--- title: "MET-097i | PepTracker Pro" url: https://peptrackerpro.com/peptides/met-097i description: "An ultra-long-acting GLP-1 receptor agonist designed for both once-weekly and once-monthly subcutaneous dosing, delivering double-digit weight loss with class-leading gastrointestinal tolerability in mid-stage trials." lang: en --- Skip to main content **Educational information only.** This site does not provide medical advice. Read full disclaimer (https://peptrackerpro.com/disclaimer) **Research-only content.** This page is for educational purposes and does not constitute medical advice. Read full disclaimer → (https://peptrackerpro.com/research-disclaimer) # MET-097i Medium Evidence An ultra-long-acting GLP-1 receptor agonist designed for both once-weekly and once-monthly subcutaneous dosing, delivering double-digit weight loss with class-leading gastrointestinal tolerability in mid-stage trials. Aliases MET-097i +3 more Evidence Medium Evidence Last Updated 2026-06-20 Reading Time 3 min ## What It Is MET-097i is an investigational ultra-long-acting GLP-1 receptor agonist originally developed by Metsera and now owned by Pfizer, which completed its acquisition of Metsera in November 2025 (enterprise value ~$7 billion plus a contingent value right of up to $20.65 per share, after a high-profile bidding war with Novo Nordisk). MET-097i is engineered with a fatty-acid-based half-life-extension technology that gives it an exceptionally long duration of action, enabling not only conventional once-weekly subcutaneous dosing but also a once-monthly maintenance regimen — a dosing interval no approved incretin therapy currently offers. The drug is being positioned as a potential best-in-class injectable GLP-1 differentiated on two fronts: convenience (monthly maintenance injections) and tolerability. In an earlier Phase 2b study, MET-097i produced approximately 14.1% mean weight loss with weekly dosing. In the VESPER-3 Phase 2b trial of once-monthly maintenance dosing, the compound met its primary endpoint with statistically significant placebo-adjusted weight reductions of 10% and 12.3% at week 28 on the low and medium monthly maintenance regimens planned for Phase 3, and importantly showed continued weight loss with no plateau after participants switched from weekly to monthly dosing. Tolerability was a defining feature: the trial reported a placebo-like frequency of diarrhea and a relatively low risk difference versus placebo for nausea (~13%) and vomiting (~11%), which Pfizer characterized as potentially class-leading. Pfizer has said roughly 10 Phase 3 trials with MET-097i (referred to internally as PF-'3944) are expected to advance in 2026, and the molecule anchors a broader next-generation obesity portfolio acquired from Metsera that also includes the amylin analog MET-233i and planned GLP-1/amylin combination programs. MET-097i is investigational and not approved in any jurisdiction. Also known as: MET-097i, PF-'3944, Metsera MET-097i, ultra-long-acting GLP-1 (Metsera/Pfizer) ## Regulatory Status Investigational — Phase 2b complete, Phase 3 beginning VESPER-3 Phase 2b once-monthly maintenance study met its primary weight-loss endpoint at 28 weeks (reported February 2026). Pfizer expects ~10 Phase 3 trials with MET-097i (PF-'3944) to advance in 2026. Acquired by Pfizer via the completed Metsera acquisition (November 2025). Not approved in any jurisdiction. Effective: June 2026 View FDA Source (https://www.pfizer.com/news/press-release/press-release-detail/pfizers-ultra-long-acting-injectable-glp-1-ra-shows-robust) ## Why Researchers Study It MET-097i is closely watched because it pairs double-digit weight loss with a once-monthly maintenance dosing option that no approved incretin therapy currently offers, plus a tolerability profile that Pfizer describes as potentially class-leading. It is studied as a potential best-in-class injectable GLP-1 differentiated on convenience and tolerability rather than peak efficacy alone, and as the anchor of Pfizer's next-generation obesity portfolio (including the amylin analog MET-233i and planned GLP-1/amylin combinations) following the company's ~$7 billion acquisition of Metsera. ## Proposed Mechanisms - Agonizes the GLP-1 receptor to reduce appetite, enhance satiety, and improve glycemic control - Fatty-acid half-life-extension chemistry produces an ultra-long duration of action - Ultra-long half-life enables both once-weekly and once-monthly subcutaneous dosing - Engineered for class-leading gastrointestinal tolerability (low nausea and vomiting vs placebo) - Designed to serve as a backbone for combination with an amylin analog (MET-233i) ## Evidence Snapshot Medium Evidence Low Medium High | Study Type | Model | Outcome | Link | | --- | --- | --- | --- | | Human (Phase 2b, weekly dosing) | Adults with obesity or overweight | Approximately 14.1% mean weight loss with once-weekly dosing; described by the company as competitive efficacy with class-leading tolerability | Source: https://www.clinicaltrialsarena.com/news/pfizers-obesity-bet-shows-14-1-weight-loss-in-phase-iib-trial/ | | Human (Phase 2b, VESPER-3, monthly maintenance) | Adults with obesity transitioning from weekly to once-monthly maintenance dosing | Met primary endpoint at week 28: placebo-adjusted weight loss of 10% (low) and 12.3% (medium) on the monthly maintenance regimens planned for Phase 3; continued weight loss with no plateau after switching to monthly; nausea risk difference ~13% and vomiting ~11% vs placebo, diarrhea placebo-like | Source: https://www.pfizer.com/news/press-release/press-release-detail/pfizers-ultra-long-acting-injectable-glp-1-ra-shows-robust | | Corporate / development | Pfizer acquisition of Metsera and Phase 3 planning | Pfizer completed the Metsera acquisition in November 2025 (~$7B enterprise value plus CVR up to $20.65/share); ~10 Phase 3 trials with MET-097i (PF-'3944) expected to advance in 2026 | Source: https://www.pfizer.com/news/press-release/press-release-detail/pfizer-completes-acquisition-metsera | ## Commonly Discussed Benefits Weight Management: https://peptrackerpro.com/benefits/weight-management Metabolism: https://peptrackerpro.com/benefits/metabolism Fat Loss: https://peptrackerpro.com/benefits/fat-loss Appetite Regulation: https://peptrackerpro.com/benefits/appetite-regulation Researching MET-097i? Track it, set reminders, and keep notes in the free app. Track in App (https://app.peptrackerpro.com/?add=met-097i) ## Safety & Cautions - Investigational; not approved in any jurisdiction - Only Phase 2b efficacy and tolerability data reported to date; Phase 3 outcomes and long-term safety unknown - Full VESPER-3 data not yet peer-reviewed/published - Available only through clinical trial enrollment - Not FDA-approved; not a compounding-eligible peptide - GLP-1-class effects (nausea, vomiting, GI symptoms) can still occur despite the favorable tolerability profile reported ## Comparisons See how MET-097i compares to related peptides: MET-097i vs Insulin Efsitora Alfa: https://peptrackerpro.com/compare/met-097i-vs-insulin-efsitora-alfa MET-097i vs MET-233i: https://peptrackerpro.com/compare/met-097i-vs-met-233i MET-097i vs Orforglipron: https://peptrackerpro.com/compare/met-097i-vs-orforglipron MET-097i vs Petrelintide: https://peptrackerpro.com/compare/met-097i-vs-petrelintide MET-097i vs Semaglutide: https://peptrackerpro.com/compare/met-097i-vs-semaglutide MET-097i vs Tirzepatide: https://peptrackerpro.com/compare/met-097i-vs-tirzepatide ## Calculator Tools Use our research tools to explore dosing and reconstitution data: Reconstitution Calculator: https://peptrackerpro.com/calculators ## Citations 1. [1] Pfizer's Ultra-Long-Acting Injectable GLP-1 RA Shows Robust and Continued Weight Loss with Monthly Dosing in Phase 2b Trial (Feb 2026) PubMed (https://www.pfizer.com/news/press-release/press-release-detail/pfizers-ultra-long-acting-injectable-glp-1-ra-shows-robust) 2. [2] Pfizer Completes Acquisition of Metsera (Nov 2025) PubMed (https://www.pfizer.com/news/press-release/press-release-detail/pfizer-completes-acquisition-metsera) 3. [3] Pfizer's obesity bet shows 14.1% weight loss in Phase IIb trial — Clinical Trials Arena PubMed (https://www.clinicaltrialsarena.com/news/pfizers-obesity-bet-shows-14-1-weight-loss-in-phase-iib-trial/) ### Keep researching in the app - Log MET-097i to your private tracker - Set a dosing reminder - Compare it side-by-side with your stack Open PepTracker Pro Free: https://app.peptrackerpro.com/?add=met-097i Browse more peptides: https://peptrackerpro.com/peptides ## Related Peptides ### Insulin Efsitora Alfa High Evidence A once-weekly basal insulin engineered as a single-chain insulin analog fused to an antibody (IgG2) Fc fragment, giving it a roughly 17-day half-life so a single subcutaneous injection covers a full week. Developed by Eli Lilly (code LY3209590, also called basal insulin Fc or BIF), efsitora is designed to replace daily long-acting insulin with a flat, ultra-stable weekly profile. In the large Phase 3 QWINT program it matched daily insulins glargine and degludec on A1C in type 2 diabetes, and in insulin-naive patients its simplified fixed-dose titration cut the number of dose adjustments dramatically while keeping hypoglycemia low. In type 1 diabetes (QWINT-5) it was non-inferior on A1C but showed a higher rate of severe hypoglycemia, a key safety caveat. As of mid-2026 efsitora is under FDA review for type 2 diabetes (a decision expected in the third quarter of 2026) and would compete directly with Novo Nordisk's once-weekly insulin icodec (Awiqli). Glycemic Control: https://peptrackerpro.com/benefits/glycemic-control Hormone