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Viagra patent invalidated: SCC suggests patentee “gaming” the patent system

November 09, 2012

Yesterday, the Supreme Court of Canada (SCC) released a decision that underlines a patentee’s disclosure requirements under the Patent Act.  This decision is another in a line of recent Canadian cases that have struck down pharmaceutical patents on the basis that the patentees failed to live up to the disclosure obligations that are one side of the quid pro quo at the heart of the patent system.

The case, Teva Canada Ltd. v. Pfizer Canada Inc. 2012 SCC 60, involves the Canadian patent for Pfizer’s Viagra drug.  Although several grounds for invalidity were raised throughout the proceedings, the main issue for the SCC was whether Patent no. 2,163,446 (the ‘446 Patent) met the disclosure requirements under the Patent Act. The SCC unanimously found the ‘446 Patent invalid for lack of sufficient disclosure, overturning the earlier decisions of the Federal Court and Federal Court of Appeal.

The ‘446 Patent pertained to the use of a compound for the treatment for erectile dysfunction.  The ‘446 Patent ended with a set of cascading claims for successively smaller ranges of compounds, with claims 6 and 7 relating to a single compound each.  Claim 7 specifically claimed the compound sildenafil.  At the time of Pfizer’s filing of the ‘446 Patent, Pfizer’s testing had only found that sildenafil was effective in treating erectile dysfunction.  None of the other compounds had been shown to be effective.  The question addressed by the SCC was whether the ‘446 Patent sufficiently disclosed that the invention was of the use of sildenafil for the treatment of erectile dysfunction.

Section 27(3)(a) of the Patent Act provides:

“The specification of an invention must correctly and fully describe the invention and its operation or use as contemplated by the inventor”.

The lower courts took the position that each claim in a patent is a separate invention, and thus the disclosure requirements are to be construed with respect to each individual claim separately in relation to the specification, and not to the specification as a whole.  As such, with respect to claim 7, the lower courts stated that even though the specification did not specifically disclose that sildenafil may be used to treat erectile dysfunction and the compound in claim 7 was sildenafil; since claim 7 disclosed sildenafil and the disclosure stated that sildenafil is one of the nine “especially preferred compounds” in treating erectile dysfunction, such a disclosure is sufficient.

The SCC rejected the lower courts’ interpretation of s. 27(3), and stated that:

“The Act requires that the court consider the specification as a whole, which includes the claims and the disclosure, from the perspective of a person skilled in the art to determine whether the patent meets the disclosure requirements.  Only where the specification as a whole shows that each claim in a patent application concerns a separate invention will the consideration of the disclosure requirements be limited to a single claim”.

Accordingly, the SCC evaluated whether the specification as a whole sufficiently disclosed the fact that sildenafil was useful for treating erectile dysfunction. The patentee had argued that the specification states that there are “certain especially preferred compounds” that are useful for this purpose and that “one of the especially preferred compounds induces penile erection in impotent males”.  It was argued that those statements, combined with the specific claims for the individual compounds in claims 6 and 7, would have lead a person skilled in the art to conclude that the actually useful compound was the compound claimed in either claim 6 and 7.  Thus, with minor testing, a person skilled in the art would find that sildenafil was the effective compound.

The SCC decided that this extent of disclosure was insufficient.  In fact, the Court suggests that the patentee may be trying to “game” the system by avoiding explicitly identifying the compound that was actually found to be effective.  Accordingly, because the specification of the ‘446 Patent does not indicate that sildenafil is the compound that works to treat erectile dysfunction, that the compound that works to treat erectile dysfunction is found in claim 7, or that the remaining compounds in the ‘446 Patent have not been found to be effective in treating erectile dysfunction, the Court found the ‘446 Patent invalid for failure to meet the disclosure requirements of s. 27(3) of the Act.