Long-Term Safety and Effectiveness of Rituximab Biosimilar RTXM83: A Retrospective Extension Study in Brazilian Patients with Diffuse Large B-Cell Lymphoma.

Introduction: RTXM83, a biosimilar of rituximab, was approved after physicochemical, functional, non-clinical, and clinical studies demonstrated their similarity; these studies included RTXM83-AC-01-11, a multicentric double-blind international prospective pivotal study. Long-term data on biosimilars can potentially elucidate their clinical robustness and facilitate their broader adoption.

Methods: In this retrospective observational study, we analyzed a dataset from a Brazilian cohort previously randomized in the RTXM83-AC-01-11 study followed by the assessment of long-term outcomes in an observational extension phase from randomization in the RTXM83-AC-01-11 study to the last recorded evaluation. Patients with diffuse large B cell lymphoma (DLBCL) received either reference rituximab (R) or RTXM83 plus cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) as adjuvant treatment.

Results: The median follow-up period was 77.0 months. Patients with initial DLBCL stages III and IV comprised 50% of the R-CHOP group and 40% of the biosimilar group. Five (18.5%) patients, including two RTXM83-CHOP-treated and three R-CHOP-treated individuals, experienced late adverse events (AEs) of interest. No new safety signs were established. At the final assessment, the progression-free survival (PFS) rates were 93.3% and 50.0% in the RTXM83-CHOP and R-CHOP groups, respectively. Median PFS was not achieved in the RTXM83-CHOP group, which was 40.5 months in the R-CHOP group. The overall survival (OS) rates were 100% and 66.7% in the RTXM83-CHOP and R-CHOP groups, respectively. The median OS was not reached in any group.

Conclusion: This study demonstrated the long-term safety and effectiveness of RTXM83 in treating DLBCL; outcomes comparable to those of the reference product and potentially improved access to treatment have been indicated. However, further research with more diverse patient groups can validate these findings and advocate the broader adoption of biosimilars in cancer care.

Trial Registration: ClinicalTrials.gov Identifier: NCT04928573. June 16, 2021, "retrospectively registered".