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by Amanda Conschafter, blog editor

The Food and Drug Administration could soon approve a complex biosimilar to treat eight disease states and patient groups – even though clinical testing data has been submitted for only two. Earlier this month the FDA’s Arthritis Advisory Committee voted 21-3 in favor of full approval for an infliximab biosimilar, which could treat Crohn’s disease and rheumatoid arthritis, among other diseases. But the committee’s willingness to transfer approved uses from the complex innovator drug to its biosimilar has made some physicians and patient advocates uneasy.

[READ: What is Indication Extrapolation?]

Indication extrapolation, the process of applying one drug’s approved uses to its follow-on medications without full testing, often occurs for generic versions of traditional drugs. But the practice presents patient safety challenges for biological drugs, which cannot be duplicated exactly. Even slight variations in molecular structure can trigger different patient responses. Further, biological medications treat vastly different disease states and patient groups, some of which carry a higher risk of an immune system response. Approving medical therapies to treat these diseases without full testing exacerbates the risks.

Europe and Canada, where infliximab biosimilars are already on the market, have differed in their willingness to tolerate these risks. The European Medicines Agency granted full extrapolation for biosimilar infliximab, while Health Canada declined to extrapolate an approved use for inflammatory bowel diseases. Canadian regulators cited concerns about the clinical impact of structural differences between the biologic and the follow-on biosimilar.

In a letter to the FDA prior to the meeting, the Alliance for Patient Access argued that, “The fact that a biosimilar tested for one or two indications of an innovator product should not automatically qualify that biosimilar for other indications for which the innovator drug is approved.” During testimony at the meeting, AfPA member and Texas rheumatologist Joshua Stolow, MD, echoed these concerns, noting, “Manufacturers should be required to provide substantial clinical data supporting their requests.”

Dr. Stolow also addressed the package inserts that accompany these drugs. He emphasized that the FDA should provide “transparent and clear information about what disease states have been tested and what the clinical outcomes and potential side effects of the approved product are for that indication.” Meanwhile, other meeting participants encouraged the FDA to administer a strong surveillance program to determine that the biosimilar, once on the market, would remain safe for patients.

The FDA could announce its decision on the infliximab biosimilar as early as April 2016.

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