Mast Therapeutics, Inc. (MSTX)

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The 505(b)(2) New Drug Application

The 505(b)(2) New Drug Application – A Rapid Approval Route

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The 505(b)(2) regulatory pathway is defined in The Federal Food Drug and Cosmetics Act as an NDA containing investigations of safety and effectiveness that are being relied upon for approval and were not conducted by or for the applicant, and for which the applicant has not obtained a right of reference. These applications differ from the typical NDA (described under Section 505(b)(1) of the Act), in that they allow a sponsor to rely, at least in part, on the FDA’s findings of safety and/or effectiveness for a previously approved drug (the “reference drug”). Section 505(b)(2) was added to the Act in 1984 with the goal of avoiding unnecessary duplication of preclinical and certain human studies. However, the sponsor must still provide any additional preclinical or clinical data necessary to ensure that differences from the reference drug do not compromise safety and effectiveness. The 505(b)(2) NDA also differs from an abbreviated NDA (ANDA; described under Section 505(j) of the Act), which is an application containing information to demonstrate that the proposed product is identical to a previously approved product.

Identity is proven in an ANDA simply through chemistry and bioequivalence data, without the need for preclinical and clinical trials assessing safety and efficacy. In a sense, a 505(b)(2) application can be thought of as a hybrid that contains more data than an ANDA, but less data than an NDA.