Safety of switching between rituximab biosimilars in onco-hematology.

Comparable clinical efficacy and safety of the reference rituximab (MABTHERA) and its biosimilars has been established in randomized trials. However, safety concerns are often raised when switching from reference to biosimilar products and between different biosimilars. In this prospective observational study we aimed at evaluating the safety of switching between reference and biosimilar rituximab (TRUXIMA and RIXATHON) at Trento General Hospital (Italy). All patients (n = 83) with Non Hodgkin's Lymphoma (NHL, n = 72) and Chronic Lymphocytic Leukemia (CLL, n = 11) who received rituximab between March 2018 and March 2019 were asked to take part in the study. In 2017 and 2018 two tenders were carried out and two different biosimilars became available in the hospital, these were used sequentially. Thus, patients with or without previous treatments with the originator rituximab either received a biosimilar or were switched between different biosimilars. The incidence of adverse events in these groups of patients is described. The study population received 465 rituximab infusions and all received biosimilars. Fifty patients (60%) experienced at least one switch between different biosimilars or between rituximab originator and biosimilar, whereas 33 (40%) received one of the two biosimilars and one patient received reference rituximab. Adverse events (n = 146) were reported in 71 patients (84.5%). Treatment-related grade 3-4 events were reported in 5 patients (5.9%), whereas grade 1 rituximab related infusion events were observed in 6 patients (7.1%). No safety signal emerged in association with the use of a specific biosimilar nor with the practice of switching. Adverse events were similar, in terms of seriousness and frequency, to those described in the literature, providing further support to the clinical safety of rituximab biosimilars.