In Teva Canada Limited v. Pfizer Canada Inc., et al. the Supreme Court of Canada (SCC) lifted a prohibition against Teva receiving marketing authorization for a generic version of Viagra™. Pfizer had planned to use Canadian Patent No. 2,163,446 to block Teva from the market until May 2014. The Court ruled against Pfizer. The Court did so on the basis that Pfizer’s patent is invalid for failing to indicate that the active compound in Viagra™ was what Pfizer had found worked in patients as of filing.

Patent ′446 relates to the use of a class of compounds (which includes sildenafil, the active ingredient in Viagra) for the treatment of erectile dysfunction (ED). Novopharm argued in the Federal Court that Pfizer’s patent was invalid for reasons of obviousness, lack of utility, and insufficiency of disclosure but the Federal Court Judge found these allegations were not justified. Novopharm appealed on utility and sufficiency but the Federal Court of Appeal dismissed the appeal.

The main issue before the SCC was sufficiency of disclosure under subsection 27(3) of the Patent Act. Patent ′446 discloses, in the description, that patient studies confirmed that one of the “especially preferred compounds” induces the desired therapeutic effect in the target patient population. While sildenafil was one of the nine especially preferred compounds listed in the description, the patent did not disclose that it was sildenafil which was so tested. Patent ′446 concluded with claims to the use of two of the especially preferred compounds for ED, one of which was sildenafil, and the Court found as a fact that a person skilled in the art would have known that one of these two compounds was the one Pfizer found had worked in patients.

In the Court’s discussion of the nature of the invention, it was held that it was improper to consider the disclosure requirement with respect to each individual claim rather than the specification as a whole. For Patent ′446, it was eventually determined that the invention was the use of sildenafil for the treatment of ED and

[t]his had to be disclosed in order to meet the requirements set out in s. 27(3) of the Act.” (Para 72)

The standard Pfizer had to meet was to enable a skilled person to produce the invention using only the teachings of the specification. Because Patent ′446 did not explicitly disclose which one of the two compounds was tested in patients, a person skilled in the art would have had to “undertake a minor research project” to determine the invention, therefore the Court held that Pfizer had not met the required standard:

The disclosure failed to state in clear terms what the invention was. Pfizer gained a benefit from the Act — exclusive monopoly rights — while withholding disclosure in spite of its disclosure obligations under the Act. As a matter of policy and sound statutory interpretation, patentees cannot be allowed to “game” the system in this way. (Emphasis added, Para 80)

Patent practitioners were hoping that the SCC would take the opportunity to clarify the disclosure requirements for utility. However, the Court only briefly addressed this issue. The Court confirmed that the invention in Patent ′446 was not based on sound prediction, but on demonstrated utility and that in such cases, there is no requirement that the utility be disclosed, or that data be included to establish utility:

At the time the application was filed, sildenafil could assist in treating ED. This is all that is required. The fact that Pfizer did not disclose that the tested compound was sildenafil goes to the issue of disclosure of the invention, not to that of disclosure of the invention’s utility. (Para 38)

As this was not a case where utility was based on sound prediction, the Court did not address the heightened disclosure requirement which has prevailed in the Federal Court for such cases.

This Decision is a clear warning to patent drafters to exercise caution when presenting information and data about their inventions in a patent application. Withholding or sparingly stating vital information can carry a heavy price. Patent applicants should be sure to seek professional counsel when drafting their patent applications to ensure that their inventions are clearly and sufficiently disclosed.