Enantiomer Exclusivity Revisited - The Food and Drug Administration Amendments Act of 2007

Tucked away at the end of the Food and Drug Administration Amendments Act of 2007 (FDAAA) is a provision that modifies FDA?s long-standing refusal to award five-year new chemical entity (NCE) exclusivity to enantiomers of previously-approved racemic mixtures. Pub. L. No. 110-85, __ Stat. __ (2007); FDAAA § 1113.

The Food and Drug Administration (FDA) has the authority under the Hatch Waxman Act to grant five years of exclusivity to drugs that contain new chemical entities, referred to as NCE exclusivity in the Orange Book, but up until this legislation FDA had declined to grant NCE exclusivity to enantiomers that were part of previously-approved racemic mixtures. See Federal Food Drug and Cosmetic Act (FDCA) §§ 505(c)(3)(E)(ii) and 505(j)(5)(F)(ii). According to FDA, exclusivity was not justified because the enantiomer had been previously approved ? albeit as part of a racemic mixture. See 54 Fed. Reg. 28872 at 28898 (July 10, 1989).

In an effort to encourage the continued development of these important chemical species, the FDAAA has modified FDA?s policy with the addition of a new subsection (u) to section 505 of the FDCA, so that FDA can award NCE exclusivity to enantiomers under limited circumstances. However, to ensure that the exclusivity fosters significant medical innovation and does not become simply another tool for life cycle management, the legislation limits the award of exclusivity to particular circumstances.


Life cycle management was clearly a concern to Congress in granting this exclusivity, and the legislation contains several limitations that ensure exclusivity is only awarded in cases of significant medical innovation. For example, exclusivity is only available for new drug applications that do not rely on studies for a previously approved racemic mixture. FDCA § 505(u)(1)(A), as amended by FDAAA 1113. Exclusivity is also only available if the enantiomer is approved in a different therapeutic category than the racemic mixture. FDCA § 505(u)(1)(B), as amended by FDAAA 1113. Conversely, FDA will not approve the enantiomer for use in the same therapeutic category as the racemic mixture for ten years from the enantiomer?s approval date. FDCA § 505(u)(2)(A), as amended by FDAAA 1113.

Unless the legislation is reauthorized, the exclusivity is only available for new drug applications filed before October 1, 2012. FDCA § 505(u)(4), as amended by FDAAA 1113