By Thomas J. Kowalski, Ryan C. Smith, Ph.D. and Brandon A. Chan, Ph.D.
Numerical patent claim limitations can be helpful to both define the metes and bounds of the claimed subject matter to deter potential infringers as well as distinguish from the prior art in advocating for patentability of the underlying subject matter during prosecution. Often, relevant chemical properties such as pH are numerically recited in patent claims. However, one aspect that may be overlooked during claim drafting is consideration of any relevant conditions at which the recited numerical claim limitations are applicable. For example, properties of compositions of matter such as pH can vary depending on the environmental conditions at which the value is measured, including temperature and pressure. Actelion Pharmaceuticals Ltd. v. Mylan Pharmaceuticals Inc., No. 2024-1641, 2026 WL 1314700 (Fed. Cir. May 13, 2026) provides an example of the pitfalls of reciting a claimed range of chemical properties without any further insight as to the conditions in which the properties are measured and the resulting treatment by the court in ascribing a meaning to such claims.
