DBTX Decibel Therapeutics Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14D-9

SOLICITATION/RECOMMENDATION STATEMENT

UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934

Decibel Therapeutics, Inc.

(Name of Subject Company)

Decibel Therapeutics, Inc.

(Name of Persons Filing Statement)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

24343R 106

(CUSIP Number of Class of Securities)

Laurence Reid, Ph.D.

President and Chief Executive Officer

Decibel Therapeutics, Inc.

1325 Boylston Street, Suite 500

Boston, Massachusetts 02215

(617) 370-8701

(Name, address, and telephone numbers of person authorized to receive notices and communications

on behalf of the persons filing statement)

With copies to:

Stuart M. Falber

Joseph Conahan

Scott N. Lunin

Wilmer Cutler Pickering Hale and Dorr LLP

60 State Street

Boston, Massachusetts 02109

(617) 526-6000

This Schedule 14D-9C relates solely to the below listed preliminary communications made before the commencement of a planned tender offer (the “Offer”) by Regeneron Pharmaceuticals, Inc., a New York corporation (“Parent”) and Symphony Acquisition Sub, Inc., a Delaware corporation (“Purchaser”), to acquire all of the issued and outstanding shares of the common stock, par value $0.001 per share, of Decibel Therapeutics, Inc., a Delaware corporation (the “Company”), to be commenced pursuant to the Agreement and Plan of Merger, dated as of August 8, 2023, by and among Parent, Purchaser and the Company (the “Merger Agreement”). Upon the consummation of the Offer, Purchaser will merge with and into the Company (the “Merger”) pursuant to Section 251(h) of the Delaware General Corporation Law with the Company as the surviving corporation.

Items #1-7 listed above were first used or made available on August  9, 2023. In addition, the information set forth under Items 1.01 and 9.01 of the Current Report on Form 8-K filed by the Company with the U.S. Securities and Exchange Commission (the “SEC”) on August 9, 2023 (including all exhibits attached thereto) is incorporated herein by reference.

Forward-Looking Statements

This filing contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,” variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers will be made; the possibility that various closing conditions for the transaction may not be satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition;

Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this filing and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product Candidates, or Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the SEC, including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this filing has not yet commenced. This filing is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO

and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no expense to them and will also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.

Exhibit 99.2

Email from Laurence Reid to Decibel Therapeutics Employees

Subject: Important Company News

Dear Colleagues,

I am pleased to share with you that today we announced an agreement for Decibel Therapeutics to be acquired by Regeneron Pharmaceuticals, a long-standing collaborator and leading biotechnology company. The press release with full details of this news can be found here [INSERT LINK].

This is a mission-critical evolution for Decibel. It enables us to most fully advance our pipeline of potentially transformative medicines and to build on our existing relationship with Regeneron and the resources they can bring to bear on our pipeline. We are proud of the commitment and passion of the Decibel team and your dedication to our vision of creating a world of connection for people with hearing and balance disorders. We see this as a unique opportunity to accelerate the outstanding work that you have all done together over the last several years and ultimately expand our potential impact on people with severe hearing loss.

We anticipate the transaction to close during the third quarter of 2023. Until the close, we remain an independent company, and we will continue to advance our science in accordance with our ordinary course of business. All of us should remain focused on our day-to-day responsibilities.

I’m sure you will have many questions, which we will begin to address in a town hall meeting at 9:00 a.m. You will also have the opportunity for discussion within your teams, and I and the rest of the management team will be available to answer any further questions you may have.

Thank you for all of your hard work that has brought us to this moment. Congratulations to all of you! Our board and management are convinced and excited about this as a route by which to maximize the impact of your work on the hearing-impaired people who need it!

Best,

Laurence

Forward-Looking Statements

This communication contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,”

variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers will be made; the possibility that various closing conditions for the transaction may not be satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition; Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this communication and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and

other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product Candidates, or Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ

CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no expense to them and will also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.

Exhibit 99.3

Email to Partners

Subject: Exciting update from Decibel Therapeutics

Dear [INSERT NAME],

Today Decibel Therapeutics and Regeneron Pharmaceuticals announced an agreement for Decibel to be acquired by Regeneron, a leading biotechnology company. This enables Decibel to build on our existing, long-standing collaboration with Regeneron to direct extensive support and resources to advance our pipeline of potentially transformative medicines. The press release with full details of this news can be found here [INSERT LINK].

