Amgen Inc (NASDAQ:AMGN, ETR:AMG) shares tumbled 11.6% to a year's low after results of a trial for its potential weight-loss drug showed it helped overweight or obese people lose up 20% of weight over a year.
Moreover, other makers of obesity drugs, including Novo Nordisk (NYSE:NVO) and Eli Lilly, rose on the back of a White House proposal to expand coverage of these medications under Medicare and Medicaid.
Amgen's Phase II study, meanwhile, also seemed positive, showing its experimental treatment, named MariTide, enabled up to around 20% average loss of weight without a plateau.
The company said it is the first obesity treatment at this clinical stage with monthly or less frequent dosing to safely demonstrate such effective weight-loss capabilities.
Overweight patients with type-2 diabetes demonstrated up to around 17% average weight loss without a weight loss plateau and lowered average hemoglobin by up to 2.2 percentage points at the 52-week stage.
After hitting an all-time high of almost $347 in September, the shares had fallen almost 20%, with a further fall to $260 on Tuesday.
The MariTide study showed no notable increase in free fatty acids, with a favorable safety profile.
Trials of the therapy, which offers monthly or less frequent dosing through a autoinjector, will advance to Phase 3 trials in obesity and related conditions, Amgen said.
Common adverse events, primarily mild and transient gastrointestinal issues, were reduced with dose escalation, and no new safety concerns were reported.