Retatrutide Phase 2: what the 48-week readout means for triple agonists

Jastreboff et al. (NEJM, 2023) reported that retatrutide — a GIP/GLP-1/glucagon triple agonist — produced a mean body-weight reduction of 17.5% at the 4 mg dose and 24.2% at 12 mg after 48 weeks in adults with obesity. The magnitude of effect exceeds anything published for dual agonists at the same timepoint.

The 48-week window matters: most Phase 3 obesity trials extend to 72 weeks and effect sizes tend to continue climbing until a plateau. Extrapolation is speculative, but the trajectory suggests retatrutide may push mean loss past 25% in longer-duration studies — closer to the range seen with bariatric surgery.

For UK researchers, retatrutide remains an investigational compound only. It has no MHRA licence and cannot be prescribed. See our retatrutide UK guide for regulatory status and the retatrutide vs tirzepatide comparison for how it stacks up against the current market leader.