Lilly's investigational triple-hormone drug retatrutide produced substantial weight loss and knee-pain relief in a phase 3 trial (TRIUMPH-4) for adults with obesity and knee osteoarthritis, achieving an average 28.7% weight loss at the 12 mg dose and a 4.4-point improvement in WOMAC pain by week 68.

Co-primary endpoints showed significant reductions in body weight and WOMAC pain from baseline to week 68, meeting primary and key secondary endpoints.

Nearly half of participants on retatrutide reached at least 25% weight loss, with meaningful portions exceeding 30% or 35%, far outperforming placebo.

Lilly plans to release additional Phase III results over the coming year and pursue regulatory submissions, with expectations of a relatively straightforward path barring safety concerns.

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Market sentiment around the stock was mixed, with bearish retail chatter on Stocktwits even as the stock posted a year-over-year gain.

Common side effects include nausea and stomach issues, with risks of gallbladder and pancreatic disease; patients should discuss individual risk profiles with doctors.

Lilly announced the TRIUMPH-4 results in a company statement, marking a major milestone in the drug’s development.

The global weight-loss drug market is projected to grow substantially, with industry projections around $100–150 billion by the mid-2030s, underscoring retatrutide’s strategic importance.

TRIUMPH-4 included five dose levels (2, 4, 6, 9, 12 mg) with over 5,800 participants across studies since 2023; detailed results will be presented at future meetings and published in a peer-reviewed journal.

Retatrutide could help Lilly defend obesity and diabetes drug market share against competitors pursuing similar therapies.

Administration is via weekly injections; FDA submission is planned after seven additional Phase 3 trials in 2026, with potential approval possibly in late 2026 or later depending on review.