---
title: "MET-097i: Pfizer's Once-Monthly GLP-1 and the Race for Longer Dosing Intervals (June 20, 2026) | PepTracker Pro Blog"
url: https://peptrackerpro.com/blog/met-097i-pfizer-metsera-monthly-glp1-vesper-3-june-20-2026
description: "Pfizer's newly acquired MET-097i is an ultra-long-acting GLP-1 designed for once-monthly maintenance dosing. Here's what the VESPER-3 Phase 2b data show, why the dosing interval matters, and what to watch as ~10 Phase 3 trials begin in 2026."
lang: en
---

Skip to main content

**Educational information only.** This site does not provide medical advice. Read full disclaimer (https://peptrackerpro.com/disclaimer)

Research & Compounds

Research & Compounds

# MET-097i: Pfizer's Once-Monthly GLP-1 and the Race for Longer Dosing Intervals (June 20, 2026)

PepTracker Pro Research Team June 20, 2026 8 min read

## Table of Contents

- A GLP-1 you might take once a month
- How it works
- What the VESPER-3 data showed
- Tolerability is part of the pitch
- Why Pfizer paid up for it
- What to watch next

## A GLP-1 you might take once a month

Most of the GLP-1 weight-loss drugs people know — semaglutide and tirzepatide — are taken once a week. MET-097i is built to stretch that interval much further. It is an ultra-long-acting GLP-1 receptor agonist engineered to work not just on a weekly schedule but on a once-monthly maintenance schedule, a dosing interval no approved incretin therapy currently offers. That single design choice is the headline: if a monthly injection can hold weight loss as well as a weekly one, it changes the day-to-day reality of staying on treatment. MET-097i came to Pfizer through its acquisition of the biotech Metsera, and inside Pfizer the molecule is also referred to as PF-'3944.

## How it works

MET-097i targets the GLP-1 receptor, the same pathway behind today's leading obesity drugs. Activating that receptor reduces appetite, increases the feeling of fullness after eating, and improves blood-sugar control. What sets MET-097i apart mechanically is its half-life-extension chemistry: a fatty-acid-based modification gives the molecule an exceptionally long duration of action in the body. That extended half-life is what makes once-monthly maintenance dosing plausible in the first place. The same long-acting design is also intended to let MET-097i serve as a backbone for combination with an amylin analog, MET-233i, which Pfizer also acquired from Metsera.

## What the VESPER-3 data showed

In an earlier Phase 2b study using weekly dosing, MET-097i produced roughly 14.1% mean weight loss — competitive with other injectables. The more distinctive readout came from VESPER-3, a Phase 2b trial specifically testing once-monthly maintenance dosing. It met its primary endpoint at 28 weeks, with placebo-adjusted weight loss of about 10% and 12.3% on the low and medium monthly maintenance regimens planned for Phase 3. Notably, participants who switched from weekly to monthly dosing kept losing weight, with no plateau reported after the switch — an early signal that the longer interval did not cost efficacy.

## Tolerability is part of the pitch

GLP-1 drugs are effective but notorious for gastrointestinal side effects, especially nausea and vomiting, which lead many people to stop treatment. Pfizer is positioning MET-097i partly on tolerability. In VESPER-3 the company reported a placebo-like frequency of diarrhea and a relatively small risk difference versus placebo for nausea (around 13%) and vomiting (around 11%), describing the profile as potentially class-leading. If those numbers hold up in Phase 3, better tolerability plus monthly dosing could translate into more people staying on therapy long enough to benefit — though that is a hypothesis Phase 3 still has to confirm.

## Why Pfizer paid up for it

MET-097i did not arrive quietly. Pfizer completed its acquisition of Metsera in November 2025, at roughly a $7 billion enterprise value plus a contingent value right of up to $20.65 per share tied to clinical and regulatory milestones — and only after a contentious bidding war with Novo Nordisk. The deal gave Pfizer a credible, late-stage entry into the obesity market it had struggled to crack with earlier internal candidates. MET-097i anchors that bet, with a broader pipeline behind it including the amylin analog MET-233i and planned GLP-1/amylin combination programs.

