A double-blind, placebo-controlled study of anti-CD5 immunoconjugate in patients with rheumatoid arthritis. The Xoma RA Investigator Group.

Objective: To evaluate the efficacy of an anti-CD5 ricin-linked immunoconjugate (CD5-IC) in patients with rheumatoid arthritis (RA).

Methods: A total of 104 evaluable patients were enrolled in a multicenter, double-blind, multiple-dose, placebo-controlled study of CD5-IC.

Results: Treatment with CD5-IC in doses up to 8 mg/m2/day for 4 days in 1 month failed to produce marked or prolonged T cell depletion and was no more effective than placebo in ameliorating disease manifestations. An unexpectedly high placebo response was observed in 48% of the patients. Adverse events were correlated with the dose of CD5-IC, but the treatment was generally well-tolerated.

Conclusion: At the doses used in this study, CD5-IC was ineffective for treating RA.