Biosimilar Uptake in Medicare Part B Varied Across Hospital Outpatient Departments and Physician Practices: The Case of Filgrastim



To examine the uptake of filgrastim-sndz (Zarxio), the first biosimilar to launch in the United States, in the Medicare Part B fee-for-service program from its launch in September 2015 to December 2017 and compare characteristics of patients and facilities that used filgrastim-sndz or originator filgrastim (Neupogen).


The 20% sample of Medicare Part B fee-for-service administrative claims data was used to extract information on claims for any filgrastim product between January 1, 2015 and December 31, 2017.


The utilization of filgrastim-sndz in Medicare Part B increased sharply between January and August 2016, surpassing filgrastim by November 2017, contributing to a 30% decrease in overall spending on this drug since 2015. Uptake was faster and larger in physician practices compared with hospital outpatient departments. About 77% of patients receiving filgrastim-sndz were new users. Utilization patterns indicated that product selection occurred at the facility level, rather than being at the discretion of the prescribing physician or driven by patient characteristics.


Uptake of biosimilar filgrastim in the Medicare Part B program occurred despite multiple challenges to the adoption of biosimilars in the US market, suggesting that substantial potential savings could be generated by improving biosimilar uptake. Our findings indicated that physician practices and hospital outpatient departments have distinctive biosimilar uptake patterns. Thus policy makers aiming to contain Medicare Part B spending might consider focusing on incentivizing biosimilar uptake among hospital outpatient departments.


Mariana P. Socal Kelly E. Anderson Aditi Sen Ge Bai Gerard F. Anderson

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