Obesity · Jan 30, 2026

Efficacy and Safety of Tirzepatide in Japanese Participants With Obesity: A Subpopulation Analysis of the SURMOUNT-1 Trial

By Ishigaki Y, Yamada M, Shingaki T et al.

OBJECTIVE: This prespecified subpopulation analysis aimed to assess the efficacy and safety of once-weekly tirzepatide versus placebo alongside lifestyle intervention in Japanese adults with obesity or overweight. METHODS: Data from 102 Japanese adults in the SURMOUNT-1 trial with BMI ≥ 30 kg/m² or ≥ 27 kg/m² and ≥ 1 weight-related comorbidity were analyzed. Coprimary endpoints were mean percent change in body weight and the proportion of participants who achieved ≥ 5% body weight reduction at week 72. RESULTS: Participants in the tirzepatide 5-, 10-, and 15-mg groups had a statistically significantly greater (all p < 0.001) least squares mean (standard error) percent change in body weight compared with those in the placebo group: -12.0% (1.7%), -22.4% (1.7%), -22.1% (1.6%), and -0.3% (1.6%), respectively. Overall, 91.7%, 100%, and 96.6% of participants in the tirzepatide 5-, 10-, and 15-mg groups, respectively, had ≥ 5% weight reduction at week 72, compared with 15.4% in the placebo group. Significant improvements in cardiometabolic measures were also observed with tirzepatide at week 72 compared to placebo. No new safety concerns were identified. CONCLUSIONS: Once-weekly treatment with tirzepatide demonstrated significant reductions in body weight and prespecified cardiometabolic measures compared with placebo in Japanese adults with obesity or overweight. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04184622 https://clinicaltrials.gov/study/NCT04184622.

doi.org/10.1002/oby.70131 Open access PubMed 41612966 Interventions