Current GLP therapies target one or two hormone receptors; Wegovy (semaglutide) targets GLP-1, while Zepbound (tirzepatide) targets GLP-1 and GIP. Eli Lilly is developing a next-generation GLP therapy called retatrutide that targets three receptors: GLP-1, GIP, and glucagon.
Eli Lilly recently published preliminary results from a 68-week retatrutide study, where 445 overweight adults (average BMI 40; average body weight 249 lbs) were randomized to once-weekly injections of retatrutide 9 mg, retatrutide 12 mg, or placebo. After 68 weeks, average weight loss in the retatrutide 12 mg group was a remarkable 28.7%, equating to an average weight loss of 71 lbs. The retatrutide 9 mg group lost an average of 26.4%, and the placebo group lost 2.1%. The most common side effects with the 12 mg dose were nausea (43.2%), diarrhea (33.1%), constipation (25.0%), and vomiting (20.9%). In the 12 mg group, 18.2% of patients discontinued treatment due to adverse events; however, some discontinuations were actually due to "perceived excessive weight loss," highlighting the potency of the drug.
The most effective therapy available now is Zepbound, which causes about 20% weight loss. Retatrutide's near 30% weight loss is remarkable and rivals what is typically seen with bariatric surgery.