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Lilly’s Retatrutide Cuts Body Weight 28.7% in Phase 3, Eases Knee Pain

The unapproved triple-agonist now heads into more late-stage readouts in 2026 before any FDA decision.

Overview

  • In the Triumph-4 phase 3 trial, a 12 mg weekly dose over 68 weeks produced an average 28.7% weight reduction and also reduced knee osteoarthritis pain.
  • Retatrutide activates GLP-1, GIP, and glucagon receptors, and its weight-loss results surpassed late-stage outcomes reported for tirzepatide.
  • The drug is not FDA-approved, and Eli Lilly expects seven additional phase 3 readouts in 2026 across obesity and type 2 diabetes.
  • Clinicians highlight common gastrointestinal side effects and say long-term safety, durability of weight loss, and maintenance off-therapy remain open questions.
  • Analysts see significant commercial potential, with Morgan Stanley estimating a $150 billion obesity-drug market by 2035 and Evaluate projecting about $5 billion in retatrutide revenue by 2030, as Lilly leads U.S. incretin prescriptions.