Amgen reports Phase 2 weight loss results for monthly obesity drug MariTide

Amgen said on Nov. 26, 2024 that MariTide, its experimental obesity drug, produced average weight loss of up to about 20% at 52 weeks in a Phase 2 study, and the company said it is starting a Phase 3 program called MARITIME ^[1].

MariTide, also called maridebart cafraglutide and formerly AMG 133, is an antibody-peptide conjugate injected under the skin once a month or less often ^[1]. It activates the GLP-1 receptor, the same target as Ozempic, Wegovy and Rybelsus (semaglutide), and blocks the GIP receptor — a different design from Mounjaro and Zepbound (tirzepatide), which activate GIP ^[1].

What the trial found

The double-blind, dose-ranging study enrolled 592 adults in two groups: 465 people with obesity or overweight who did not have type 2 diabetes, and 127 people who also had type 2 diabetes ^[1]. Participants received monthly fixed doses of placebo, 140 mg, 280 mg or 420 mg, or an 8-week 420 mg arm, and two arms escalated to a 420 mg target dose over 4 or 12 weeks ^[1].

In people without type 2 diabetes, average weight loss reached up to about 20% at week 52, and Amgen said no weight-loss plateau was seen, which the company said indicates the potential for further loss with longer treatment ^[1]. In people with type 2 diabetes, average loss reached up to about 17%, also without a plateau, and average HbA1c fell by up to 2.2 percentage points ^[1]. Amgen described people with diabetes as those who "typically lose less weight on GLP-1 therapies" ^[1].

The release did not say which statistical method produced those percentages, and it did not report weight change for the placebo groups ^[1]. In obesity trials, companies often report both a treatment-regimen or intention-to-treat figure, which counts everyone randomized, and a higher efficacy figure that estimates what would have happened if everyone stayed on treatment; the two answer different questions ^[2].

Amgen also reported improvements in blood pressure, triglycerides and high-sensitivity C-reactive protein across doses, no significant increases in free fatty acids, and no association between the drug and changes in bone mineral density ^[1].

The most common side effects were gastrointestinal: nausea, vomiting and constipation. Nausea and vomiting were mostly mild and brief and mainly followed the first dose, and were substantially reduced with dose escalation; when they occurred in the escalation arms, nausea generally resolved within a median of six days and vomiting within one to two days ^[1]. In those arms, about 11% of participants stopped treatment because of any side effect, and fewer than 8% stopped for gastrointestinal side effects ^[1].

More than 90% of eligible participants continued into Part 2 of the study, which is testing treatment beyond 52 weeks, weight maintenance with lower or less frequent dosing, and what happens after the drug is stopped ^[1]. Amgen said the data would be presented at a future medical congress and submitted for publication ^[1]; the Phase 2 results were later presented at the American Diabetes Association's 85th Scientific Sessions ^[3].

Why it matters for patients

MariTide is not approved for any use. As of July 2026 it remained in Phase 3, while the Wegovy pill (oral semaglutide), Foundayo (orforglipron) and CagriSema sit further along in the regulatory process ^[2].

Amgen has positioned monthly or less frequent dosing as the drug's main practical difference from the weekly injections used by semaglutide and tirzepatide products ^[1]. Whether monthly dosing would make a real difference to staying on treatment has not been tested in a head-to-head study, and the Phase 2 results are from a single trial that has not yet been published in full ^[1].

Side effects follow the pattern seen with other GLP-1-based drugs — mostly gastrointestinal, worst around the first dose, and reduced when the dose is stepped up gradually ^[1]. The roughly 11% discontinuation rate in the escalation arms reflects what happened in a trial, not what would happen in routine practice ^[1].

Amgen has not disclosed a price, and no insurer coverage decision exists because the drug is not approved ^[2].

What happens next

MARITIME, the Phase 3 program, covers obesity and obesity-related conditions, with further studies planned in cardiovascular disease, heart failure and obstructive sleep apnoea, and pivotal data expected to read out through 2027 ^[1][3]. Amgen has said the drug is expected to be given with a handheld autoinjector ^[1]. No approval date has been announced in the United States or anywhere else, and no filing date has been disclosed ^[2].