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

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.