In a major rebuke to a district court’s handling of patent eligibility, the Federal Circuit has vacated a decision that invalidated Astellas’s pharmaceutical patent under 35 U.S.C. § 101—a ruling the lower court made on its own initiative, without either party raising the issue. The court’s strong reaffirmation of the “party presentation principle” signals a warning against judicial overreach in patent litigation.
Background: The Overactive Bladder Treatment and the Patent Dispute
Astellas Pharma, the manufacturer of Myrbetriq®, an extended-release formulation of mirabegron for overactive bladder (OAB), sued multiple generic drugmakers, including Sandoz, Lupin, and Zydus, for patent infringement under the Hatch-Waxman Act. The key patent at issue, U.S. Patent No. 10,842,780 (the ’780 patent), covered a sustained-release formulation of mirabegron that overcame the “food effect”—an issue where drug absorption varies significantly depending on whether the patient has eaten.
During the litigation:
- The generic manufacturers challenged the patent’s validity only under 35 U.S.C. § 112, arguing that the claims were not enabled, lacked written description, or were indefinite.
- Sandoz explicitly waived arguments under §§ 102 (anticipation) and 103 (obviousness) before trial.
- Neither side raised a challenge under 35 U.S.C. § 101 (patent eligibility).
However, after a five-day bench trial, the district court unexpectedly ruled that the patent claims were invalid under § 101—a legal theory that had never been argued by the defendants. This ruling blindsided Astellas, prompting their appeal.
Key Patent Law Issues Addressed
1. Can a Court Invalidate a Patent on Grounds Not Raised by Either Party?
The Federal Circuit’s resounding answer: No.
The appeals court held that the district court violated the “party presentation principle”—a fundamental rule in U.S. litigation that courts must decide only the issues framed by the parties.
The Supreme Court has repeatedly reinforced this principle, stating that courts should not act as “issue spotters” on behalf of litigants. The Federal Circuit echoed this, emphasizing:
“It is for the parties—not the court—to chart the course of the litigation.”
By introducing a new ground of invalidity sua sponte, the district court abused its discretion, undermining due process, and depriving Astellas of an opportunity to defend its patent.
2. Is Patent Eligibility a Special Case Where a Court Can Rule on Its Own?
No. The district court seemed to treat § 101 eligibility like a jurisdictional question, which courts must assess even if not raised. However, the Federal Circuit flatly rejected this view, clarifying that patent eligibility is subject to the same statutory presumption of validity under 35 U.S.C. § 282 as other validity defenses.
The court noted:
- The Supreme Court has never held that § 101 must be evaluated independently by courts.
- Patent challengers bear the burden of proving invalidity—courts cannot assume this burden for them.
3. Was the ’780 Patent’s “Food Effect” Solution Merely a Natural Law?
The district court held that Astellas’s discovery of a sustained-release profile that eliminated the food effect was merely an application of a natural law, making it patent-ineligible under Mayo Collaborative Services v. Prometheus Labs (2012).
The Federal Circuit avoided ruling on the merits of this issue, focusing instead on the procedural error. However, it hinted that the district court likely misunderstood the scope of § 101, as formulation patents like Astellas’s typically claim a non-naturally occurring composition—not a law of nature.
Outcome and Key Takeaways
| Issue | Federal Circuit Decision |
|---|---|
| Court raising § 101 issue sua sponte | Abuse of discretion—violates party presentation principle |
| Treatment of § 101 as jurisdictional | Error—validity challenges must be raised by parties |
| Presumption of validity under § 282 | Applies equally to § 101 challenges |
| Future of Astellas’s patent | Remanded for ruling on infringement and § 112 validity defenses |
The Federal Circuit vacated the district court’s judgment and remanded the case for a proper adjudication—one limited to the issues actually raised by the parties (i.e., enablement, written description, and indefiniteness under § 112).
What This Means for Future Patent Cases
1. District Courts Must Stick to the Issues Raised
This ruling strongly discourages judges from introducing new invalidity arguments. It reinforces that § 101 is not a jurisdictional test and that courts cannot invalidate patents sua sponte.
2. Patent Defendants Cannot Rely on Courts to Raise Additional Defenses
Generic manufacturers (and other patent challengers) must affirmatively raise § 101 defenses during litigation. A court cannot do their work for them.
3. Clarifies That Formulation Patents Are Not Automatically “Natural Laws”
While the Federal Circuit did not directly decide whether Astellas’s patent was ineligible under § 101, its reluctance to uphold the district court’s reasoning suggests that such pharmaceutical formulation patents remain patentable under existing law.
Next Steps for Astellas
On remand, Astellas’s patent infringement claims will continue—but the case will focus only on the § 112 defenses (enablement, written description, and indefiniteness). The generics will have to prove these defenses—which are often harder to establish than obviousness or anticipation.
See also:
Article relating to patent office interim guidance on subject matter elegibility.
By Charles Gideon Korrell