⚖ Oral Arguments, with Context

The Federal Circuit considers a patent dispute over a liquid formulation of cyclophosphamide, a drug used to treat cancer. The patent owner sued a competing manufacturer, alleging that its injectable product infringed the patent. A federal district court in Illinois ruled the patent invalid because its use of the word stable did not define the protected formulation with reasonable certainty. The patent owner is asking the Federal Circuit to reverse that ruling. The practical problem is knowing which test marks the boundary between the patented formulation and something competitors may make. One claim specifies limits on certain impurities after a week at elevated temperature and humidity. Another independent claim does not repeat those limits, and the patent also describes refrigeration. The patent owner will argue that the accelerated test supplies the controlling standard and that references to refrigeration do not create another claim requirement. The competitor will argue that this narrower interpretation was not presented below and does not resolve the uncertainty across the claims. Listen for whether the patent itself tells a skilled chemist what to measure and under which conditions, and whether the position now urged on appeal matches the one presented to the district court. The issue is the boundary of patent protection, not whether the medicine is safe or effective.

Ingenus Pharmaceuticals, LLC v. Nexus Pharmaceuticals, Inc. (No. 25-1840) — U.S. Court of Appeals for the Federal Circuit, argued November 5, 2026.