The Federal Court of Appeal recently affirmed a trial decision relating to two competing patents over Gilead’s SOVALDI (sofosbuvir). In the trial decision, as previously reported, the Court declared Idenix’s Patent No. 2,490,191 invalid on the basis of insufficiency of disclosure and inutility, while upholding the validity of Gilead’s Patent No. 2,527,657 (657 patent).

Idenix’s appeal on both patents was dismissed unanimously by the Court of Appeal (2017 FCA 161). In its decision, the Court noted that the case did not raise new issues of law, and was primarily directed to whether there were reviewable errors made by the trial judge.  Nonetheless, some points of interest arose which may have broader applicability to future cases.

Test for sufficiency of disclosure. On the matter of the disclosure, the Court reiterated that patents are not directed to lawyers or judges, but to a person skilled in the art—accordingly it would not be correct to apply the test of whether there is “express written disclosure.” Instead, common general knowledge must be considered in interpretation.

Skilled person and witness evidence.  Idenix argued that the trial judge erred by using one of their fact witnesses (a chemist employed by Idenix involved in chemical synthesis at the relevant time) as a proxy for the skilled person. While this argument was rejected, the Court of Appeal cautioned that courts must be “careful not to lose sight” of the identity of the person of ordinary skill in the art, who is a “mythical creature”—not a real person. Thus, courts must be informed by evidence as to the knowledge of the skilled person and what they would have been able to do with that knowledge.

Analysis of sufficiency and post-filing date evidence.  One of the main issues in this case was whether a skilled person would have been able to synthesize the compound given that the disclosure of Idenix’s patent did not explicitly teach a required fluorination step. Idenix argued that there were three potential approaches to the particular synthesis which would have been tried by the skilled person with success, as proven by post-filing date evidence.  The Court of Appeal minimized the relevance of this evidence as it reflected the benefit of hindsight rather than the skilled person’s knowledge as of the date of filing.

Drawing an analogy to Teva v Pfizer (Sildenafil), 2012 SCC 60, the Court held that the specification  required a skilled person to work out a problem: specifically, to determine which pathway, reagents, and reaction conditions would successfully lead to the claimed compound rather than leading the skilled person step by step through the synthesis.  This constituted “a burden beyond that borne by the text of paragraph 27(3)(b) of the Patent Act” and therefore rendered the patent insufficient.

Other issues. The Court did not address sound prediction of utility, as it agreed with the trial judge’s finding of invalidity on the basis of insufficient disclosure.  The Court also upheld the trial judge’s finding that Gilead’s 657 patent was valid.