## What to watch next

The near-term story is Phase 3. Pfizer has said roughly 10 Phase 3 trials with MET-097i are expected to advance in 2026, which will test whether the monthly-dosing convenience and favorable tolerability seen in Phase 2b hold at scale and over longer durations. Key questions: does monthly maintenance match weekly dosing on durable weight loss and metabolic endpoints; how does the tolerability profile compare head-to-head with established drugs; and how the GLP-1/amylin combination with MET-233i performs. As always, MET-097i is investigational and not approved anywhere — none of this is medical advice, and the most reliable read will come from full, peer-reviewed Phase 3 results.

Ready to track your peptide research?

Open PepTracker Pro (https://app.peptrackerpro.com/)

PepTracker Pro Research Team

The PepTracker Pro Research Team is an editorial group of science writers, pharmacologists, and clinical researchers dedicated to making peptide science accessible. Every article is reviewed for accuracy against peer-reviewed sources and updated as new evidence emerges.

## Citations

1. [1] Pfizer — Ultra-Long-Acting Injectable GLP-1 RA Shows Robust Weight Loss with Monthly Dosing (VESPER-3, Feb 2026) Source (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) Source (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 Source (https://www.clinicaltrialsarena.com/news/pfizers-obesity-bet-shows-14-1-weight-loss-in-phase-iib-trial/)
4. [4] Pfizer finalizes Metsera buy after contentious bidding war with Novo Nordisk — Fierce Biotech Source (https://www.fiercebiotech.com/biotech/pfizer-finalizes-metsera-buy-after-contentious-bidding-war-novo-nordisk)

**Disclaimer:** This article is for educational purposes only and does not constitute medical advice. Always consult a licensed healthcare provider. Read full research disclaimer → (https://peptrackerpro.com/research-disclaimer)

## Related Articles

Research & Compounds cover image (https://peptrackerpro.com/blog/oral-glp1-pill-race-conveglipron-hdm1002-vs-orforglipron-danuglipron-june-15-2026)

Research & Compounds ### The Oral GLP-1 Pill Race Widens: Conveglipron (HDM1002) Joins Orforglipron in the Hunt for a Needle-Free Weight-Loss Drug — June 15, 2026 (https://peptrackerpro.com/blog/oral-glp1-pill-race-conveglipron-hdm1002-vs-orforglipron-danuglipron-june-15-2026)

Conveglipron (HDM1002) is an oral, once-daily small-molecule GLP-1 receptor agonist from Huadong Medicine now in Phase 2 for obesity and Phase 3 for type 2 diabetes. Here's how the GLP-1 'pill' race is shaping up against orforglipron and danuglipron — and why an oral small molecule is not the same thing as a peptide.

PepTracker Pro Team

June 15, 2026 9 min read

Read (https://peptrackerpro.com/blog/oral-glp1-pill-race-conveglipron-hdm1002-vs-orforglipron-danuglipron-june-15-2026)

Research & Compounds cover image (https://peptrackerpro.com/blog/motixafortide-aphexda-cxcr4-peptide-stem-cell-mobilization-pancreatic-cancer-june-17-2026)

Research & Compounds ### Motixafortide (Aphexda): The FDA-Approved Peptide Working in Cancer Care — and Why Not Every Peptide Is About Weight Loss (June 17, 2026) (https://peptrackerpro.com/blog/motixafortide-aphexda-cxcr4-peptide-stem-cell-mobilization-pancreatic-cancer-june-17-2026)

Most peptide headlines are about weight loss. Motixafortide (Aphexda, BL-8040) is a different kind of story: an FDA-approved cyclic peptide used in cancer care to mobilize stem cells for transplant — and now being tested against pancreatic cancer. Here's how it works and why it matters.

