Metsera (NASDAQ: MTSR) posts positive Phase 2b MET-097i weight-loss and tolerability results

Rhea-AI Filing Summary

Metsera, Inc. reported positive Phase 2b results for its obesity and metabolic candidate MET-097i, a first-in-class, fully biased, ultra-long acting GLP-1 receptor agonist with potential for monthly dosing. In the VESPER-1 trial, MET-097i achieved mean placebo-subtracted weight loss of up to 14.1% after 28 weekly doses, showing substantial body-weight reduction versus placebo.

The company also reported strong tolerability from VESPER-1 and a planned interim tolerability analysis of VESPER-3. At the highest evaluated dose in VESPER-3, there was minimal diarrhea and a risk difference versus placebo of 13% for nausea and 11% for vomiting at 12 weeks after two titration steps, suggesting a potentially favorable side-effect profile for a GLP-1 therapy.

Based on these data, Metsera plans to start a global Phase 3 program for MET-097i in late 2025. Additional Phase 2b trials are underway to test a monthly dosing profile for long-term maintenance and use in people with type 2 diabetes, and MET-097i serves as the backbone for four more clinical programs in the company’s pipeline.

Positive

• Phase 2b efficacy de-risking: VESPER-1 showed mean placebo-subtracted weight loss of up to 14.1% after 28 weekly doses of MET-097i, indicating clinically meaningful efficacy before Phase 3.
• Tolerability profile: The company reports potentially class-leading tolerability, with minimal diarrhea and modest nausea (13% risk difference) and vomiting (11% risk difference) versus placebo at 12 weeks in VESPER-3.
• Pipeline and Phase 3 momentum: Metsera plans to start a global Phase 3 program in late 2025, with additional Phase 2b trials ongoing and MET-097i serving as the backbone for four further clinical programs.

Negative

• None.

Insights

Biotech clinical development analyst

Strong Phase 2b weight-loss and tolerability data advance MET-097i toward Phase 3 in late 2025.

The disclosed results highlight MET-097i as a competitive GLP-1 receptor agonist, with VESPER-1 showing mean placebo-subtracted weight loss of up to 14.1% after 28 weekly doses. For obesity and metabolic drugs, double-digit placebo-adjusted weight loss at Phase 2b is a key de-risking milestone, as it indicates clinically meaningful efficacy before larger and more expensive Phase 3 studies.

Tolerability is equally important in the GLP-1 class, where gastrointestinal side effects often limit adherence. The filing states potentially class-leading tolerability in both VESPER-1 and VESPER-3, with the highest VESPER-3 dose showing minimal diarrhea and risk differences versus placebo of 13% for nausea and 11% for vomiting at 12 weeks after two titration steps. This combination of weight loss and manageable GI events, if confirmed in larger trials, supports the case for broad, long-term use.

The company plans to initiate a global Phase 3 program in late 2025 and is running additional Phase 2b studies to define a monthly dosing profile and evaluate use in type 2 diabetes. MET-097i is also described as the foundational incretin backbone for four more clinical programs, suggesting a platform strategy built around this molecule. Future company filings and data releases will clarify Phase 3 design, regulatory interactions, and how the broader pipeline leverages these results.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 29, 2025

METSERA, INC.

(Exact name of Registrant as Specified in Its Charter)

Delaware		001-42489		92-0931552
(State or Other Jurisdiction of Incorporation)		(Commission File Number)		(IRS Employer Identification No.)
3 World Trade Center 175 Greenwich Street
New York, New York				10007
(Address of Principal Executive Offices)				(Zip Code)

Registrant’s Telephone Number, Including Area Code: 212 784-6595

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, par value $0.00001 per share		MTSR		The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 7.01 Regulation FD Disclosure.

On September 29, 2025, Metsera, Inc. (the “Company”) announced positive topline data from VESPER-1 and positive data from a planned interim analysis for tolerability of VESPER-3 – two Phase 2b trials of MET-097i, a first-in-class fully biased, ultra-long acting GLP-1 receptor agonist (RA) with potential for monthly dosing. A copy of the press release is furnished as Exhibit 99.1.

The information in this Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended. The information contained in this Item 7.01, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission (the “SEC”) made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing.

Item 8.01 Other Events.

