Going Global On Polymorphs

• Published date: 25 March 2024
• Subject Matter: Intellectual Property, Patent
• Law Firm: Axinn Veltrop & Harkrider
• Author: Mr Ted Mathias, Aziz Burgy and Rebecca L. Clegg

We were so pleased to have the opportunity to address InformaMarkets' 13^th Annual Pharma IPR Conference in Mumbai on legal challenges to polymorph patents. Patents covering one or more crystalline forms of a drug substance at times have presented steep obstacles to generic drug manufacturers' efforts to enter the market. As we sought to make clear through our presentation, however, polymorph patents are of varying strength and susceptible to both noninfringement and invalidity challenges.

We first addressed a divide in the caselaw on how to construe claims reciting polymorphs with specific x-ray powder diffraction or infrared spectroscopy patterns. A bedrock principle of patent law is that a product or process must meet every limitation of a claim to be deemed infringing. Nevertheless, some courts have held that a claim reciting 'characteristic' XRPD peaks at different positions and intensities, for example, can be infringed even if the accused product does not match each of the peaks recited in the claim. For those courts, each peak position and intensity listed in the claim is not treated as a separate claim limitation. See, e.g., Kowa Co. v. Amneal Pharms., LLC, Nos. 14-CV-2758 (PAC), 14-CV-7934 (PAC), 2017 WL 10667089 (S.D.N.Y. Sept. 19, 2017). But other courts have stuck more closely to traditional patent law principles and required an exact match to recited peaks, subject to normal experimental error. See, e.g., In re Sebela Patent Litig., No. 14-6414 (CCC) (MF), 2017 WL 3449054 (D.N.J. Aug. 11, 2017). These differing approaches to claim construction can determine the outcome of a noninfringement defense.

We next turned to invalidity. Challenges to polymorph patents based on invalidity frequently turn on inherent anticipation, i.e., whether a prior art compound will necessarily convert to or a prior art process will necessarily produce the claimed polymorph. 'Sometimes' is not enough; the prior art compound or process must always yield at least some amount of what is claimed in the asserted patent. One notable case demonstrates the link between infringement and inherent anticipation. An originator successfully argued infringement because the accused anhydrate product would inevitably contain trace amounts of the claimed hemihydrate polymorph. But the patent was invalid for inherent anticipation because a process for making the accused...