We view this as a momentous event for Decibel and a unique opportunity to accelerate the great work we’ve been doing together with you.

We will have more information to share after the acquisition closes, which is anticipated in the third quarter of 2023, and we expect business to continue as usual until then. We look forward to our continued collaboration with [INSERT ORGANIZATION].

Best,

[INSERT NAME OF SENDER]

Forward-Looking Statements

This communication contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,” variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers will be made; the possibility that various closing conditions for the transaction may not be satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be

integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition; Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this communication and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product Candidates, or Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no expense to them and will also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.

Exhibit 99.4

Email to Advocacy Groups

Subject: Exciting update from Decibel Therapeutics

Hi [INSERT NAME],

I am writing to share an exciting update from Decibel Therapeutics. Today Decibel and Regeneron Pharmaceuticals announced an agreement for Decibel to be acquired by Regeneron, one of our long-standing collaborators and a leading biotechnology company. The press release with full details of this news can be found here [INSERT LINK].

This is a momentous event for Decibel which will provide extensive support and resources to deliver on our mission to create innovative medicines to treat hearing loss and balance disorders. As part of Regeneron, we will also continue our joint efforts with organizations like [INSERT ADVOCACY GROUP] in support of individuals and families in the deaf and hard of hearing community.

We view this news as a unique opportunity to support our work together and don’t anticipate any disruption to our collaboration. We will have more information to share after the acquisition closes, which is anticipated in the third quarter of 2023, and we expect business to continue as usual until then. If you have any questions, please don’t hesitate to reach out.

Best,

[INSERT NAME OF SENDER]

Forward-Looking Statements

This communication contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,” variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers will be made; the possibility that various closing conditions for the transaction may not be satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory

approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition; Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this communication and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product Candidates, or

Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no

expense to them and will also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.

Exhibit 99.5

Email to Clinical Trial Investigators

Subject: Exciting update from Decibel Therapeutics

Hi [INSERT NAME]

Today Decibel Therapeutics and Regeneron Pharmaceuticals announced an agreement for Decibel to be acquired by Regeneron, our longtime collaborator and co-developer of our DB-OTO gene therapy product candidate. The press release with full details of this news can be found here [INSERT LINK].

This is an exciting opportunity for Decibel and for collaborators like you. As part of Regeneron, we will have extensive support and resources to advance our shared purpose to bring transformative treatment options to people with hearing and balance disorders. Importantly, our work to progress the Phase 1/2 CHORD^TM clinical trial of DB-OTO and the ENSEMBLE natural history study will continue as planned, and we are more excited than ever to continue our work together.

We see this as enabling for us to advance our work together and don’t anticipate any disruption to our collaboration. We expect business as usual until the transaction closes in the third quarter of 2023.

We look forward to continuing our work with you and your team. If you have any questions, please reach out.

Best,

[INSERT NAME OF SENDER]

Forward-Looking Statements

This communication contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,” variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers will be made; the possibility that various closing conditions for the transaction may not be

satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition; Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this communication and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and

Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product Candidates, or Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE

TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no expense to them and will also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.

Exhibit 99.6

Announcements by the Company and the Company’s management via LinkedIn on August 9, 2023

On August 9, 2023, Decibel Therapeutics, Inc. (the “Company”) made the following announcements via LinkedIn regarding the proposed acquisition of the Company by Regeneron Pharmaceuticals, Inc., a New York corporation (“Parent”), and proposed merger of the Company with Symphony Acquisition Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Purchaser”), pursuant to the terms of an Agreement and Plan of Merger, dated August 8, 2023, by and among the Company, Parent and Purchaser.

Forward-Looking Statements

This communication contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,” variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers

will be made; the possibility that various closing conditions for the transaction may not be satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition; Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this communication and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s

ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product Candidates, or Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no expense to them and will

also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.

