Pfizer reported Phase 2b data for the ultra‑long‑acting GLP‑1 therapy it acquired with Metsera, showing clinically meaningful weight loss with a once‑monthly maintenance regimen. The company disclosed up to ~10.5% mean weight reduction at six months in one cohort and placebo‑adjusted losses up to ~12.3% at 28 weeks in per‑protocol analyses, while signaling plans to test higher doses in an extensive Phase 3 program starting later this year. Pfizer called the results confidence‑building for a monthly dosing strategy intended to improve adherence; executives said the Phase 3 program will run multiple pivotal studies across obesity indications. The data prompted a volatile market reaction, with shares sliding on concerns about relative efficacy versus competitors and a separate $4.4 billion impairment tied to other portfolio moves noted in company filings. GLP‑1 receptor agonists are peptide drugs that stimulate insulin secretion and reduce appetite; monthly formulations aim to trade off peak efficacy for convenience and adherence. Investors and payors will watch upcoming Phase 3 dose escalation and tolerability readouts to assess whether monthly maintenance can compete with weekly or more frequent regimens from rivals. Key actors: Pfizer (Metsera acquisition), trial sponsors and analysts including Leerink and Evercore; reporting aggregated from company releases and MedCity/STAT coverage.