in each case after deducting placement agent fees and estimated offering expenses payable by us, and assuming no exercise of the warrants offered hereby, no value is attributed to such warrants and such warrants are classified and accounted for as equity.

You should read the following table together with “Description of Capital Stock” beginning on page 17 of the accompanying prospectus, and our consolidated financial statements and related notes to those statements and the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Quarterly Report on Form 10-Q for the period ended June 30, 2019, which is incorporated by reference in this prospectus supplement. In addition, there can be no assurance that the warrants issued in this offering will be classified as and accounted for as equity.


	As of June 30, 2019
(in thousands, except share and per share data)	Pro forma			Pro forma as adjusted
Cash and cash equivalents	$	40,232		$	47,204

Loans payable, net of current portion and discount	$	—		$	—
Stockholders’ equity
Preferred stock, par value $0.001 per share; 5,000,000 shares authorized, no shares issued or outstanding, actual, pro forma and pro forma as adjusted	$	—		$	—
Common stock, par value $0.001 per share; 125,000,000 shares authorized and 54,316,535 shares issued and outstanding, actual; 125,000,000 shares authorized and 2,715,824 shares issued and outstanding, pro forma; and 125,000,000 shares authorized and 3,015,824 shares issued and outstanding, pro forma as adjusted	$	54		$	54
Additional paid-in capital	$	618,142		$	625,114
Accumulated deficit	$	(578,425	)	$	(578,425	)

Total stockholders’ equity	$	39,771		$	46,743

Total capitalization	$	39,771		$	46,743

The foregoing table does not include:

•

20,718 shares of our common stock issuable upon the exercise of warrants outstanding as of June 30, 2019, at a weighted-average exercise price of $43.44 per share;

•

343,109 shares of our common stock issuable upon the exercise of stock options outstanding as of June 30, 2019, at a weighted-average exercise price of $228.24 per share;

•

129,530 shares of our common stock issuable upon the vesting of restricted stock units outstanding as of June 30, 2019;

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•

58,583 and 15,000 additional shares of our common stock available for future issuance, as of June 30, 2019, under our 2013 stock incentive plan and our 2014 employee stock purchase plan, as amended, respectively; and

•

11,152,678 shares of common stock available for sale as of June 30, 2019 under our sales agreement in respect of our “at-the-market” program (based on an aggregate of $40.4 million of common stock available for sale under the sales agreement, as amended, and assuming sales at a price of $3.62 per share, which was the closing price of our common stock on The Nasdaq Global Select Market on October 29, 2019).

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DILUTION

If you purchase securities in this offering, your ownership interest will be diluted immediately to the extent of the difference between the offering price per share you will pay in this offering and the pro forma as adjusted net tangible book value per share of our common stock after this offering.

Our historical net tangible book value as of June 30, 2019 was $37.3 million, or $0.69 per share of common stock. Our historical net tangible book value is the amount of our total tangible assets less our total liabilities. Historical net tangible book value per share represents our historical net tangible book value divided by the number of shares of our common stock outstanding as of June 30, 2019.

Our pro forma net tangible book value as of June 30, 2019 was $35.3 million, or $13.00 per share of our common stock. Pro forma net tangible book value represents the amount of our total tangible assets less our total liabilities, after giving effect to (i) the repayment in full and termination of, on August 30, 2019, the Company’s loan and security agreement with Solar Capital Ltd. and the other lenders party thereto and (ii) the one-for-20 reverse stock split of our common stock that was effected on September 26, 2019. Pro forma net tangible book value per share represents pro forma net tangible book value divided by 2,715,824 shares of common stock outstanding, pro forma, as of June 30, 2019, after giving effect to the pro forma adjustments described above.

After giving effect to the issuance and sale of (i) 300,000 shares of common stock and accompanying common stock warrants to purchase up to an aggregate of 300,000 shares of our common stock in this offering and (ii) pre-funded warrants to purchase up to on aggregate of 1,830,439 shares of common stock and accompanying common stock warrants to purchase up to an aggregate of 1,830,439 shares of our common stock in this offering, in each case after deducting placement agent fees and estimated offering expenses payable by us, and assuming no exercise of the warrants offered hereby, that no value is attributed to such warrants and that such warrants are classified and accounted for as equity, our pro forma as adjusted net tangible book value as of June 30, 2019 would have been $42.3 million, or $14.02 per share. This represents an immediate increase of $1.02 in pro forma as adjusted net tangible book value per share to existing stockholders and immediate dilution of $(10.265) in pro forma as adjusted net tangible book value per share to investors purchasing securities in this offering. In addition, there can be no assurance that any warrants issued in this offering will be classified as and accounted for as equity. The following table illustrates this calculation:


Offering price per share of common stock and accompanying common stock warrant			$	3.755
Historical net tangible book value per share as of June 30, 2019	$	0.69
Increase per share attributable to the pro forma adjustments described above		12.31

Pro forma net tangible book value per share as of June 30, 2019		13.00
Increase in pro forma as adjusted net tangible book value per share attributable to this offering		1.02

Pro forma as adjusted net tangible book value per share after giving effect to this offering			$	14.02

Dilution in pro forma as adjusted net tangible book value to new investors in this offering			$	(10.265	)

The calculations in the foregoing table and discussion do not include, as of June 30, 2019:

•

20,718 shares of our common stock issuable upon the exercise of warrants outstanding as of June 30, 2019, at a weighted-average exercise price of $43.44 per share;

•

343,109 shares of our common stock issuable upon the exercise of stock options outstanding as of June 30, 2019, at a weighted-average exercise price of $228.24 per share;

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•

129,530 shares of our common stock issuable upon the vesting of restricted stock units outstanding as of June 30, 2019;

•

To the extent that any of our outstanding options or warrants are exercised at prices below the offering price, we grant additional options or other awards under our equity incentive plans or issue additional warrants, the warrants issued in this offering are accounted for as liabilities or we issue additional shares of common stock in the future, there may be further dilution to new public investors.

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DESCRIPTION OF SECURITIES WE ARE OFFERING

Common Stock

The material terms and provisions of our common stock are described under the heading “Description of Capital Stock” in the accompanying prospectus.

Pre-Funded Warrants

The following is a summary of the material terms and provisions of the pre-funded warrants that are being offered hereby. This summary is subject to and qualified in its entirety by the form of pre-funded warrants, which has been provided to the investors in this offering and which has been filed with the U.S. Securities and Exchange Commission, or SEC, as an exhibit to a Current Report on Form 8-K in connection with this offering and incorporated by reference into the registration statement of which this prospectus forms a part. Prospective investors should carefully review the terms and provisions of the form of warrant for a complete description of the terms and conditions of the pre-funded warrants.

Duration and Exercise Price

The pre-funded warrants offered hereby will have an exercise price of $0.01 per share. The pre-funded warrants will be immediately exercisable and may be exercised at any time after their original issuance until such pre-funded warrants are exercised in full. The exercise prices and numbers of shares of common stock issuable upon exercise are subject to appropriate adjustment in the event of stock dividends, stock splits, reorganizations or similar events affecting our common stock. Pre-funded warrants will be issued in certificated form only.

Exercisability

The pre-funded warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of shares of our common stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of such holder’s warrants to the extent that the holder would own more than 4.99% of our outstanding common stock immediately after exercise, except that upon at least 61 days’ prior notice from the holder to us, the holder may increase the amount of ownership of outstanding stock after exercising the holder’s pre-funded warrants up to 9.99% of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants. Purchasers in this offering may also elect prior to the issuance of pre-funded warrants to have the initial exercise limitation set at 9.99% of our outstanding common stock. Further, such pre-funded warrants may not be exercised to the extent that such exercise would result in a holder and its affiliates beneficially owning more than 19.99% of the outstanding common stock or outstanding voting power of the Company (including shares of common stock issuable upon exercise of the warrants held by them).

Cashless Exercise

If, at the time a holder exercises its warrants, a registration statement registering the issuance of the shares of common stock underlying the warrants under the Securities Act of 1933, as amended, or the Securities Act, is not then effective or available for the issuance of such shares, then in lieu of making the cash payment otherwise contemplated to be made to us upon such exercise in payment of the aggregate exercise price, the holder may elect instead to receive upon such exercise (either in whole or in part) the net number of shares of common stock determined according to a formula set forth in the warrant.

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Fundamental Transactions

In the event of any fundamental transaction, as described in the pre-funded warrants and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer or exchange offer, or reclassification of our common stock, then upon any subsequent exercise of a pre-funded warrant, the holder will have the right to receive as alternative consideration, for each share of our common stock that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction, the number of shares of common stock of the successor or acquiring corporation or of our company, if it is the surviving corporation, and any additional consideration receivable upon or as a result of such transaction by a holder of the number of shares of our common stock for which the pre-funded warrant is exercisable immediately prior to such event.

Transferability

In accordance with its terms and subject to applicable laws and a standard legend with regard to restriction on transfer only in compliance with a public offering or an available exemption therefrom, a pre-funded warrant may be transferred at the option of the holder upon surrender of the pre-funded warrant to us together with the appropriate instruments of transfer.

Fractional Shares

No fractional shares of common stock will be issued upon the exercise of the pre-funded warrants. Rather, the number of shares of common stock to be issued will, at our election, either be rounded up to the nearest whole number or we will pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price.

Trading Market

There is no established trading market for any of the pre-funded warrants, and we do not expect a market to develop. We do not intend to apply for a listing for any of the warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the pre-funded warrants will be limited.

Rights as a Stockholder

Except as otherwise provided in the pre-funded warrants or by virtue of the holders’ ownership of shares of our common stock, the holders of pre-funded warrants do not have the rights or privileges of holders of our common stock, including any voting rights, until such pre-funded warrant holders exercise their warrants.

Waivers and Amendments

No term of the pre-funded may be amended or waived without the written consent of the holder of such warrant.

Common Stock Warrants

The following is a summary of the material terms and provisions of the common stock warrants that are being offered hereby. This summary is subject to and qualified in its entirety by the form of common stock warrant, which has been provided to the investors in this offering and has been filed with the SEC as an exhibit to a Current Report on Form 8-K in connection with this offering and incorporated by reference into the registration statement of which this prospectus forms a part. Prospective investors should carefully review the terms and provisions of the form of common stock warrant for a complete description of the terms and conditions of the common stock warrants.

Duration and Exercise Price

The common stock warrants offered hereby will have an exercise price of $3.62 per share. The common stock warrants will be immediately exercisable and may be exercised until the fifth anniversary of the issuance date, at

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which time they will be automatically exercised on a cashless basis. The exercise prices and numbers of shares of common stock issuable upon exercise are subject to appropriate adjustment in the event of stock dividends, stock splits, reorganizations or similar events affecting our common stock. The common stock warrants will be issued separately from the shares of common stock offered hereby, and may be transferred separately immediately thereafter. Common stock warrants will be issued in certificated form only.

Exercisability

The common stock warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of shares of our common stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of such holder’s warrants to the extent that the holder would own more than 4.99% of our outstanding common stock immediately after exercise, except that upon at least 61 days’ prior notice from the holder to us, the holder may increase the amount of ownership of outstanding stock after exercising the holder’s common stock warrants up to 9.99% of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the warrants. Purchasers in this offering may also elect prior to the issuance of common stock warrants to have the initial exercise limitation set at 9.99% of our outstanding common stock. Further, such common stock warrants may not be exercised to the extent that such exercise would result in a holder and its affiliates beneficially owning more than 19.99% of the outstanding common stock or outstanding voting power of the Company (including shares of common stock issuable upon exercise of the warrants held by them).

Cashless Exercise

If, at the time a holder exercises its common stock warrants, a registration statement registering the issuance of the shares of common stock underlying the warrants under the Securities Act of 1933, as amended, or the Securities Act, is not then effective or available for the issuance of such shares, then in lieu of making the cash payment otherwise contemplated to be made to us upon such exercise in payment of the aggregate exercise price, the holder may elect instead to receive upon such exercise (either in whole or in part) the net number of shares of common stock determined according to a formula set forth in the common stock warrant. The common stock warrants will be automatically exercised on a cashless basis on the expiration date.

