s | 53 Scale-18(BPRS-18) at the baseline, 6 weeks, 6 months, and 12 months after the baseline. Changes of BPRS-18 scores across time were analyzed by repeated measure ANOVA. To identify which factor is related to additional improvement with longterm use of clozapine, subjects were classified into 2 groups; clozapine-responsive group and clozapine-resistant group. And logistic regression was performed for two groups. Results: The analysis revealed the significant improvements of BPRS-18 scores had continued until 6 month, but no significant change found at 12 month. The greatest change of BPRS-18 score was observed at 6 week. Clozapine responsive group(n=14) seemed to have later onset time of the disease, get longer years of education, take more doses of clozapine, and show worse conditions in BPRS-18 at baseline than clozapine resistant group did. However, no significant differences in characteristics were found in logistic regression. Conclusion: From the results above, some patients with chronic schizophrenia seem to benefit from maintaining clozapine over 6 months. Though no factors predictive of additional efficacy after 6 weeks of clozapine therapy were found, this work suggests it is worth maintaining clozapine over 6 months for some patients if there are no other probable options left in clinical setting. PM421 Efficacy and safety of brexpiprazole (OPC-34712) in acute schizophrenia: a pooled analysis of two pivotal studies Aleksandar Skuban MD1, John M. Kane MD2, John Ouyang PhD1, Catherine Weiss PhD1, Emmanuelle Weiller PsyD3, Christoph U. Correll MD2 1Otsuka Pharmaceutical Development & Commercialization, Inc., Princeton, NJ, USA 2The Zucker Hillside Hospital, Glen Oaks, NY, USA 3H. Lundbeck A/S, Valby, Denmark Abstract Background: Brexpiprazole is a serotonin-dopamine activity modulator that acts as a partial agonist at 5-HT1A and dopamine D2 receptors, and an antagonist at 5-HT2A and noradrenaline alpha1B/2C receptors, all at similar potencies. The efficacy, safety, and tolerability of brexpiprazole were evaluated in patients with acute schizophrenia, based on pooled data from two pivotal phase III studies (NCT01396421[1] and NCT01393613[2]). Methods: In two similarly designed studies, patients with acute schizophrenia were randomly assigned to fixed once-daily doses of brexpiprazole 2mg, 4mg or placebo (an additional treatment group was included in each study [0.25mg and 1.0mg] to evaluate the lower dose range; these doses were not included in the meta-analysis). Primary efficacy endpoint was change in PANSS total score from baseline to week 6; key secondary endpoint was the change in CGI-S score at week 6. Results: Pooled brexpiprazole 4mg (N=359) and 2mg (N=359) were each superior to placebo (N=358) in change from baseline in PANSS total score at week 6 (least square mean difference [LSMD] to placebo: -6.69, p<0.0001 and -5.46, p=0.0004, respectively). Results of the key secondary endpoint supported the primary results. Altogether 8.2% (30/364) and 7.1% (26/368) of brexpiprazoletreated patients (4mg and 2mg, respectively) vs 14.7% (54/368) placebo-treated patients discontinued due to adverse events. The incidences of insomnia and agitation in the brexpiprazole treatment groups were similar or lower than with placebo. Akathisia incidences were 6.9% and 4.6% in the brexpiprazole 4mg and 2mg groups, respectively, vs 4.6% with placebo and sedation incidences were 2.7% and 1.6% in the brexpiprazole 4mg and 2mg groups, respectively, vs 0.8% with placebo. Conclusion: Pooled data from two pivotal studies provide evidence that brexpiprazole is efficacious and safe in treating patients with acute schizophrenia. Both brexpiprazole 2 and 4mg were well tolerated, with notably low levels of akathisia and sedation.Background: Brexpiprazole is a serotonin-dopamine activity modulator that acts as a partial agonist at 5-HT1A and dopamine D2 receptors, and an antagonist at 5-HT2A and noradrenaline alpha1B/2C receptors, all at similar potencies. The efficacy, safety, and tolerability of brexpiprazole were evaluated in patients with acute schizophrenia, based on pooled data from two pivotal phase III studies (NCT01396421[1] and NCT01393613[2]). Methods: In two similarly designed studies, patients with acute schizophrenia were randomly assigned to fixed once-daily doses of brexpiprazole 2mg, 4mg or placebo (an additional treatment group was included in each study [0.25mg and 1.0mg] to evaluate the lower dose range; these doses were not included in the meta-analysis). Primary efficacy endpoint was change in PANSS total score from baseline to week 6; key secondary endpoint was the change in CGI-S score at week 6. Results: Pooled brexpiprazole 4mg (N=359) and 2mg (N=359) were each superior to placebo (N=358) in change from baseline in PANSS total score at week 6 (least square mean difference [LSMD] to placebo: -6.69, p<0.0001 and -5.46, p=0.0004, respectively). Results of the key secondary endpoint supported the primary results. Altogether 8.2% (30/364) and 7.1% (26/368) of brexpiprazoletreated patients (4mg and 2mg, respectively) vs 14.7% (54/368) placebo-treated patients discontinued due to adverse events. The incidences of insomnia and agitation in the brexpiprazole treatment groups were similar or lower than with placebo. Akathisia incidences were 6.9% and 4.6% in the brexpiprazole 4mg and 2mg groups, respectively, vs 4.6% with placebo and sedation incidences were 2.7% and 1.6% in the brexpiprazole 4mg and 2mg groups, respectively, vs 0.8% with placebo. Conclusion: Pooled data from two pivotal studies provide evidence that brexpiprazole is efficacious and safe in treating patients with acute schizophrenia. Both brexpiprazole 2 and 4mg were well tolerated, with notably low levels of akathisia and sedation.