Myrbetriq® (mirabegron)
Case Name: Astellas Pharma Inc. v. Zydus, Inc., Civ. No. 20-1589, 2025 WL 1555219 (D. Del. May 30, 2025) (Bataillon, J.)
Drug Product and Patent(s)-in-Suit: Myrbetriq® (mirabegron); U.S. Pat. No. 10,842,780 (“the ’780 patent”)
Nature of the Case and Issue(s) Presented: Astellas sued Lupin and Zydus based on the generics manufacturers’ ANDA filing and their efforts to make and sell generic mirabegron. In the leadup to the 2023 bench trial, the parties exchanged validity discovery on enablement, written description, indefiniteness, and obviousness. One month before trial, the parties narrowed the case and Defendants stipulated that they would “not present any evidence on or assert as a defense at trial that the Asserted Claims are invalid for failing to comply with 35 U.S.C. § 103.” At trial, Defendants focused their arguments on the issues of enablement, written description, and indefiniteness. After trial, the court granted judgment as a matter of law to Defendants on other grounds. On appeal, Lupin and Zydus launched their allegedly infringing product. The Federal Circuit reversed. On remand, the parties disagreed on how to proceed: Astellas sought a new trial before a jury resulting from the launch of the generic product; and Defendants sought a bench trial. The court decided to proceed on a path whereby it would decide the validity issues—in which it found in favor of Astellas—and a jury would decide the infringement and damages issues. The court then consolidated the ’780 patent action with suits related to other Myrbetriq® patents. One of the patents-in-suit in the consolidated case—the ’409 patent—shares the same specification with the ’780 patent but recites narrowed claims. Other defendants in the consolidated case, Ascent and MSN, plan to assert an obviousness defense at a bench trial in November 2025. Now, Lupin and Zydus wish to discard their prior stipulation and argue obviousness at the jury trial in February 2026. Defendants filed a motion for relief from stipulation, which the court granted.
Why Defendants Prevailed: Astellas argued that the Federal Circuit’s mandate prevents the district court from relieving Lupin and Zydus of their stipulation. The Federal Circuit referenced the stipulation “to explain why the Court messed up in straying from their presentation. … And the panel was (correctly) explaining that the stipulation limited the validity theories before the Court at trial. The panel was not asked to address and did not address whether the Generics Manufactures could seek relief from the stipulation before the Court.”
The court next addressed the Waldorf factors. It found that maintaining the stipulation in the consolidated case creates two specific risks to the parties: (i) the risk of inconsistent results between defendants and patents, and the possibility that a patent is invalid for one defendant and valid for another; and (ii) encouraging unproductive satellite litigation. This unfairness supports relieving Lupin and Zydus of their stipulation. It further found that Astellas faces minimal prejudice. The issue of obviousness is not new. The parties created a record on it in 2022 and 2023, including expert discovery, and Astellas was prepared to go to trial against that theory. “Indeed, Astellas is defending against an obviousness challenge to a member of the same patent family and an obviousness challenge to the same patent in the consolidated litigation.” Finally, there has been changes in circumstances. “At the time of the stipulation, the Generics Manufacturers were litigating a single patent in an ANDA posture. Now, they are facing a consolidated case involving four patents. Thus, the litigation today implicates new uniformity concerns that were not present when Lupin and Zydus entered the stipulation.”
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