The US Food and Drug Administration (FDA) has approved adding adult patients with rheumatoid arthritis (RA) to the list of indications for the rituximab biosimilar Riabni (rituximab-arrx) on the basis of results of a randomized, double-blind, comparative clinical study with the CD20-directed cytolytic antibody reference product, Rituxan, the biosimilar’s manufacturer, Amgen, announced June 6.
The RA indication is specifically for adults with moderate to severely active disease who have had an inadequate response to one or more tumor necrosis factor inhibitors. Riabni was approved in December 2020 for the treatment of adult patients with non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, granulomatosis with polyangiitis, and microscopic polyangiitis.
The clinical study testing Riabni against Rituxan involved 311 patients with moderate to severe RA who received Riabni, Rituxan manufactured in the United States, and Rituxan manufactured in the European Union. The patients who received the US-manufactured Rituxan were transitioned to receive Riabni for their second dose of rituximab, whereas patients in other groups stayed with the same treatment. The trial’s primary efficacy endpoint of the change in Disease Activity Score in 28 joints using C-reactive protein from baseline to week 24 was within the predefined equivalence margin for clinical efficacy between Riabni and Rituxan. The two products also had similar safety, pharmacokinetics, and immunogenicity profiles, according to Amgen.
Currently, Riabni and Ruxience (rituximab-pvvr) are the only two approved rituximab biosimilars in the United States. Ruxience is approved for the same indications. Rituxan alone has protected orphan drug status for the indication of adult patients with moderate to severe pemphigus vulgaris.