## Facts

- Barr Laboratories filed the first ANDA for generic tamoxifen and later submitted a paragraph IV certification, triggering patent litigation and potential 180-day exclusivity under 21 U.S.C. § 355(j)(5)(B)(iv).
- A district court decision held the tamoxifen patent invalid, but the case settled on appeal; the invalidity judgment was vacated, and Barr amended its ANDA from paragraph IV to paragraph III.
- Mylan and Pharmachemie later filed ANDAs with paragraph IV certifications and were sued for infringement, resulting in 30-month approval stays under § 355(j)(5)(B)(iii).
- Barr petitioned FDA to treat it as still entitled to 180-day exclusivity and to withhold approval of any other tamoxifen ANDAs.
- FDA issued a March 2, 1999 letter granting Barr’s request and staying approval of any tamoxifen ANDA other than Barr’s, effectively preventing Mylan and Pharmachemie from entering the market until patent expiration.
- Mylan and Pharmachemie sued FDA under the FDCA and APA, arguing the stay and exclusivity interpretation were contrary to law and arbitrary and capricious; Barr intervened.

## Issues

1. Whether FDA’s March 2, 1999 decision staying approval of competing tamoxifen ANDAs reflected a permissible interpretation of 21 U.S.C. § 355(j)(5)(B)(iv) and 21 C.F.R. § 314.94(a)(12)(viii) under APA review.
2. Whether Mylan and Pharmachemie were entitled to preliminary injunctive relief against FDA’s implementation of the March 2, 1999 decision.

## Decision

- The court consolidated the actions.
- The court held FDA’s interpretation supporting the March 2, 1999 stay was impermissible and inconsistent with the statutory scheme.
- The court set aside (vacated) FDA’s March 2, 1999 action and remanded to FDA for a lawful interpretation of § 355(j)(5)(B)(iv) and the related regulation.
- The court denied Mylan’s and Pharmachemie’s motions for injunctive relief (and related requested interim relief).

## Legal Principles

- Under APA § 706(2)(A), agency action must reflect a permissible construction of the governing statute and a reasoned explanation connecting facts to the agency’s choice; action inconsistent with the statute’s operation and design may be set aside as arbitrary and capricious.
- The Hatch-Waxman 180-day exclusivity provision uses specified statutory events (including a “decision of a court” holding invalidity or noninfringement) as triggers; agency interpretations that treat those triggers in a manner that defeats the statutory function are unlawful.
- FDA may not administer exclusivity in a way that allows a first filer to block later applicants’ approvals indefinitely where the result frustrates Congress’s balance between rewarding patent challenges and enabling timely generic competition.
- When an agency adopts an unlawful interpretation within a complex regulatory program, the typical remedy is vacatur and remand for further agency action consistent with law, rather than judicially rewriting the regulatory outcome through injunction.

## Conclusion

The court invalidated FDA’s tamoxifen approval stay because it rested on an impermissible interpretation of Hatch-Waxman’s 180-day exclusivity framework and lacked adequate legal support under the APA, but it declined to grant immediate injunctive relief and instead vacated the agency action and remanded for a permissible interpretation.


Mylan Pharms., Inc. v. Henney, 94 F. Supp. 2d 36 (D.D.C. 2000)