PepTracker Pro Team

June 17, 2026 8 min read

Read (https://peptrackerpro.com/blog/motixafortide-aphexda-cxcr4-peptide-stem-cell-mobilization-pancreatic-cancer-june-17-2026)

Research & Compounds cover image (https://peptrackerpro.com/blog/pluvicto-lutetium-177-psma-radioligand-prostate-cancer-psmaddition-june-19-2026)

Research & Compounds ### Pluvicto (Lutetium-177 PSMA): The Targeted Radiation Drug Reshaping Prostate Cancer — and Is It Really a Peptide? (June 19, 2026) (https://peptrackerpro.com/blog/pluvicto-lutetium-177-psma-radioligand-prostate-cancer-psmaddition-june-19-2026)

Pluvicto (lutetium-177 vipivotide tetraxetan) is one of oncology's most talked-about 'peptide-targeted' drugs — a radioligand that delivers radiation straight to prostate-cancer cells. In 2026 the Phase 3 PSMAddition trial pushed it into earlier disease. Here is how it works, what the new data show, and why calling it a 'peptide' deserves an asterisk.

PepTracker Pro Team

June 19, 2026 8 min read

Read (https://peptrackerpro.com/blog/pluvicto-lutetium-177-psma-radioligand-prostate-cancer-psmaddition-june-19-2026)

Research & Compounds cover image (https://peptrackerpro.com/blog/met-233i-metsera-pfizer-once-monthly-amylin-analog-19-day-half-life-met-097i-combination-obesity-july-31-2026)

Research & Compounds ### MET-233i: The Once-Monthly Amylin Injection Built to Pair With a Monthly GLP-1 (July 31, 2026) (https://peptrackerpro.com/blog/met-233i-metsera-pfizer-once-monthly-amylin-analog-19-day-half-life-met-097i-combination-obesity-july-31-2026)

Most amylin obesity drugs are weekly shots. MET-233i, from Metsera and now Pfizer, is an amylin analog with a ~19-day half-life - the longest reported for the class - that produced up to 8.4% weight loss in Phase 1 and is engineered to be combined with a monthly GLP-1 agonist into one once-monthly injection. Here is what is known, and what is not.

PepTracker Pro Team

July 31, 2026 7 min read

Read (https://peptrackerpro.com/blog/met-233i-metsera-pfizer-once-monthly-amylin-analog-19-day-half-life-met-097i-combination-obesity-july-31-2026)

## 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": "Article",
    "headline": "MET-097i: Pfizer's Once-Monthly GLP-1 and the Race for Longer Dosing Intervals (June 20, 2026)",
    "description": "Pfizer's newly acquired MET-097i is an ultra-long-acting GLP-1 designed for once-monthly maintenance dosing. Here's what the VESPER-3 Phase 2b data show, why the dosing interval matters, and what to watch as ~10 Phase 3 trials begin in 2026.",
    "datePublished": "2026-06-20",
    "dateModified": "2026-06-20",
    "author": {
      "@type": "Organization",
      "name": "PepTracker Pro Research Team",
      "url": "https://peptrackerpro.com"
    },
    "publisher": {
      "@type": "Organization",
      "name": "PepTracker Pro",
      "logo": {
        "@type": "ImageObject",
        "url": "https://peptrackerpro.com/favicon.png"
      }
    },
    "mainEntityOfPage": {
      "@type": "WebPage",
      "@id": "https://peptrackerpro.com/blog/met-097i-pfizer-metsera-monthly-glp1-vesper-3-june-20-2026"
    }
  },
  {
    "@context": "https://schema.org",
    "@type": "BreadcrumbList",
    "itemListElement": [
      {
        "@type": "ListItem",
        "position": 1,
        "name": "Home",
        "item": "https://peptrackerpro.com"
      },
      {
        "@type": "ListItem",
        "position": 2,
        "name": "Blog",
        "item": "https://peptrackerpro.com/blog"
      },
      {
        "@type": "ListItem",
        "position": 3,
        "name": "MET-097i: Pfizer's Once-Monthly GLP-1 and the Race for Longer Dosing Intervals (June 20, 2026)",
        "item": "https://peptrackerpro.com/blog/met-097i-pfizer-metsera-monthly-glp1-vesper-3-june-20-2026"
      }
    ]
  }
]
```