Principia Biopharma Inc. announced it has completed patient enrollment into the global Phase 3 PEGASUS trial for rilzabrutinib, an oral investigational Bruton tyrosine kinase (BTK) inhibitor. PEGASUS is a global, randomized, double-blind, placebo-controlled, pivotal, Phase 3 clinical trial enrolling approximately 120 participants to evaluate rilzabrutinib versus placebo, using a background treatment of tapering doses of corticosteroids (CS). The trial entry criteria include participants with moderate to severe pemphigus who are either newly diagnosed or relapsing with chronic disease. This demographic will potentially represent three quarters of the pemphigus patient population. The primary efficacy endpoint is the ability of rilzabrutinib to achieve durable complete remission (CR) at 37 weeks of treatment. Durable CR is defined as a state in which all lesions have healed on very low dose CS (5mg/day), and no new lesions have appeared for a period of at least eight weeks. Key secondary endpoints include cumulative CS use and time to CR. At 37 weeks, all patients will have the option to be treated with active rilzabrutinib therapy in an open-label extension period of 24 weeks. Rilzabrutinib has been granted orphan drug designation by the U.S. Food and Drug Administration and the European Commission for the treatment of patients with pemphigus.