As noted in Item 7.01, on September 29, 2025, the Company announced positive topline data from VESPER-1 and positive data from a planned interim analysis for tolerability of VESPER-3 – two Phase 2b trials of MET-097i, a first-in-class fully biased, ultra-long acting GLP-1 receptor agonist (RA) with potential for monthly dosing. In VESPER-1, MET-097i demonstrated mean placebo-subtracted weight loss of up to 14.1% after 28 weekly doses. MET-097i demonstrated potentially class-leading tolerability in both trials. At the highest evaluated dose in VESPER-3, there was minimal diarrhea signal and a risk difference from placebo of 13% nausea and 11% vomiting at 12 weeks after two titration steps.

Next Steps

Based on these positive topline data, the Company is on track to initiate a global Phase 3 program in late 2025.

Additional Phase 2b trials are ongoing to characterize the monthly profile of MET-097i for long-term maintenance and in populations with type 2 diabetes mellitus (T2DM):

• VESPER-1 study extension exploring a range of less frequent dosing options for continued induction and maintenance of weight loss.

• VESPER-2 is ongoing to assess MET-097i in participants with T2DM, with topline data expected in early 2026.

• VESPER-3 is ongoing to assess monthly dosing of MET-097i, with topline data at the primary endpoint at 28-weeks expected by year-end 2025 or in early 2026.

MET-097i is the foundational incretin backbone of four additional clinical programs:

• MET-233/097, a first-in-category monthly multi-NuSH combination with MET-233i, an ultra-long acting amylin agonist, is in ongoing 12-week Phase 1/2a trials with topline data expected at year-end 2025 or in early 2026.

• MET-034/097, a combination with MET-034i, an ultra-long acting GIP receptor agonist, is initiating Phase 1 clinical studies.

• MET-097o, an oral form of MET-097, is currently being evaluated in Phase 1 trials.

• MET-815, a prodrug of MET-097i designed for quarterly maintenance dosing, is in IND-enabling studies.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.		Description
99.1		Press Release, dated as of September 29, 2025.
104		Cover Page Interactive Data File - the cover page XBRL tags are embedded within the Inline XBRL document.

Forward-Looking Statements

This Current Report on Form 8-K contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995 that involve substantial risks and uncertainties, including information about, among other topics, the timelines, design and results of the Company’s clinical trials and data releases; the Company’s product candidate pipeline and milestone events; and potential benefits of treatment with the Company’s product candidates, that involves substantial risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements. Risks and uncertainties include, among other things, the Company’s limited operating history; the Company’s ability to generate revenue or become profitable; the Company’s failure to obtain additional capital when needed on acceptable terms or at all; raising additional capital may cause dilution to the Company’s stockholders or require the Company to relinquish rights to its technologies or product candidates; the Company’s risks related to the satisfaction or waiver of the conditions to closing the proposed acquisition by Pfizer Inc. (“Pfizer”) (including the failure to obtain necessary regulatory approvals and failure to obtain the requisite vote by the Company stockholders) in the anticipated timeframe or at all, including the possibility that the proposed acquisition does not close; the possibility that competing offers may be made; risks related to the ability to realize the anticipated benefits of the proposed acquisition, including the possibility that the expected benefits from the acquisition will not be realized or will not be realized within the expected time period; the risk that the businesses will not be integrated successfully; disruption from the transaction making it more difficult to maintain business and operational relationships, including the Company’s ability to attract and retain highly qualified management and other clinical and scientific personals; negative effects of this announcement or the consummation of the proposed acquisition on the market price of the Company’s common stock and/or operating results; significant transaction costs; unknown liabilities; the risk of litigation and/or regulatory actions related to the proposed acquisition or the Company’s business; other business effects and uncertainties, including the effects of industry, market, business, economic, political or regulatory conditions; future exchange and interest rates; risks and uncertainties related to issued or future executive orders or other new, or changes in, laws, regulations or policy; changes in tax and other laws, regulations, rates and policies; the uncertainties inherent in business and financial planning, including, without limitation, risks related to the Company’s business and prospects, adverse developments in the Company’s markets, or adverse developments in the U.S. or global capital markets, credit markets, regulatory environment, tariffs and other trade policies or economies generally; future business combinations or disposals; uncertainties regarding the commercial success of the Company’s pipeline products; risks associated with the Company conducting clinical trials and preclinical studies outside of the United States; the Company’s reliance on third parties to conduct clinical trials and preclinical studies and for the manufacture and shipping of its product candidates; the risk that the Company’s product candidates are associated with side effects, adverse events or other properties or safety risks; risks associated with the Company’s license and collaboration agreements and future strategic alliances; the Company’s ability to obtain, maintain, defend and enforce patent or other intellectual property protection for current or future product candidates or technology; the uncertainties inherent in research and development, including the ability to meet anticipated clinical endpoints, commencement and/or completion dates for clinical trials, regulatory submission dates, regulatory approval dates and/or launch dates, as well as the possibility of unfavorable new clinical data and further analyses of existing clinical data; risks associated with initial, preliminary or interim data; the risk that clinical trial data are subject to differing interpretations and assessments by regulatory authorities; whether regulatory authorities will be satisfied with the design of and results from the clinical studies; whether and when drug applications may be filed in any jurisdictions for the Company’s pipeline products for any potential indications; whether and when any such applications may be approved by regulatory authorities, which will depend on myriad factors, including making a determination as to whether the product’s benefits outweigh its known risks and determination of the product’s efficacy and,