Support: https://peptrackerpro.com/benefits/hormone-support View Details: https://peptrackerpro.com/peptides/insulin-efsitora-alfa \+ Compare: https://peptrackerpro.com/compare?select=insulin-efsitora-alfa Track in App: https://app.peptrackerpro.com/?add=insulin-efsitora-alfa ### MET-233i Medium Evidence MET-233i is a first-in-class, once-monthly ultra-long-acting amylin analog for obesity, originally developed by Metsera and now a Pfizer asset. In its Phase 1 trial it produced up to 8.4% placebo-subtracted weight loss after five weekly doses and showed a roughly 19-day half-life - the most durable of any reported amylin analog - supporting once-monthly subcutaneous dosing. It is engineered to be combined with Metsera's monthly GLP-1 agonist MET-097i in a single once-monthly injection. Weight Management: https://peptrackerpro.com/benefits/weight-management Metabolism: https://peptrackerpro.com/benefits/metabolism Fat Loss: https://peptrackerpro.com/benefits/fat-loss Muscle Preservation: https://peptrackerpro.com/benefits/muscle-preservation View Details: https://peptrackerpro.com/peptides/met-233i \+ Compare: https://peptrackerpro.com/compare?select=met-233i Track in App: https://app.peptrackerpro.com/?add=met-233i ### Orforglipron High Evidence The first oral non-peptide GLP-1 receptor agonist, FDA-approved in April 2026 for chronic weight management with no food or water restrictions. Weight Management (https://peptrackerpro.com/benefits/weight-management)Appetite Regulation (https://peptrackerpro.com/benefits/appetite-regulation)Metabolism (https://peptrackerpro.com/benefits/metabolism)Fat Loss (https://peptrackerpro.com/benefits/fat-loss)+1 more View Details: https://peptrackerpro.com/peptides/orforglipron \+ Compare: https://peptrackerpro.com/compare?select=orforglipron Track in App: https://app.peptrackerpro.com/?add=orforglipron ### Petrelintide Medium Evidence A long-acting amylin analog in late-stage clinical development for chronic weight management, designed to deliver double-digit weight loss with a tolerability profile comparable to placebo. View Details: https://peptrackerpro.com/peptides/petrelintide \+ Compare: https://peptrackerpro.com/compare?select=petrelintide Track in App: https://app.peptrackerpro.com/?add=petrelintide ### Semaglutide High Evidence A GLP-1 receptor agonist FDA-approved for type 2 diabetes and chronic weight management. Weight Management (https://peptrackerpro.com/benefits/weight-management)Appetite Regulation (https://peptrackerpro.com/benefits/appetite-regulation)Metabolism (https://peptrackerpro.com/benefits/metabolism)Fat Loss (https://peptrackerpro.com/benefits/fat-loss)+3 more View Details: https://peptrackerpro.com/peptides/semaglutide \+ Compare: https://peptrackerpro.com/compare?select=semaglutide Track in App: https://app.peptrackerpro.com/?add=semaglutide ### Tirzepatide High Evidence A dual GIP/GLP-1 receptor agonist FDA-approved for type 2 diabetes, weight management, and MASH with liver fibrosis. View Details: https://peptrackerpro.com/peptides/tirzepatide \+ Compare: https://peptrackerpro.com/compare?select=tirzepatide Track in App: https://app.peptrackerpro.com/?add=tirzepatide ## Structured data ```json [ { "@context": "https://schema.org", "@type": "Organization", "name": "PepTracker Pro", "url": "https://peptrackerpro.com", "logo": "https://peptrackerpro.com/favicon.png", "description": "Evidence-based educational resource dedicated to improving peptide research literacy.", "contactPoint": { "@type": "ContactPoint", "email": "hello@peptrackerpro.com", "contactType": "customer support" }, "sameAs": [] }, { "@context": "https://schema.org", "@type": "MedicalWebPage", "name": "MET-097i", "description": "An ultra-long-acting GLP-1 receptor agonist designed for both once-weekly and once-monthly subcutaneous dosing, delivering double-digit weight loss with class-leading gastrointestinal tolerability in mid-stage trials.", "url": "https://peptrackerpro.com/peptides/met-097i", "lastReviewed": "2026-06-20", "reviewedBy": { "@type": "Organization", "name": "PepTracker Pro Research Team", "url": "https://peptrackerpro.com" }, "isPartOf": { "@type": "WebSite", "name": "PepTracker Pro", "url": "https://peptrackerpro.com" } }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://peptrackerpro.com" }, { "@type": "ListItem", "position": 2, "name": "Peptides", "item": "https://peptrackerpro.com/peptides" }, { "@type": "ListItem", "position": 3, "name": "MET-097i", "item": "https://peptrackerpro.com/peptides/met-097i" } ] }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "People tracking next-generation GLP-1 weight-loss drugs beyond semaglutide and tirzepatide?", "acceptedAnswer": { "@type": "Answer", "text": "MET-097i is a research peptide studied in preclinical models. 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