Safety and Tolerability of Serdexmethylphenidate/Dexmethylphenidate Capsules in Children with Attention-Deficit/Hyperactivity Disorder: A 12-Month, Open-Label Safety Study

Objective: Serdexmethylphenidate/dexmethylphenidate (SDX/d-MPH) is approved for the treatment of patients aged >= 6 years with attention-deficit/hyperactivity disorder (ADHD). A pivotal double-blind (DB) study of children aged 6-12 years with ADHD demonstrated efficacy for ADHD with good tolerability. In this study, we assessed the safety and tolerability of daily oral SDX/d-MPH for up to 1 year in children with ADHD. Methods: This was a dose-optimized, open-label safety study with SDX/d-MPH in children aged 6-12 years with ADHD that included subjects who successfully completed the DB study (rollover) and new subjects. The study consisted of a 30-day screening phase, a dose optimization phase for new subjects only, a 360-day treatment phase, and follow-up. Adverse events (AEs) were assessed from the first day of SDX/d-MPH administration to the end of the study. During the treatment phase, ADHD Rating Scale-5 (ADHD-RS-5) and Clinical Global Impressions-Severity (CGI-S) scale assessments were used to evaluate ADHD severity. Results: Of the 282 subjects enrolled (70 rollover; 212 new), 28 discontinued treatment in the dose optimization phase and 254 entered the treatment phase. By study completion, 127 had discontinued and 155 had completed the study. The treatment-phase safety population included all enrolled subjects who received >= 1 dose of study drug and had >= 1 postdose safety assessment. Of 238 subjects assessed in the treatment-phase safety population, 143 (60.1%) had >= 1 treatment-emergent adverse events (TEAEs), and 36 (15.1%), 95 (39.9%), and 12 (5.0%) had mild, moderate, or severe TEAEs, respectively. The most common TEAEs were decreased appetite (18.5%), upper respiratory tract infection (9.7%), nasopharyngitis (8.0%), decreased weight (7.6%), and irritability (6.7%). There were no clinically meaningful trends in electrocardiograms, cardiac events, or blood pressure events, and none led to discontinuation. Two subjects had eight serious AEs that were unrelated to treatment. There were overall reductions in ADHD symptoms and severity as assessed by ADHD-RS-5 and CGI-S during the treatment phase. Conclusions: In this 1-year study, SDX/d-MPH was found to be safe and well tolerated and comparable with other methylphenidate products, with no unexpected safety findings. SDX/d-MPH also showed sustained efficacy during the 1-year treatment period. ClinicalTrials.gov identifier: NCT03460652.