Fundamental Transactions

In the event of any fundamental transaction, as described in the common stock warrants and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer or exchange offer, or reclassification of our common stock, then upon any subsequent exercise of a common stock warrant, the holder will have the right to receive as alternative consideration, for each share of our common stock that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction, the number of shares of common stock of the successor or acquiring corporation or of our company, if it is the surviving corporation, and any additional consideration receivable upon or as a result of such transaction by a holder of the number of shares of our common stock for which the common stock warrant is exercisable immediately prior to such event.

In addition, in certain circumstances, upon a fundamental transaction, the holder of common stock warrants will have the right to require us to repurchase its common stock warrants at their fair value using the Black Scholes option pricing formula; provided, however, (1) such holder may not require us or our successor entity to repurchase the warrants for the Black Scholes value in connection with a fundamental transaction that is not approved by our board of directors, and therefore not within our control and (2) in the event that the alternate consideration payable to holders of the Company’s common stock in such fundamental transaction consists of equity securities of the successor or acquirer that are quoted or listed on a nationally recognized securities

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exchange, then the holder of the common stock warrants shall only be entitled to receive the same type or form of consideration (and in the same proportion), determined in accordance with the Black Scholes option pricing formula.

Transferability

In accordance with its terms and subject to applicable laws and a standard legend with regard to restriction on transfer only in compliance with a public offering or an available exemption therefrom, a common stock warrant may be transferred at the option of the holder upon surrender of the common stock warrant to us together with the appropriate instruments of transfer.

Fractional Shares

No fractional shares of common stock will be issued upon the exercise of the common stock warrants. Rather, the number of shares of common stock to be issued will, at our election, either be rounded up to the nearest whole number or we will pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price.

Trading Market

There is no established trading market for any of the common stock warrants, and we do not expect a market to develop. We do not intend to apply for a listing for any of the common stock warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the common stock warrants will be limited.

Rights as a Stockholder

Except as otherwise provided in the common stock warrants or by virtue of the holders’ ownership of shares of our common stock, the holders of common stock warrants do not have the rights or privileges of holders of our common stock, including any voting rights, until such warrant holders exercise their common stock warrants.

Waivers and Amendments

No term of the common stock warrants may be amended or waived without the written consent of the holder of such warrant.

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MATERIAL U.S. FEDERAL TAX CONSIDERATIONS FOR HOLDERS OF OUR

COMMON STOCK, PRE-FUNDED WARRANTS AND COMMON STOCK WARRANTS

The following discussion describes the material U.S. federal income tax consequences of the acquisition, ownership and disposition of our common stock, pre-funded warrants and common stock warrants acquired in this offering. This discussion is based on the current provisions of the Internal Revenue Code of 1986, as amended (referred to as the “Code”), existing and proposed U.S. Treasury regulations promulgated thereunder, and administrative rulings and court decisions in effect as of the date hereof, all of which are subject to change at any time, possibly with retroactive effect. No ruling has been or will be sought from the Internal Revenue Service, or IRS, with respect to the matters discussed below, and there can be no assurance the IRS will not take a contrary position regarding the tax consequences of the acquisition, ownership or disposition of our common stock, pre-funded warrants or common stock warrants, or that any such contrary position would not be sustained by a court.

We assume in this discussion that the shares of our common stock, pre-funded warrants and common stock warrants will be held as capital assets (generally, property held for investment). This discussion does not address all aspects of U.S. federal income taxes, does not discuss the potential application of the Medicare contribution tax on net investment income, the alternative minimum tax and does not address state or local taxes, U.S. federal gift and estate tax laws, except as specifically provided below with respect to non-U.S. holders, or any non-U.S. tax consequences that may be relevant to holders in light of their particular circumstances. This discussion also does not address the special tax rules applicable to particular holders, such as:

•

financial institutions;

•

brokers or dealers in securities;

•

tax-exempt organizations;

•

pension plans;

•

regulated investment companies;

•

owners that hold our common stock, pre-funded warrants or common stock warrants as part of a straddle, hedge, conversion transaction, synthetic security or other integrated investment;

•

insurance companies;

•

controlled foreign corporations, passive foreign investment companies, or corporations that accumulate earnings to avoid U.S. federal income tax; and

•

certain U.S. expatriates.

In addition, this discussion does not address the tax treatment of partnerships or other pass-through entities or persons who hold our common stock, pre-funded warrants or common stock warrants through partnerships or other entities which are pass-through entities for U.S. federal income tax purposes. A partner in a partnership or other pass-through entity that will hold our common stock, pre-funded warrants or common stock warrants should consult his, her or its own tax advisor regarding the tax consequences of the ownership and disposition of our common stock, pre-funded warrants or common stock warrants through a partnership or other pass-through entity, as applicable.

This discussion of U.S. federal income tax considerations is for information purposes only and is not tax advice. Prospective investors should consult their own tax advisors regarding the U.S. federal, state, local and non-U.S. income and other tax considerations of acquiring, holding and disposing of our common stock, pre-funded warrants and common stock warrants.

For the purposes of this discussion, a “U.S. Holder” means a beneficial owner (other than a partnership or other pass-through entity) of our common stock, pre-funded warrants or common stock warrants that is for U.S. federal

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income tax purposes (a) an individual citizen or resident of the United States, (b) a corporation (or other entity taxable as a corporation for U.S. federal income tax purposes), created or organized in or under the laws of the United States, any state thereof or the District of Columbia, (c) an estate the income of which is subject to U.S. federal income taxation regardless of its source, or (d) a trust if it (1) is subject to the primary supervision of a court within the United States and one or more U.S. persons (within the meaning of Section 7701(a)(30) of the Code) have the authority to control all substantial decisions of the trust or (2) has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person. A “Non-U.S. Holder” is, for U.S. federal income tax purposes, a beneficial owner of common stock, pre-funded warrants or common stock warrants that is not a U.S. Holder or a partnership for U.S. federal income tax purposes.

Allocation of Purchase Price to Common Stock, Pre-funded Warrants and Common Stock Warrants

For U.S. federal income tax purposes, a holder’s acquisition of the common stock warrants and common stock or prefunded warrants, as applicable, should be treated as the acquisition of an “investment unit” consisting of one share of common stock or one pre-funded warrant, as applicable, and a warrant to acquire 1 share of our common stock, subject to adjustment. The purchase price for each investment unit will be allocated between these two components in proportion to their relative fair market values at the time the unit is purchased by the holder. This allocation of the purchase price for each unit will establish the holder’s initial tax basis for U.S. federal income tax purposes in the common stock or pre-funded warrant, as applicable, and the common stock warrant included in each unit. The separation of the share of common stock or pre-funded warrant, as applicable, and the common stock warrant included in each unit should not be a taxable event for U.S. federal income tax purposes. Each holder should consult his, her or its own tax advisor regarding the allocation of the purchase price for a unit.

Treatment of Pre-Funded Warrants

Although it is not entirely free from doubt, a pre-funded warrant should be treated as a share of our common stock for U.S. federal income tax purposes and a holder of pre-funded warrants should generally be taxed in the same manner as a holder of common stock as described below. Accordingly, upon exercise, the holding period of a pre-funded warrant should carry over to the share of common stock received. Similarly, the tax basis of the pre-funded warrant should carry over to the share of common stock received upon exercise increased by the exercise price of $0.01. Each holder should consult his, her or its own tax advisor regarding the risks associated with the acquisition of a unit pursuant to this offering (including potential alternative characterizations). The balance of this discussion generally assumes that the characterization described above is respected for U.S. federal income tax purposes.

Tax Considerations Applicable to U.S. Holders

Exercise and Expiration of Common Stock Warrants

In general, a U.S. Holder will not recognize gain or loss for U.S. federal income tax purposes upon exercise of a common stock warrant. The U.S. Holder will take a tax basis in the shares acquired on the exercise of a common stock warrant equal to the exercise price of the warrant, increased by the U.S. Holder’s adjusted tax basis in the warrant exercised (as determined pursuant to the rules discussed above). The U.S. Holder’s holding period in the shares of our common stock acquired on exercise of the common stock warrant will begin on the date of exercise of the warrant (or possibly, the day after), and will not include any period for which the U.S. Holder held the warrant.

In certain limited circumstances, a U.S. Holder may be permitted to undertake a cashless exercise of common stock warrants into our common stock. The U.S. federal income tax treatment of a cashless exercise of common stock warrants into our common stock is unclear, and the tax consequences of a cashless exercise could differ from the consequences upon the exercise of a common stock warrant described in the preceding paragraph. U.S. Holders should consult their own tax advisors regarding the U.S. federal income tax consequences of a cashless exercise of common stock warrants.

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The lapse or expiration of a common stock warrant will be treated as if the U.S. Holder sold or exchanged the warrant and recognized a capital loss equal to the U.S. Holder’s tax basis in the warrant. The deductibility of capital losses is subject to limitations.

Certain Adjustments to and Distributions on the Common Stock Warrants

Under Section 305 of the Code, an adjustment to the number of shares of common stock issued on the exercise of the common stock warrants, or an adjustment to the exercise price of the common stock warrants, may be treated as a constructive distribution to a U.S. Holder of the warrants if, and to the extent that, such adjustment has the effect of increasing such U.S. Holder’s proportionate interest in our “earnings and profits” or assets, depending on the circumstances of such adjustment. An adjustment made pursuant to a bona fide reasonable adjustment formula that has the effect of preventing dilution should generally not be considered to result in a constructive distribution. Any such constructive distribution would be taxable whether or not there is an actual distribution in cash or other property to the holders of common stock warrants. In certain circumstances, if we were to make a distribution in cash or other property with respect to our common stock after the issuance of the common stock warrants, then we may make a corresponding distribution to a warrant holder. The taxation of a distribution received with respect to a warrant is unclear. It is possible such a distribution would be treated as a distribution (or constructive distribution), although other treatments are possible. For more information regarding the tax considerations related to distributions, see the discussion below regarding “Distributions”. U.S. Holders should consult their tax advisors regarding the proper treatment of any adjustments to and distributions on the common stock warrants.

Distributions

As discussed above, we currently anticipate that we will retain future earnings for the development, operation, and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. In the event that we do make distributions on our common stock or pre-funded warrants to a U.S. Holder, those distributions generally will constitute dividends for U.S. tax purposes to the extent paid out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles). Distributions in excess of our current and accumulated earnings and profits will constitute a return of capital that is applied against and reduces, but not below zero, a U.S. Holder’s adjusted tax basis in our common stock or pre-funded warrants, as applicable. Any remaining excess will be treated as gain realized on the sale or exchange of our common stock or pre-funded warrants as described below under the section titled “—Disposition of Our Common Stock, Pre-Funded Warrants or Common Stock Warrants.”

Disposition of Our Common Stock, Pre-Funded Warrants or Common Stock Warrants

Upon a sale or other taxable disposition of our common stock, pre-funded warrants or common stock warrants, a U.S. Holder generally will recognize capital gain or loss in an amount equal to the difference between the amount realized and the U.S. Holder’s adjusted tax basis in the common stock, pre-funded warrants or common stock warrants. Capital gain or loss will constitute long-term capital gain or loss if the U.S. Holder’s holding period for the common stock, pre-funded warrants or common stock warrants exceeds one year. The deductibility of capital losses is subject to certain limitations. U.S. Holders who recognize losses with respect to a disposition of our common stock, pre-funded warrants or common stock warrants should consult their own tax advisors regarding the tax treatment of such losses.

Information Reporting and Backup Withholding

Information reporting requirements generally will apply to payments of dividends (including constructive dividends) on the common stock, pre-funded warrants and common stock warrants and to the proceeds of a sale or other disposition of common stock, pre-funded warrants and common stock warrants paid by us to a U.S. Holder unless such U.S. Holder is an exempt recipient, such as a corporation. Backup withholding will apply to

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those payments if the U.S. Holder fails to provide the holder’s taxpayer identification number, or certification of exempt status, or if the holder otherwise fails to comply with applicable requirements to establish an exemption. Backup withholding is not an additional tax. Rather, any amounts withheld under the backup withholding rules will be allowed as a refund or a credit against the U.S. Holder’s U.S. federal income tax liability provided the required information is timely furnished to the IRS.

