Biosimilars Arrive - First Biosimilar Drug Approved in the U.S. (Zarxio)

By Glenn Petrie, Ph.D.
Senior Scientific Advisor
ABC Laboratories
www.abclabs.com

On Friday, Sandoz’s Zarxio became the first biosimilar drug approved in the U.S.

Zarxio is approved for the same indications as Amgen’s Neupogen however, Zarxio was approved as a biosimilar, not an interchangeable. This means that it cannot be substituted without the approval of the physician who originally prescribed the originator drug. While Zarxio is the first biosimilar approved in the U.S., Apotex is poised to get approval of its own Neupogen biosimilar. This is indicative of the anticipated flood of biosimilars expected in the next few years. This includes Humira, Enbrel, Remicade and Lautus.

Due to their complexity, it is considerably more difficult to demonstrate the structural identity of biopharmaceuticals versus that for traditional generics. That is why the terminology is biosimilar. In addition to animal and clinical studies, structural characterization was critical to Zarxio’s approval. While Zarxio is a relatively simple molecule (18.8 kD) it still required complete analysis of its sequence, secondary and tertiary structure. The barrier to structural characterization of monoclonal antibodies is much greater. These biopharmaceuticals are large (150 kD), have multiple subunits and disulfide linkages and are glycosylated. Biosimilar developers will need to employ sophisticated analytical techniques including QToF MS, CD, peptide maps and SPR in order to show biosimilarity with the innovator’s product.