Effects of administration of an anti‐cd5 plus immunoconjugate in rheumatoid arthritis. results of two phase ii studies

Abstract Objective. To evaluate the safety and activity of an immunoconjugate of ricin A chain and anti‐CD5 monoclonal antibody (anti‐CD5 IC), with and without concomitant methotrexate and/or azathioprine, in the treatment of rheumatoid arthritis (RA). Methods. Seventy‐nine patients with active RA were enrolled in 2 prospective open‐label protocols. Results. Using composite criteria, response rates were 50–68% at 1 month and 22–25% at 6 months. Transient depletion of CD3/CD5 T cells was observed on days 2 and 5 of treatment, with reconstitution on day 15 or day 29. Treatment‐associated adverse effects were common but resolved rapidly without sequelae. Conclusion. These findings suggest activity of anti‐CD5 IC in active RA and warrant confirmation in a multicenter randomized study (currently underway).