Tax Considerations Applicable To Non-U.S. Holders

Exercise and Expiration of Common Stock Warrants

In general, a Non-U.S. Holder will not be subject to U.S. federal income tax on the exercise of the common stock warrants into shares of common stock. The U.S. federal income tax treatment of a cashless exercise of common stock warrants into our common stock is unclear. A Non-U.S. Holder should consult his, her, or its own tax advisor regarding the U.S. federal income tax consequences of a cashless exercise of common stock warrants.

The expiration or lapse of a common stock warrant will be treated as if the Non-U.S. Holder sold or exchanged the warrant and recognized a capital loss equal to the Non-U.S. Holder’s tax basis in the warrant. However, a Non-U.S. Holder will not be able to utilize a loss recognized upon expiration or lapse of a warrant against the Non-U.S. Holder’s U.S. federal income tax liability unless the loss is effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States (and, if an income tax treaty applies, is attributable to a permanent establishment or fixed base in the United States) or is treated as a U.S.-source loss and the Non-U.S. Holder is present in the United States for 183 days or more in the taxable year of disposition and certain other conditions are met.

Certain Adjustments to and Distributions on the Common Stock Warrants

As described under “—U.S. Holders—Certain Adjustments to and Distributions on the Common Stock Warrants”, an adjustment to the common stock warrants could result in a constructive distribution to a Non-U.S. Holder, which would be treated as described under “Distributions” below, and the tax treatment of a distribution on a common stock warrant is unclear. Any resulting withholding tax attributable to deemed dividends would be collected from other amounts payable or distributable to the Non-U.S. Holder. Non-U.S. Holders should consult their tax advisors regarding the proper treatment of any adjustments to and distributions on the common stock warrants.

Distributions

Any distribution (including constructive distributions) on our common stock or pre-funded warrants that is treated as a dividend paid to a Non-U.S. Holder that is not effectively connected with the holder’s conduct of a trade or business in the United States will generally be subject to withholding tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and the Non-U.S. Holder’s country of residence. To obtain a reduced rate of withholding under a treaty, a Non-U.S. Holder generally will be required to provide the applicable withholding agent with a properly executed IRS Form W-8BEN, IRS Form W-8BEN-E or other appropriate form, certifying the Non-U.S. Holder’s entitlement to benefits under that treaty. Non-U.S. Holders are urged to consult their own tax advisors regarding their entitlement to benefits under a relevant income tax treaty and the specific methods available to them to satisfy these requirements.

We generally are not required to withhold tax on dividends paid (or constructive dividends deemed paid) to a Non-U.S. Holder that are effectively connected with the holder’s conduct of a trade or business within the United

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States (and, if required by an applicable income tax treaty, are attributable to a permanent establishment or fixed base that the holder maintains in the United States) if a properly executed IRS Form W-8ECI, stating that the dividends are so connected, is furnished to us or the applicable withholding agent. In general, such effectively connected dividends will be subject to U.S. federal income tax on a net income basis at the regular graduated rates applicable to U.S. persons. A corporate Non-U.S. Holder receiving effectively connected dividends may also be subject to an additional “branch profits tax,” which is imposed, under certain circumstances, at a rate of 30% (or such lower rate as may be specified by an applicable treaty) on the corporate Non-U.S. Holder’s effectively connected earnings and profits, subject to certain adjustments.

See also the sections below titled “—Information Reporting and Backup Withholding” and “—Foreign Accounts” for additional withholding rules that may apply to dividends paid to certain foreign financial institutions or non-financial foreign entities.

Disposition of Our Common Stock, Pre-Funded Warrants or Common Stock Warrants

Subject to the discussions below under the sections titled “—Information Reporting and Backup Withholding” and “—Foreign Accounts,” a Non-U.S. Holder generally will not be subject to U.S. federal income or withholding tax with respect to gain realized on a sale or other disposition of our common stock, pre-funded warrant or common stock warrants unless:

•

the gain is effectively connected with the Non-U.S. Holder’s conduct of a trade or business in the United States, and if an applicable income tax treaty so provides, the gain is attributable to a permanent establishment or fixed base maintained by the Non-U.S. Holder in the United States; in these cases, the Non-U.S. Holder will be taxed on a net income basis at the regular graduated rates and in the manner applicable to U.S. persons, and if the Non-U.S. Holder is a corporation, an additional branch profits tax at a rate of 30%, or a lower rate as may be specified by an applicable income tax treaty, may also apply;

•

the Non-U.S. Holder is a nonresident alien present in the United States for 183 days or more in the taxable year of the disposition and certain other requirements are met, in which case the Non-U.S. Holder will be subject to a 30% tax (or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence) on the net gain derived from the disposition, which may be offset by certain U.S.-source capital losses of the Non-U.S. Holder, if any; or

•

we are, or have been at any time during the five-year period preceding such disposition (or the Non-U.S. Holder’s holding period of the common stock, pre-funded warrants or common stock warrants, if shorter), a “U.S. real property holding corporation,” unless our common stock is regularly traded on an established securities market and the Non-U.S. Holder held no more than 5% of our outstanding common stock, directly or indirectly, during the shorter of the five-year period ending on the date of the disposition or the period that the Non-U.S. Holder held our common stock. Special rules may apply to the determination of the 5% threshold in the case of a holder of a pre-funded warrant or common stock warrant. Non-U.S. Holders are urged to consult their own tax advisors regarding the effect of holding our pre-funded warrants or common stock warrants on the calculation of such 5% threshold. Generally, a corporation is a “U.S. real property holding corporation” if the fair market value of its “U.S. real property interests” (as defined in the Code and applicable regulations) equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus its other assets used or held for use in a trade or business. Although there can be no assurance, we believe that we are not currently, and we do not anticipate becoming, a “U.S. real property holding corporation” for U.S. federal income tax purposes. No assurance can be provided that our common stock will be regularly traded on an established securities market for purposes of the rules described above.

See the sections titled “—Information Reporting and Backup Withholding” and “—Foreign Accounts” below for additional information regarding withholding rules that may apply to proceeds of a disposition of our common

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stock, pre-funded warrants or common stock warrants paid to foreign financial institutions or non-financial foreign entities.

Federal Estate Tax

Common stock or pre-funded warrants owned or treated as owned by an individual who is a Non-U.S. Holder (as specially defined for U.S. federal estate tax purposes) at the time of death will be included in the individual’s gross estate for U.S. federal estate tax purposes and, therefore, may be subject to U.S. federal estate tax, unless an applicable estate tax or other treaty provides otherwise. The foregoing may also apply to common stock warrants.

Information Reporting and Backup Withholding

We must report annually to the IRS and to each Non-U.S. Holder the gross amount of the distributions (including constructive distributions) on our common stock, pre-funded warrants or common stock warrants paid to such holder and the tax withheld, if any, with respect to such distributions. Non-U.S. Holders may have to comply with specific certification procedures to establish that the holder is not a U.S. person (as defined in the Code) in order to avoid backup withholding at the applicable rate, currently 24%, with respect to dividends (including constructive dividends) on our common stock, pre-funded warrants, or common stock warrants. Generally, a holder will comply with such procedures if it provides a properly executed IRS Form W-8BEN (or other applicable Form W-8) or otherwise meets documentary evidence requirements for establishing that it is a Non-U.S. Holder, or otherwise establishes an exemption. Dividends paid to Non-U.S. Holders subject to withholding of U.S. federal income tax, as described above under the heading “Distributions,” will generally be exempt from U.S. backup withholding.

Information reporting and backup withholding generally will apply to the proceeds of a disposition of our common stock, pre-funded warrants or common stock warrants by a Non-U.S. Holder effected by or through the U.S. office of any broker, U.S. or foreign, unless the holder certifies its status as a Non-U.S. Holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to a Non-U.S. Holder where the transaction is effected outside the United States through a non-U.S. office of a broker. However, for information reporting purposes, dispositions effected through a non-U.S. office of a broker with substantial U.S. ownership or operations generally will be treated in a manner similar to dispositions effected through a U.S. office of a broker. Non-U.S. Holders should consult their own tax advisors regarding the application of the information reporting and backup withholding rules to them.

Copies of information returns may be made available to the tax authorities of the country in which the Non-U.S. Holder resides or is incorporated under the provisions of a specific treaty or agreement.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment to a Non-U.S. Holder can be refunded or credited against the Non-U.S. Holder’s U.S. federal income tax liability, if any, provided that an appropriate claim is timely filed with the IRS.

Foreign Accounts

The Foreign Account Tax Compliance Act, or FATCA, generally imposes a 30% withholding tax on dividends on common stock, pre-funded warrants and common stock warrants if paid to a non-U.S. entity unless (i) if the non-U.S. entity is a “foreign financial institution,” the non-U.S. entity undertakes certain due diligence, reporting, withholding, and certification obligations, (ii) if the non-U.S. entity is not a “foreign financial institution,” the non-U.S. entity identifies certain of its U.S. investors, if any, or (iii) the non-U.S. entity is otherwise exempt under FATCA.

While withholding under FATCA may apply to payments of gross proceeds from a sale or other disposition of our common stock, pre-funded warrants or common stock warrants., under proposed U.S. Treasury Regulations,

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withholding on payments of gross proceeds is not required. Although such regulations are not final, applicable withholding agents may rely on the proposed regulations until final regulations are issued.

An intergovernmental agreement between the United States and an applicable foreign country may modify the requirements described in this section. Under certain circumstances, a holder may be eligible for refunds or credits of the tax. Holders should consult their own tax advisors regarding the possible implications of FATCA on their investment in our common stock, pre-funded warrants or common stock warrants.

The preceding discussion of material U.S. federal tax considerations is for information only. It is not tax advice. Prospective investors should consult their own tax advisors regarding the particular U.S. federal, state, local and non-U.S. tax consequences of purchasing, holding and disposing of our common stock, pre-funded warrants or common stock warrants, including the consequences of any proposed changes in applicable laws.

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PLAN OF DISTRIBUTION

Pursuant to a letter agreement dated as of September 29, 2019, as amended, we have retained H.C. Wainwright & Co., LLC, or Wainwright, to act as our exclusive placement agent in connection with this offering. Under the terms of the engagement letter, Wainwright is not purchasing the securities offered by us in this offering, and is not required to sell any specific number or dollar amount of securities. The terms of this offering were subject to market conditions and negotiations between us, Wainwright and the prospective investor.

Wainwright proposes to arrange for the sale of the shares, pre-funded warrants and common stock warrants we are offering pursuant to this prospectus supplement and accompanying prospectus to a single investor through securities purchase agreement directly between such investor and us. We will only sell to investors who have entered into securities purchase agreements with us.

Wainwright will have no authority to bind us by virtue of the engagement letter. Further, Wainwright does not guarantee that it will be able to raise new capital in any prospective offering. Wainwright may engage sub-agents or selected dealers to assist with this offering. We may not sell the entire amount of the securities being offered pursuant to this prospectus supplement.

Delivery of the securities offered hereby is expected to occur on or about November 1, 2019, subject to satisfaction of certain conditions.

We have agreed to pay Wainwright a cash fee equal to 7% of the gross proceeds received from the investor who purchased securities in the offering. We have also agreed to reimburse Wainwright $35,000 for non-accountable expenses, up to $100,000 for legal fees and expenses and other out-of-pocket expenses and $10,000 for clearing purposes. We estimate the total offering expenses of this offering that will be payable by us, excluding the placement agent’s fees and expenses, will be approximately $0.5 million.

We have agreed to indemnify Wainwright and specified other persons against certain liabilities relating to or arising out of Wainwright’s activities under the engagement letter and to contribute to payments that Wainwright may be required to make in respect of such liabilities.

