Eli Lilly announced on Thursday that its experimental drug, retatrutide, has demonstrated substantial weight loss in a late-stage clinical trial, with results comparable to bariatric surgery. The trial, which involved 2,339 adults who were obese or overweight, showed that participants on the highest doses lost an average of 28.3% of their body weight over 80 weeks. This efficacy appears to surpass that of existing weight-loss medications like Zepbound and Wegovy.
The drug targets three hormones related to weight loss: GLP-1, GIP, and glucagon, distinguishing it from current dual-agonist or single-agonist medications.
However, the drug's significant impact comes with notable side effects. Gastrointestinal issues, including nausea, diarrhea, and vomiting, were commonly reported. Furthermore, 11% of patients on the highest dose discontinued treatment due to adverse events, a rate higher than observed with current market drugs like Wegovy and Zepbound, where discontinuations due to side effects were up to 7%. A slightly increased rate of urinary tract infections was also observed, though most cases were mild and resolved during treatment.
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The trial results have not yet been published in a peer-reviewed medical journal. Eli Lilly stated that a lower dose of retatrutide was associated with fewer discontinuations, indicating a potential trade-off between efficacy and tolerability. The company is conducting further studies to explore broader health benefits of the triple-acting drug.
Retatrutide is administered as a weekly injection, with dosages incrementally increased over time. Participants in the trial, who had obesity or were overweight and had at least one weight-related comorbidity but no diabetes, were randomized to receive varying doses of retatrutide or a placebo.
Eli Lilly also produces Zepbound, another weight-loss medication that targets GLP-1 and GIP hormones. While Zepbound achieved an average weight loss of 50 pounds over 72 weeks in clinical trials, and semaglutide (Wegovy) resulted in about 33 pounds lost, retatrutide's triple-hormone targeting mechanism appears to offer a more potent effect.
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