Asenapine versus olanzapine in people with persistent negative symptoms of schizophrenia

Two randomized, double-blind, 26-week core studies (Eastern [EH] and Western Hemisphere [WH]) tested the hypothesis that asenapine is superior to olanzapine for persistent negative symptoms of schizophrenia; 26-week extension studies assessed the comparative long-term efficacy and safety of these agents. In the core studies, 949 people were randomized to asenapine (n = 241 and 244) or olanzapine (n = 240 and 224); 26-week completion rates with asenapine were 64.7% and 49.6% (olanzapine, 80.4% and 63.8%) in the EH and WH, respectively. In the EH and WH extensions, respectively (asenapine, n = 134 and 86; olanzapine, n = 172 and 110), 52-week completion rates were 84.3% and 66.3% with asenapine (olanzapine, 89.0% and 80.9%). Asenapine was not superior to olanzapine in change in the 16-item Negative Symptom Assessment Scale total score in either core study, but asenapine was superior to olanzapine at week 52 in the WH extension study. Olanzapine was associated with modest, but significantly greater, changes in PANSS positive subscale score at various assessment times in both core studies and the WH extension study. Incidence of treatment-emergent adverse events was comparable between treatments across studies. Weight gain was consistently lower with asenapine. Extrapyramidal symptom-related adverse event incidence was higher with asenapine (EH: 8.3%; 95% confidence interval [CI], 5.1%-12.5%; WH: 16.4%; 95% CI, 11.9%-21.6%) than olanzapine (EH: 3.3%; 95% CI, 1.4%-6.4%; WH: 12.1%; 95% CI, 8.1%-17.0%), but Extrapyramidal Symptom Rating Scale-Abbreviated total score changes did not significantly differ between treatments. In conclusion, asenapine superiority over olanzapine was not observed in the core studies. Both treatments improved persistent negative symptoms, but discontinuation rates were higher with asenapine.