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Last week, the U.S. Court of Appeals for the Federal Circuit issued a precedential decision in <a href="https://www.cafc.uscourts.gov/opinions-orders/25-2016.OPINION.7-1-2026_2717310.pdf"><em>Otsuka America Pharmaceutical, Inc. v. Hetero Labs Limited</em>, No. 2025-2016 (July 1, 2026)</a>, affirming in part and vacating in part a preliminary injunction barring Hetero from launching a generic version of Nuedexta, a drug used to treat pseudobulbar affect (“PBA”).

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The ’282 patent claims methods of treating PBA by administering dextromethorphan with quinidine at a weight-to-weight ratio of “1:0.5 or less.” The central issue was whether the ratio should be calculated using total compound weight—including salts—or only the active moiety. Otsuka argued the ratio should be calculated using the amounts administered, regardless of salt form—a construction under which both Nuedexta and Hetero’s generic would fall within the claimed ratio. Hetero countered that only active moiety weights should be used, placing its product outside the claim scope at a ratio of 1:0.56.<del></del>

The Federal Circuit agreed with Otsuka. Intrinsic evidence showed the claims and specification used “dextromethorphan” and “quinidine” to encompass free base and salt forms. Dependent claims 7 and 8 recite administration “in a form of a pharmaceutically acceptable salt,” indicating the independent claim includes salts. The specification used the terms as shorthand for salt forms in clinical studies and defined the active ingredients to include salts. The prosecution history likewise favored Otsuka: the examiner described the invention as covering “dextromethorphan or dextromethorphan hydrobromide” and “quinidine or quinidine sulfate."

Extrinsic evidence also supported Otsuka because Hetero’s interpretation would exclude Nuedexta from claim scope, and it would be “highly improbable” that the patentee drafted claims excluding the product the patent was intended to protect. Rejecting Hetero’s indefiniteness arguments, the Court affirmed the preliminary injunction.<del></del>

The Court, however, vacated the district court’s decision to waive the Rule 65(c) bond requirement. Under Third Circuit law, the bond requirement is “strictly interpreted” and has “never [been] excused” where an injunction prevents commercial activities such as Hetero’s generic launch. The Court remanded for the district court to set an appropriate bond.

Judge Dyk dissented on claim construction, arguing “dextromethorphan” and “quinidine” refer to specific molecules, and that the ratio should be calculated using active moiety weights. He reasoned that measuring salt weights distorts the measurement in a manner inconsistent with the patent’s inventive purpose.

<em>Coauthored by James Beard and Elle Maggio</em>

CAFC Affirms Preliminary Injunction in Pharmaceutical Patent Case, Addresses Claim Construction of Salt-Form Compounds

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