Next‑gen multi‑agonists rising
- New multi‑agonists combine gut hormones: tirzepatide pairs GLP‑1 and GIP, while retatrutide adds glucagon for triple action. ( ) - Clinical results show tirzepatide yields roughly 20–22% weight loss, and triple‑agonists are approaching or exceeding 22.5% losses. ( ) - These drugs reflect a shift toward targeting gut‑brain appetite circuits rather than single‑hormone approaches. ( )
These new obesity drugs are being built to hit two or three hormone switches at once, not just one. (nejm.org, nejm.org) The basic idea is simple: hormones released from the gut help tell the brain when to stop eating, and drugmakers are trying to amplify more of those signals together. The American Journal of Managed Care described that shift as a move toward the “gut-brain axis” in obesity treatment. (ajmc.com) Tirzepatide is the first big proof point. It activates glucose-dependent insulinotropic polypeptide, or GIP, and glucagon-like peptide-1, or GLP-1, and in the SURMOUNT-1 trial the 15-milligram dose produced a mean 20.9% weight reduction at 72 weeks. (nejm.org) The Food and Drug Administration approved tirzepatide as Zepbound in November 2023 for chronic weight management in adults with obesity, or adults who are overweight with at least one weight-related condition. The current label says it is used with a reduced-calorie diet and increased physical activity. (fda.gov, accessdata.fda.gov) Retatrutide pushes the same idea further. It adds a third target — the glucagon receptor — to GIP and GLP-1, and a Phase 2 trial reported mean weight reduction of 24.2% at 48 weeks with the 12-milligram dose. (nejm.org) That puts the field into a new comparison: not whether these medicines can produce double-digit weight loss, but how close they can get to bariatric-surgery ranges in trials. In the retatrutide study, the 8-milligram dose reached 22.8% at 48 weeks, while tirzepatide’s top dose reached 20.9% at 72 weeks in SURMOUNT-1. (nejm.org, nejm.org) The race is moving ahead because obesity remains widespread in the United States. CDC said in September 2024 that 23 states had adult obesity prevalence above 35% in 2023, and a separate National Center for Health Statistics brief estimated adult obesity prevalence at 40.3% in August 2021 through August 2023. (cdc.gov, cdc.gov) The tradeoff has not changed: the most common side effects are still gastrointestinal. In the tirzepatide and retatrutide obesity trials, nausea, diarrhea, vomiting, and constipation were the most frequently reported adverse events, and investigators said they were mostly mild to moderate and often tied to dose escalation. (nejm.org, nejm.org) Retatrutide is not yet an approved obesity drug. One of its Phase 3 studies, TRIUMPH-3, is listed on ClinicalTrials.gov as active and designed to test weekly retatrutide in people with obesity and established cardiovascular disease over about 113 weeks. (clinicaltrials.gov) So the story now is less about a single GLP-1 medicine than about combination drugs aimed at the gut’s full appetite-control network. Tirzepatide is already on the market, and retatrutide’s late-stage testing will show whether triple-action therapy can turn early trial numbers into an approved treatment. (accessdata.fda.gov, clinicaltrials.gov, ajmc.com)
