Efficacy and Safety of Rilzabrutinib in Pemphigus: PEGASUS Phase 3 Randomized Study

Trial design Pemphigus is a rare, but life-threatening autoimmune disease requiring long-term treatment that minimizes corticosteroid (CS) exposure while providing consistent disease control. The phase 2 pemphigus study of oral, reversible, covalent Bruton tyrosine kinase (BTK) inhibitor rilzabrutinib demonstrated rapid and sustained efficacy with well-tolerated safety. Methods Adults (18–80 y) were randomized 1:1 to rilzabrutinib 400 mg (n=65) or placebo (n=66) twice daily (with CS ≤0.5 mg/kg/d) for 37 weeks in the phase 3 PEGASUS study in moderate-to-severe pemphigus vulgaris/foliaceus (PV/PF). Results The primary endpoint of complete remission (CR) from week 29–37 with the amended endpoint CS dose ≤10 mg/d was not significant for 13/54 (24%) rilzabrutinib vs. 10/55 (18%) placebo patients with PV (P=0.45). Secondary endpoints showed numerical, but non-significant, improvements with rilzabrutinib (vs. placebo) in reduced CS use, prolonged CR duration, and faster time to first CR. Conclusions Overall, rilzabrutinib was well-tolerated with similar adverse events reported in both groups. Using minimal CS dose ≤10 mg/d and excluding remote observations, the primary efficacy endpoint was not met. However, results from a prespecified sensitivity analysis using CS dose ≤5 mg/d, considering all observations, and including all patients support BTK inhibition as a viable therapeutic approach for pemphigus.