A Double-Blind, Placebo-Controlled, Phase II Study to Determine the Efficacy, Safety, Tolerability and Pharmacokinetics of a Controlled Release (CR) Formulation of Mazindol in Adults with DSM-5 Attention-Deficit/Hyperactivity Disorder (ADHD)

Background Mazindol is under investigation for the treatment of attention-deficit/hyperactivity disorder (ADHD) because of its alertness-enhancing properties. A novel controlled-release (CR) formulation of mazindol was developed to allow once-daily dosing. Objective The aim of this study was to evaluate the efficacy of mazindol CR in adults with ADHD. Design We conducted a randomized, double-blind, placebo-controlled 6-week trial. Methods Subjects diagnosed with ADHD using the Mini-International Neuropsychiatric Structured Interview (MINI) and with an ADHD Rating Scale, Diagnostic and Statistical Manual of Mental Disorders 5th Edition (ADHD-RS-DSM5) score >= 28 were randomized to receive placebo or 1-3 mg/day of mazindol for 6 weeks. The primary endpoint was the reduction from baseline in the ADHD-RS-DSM5 score on Day 42. Secondary endpoints were response rates defined by change in ADHD-RS-DSM5 (>= 30 or >= 50% reduction) and dichotomized Clinical Global Impression-Improvement (CGI-I) score (1 or 2). An exploratory endpoint of functional impairment, as measured by the Target Impairment Scale, examined individualized deficits in specific settings. Safety, tolerability, and pharmacokinetics were assessed. Statistical Eighty-five participants were randomized (n = 43 active, 42 placebo); 75 completed. Weekly ADHD-RS-DSM5 measurements after mazindol differed from placebo beginning at Day 7, with a least squares mean difference (active-placebo) of - 13.2 at Day 42 and an effect size of 1.09. For the 30% or more reduction in ADHD-RS-DSM5 (minimal response), a significant difference (active-placebo) was seen starting at Day 7 and continuing to Day 42. For the CGI-I (1 or 2) and for the 50% or more reduction in ADHD-RS-DSM5 (measures of excellent response), the differences began at Day 14 and continued to Day 42. Functional impairment was significantly different in the proportion achieving at least a 50% reduction in target impairment score (42.9% mazindol vs 11.9% placebo) by Day 42. Dry mouth, nausea, fatigue, heart rate (HR) increased, decreased appetite, and constipation were more prevalent for mazindol versus placebo. Overall, mazindol CR had minimal effects on blood pressure and small effects on HR. Conclusion Mazindol CR was efficacious in the treatment of adults with ADHD, with a large effect size, and was well tolerated, supporting the progression to phase III.