A Multicentre, Double-Blind, Placebo-Controlled, Parallel-Group Study to Evaluate the Efficacy, Safety, and Tolerability of the S1P Receptor Agonist KRP203 in Patients with Moderately Active Refractory Ulcerative Colitis

Background and Aims: KRP203 is a potent oral agonist of the sphingosine-1-phosphate receptor subtype 1 that induces the sequestration of peripheral lymphocytes, thereby potentially reducing the number of activated lymphocytes circulating to the gastrointestinal tract. Methods: We conducted a multicentre, double-blind, placebo-controlled, parallel-group, proof-of-concept study to evaluate the efficacy, safety, and tolerability of KRP203 in patients with moderately active 5-aminosalicylate-refractory ulcerative colitis (UC). Patients were randomly assigned to receive 1.2 mg KRP203 or placebo daily for 8 weeks. Primary efficacy variable was clinical remission, defined as partial Mayo Score 0–1 and modified Baron Score 0–1 with rectal bleeding subscore 0. Results: KRP203 was safe and well tolerated overall. The most common adverse events (AEs) were gastrointestinal disorders and headache. Importantly, no KRP203-related cardiac AEs were reported. Total peripheral lymphocytes and selectively affected lymphocyte subtypes decreased, causing marked decreases in naive and central memory CD4+ and CD8+ T cells, and also in B cells. Clinical remission occurred in 2/14 (14%) patients under KRP203, compared with 0/8 (0%) under placebo. Conclusions: Overall, KRP203 was safe and well tolerated by patients with UC. Importantly, no cardiac AEs were reported. Although KRP203 did not meet the minimum clinically relevant threshold for efficacy, the results may suggest that KRP203 treatment is superior to placebo. However, in this small study population, the difference was insignificant. Based on these data, studies with an improved design and a larger population should be considered.