The ADA recommended doctors avoid prescribing unapproved, off-brand versions of drugs like Wegovy, wading into a dispute that has gripped the FDA and compounding pharmacies over the past few months.

Recent data from an Amgen obesity-drug trial only reinforced investors' impressions that Eli Lilly and Novo Nordisk have a prohibitive head start, thanks, in particular, to a new generation of Lilly ...