What Is Retatrutide?
Retatrutide (LY3437943) is an investigational “triple agonist” — a single peptide that activates the GLP-1, GIP, and glucagon receptors — being developed for obesity and related metabolic conditions. Adding glucagon-receptor agonism to the GLP-1/GIP incretin effect is intended to increase energy expenditure alongside appetite suppression. It is not an approved drug and is not a dietary supplement; it is available only within clinical trials (and, illicitly, as an unapproved research chemical). This entry is informational only.
Evidence
In a phase 2, double-blind, randomised, placebo-controlled trial in adults with obesity, once-weekly subcutaneous retatrutide produced dose-dependent mean weight reductions at 48 weeks of −8.7% (1 mg), −17.1% (4 mg), −22.8% (8 mg), and −24.2% (12 mg), versus −2.1% with placebo 1Reference 1RCTTriple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial — randomised controlled trialView study →. The most common adverse events were gastrointestinal and dose-related (mostly mild-to-moderate), and dose-dependent increases in heart rate were observed that peaked around 24 weeks. These are promising but phase 2 results; large phase 3 outcome trials were still underway and were not retrieved/verified in this quick pass, and long-term safety and efficacy are not yet established. Marketing of retatrutide as a self-administered peptide is not supported by any approval.
Dosage & Safety
The doses above are the investigational once-weekly regimens used in the phase 2 trial 1Reference 1RCTTriple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial — randomised controlled trialView study →; they are reported for information only and are not a recommendation — retatrutide is not approved, and material sold outside clinical trials is an unapproved research chemical of unverified identity and purity. Long-term safety, cardiovascular effects, drug interactions, and use in pregnancy are not established and were not assessed in this pass; the observed heart-rate increase is a notable open question. Informational only.
References
- Jastreboff AM, et al. (2023). Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial — randomised controlled trial. N Engl J Med, 389:514–526. https://doi.org/10.1056/NEJMoa2301972