Polymorphs are patentable subject matter in Canada and the U.S. Our prior article discussed some best practices to differentiate a new polymorph from the prior art and establish its inventiveness. Recent court decisions from Europe and Japan may be helpful for determining the best way to file not just internationally, but also in North America.
Applicants looking to patent internationally need to be familiar with the types of issues that courts have considered in key regions, like Japan and Europe. This provides insight on local patentability standards, and further highlights best practices for properly drafting a patent application that will be filed globally.
A thorough disclosure that supports the invention, establishes inventiveness, and fully discloses how to obtain the claimed polymorph will offer the highest likelihood of successfully obtaining a patent for a crystalline version of a known compound. A recent decision of the Japanese IP High Court (IPHC) in late 2012 dealt with the patentability of a crystalline form of the drug Lipitor®.1 The IPHC stated that Japanese Patent No. 3296564 did not adequately enable a person skilled in the art to make the polymorph: the patent did not specify factors such as a pH value, slurry concentration, temperature, and other additives, all of which strongly affect crystallization. The IPHC also stated that because crystalline versions of compounds generally have superior effects for pharmaceutical compounds with respect to stability, purity, and ease of handling, it would be obvious to a person skilled in the art to try to crystallize the non-crystalline compound. The method chosen for forming the crystal was also one that one skilled in the art using common general knowledge would think to apply when attempting to form the crystal.
Europe also allows the patenting of crystal forms of known compounds. The application must disclose the invention sufficiently to be carried out by a person skilled in the art.2 In an appeal case, the European Patent Office found that a patent application lacked sufficient disclosure as its claims specified that the claimed crystal was to be made by “a seed being added”.3 However, the “seed” was composed of the product that was sought to be synthesized. Therefore, the invention could not be practiced without already having made the claimed product.
In Europe, the claimed product must also be defined by its physical parameters (a common claim strategy in other jurisdictions too). For a claimed polymorph, this could include XRPD, single crystal X-ray diffraction, solid-state 13C NMR spectroscopy, and/or infrared (IR) or Raman spectroscopy. A difficulty arises as the burden of proof is on the applicant to show that their product is novel over the prior art, even where the prior art does not list these physical parameters. The Applicant may benefit from running experiments on the products made using the prior art to show that the claimed polymorph is novel, and including these experiments in the patent application. Finally, the crystal synthesized must exhibit unexpected characteristics—merely picking one polymorph that offers no benefit over the other possible polymorphs does not satisfy the requirement of inventiveness, nor does a crystal showing the benefits expected for the amorphous form (e.g. improvements in stability, filtration, and drying).4
Patenting polymorphs internationally requires careful attention to providing enough detail in the application to fully disclose and support the invention, as well as establishing its inventiveness compared to prior art. Reviewing cases where patents were challenged in Europe and Japan shows the need to fully disclose the conditions used to synthesize the crystal (solvents, temperatures, times, pH values, etc.). Do not hold back on detail that may help physically differentiate the polymorph from prior art, or that could establish inventive functional benefits.