The popularity of a new generation of weight-loss medicines is inspiring a growing number of drugmakers to pursue paths emulating Eli Lilly's highly-effective Zepbound, but Amgen is taking a unique approach. Zepbound, which promotes the most weight loss among treatment options currently on the market, stimulates two different gut hormones to fight obesity, GLP-1 and GIP. Amgen's most advanced experimental candidate activates GLP-1 while blocking GIP.