In 2015 the Food and Drug Administration approved filgrastim-sndz (Zarxio), the first US biosimilar. Following rapid uptake, by March 2018 filgrastim-sndz accounted for 47 percent of filgrastim administrations among commercially insured and 42 percent among Medicare Advantage beneficiaries. The initial cost difference between the originator and biosimilar was 31 percent in the former population but negligible in the latter.
