Exploratory Analyses of Efficacy Data From Schizophrenia Trials in Support of New Drug Applications Submitted to the US Food and Drug Administration
ABSTRACT There has been concern about a high rate of placebo response and a decline in treatment effect over time in schizophrenia trials as well as the implications of increasing conduct of such trials outside North America. This report explores differences in efficacy data over an 18-year period from randomized placebo-controlled trials submitted in support of new drug applications (NDAs) for the treatment of schizophrenia and differences in results between trials conducted in North America and elsewhere.
Clinical trial data that were submitted to the US Food and Drug Administration (FDA) as part of NDAs for the indication of schizophrenia between 1991 and 2009.
Efficacy data were compiled from 32 clinical trials with 11,567 evaluable patients with schizophrenia. Data from completed, randomized, multicenter, double-blind, placebo-controlled, 4- to 8-week clinical trials in adult patients diagnosed with schizophrenia according to DSM-III or DSM-IV criteria were included.
Baseline demographic and disease characteristics, including mean Positive and Negative Syndrome Scale (PANSS) total scores, were summarized and compared between North American and multiregional trials. Mean change from baseline to endpoint in PANSS total scores was utilized as the primary outcome of interest. We explored differences in treatment effect and success rate of these trials based on when and where the studies were conducted, sample size, trial duration, and baseline patient characteristics.
Twenty-one of the 32 trials were conducted solely in North America, and 11 were carried out in multiple regions. Of those 11 multiregional trials, 2 were conducted exclusively in foreign countries. Although the observed responses (change from baseline) in placebo and drug-treated groups in multiregional trials tended to be larger than in North American trials, the treatment effects (drug-placebo difference) were -9 and -8 PANSS units for North American and multiregional trials, respectively. When time of trial conduct was taken into account, an increasing placebo response and a diminishing treatment effect over time were observed in North American trials from -10.8 PANSS units for the first period (1991-1998) to -6.0 PANSS units for the later period (1999-2008). The overall trial success rate over the almost 2 decades was 78%, declining slightly in trials conducted after 1999, the time period during which multiregional trials were first conducted (74% for 1999-2008 vs 85% for 1991-1998), despite increasing sample sizes in the later period. The mean baseline PANSS total score was in the range of 87-100 for most of these trials. Trials in patients with higher mean baseline PANSS total scores tended to show larger treatment effects than those in patients with lower scores. The mean body weight and body mass index (BMI) were higher in patients in North American trials and North America-predominant multiregional trials compared to those in foreign-predominant multiregional trials (mean body weights of 85 kg and 81 kg vs 72 kg, and BMIs of 29 and 27 vs 25, respectively). Treatment effects decreased as body weights increased, especially in North American trials. In foreign-predominant multiregional trials, there were higher proportions of women than in North American trials and North America-predominant multiregional trials (40% vs 22% and 27%, respectively) and a relatively larger proportion of Asians (21% vs 1% and 8%, respectively).
A high and increasing placebo response and a declining treatment effect are of great concern in schizophrenia trials conducted in North America. In this era of global clinical trials, close attention is needed to the design and conduct of these trials.