Exhibit 99.7

Announcements by the Company and the Company’s management via X on August 9, 2023

On August 9, 2023, Decibel Therapeutics, Inc. (the “Company”) made the following announcements via X regarding the proposed acquisition of the Company by Regeneron Pharmaceuticals, Inc., a New York corporation (“Parent”), and proposed merger of the Company with Symphony Acquisition Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Purchaser”), pursuant to the terms of an Agreement and Plan of Merger, dated August 8, 2023, by and among the Company, Parent and Purchaser.

Forward-Looking Statements

This communication contains forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Decibel Therapeutics, Inc. (“Decibel”), including regarding Regeneron’s proposed acquisition of Decibel, the prospective benefits of the proposed acquisition, the potential contingent consideration amounts and terms and the anticipated occurrence, manner and timing of the proposed tender offer and the closing of the proposed acquisition. Actual events or results may differ materially from these forward-looking statements. Words such as “anticipate,” “expect,” “intend,” “plan,” “propose,” “provide,” “believe,” “seek,” “estimate,” variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. Risks that may cause these forward-looking statements to be inaccurate include, without limitation: uncertainties as to the timing of the tender offer and merger; uncertainties as to how many of Decibel’s stockholders will tender their stock in the offer; the possibility that competing offers will be made; the possibility that various closing conditions for the transaction may not be

satisfied or waived, including that a governmental entity may prohibit, delay, or refuse to grant approval for the consummation of the transaction (or only grant approval subject to adverse conditions or limitations); the difficulty of predicting the timing or outcome of regulatory approvals or actions, if any; the possibility that the transaction does not close; risks related to Regeneron’s ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the proposed acquisition will not be realized or will not be realized within the expected time period and that Regeneron and Decibel will not be integrated successfully; the effects of the transaction on relationships with employees, other business partners or governmental entities; negative effects of this announcement or the consummation of the proposed acquisition on the market price of Regeneron’s or Decibel’s common stock and/or Regeneron’s or Decibel’s operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition; Regeneron’s and Decibel’s ability to continue to conduct research and clinical programs; Regeneron’s and Decibel’s ability to manage their respective supply chains; Regeneron’s ability to manage net product sales of products marketed or otherwise commercialized by Regeneron and/or its collaborators or licensees (collectively, “Regeneron’s Products”); the nature, timing, and possible success and therapeutic applications of Regeneron’s Products, product candidates being developed by Regeneron and/or its collaborators or licensees (including without limitation Regeneron’s and Decibel’s investigational gene therapy DB-OTO for the treatment of congenital hearing loss and the other gene therapy programs being developed as part of the companies’ collaboration (collectively, “Regeneron’s Product Candidates”)), and development programs and product candidates being developed by Decibel independently (collectively, “Decibel’s Product Candidates”); the extent to which the results from the research and development programs conducted by Regeneron, Decibel, and/or their respective collaborators or licensees may be replicated in other studies and/or lead to advancement of product candidates to clinical trials, therapeutic applications, or regulatory approval; uncertainty of the utilization, market acceptance, and commercial success of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates and the impact of studies (whether conducted by Regeneron, Decibel or others and whether mandated or voluntary) on any of the foregoing or any potential regulatory approval of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; uncertainty regarding each of the contingent value rights milestones referenced in this communication and the possibility that any or all of such milestones will never be achieved and that some or all milestone payments may not be made; the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron’s Product Candidates and Decibel’s Product Candidates and new indications for Regeneron’s Products; the ability of Regeneron’s and Decibel’s collaborators, licensees, suppliers, or other third parties (as applicable) to perform manufacturing, filling, finishing, packaging, labeling, distribution, and other steps related to Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates; the ability of Regeneron and/or its collaborators to manufacture and manage supply chains for multiple products and product candidates; safety issues resulting from the administration of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in patients, including serious complications or side effects in connection with the use of Regeneron’s Products, Regeneron’s Product Candidates, and Decibel’s Product Candidates in clinical trials; determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron’s ability to continue to develop or commercialize Regeneron’s Products or Regeneron’s Product

Candidates, or Decibel’s ability to continue to develop Decibel’s Product Candidates; competing drugs and product candidates that may be superior to, or more cost effective than, Regeneron’s Products, Regeneron’s Product Candidates, or Decibel’s Product Candidates; and the impact of public health outbreaks, epidemics, or pandemics (such as the COVID-19 pandemic) on Regeneron’s or Decibel’s respective businesses.

