New trial data complicates the competitive picture in the fast-growing obesity drug market
Eli Lilly and Co's (NYSE:LLY) experimental weight-loss and diabetes drug retatrutide has shown a side-effect profile broadly comparable to leading treatments, but new data flagging an unusual skin reaction could give prescribers pause as the race to challenge Novo Nordisk's dominance intensifies.
Lilly reported headline results from the first phase three trial of retatrutide in type 2 diabetes, showing patients achieved 16.8% weight loss and a 1.1 percentage point reduction in HbA1c, a standard measure of long-term blood sugar control, after 40 weeks at the 12mg dose.
The gut tolerability numbers, closely watched given that nausea and vomiting have dogged the entire GLP-1 drug class, came in at levels broadly in line with Lilly's own approved Zepbound and Novo Nordisk's pipeline drug CagriSema. Nausea affected 26.5% of patients, diarrhoea 22.8% and vomiting 17.6%.
The wrinkle is dysesthesia, an abnormal skin sensation including pins and needles, which appeared in 2.3% to 4.5% of patients across doses, echoing a similar signal seen in an earlier retatrutide trial in osteoarthritis patients
. Citi described the finding as notable, though not yet disqualifying.
The bank cautioned that direct comparison with CagriSema remains difficult, given differences in patient populations and trial duration.
Novo Nordisk's REIMAGINE2 trial ran to 68 weeks in patients inadequately controlled on metformin, while retatrutide's upcoming TRIUMPH trials in obese patients, due to report around mid-2026, will provide a cleaner read on how the two drugs stack up.