Efficacy and Safety of a Combination of Olanzapine and Samidorphan in Adult Patients With an Acute Exacerbation of Schizophrenia: Outcomes From the Randomized, Phase 3 ENLIGHTEN-1 Study

Objective: To assess the antipsychotic efficacy and safety of a combination of olanzapine and samidorphan (OLZ/SAM). Methods: This 4-week, phase 3, randomized, double-blind, placeboand olanzapine-controlled study was conducted from December 2015 to June 2017 in adults with schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria who were experiencing an acute exacerbation. Patients were randomized 1:1:1 to OLZ/SAM, olanzapine monotherapy, or placebo. The primary and key secondary efficacy endpoint assessed was the change in Positive and Negative Syndrome Scale (PANSS) total score and Clinical Global Impressions-Severity of Illness Scale (CGI-S) score between baseline and week 4, respectively, for OLZ/SAM versus placebo. Safety monitoring occurred throughout. Results: 401 patients received >= 1 dose of study drug; 352 completed treatment. Treatment with OLZ/SAM resulted in significant improvements versus placebo in PANSS total and CGI-S scores from baseline to week 4 (least squares [LS] mean +/- SE: -6.4 +/- 1.8 [P < .001] and -0.38 +/- 0.12 [P =.002], respectively). Olanzapine treatment resulted in similar improvements (PANSS and CGI-S LS mean +/- SE of -5.3 +/- 1.84 [P= .004] and -0.44 +/- 0.12 [P < .001], respectively). Adverse events (AEs) occurred in 54.5%, 54.9%, and 44.8% of patients on OLZ/SAM, olanzapine, and placebo, respectively. Weight gain, somnolence, dry mouth, anxiety, and headache were the most common AEs (ie, >= 5%) with active treatment. Conclusions: OLZ/SAM treatment resulted in statistically and clinically significant efficacy improvements over 4 weeks versus placebo in adults with acutely exacerbated schizophrenia. Improvements were similar to those observed with olanzapine. OLZ/SAM was well tolerated, with a safety profile similar to that of olanzapine.