Combination olanzapine and samidorphan (OLZ/SAM) is in development for treatment of schizophrenia and bipolar I disorder and is intended to provide the antipsychotic efficacy of olanzapine while mitigating olanzapine-associated weight gain. This 52-week open-label extension study (NCT02873208; ENLIGHTEN-2-EXT) in schizophrenia assessed the safety and tolerability of OLZ/SAM. Methods: Patients completing the 24-week, randomized, double-blind, phase 3 ENLIGHTEN−2 study comparing weight gain with OLZ/SAM vs olanzapine were eligible for ENLIGHTEN-2-EXT enrollment. Initial OLZ/SAM doses were based on olanzapine dose (10 or 20 mg) received at the conclusion of ENLIGHTEN-2; subsequent olanzapine dose adjustments were allowed. The samidorphan dose (10 mg) remained fixed throughout. Assessments included adverse events (AEs), weight, waist circumference, metabolic laboratory parameters, and Positive and Negative Syndrome Scale (PANSS) scores. Analyses were based on observed results using descriptive statistics. Baseline was relative to the first OLZ/SAM dose in the extension study.

265 patients received OLZ/SAM; 167 (63.0%) completed the extension study. Common AEs (= 5%) were weight decreased (n=23; 8.7%), extra dose administered (n=21; 7.9%), headache (n=18; 6.8%), and weight increased (n=16; 6.0%). At week 52, mean (SD) change from baseline for weight and waist circumference was −0.03 (6.216) kg and −0.35 (6.115) cm, respectively. Changes in fasting lipid and glycemic parameters were generally small and remained stable over 52 weeks. PANSS total scores remained stable during the extension.

OLZ/SAM was generally well tolerated over 52 weeks. Weight, waist circumference, metabolic laboratory parameters, and schizophrenia symptoms remained stable throughout the study.

Alkermes, Inc.

Opioid antagonists may mitigate medication-associated weight gain and/or metabolic dysregulation. ENLIGHTEN-2 evaluated a combination of olanzapine and the opioid antagonist samidorphan (OLZ/SAM) vs olanzapine for effects on weight gain and metabolic parameters over 24 weeks in adults with stable schizophrenia.

This phase 3, double-blind study (ClinicalTrials.gov: NCT02694328) enrolled adults 18–55 yo with stable schizophrenia, randomized 1:1 to once-daily OLZ/SAM or olanzapine. Co-primary endpoints were percent change from baseline in body weight and proportion of patients with ≥10% weight gain at week 24. Waist circumference and fasting metabolic parameters were also measured. Completers could enter a 52-week open-label safety extension.

561 patients were randomized: 550 were dosed, 538 had ≥1 post-baseline weight assessment, and 352 (64%) completed; 10.9% discontinued due to AEs. At week 24, least squares mean (SE) percent weight change from baseline was 4.21 (0.68)% with OLZ/SAM and 6.59 (0.67)% with olanzapine (difference, −2.38 [0.76]%; P=0.003). Fewer patients treated with OLZ/SAM (17.8%) had ≥10% weight gain vs olanzapine (29.8%; odds ratio=0.50; P=0.003). The change from baseline in waist circumference was significantly smaller with OLZ/SAM (P<0.001). Common AEs (≥10%) with OLZ/SAM and olanzapine were weight increased (24.8%, 36.2%), somnolence (21.2%, 18.1%), dry mouth (12.8%, 8.0%), and increased appetite (10.9%, 12.3%), respectively. Metabolic parameter changes were generally small and remained stable with long-term OLZ/SAM treatment.

OLZ/SAM treatment limited weight gain associated with olanzapine. Metabolic parameter changes were generally small, similar between groups over 24 weeks, and remained stable over an additional 52 weeks of open-label OLZ/SAM treatment.

This study was funded by Alkermes, Inc.