- SourceAvailable from: Tamar Dina Wohlfarth
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- "Similar differences were previously reported by Khin et al. (2012). However there are contradicting results regarding the impact of race on efficacy of pharmacological treatment of schizophrenia (Teo et al., 2013; Bersani et al., 2011; Bigos et al., 2011; Stauffer et al., 2010; Ciliberto et al., 2005). "
ABSTRACT: Generalizability of efficacy results from medication trials across geographic regions is disputed. Geographic differences in factors such as patient characteristics, treatment practices and disease definitions might lead to differences in effect sizes across regions. This study examined geographic variation in efficacy results of schizophrenia trials with atypical antipsychotics using individual-patient data meta-analysis. Twenty-two studies including in total 5,233 patients from three regions (North America, Europe, and the rest of the world) were included in the random effects meta-analysis. The effect size in North American patients was smaller in terms of mean change from baseline and in terms of responders (Hedge's G=0.37, 95% CI 0.28–0.46; OR 1.71, 95% CI 1.35–2.17) as compared to patients in Europe (Hedge's G=0.56, 95% CI 0.34–0.79; OR 2.25, 95% CI 1.62–3.12) and the rest of the world (Hedge's G=0.53, 95% CI 0.12–0.75; OR 2.61, 95% CI 1.66–4.17). The differences were not statistically significant. The observed differences remained when the confounding effect of unequal distribution of compounds was controlled for by analyzing separately the compounds that were studied across all three regions. Based on these results it cannot be excluded that there are differences in efficacy results of atypical antipsychotics trials across geographic regions. Thβe observed trend towards differential efficacy across geographic regions warrants further examination of the determinants of these differences.European neuropsychopharmacology: the journal of the European College of Neuropsychopharmacology 07/2014; 24(7). DOI:10.1016/j.euroneuro.2014.02.006 · 5.40 Impact Factor
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ABSTRACT: The objective of this paper was to investigate the prognostic and predictive value of a small panel of independent and clinically important factors based on symptom improvement, baseline cognitive impairment, and weight change during the early treatment phase. METHODS: The study sample was based on a double-blind, 6-month continuation study of ziprasidone and olanzapine (N=94). We developed a parsimonious 6-month GAF prediction function using a logistic regression model, and evaluated its predictive accuracy and performance using bootstrap estimates of c-statistics and error in predicted probability. RESULTS: At up to 6 months of follow-up, 52 (55%) of all subjects treated with ziprasidone or olanzapine met the responder criterion of ≥50% improvement in GAF. At Week 2 (acute phase), the majority of ziprasidone (75%) and olanzapine (70%) patients showed greater than 25% improvement in the BPRS psychotic symptom subscale score. These early psychotic symptom responders (Week 2) showed significantly greater improvement in global functioning than early non-responders at all time points (Week 6 and Month 6) (all p's<0.05), confirming early response as an indicator of continued responsiveness to treatment over at least 6 months. A multivariate prediction function based on baseline neurocognitive scores and GAF, early reduction of psychotic symptoms at 2 weeks, and percentage of weight change observed at 6 weeks (All p's <0.05), showed statistically acceptable predictive performance (boostrap c-statistics=0.8598). CONCLUSIONS: Our findings suggest that a parsimonious model incorporating a psychotic symptom assessment score, baseline neurocognitive performance, and risk of weight gain can be developed for predicting patients' likelihood of achieving favorable, long-term treatment outcomes.European neuropsychopharmacology: the journal of the European College of Neuropsychopharmacology 11/2012; 23(8). DOI:10.1016/j.euroneuro.2012.10.005 · 5.40 Impact Factor
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ABSTRACT: High and variable placebo effect (PE) within and among clinical trials can substantially affect conclusions about the efficacy of new drugs in the treatment of schizophrenia and other neuropsychiatric disorders. In recent years, it has become increasingly difficult to prove drug efficacy against placebo, and one of the reasons is that the placebo response has increased over recent years. The increased placebo response over the years is partly explained by unidentified parallel interventions, patient factors, issues with trial designs, and regional variability or demographic differences. In addition, a nocebo effect, which is undesirable effects a subject manifests after receiving placebo, e.g. extrapyramidal side effects, in placebo arms of antipsychotic trials could also influence the PE and clinical trial outcomes. Placebo effects (PEs) are a natural phenomenon and cannot be avoided completely in clinical trials. However, accounting for the PE via mixed effects modelling approaches could reduce bias in quantifying the overall effect size of the drug treatment. This review article focuses on the PE and its impact on schizophrenia clinical trial outcomes. The authors briefly describe the factors that lead to high and variable PE. Next, pharmacometric approaches to account for the PE and dropouts in schizophrenia clinical trials are described. Finally, some points are provided that could be considered while designing and optimizing antipsychotic trials via simulation approaches.Journal of Pharmacokinetics and Biopharmaceutics 01/2013; DOI:10.1007/s10928-012-9296-7 · 1.46 Impact Factor