Efficacy of iloperidone in the short-term treatment of schizophrenia: a post hoc analysis of pooled patient data from four phase III, placebo- and active-controlled trials

Abstract

Objectives: The efficacy and tolerability characteristics of an antipsychotic are difficult to determine from a single registration study. We thus conducted an analysis that assessed key efficacy and tolerability outcomes post hoc from four pooled short-term (4-6 weeks) phase III studies that evaluated iloperidone versus placebo in patients with schizophrenia or schizoaffective disorder.

Methods: Patient-level data were pooled from four prospective, randomized, double-blind, placebo-controlled and active-controlled, multicenter trials of iloperidone in patients with schizophrenia or schizoaffective disorder aged 18-65 years. Iloperidone 4-8, 10-16, and 20-24 mg/day (all dosed twice daily) were compared with placebo. Active controls used for assay sensitivity included risperidone 4-8 mg/day, haloperidol 15 mg/day, and ziprasidone 160 mg/day. Outcomes of interest were change from baseline to endpoint in the Brief Psychiatric Rating Scale (derived) (BPRSd), Positive and Negative Syndrome Scale (PANSS)-total (PANSS-T) score, and PANSS-positive (PANSS-P) and PANSS-negative (PANSS-N) subscale scores. An analysis of covariance (with treatment and study as factors, baseline as a covariate) was performed to compare changes between the iloperidone treatment groups versus placebo, on the basis of a last-observation-carried-forward approach for the intent-to-treat (ITT) populations. Tolerability outcomes were obtained from spontaneously reported adverse events (AEs), and number needed to harm was calculated for each antipsychotic versus placebo for the total population.

Results: The ITT population included both schizoaffective and schizophrenia patients (N = 2401): n = 370, n = 494, and n = 424 for iloperidone 4-8, 10-16, and 20-24 mg/day, respectively; n = 294 for risperidone; n = 114 for haloperidol; n = 144 for ziprasidone; and n = 561 for placebo. Treatment with iloperidone 10-16 mg/day or 20-24 mg/day was associated with significantly improved BPRSd, PANSS-T, PANSS-P, and PANSS-N scores versus treatment with placebo. When only patients with schizophrenia were included (n = 1941), the pattern of results was essentially unchanged. The active controls confirmed assay sensitivity. Across all iloperidone dose groups, the incidences of extrapyramidal disorders and akathisia were similar to those observed with placebo. AEs for which the frequency was greater for iloperidone than placebo and for which the 95% confidence interval for number needed to harm did not contain infinity were dizziness, dry mouth, somnolence, nasal congestion, fatigue, sedation, and tachycardia; in general, for these AEs, frequency was higher with higher doses, resulting in a lower number needed to harm.

Conclusions: Consistent with product labeling, iloperidone 10-16 mg/day or 20-24 mg/day demonstrated significant improvement over placebo on BPRSd and PANSS-T scores, as well as on PANSS-P and PANSS-N subscale scores over 6 weeks of treatment in patients with schizophrenia and in the ITT population, which includes patients with schizoaffective disorder. Iloperidone did not differ from placebo in terms of extrapyramidal disorders and akathisia.