In the per-protocol population , 8 weeks of treatment with bitopertin was associated with a significant reduction of negative symptoms in the 10-mg/d ( mean [ SE ] reduction in negative symptoms score , -25 % [ 2 % ] ; P = .049 ) and 30-mg/d ( mean [ SE ] , -25 % [ 2 % ] ; P = .03 ) bitopertin groups , a significantly higher response rate and a trend toward improved functioning in the 10-mg/d group when compared with placebo ( mean [ SE ] , -19 % [ 2 % ] ) .