Neuropsychological endpoints for clinical trials in methylmalonic acidemia and propionic acidemia: A pilot study.

Introduction: This pilot study assessed instruments measuring relatively discrete neuropsychological domains to inform the selection of clinical outcome assessments that may be considered for interventional trials in methylmalonic acidemia (MMA) and propionic acidemia (PA). Methods: Tests and questionnaires were selected for their possible relevance to MMA and PA and potential sensitivity to modest changes in functioning and behavior. Results: Twenty-one patients (<18 years, Conclusion: Overall, test and questionnaire results were notably different between participants with MMA and participants with PA. The study demonstrates that pilot studies can detect instruments that may not be appropriate for individuals with language or motor deficits and that may not provide a broad range of scores reflecting disease severity. It also provides a rationale for focusing on discrete neuropsychological domains since some aspects of functioning were less affected than others and some were more closely related to disease severity. When global measures are used, overall scores may mask specific deficits. A pilot study like this one cannot ensure that scores will change over time in response to a specific treatment in a clinical trial. However, it can avert the selection of instruments that do not show associations with severity or biomedical parameters likely to be the target of a clinical trial. A pilot study can also identify when differences in diagnoses and baseline functioning need to be addressed prior to developing the analytical plan for the trial.