A Phase 3, Multicenter, Randomized, Placebo-Controlled Trial Evaluating the Efficacy, Safety, and Tolerability of Serdexmethylphenidate/d-Methylphenidate Capsules in Chinese Children with Attention-Deficit/Hyperactivity Disorder

Background and Objective: Serdexmethylphenidate/dexmethylphenidate (SDX/d-MPH) is a novel methylphenidate formulation designed to provide rapid onset and sustained symptom control in attention-deficit/hyperactivity disorder (ADHD). This phase 3 study evaluated its efficacy, safety, and tolerability in Chinese children with ADHD. Methods: This multicenter, randomized, double-blind, placebo-controlled bridging study enrolled children aged 6–12 years who met DSM-5 criteria for ADHD. The primary endpoint was least squares mean (LSM) change from baseline to week 3 in ADHD Rating Scale-5 (ADHD-RS-5) total score, an 18-item DSM-5-based scale rating symptoms from 0 (never/rarely) to 3 (very often). Secondary endpoints included change from baseline to week 4 in ADHD-RS-5, and weekly changes in Clinical Global Impressions–Severity (CGI-S), Clinical Global Impressions–Improvement (CGI-I), and Weekly Ratings of Evening and Morning Behavior–Revised (WREMB-R). Safety was assessed throughout the study. Results: Overall, 55 participants were randomized (SDX/d-MPH, n = 28; placebo, n = 27). At week 3, SDX/d-MPH demonstrated significantly greater improvement in ADHD-RS-5 total score versus placebo (between-group LSM change [standard error]: − 5.8 [2.58], p = 0.0292), with an effect size of 0.61, meeting the prespecified efficacy consistency criterion (≥ 0.25). At week 4, significant improvements versus placebo were observed across ADHD-RS-5 total score (− 8.4 [2.69]), inattention and hyperactivity–impulsivity sub-scores (− 4.4 [1.69] and − 3.7 [1.27], respectively), CGI-S (− 0.8 [0.28]), CGI-I (0.9 [0.27]), and WREMB-R total (− 3.7 [1.35]) and evening scores (− 3.2 [1.03]). Most treatment-emergent adverse events were mild to moderate, with no new safety signals. Conclusions: SDX/d-MPH significantly improved ADHD symptoms and was generally well tolerated in Chinese children, supporting extension of global trial results to this population. ClinicalTrials.gov identifier: NCT06359899 (registered on 25 March 2024).