Wainwright may be deemed to be an underwriter within the meaning of Section 2(a)(11) of the Securities Act, and any commissions received by it and any profit realized on the resale of the securities sold by it while acting as principal might be deemed to be underwriting discounts or commissions under the Securities Act. As an underwriter, Wainwright would be required to comply with the requirements of the Securities Act and the Exchange Act, including, without limitation, Rule 415(a)(4) under the Securities Act and Rule 10b-5 and Regulation M under the Exchange Act. These rules and regulations may limit the timing of purchases and sales of common shares by Wainwright acting as principal. Under these rules and regulations, Wainwright:

•

may not engage in any stabilization activity in connection with our securities; and

•

may not bid for or purchase any of our securities or attempt to induce any person to purchase any of our securities, other than as permitted under the Exchange Act, until it has completed its participation in the distribution.

The securities purchase agreement is included as an exhibit to a Current Report on Form 8-K that we have filed with the SEC and that is incorporated by reference into the registration statement of which this prospectus supplement forms a part.

From time to time, Wainwright may provide in the future various advisory, investment and commercial banking and other services to us in the ordinary course of business, for which they have received and may continue to receive customary fees and commissions. However, except as disclosed in this prospectus supplement, we have no present arrangements with Wainwright for any further services.

Our common stock is listed on The Nasdaq Global Select Market under the symbol “TTPH.”

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LEGAL MATTERS

The validity of the shares of common stock, pre-funded warrants and the accompanying warrants offered hereby will be passed upon for us by Wilmer Cutler Pickering Hale and Dorr LLP, Boston, Massachusetts. Lowenstein Sandler LLP, New York, New York has acted as counsel for the placement agent in connection with certain matters relating to this offering.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2018, and the effectiveness of our internal control over financial reporting as of December 31, 2018, as set forth in their reports, which are incorporated by reference into this prospectus and elsewhere in the registration statement. Our consolidated financial statements are incorporated by reference in reliance on Ernst & Young LLP’s reports, given on their authority as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION

This prospectus supplement is part of a registration statement we filed with the SEC. This prospectus supplement and the accompanying prospectus omit some information contained in the registration statement in accordance with SEC rules and regulations. You should review the information and exhibits in the registration statement for further information about us and our consolidated subsidiaries and the securities we are offering. Statements in this prospectus supplement and in the accompanying prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings. You should review the complete document to evaluate these statements.

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INCORPORATION BY REFERENCE

The SEC allows us to incorporate by reference into this prospectus supplement and the accompanying prospectus much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference is considered to be part of this prospectus supplement and the accompanying prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus supplement and the accompanying prospectus are continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus supplement and the accompanying prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus supplement, the accompanying prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus supplement and the accompanying prospectus incorporate by reference the documents listed below (File No. 001-35837) and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (in each case, other than those documents or the portions of those documents not deemed to be filed) until the offering of the securities under the registration statement is terminated or completed:

•

our Annual Report on Form 10-K for the fiscal year ended December 31, 2018;

•

our Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31, 2019 and June 30, 2019;

•

the information included in our definitive proxy statement on Schedule 14A for the 2019 Annual Meeting of Stockholders, filed on April 26, 2019, to the extent incorporated by reference into Part III of the Annual Report on Form 10-K for the fiscal year ended December 31, 2018;

•

our Current Reports on Form 8-K dated June 12, 2019, June 28, 2019, August 30, 2019, September 30, 2019 and October 2, 2019; and

•

the description of our common stock contained in our registration statement on Form 8-A filed on March 15, 2013, including any amendments or reports filed for the purpose of updating such description.

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address or telephone number:

Tetraphase Pharmaceuticals, Inc.

480 Arsenal Way

Watertown, Massachusetts 02472

Attention: Investor Relations

Telephone: (617) 715-3600

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PROSPECTUS

$150,000,000

TETRAPHASE PHARMACEUTICALS, INC.

Debt Securities

Common Stock

Preferred Stock

Warrants

We may offer and sell securities from time to time in one or more offerings of up to $150,000,000 in aggregate offering price. This prospectus describes the general terms of these securities and the general manner in which these securities will be offered. We will provide the specific terms of these securities in supplements to this prospectus. The prospectus supplements will also describe the specific manner in which these securities will be offered and may also supplement, update or amend information contained in this document. You should read this prospectus and any applicable prospectus supplement before you invest.

We may offer these securities in amounts, at prices and on terms determined at the time of offering. The securities may be sold directly to you, through agents, or through underwriters and dealers. If agents, underwriters or dealers are used to sell the securities, we will name them and describe their compensation in a prospectus supplement.

Our common stock is listed on The NASDAQ Global Select Market under the symbol “TTPH.”

Investing in these securities involves certain risks. See “Risk Factors” included in any accompanying prospectus supplement and in the documents incorporated by reference in this prospectus for a discussion of the factors you should carefully consider before deciding to purchase these securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is February 5, 2018

TABLE OF CONTENTS


	Page
ABOUT THIS PROSPECTUS		1
RISK FACTORS		1
WHERE YOU CAN FIND MORE INFORMATION		1
INCORPORATION BY REFERENCE		3
FORWARD-LOOKING STATEMENTS		4
TETRAPHASE PHARMACEUTICALS, INC.		5
CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES		7
USE OF PROCEEDS		8
DESCRIPTION OF DEBT SECURITIES		8
DESCRIPTION OF CAPITAL STOCK		17
DESCRIPTION OF WARRANTS		21
FORMS OF SECURITIES		22
PLAN OF DISTRIBUTION		24
LEGAL MATTERS		27
EXPERTS		27

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, which we refer to as the “SEC,” utilizing a “shelf” registration process. Under this shelf registration process, we may from time to time sell any combination of the securities described in this prospectus in one or more offerings for an aggregate initial offering price of up to $150,000,000.

This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide one or more prospectus supplements that will contain specific information about the terms of the offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and the accompanying prospectus supplement together with the additional information described under the heading “Where You Can Find More Information” beginning on page 1 of this prospectus.

You should rely only on the information contained in or incorporated by reference in this prospectus, any accompanying prospectus supplement or in any related free writing prospectus filed by us with the SEC. We have not authorized anyone to provide you with different information. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the securities described in this prospectus or such accompanying prospectus supplement or an offer to sell or the solicitation of an offer to buy such securities in any circumstances in which such offer or solicitation is unlawful. You should assume that the information appearing in this prospectus, any prospectus supplement, the documents incorporated by reference and any related free writing prospectus is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed materially since those dates.

Unless the context otherwise indicates, references in this prospectus to “we,” “our” and “us” refer, collectively, to Tetraphase Pharmaceuticals, Inc., a Delaware corporation, and its consolidated subsidiaries.

RISK FACTORS

Investing in our securities involves a high degree of risk. You should carefully consider the risks and uncertainties described in this prospectus and any accompanying prospectus supplement, including the risk factors set forth in our filings with the SEC that are incorporated by reference herein, including the risk factors in our Quarterly Report on Form 10-Q for the fiscal quarter ended September 30, 2017, before making an investment decision pursuant to this prospectus and any accompanying prospectus supplement relating to a specific offering.

Our business, financial condition and results of operations could be materially and adversely affected by any or all of these risks or by additional risks and uncertainties not presently known to us or that we currently deem immaterial that may adversely affect us in the future.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov. Copies of certain information filed by us with the SEC are also available on our website at www.tphase.com. Our website is not a part of this prospectus and is not incorporated by reference in this prospectus. You may also read and copy any document we file at the SEC’s Public Reference Room, 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the operation of the Public Reference Room.

This prospectus is part of a registration statement we filed with the SEC. This prospectus omits some information contained in the registration statement in accordance with SEC rules and regulations. You should review the information and exhibits in the registration statement for further information about us and our consolidated subsidiaries and the securities we are offering. Statements in this prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings. You should review the complete document to evaluate these statements. You can obtain a copy of the registration statement from the SEC at the address listed above or the SEC’s website.

INCORPORATION BY REFERENCE

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus is considered to be part of this prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus or in any document previously incorporated by reference have been modified or superseded.

This prospectus incorporates by reference the documents listed below (File No. 000-35837) and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act (in each case, other than those documents or the portions of those documents not deemed to be filed) between the date of the initial registration statement and the effectiveness of the registration statement and following the effectiveness of the registration statement until the offering of the securities under the registration statement is terminated or completed:

•

Our Annual Report on Form 10-K for the fiscal year ended December 31, 2016, including the information specifically incorporated by reference into the Annual Report on Form 10-K from our definitive Proxy Statement on Schedule 14A filed in connection with our 2017 annual meeting of stockholders;

•

Our Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31, 2017, June 30, 2017 and September 30, 2017;

•

Our Current Reports on Form 8-K filed with the SEC on each of January 17, 2017, February 3, 2017, April 3, 2017, June 2, 2017, June 20, 2017, July 7, 2017, July 25, 2017, July 28, 2017, October 20, 2017, December 4, 2017, January 5, 2018 and January 23, 2018;

•

The description of our common stock contained in our Registration Statement on Form 8-A filed with the SEC on March 15, 2013, including any amendments or reports filed for the purpose of updating such description.

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address or phone number:

Tetraphase Pharmaceuticals, Inc.

480 Arsenal Way

Watertown, MA 02472

Attn: Investor Relations

(617) 715-3600

FORWARD-LOOKING STATEMENTS

This prospectus and the information incorporated by reference in this prospectus include forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. Such forward-looking statements include statements about our plans and strategy for our business, the possible achievement of discovery and development goals and milestones, our future discovery and development efforts, our collaborations, our future operating results and financial position, and other objectives for future operations. We often use words such as “anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,” “plan,” “predict,” “project,” “seek,” “target,” “goal,” “potential,” “will,” “would,” “could,” “should,” “continue,” and other words and terms of similar meaning to help identify forward-looking statements, although not all forward-looking statements contain these identifying words. You also can identify them by the fact that they do not relate strictly to historical or current facts. There are a number of important risks and uncertainties that could cause actual results or events to differ materially from those indicated by forward-looking statements. These risks and uncertainties include those inherent in pharmaceutical research and development, such as adverse results in our drug discovery and clinical development activities, decisions made by the U.S. Food and Drug Administration and other regulatory authorities with respect to the development and commercialization of our product candidates, our ability to obtain, maintain and enforce intellectual property rights for our drug candidates, competition, our ability to obtain any necessary financing to conduct our planned activities, and other risk factors that are referenced in the section of any accompanying prospectus supplement entitled “Risk Factors.” You should also carefully review the risk factors and cautionary statements described in the other documents we file from time to time with the SEC, specifically our most recent Annual Report on Form 10-K, our Quarterly Reports on Form 10-Q and our Current Reports on Form 8-K. We undertake no obligation to revise or update any forward-looking statements except to the extent required by law.

TETRAPHASE PHARMACEUTICALS, INC.

Our Business

We are a clinical-stage biopharmaceutical company using our proprietary chemistry technology to create novel antibiotics for serious and life-threatening multidrug-resistant infections. We are developing our lead product candidate, eravacycline, a fully-synthetic fluorocycline, as an intravenous, or IV, and oral antibiotic for use as a first-line empiric monotherapy for the treatment of multidrug-resistant infections, including multidrug-resistant, or MDR, Gram-negative infections.

We are conducting a global phase 3 clinical program for eravacycline called IGNITE (Investigating Gram-Negative Infections Treated with Eravacycline). We are also pursuing the discovery and development of additional antibiotics that target unmet medical needs, including multidrug-resistant Gram-negative bacteria.

On July 25, 2017, we announced top-line data from our IGNITE4 trial, a global phase 3 randomized, double-blind, double-dummy, multicenter, prospective study assessing the efficacy, safety and pharmacokinetics of twice-daily IV eravacycline (1.0 mg/kg every 12 hours) compared with meropenem (1g every 8 hours) for the treatment of complicated intra-abdominal infections, or cIAI, that we conducted in 500 patients. In the trial, eravacycline met the primary endpoint of statistical non-inferiority of clinical response at the test-of-cure, or TOC, visit, under the guidance set by the United States Food and Drug Administration, or FDA, and the European Medicines Agency, or EMA. Prior to IGNITE 4, we conducted IGNITE1, a phase 3 clinical trial of twice daily IV eravacycline (1.0 mg/kg every 12 hours) compared with ertapenem (1.0g IV every 24 hours) for the treatment of cIAI. In IGNITE1, eravacycline met the primary endpoint of statistical non-inferiority of clinical response.

