FDA Responds to Citizen Petition & Publishes Revised BE Recommendations for Difluprednate

On Wednesday, February 15th, the FDA issued a revised draft guidance, entitled “Draft Guidance on Difluprednate.” regarding its bioequivalence recommendations for the product.  In the revised document, FDA “provides specific guidance on the design of bioequivalence (BE) studies to support abbreviated new drug applications (ANDAs) for difluprednate emulsion.”


In 2008, the FDA approved the New Drug Application (NDA) for Durezol (diflprednate emulsion).  Durezol is a “topical corticosteroid that is indicated for the treatment of inflammation and pain associated with ocular surgery and the treatment of endogenous anterior uveitis.”  In January 2016, the Agency issued an initial draft guidance regarding its BE recommendations for the generic version of this product.

Citizen Petition & Revised Draft Guidance

In September 2016, a citizen petition was submitted by Alcon and Novartis.  In this petition, the companies “argued that the in vitro-only option proposed by FDA is insufficient to measure bioequivalence for difluprednate ophthalmic emulsions, and called for the agency to remove the option,”.  In a recent RAPS article, it was noted that “the companies also requested that FDA require companies taking the in vivo route measure the active metabolite, 6α, 9-difluoropredisolone 17-butyrate (DFB) of difluprednate instead of the parent drug.”

FDA responded to this petition by denying the first part of the companies’ request and accepting the second part.

In its response, FDA wrote the following:

“We disagree with the contention that the in vitro option is insufficient. The in vitro option is a weight-of-evidence approach based on testing that demonstrates comparative physicochemical characteristics and drug release rate to the RLD.”

In addition, the Agency also noted that its draft guidance for difluprednate only recommends in vitro testing if the proposed generic is Q1/Q2 the same as the RLD.  Furthermore, FDA states that “for a Q1/Q2 generic difluprednate ophthalmic emulsion product, the only clinically meaningful difference from the RLD would be in its physiochemical properties and drug release rate, which would arise from differences in the product’s manufacturing process or formulation steps. When a Q1/Q2 generic difluprednate ophthalmic emulsion product has comparative physiochemical properties and a comparative drug release profile to the RLD, the two products are expected to be bioequivalent.”

However, the Agency did partially accept Alcon’s argument regarding the in vivo option.  As such, the FDA “will request that generic sponsors submit DFB metabolite data in their BE demonstration in addition to data on the parent drug.”

For additional information, view the Citizen Petition, FDA’s response, and the Agency’s revised draft guidance on the subject.
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