Written Description: Lessons From Duke v. Sandoz and Seagen v. Daiichi Sankyo

This CLE course will guide patent counsel on leveraging recent Federal Circuit decisions regarding applying Section 112 written description requirements in patent cases. The panel will examine lessons from these decisions and discuss how these lessons impact best practices.

Patent practitioners in every technology face §112 issues all the time, in examiner rejections during prosecution, patentability challenges in post-grant reviews before the PTAB, and validity challenges before the courts. The Federal Circuit has seemingly been raising the bar for meeting the written description and enablement requirements in recent years.

On Nov. 18, 2025, the Federal Circuit Court of Appeal continued its application of §112 stringent standards, finding invalidity for lack of adequate written description and reversing a $39 million damages award in Duke University v. Sandoz Inc. The court determined "no reasonable juror could find anything other than clear and convincing evidence that the ’270 patent fails to describe either (i) a representative number of species of claim 30's subgenus or (ii) structural features common to all members of that subgenus."

On Dec. 2, 2025, the Federal Circuit followed its decision in Duke v. Sandoz with a precedential decision in Seagen Inc. v. Daiichi Sankyo Co., providing additional clarification on how much disclosure must be included in a patent application to uphold claims covering a generic scope of chemical structures.

These decisions emphasize the strict application of the written description requirement to claims and higher disclosure standards. Patentability and enforceability are expected to be impacted by these decisions.

Listen as our panel of authoritative patent attorneys examines the lessons from recent Federal Circuit decisions and discusses how those lessons impact best practices.