Leflunomide is equally efficacious and safe compared to low dose rituximab in refractory rheumatoid arthritis given in combination with methotrexate: results from a randomized double blind controlled clinical trial.

Background: The standard dose of rituximab used in rheumatoid arthritis (RA) is 1000 mg but recent studies have shown that low dose (500 mg) is also effective. Efficacy of low dose rituximab in rheumatoid arthritis (RA) refractory to first-line non-biologic Disease Modifying Anti Rheumatic Drugs (DMARDs), compared to leflunomide is unknown. In a tertiary care referral setting, we conducted a randomized, double blind controlled clinical trial comparing the efficacy and safety of low-dose rituximab-methotrexate combination with leflunomide-methotrexate combination.

Methods: Patients on methotrexate (10-20 mg/week) with a Disease Activity Score (DAS) > 3.2 were randomly assigned to rituximab (500 mg on days 1 and 15) or leflunomide (10-20 mg/day). The primary end-point was ACR20 at 24 weeks. Sample of 40 had 70% power to detect a 30% difference. ACR50, ACR70, DAS, EULAR good response, CD3 + (T cell), CD19 + (B cell) and CD19 + CD27+ (memory B cell) counts, tetanus and pneumococcal antibody levels were secondary end points.

Results: Baseline characteristics were comparable in the two groups. At week 24, ACR20 was 85% vs 84% (p = 0.93), ACR50 was 60% vs. 64% (p = 0.79) and ACR70 was 35% vs 32% (P = 0.84), in rituximab and in leflunomide groups respectively. Serious adverse events were similar. With rituximab there was significant reduction in B cells (p < 0.001), memory B cells (p < 0.001) and pneumococcal antibody levels (P < 0.05) without significant changes in T cells (p = 0.835) and tetanus antibody levels (p = 0.424) at 24 weeks. With leflunomide, significant reduction in memory B cells (p < 0.01) and pneumococcal antibody levels (p < 0.01) occurred without significant changes in B cells (P > 0.05), T cells (P > 0.05) or tetanus antibody levels (P > 0.05).

Conclusions: Leflunomide-methotrexate combination is as efficacious as low-dose rituximab-methotrexate combination at 24 weeks, in RA patient's refractory to initial DMARDs. The high responses seen in both groups have favorable cost implications for patients in developing countries. Changes in immune parameters with leflunomide are novel and need further characterization.

Trial Registration: The trial was registered with the Sri Lanka Clinical Trials Registry (SLCTR), a publicly accessible primary registry linked to the registry network of the International Clinical Trials Registry Platform of the WHO (WHO-ICTRP) (registration number: SLCTR/2008/008 dated 16th May 2008).