Exelixis v. MSN Laboratories — Federal Circuit Upholds Cabometyx Patent Claims and Vacates Moot Ruling

Background

Exelixis owns patents covering crystalline cabozantinib (L)-malate, the active ingredient in Cabometyx, a cancer treatment. MSN challenged claims of U.S. Patent Nos. 11,091,439, 11,091,440, 11,098,015, and 11,298,349 after seeking approval for a generic product. The Delaware district court rejected MSN’s written-description and obviousness challenges.

The Court’s Holding

In a precedential ruling, the Federal Circuit affirmed that asserted claims of three Cabometyx-related patents had adequate written-description support. It dismissed as moot MSN’s appeal concerning claim 3 of a fourth patent and vacated the district court’s nonobviousness judgment for that claim.

The court held that the specifications demonstrated possession of the claimed crystalline salt and that the claims did not improperly outrun the disclosed invention. It distinguished precedent involving claims broadened beyond what the patent’s figures and description conveyed. The separate dispute over claim 3 of the ’349 patent became moot after Exelixis dropped the relevant cross-appeal. Because that unilateral action prevented appellate review, the panel applied the usual mootness remedy and vacated the district court’s judgment on that claim.

Key Takeaways

• A specification can support claims to a crystalline pharmaceutical form when it conveys possession of that form to a skilled artisan.
• Written description is a fact-intensive inquiry, and appellate review respects supported district-court findings.
• When an appellee’s action moots an appeal, vacatur may clear the unreviewable judgment from having future effect.

Why It Matters

The decision protects key patent coverage for Cabometyx while narrowing the judgment that can carry forward concerning the separate ’349 patent. For pharmaceutical litigants, it is a significant precedential application of written-description doctrine to claimed crystalline drug forms.