Background: ALKS 3831, a combination of olanzapine and samidorphan (OLZ/SAM), is in development for the treatment of schizophrenia and is intended to provide the antipsychotic efficacy of olanzapine while mitigating olanzapine-associated weight gain. We report the safety, tolerability, and efficacy of OLZ/SAM in patients with schizophrenia in a phase 3, 52-week, open-label extension study.

Patients aged 18–70 years who completed a previous phase 3, 4-week, inpatient acute efficacy study were switched from OLZ/SAM, olanzapine, or placebo to OLZ/SAM. Study assessments included adverse events (AEs), weight, clinical laboratory testing, and Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression-Severity (CGI-S) scores.

281 patients were enrolled; 277 (mean age, 41.4 years) received ≥1 dose of study drug, and 183 (66.1%) completed the extension study. The most common reasons for discontinuation were withdrawal by patient (15.5%), loss to follow-up (6.9%), and AEs (5.8%). AEs were reported in 136 (49.1%) patients; most were mild in severity. The most common AEs were increased weight (13.4%), somnolence (8.3%), nasopharyngitis (4.0%), and headache (4.0%). Mean weight increase from baseline in patients completing 52 weeks of treatment was 1.86 kg, a 2.79% increase. No clinically significant changes in mean laboratory parameters were observed. Mean (SD) changes from baseline to week 52 in PANSS total score and CGI-S score were –16.2 (15.41) and –0.9 (0.92), respectively (both P<0.001).

OLZ/SAM was generally well tolerated with a safety profile that supports long-term treatment. During this 52-week extension study, there were improvements in schizophrenia symptoms.

This study was funded by Alkermes, Inc.