Looking Into The Crystal Ball – Protecting Polymorphs To Lengthen The Drug Patent Life Cycle

Innovative pharmaceutical companies are increasingly attempting to patent improved forms of their original drug compound. Crystalline forms of a drug, called polymorphs, are one such improvement.1 A polymorph drug may provide benefits such as better efficacy, solubility, shelf life, or ease of manufacture, which can translate into increased adoption of the drug and higher sales. Patenting a polymorph also starts an additional 20-year patent term, which may help keep generic competition off the market longer.

Patentability of Polymorphs

Polymorphs are patentable subject matter in Canada and the U.S. The Federal Court of Canada dealt with the patentability of novel crystalline forms of known compounds in Abbott Laboratories v Canada.2 In this case, Ratiopharm sought approval to market Clarithromycin (6-O-methylerythromycin) in Canada. Although Abbott did not invent the Clarithromycin compound per se, they did own Canadian Patent No. 2,258,606, which claimed two different crystalline versions of the polymorphic drug. The claims covered two different crystalline forms of Clarithromycin that were distinguishable by their X-ray powder diffraction (XRPD) pattern: this effectively made...