Amgen's MariTide produced up to about 20% weight loss at 52 weeks in Phase 2

Amgen's experimental obesity medicine MariTide produced average weight loss of up to about 20% over 52 weeks in a mid-stage trial, and participants had not stopped losing weight when the study ended, according to results published in the New England Journal of Medicine ^[3]. The drug is designed to be injected once a month or less often, which would distinguish it from the weekly shots and daily pills available today ^[3][4].

MariTide's generic name is maridebart cafraglutide; the trial record lists it as AMG 133 ^[1][3]. It is a peptide-antibody conjugate, meaning one part of the molecule blocks the GIP receptor while another activates the GLP-1 receptor, the same target as semaglutide in Ozempic and Wegovy ^[3][4]. Its long half-life is what makes a monthly schedule possible ^[3].

The Phase 2 study, registered as NCT05669599, tested a range of doses in adults with overweight or obesity, including some who also had type 2 diabetes ^[1]. Results differed by group: participants with obesity but without diabetes lost up to roughly 20% of their body weight, while those who also had diabetes lost up to about 17% ^[3]. Jay Bradner, Amgen's head of research and development, called the findings "a defining advance for the obesity field" ^[3].

Amgen's Phase 3 program is named MARITIME and is running in obesity and type 2 diabetes, with further trials planned in cardiovascular disease, heart failure and obstructive sleep apnoea ^[3]. The company expects pivotal results to emerge through 2027 ^[3]. MariTide holds no approval in the United States; a tracker of six late-stage obesity medicines listed it as still in Phase 3 as of July 2026, and only two of the six are approved for use in the US ^[4].

Amgen's spending on late-stage research is climbing. In second-quarter 2026 results released Aug. 4, the company reported research and development costs of $1.868 billion on a GAAP basis, 7% higher than a year earlier, and attributed part of the increase to later-stage programs "primarily those related to MariTide" ^[2].

Why it matters for patients

Dosing frequency is the main practical difference. Everything approved in the US for weight management is taken daily or weekly ^[3][4]. A monthly injection would mean 12 doses a year rather than 52, which could help people who struggle to keep up with a weekly schedule.

There is no way to get it now. Because MariTide is not approved, it cannot be prescribed or dispensed in the US ^[4]. Products marketed under that name outside a clinical trial are not approved medicines.

Group averages are not individual outcomes. The 20% and 17% figures are mean changes in groups of participants at particular doses ^[3]. Results vary widely from person to person in every weight-loss trial.

Side effects are the unresolved question. The reported Phase 2 results do not include detailed rates of nausea or other gastrointestinal problems for MariTide. Those effects are the most common reason people stop GLP-1 medicines; in a Phase 3 trial of the oral drug orforglipron, 5.3% to 10.3% of participants stopped because of side effects, against 2.7% on placebo ^[4].

Rivals are further ahead in line. CagriSema, a weekly combination of cagrilintide and semaglutide, was filed with the FDA on Dec. 18, 2025 and was still awaiting a decision as of July 2026 ^[4]. Orforglipron, sold as Foundayo, won US approval in April 2026 ^[4]. Retatrutide, Eli Lilly's triple agonist, is in Phase 3 ^[4].

What happens next

Amgen expects pivotal data from the MARITIME trials to arrive through 2027 ^[3]. No filing date and no approval date for MariTide have been announced in any market ^[4]. Analysts expect the global market for obesity drugs to exceed $100 billion within a few years, one reason the field has grown so crowded ^[3].