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Explore the latest in patent, trademark, and copyright cases on the Merchant & Gould LLP blog. Stay informed with expert insights on intellectual property law updates.

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Last week, the U.S. Court of Appeals for the Federal Circuit issued an opinion in <em><a href="https://www.cafc.uscourts.gov/opinions-orders/24-1078.OPINION.11-18-2025_2605503.pdf">D</a></em><a href="https://www.cafc.uscourts.gov/opinions-orders/24-1078.OPINION.11-18-2025_2605503.pdf"><em>uke University and Allergan Sales, LLC v. Sandoz, Inc.</em>, No. 2024-1978 (Nov. 18, 2025)</a>, holding that U.S. Patent No. 9,579,270 was invalid under 35 U.S.C. § 112 for lack of adequate written description.

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Allergan’s ’270 patent claims a method of treating hair loss using prostaglandin F (PGF) analogs, which are a class of cell-signaling compounds. Allergan markets Latisse®, a PGF drug for treatment of eyelash hair loss. Allergan sued Sandoz in 2018, alleging that Sandoz’s generic version of Latisse® infringed claim 30 of the ’270 patent. Sandoz stipulated to infringement but argued that the ’270 patent was invalid for lack of adequate written description, among other defenses. A jury rejected Sandoz’s invalidity arguments and awarded Allergan $39 million in damages. The U.S. District Court for the District of Colorado denied Sandoz’s post-trial motions challenging the jury verdict, and Sandoz appealed.

The Federal Circuit reversed. The Court held that no reasonable jury could find that claim 30 meets the written description requirement of 35 U.S.C. § 112(a), which considers whether the patent specification contains sufficient disclosure such that a person of ordinary skill in the art would conclude the inventor possessed the full scope of the claimed invention at the time the application was filed. Here, the ’270 patent specification broadly discloses PGF compounds with variable physical structures, which potentially encompass a “universe of billions of compounds.” Claim 30 covers a far narrower subgenus of PGF compounds—on the order of thousands—but the specification does not provide any specific examples of compounds within the scope of claim 30. The specification also does not identify sufficient commonalities in structure that would permit a person of ordinary skill in the art to identify and obtain the specific PGF compounds covered by claim 30. Given these deficiencies, the Court found that the specification does not show that the inventor possessed the full scope of the claimed subgenus, and accordingly, the Court held that claim 30 was invalid for lack of adequate written description.&nbsp;Because the lack of written description was dispositive, the Court did not reach Sandoz’s other arguments, including collateral estoppel, lack of enablement, or jury-instruction error.

CAFC Finds Hair Loss Treatment Patent Invalid for Lack of Written Description

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