In January 2018, we announced the submission of a new drug application, or NDA, for eravacycline for the treatment of cIAI with the FDA based on the positive results observed in both IGNITE1 and IGNITE4. In the third quarter of 2017 we submitted a marketing authorization application, or MAA, to the EMA for IV eravacycline for the treatment of cIAI primarily based upon the results of IGNITE1.

We are also developing eravacycline for the treatment of complicated urinary tract infections, or cUTI. In January 2017, we initiated IGNITE3, a randomized, multi-center, double-blind, phase 3 clinical trial evaluating the efficacy and safety of once-daily IV eravacycline compared to ertapenem, the control therapy in this trial, for the treatment of cUTI. We completed enrollment in IGNITE3 in September 2017 and expect to report top-line data from this trial in the first quarter of 2018. If IGNITE3 is successful, we plan to use the results from IGNITE3 to support submission of a supplemental new drug application, or sNDA, for IV eravacycline for the treatment of cUTI, assuming approval first of IV eravacycline for the treatment of cIAI.

In parallel with the clinical trials using IV eravacycline, we are continuing our development program for an oral formulation of eravacycline. We have identified an optimized IV-to-oral dosing regimen using the current oral formulation which we plan to advance into a phase 2 clinical trial in patients with cUTI.

The FDA has granted Qualified Infectious Disease Product (QIDP) and Fast Track designations for IV and oral eravacycline for cIAI and cUTI.

In June 2017, we announced positive results from a phase 1 single-ascending dose clinical trial of the IV formulation of TP-271, a fully-synthetic fluorocycline being developed for respiratory disease caused by bacterial biothreat pathogens, in healthy volunteers. We are conducting a multiple-ascending dose trial for the IV formulation of TP-271. We also plan to initiate a multiple-ascending dose phase 1 study for the oral formulation of TP-271 in early 2018. In February 2017, we received Qualified Infectious Disease Product and Fast Track designations from the FDA.

In addition, we are developing TP-6076, a fully-synthetic fluorocycline derivative, as a lead candidate under our second-generation program to target unmet medical needs, including multidrug-resistant Gram-negative

bacteria. In June 2017, we announced positive results from a phase 1 randomized, placebo-controlled, double-blind, single-ascending dose study evaluating the safety, tolerability and pharmacokinetics of IV TP-6076. We also are conducting a multiple-ascending study in healthy volunteers of the IV formulation of TP-6076.

We believe that our proprietary chemistry technology, licensed from Harvard University on an exclusive worldwide basis and enhanced by us, represents a significant innovation in the creation of tetracycline drugs that has the potential to reinvigorate the clinical and market potential of the class. Our proprietary chemistry technology makes it possible to create novel tetracycline antibiotics using a practical, fully synthetic process for what we believe is the first time. This fully synthetic process avoids the limitations of bacterially derived tetracyclines and allows us to chemically modify many positions in the tetracycline scaffold, including most of the positions that we believe could not practically be modified by any previous conventional method. Using our proprietary chemistry technology, we can create a wider variety of tetracycline-based compounds than was previously possible, enabling us to pursue novel tetracycline derivatives for the treatment of multidrug-resistant bacteria that are resistant to existing tetracyclines and other classes of antibiotic products. We own exclusive worldwide rights to these compounds and our technology.

Our principal executive offices are located at 480 Arsenal Way, Watertown, Massachusetts 02472 and our telephone number is (617) 715-3600.

CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES

The following table sets forth, for each of the periods presented, our ratio of earnings to fixed charges and the related coverage deficiency. You should read this table in conjunction with the financial statements and notes incorporated by reference in this prospectus.


(In thousands)	Nine Months Ended September 30, 2017			Years Ended December 31,
	Nine Months Ended September 30, 2017			2016			2015			2014			2013			2012
Net loss	$	(91,276	)	$	(77,480	)	$	(83,189	)	$	(66,742	)	$	(29,636	)	$	(15,087	)
Ratio of earnings to fixed charges(1), (2)		N/A			N/A			N/A			N/A			N/A			N/A
Coverage deficiency	$	(91,276	)	$	(77,480	)	$	(83,189	)	$	(66,742	)	$	(29,636	)	$	(15,087	)

(1)	For purposes of calculating the ratio of earnings to fixed charges, earnings consist of net income (loss) from continuing operations before income taxes, plus fixed charges. Fixed charges include interest expense and the estimated interest component of rental expense.

(2)

We did not record earnings for the nine months ended September 30, 2017 or for the years ended December 31, 2016, 2015, 2014, 2013 and 2012. Accordingly, our earnings were insufficient to cover fixed charges for such periods and we are unable to disclose a ratio of earnings to fixed charges for such periods.

USE OF PROCEEDS

We intend to use the net proceeds from the sale of any securities offered under this prospectus for general corporate purposes unless otherwise indicated in the applicable prospectus supplement. General corporate purposes may include working capital and capital expenditures, research and development expenses, including clinical trial costs, general and administrative expenses, potential acquisition of, or investment in, companies, technologies, products or assets that complement our business, and repayment and refinancing of debt. We may temporarily invest the net proceeds in investment-grade, interest-bearing securities until they are used for their stated purpose. We have not determined the amount of net proceeds to be used specifically for such purposes. As a result, management will retain broad discretion over the allocation of net proceeds.

DESCRIPTION OF DEBT SECURITIES

We may offer debt securities which may be senior or subordinated. We refer to the senior debt securities and the subordinated debt securities collectively as debt securities. The following description summarizes the general terms and provisions of the debt securities. We will describe the specific terms of the debt securities and the extent, if any, to which the general provisions summarized below apply to any series of debt securities in the prospectus supplement relating to the series and any applicable free writing prospectus that we authorize to be delivered. When we refer to “the Company,” “we,” “our,” and “us” in this section, we mean Tetraphase Pharmaceuticals, Inc., excluding, unless the context otherwise requires or as otherwise expressly stated, our subsidiaries.

We may issue senior debt securities from time to time, in one or more series under a senior indenture to be entered into between us and a senior trustee to be named in a prospectus supplement, which we refer to as the senior trustee. We may issue subordinated debt securities from time to time, in one or more series under a subordinated indenture to be entered into between us and a subordinated trustee to be named in a prospectus supplement, which we refer to as the subordinated trustee. The forms of senior indenture and subordinated indenture are filed as exhibits to the registration statement of which this prospectus forms a part. Together, the senior indenture and the subordinated indenture are referred to as the indentures and, together, the senior trustee and the subordinated trustee are referred to as the trustees. This prospectus briefly outlines some of the provisions of the indentures. The following summary of the material provisions of the indentures is qualified in its entirety by the provisions of the indentures, including definitions of certain terms used in the indentures. Wherever we refer to particular sections or defined terms of the indentures, those sections or defined terms are incorporated by reference in this prospectus or the applicable prospectus supplement. You should review the indentures that are filed as exhibits to the registration statement of which this prospectus forms a part for additional information.

None of the indentures will limit the amount of debt securities that we may issue. The applicable indenture will provide that debt securities may be issued up to an aggregate principal amount authorized from time to time by us and may be payable in any currency or currency unit designated by us or in amounts determined by reference to an index.

General

The senior debt securities will constitute our unsubordinated general obligations and will rank pari passu with our other unsubordinated obligations. The subordinated debt securities will constitute our subordinated general obligations and will be junior in right of payment to our senior indebtedness (including senior debt securities), as described under the heading “—Certain Terms of the Subordinated Debt Securities—Subordination.” The debt securities will be structurally subordinated to all existing and future indebtedness and other liabilities of our subsidiaries unless such subsidiaries expressly guarantee such debt securities.

The debt securities will be our unsecured obligations unless otherwise specified in the applicable prospectus supplement. Any secured debt or other secured obligations will be effectively senior to the debt securities to the extent of the value of the assets securing such debt or other obligations.

The applicable prospectus supplement and/or free writing prospectus will include any additional or different terms of the debt securities being offered, including the following terms:

•

the title and type of the debt securities;

•

whether the debt securities will be senior or subordinated debt securities, and, with respect to debt securities issued under the subordinated indenture the terms on which they are subordinated;

•

the aggregate principal amount of the debt securities;

•

the price or prices at which we will sell the debt securities;

•

the maturity date or dates of the debt securities and the right, if any, to extend such date or dates;

•

the rate or rates, if any, per year, at which the debt securities will bear interest, or the method of determining such rate or rates;

•

the date or dates from which such interest will accrue, the interest payment dates on which such interest will be payable or the manner of determination of such interest payment dates and the related record dates;

•

the right, if any, to extend the interest payment periods and the duration of that extension;

•

the manner of paying principal and interest and the place or places where principal and interest will be payable;

•

provisions for a sinking fund, purchase fund or other analogous fund, if any;

•

any redemption dates, prices, obligations and restrictions on the debt securities;

•

the currency, currencies or currency units in which the debt securities will be denominated and the currency, currencies or currency units in which principal and interest, if any, on the debt securities may be payable;

•

any conversion or exchange features of the debt securities;

•

whether and upon what terms the debt securities may be defeased;

•

any events of default or covenants in addition to or in lieu of those set forth in the indenture;

•

whether the debt securities will be issued in definitive or global form or in definitive form only upon satisfaction of certain conditions;

•

whether the debt securities will be guaranteed as to payment or performance;

•

whether the debt securities will be secured by any collateral and, if so, a general description of the collateral and the terms and provisions of such collateral, security, pledge or other related agreements;

•

any material tax implications of the debt securities; and

•

any other material terms of the debt securities.

When we refer to “principal” in this section with reference to the debt securities, we are also referring to “premium, if any.”

We may from time to time, without notice to or the consent of the holders of any series of debt securities, create and issue further debt securities of any such series ranking equally with the debt securities of such series in all respects (or in all respects other than (1) the payment of interest accruing prior to the issue date of such further debt securities or (2) the first payment of interest following the issue date of such further debt securities). Such further debt securities may be consolidated and form a single series with the debt securities of such series and have the same terms as to status, redemption or otherwise as the debt securities of such series.

You may present debt securities for exchange and you may present debt securities for transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the applicable prospectus supplement.

We will provide you those services without charge, although you may have to pay any tax or other governmental charge payable in connection with any exchange or transfer, as set forth in the indenture.

Debt securities may bear interest at a fixed rate or a floating rate. Debt securities bearing no interest or interest at a rate that at the time of issuance is below the prevailing market rate (original issue discount securities) may be sold at a discount below their stated principal amount. U.S. federal income tax considerations applicable to any such discounted debt securities or to certain debt securities issued at par which are treated as having been issued at a discount for U.S. federal income tax purposes will be described in the applicable prospectus supplement.

We may issue debt securities with the principal amount payable on any principal payment date, or the amount of interest payable on any interest payment date, to be determined by reference to one or more currency exchange rates, securities or baskets of securities, commodity prices or indices. You may receive a payment of principal on any principal payment date, or a payment of interest on any interest payment date, that is greater than or less than the amount of principal or interest otherwise payable on such dates, depending on the value on such dates of the applicable currency, security or basket of securities, commodity or index. Information as to the methods for determining the amount of principal or interest payable on any date, the currencies, securities or baskets of securities, commodities or indices to which the amount payable on such date is linked and certain related tax considerations will be set forth in the applicable prospectus supplement.

Certain Terms of the Senior Debt Securities

Covenants. Unless we indicate otherwise in a prospectus supplement, the senior debt securities will not contain any financial or restrictive covenants, including covenants restricting either us or any of our subsidiaries from incurring, issuing, assuming or guaranteeing any indebtedness secured by a lien on any of our or our subsidiaries’ property or capital stock, or restricting either us or any of our subsidiaries from entering into sale and leaseback transactions.

