Factors Influencing Infusion-Related Reactions Following Dosing of Reference Rituximab and PF-05280586, a Rituximab Biosimilar

Background: Infusion-related reactions (IRRs) are the most common adverse event (AE) associated with infusion of rituximab, an anti-CD20 monoclonal antibody. Objective: Our objective was to evaluate the impact of dosing/infusion patterns and certain baseline characteristics on IRR occurrence during the first rituximab infusion administered as the biosimilar PF-05280586 (RTX-PF) or reference rituximab sourced from the EU (RTX-EU, MabThera^®) in patients with CD20+ low-tumor-burden follicular lymphoma. Patients and methods: Rituximab (RTX-PF, n=196; RTX-EU, n=198) was administered (375 mg/m²) on days 1, 8, 15, and 22 (one cycle), with a follow-up period through 52 weeks. The relationships between infusion rate, drug exposure, and IRR incidence were assessed by logistic regression analysis and pharmacokinetic modeling and simulation. Baseline CD20 level, antidrug antibody (ADA) status, and tumor burden according to IRR occurrence (yes/no) were compared descriptively. Results: Median rituximab infusion duration on day 1 was 3.50 h for each of the two groups. There was a positive correlation between infusion rate and all-grade IRRs occurring within 24 h after infusion (p < 0.0001). Patients who developed IRRs had a higher median baseline CD20+ level. IRR incidence was unaffected by baseline ADA status. Drug exposure did not predict IRR incidence. Baseline tumor burden was similar between patients with and without IRRs. Conclusions: Results of this analysis provide a better understanding of IRRs after the first rituximab (RTX-PF or RTX-EU) infusion and demonstrate a potential correlation of infusion rate and other factors with IRR at the individual and population levels. Infusion-rate escalation steps continue to be needed to manage IRRs. Trial registration (date of registration): ClinicalTrials.gov Identifier: NCT02213263 (11 August 2014); and EudraCT: 2014-000132-41 (10 October 2014).