Biosimilar Naming, Extrapolation Pose Tough Questions for FDA

By Amanda Conschafter, blog editor

The FDA’s first biosimilar approval application has stirred high hopes among some members of the health care community – and heated debate among others. Filgrastim’s application has also propelled several associated issues to the forefront. The FDA’s considerations about naming conventions for biosimilars, for instance, have taken on sudden urgency. And dialogue on indication extrapolation has elicited new interest as the FDA, like Canada and the European Union before it, tackles extrapolation’s core issues: testing, cost and patient safety.

While biologic therapies require FDA approval for each individual use, or indication, for which they’re approved, biosimilars may seek approval for an indication through extrapolation.   Indication extrapolation occurs when regulatory bodies apply a biosimilar’s approval for one medical use to an additional use that mirrors another of the biologic reference product’s approved indications. Extrapolation does not, however, require the rigorous clinical testing typical of obtaining approval for specific indications. Regulators instead require biosimilar manufacturers to provide evidence of therapeutic similarity for use with the disease or patient population in question.

Thus, extrapolation effectively provides a shortcut for biosimilar approval. And it holds the key to profits for many biosimilar manufacturers. Investing in rigorous testing for each and every use of a biosimilar would increase the cost of developing these drugs. Higher prices for patients could then dampen the biosimilar market – and limit the broader access that many expect biosimilars to offer.

But testing for each indication would better satisfy physicians, many of whom express concerns about extrapolation’s affect on patient safety. As Robert Yapundich, M.D., a member of AfPA’s National Physicians Biologics Working Group explained, “Extrapolation asks physicians to forego our expectation that the regulatory framework thoroughly tests medications’ safety and efficacy for each approved use. Considering the particularly complex and sensitive nature of biosimilars and biologics, I have real concerns about what this regulatory shortcut means for the safety of my patients.”

Physician unease has already surfaced with Europe and Canada’s approval of infliximab, a Remicade biosimilar. In Europe, several medical societies discouraged their members from prescribing infliximab for certain extrapolated uses, despite the European Medicines Agency’s approval. Canada has likewise approached infliximab extrapolation with caution, and has opted to evaluate extrapolation requests on a case-by-case basis.

Back in the United States, filgrastim manufacturer Sandoz has requested extrapolation permission from the FDA. The agency’s decision could shape the emerging biosimilars market. And it will most assuredly raise debate about how the United States balances cost considerations with patient safety in the approval of these uniquely sophisticated – and uniquely sensitive – drugs.


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