Phase 3, multicentre, randomised, double-blind, placebo-controlled, parallel-group study of ustekinumab in Japanese patients with active polymyositis and dermatomyositis who have not adequately responded to one or more standard-of-care treatments.

objectivesTo evaluate the efficacy and safety of ustekinumab (UST) in a multicentre, randomised, double-blind, placebo-controlled trial in adult Japanese patients with active polymyositis (PM) and dermatomyositis (DM).

methodsFifty-one Japanese adults diagnosed with active PM/DM who did not respond adequately to one or more standard-of-care treatments were randomised 1:1 to receive UST (n=25) or placebo (n=26). Participants received body weight-range based intravenous administration of UST (6 mg/kg) or placebo at week 0 followed by 90 mg subcutaneous (SC) administration of UST or placebo every 8 weeks from week 8 to week 24. At week 24, placebo group crossed over to receive body weight-range based intravenous administration of UST, and thereafter, all participants received/were to receive SC administration of UST 90 mg every 8 weeks (week 32 through to week 72). The primary efficacy endpoint was the proportion of participants who achieved minimal improvement (≥20) in the International Myositis Assessment and Clinical Studies Total Improvement Score (IMACS TIS) at week 24.

resultsNo statistically significant difference was seen in the proportion of participants who achieved minimal improvement (≥20) in IMACS TIS at week 24 between the treatment groups (UST 64.0% vs placebo 61.5%, p=0.94) based on the primary estimand of the primary endpoint analysis.

conclusionsUST was safe and well tolerated but did not meet the primary efficacy endpoint in adult Japanese participants with active PM/DM based on the primary analysis at week 24 in the study. TRIAL REGISTRATION NUMBER: NCT03981744.