--- title: "PF-08653944 | PepTracker Pro" description: "An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned." lang: en json-ld: | [ { "@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": "PF-08653944", "description": "An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned.", "url": "https://peptrackerpro.com/peptides/pf-08653944", "lastReviewed": "2026-05-11", "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": "PF-08653944", "item": "https://peptrackerpro.com/peptides/pf-08653944" } ] }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "People researching convenient GLP-1 dosing options?", "acceptedAnswer": { "@type": "Answer", "text": "PF-08653944 is a research peptide studied in preclinical models. An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned." } }, { "@type": "Question", "name": "Those comparing next-generation weight loss drug pipelines?", "acceptedAnswer": { "@type": "Answer", "text": "PF-08653944 is a research peptide studied in preclinical models. An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned." } }, { "@type": "Question", "name": "Individuals interested in monthly vs weekly vs daily dosing tradeoffs?", "acceptedAnswer": { "@type": "Answer", "text": "PF-08653944 is a research peptide studied in preclinical models. An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned." } }, { "@type": "Question", "name": "Researchers following Pfizer's obesity program?", "acceptedAnswer": { "@type": "Answer", "text": "PF-08653944 is a research peptide studied in preclinical models. An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned." } } ] } ] --- [Skip to main content](#main) **Educational information only.** This site does not provide medical advice. [Read full disclaimer](/disclaimer) [PepTracker Pro](/) [Home](/)[Peptides](/peptides)[Compare](/compare)[Glossary](/glossary)[Blog](/blog)[Calculators](/calculators)[Start Here](/start) [Open the App](https://app.peptrackerpro.com) [Peptides](/peptides)/ PF-08653944 **Research-only content.** This page is for educational purposes and does not constitute medical advice. [Read full disclaimer →](/research-disclaimer) # PF-08653944 Medium Evidence An ultra-long-acting injectable GLP-1 receptor agonist enabling monthly dosing, with 12.3% placebo-adjusted weight loss in Phase 2b and 10 Phase 3 trials planned. Aliases MET-097i +3 more Evidence Medium Evidence Last Updated 2026-05-11 Reading Time 2 min ## Table of Contents 1. [What It Is](#what-it-is) 2. [Regulatory Status](#regulatory-status) 3. [Why Researchers Study It](#why-researchers-study) 4. [Proposed Mechanisms](#proposed-mechanisms) 5. [Evidence Snapshot](#evidence-snapshot) 6. [Commonly Discussed Benefits](#benefits) 7. [Safety & Cautions](#safety) 8. [Comparisons](#comparisons) 9. [Calculator Tools](#calculator) 10. [Citations](#citations) ## What It Is PF-08653944 (also known as MET-097i or PF'3944) is a fully-biased, ultra-long-acting injectable GLP-1 receptor agonist being developed by Pfizer, acquired through its $10 billion purchase of Metsera. What distinguishes PF'3944 from existing GLP-1 drugs is its pharmacokinetic profile enabling once-monthly maintenance dosing after an initial weekly titration period. In the Phase 2b VESPER-3 trial, PF'3944 demonstrated up to 12.3% mean placebo-adjusted weight loss at 28 weeks in adults with obesity or overweight without type 2 diabetes. Weight loss continued after switching from weekly to monthly dosing with no plateau observed at 28 weeks, and the safety profile was well-tolerated and consistent with the GLP-1 RA class. Pfizer plans 10 Phase 3 trials of PF'3944 beginning in 2026, including VESPER-4 (weekly dosing in obesity), VESPER-5 (weekly with T2D), VESPER-6 (monthly dosing in obesity), and at least seven additional studies. Detailed VESPER-3 results will be presented at the American Diabetes Association 86th Scientific Sessions on June 6, 2026. With 10 Phase 3 trials expected to advance in 2026, PF'3944 is central to Pfizer's strategy to challenge the Lilly/Novo duopoly in the obesity market — analysts position it as a potential top-3 monthly dosing contender alongside MariTide and the Ascletis pipeline. Also known as: MET-097i, PF'3944, Pfizer Monthly GLP-1, Metsera GLP-1 ## Regulatory Status Investigational Phase 2b VESPER-3 completed. Phase 3 VESPER-4 (weekly dosing, obesity without T2D) initiated. 