Amgen also tested MariTide in a population with Type 2 diabetes, a group that tends to lose less weight with the new obesity drugs. On average they lost up to 17 percent of their initial weight.

Amgen Inc.’s stock tumbled 7.8% in early trade Tuesday, after the company said a mid-stage trial of its weight-loss treatment MariTide showed up to 20% average weight loss at 52 weeks. Analysts were expecting the treatment to achieve an average weight loss of about 20% to 25% after one year of treatment,

The results shed light on how MariTide may measure up to weight loss injections from Novo Nordisk and Eli Lilly and other experimental treatments.