Move over Ozempic, Wegovy, Mounjaro and Zepbound — Eli Lilly says another contender may be on the way. The pharmaceutical giant announced encouraging results from a Phase 3 clinical trial of its experimental weight loss drug retatrutide, showing levels of weight loss that could rival — or exceed — existing blockbuster treatments.
What the study found
According to Eli Lilly, patients taking retatrutide lost nearly 30% of their body weight over 68 weeks.
Those who received the highest dose of the weekly injection lost an average of 71.2 pounds, equivalent to 28.7% of their starting weight.
The trial enrolled patients with obesity and knee osteoarthritis who did not have diabetes. Participants had a body mass index (BMI) of at least 35 at the start of the study.
For comparison, The Wall Street Journal reported that Eli Lilly’s current drug Zepbound produced an average weight loss of about 22.5%, while Novo Nordisk’s Wegovy typically results in weight loss under 20%.
Added benefit: less knee pain
Beyond weight loss, Eli Lilly says retatrutide also helped ease knee pain linked to osteoarthritis — a condition that can be worsened by excess weight.
“We believe retatrutide could become an important option for patients with significant weight-loss needs and certain complications, including knee osteoarthritis,” said Kenneth Custer, President of Lilly Cardiometabolic Health.
A booming — and expensive — market
GLP-1 and related weight loss drugs exploded in popularity by mimicking hormones that regulate blood sugar and appetite, helping people feel full longer.
The downside is the cost. Annual treatment often runs between $5,000 and $7,000, with limited insurance coverage — especially for people relying on Medicare or Medicaid.
Industry analysts estimate the global GLP-1 market topped $50 billion in 2024 and could exceed $150 billion by the end of the decade.
Side effects and dropouts
The trial wasn’t without drawbacks.
According to the Journal, patients experienced higher rates of nausea and diarrhea compared to existing drugs. Some patients also dropped out because they lost too much weight.
What comes next
Eli Lilly says it plans to launch more than six additional Phase 3 trials in 2026 to further test retatrutide across different patient groups.
If results hold, the drug could become a major new player in an already crowded, and highly competitive, weight loss market.
