Maridebart cafraglutide (MariTide, AMG 133) is a peptide-antibody conjugate that combines GLP-1 receptor agonism with GIP receptor antagonism. That design is notable because tirzepatide, the current market leader, is a GIP receptor agonist — two opposite approaches to the same receptor both appear to drive weight loss. MariTide's roughly 21-day half-life allows once-monthly, and potentially once-quarterly, dosing rather than the weekly injections that define current GLP-1 therapy.
Interest surged in 2026 as Amgen's phase 3 MARITIME program — six global trials — got underway, and the company foregrounded the monthly and quarterly dosing schedule at the January 2026 JP Morgan healthcare conference as its main differentiator. For patients weary of weekly injections, a once-a-month or once-a-quarter shot is the headline that is pulling search traffic.
The phase 2 evidence is now published. In a 592-participant trial reported in the New England Journal of Medicine, people with obesity and without diabetes lost up to roughly 20% of body weight at 52 weeks on the efficacy estimand — 12.3% to 16.2% on the more conservative treatment-policy estimand — versus about 2.5% with placebo, and the weight-loss curve had not plateaued at one year. In obesity with type 2 diabetes, reductions reached about 17% versus 1.4% with placebo.
The trade-off centres on tolerability and the unfinished science. Treatment-emergent adverse events were mostly mild-to-moderate and gastrointestinal, though earlier dosing produced high nausea and vomiting rates that Amgen has sought to blunt with slower titration. The GIP-antagonist rationale remains an open scientific debate, and no MariTide product is approved. The six phase 3 studies, running into 2027, will decide whether monthly dosing and the absent plateau translate into an approved drug rather than a promising phase 2 signal.