Amgen starts phase 3 study of switching from weekly GLP-1s to monthly MariTide
A switch study tests whether people already taking a weekly GLP-1 can move to a monthly shot, but no results or trial details have been reported yet.
Amgen has begun a phase 3 study in which patients now taking a weekly GLP-1 medicine switch to its own once-monthly candidate, MariTide [1]. Dosing frequency is the main argument Amgen makes for MariTide against the market-leading weekly drugs [1].
MariTide is an injected drug given once a month. An Amgen pipeline summary describes that schedule as a "convenience edge" over semaglutide, sold as Ozempic, Wegovy and Rybelsus, and tirzepatide, sold as Mounjaro and Zepbound; both are dosed weekly [1]. In phase 2 testing, MariTide produced up to about 20% weight loss at 52 weeks under the efficacy analysis, which estimates what would have happened if everyone had stayed on treatment. The same trial reported 12.3% to 16.2% under the treatment-policy analysis, which counts people who stopped the drug [1]. Amgen's phase 3 program tracked as MARITIME runs for 72 weeks [1]. Whether the new switch study sits inside that program has not been reported.
Nothing here is close to a pharmacy shelf. MariTide is in phase 3 and was not approved in the United States, the United Kingdom, Ireland or Australia as of July 2026 [2]. Competitors are further along. Foundayo (orforglipron) was approved by the FDA in April 2026 [2]. CagriSema, Novo Nordisk's weekly combination of cagrilintide and semaglutide, was filed with the FDA on 18 December 2025 and is awaiting a decision [2]. Eli Lilly reported topline results from the retatrutide TRIUMPH-1 trial in May 2026: -25.0% weight loss at 80 weeks under the treatment-regimen analysis, and -28.3% under the efficacy analysis [2].
Amgen's own position in the obesity market has narrowed. The company's bear case is that it sits behind Lilly and Novo Nordisk in obesity and still faces a question about gastrointestinal tolerability; on 4 August 2026 it discontinued an undisclosed early-stage obesity candidate, concentrating its obesity effort on MariTide alone [1]. Amgen's market value was listed at about $191.7 billion, and its phase 3 plan for MariTide covers obesity, type 2 diabetes, cardiovascular outcomes, heart failure and obstructive sleep apnea [1].
Why it matters for patients
Dosing frequency is one of the few differences between these drugs that a patient feels directly. A weekly injection means about 52 injection days a year; a monthly one means roughly 12 [1][2]. For people who travel, dislike needles or have missed doses on a weekly schedule, a once-monthly option would change the routine rather than the drug's job.
But a switch study asks a different question than the trials that got these medicines approved. The results reported so far for MariTide, semaglutide and tirzepatide describe people starting a drug, not people moving onto it from another GLP-1 [1][2]. How much weight people keep off after a switch, and how they tolerate it, has not been reported. That makes the new trial the test, not the answer.
For anyone currently taking a weekly GLP-1, nothing changes now. MariTide is not approved in the United States or anywhere else tracked, so it cannot be prescribed [2].
What happens next
The number of people in the switch study, which weekly medicines they are moving from, how long they are followed and when results are expected have not been disclosed. MARITIME runs 72 weeks, and no readout date has been reported [1]. Amgen's broader phase 3 program spans obesity, type 2 diabetes, cardiovascular disease, heart failure and obstructive sleep apnea, and its timing has not been detailed [1]. Separately, the FDA is still considering CagriSema, filed on 18 December 2025, and no decision had been announced as of July 2026 [2].
Sources
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