In a 26‑week trial, people with schizophrenia who were taking weight‑gain‑causing antipsychotic drugs lost about 9 kg, dropped around 7 cm from their waist, and lowered their blood‑sugar marker (HbA1c) by a quarter of a percent when they added a weekly 1 mg dose of semaglutide, compared with a placebo. The drug was well‑tolerated, with only mild stomach upset, and didn’t worsen psychiatric symptoms.

Individuals with schizophrenia spectrum disorders treated with second-generation antipsychotics (SGAs) are at heightened risk for obesity, prediabetes, and type 2 diabetes, contributing to increased cardiovascular morbidity and premature mortality. Early intervention with glucagon-like peptide-1 receptor agonists (GLP-1RAs) may help mitigate long-term cardiometabolic risk. To evaluate the efficacy of adjunctive semaglutide on glycemic control, weight-associated outcomes, and cardiometabolic risk factors in individuals with schizophrenia spectrum disorders receiving clozapine or olanzapine and exhibiting early glycemic abnormalities. This was a multicenter, double-blind, placebo-controlled, randomized clinical trial. Participants were enrolled from 3 clinical sites in Denmark between September 2021 and August 2024. Screening individuals were aged 18 to 65 years with schizophrenia spectrum disorders and clozapine or olanzapine treatment initiated within the past 5 years. Participants had early-stage glycemic dysregulation (hemoglobin A1c [HbA1c], 5.4%-7.4%) and were not receiving antidiabetic therapy. Participants received once-weekly subcutaneous semaglutide (1 mg) or a matching placebo, administered adjunctively to SGA therapy for 26 weeks. The prespecified primary outcome was change in HbA1c level from baseline to week 26. The primary analysis adhered to the intention-to-treat principle. Of 104 individuals screened, 73 were randomized and 57 (78%) completed the trial. Baseline characteristics were comparable between groups. Mean (SD) age was 35 (12) years, 48 were female (65%), and mean (SD) body mass index was 36.1 (7.9). At week 26, semaglutide significantly reduced HbA1c level compared with placebo (mean difference, -0.25%; 95% CI, -0.33 to -0.16; P < .001); 43% of participants (12 of 28) treated with semaglutide achieved low-risk HbA1c levels (<5.4%) vs 3% with placebo. Greater reductions in body weight (-9.2 kg; 95% CI, -13.3 to -5.1 kg; P < .001), waist circumference (-7.0 cm; 95% CI, -10.6 to -3.3 cm; P < .001), and fat mass (-6.1 kg; 95% CI, -10.2 to -1.9 kg; P = .006) were observed with semaglutide. No differences in lipid levels, liver function, blood pressure, or psychiatric symptoms were observed. Gastrointestinal adverse events were common but mild and transient; psychiatric adverse events were similar across groups. Results of this randomized clinical trial show that adjunctive semaglutide significantly improved glycemic control and weight outcomes in individuals with schizophrenia spectrum disorders. Secondary outcomes were exploratory. These findings support the use of GLP-1RAs as a potential early intervention strategy to reduce cardiometabolic risk in this vulnerable population. ClinicalTrials.gov Identifier: NCT04892199.