Association for Public Policy Analysis & Management

The US Food and Drug Administration has recently identified the market uptake of biosimilar drugs as an important issue. However, the forces driving uptake dynamics are not well understood, and correlates of provider characteristics and biosimilar uptake remain largely unexplored. This paper identifies provider uptake of biosimilar filgrastim and assesses the factors associated with a provider’s decision to switch from prescribing the biologic version of the drug to the biosimilar version. Commercial claims for the use of granulocyte colony-stimulating factors (G-CSFs) among providers from January 2015 to December 2017 were analyzed. We focused on providers with filgrastim claims in at least two consecutive quarters and examined provider administration of biologic filgrastim (Neupogen), biosimilar filgrastim (Zarxio), or both across the hospital and individual practice settings. We investigated associations between provider switching from the biologic to biosimilar and patient cost, adjusted for patient demographics.

Biosimilar uptake increased steadily from 2016Q1 to 2017Q4, reaching 50.1% of filgrastim patients by the end of our study period. Over the study period, the proportion of filgrastim providers with only claims for the biologic decreased from 88% to 49%, while the proportion with only biosimilar claims increased from 6% to 44%. Individual providers adopted biosimilar filgrastim earlier and more quickly than did hospitals. Individual providers with higher proportions of patients who were non-white (adjusted OR=1.66, 95% CI=1.25-2.20) and facing positive copays (adjusted OR=2.48, 95% CI=1.50-4.11) were more likely to switch to the biosimilar. Hospital providers who switched did not differ from non-switchers on these dimensions.

Switching to the biosimilar filgrastim was associated with individual providers with more non-white patients and patients facing positive copays. Provider incentives and awareness of biosimilars may be key levers to increase biosimilar market penetration.