Consolidation, Merger and Sale of Assets. Unless we indicate otherwise in a prospectus supplement, we may not consolidate with or merge into any other person, in a transaction in which we are not the surviving corporation, or convey, transfer or lease our properties and assets substantially as an entirety to any person, in either case, unless:

•

the successor entity, if any, is a U.S. corporation, limited liability company, partnership or trust (subject to certain exceptions provided for in the senior indenture);

•

the successor entity assumes our obligations on the senior debt securities and under the senior indenture;

•

immediately after giving effect to the transaction, no default or event of default shall have occurred and be continuing; and

•

certain other conditions are met.

No Protection in the Event of a Change in Control. Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the senior debt securities will not contain any provisions that may afford holders of the senior debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control).

Events of Default. Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the following are events of default under the senior indenture for any series of senior debt securities:

•

failure to pay interest on any senior debt securities of such series when due and payable, if that default continues for a period of 90 days (or such other period as may be specified for such series);

•

failure to pay principal on the senior debt securities of such series when due and payable whether at maturity, upon redemption, by declaration or otherwise (and, if specified for such series, the continuance of such failure for a specified period);

•

default in the performance of or breach of any of our covenants or agreements in the senior indenture applicable to senior debt securities of such series, other than a covenant breach which is specifically dealt with elsewhere in the senior indenture, and that default or breach continues for a period of 90 days after we receive written notice from the trustee or from the holders of 25% or more in aggregate principal amount of the senior debt securities of such series;

•

certain events of bankruptcy or insolvency, whether or not voluntary; and

•

any other event of default provided for in such series of senior debt securities as may be specified in the applicable prospectus supplement.

The default by us under any other debt, including any other series of debt securities, is not a default under the senior indenture.

If an event of default other than an event of default specified in the fourth bullet point above occurs with respect to a series of senior debt securities and is continuing under the senior indenture, then, and in each such case, either the trustee or the holders of not less than 25% in aggregate principal amount of such series then outstanding under the senior indenture (each such series voting as a separate class) by written notice to us and to the trustee, if such notice is given by the holders, may, and the trustee at the request of such holders shall, declare the principal amount of and accrued interest on such series of senior debt securities to be immediately due and payable, and upon this declaration, the same shall become immediately due and payable.

If an event of default specified in the fourth bullet point above occurs with respect to us and is continuing, the entire principal amount of and accrued interest, if any, on each series of senior debt securities then outstanding shall become immediately due and payable.

Unless otherwise specified in the prospectus supplement relating to a series of senior debt securities originally issued at a discount, the amount due upon acceleration shall include only the original issue price of the senior debt securities, the amount of original issue discount accrued to the date of acceleration and accrued interest, if any.

Upon certain conditions, declarations of acceleration may be rescinded and annulled and past defaults may be waived by the holders of a majority in aggregate principal amount of all the senior debt securities of such series affected by the default, each series voting as a separate class. Furthermore, subject to various provisions in the senior indenture, the holders of a majority in aggregate principal amount of a series of senior debt securities, by notice to the trustee, may waive an existing default or event of default with respect to such senior debt securities and its consequences, except a default in the payment of principal of or interest on such senior debt securities or in respect of a covenant or provision of the senior indenture which cannot be modified or amended without the consent of the holders of each such senior debt security. Upon any such waiver, such default shall cease to exist, and any event of default with respect to such senior debt securities shall be deemed to have been cured, for every purpose of the senior indenture; but no such waiver shall extend to any subsequent or other default or event of default or impair any right consequent thereto.

The holders of a majority in aggregate principal amount of a series of senior debt securities may direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any

trust or power conferred on the trustee with respect to such senior debt securities. However, the trustee may refuse to follow any direction that conflicts with law or the senior indenture, that may involve the trustee in personal liability or that the trustee determines in good faith may be unduly prejudicial to the rights of holders of such series of senior debt securities not joining in the giving of such direction and may take any other action it deems proper that is not inconsistent with any such direction received from holders of such series of senior debt securities. A holder may not pursue any remedy with respect to the senior indenture or any series of senior debt securities unless:

•

the holder gives the trustee written notice of a continuing event of default;

•

the holders of at least 25% in aggregate principal amount of such series of senior debt securities make a written request to the trustee to pursue the remedy in respect of such event of default;

•

the requesting holder or holders offer the trustee indemnity satisfactory to the trustee against any costs, liability or expense;

•

the trustee does not comply with the request within 60 days after receipt of the request and the offer of indemnity; and

•

during such 60-day period, the holders of a majority in aggregate principal amount of such series of senior debt securities do not give the trustee a direction that is inconsistent with the request.

These limitations, however, do not apply to the right of any holder of a senior debt security to receive payment of the principal of and interest, if any, on such senior debt security in accordance with the terms of such debt security, or to bring suit for the enforcement of any such payment in accordance with the terms of such debt security, on or after the due date for the senior debt securities, which right shall not be impaired or affected without the consent of the holder.

The senior indenture requires certain of our officers to certify, on or before a fixed date in each year in which any senior debt security is outstanding, as to their knowledge of our compliance with all covenants, agreements and conditions under the senior indenture.

Satisfaction and Discharge. We can satisfy and discharge our obligations to holders of any series of debt securities if:

•

we pay or cause to be paid, as and when due and payable, the principal of and any interest on all senior debt securities of such series outstanding under the senior indenture; or

•

all senior debt securities of such series have become due and payable or will become due and payable within one year (or are to be called for redemption within one year) and we deposit in trust a combination of cash and U.S. government or U.S. government agency obligations that will generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

Under current U.S. federal income tax law, the deposit and our legal release from the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give back to us. Purchasers of the debt securities should consult their own advisers with respect to the tax consequences to them of such deposit and discharge, including the applicability and effect of tax laws other than the U.S. federal income tax law.

Defeasance. Unless the applicable prospectus supplement provides otherwise, the following discussion of legal defeasance and discharge and covenant defeasance will apply to any series of debt securities issued under the indentures.

Legal Defeasance. We can legally release ourselves from any payment or other obligations on the debt securities of any series (called “legal defeasance”) if certain conditions are met, including the following:

•

We deposit in trust for your benefit and the benefit of all other direct holders of the debt securities of the same series a combination of cash and U.S. government or U.S. government agency obligations that will generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

•

There is a change in current U.S. federal income tax law or an IRS ruling that lets us make the above deposit without causing you to be taxed on the debt securities any differently than if we did not make the deposit and instead repaid the debt securities ourselves when due. Under current U.S. federal income tax law, the deposit and our legal release from the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give back to us.

•

We deliver to the trustee a legal opinion of our counsel confirming the tax law change or ruling described above.

If we accomplish legal defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the debt securities. You could not look to us for repayment in the event of any shortfall.

Covenant Defeasance. Without any change of current U.S. federal tax law, we can make the same type of deposit described above and be released from some of the covenants in the debt securities (called “covenant defeasance”). In that event, you would lose the protection of those covenants but would gain the protection of having money and securities set aside in trust to repay the debt securities. In order to achieve covenant defeasance, we must do the following (among other things):

•

We must deposit in trust for your benefit and the benefit of all other direct holders of the debt securities of the same series a combination of cash and U.S. government or U.S. government agency obligations that will generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

•

We must deliver to the trustee a legal opinion of our counsel confirming that under current U.S. federal income tax law we may make the above deposit without causing you to be taxed on the debt securities any differently than if we did not make the deposit and instead repaid the debt securities ourselves when due.

If we accomplish covenant defeasance, you could still look to us for repayment of the debt securities if there were a shortfall in the trust deposit. In fact, if one of the events of default occurred (such as our bankruptcy) and the debt securities become immediately due and payable, there may be such a shortfall. Depending on the events causing the default, you may not be able to obtain payment of the shortfall.

Modification and Waiver. We and the trustee may amend or supplement the senior indenture or the senior debt securities without the consent of any holder:

•

to convey, transfer, assign, mortgage or pledge any assets as security for the senior debt securities of one or more series;

•

to evidence the succession of a corporation, limited liability company, partnership or trust to us, and the assumption by such successor of our covenants, agreements and obligations under the senior indenture or to otherwise comply with the covenant relating to mergers, consolidations and sales of assets;

•

to comply with the requirements of the SEC in order to effect or maintain the qualification of the senior indenture under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act;

•

to add to our covenants such new covenants, restrictions, conditions or provisions for the protection of the holders, and to make the occurrence, or the occurrence and continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default;

•

to cure any ambiguity, defect or inconsistency in the senior indenture or in any supplemental indenture or to conform the senior indenture or the senior debt securities to the description of senior debt securities of such series set forth in this prospectus or any applicable prospectus supplement;

•

to provide for or add guarantors with respect to the senior debt securities of any series;

•

to establish the form or forms or terms of the senior debt securities as permitted by the senior indenture;

•

to evidence and provide for the acceptance of appointment under the senior indenture by a successor trustee, or to make such changes as shall be necessary to provide for or facilitate the administration of the trusts in the senior indenture by more than one trustee;

•

to add to, delete from or revise the conditions, limitations and restrictions on the authorized amount, terms, purposes of issue, authentication and delivery of any series of senior debt securities;

•

to make any change to the senior debt securities of any series so long as no senior debt securities of such series are outstanding; or

•

to make any change that does not adversely affect the rights of any holder in any material respect.

Other amendments and modifications of the senior indenture or the senior debt securities issued may be made, and our compliance with any provision of the senior indenture with respect to any series of senior debt securities may be waived, with the consent of the holders of a majority of the aggregate principal amount of the outstanding senior debt securities of all series affected by the amendment or modification (voting together as a single class); provided, however, that each affected holder must consent to any modification, amendment or waiver that:

•

extends the final maturity of any senior debt securities of such series;

•

reduces the principal amount of any senior debt securities of such series;

•

reduces the rate or extends the time of payment of interest on any senior debt securities of such series;

•

reduces the amount payable upon the redemption of any senior debt securities of such series;

•

changes the currency of payment of principal of or interest on any senior debt securities of such series;

•

reduces the principal amount of original issue discount securities payable upon acceleration of maturity or the amount provable in bankruptcy;

•

waives an uncured default in the payment of principal of or interest on the senior debt securities (except in the case of a rescission of acceleration as described above);

•

changes the provisions relating to the waiver of past defaults or changes or impairs the right of holders to receive payment or to institute suit for the enforcement of any payment or conversion of any senior debt securities of such series on or after the due date therefor;

•

modifies any of the provisions of these restrictions on amendments and modifications, except to increase any required percentage or to provide that certain other provisions cannot be modified or waived without the consent of the holder of each senior debt security of such series affected by the modification; or

•

reduces the above-stated percentage of outstanding senior debt securities of such series whose holders must consent to a supplemental indenture or modifies, amends or waives certain provisions of or defaults under the senior indenture.

It shall not be necessary for the holders to approve the particular form of any proposed amendment, supplement or waiver, but it shall be sufficient if the holders’ consent approves the substance thereof. After an amendment, supplement or waiver of the senior indenture in accordance with the provisions described in this section becomes effective, the trustee must give to the holders affected thereby certain notice briefly describing the amendment, supplement or waiver. Any failure by the trustee to give such notice, or any defect therein, shall not, however, in any way impair or affect the validity of any such amendment, supplemental indenture or waiver.

No Personal Liability of Incorporators, Stockholders, Officers, Directors. The senior indenture provides that no recourse shall be had under any obligation, covenant or agreement of ours in the senior indenture or any supplemental indenture, or in any of the senior debt securities or because of the creation of any indebtedness represented thereby, against any of our incorporators, stockholders, officers or directors, past, present or future, or of any predecessor or successor entity thereof under any law, statute or constitutional provision or by the enforcement of any assessment or by any legal or equitable proceeding or otherwise. Each holder, by accepting the senior debt securities, waives and releases all such liability.

