FDA Approves Neupogen Biosimilar, First in US

March 6, 2015

The filgrastim biosimilar Zarxio, the first approved in the US, can be used to treat patients with acute myelogenous leukemia and bone marrow transplants, among other conditions. A biosimilar form of the rheumatology drug infliximab may be close on its heels.

The US Food and Drug Administration today approved a biosimilar medication analagous to the biological response modifier Neupogen (Amgen). This is the first biosimilar to be approved in the United States.

Biosimilars are manufactured biologically, rather than through chemical processes, which makes them distinct from generic drugs that are chemically identical to the originally approved reference medication. Numerous biosimilars are already approved and in use in Europe, Asia, and South America.

Developed by Sandoz under the name Zarxio, the newly approved form of filgrastim is indicated for the same uses as the reference Neuopogen, for treatment of acute myeloid leukemia, severe chronic neutropenia, and for patients undergoing bone marrow transplants, therapy with autologous blood progenitor cells, or myelosuppressive chemotherapy.

Numerous biosimilars to biologics used in rheumatology are currently in testing for use in the US. The first likely to be approved is Remsima (Celltrion), a biosimilar to infliximab, which the FDA is scheduled to review on March 17, rheumatologist Jonathan Kay MD, professor of medicine at the University of Massachusetts Medical School, told Rheumatology Network. "If the advisory panel votes favorably," he added, "we might see a biosimilar monoclonal anti-TNF antibody in several months."

See also: Infliximab Biosimilars Launch in Europe. So What?
By Lothar Kirsch MD (Rheumatology Network,  February 23, 2015)

Relevant to concerns about immunogenicity among patients who have already used Neupogen, Zarxio is approved as "biosimilar" but not as "interchangeable" under the terms of the Biologics Price Competition and Innovation Act of 2009.

To designate a drug as interchangeable, "we would have to be comfortable that switching [between reference drug and biosimilar] would not introduce any dangers to the patient," explained John Jenkins MD, director of the Office of New Drugs at FDA's Center for Drug Evaluation and Research, at a press briefing. "There might be the development of drug-specific antibodies to the biosimilar drug that may interfere with safety or effectiveness."

Because Zarxio is not classed as "interchangeable" for Neupogen, pharmacies and pharmaceutical benefit managers may not substitute it without a orders from a physician (although regulation of this issue is up to the individual states).

However, Jenkins said, physicians are at liberty to prescribe the biosimilar for patients already exposed to Neupogen. Whether to choose the biosimilar or the reference product is "up to the prescriber."

Zarxio will not reach the market immediately. It is currently subject to a preliminary injunction brought by Amgen. The hearing on that lawsuit is scheduled for March 13.