Counting is one of the first things you learn as a child, sort of like this bunny counting carrots in his cart. While counting may seem relatively easy, sometimes it’s not so simple when interpreting patent claims.

“pH of 13 or higher”

To improve the product’s stability, the developers of Veletri®(epoprostenol) focused on its pH level and then claimed in its patent a bulk solution that has a “pH of 13 or higher.” This seems simple enough, but the pH of Mylan’s ANDA product was lower than 13, but not by much, apparently. The ensuing PIV case and claims construction swirled around the meaning of 13.

13 is 13 or is it?

Mylan argued that 13 means 13 and anything below 13 is non-infringing. Patent holder Actelion disagreed and asked the West Virginia District Court to construe the meaning of “pH of 13 or higher” to mean a lower number that could be rounded up to 13, such as 12.91. Looking only at the “intrinsic” evidence (in this case the patent and specifications) for the answer, the Court agreed with Actelion that a pH as low as 12.5 should be rounded up to 13. At that point, the parties agreed to infringement. Mylan appealed.

Court of Appeals Challenges the Process

The Court of Appeals for the Federal Circuit reversed the decision. It concluded that the intrinsic evidence alone could be construed either way. As such, it sent the case back to West Virginia (“remanded”) and asked the Court to consider “extrinsic” evidence (anything else relevant outside of the patent and its specifications). It reasoned that the extrinsic evidence could determine the standard of practice which would indicate how strictly 13 should be construed. For example, would most skilled in the art consider a number like 12.95 to be “close enough” to 13 to mean 13?

Back in West Virginia, the parties completed a second bench trial on this question on February 20, 2024. The bench trial included the testimony of several expert witnesses and reliance on the United States Pharmacopeia. A month later, the West Virginia District Court concluded that a “person skilled in the art” would have concluded that a pH of 13 is indeed 13 when developing the product. As Mylan’s formulation was lower than 13, it concluded Mylan did not infringe. Actelion has appealed.