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Federal Circuit Affirms Preliminary Injunction Against Generic Nuedexta
07/07/2026In Otsuka America Pharmaceutical, Inc. v. Hetero Labs Limited, No. 2025-2016 (Fed. Cir. July 1, 2026), the U.S. Court of Appeals for the Federal Circuit affirmed a preliminary injunction barring Hetero Labs Limited (“Defendants-Appellants”) from launching a generic version of Nuedexta, a drug used to treat neurological disorders. Writing for the Court, Circuit Judge Bryson upheld the district court’s construction of the disputed claim terms and its finding that Otsuka America Pharmaceutical, Inc., and its subsidiary Avanir Pharmaceuticals, LLC (together, “Plaintiffs-Appellees”) were likely to succeed in proving infringement of U.S. Patent No. 7,659,282 (the “‘282 patent”). Circuit Judge Dyk dissented from the claim construction and infringement holding.
The ’282 patent, owned by Plaintiffs-Appellees, covers a method for treating pseudobulbar affect or emotional lability, such as the inability to control emotions exhibited by patients with neurodegenerative diseases or after a stroke or other brain injury. The patented method administers dextromethorphan, which provides the therapeutic effect, in combination with quinidine, which protects the dextromethorphan from rapid metabolism by the liver. Independent claim 1 recites specified daily amounts of each compound “with the proviso that the weight to weight ratio of dextromethorphan to quinidine is 1:0.5 or less,” and the patent is scheduled to expire on August 13, 2026. Plaintiffs-Appellees’ branded product, Nuedexta, combines the two compounds in salt form, with each capsule containing 20 mg of dextromethorphan hydrobromide and 10 mg of quinidine sulfate. After the FDA approved Defendants-Appellants’ Abbreviated New Drug Application for a generic with the same indications and salt amounts, and Defendants-Appellants signaled their intent to launch on or after July 10, 2025, Plaintiffs-Appellees sued in the District of Delaware and obtained a preliminary injunction.
The central dispute was how to construe “dextromethorphan” and “quinidine” in the weight-to-weight ratio when the compounds are administered in salt form. Defendants-Appellants argued the ratio must be calculated using only the active moiety components, which for its product yielded a ratio of 1:0.56 and was outside the “1:0.5 or less” limitation and, in its view, defeated any likelihood of success on infringement. Plaintiffs-Appellees countered that no conversion was required and that the ratio should reflect the amounts of the compounds administered, whether in free base or salt form, producing a 1:0.5 ratio for both Nuedexta and Defendants-Appellants’ generic.
The Court adopted Plaintiffs-Appellees’ construction, holding that the terms refer to the compounds in whichever form they are administered. The Court’s reading is grounded in the intrinsic evidence: dependent claims 7 and 8 expressly require the compounds “in a form of a pharmaceutically acceptable salt,” so the same terms in claim 1 must include the salt forms; the specification defines the active ingredients to include both free base and salt forms and repeatedly uses the terms (and the abbreviations “DM” and “Q”) as shorthand for salt-form doses in the clinical studies; and the prosecution history showed the examiner understood the terms to encompass the salts. The Court also found it “highly improbable” that Plaintiffs-Appellees would have drafted claims excluding their own Nuedexta product, which under Defendants-Appellants’ approach would itself fall outside claim 1. Rejecting Defendants-Appellants’ indefiniteness argument, the Court explained that for any particular product only the specific salts used would be measured, leaving “only one way to calculate the weight-to-weight ratio,” and it gave the contrary opinion of Defendants-Appellants’ expert less weight as extrinsic evidence at odds with the intrinsic record. The Court therefore held the district court did not err in finding a likelihood of success and acted within its discretion in granting the injunction.
In his dissent, Judge Dyk notes he would have construed the terms in light of the invention’s purpose, reducing the blood level of quinidine while maintaining a therapeutically effective level of dextromethorphan, and concluded that the claimed weight measurements were designed to account only for the active moieties. In his view, measuring salt weights “distorts the relative measurement” and produces a result “contrary to the inventive purpose,” and Plaintiffs-Appellees could have drafted the claims to reference salt weights but did not. Concluding that Defendants-Appellants had raised a substantial question of noninfringement, he would have reversed the preliminary injunction.
IP Litigation