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Federal Circuit Continues Its Strict Review Of Genus Claims And Reverses Lack Of Written Description Verdict
11/25/2025In Duke University v. Sandoz Inc., No. 2024-1078, __ F.4th __ (Fed. Cir. Nov. 12, 2025), the Federal Circuit reversed a judgment of the United States District Court of Colorado, and held the sole, infringed claim invalid for lack of written description because the specification broadly discloses billions of prostaglandin compounds without representative species or adequate “blaze marks” to the claimed subgenus.
U.S. Patent No. 9,579,270 (the ’270 Patent), entitled “Compositions and Methods for Treating Hair Loss Using Non-Naturally Occurring Prostaglandins,” concerns methods for growing hair using prostaglandin F (PGF) analogs. Duke University and Allergan, co-owners of the ’270 Patent, sued Sandoz for infringement based on Sandoz’s generic version of Latisse®. After a five-day jury trial, the jury found Sandoz had not proven invalidity on any ground and awarded Allergan $39 million in damages.
The Federal Circuit reversed and held that no reasonable jury could have found adequate written description for claim 30 of the ’270 Patent. The Court noted that, for a claimed genus of chemical compounds, written description requires either (1) disclosure of a representative number of species or (2) disclosure of structural features common to the members of the claimed genus, with sufficient precision to allow a skilled artisan to visualize or recognize the members.
The record established that the specification describes prostaglandin structures so broadly as to encompass billions of compounds, while claim 30 is confined to a smaller subgenus of approximately 1,620 to 4,230 compounds. The Court found that the patent fails to disclose even a single species within the scope of claim 30, foreclosing the “representative species” route.
Regarding the “structural features” route, the Court found the specification inadequate. It noted that the generic prostaglandin “hairpin” backbone was far too broad to distinguish the claimed subgenus from the billions of disclosed compounds. At the critical C1 (R1) position, the specification presented 13 “options,” nine of which were broad categories requiring multiple embedded choices, creating a maze of branching paths rather than clear direction to the claimed amide, C(O)NHR3. Moreover, the Court found that the specification’s “preferred” and “more preferred” embodiments at C1 pointed away from the claimed subgenus, undermining the “blaze marks” theory. Given the lack of sufficient blaze marks pointing toward PGF analogs with the required elements of the compounds comprising claim 30’s subgenus, the Federal Circuit concluded that the inventors had not demonstrated possession of the full scope of the claimed subgenus as of the filing date.
The Federal Circuit determined that no reasonable juror could find adequate written description on the record and reversed the district court’s judgment. Given the invalidity holding, the Court did not reach any remaining issues.
