Navigating biosimilar transitions in IV rituximab therapy: Efficacy and safety insights from a real-world switching study

AimThis study evaluates the efficacy and safety of rituximab biosimilars (BRs) compared to the original rituximab (MAB) administered intravenously, particularly from the aspect of switching and switch directions.Materials and MethodsThis retrospective study included patients treated with BR and/or MAB for hematological diagnoses. For efficacy analyses, patients with DLBCL or FL receiving BR during R-CHOP were compared with two matched-control groups treated only with MAB. Patients completing fewer than two consecutive cycles of BR or MAB were excluded. Study groups were classified as BR-only or switching (S). Switching was defined as replacing rituximab between MAB and BR for at least two consecutive cycles. Switch directions are denoted as OB (MAB to BR), BO (BR to MAB), and M (multiple switches).ResultsToxicity was evaluated in 185 patients. Responses of 69 DLBCL and 33 FL patients were compared with 52 DLBCL and 11 FL patients treated only with MAB. Median follow-up was 20 months. In DLBCL, MAB had significantly higher interim ORR and CR than BR and S (p = 0.04), but not at end-of-treatment (p = 0.081, 0.125). FL responses were similar across groups. Among 1266 rituximab infusions, 32 (2.5%) IRRs occurred, 78% during first-cycle. No difference in IRR or first-cycle reactions was seen between BR and S (p = 0.175, 0.429). IRR rates in S subgroups were 1/37 (OB), 8/35 (BO), and 4/28 (M), with BO direction higher than OB (p = 0.029).ConclusionOur findings confirm that intravenous BRs and MAB are equivalent in efficacy and toxicity, while a direction-specific increase in IRRs occurs when switching from BR to MAB, warranting further prospective studies to clarify clinical significance and guide safer treatment transitions.