Efficacy of brexpiprazole in patients with acute schizophrenia: Review of three randomized, double-blind, placebo-controlled studies

Brexpiprazole, a serotonin-dopamine activity modulator, is a partial agonist at 5-HT1A and dopamine D2 receptors, and antagonist at 5-HT2A and noradrenaline α1B and α2C receptors, all at similar potency. Efficacy of brexpiprazole was evaluated in patients with acutely exacerbated schizophrenia in three short-term, randomized, double-blind, placebo-controlled studies. In a Phase 2 study, patients were randomized to brexpiprazole 0.25mg (fixed dose), 1.0±0.5mg, 2.5±0.5mg, 5.0±1mg (flexible-dose ranges), placebo, or aripiprazole 15±5mg. In two Phase 3 studies, patients were randomized to fixed-dose brexpiprazole 0.25mg, 1mg, 2mg, or 4mg, or placebo. For this review, brexpiprazole 2mg and 4mg arms from the Phase 3 studies were combined. Primary efficacy endpoint was change in Positive and Negative Syndrome Scale (PANSS) total score from baseline at week 6; key secondary endpoint was change in Clinical Global Impression-Severity of illness (CGI-S) score at week 6. Primary outcome moderator analyses explored effects of sex, age, race, and illness duration. There were no statistically significant differences vs. placebo in the Phase 2 brexpiprazole and aripiprazole groups for primary and key secondary endpoints. Combined brexpiprazole 2mg (n=359) and 4mg (n=359) were superior to placebo (n=358) in change in PANSS total score (least square mean difference from placebo: -5.46, p=0.0004, and -6.69, p<0.0001, respectively) and CGI-S (-0.25, p=0.0035, and -0.38, p<0.0001, respectively). Changes from baseline in efficacy endpoints were minimal in the 0.25mg group, while the 1mg group exhibited suboptimal improvement. No relevant moderators were identified. Meta-analysis of the pivotal studies indicates brexpiprazole 2mg and 4mg are effective in treating acute schizophrenia.