A Phase 3, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Pimavanserin as an Adjunctive Treatment for the Negative Symptoms of Schizophrenia (ADVANCE-2) in Patients With Predominant Negative Symptoms.

Background and hypotheses: Negative symptoms of schizophrenia (NSS) carry a substantial burden, and there are no treatments currently approved for NSS. The efficacy of pimavanserin, a selective 5-HT2A inverse agonist and antagonist, in treating NSS was assessed.

Study design: ADVANCE-2 was a phase 3, randomized, double-blind, placebo-controlled study of pimavanserin in patients with schizophrenia and predominantly negative symptoms. Patients were randomized (1:1) to receive pimavanserin (34 mg/day) or placebo alongside ongoing background antipsychotic medication. Eligible adults were aged 18-55 years and had access to a caregiver. The primary and key secondary endpoints were the change from baseline to week 26 in the Negative Symptom Assessment-16 (NSA-16) total score and Clinical Global Impression-Schizophrenia Scale-Severity (CGI-SCH-S) negative symptom score, respectively.

Study results: Of the 454 randomized patients, 71 (39 placebo; 32 pimavanserin) discontinued and 383 (188 placebo; 195 pimavanserin) completed the study. The safety and full analysis sets comprised 453 and 446 patients, respectively. The NSA-16 change from baseline to week 26 was not significantly different between groups (least squares mean difference: -0.67; SE, 0.95; [95% CI: -2.54, 1.20]; P = .48; Cohen's d effect size: 0.07). Treatment-emergent adverse events occurred in 30.4% with pimavanserin and 40.3% with placebo.

Conclusions: In this study, pimavanserin was well tolerated, and although it demonstrated a similar treatment effect as in the prior phase 2 study favoring pimavanserin, treatment with pimavanserin vs placebo did not result in significant differences for primary or other endpoints.