10 Phase 3 trials planned including VESPER-5 (weekly with T2D) and VESPER-6 (monthly dosing). Effective: February 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 PF'3944's ability to deliver clinically meaningful weight loss with once-monthly dosing could dramatically improve adherence and convenience compared to weekly injections. If Phase 3 confirms Phase 2b results, it would be the first monthly GLP-1 option, potentially reshaping the competitive landscape alongside oral formulations like orforglipron. ## Proposed Mechanisms - Full GLP-1 receptor agonism with biased signaling profile - Ultra-long pharmacokinetic half-life enables monthly dosing - Central appetite suppression via hypothalamic GLP-1 receptors - Slowed gastric emptying contributing to reduced food intake - Potential cardiovascular and metabolic benefits consistent with GLP-1 class ## Evidence Snapshot Medium Evidence Low Medium High Study Type Model Outcome Link Phase 2b (VESPER-3) 28-week, weekly-to-monthly transition, obesity without T2D Up to 12.3% placebo-adjusted weight loss; continued loss after switch to monthly; no plateau at 28 weeks [Source](https://www.pfizer.com/news/press-release/press-release-detail/pfizers-ultra-long-acting-injectable-glp-1-ra-shows-robust) ## Commonly Discussed Benefits [Weight Management](/benefits/weight-management)[Appetite Regulation](/benefits/appetite-regulation)[Fat Loss](/benefits/fat-loss)[Metabolism](/benefits/metabolism) Researching PF-08653944 ? Track it, set reminders, and keep notes in the free app. [Track in App](https://app.peptrackerpro.com/?add=pf-08653944) ## Safety & Cautions - Phase 3 VESPER-4 trial initiated; 10 Phase 3 trials planned across weekly and monthly dosing regimens - 28-week data — longer-term efficacy and safety unknown - GI side effects (nausea, vomiting) consistent with GLP-1 class - Monthly dosing convenience must be weighed against injection-site considerations - No regulatory submissions yet ## Comparisons See how PF-08653944 compares to related peptides: [PF-08653944 vs Orforglipron](/compare/pf-08653944-vs-orforglipron) [PF-08653944 vs Retatrutide](/compare/pf-08653944-vs-retatrutide) [PF-08653944 vs Semaglutide](/compare/pf-08653944-vs-semaglutide) [PF-08653944 vs Survodutide](/compare/pf-08653944-vs-survodutide) [PF-08653944 vs Tirzepatide](/compare/pf-08653944-vs-tirzepatide) ## Calculator Tools Use our research tools to explore dosing and reconstitution data: [Reconstitution Calculator](/calculators) ## Citations 1. \[1\] Pfizer — Ultra-Long-Acting Injectable GLP-1 RA Shows Robust Weight Loss with Monthly Dosing in Phase 2b Trial. February 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 Phase IIb Data Support Monthly GLP-1 Dosing for Obesity. BioPharm International 2026 [PubMed](https://www.biopharminternational.com/view/pfizer-phase-iib-data-support-monthly-glp-1-dosing-for-obesity) ### Keep researching in the app - Log PF-08653944 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=pf-08653944) [Browse more peptides](/peptides) ## Related Peptides ### 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](/benefits/weight-management)[Appetite Regulation](/benefits/appetite-regulation)[Metabolism](/benefits/metabolism)[Fat Loss](/benefits/fat-loss)+1 more [View Details](/peptides/orforglipron) [\+ Compare](/compare?select=orforglipron)[](https://app.peptrackerpro.com/?add=orforglipron) ### Retatrutide High Evidence An investigational triple agonist (GIP/GLP-1/glucagon) studied for obesity and metabolic disease. [Weight Management](/benefits/weight-management)[Appetite Regulation](/benefits/appetite-regulation)[Metabolism](/benefits/metabolism)[Fat Loss](/benefits/fat-loss) [View Details](/peptides/retatrutide) [\+ Compare](/compare?select=retatrutide)[](https://app.peptrackerpro.com/?add=retatrutide) ### Semaglutide High Evidence A GLP-1 receptor agonist FDA-approved for type 2 diabetes and chronic weight management. [Weight Management](/benefits/weight-management)[Appetite Regulation](/benefits/appetite-regulation)[Metabolism](/benefits/metabolism)[Fat Loss](/benefits/fat-loss)+3 more [View Details](/peptides/semaglutide) [\+ Compare](/compare?select=semaglutide)[](https://app.peptrackerpro.com/?add=semaglutide) ### Survodutide Medium Evidence A dual GLP-1/glucagon receptor agonist with FDA Breakthrough Therapy designation for MASH and Priority Review NDA filed February 2026. Phase 3 SYNCHRONIZE-1 reported 16.6% weight loss at 76 weeks; approval possible Q3 2026. [Weight Management](/benefits/weight-management)[Appetite Regulation](/benefits/appetite-regulation)[Metabolism](/benefits/metabolism)[Fat Loss](/benefits/fat-loss) [View Details](/peptides/survodutide) [\+ Compare](/compare?select=survodutide)[](https://app.peptrackerpro.com/?add=survodutide) ### Tirzepatide High Evidence A dual GIP/GLP-1 receptor agonist FDA-approved for type 2 diabetes, weight management, and MASH with liver fibrosis. [Weight Management](/benefits/weight-management)[Appetite Regulation](/benefits/appetite-regulation)[Metabolism](/benefits/metabolism)[Fat Loss](/benefits/fat-loss)+1 more [View Details](/peptides/tirzepatide) [\+ Compare](/compare?select=tirzepatide)[](https://app.peptrackerpro.com/?add=tirzepatide) [PepTracker Pro](/) Educational peptide information and research tracking tools. Not medical advice. #### Explore - [Peptide Directory](/peptides) - [Compare Peptides](/compare) - [Glossary](/glossary) - [Benefits](/benefits/sleep) #### Learn - [Blog](/blog) - [Calculators](/calculators) - [Start Here](/start) - [About](/about) #### Legal - [Editorial Policy](/editorial-policy) - [Research Disclaimer](/research-disclaimer) - [Disclaimer](/disclaimer) - [Privacy Policy](/privacy) - [Terms of Service](/terms) - [Contact](/contact) © 2026 PepTracker Pro. Educational purposes only. Not medical advice. Always consult a licensed healthcare provider.