Iloperidone for schizophrenia: a review of the efficacy and safety profile for this newly commercialised second-generation antipsychotic

Summary Objective: The aim of the study was to describe the efficacy and safety of iloperidone for the treatment of schizophrenia. Data sources: The pivotal registration trials were accessed by querying http://www.pubmed.gov, http://www.fda.gov and http://www.clinicaltrials.gov for the search term ‘iloperidone’. Study selection: Four published primary reports of phase III studies were identified as well as preclinical animal and receptor affinity studies that describe potential mechanisms of action and pharmacogenomic studies that identify potential genetic biomarkers for efficacy and tolerability. Product labelling provided additional data. Data extraction: Descriptions of the principal results and calculation of number needed to treat (NNT) and number needed to harm (NNH) for relevant dichotomous outcomes were extracted from the study reports. Additional safety outcomes subject to NNH analysis were obtained from product labelling. Data synthesis: Iloperidone is a second-generation antipsychotic agent indicated for the acute treatment of schizophrenia in adults. Iloperidone has been evaluated in several double-blind placebo-controlled clinical trials. The oral formulation has demonstrated efficacy in reducing the symptoms of acute schizophrenia at fixed daily doses ranging from 12 to 24 mg. Data reported for categorical definitions of response using the Positive and Negative Syndrome Scale were limited to one study and specifically to rates of achieving a ≥ 20% decrease in the positive subscale from baseline; significantly more patients receiving iloperidone 24 mg/day (72%) than placebo (52%) met this criterion, yielding a NNT of five. Iloperidone should be titrated slowly to avoid orthostatic hypotension, potentially delaying the achievement of a therapeutic dose level. There appears to be a dose relationship for adverse events such as dizziness, somnolence and dry mouth; for example NNH vs. placebo for somnolence was 25 for iloperidone 10–16 mg/day and 10 for 20–24 mg/day. There is a possibility of a therapeutic dose response as well. Iloperidone is essentially free of extra-pyramidal side effects. Iloperidone is associated with weight gain comparable with risperidone. Long-term double-blind maintenance studies have demonstrated iloperidone’s non-inferiority to haloperidol for relapse prevention. Product labelling includes a warning about the potential for QT interval prolongation. At present there are no efficacy studies available that are powered to directly compare iloperidone with other second-generation antipsychotics. The development of a depot formulation of iloperidone as well as efforts to identify genetic biomarkers for prediction of both efficacy and tolerability are in progress. Conclusions: Aside from paliperidone, iloperidone is the first new second-generation antipsychotic to be commercialised in the USA since 2002. From the limited registration data, iloperidone appears to be relatively well tolerated once titrated to a therapeutic level and can be a useful option to consider. The development of a depot formulation and potential for genetic biomarkers may make this agent compelling. Further comparisons with other available agents among patients with schizophrenia in the ‘real world’ are needed.