Bloomberg / Wall Street Journal Recap: Lilly Mounjaro+Zepbound Reach 54.8% US GLP-1 Market Share vs Novo's 47% Year Earlier — 125%/80% YoY Growth in Mounjaro/Zepbound Q1 2026 Outpacing Novo's Wegovy Cycle
Coverage week of June 15-19 distilled the post-ADA market share story: Eli Lilly's tirzepatide franchise (Mounjaro for T2D, Zepbound for obesity) now holds 54.8% of US GLP-1 prescription share versus 47% a year earlier, with Q1 2026 YoY growth of 125% for Mounjaro and 80% for Zepbound and full-year revenue guidance raised to $82-85B. Novo Nordisk lifted its own 2026 guidance to a 4-12% currency-adjusted decline (improved from 5-13%) on Wegovy pill momentum (3M US scripts in five months, 65% of new prescriptions, 82% to GLP-1-naive patients), but Novo's stock has declined 42% over the past year against Lilly's 40% gain — the share-shift signal the ADA cycle crystallized. Lilly's seven additional retatrutide Phase 3 readouts across 2026 (TRIUMPH-7 chronic low-back pain, TRIUMPH-8 general obesity, TRIUMPH-9 obesity without T2D, plus OSA, MASLD, and cardiometabolic outcomes) extend the franchise gap.