Amgen drops AMG 513 for MariTide, and the obesity field narrows to a Phase 3 shortlist

Amgen has halted further development of AMG 513, an obesity candidate that had reached Phase 1, in what the industry reads as a decision to concentrate capacity and money on MariTide, the asset already in later-stage trials, and to get to market faster ^[1][2]. That is the field in miniature: with Phase 3 results and regulatory filings for the major candidates due one after another from next year, the next one to two years will set the order behind Eli Lilly and Novo Nordisk ^[3][4].

Cutting a Phase 1 molecule costs little in absolute terms. The information is in the direction: Amgen kept the asset two development phases further along ^[3] and is now running a large-scale Phase 3 programme for MariTide that reaches past obesity and overweight into type 2 diabetes, cardiovascular disease, heart failure and obstructive sleep apnea ^[6]. MariTide is designed to activate the GLP-1 receptor while inhibiting the GIP receptor, and is being built as a long-acting drug with a longer dosing interval than the current once-weekly injectables ^[5]. On the strength of that programme it is treated as the leading candidate behind the two incumbents, with results expected sequentially starting next year ^[7], which on an August 2026 report means 2027 ^[1].

Pfizer's entry arrived by purchase rather than discovery: verobenatide, a long-acting GLP-1 it picked up in the Metsera acquisition ^[8]. The company has 10 Phase 3 trials running this year across chronic weight management and obesity-related comorbidities ^[9], and is developing the injectable for once-monthly dosing ^[10]. Pfizer's own framing is that verobenatide may be comparable to Mounjaro and could produce more weight loss than Wegovy, and it points to monthly dosing, efficacy and gastrointestinal tolerability as its edge ^[11]. The target is a 2028 launch, contingent on proving efficacy and safety in Phase 3 ^[12], roughly two years from now ^[2]. Ten simultaneous Phase 3 trials is a statement about conviction and about how much of the value sits in comorbidity labels rather than in weight numbers alone.

The oral contender is Structure Therapeutics, whose once-daily aleniglipron showed weight loss of up to 16.3% versus placebo at 44 weeks in Phase 2 ^[13]. In the second half of the year the company plans more data, including body composition in treated patients and what happens when patients switch to aleniglipron from injectable GLP-1s ^[14]. The switching read is the commercially interesting one, because it tests whether an oral can hold patients rather than only start them. If later-stage work holds up, partnerships or an outright acquisition become the live questions ^[15].

Ha Heon-ho of Shinhan Securities put it as the stage where the runners-up' achievements take concrete shape, and said the sorting of winners from losers on Phase 3 data will begin in earnest as Structure, Amgen and Pfizer aim at approval filings and launches in 2027 and 2028 ^[16].

What to watch: whether MariTide's comorbidity readouts land as sequentially as guided ^[7], whether Pfizer's ten-trial spread produces the Mounjaro comparison it is describing rather than merely a dosing convenience claim ^[11][12], and whether Structure's second-half switching data attracts a buyer before it has to fund Phase 3 alone ^[14][15].