New Data Underscore the Utility of Rituximab in Treating Pemphigus Vulgaris

Genentech has announced that a phase 3 study of its brand-name rituximab, Rituxan, met its primary end point and demonstrated that treatment with rituximab is superior to treatment with mycophenolate mofetil in patients with moderate to severe pemphigus vulgaris (PV), a rate autoimmune disease that affects the skin and mucous membranes.

In the PEMPHIX study, a double-blind, double-dummy, active-comparator, parallel arm study in patients requiring oral corticosteroids, patients were randomized to receive either rituximab plus a placebo or mycophenolate mofetil plus a placebo for 52 weeks along with steroids, with the aim of tapering the steroid dose to 0 by week 24.

The primary end point at week 52 was the percentage of participants who achieved sustained complete remission without treatment failure; the study met this end point, with 40.3% of patients treated with rituximab, versus just 9.5% of patients treated with mycophenolate mofetil, achieving sustained complete remission without steroids for 16 weeks or more (P = .0001).

Secondary end points also favored rituximab, says Genentech: Patients treated with the biologic had lower cumulative oral corticosteroid doses, fewer flares, a greater likelihood of sustained complete remission, a lower likelihood of flares, and greater improvements in quality of life. Adverse events were consistent with the known profile of rituximab.

The results were presented in a late-breaking oral presentation during the 28th Congress of the European Academy of Dermatology and Venereology in Madrid, Spain.

The FDA first approved the brand-name rituximab for PV in 2018 on the basis of a different phase 3 study, the Ritux 3 trial, which showed that rituximab plus corticosteroids was superior to corticosteroids alone as first-line treatment for patients with PV. As a results of the findings, the International Bullous Disease Consensus Group reached an international consensus to recommend rituximab and corticosteroids as first-line therapy for moderate to severe PV.

The newly reported data could help Genentech and its innovator drug stay ahead of biosimilar competition, at least in the PV market; notably, the 2 currently FDA-approved biosimilar rituximab products, Pfizer’s Ruxience and Celltrion’s Truxima, are not approved to treat PV. The biosimilars both have so-called “skinny labels” due to patent protections and exclusivities for the reference drug. Neither drug has yet announced a launch date for the US marketplace.