Analysis and reporting of pediatric growth and development assessment from clinical trials: overview and challenges.

Pediatric drug development has many unique challenges, one of which is the evaluation of growth and development changes in children that are expected and are not due to the study intervention. Children grow and mature at different pace. The potential impact of the drug could vary with the developmental age of the participants receiving the treatment. For example, sexual maturation is a critical consideration in children of age 10 and above, but not in younger age groups. How the investigational drug impacts children is ultimately a risk-benefit consideration. In this paper, practical considerations and recommendations are provided on how to assess growth and development based on data collected from clinical trials in pediatric patients. The endpoints and measures related to growth, sexual maturation and neurocognitive development are discussed. Basic analysis approaches are recommended.

Statistical power considerations in the use of win ratio in cardiovascular outcome trials.

BACKGROUND: In cardiovascular outcome trials, the win ratio (WR) method models the composite endpoint under a hierarchical structure to account for clinical priorities. It also can be applied to both survival and nonsurvival outcomes. METHODS: In this article, we assess the performance of the WR method via extensive simulation studies and real data analyses and discuss power considerations of the method with respect to hierarchical order, variable type, magnitude of treatment effect, and event rates when applied to clinical studies. RESULTS AND CONCLUSION: In the hierarchy of the WR method, the first-ordered component (e.g., death) plays a dominant role in statistical power, especially when that component has a large treatment effect and a high event rate. This is in contrast with the score test of the Cox proportional hazards model in which the power is more likely affected by the nonfatal events that are usually observed earlier. Furthermore, when adding an additional component to the composite endpoint, the performance of the WR method varies depending on the treatment effect, event rate, and hierarchical position of the component. If the additional component has a relatively smaller or no treatment effect, the statistical power will decrease; if the additional component has a relatively larger treatment effect and higher event rate, the statistical power will increase. When adding a nonsurvival continuous outcome (e.g., 6-min walk distance) with even a tiny treatment effect, the statistical power could dramatically increase.

Mixture-based gatekeeping procedures in adaptive clinical trials.

Clinical trials with data-driven decision rules often pursue multiple clinical objectives such as the evaluation of several endpoints or several doses of an experimental treatment. These complex analysis strategies give rise to "multivariate" multiplicity problems with several components or sources of multiplicity. A general framework for defining gatekeeping procedures in clinical trials with adaptive multistage designs is proposed in this paper. The mixture method is applied to build a gatekeeping procedure at each stage and inferences at each decision point (interim or final analysis) are performed using the combination function approach. An advantage of utilizing the mixture method is that it enables powerful gatekeeping procedures applicable to a broad class of settings with complex logical relationships among the hypotheses of interest. Further, the combination function approach supports flexible data-driven decisions such as a decision to increase the sample size or remove a treatment arm. The paper concludes with a clinical trial example that illustrates the methodology by applying it to develop an adaptive two-stage design with a mixture-based gatekeeping procedure.

An enhanced mixture method for constructing gatekeeping procedures in clinical trials.

It is increasingly common to encounter complex multiplicity problems with several multiplicity components in confirmatory Phase III clinical trials. These components are often based on several endpoints (primary and secondary endpoints) and several dose-control comparisons. When constructing a multiplicity adjustment in these settings, it is important to control the Type I error rate over all multiplicity components. An important class of multiple testing procedures, known as gatekeeping procedures, was derived using the mixture method that enables clinical trial sponsors to set up efficient multiplicity adjustments that account for clinically relevant logical relationships among the hypotheses of interest. An enhanced version of this mixture method is introduced in this paper to construct more powerful gatekeeping procedures for a specific type of logical relationships that rely on transitive serial restrictions. Restrictions of this kind are very common in Phase III clinical trials and the proposed method is applicable to a broad class of multiplicity problems. Several examples are provided to illustrate the new method and results of simulation trials are presented to compare the performance of gatekeeping procedures derived using this method and other available methods.

Summary of findings from the FDA regulatory science forum on measuring sexual dysfunction in depression trials.

