Longer rilzabrutinib treatment led to improved pemphigus control

Bruton tyrosine kinase inhibitor rilzabrutinib, in association with longer treatment, showed improved clinical activity in patients with pemphigus, according to a study reported at the American Academy of Dermatology virtual meeting.

“The Bruton tyrosine kinase system, or BTK system, is involved in two major arms of the immune response, the rapid onset innate immune response as well as the delayed onset adaptive immune response,” Deedee F. Murrell, MD, of the UNSW Medical School department of dermatology, said in the presentation. “By inhibiting both arms of this immune response with BTK inhibitors, you could get a more rapid onset of disease control in addition to the longer-term autoantibody suppression.”

In part B of a phase 2 open-label study, 15 patients with mild to severe pemphigus were evaluated. Patients received oral rilzabrutinib (formerly known as PRN1008, Principia Biopharma) either alone or with a low-dose corticosteroid. Dose escalation was allowed at the investigator’s discretion. Disease control at week 4 was evaluated as the primary endpoint.

Study results yielded disease control rates of 60% at week 4 and 87% at week 12, with the Pemphigus Disease Area Index score improving to either 0 or 1 in two-thirds of patients. The longer-term treatment led to complete remission rates calculated as 40% at week 28 in part B of the trial vs. 25% at week 24 in part A of the trial.

“Rilzabrutinib achieved high complete control disease activity and rapid onset,” Murrell said. “It was very well tolerated with only mild to moderate side effects.”