Postdoctoral fellow Research Institute of the McGill University Health Centre Montreal, Canada
Background: Infection is an important safety concern for biologics, and relatively few real-world data analyses have compared biosimilar versus bio-originator agents.
Objectives: To compare serious infections among initiators of infliximab biosimilar (INF-B) and originator (INF-O).
Methods: We used data from the National Prescription Drug Utilization Information System, containing pan-Canadian (except Quebec) claims-level data on prescription dispensations paid from public drug programs, linked to the hospital Discharge Abstract Database and the National Ambulatory Care Reporting System. We studied adults (≥18 years) initiating INF between January 2015 and December 2019. Follow-up began from treatment initiation and continued until treatment discontinuation (no dispensation for at least 90 days) or end of study period. Serious infection was defined as the first hospitalization with ICD-10 diagnostic codes indicating infection. We compared initiators of INF-B and INF-O using Cox regression models, adjusting for potential confounders, including sex at birth, age at INF initiation, prior corticosteroids or other biologics, region, and calendar year.
Results: New-users of INF-B (2,035) and INF-O (5,107) had a median age of 45 years (interquartile range 28-62) at INF initiation. Serious infection occurred at a rate of 3.1 events per 100 person-years, PY (95% CI 2.7-3.3), and were similar for INF-B initiator (3.6/100 PY, 95% CI 3.0-4.3) and INF-O initiators (3.1 /100 PY, 95% CI 28-34). Comparing INF-B to INF-O, the adjusted hazard ratio for infection was 0.97 (95% CI 0.77-1.21).
Conclusions: In this real-world dataset, we were unable to identify clear differences in serious infectious comparing INF-B and INF-O initiators. Limitations include inability to control for residual confounders (e.g. disease severity), potential outcome misclassification, and selection bias.