OBJECTIVE: Sexual dysfunction is a significant treatment-emergent adverse reaction to the serotonergic antidepressants (selective serotonin reuptake inhibitors [SSRIs] and serotonin-norepinephrine reuptake inhibitors [SNRIs]). However, the rate of sexual dysfunction is often underestimated in registration trials, which have relied on unsolicited reports. We conducted a literature search to examine the rates of sexual dysfunction with SSRIs/SNRIs when these rates were ascertained by structured questionnaires or standardized instruments. Additionally, we conducted exploratory analyses of major depressive disorder (MDD) registration trial data. DATA SOURCES: For the literature search, we used the PubMed and EMBASE databases, with a cutoff date of April 1, 2011. We included all the SSRIs and SNRIs that at the time had been approved for the treatment of MDD. For each of these drugs, a search was conducted with the following terms: sexual dysfunction, SD, sexual adverse effects, desire, arousal, excitement, and orgasm. For the exploratory analyses of US Food and Drug Administration in-house trial data, we searched our database for short-term (6-8 weeks), randomized, placebo-controlled MDD monotherapy trials of approved drugs included in New Drug Application submissions that used a standardized instrument to assess sexual function. STUDY SELECTION: For the literature search, we initially found a total of 123 nonduplicate articles, some of which included multiple studies. After screening based on our inclusion/exclusion criteria (and to remove duplicate trial-level data), we were left with 7 articles representing 11 unique studies in which sexual dysfunction was assessed with direct questioning or standardized instruments. The Changes in Sexual Functioning Questionnaire-Short-Form (CSFQ-14) and Arizona Sexual Experiences Scale (ASEX) were the only instruments represented. For the exploratory analyses of in-house MDD trial data, we found controlled studies using either the CSFQ-14 (6 trials) or ASEX (5 trials). DATA EXTRACTION: For the literature search, we were able to pool the results for the studies that included direct questioning. For the studies that used standardized instruments to assess sexual function, we simply describe our findings. For the exploratory analyses of in-house MDD trial data, we constructed a dataset containing all subject-level CSFQ-14 or ASEX item scores for each of the trials as well as demographic and other relevant variables. For each treatment or placebo group, analyses were performed on pooled data, including multiple studies, and on individual studies. RESULTS: For our literature search, regardless of which method was used to assess sexual function, the data from these articles were informative and showed the expected effects on sexual function with SSRIs/SNRIs. However, for our exploratory analyses, no trend was observed in CSFQ-14 or ASEX results for individual drugs or drug classes. CONCLUSIONS: These results raise the question as to why the CSFQ-14 and ASEX appeared to perform well in the published studies but not in our exploratory analyses of in-house MDD trial data. We discuss possible reasons and solutions.

Regulatory and scientific issues in studies to evaluate sexual dysfunction in antidepressant drug trials.

OBJECTIVE: Sexual dysfunction is an important side effect of serotonergic antidepressants, as it often leads to treatment nonadherence. However, sexual dysfunction is often underestimated in clinical trials submitted in support of drug approval. This is because such assessments are based mainly on unsolicited reporting. As a result, the characterization of sexual adverse events has become an important component of many of the development programs for new antidepressants. The purpose of this article is to discuss US Food and Drug Administration's (FDA's) current thinking on possible approaches to characterizing the effects of drugs on sexual function in depression drug trials. PARTICIPANTS: FDA's Division of Psychiatry Products, together with the Division of Biometrics I, in particular the authors of this article. EVIDENCE: The above-referenced FDA divisions conducted a regulatory science forum on measuring sexual dysfunction in depression trials. CONSENSUS PROCESS: Considering the evidence presented and discussed at the forum, we developed our preliminary regulatory views on the scientific issues with regard to study design, study population, use of available scales, testing strategy, and statistical analysis plans. CONCLUSIONS: Sexual dysfunction associated with antidepressants is an important entity that should be adequately assessed during clinical trials with the use of available instruments and described in product labels. It is important to appreciate the need for a positive control to establish assay sensitivity for any trial evaluating the impact of antidepressant medications on sexual function. Methodological improvement and additional data as well as experience with these approaches will be needed prior to further consideration of a formal regulatory guidance document by the FDA.