Long-Term Safety and Efficacy of Dazukibart in Dermatomyositis: Combined Phase II Results From Double-Blind and Open-Label Extension Studies

OBJECTIVE: To evaluate the long-term safety and efficacy of dazukibart, a novel antiinterferon β monoclonal antibody, in adults with moderate-to-severe dermatomyositis (DM). METHODS: Participants from 2 cohorts of DM (skin-predominant [SP] and muscle-predominant [MP]) completing a 24-week phase II, double-blind study, were enrolled into a 52-week phase IIb, open-label extension (OLE) study, with a 16-week follow-up post treatment (combined study duration: 92 weeks). The pooled skin analysis set included all SP and MP DM participants with baseline Cutaneous Dermatomyositis Disease Area and Severity Index-Activity (CDASI-A) scores ≥ 14. The primary endpoint was incidence of treatment-emergent adverse events (TEAEs) from week 24 through week 92. Key secondary endpoints were change in CDASI-A and Total Improvement Score (TIS) from week 0 through week 92. RESULTS: Participants who received ≥ 1 dose of dazukibart (600 mg) during the OLE study (comprising 9, 15, and 16 participants from the SP cohort, MP cohort, and pooled skin analysis set, respectively) were analyzed (median age 49.5 years, 83% female, 96% White). TEAEs were mild (55%), moderate (38%), or severe (7%), with no treatment-related serious AEs or treatment discontinuations. At week 76, CDASI-A scores improved, with a median change from baseline of -24.0 (range -33 to -12), -9.0 (range -32 to 1), and -23.5 (range -33 to -12) for participants from the SP cohort, MP cohort, and pooled skin analysis set, respectively. In the MP cohort, TIS (median 65.0, range 2.5-95.0) and associated core set measures, including patient-reported outcomes, improved at week 76. Overall, the observed improvements in outcomes, as indicated by the slight reduction in outcome measures, persisted during the 16-week posttreatment follow-up. CONCLUSION: The safety and efficacy profiles of dazukibart observed at 24 weeks were sustained through 92 weeks. (ClinicalTrials.gov: NCT03181893, NCT05192200).