The pharmaceutical manufacturer Amgen announced on Tuesday that an experimental obesity drug helped patients lose up to 20 percent of their weight in a year. The drug, MariTide, is given by injection once a month, compared with once a week for other obesity drugs like Wegovy and Zepbound that are already on the market.

Shares in Amgen fell by double digits Tuesday on results for the company’s MariTide shot, which is viewed as a potential rival to Wegovy and Zepbound.