Eli Lilly's New Weight Loss Drug Sees High Dropout Rates

Participants taking the highest dose of retatrutide lost an average of 28.7% of their body weight, but some dropped out due to excessive weight loss.

Published on Feb. 22, 2026

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Participants in a late-stage trial of Eli Lilly's new GLP-1 drug retatrutide lost an average of 28.7% of their body weight on the highest dose, putting it on track to be a major player in the weight-loss and diabetes treatment market. However, the trial also saw higher dropout rates than previous studies, with some participants concerned about the rapid and significant weight loss.

Why it matters

Retatrutide's impressive weight-loss results could make it a game-changer in obesity and diabetes treatment, but the high dropout rates due to excessive weight loss raise questions about the drug's safety and tolerability, especially at the highest doses.

The details

In the Phase 3 'Triumph-4' trial, Lilly tested two doses of retatrutide, a drug that mimics three hormones to curb appetite and lower blood sugar. Patients who completed the higher 12mg dose lost an average of 71.2 pounds, while those on the lower 9mg dose lost 64.2 pounds on average. However, 18.2% of participants on the 12mg dose and 12.2% on the 9mg dose dropped out due to adverse events, compared to just 4% in the placebo group. Lilly noted the dropouts were 'highly correlated with baseline BMI and included discontinuations for perceived excessive weight loss.'

  • The Phase 3 'Triumph-4' trial lasted 68 weeks.
  • Lilly expects to have seven additional Phase 3 readouts for retatrutide in 2026.

The players

Eli Lilly

An American pharmaceutical company that developed the experimental weight-loss drug retatrutide.

Dr. Jennah Siwak

An obesity medicine expert who commented on the trial results in a TikTok video.

Dr. Kenneth Custer

The executive vice president and president of Lilly Cardiometabolic Health, who commented on the potential benefits of retatrutide for patients with obesity and knee osteoarthritis.

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What they’re saying

“This is beyond what we see with any other medication on the market, and it is what we see with some bariatric surgeries. This is insane.”

— Dr. Jennah Siwak, Obesity medicine expert (TikTok)

“People with obesity and knee osteoarthritis often live with pain and restricted mobility, and may eventually require total joint replacement. With seven additional Phase 3 readouts expected in 2026, we believe retatrutide could become an important option for patients with significant weight loss needs and certain complications, including knee osteoarthritis.”

— Dr. Kenneth Custer, Executive Vice President and President of Lilly Cardiometabolic Health (Lilly statement)

What’s next

Lilly expects to have seven additional Phase 3 readouts for retatrutide in 2026, which will provide more data on the drug's safety and efficacy.

The takeaway

Retatrutide's impressive weight-loss results could make it a breakthrough treatment, but the high dropout rates due to excessive weight loss raise concerns about its tolerability, especially at the highest doses. Lilly will need to carefully balance the drug's benefits and risks as it moves forward with additional trials and regulatory approvals.