Uptake of Biosimilar Among Privately Insured Patients Undergoing Infliximab Treatment.

Abstract

Recent literature has found rapid uptake of short-acting filgrastim biosimilars but slower uptake of other biosimilars, such as infliximab, in both Medicare and privately insured enrollees. To describe patient, provider, and health plan characteristics associated with a switch to biosimilar among existing infliximab patients. We constructed a retrospective panel dataset of patients undergoing active infliximab treatments and the choice of infliximab drug for each infusion. We used mixed logit regression controlling for patient, provider, and health plan characteristics as well as time-fixed effects. Medicare Advantage and privately insured enrollees with evidence of active infliximab treatments between 2016 and 2020 (n=357,430). Our primary outcome of interest was to switch from infliximab originator to one of the infliximab biosimilars. Exposure variables of interest variables such as out-of-pocket, site of care, and in-network deductible. Our study found nominally low switching among existing infliximab originator users (3.4%). We found that patients who previously received 1 infliximab originator infusion were 63.7% more likely to switch to biosimilar compared with patients who previously received administration of 20 infliximab originators. We found that biosimilar's placement as health's plan preferred drug was attributed to higher likelihood of biosimilar use (odds ratio: 1.666; P -value=0.001). We did not observe any statistically significant effect among out-of-pocket amount or deductible with respect to switch to infliximab biosimilar. To encourage uptake and switch to biosimilar, policymakers should consider targeted policies that include leveraging health plan tools such as placement of biosimilar as preferred drug and aim to educate patients on the clinical equivalence between infliximab biosimilar and originator.