if approved, whether any such products will be commercially successful; decisions by regulatory authorities impacting labeling, manufacturing processes, safety and/or other matters that could affect the availability or commercial potential of such products; and uncertainties regarding the impact of COVID-19; and competitive developments.

You should carefully consider the foregoing factors and the other risks and uncertainties that affect the business of the Company described in the “Risk Factors” and “Forward-Looking Information and Factors That May Affect Future Results” (in the case of Pfizer) and “Special Note regarding Forward Looking Statements” (in the case of the Company) sections of their respective Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and other documents filed by either of them from time to time with the SEC, all of which are available at www.sec.gov. These filings identify and address other important risks and uncertainties that could cause actual events and results to differ materially from those contained in the forward-looking statements. Forward-looking statements speak only as of the date they are made. Readers are cautioned not to put undue reliance on forward-looking statements, and the Company does not assume any obligation to, and do not intend to, update or revise these forward-looking statements, whether as a result of new information, future events, or otherwise, unless required by law. The Company does not give any assurance that it will achieve its expectations.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

						METSERA, INC.
Date: September 29, 2025				By:		/s/ Matthew Lang
						Matthew Lang Chief Legal Officer and Secretary

FAQ

What did Metsera (MTSR) announce in this Form 8-K?

Metsera announced positive topline data from two Phase 2b trials of its GLP-1 receptor agonist MET-097i, VESPER-1 and VESPER-3, including strong weight-loss efficacy and favorable tolerability, and outlined plans to begin a global Phase 3 program in late 2025.

How effective was MET-097i in Metsera’s VESPER-1 Phase 2b trial?

In VESPER-1, MET-097i achieved mean placebo-subtracted weight loss of up to 14.1% after 28 weekly doses, indicating substantial additional weight reduction compared with placebo in this Phase 2b study.

What tolerability data did Metsera (MTSR) report from the VESPER-3 trial?

Metsera reported that MET-097i showed potentially class-leading tolerability, with minimal diarrhea at the highest evaluated dose in VESPER-3 and risk differences versus placebo of 13% for nausea and 11% for vomiting at 12 weeks after two titration steps.

What are Metsera’s next steps for MET-097i after these Phase 2b results?

Based on the positive topline data, Metsera plans to initiate a global Phase 3 program for MET-097i in late 2025 and is continuing additional Phase 2b trials to characterize monthly dosing for long-term maintenance and evaluate use in type 2 diabetes.

What is MET-097i and why is it important for Metsera (MTSR)?

MET-097i is described as a first-in-class fully biased, ultra-long acting GLP-1 receptor agonist with potential for monthly dosing. It is the foundational incretin backbone of four additional clinical programs, making it central to Metsera’s pipeline strategy.

Does the filing mention any risks related to Metsera’s acquisition by Pfizer?

Yes. The forward-looking statements section lists risks and uncertainties tied to the proposed acquisition by Pfizer, including satisfaction of closing conditions, regulatory approvals, stockholder votes, possible competing offers, execution of integration, transaction costs, and potential litigation or regulatory actions.