Efficacy and Safety of High-Dose Multimatrix Mesalazine in Pediatric Patients with Mild-to-Moderate Active Ulcerative Colitis.

Purpose: This study aimed to investigate the efficacy and safety of high-dose multimatrix mesalazine in pediatric patients with active ulcerative colitis (UC). Methods: This was an open-label, uncontrolled, multicenter trial in Japan that included 27 patients aged <17 years with mild-to-moderate active UC. The participants were treated with multimatrix mesalazine at a dose of 80 mg/kg orally once daily for 8 weeks. The primary efficacy endpoint was the achievement of clinical remission, measured based on the ulcerative colitis disease activity index (UC-DAI) score. Results: In the full analysis set, the clinical remission rate based on the UC-DAI score at the end of treatment was 25.9% (two-sided 95% confidence interval [CI]: 11.1%, 46.3%; n=7/27). The lower limit of the two-sided 95% CI exceeded the efficacy threshold (10%), which was predefined based on the placebo group results from clinical studies involving patients with UC. The incidence of adverse events (AEs) was 66.7% (n=18/27) and that of drug-related AEs was 18.5% (n=5/27). No fatalities were reported. Among the study drug-related AEs, only drug intolerance (n=2) was classified as severe, serious, or led to study drug discontinuation. Conclusion: This study demonstrates the clinically meaningful efficacy of high-dose multimatrix mesalazine in the treatment of mild-to-moderate active pediatric UC in Japan. No noteworthy safety concerns beyond the known risks associated with mesalazine were noted.