Concerning the Trustee. The senior indenture provides that, except during the continuance of an event of default, the trustee will not be liable except for the performance of such duties as are specifically set forth in the senior indenture. If an event of default has occurred and is continuing, the trustee will exercise such rights and powers vested in it under the senior indenture and will use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person’s own affairs.

The senior indenture and the provisions of the Trust Indenture Act incorporated by reference therein contain limitations on the rights of the trustee thereunder, should it become a creditor of ours or any of our subsidiaries, to obtain payment of claims in certain cases or to realize on certain property received by it in respect of any such claims, as security or otherwise. The trustee is permitted to engage in other transactions, provided that if it acquires any conflicting interest (as defined in the Trust Indenture Act), it must eliminate such conflict or resign.

We may have normal banking relationships with the senior trustee in the ordinary course of business.

Unclaimed Funds. All funds deposited with the trustee or any paying agent for the payment of principal, premium, interest or additional amounts in respect of the senior debt securities that remain unclaimed for two years after the date upon which such principal, premium or interest became due and payable will be repaid to us. Thereafter, any right of any holder of senior debt securities to such funds shall be enforceable only against us, and the trustee and paying agents will have no liability therefor.

Governing Law. The senior indenture and the senior debt securities will be governed by, and construed in accordance with, the internal laws of the State of New York.

Certain Terms of the Subordinated Debt Securities

Other than the terms of the subordinated indenture and subordinated debt securities relating to subordination or otherwise as described in the prospectus supplement relating to a particular series of subordinated debt securities, the terms of the subordinated indenture and subordinated debt securities are identical in all material respects to the terms of the senior indenture and senior debt securities.

Additional or different subordination terms may be specified in the prospectus supplement applicable to a particular series.

Subordination. The indebtedness evidenced by the subordinated debt securities is subordinate to the prior payment in full of all of our senior indebtedness, as defined in the subordinated indenture. During the continuance beyond any applicable grace period of any default in the payment of principal, premium, interest or any other payment due on any of our senior indebtedness, we may not make any payment of principal of or

interest on the subordinated debt securities (except for certain sinking fund payments). In addition, upon any payment or distribution of our assets upon any dissolution, winding-up, liquidation or reorganization, the payment of the principal of and interest on the subordinated debt securities will be subordinated to the extent provided in the subordinated indenture in right of payment to the prior payment in full of all our senior indebtedness. Because of this subordination, if we dissolve or otherwise liquidate, holders of our subordinated debt securities may receive less, ratably, than holders of our senior indebtedness. The subordination provisions do not prevent the occurrence of an event of default under the subordinated indenture.

The term “senior indebtedness” of a person means with respect to such person the principal of, premium, if any, interest on, and any other payment due pursuant to any of the following, whether outstanding on the date of the subordinated indenture or incurred by that person in the future:

•

all of the indebtedness of that person for money borrowed;

•

all of the indebtedness of that person evidenced by notes, debentures, bonds or other securities sold by that person for money;

•

all of the lease obligations that are capitalized on the books of that person in accordance with generally accepted accounting principles;

•

all indebtedness of others of the kinds described in the first two bullet points above and all lease obligations of others of the kind described in the third bullet point above that the person, in any manner, assumes or guarantees or that the person in effect guarantees through an agreement to purchase, whether that agreement is contingent or otherwise; and

•

all renewals, extensions or refundings of indebtedness of the kinds described in the first, second or fourth bullet point above and all renewals or extensions of leases of the kinds described in the third or fourth bullet point above;

unless, in the case of any particular indebtedness, renewal, extension or refunding, the instrument creating or evidencing it or the assumption or guarantee relating to it expressly provides that such indebtedness, renewal, extension or refunding is not superior in right of payment to the subordinated debt securities. Our senior debt securities constitute senior indebtedness for purposes of the subordinated debt indenture.

DESCRIPTION OF CAPITAL STOCK

The following description of our capital stock is intended as a summary only and therefore is not a complete description of our capital stock. This description is based upon, and is qualified by reference to, our certificate of incorporation, our bylaws and applicable provisions of Delaware corporate law. You should read our certificate of incorporation and bylaws, which are filed as exhibits to the registration statement, of which this prospectus forms a part, for the provisions that are important to you.

Our authorized capital stock consists of 125,000,000 shares of common stock, par value $0.001 per share, and 5,000,000 shares of preferred stock, par value $0.001 per share, all of which preferred stock is undesignated. The following description of our capital stock and provisions of our restated certificate of incorporation and bylaws are summaries and are qualified by reference to our certificate of incorporation and bylaws. Copies of these documents are filed with the SEC as exhibits to our Quarterly Report on Form 10-Q filed with the SEC on May 13, 2013.

Common Stock

As of January 24, 2018, we had outstanding 51,594,848 shares of common stock, held of record by 8 stockholders. We believe that the number of beneficial owners of our common stock at that date was substantially greater.

Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of stockholders and do not have cumulative voting rights. An election of directors by our stockholders shall be determined by a plurality of the votes cast by the stockholders entitled to vote on the election. In general, except (1) for the election of directors, (2) as described below under “—Anti-Takeover Effects of Delaware Law and Our Charter and Bylaws”, (3) in the future to the extent that we have two or more classes or series of stock outstanding with separate voting rights and (4) as otherwise required by law, any matter to be voted on by our stockholders at any meeting, shall be decided by the affirmative vote of our stockholders having a majority in voting power of the votes cast by the stockholders present or represented and voting on such matter.

Holders of common stock are entitled to receive proportionately any dividends as may be declared by our board of directors, subject to any preferential dividend rights of our outstanding preferred stock.

In the event of our liquidation or dissolution, the holders of common stock are entitled to receive proportionately all assets available for distribution to stockholders after the payment of all debts and other liabilities and subject to the prior rights of any of our outstanding preferred stock.

Holders of common stock have no preemptive, subscription, redemption or conversion rights. The rights, preferences and privileges of holders of our common stock are subject to and may be adversely affected by the rights of the holders of shares of any series of our preferred stock that we may designate and issue in the future.

Listing on The NASDAQ Global Market

Our common stock is listed on The NASDAQ Global Market under the symbol “TTPH.”

Authorized but Unissued Shares

The authorized but unissued shares of common stock are available for future issuance without stockholder approval, subject to any limitations imposed by the NASDAQ Listing Rules. These additional shares may be used for a variety of corporate finance transactions, acquisitions and employee benefit plans. The existence of authorized but unissued and unreserved common stock could make it more difficult or discourage an attempt to obtain control of us by means of a proxy contest, tender offer, merger or otherwise.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company, LLC.

Preferred Stock

Under the terms of our certificate of incorporation, our board of directors is authorized to issue 5,000,000 shares of preferred stock, par value $0.001 per share, in one or more series without stockholder approval. Our board of directors has the discretion to determine the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, of each series of preferred stock.

If we decide to issue any preferred stock pursuant to this prospectus, we will describe in a prospectus supplement the specific terms of the preferred stock, including, if applicable, the following:

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the title and stated value;

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the number of shares we are offering;

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the liquidation preference per share;

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the purchase price;

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the dividend rate, period and payment date, and method of calculation for dividends;

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whether dividends will be cumulative and, if cumulative, the date from which dividends will accumulate;

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the relative ranking and preference of the preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs

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the procedures for any auction and remarketing;

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the provisions for a sinking fund;

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the provisions for redemption or repurchase and any restrictions on our ability to exercise those redemption and repurchase rights;

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the listing of the preferred stock on any securities exchange or market;

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whether the preferred stock will be convertible into our common stock and, if convertible, the conversion price, or how it will be calculated, and the conversion period;

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whether the preferred stock will be exchangeable into debt securities and, if exchangeable, the exchange price, or how it will be calculated, and the exchange period;

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voting rights of the preferred stock;

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preemptive rights;

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restrictions on transfer, sale or other assignment;

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whether interests in the preferred stock will be represented by depositary shares;

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a discussion of any material U.S. federal income tax considerations applicable to the preferred stock;

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any limitations on issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs; and

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any other specific terms, preferences, rights or limitations of, or restrictions on, the preferred stock.

The preferred stock could have other rights, including economic rights that are senior to our common stock that could adversely affect the market value of our common stock. The issuance of the preferred stock may also have the effect of delaying, deferring or preventing a change in control of us without any action by the shareholders.

Anti-Takeover Effects of Delaware Law and Our Charter and Bylaws

Delaware law, our certificate of incorporation and our bylaws contain provisions that could have the effect of delaying, deferring or discouraging another party from acquiring control of us. These provisions, which are summarized below, are expected to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors.

Staggered Board; Removal of Directors

Our certificate of incorporation and bylaws divide our board of directors into three classes with staggered three-year terms. In addition, a director may be removed only for cause and only by the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in an annual election of directors. Any vacancy on our board of directors, including a vacancy resulting from an enlargement of our board of directors, may be filled only by vote of a majority of our directors then in office. The classification of our board of directors and the limitations on the removal of directors and filling of vacancies could make it more difficult for a third party to acquire, or discourage a third party from seeking to acquire, control of our company.

Stockholder Action by Written Consent; Special Meetings

Our certificate of incorporation provides that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of such holders and may not be effected by any consent in writing by such holders. Our certificate of incorporation and bylaws also provide that, except as otherwise required by law, special meetings of our stockholders can only be called by our chairman of the board, our chief executive officer or our board of directors.

Advance Notice Requirements for Stockholder Proposals

Our bylaws establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of stockholders, including proposed nominations of persons for election to our board of directors. Stockholders at an annual meeting may only consider proposals or nominations specified in the notice of meeting or brought before the meeting by or at the direction of our board of directors or by a stockholder of record on the record date for the meeting who is entitled to vote at the meeting and who has delivered timely written notice in proper form to our secretary of the stockholder’s intention to bring such business before the meeting. These provisions could have the effect of delaying until the next stockholder meeting stockholder actions that are favored by the holders of a majority of our outstanding voting securities. These provisions could also discourage a third party from making a tender offer for our common stock, because even if it acquired a majority of our outstanding voting stock, it would be able to take action as a stockholder, such as electing new directors or approving a merger, only at a duly called stockholders meeting and not by written consent.

Delaware Business Combination Statute

Section 203 of the General Corporation Law of the State of Delaware, which we refer to as the DGCL, is applicable to us. Section 203 of the DGCL restricts some types of transactions and business combinations between a corporation and a 15% stockholder. A 15% stockholder is generally considered by Section 203 to be a person owning 15% or more of the corporation’s outstanding voting stock. Section 203 refers to a 15% stockholder as an “interested stockholder.” Section 203 restricts these transactions for a period of three years

from the date the stockholder acquires 15% or more of our outstanding voting stock. With some exceptions, unless the transaction is approved by the board of directors and the holders of at least two-thirds of the outstanding voting stock of the corporation, Section 203 prohibits significant business transactions such as:

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a merger with, disposition of significant assets to or receipt of disproportionate financial benefits by the interested stockholder, and

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any other transaction that would increase the interested stockholder’s proportionate ownership of any class or series of our capital stock.

The shares held by the interested stockholder are not counted as outstanding when calculating the two-thirds of the outstanding voting stock needed for approval.

The prohibition against these transactions does not apply if:

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prior to the time that any stockholder became an interested stockholder, the board of directors approved either the business combination or the transaction in which such stockholder acquired 15% or more of our outstanding voting stock, or

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the interested stockholder owns at least 85% of our outstanding voting stock as a result of a transaction in which such stockholder acquired 15% or more of our outstanding voting stock. Shares held by persons who are both directors and officers or by some types of employee stock plans are not counted as outstanding when making this calculation.

Amendment of Certificate of Incorporation and Bylaws

The Delaware General Corporation Law provides generally that the affirmative vote of a majority of the shares entitled to vote on any matter is required to amend a corporation’s certificate of incorporation or bylaws, unless a corporation’s certificate of incorporation or bylaws, as the case may be, requires a greater percentage. Our bylaws may be amended or repealed by a majority vote of our board of directors or by the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in any annual election of directors. In addition, the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in any annual election of directors is required to amend or repeal or to adopt any provisions inconsistent with any of the provisions of our certificate of incorporation described above under “—Staggered Board; Removal of Directors” and “—Stockholder Action by Written Consent; Special Meetings.”

