On Mar. 6, 2015, the The U.S. Food and Drug Administration (FDA) approved filgrastim-sndz (Zarxio, Sandoz, Inc.), the first biosimilar product available in the U.S. Zarxio has the same mechanism of action, route of administration, strength, and dosage form as Amgen’s Neupogen.

Filgrastim-sndz is biosimilar to filgrastim (Neupogen; Amgen), a granulocyte CSF agent, which was originally approved by the FDA in 1991. The formulation of filgrastim-sndz differs from that of filgrastim by 1 inactive component.

The FDA’s approval of filgrastim-sndz was based on a review of evidence that included structural and functional characterization, animal study data, human pharmacokinetic and pharmacodynamics data, clinical immunogenicity data, and other clinical safety and effectiveness data that demonstrate that filgrastim-sndz is biosimilar to filgrastim. Filgrastim-sndz has been approved as a biosimilar drug, but not as an “interchangeable” drug; therefore, it cannot be substituted for filgrastim without authorization from the prescriber.