A more complete description of these and other material risks can be found in Regeneron’s and Decibel’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including their Quarterly Reports on Form 10-Q for the quarterly period ended June 30, 2023 and March 31, 2023 for Regeneron and Decibel respectively, and their Annual Reports on Form 10-K for the fiscal year ended December 31, 2022 as well as the Schedule TO and related tender offer documents to be filed by Regeneron and its acquisition subsidiary, Symphony Acquisition Sub, Inc., the Schedule 14D-9 to be filed by Decibel, and, if applicable, the proxy statement referenced below. Any forward-looking statements are made based on the current beliefs and judgments of Regeneron’s and Decibel’s management, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron or Decibel. Except as required by law, Regeneron and Decibel do not undertake any obligation to update (publicly or otherwise) any forward-looking statement, including without limitation any financial projection or guidance, whether as a result of new information, future events, or otherwise.

Additional Information and Where to Find It

The tender offer referenced in this communication has not yet commenced. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any securities, nor is it a substitute for the tender offer materials that Decibel, Regeneron or its acquisition subsidiary, Symphony Acquisition Sub, Inc., will file with the SEC. The solicitation and offer to buy Decibel stock will only be made pursuant to an Offer to Purchase and related tender offer materials that Regeneron intends to file with the SEC. At the time the tender offer is commenced, Regeneron and its acquisition subsidiary will file a Tender Offer Statement on Schedule TO and thereafter Decibel will file a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the tender offer. Under certain circumstances described in the definitive transaction documents, Regeneron may determine to instead terminate or withdraw the offer and effect the transaction through a merger only, in which case the relevant documents to be filed with the SEC will include a proxy statement for the solicitation of votes of Decibel stockholders to approve the merger. DECIBEL’S STOCKHOLDERS AND OTHER INVESTORS ARE URGED TO READ CAREFULLY THE TENDER OFFER MATERIALS (INCLUDING AN OFFER TO PURCHASE, A RELATED LETTER OF TRANSMITTAL AND CERTAIN OTHER TENDER OFFER DOCUMENTS), THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, AND, IF APPLICABLE, THE PROXY STATEMENT BECAUSE THEY WILL EACH CONTAIN IMPORTANT INFORMATION THAT HOLDERS OF DECIBEL SECURITIES AND OTHER INVESTORS SHOULD CONSIDER BEFORE MAKING ANY DECISION WITH RESPECT TO THE TENDER OFFER, OR, IF APPLICABLE, VOTING ON THE TRANSACTION. The Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement will be made available to all stockholders of Decibel at no expense to them and will also be made available for free at the SEC’s website at www.sec.gov. Additional copies may be

obtained for free by contacting either Regeneron or Decibel. Copies of the documents filed with the SEC by Decibel will be available free of charge on Decibel’s website at https://ir.decibeltx.com or by contacting Decibel Investor Relations at (617) 370-8701. Copies of the documents filed with the SEC by Regeneron will be available free of charge on Regeneron’s website at https://investor.regeneron.com or by contacting Regeneron’s Investor Relations Department at invest@regeneron.com or (914) 847-7741.

In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement on Schedule 14D-9, and if applicable, the proxy statement, Regeneron and Decibel each file annual, quarterly and current reports, proxy statements and other information with the SEC, which are available to the public over the Internet at the SEC’s website at http://www.sec.gov.

If the tender offer is terminated and the transaction is to be effected by merger only, in which case, the approval of Decibel stockholders must be obtained, Regeneron, Decibel and their respective directors and executive officers may be deemed to be participants in any such solicitation of proxies from Decibel’s stockholders in connection with the proposed transaction. Information regarding Regeneron’s directors and executive officers is available in its proxy statement that was filed with the SEC; information regarding Decibel’s directors and executive officers is available in its proxy statement that was filed with the SEC. Other information regarding potential participants in any such proxy solicitation will be contained in any proxy statement filed in connection with the transaction.