Real-World Noninferiority Assessment of Two Filgrastim Biosimilars in Patients Receiving Myelosuppressive Chemotherapy

Abstract

PURPOSE Although multiple filgrastim biosimilars are now available in the United States, no studies comparing clinical outcomes between products have been reported. This analysis evaluated real-world outcomes of filgrastim-aafi and filgrastim-sndz in patients with select solid tumors receiving myelosuppressive chemotherapy to compare the two filgrastim biosimilars. METHODS This was an observational, noninferiority, cohort study of patients from three integrated health care systems who received myelosuppressive chemotherapy and were prophylactically initiated on filgrastim-sndz between January and November 2021 or filgrastim-aafi between June and November 2022. Patients were followed from filgrastim biosimilar initiation until the start of their next chemotherapy cycle. The primary outcome of severe neutropenia was analyzed using a binary noninferiority test with a 5% upper margin. Secondary outcomes included the incidence of emergency department or hospital encounters due to febrile neutropenia and systemic antibiotic/antifungal medication use. If noninferiority was met, adjusted logistic regression modeling was conducted. RESULTS A total of 2,730 patients who initiated filgrastim-aafi (n = 880) or filgrastim-sndz (n = 1,850) during the study period were included. The overall mean age was 55 years, 87.4% were female, 42.3% were White, and 76.6% had breast cancer. Severe neutropenia occurred in 1.8% and 1.7% of patients initiated on filgrastim-aafi and filgrastim-sndz, respectively ( P < .01 for noninferiority). The adjusted odds ratio for severe neutropenia with filgrastim-aafi compared with filgrastim-sndz was 0.91 (95% CI, 0.49 to 1.68; P = .76). Noninferiority was met for all secondary outcomes ( P < .01), and there were no adjusted statistically significant differences between the groups (all P > .05). CONCLUSION Among patients with select solid tumors receiving myelosuppressive chemotherapy, severe neutropenia outcomes were comparable between filgrastim-aafi and filgrastim-sndz biosimilars. Findings from this study may support utilization of different filgrastim biosimilars in clinical practice.