Olanzapine/Samidorphan Effects on Weight Gain: An Individual Patient Data Meta-Analysis of Phase 2 and 3 Randomized Double-Blind Studies

Abstract

Objective: To evaluate weight change with a combination of olanzapine and samidorphan (OLZ/SAM) versus olanzapine by pooling data across clinical studies.

Methods: This study was an individual patient data (IPD) meta-analysis of clinical trial data.

Data Sources and Study Selection: EMBASE, MEDLINE, and PsycInfo were searched for randomized clinical trials (≥12 weeks) in adults with schizophrenia or bipolar I disorder in which weight change from baseline was the primary or secondary end point. Search results were reviewed for eligible studies.

Participants: Patients receiving daily OLZ/SAM (olanzapine 5–20 mg + samidorphan 10 mg) or olanzapine (5–20 mg) who underwent ≥1 postbaseline weight assessment by week 12 were included.

Outcomes: The primary outcome was percent change in body weight at week 12. Secondary outcomes were proportions of patients with ≥7% or ≥10% weight gain from baseline at week 12.

Results: Overall, 1063 patients from 3 studies conducted between June 2013 and December 2021 were analyzed. At week 12, OLZ/SAM treatment was associated with a lower least squares mean (LSM) percent change in body weight from baseline (3.68%) vs olanzapine (5.43%) (LSM [SE] difference=−1.75% [.41]; 95% CI, −2.55 to −0.94). Fewer patients treated with OLZ/SAM gained ≥7% (23.9% vs 34.6%; odds ratio [OR] = 0.58; 95% CI, 0.043–0.79) or ≥10% (13.7% vs 20.4%; OR = 0.60; 95% CI, 0.42–0.88) of their baseline body weight at week 12.

Conclusion: In this IPD meta-analysis, OLZ/SAM treatment was associated with less weight gain and reduced risk of reaching ≥7% or ≥10% gain in body weight versus olanzapine over 12 weeks.

J Clin Psychiatry 2025;86(1):24m15526

Author affiliations are listed at the end of this article.