Judge Sue Robinson recently granted defendants’ motion for leave to amend their answers to add the affirmative defense of intervening rights in a consolidated ANDA litigation action. See Senju Pharmaceutical Co., et al. v. Lupin Limited, et al., C.A. No. 11-271-SLR (consolidated), Slip Op. (D. Del. Dec. 14, 2012). Plaintiffs’ original complaint alleged infringement of U.S. Patent Nos. 6,333,045 and 5,880,283. Id. at 2. Prior to this motion, “plaintiffs further amended their complaint to allege infringement of [U.S. Patent No. 6,333,045] as reexamined by defendants’ ANDA No. 202-653 and also by defendants’ ANDA No. 202-709.” Id. at 2-3. Defendants subsequently “answered the amended complaints and counterclaimed to each.” Id. at 3. Approximately nine months after plaintiffs answered defendants’ counterclaims, defendants moved for leave to further amend their answers with an affirmative defense of intervening rights. Id.
Judge Robinson noted that leave to amend “shall be freely given when justice so requires.” Id. at 3 (quoting Foman v. Davis, 371 U.S. 178, 182 (1962) (quoting Fed. R. Civ. P. 15(a))). Judge Robinson then explained that under the doctrine of intervening rights, “an infringer who was engaged in allegedly infringing activities (or ‘substantial preparation was made by the infringer’ to do so) before a reexamination certificate issued may continue to infringe said claims, if the court determines that the reexamined claims are broader in scope than the original claims, and to the extent and under such terms as the court deems equitable. . . .” Id. at 4. Thus, “the doctrine of intervening rights is a defense to infringing activity occurring after reexamination.” Id.
Plaintiffs argued that defendants’ amendment would be “futile, apparently because defendants have not conceded that they have engaged in infringing activity.” Id. Judge Robinson disagreed, and noted that “at this stage of the proceedings, defendants need not so concede, but may advance the defense of intervening rights based on plaintiffs’ allegation that ‘[d]efendants have made, and will continue to make, substantial preparation in the United States to manufacture, sell, offer to sell, and/or use within the United States, and/or import into the United States the [d]efendants’ gatifloxacin ophthalmic solution which is the subject of ANDA’ No. 202-653 and No. 202-709.” Id. 4-5. Further, defendants “contend that each ANDA sets forth preparation steps sufficient to allow the proposed affirmative defense.” Id. at 5. Thus, in light of the fact that defendants demonstrated that there is “at least some evidence to support an affirmative defense of intervening rights,” Judge Robinson granted defendants’ motion for leave to amend their answers. Id.