Different Dosing Regimens of Rituximab Biosimilar in Rheumatoid Arthritis: A Comparative Analysis of Disease Activity Control, B-cell Depletion and Adverse Effect Profile

Author(s): Syamasis Bandyopadhyay, Aheli Ghosh Dastidar, Sandip Kumar Chandra.

Introduction: Rituximab is an established biologic DMARD for refractory rheumatoid arthritis (RA), but its high cost restricts access in low- and middle-income countries. Biosimilar rituximab (bRTX) provides a more affordable option with proven efficacy and safety. While reduced-dose regimens have shown non-inferiority to the standard regimen in originator RTX, real-world evidence on bRTX in India is limited. This study compares clinical outcomes and B-cell depletion with two bRTX dosing strategies in RA. Methods: We retrospectively analysed bDMARD-naïve RA patients with inadequate response to conventional DMARDs who chose to receive either 1000 mg × 2 or 500 mg × 2 doses of bRTX. Disease activity (DAS28-ESR/CRP), ACR50 responses, and CD19+ B-cell counts were assessed at baseline and 12 months. Between-group comparisons were performed using Student’s t- test. Results: The mean DAS28-CRP decreased from 5.23 ± 0.10 to 3.62 ± 0.44 in the 1000 mg group and from 5.24 ± 0.09 to 3.65 ± 0.59 in the 500 mg group. ACR50 response rates were 84.6% and 78.6% in the standard- and reduced-dose groups, respectively, with no significant difference in disease activity reduction (p > 0.05). CD19+ counts (/uL) fell from 1222 to 127 in the 1000 mg group and from 1223to 134 in the 500 mg group. Conclusion: Both standard and reduced bRTX regimens achieved comparable clinical efficacy and B-cell depletion over 12 months. The 500 mg regimen may represent an economically-viable alternative for RA management in resource-constrained settings.