DESCRIPTION OF WARRANTS

We may issue warrants to purchase common stock, preferred stock or debt securities. We may offer warrants separately or together with one or more additional warrants, common stock, preferred stock or debt securities, or any combination of those securities, as described in the applicable prospectus supplement. The applicable prospectus supplement will also describe the following terms of any warrants:

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the specific designation and aggregate number of, and the offering price at which we will issue, the warrants;

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the currency or currency units in which the offering price, if any, and the exercise price are payable;

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the date on which the right to exercise the warrants will begin and the date on which that right will expire or, if you may not continuously exercise the warrants throughout that period, the specific date or dates on which you may exercise the warrants;

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whether the warrants are to be sold separately or with other securities;

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whether the warrants will be issued in definitive or global form or in any combination of these forms;

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any applicable material U.S. federal income tax consequences;

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the identity of the warrant agent for the warrants and of any other depositaries, execution or paying agents, transfer agents, registrars or other agents;

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the proposed listing, if any, of the warrants or any securities purchasable upon exercise of the warrants on any securities exchange;

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the designation and terms of any equity securities purchasable upon exercise of the warrants;

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the designation, aggregate principal amount, currency and terms of any debt securities that may be purchased upon exercise of the warrants;

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if applicable, the designation and terms of the preferred stock with which the warrants are issued and, the number of warrants issued with each security;

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the number of shares of common stock or preferred stock purchasable upon exercise of a warrant and the price at which those shares may be purchased;

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if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;

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information with respect to book-entry procedures, if any;

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the anti-dilution provisions of, and other provisions for changes to or adjustment in the exercise price of, the warrants, if any;

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any redemption or call provisions; and

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any additional terms of the warrants, including terms, procedures and limitations relating to the exchange or exercise of the warrants.

FORMS OF SECURITIES

Each debt security and warrant will be represented either by a certificate issued in definitive form to a particular investor or by one or more global securities representing the entire issuance of securities. Unless the applicable prospectus supplement provides otherwise, certificated securities in definitive form and global securities will be issued in registered form. Definitive securities name you or your nominee as the owner of the security, and in order to transfer or exchange these securities or to receive payments other than interest or other interim payments, you or your nominee must physically deliver the securities to the trustee, registrar, paying agent or other agent, as applicable. Global securities name a depositary or its nominee as the owner of the debt securities or warrants represented by these global securities. The depositary maintains a computerized system that will reflect each investor’s beneficial ownership of the securities through an account maintained by the investor with its broker/dealer, bank, trust company or other representative, as we explain more fully below.

Global Securities

We may issue the debt securities and warrants in the form of one or more fully registered global securities that will be deposited with a depositary or its nominee identified in the applicable prospectus supplement and registered in the name of that depositary or nominee. In those cases, one or more global securities will be issued in a denomination or aggregate denominations equal to the portion of the aggregate principal or face amount of the securities to be represented by global securities. Unless and until it is exchanged in whole for securities in definitive registered form, a global security may not be transferred except as a whole by and among the depositary for the global security, the nominees of the depositary or any successors of the depositary or those nominees.

If not described below, any specific terms of the depositary arrangement with respect to any securities to be represented by a global security will be described in the prospectus supplement relating to those securities. We anticipate that the following provisions will apply to all depositary arrangements.

Ownership of beneficial interests in a global security will be limited to persons, called participants, that have accounts with the depositary or persons that may hold interests through participants. Upon the issuance of a global security, the depositary will credit, on its book-entry registration and transfer system, the participants’ accounts with the respective principal or face amounts of the securities beneficially owned by the participants. Any dealers, underwriters or agents participating in the distribution of the securities will designate the accounts to be credited. Ownership of beneficial interests in a global security will be shown on, and the transfer of ownership interests will be effected only through, records maintained by the depositary, with respect to interests of participants, and on the records of participants, with respect to interests of persons holding through participants. The laws of some states may require that some purchasers of securities take physical delivery of these securities in definitive form. These laws may impair your ability to own, transfer or pledge beneficial interests in global securities.

So long as the depositary, or its nominee, is the registered owner of a global security, that depositary or its nominee, as the case may be, will be considered the sole owner or holder of the securities represented by the global security for all purposes under the applicable indenture or warrant agreement. Except as described below, owners of beneficial interests in a global security will not be entitled to have the securities represented by the global security registered in their names, will not receive or be entitled to receive physical delivery of the securities in definitive form and will not be considered the owners or holders of the securities under the applicable indenture or warrant agreement. Accordingly, each person owning a beneficial interest in a global security must rely on the procedures of the depositary for that global security and, if that person is not a participant, on the procedures of the participant through which the person owns its interest, to exercise any rights of a holder under the applicable indenture or warrant agreement. We understand that under existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a global security desires to give or take any action that a holder is entitled to give or take under the applicable indenture or warrant

agreement, the depositary for the global security would authorize the participants holding the relevant beneficial interests to give or take that action, and the participants would authorize beneficial owners owning through them to give or take that action or would otherwise act upon the instructions of beneficial owners holding through them.

Principal, premium, if any, and interest payments on debt securities, and any payments to holders with respect to warrants, represented by a global security registered in the name of a depositary or its nominee will be made to the depositary or its nominee, as the case may be, as the registered owner of the global security. None of us, or any trustee, warrant agent or any other agent of ours, or any agent of any trustee or warrant agent will have any responsibility or liability for any aspect of the records relating to payments made on account of beneficial ownership interests in the global security or for maintaining, supervising or reviewing any records relating to those beneficial ownership interests.

We expect that the depositary for any of the securities represented by a global security, upon receipt of any payment to holders of principal, premium, interest or other distribution of underlying securities or other property on that registered global security, will immediately credit participants’ accounts in amounts proportionate to their respective beneficial interests in that global security as shown on the records of the depositary. We also expect that payments by participants to owners of beneficial interests in a global security held through participants will be governed by standing customer instructions and customary practices, as is now the case with the securities held for the accounts of customers or registered in “street name,” and will be the responsibility of those participants.

If the depositary for any of the securities represented by a global security is at any time unwilling or unable to continue as depositary or ceases to be a clearing agency registered under the Exchange Act, and a successor depositary registered as a clearing agency under the Exchange Act is not appointed by us within 90 days, we will issue securities in definitive form in exchange for the global security that had been held by the depositary. Any securities issued in definitive form in exchange for a global security will be registered in the name or names that the depositary gives to the relevant trustee, warrant agent or other relevant agent of ours or theirs. It is expected that the depositary’s instructions will be based upon directions received by the depositary from participants with respect to ownership of beneficial interests in the global security that had been held by the depositary.

PLAN OF DISTRIBUTION

We may sell securities:

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to or through underwriters;

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to or through brokers or dealers;

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through agents;

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directly to one or more purchasers in negotiated sales or competitively bid transactions; or

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through a block trade in which the broker or dealer engaged to handle the block trade will attempt to sell the securities as agent, but may position and resell a portion of the block as principal to facilitate the transaction; or

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through a combination of any of these methods of sale.

In addition, we may issue the securities as a dividend or distribution or in a subscription rights offering to our existing security holders. This prospectus may be used in connection with any offering of our securities through any of these methods or other methods described in the applicable prospectus supplement.

We may directly solicit offers to purchase securities, or agents may be designated to solicit such offers. We will, in the prospectus supplement relating to such offering, name any agent that could be viewed as an underwriter under the Securities Act, and describe any commissions that we must pay. Any such agent will be acting on a best efforts basis for the period of its appointment or, if indicated in the applicable prospectus supplement, on a firm commitment basis.

The distribution of the securities may be effected from time to time in one or more transactions:

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at a fixed price, or prices, which may be changed from time to time;

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at market prices prevailing at the time of sale;

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at prices related to such prevailing market prices; or

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at negotiated prices.

Each prospectus supplement will describe the method of distribution of the securities and any applicable restrictions.

The prospectus supplement with respect to the securities of a particular series will describe the terms of the offering of the securities, including the following:

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the name of the agent or any underwriters;

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the public offering or purchase price and the proceeds we will receive from the sale of the securities;

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any discounts and commissions to be allowed or re-allowed or paid to the agent or underwriters;

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all other items constituting underwriting compensation;

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any discounts and commissions to be allowed or re-allowed or paid to dealers; and

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any exchanges on which the securities will be listed.

If any underwriters or agents are utilized in the sale of the securities in respect of which this prospectus is delivered, we will enter into an underwriting agreement or other agreement with them at the time of sale to them, and we will set forth in the prospectus supplement relating to such offering the names of the underwriters or agents and the terms of the related agreement with them.

If a dealer is utilized in the sale of the securities in respect of which this prospectus is delivered, we will sell such securities to the dealer, as principal. The dealer may then resell such securities to the public at varying prices to be determined by such dealer at the time of resale.

If we offer securities in a subscription rights offering to our existing security holders, we may enter into a standby underwriting agreement with dealers, acting as standby underwriters. We may pay the standby underwriters a commitment fee for the securities they commit to purchase on a standby basis. If we do not enter into a standby underwriting arrangement, we may retain a dealer-manager to manage a subscription rights offering for us.

Remarketing firms, agents, underwriters, dealers and other persons may be entitled under agreements which they may enter into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, and may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

If so indicated in the applicable prospectus supplement, we will authorize underwriters or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in the prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in the prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will not be subject to any conditions except that:

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the purchase by an institution of the securities covered under that contract shall not at the time of delivery be prohibited under the laws of the jurisdiction to which that institution is subject; and

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if the securities are also being sold to underwriters acting as principals for their own account, the underwriters shall have purchased such securities not sold for delayed delivery. The underwriters and other persons acting as our agents will not have any responsibility in respect of the validity or performance of delayed delivery contracts.

Certain agents, underwriters and dealers, and their associates and affiliates may be customers of, have borrowing relationships with, engage in other transactions with, and/or perform services, including investment banking services, for us or one or more of our respective affiliates in the ordinary course of business.

In order to facilitate the offering of the securities, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the securities or any other securities the prices of which may be used to determine payments on such securities. Specifically, any underwriters may overallot in connection with the offering, creating a short position for their own accounts. In addition, to cover overallotments or to stabilize the price of the securities or of any such other securities, the underwriters may bid for, and purchase, the securities or any such other securities in the open market. Finally, in any offering of the securities through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing the securities in the offering if the syndicate repurchases previously distributed securities in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the securities above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

Under Rule 15c6-1 of the Exchange Act, trades in the secondary market generally are required to settle in three business days, unless the parties to any such trade expressly agree otherwise. The applicable prospectus supplement may provide that the original issue date for your securities may be more than three scheduled business days after the trade date for your securities. Accordingly, in such a case, if you wish to trade securities

on any date prior to the third business day before the original issue date for your securities, you will be required, by virtue of the fact that your securities initially are expected to settle in more than three scheduled business days after the trade date for your securities, to make alternative settlement arrangements to prevent a failed settlement.

The securities may be new issues of securities and may have no established trading market. The securities may or may not be listed on a national securities exchange. We can make no assurance as to the liquidity of or the existence of trading markets for any of the securities.

In compliance with the guidelines of the Financial Industry Regulatory Authority, or FINRA, to the extent applicable, the aggregate maximum discount, commission or agency fees or other items constituting underwriting compensation to be received by any FINRA member or independent broker-dealer will not exceed 8% of the proceeds from any offering pursuant to this prospectus and any applicable prospectus supplement.

LEGAL MATTERS

Unless the applicable prospectus supplement indicates otherwise, the validity of the securities in respect of which this prospectus is being delivered will be passed upon by Wilmer Cutler Pickering Hale and Dorr LLP.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2016, and the effectiveness of our internal control over financial reporting as of December 31, 2016, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our consolidated financial statements are incorporated by reference in reliance on Ernst & Young LLP’s reports, given on their authority as experts in accounting and auditing.