In a recent decision, the Supreme Court of Canada has reiterated that an applicant for a patent must not write the patent in such a way that the true invention is obscured and admonished a patentee for not disclosing which of the claimed compound was actually found to work. In addition, the Supreme Court overruled lower court jurisprudence holding that each claim of a patent is to be considered a separate invention.

In Teva Canada Ltd. v. Pfizer Canada Inc., 2012 SCC 60, the patent at issue (the "446 Patent") related to the use of certain compounds for the treatment of erectile dysfunction ("ED"). One of the specific compounds covered was sildenafil, the active compound in Pfizer's Viagra product. The specification of the 446 Patent stated that the invention was the use of a "compound of formula (I)" as a medicament for the treatment of ED. This formula was broad enough to cover 260 quintillion possible compounds (that's 260 followed by 18 zeros!). As is common for chemical patents, the disclosure stated that certain of the compounds within the scope of formula (I) were "especially preferred". The 446 Patent also stated that "one of the especially preferred induces penile erection in impotent males". However, which compound found to do so was not stated anywhere in the patent. Further, the patent did not disclose that the remaining compounds tested had not been found to be effective in treating ED.

At the Federal Court level, Teva challenged the Viagra patent on a number of grounds. On appeal to the Federal Court of Appeal and to the Supreme Court of Canada, Teva limited its attacks to insufficiency – Teva argued that the specification of the patent was insufficient as it did not identify what compound had been found to be biologically active. This attack has its basis in section 27(3) of the Patent Act, which requires that the specification correctly and fully described the invention and its operation or use as contemplated by the inventor and set out clearly the method of using the invention "in such full, clear, concise and exact terms as to enable" a skilled person to use it.

At the trial level, Justice Kelen held that the evidence from both side's experts was that a person reading the disclosure of the patent would not know that sildenafil was the one compound found to work, nor would the person know how the "especially preferred" compounds were selected or how to choose between the extremely large number of compounds in claim 1. While Justice Kelen questioned why the disclosure of the patent did not simply state that the active compound was sildenafil and stated that "the patent plays 'hide and seek' with the reader", he considered himself bound by earlier jurisprudence that each claim of patent must be considered separately in relation to the disclosure. As one claim (claim 7) of the patent did claim the use of sildenafil in treating ED, on the basis of this earlier jurisprudence, he rejected Teva's contention that the disclosure of the 446 Patent was insufficient.

On appeal, the Federal Court of Appeal held that the issue was not whether the patent as a whole was clear, but rather whether it clearly revealed the invention disclosed by claim 7. As that claim set out the chemical formula for sildenafil, the Court of Appeal affirmed the finding of sufficient disclosure. The Court of Appeal agreed with the trial judge that even if the proper test was to take the patent as a whole, a skilled reader would be able to narrow the range of compounds down to the two especially preferred compounds individually claimed in claims 6 and 7. The skilled reader would then conduct tests on those two compounds and determine which of them worked.

Writing for a unanimous court, Justice LeBel overturned the lower courts' decisions, holding that the disclosure of the patent was insufficient. Justice LeBel emphasized that the patent system is based on a bargain – the inventor is granted exclusive rights in a new and useful invention for a limited period in exchange for disclosure of the invention so that society can benefit from this knowledge.

As indicated above, the Federal Court and Federal Court of Appeal held that each claim in the patent is a separate invention and thus sufficiency ought to be considered with respect to each individual claim, not with respect to the specification as a whole. Justice LeBel rejected this approach, stating that any broad proposition that in every case, each claim in a patent application concerns a separate invention would be contrary to the scheme of the Patent Act. Justice LeBel stated that considering the specification as a whole, there is nothing to support the view that the use of sildenafil for the treatment of ED is a separate invention from the use of any of the other claimed compounds for that same purpose. He stated that no specific attributes or characteristics are ascribed to sildenafil that would set it apart from the other compounds. On this basis, the court held that the use of sildenafil and the other compounds for the treatment of ED comprised one inventive concept only.

Justice LeBel referred to several prior Supreme Court of Canada decisions holding that the description of a patent must be such as to enable a person skilled in the art or the field of the invention to produce the invention using only the instructions contained in the disclosure. As set out above, the evidence was that testing would have been required to determine which of the claimed compounds was effective in treating ED. Justice LeBel stated that:

…the public's right to proper disclosure was denied in this case, since the claims ended in two individually claimed compounds, thereby obscuring the true invention. 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.

Justice LeBel concluded by holding that the 446 Patent is void. While in normal patent litigation, this holding would be the clear conclusion, this case arose under the somewhat arcane Patented Medicines (Notice of Compliance) Regulations, which do not provide a final decision on validity. Pfizer has brought a motion in the Supreme Court seeking an order amending the judgment, to provide the normal sort of order in a proceeding under the Regulations. Even if Pfizer succeeds in this motion, it will be a Pyrrhic victory, because in a regular action challenging the validity of the 446 Patent, Justice Zinn of the Federal Court invalidated the patent, stating that the determination of the Supreme Court was on a question of law that is binding on the lower courts. Accordingly, in the case before him, "no result is possible other than a finding that the '446 Patent is invalid".

In its decision, the Supreme Court of Canada has provided a clear direction to patentees that full disclosure is needed to hold up their end of the patent bargain. Further, the starting point now is that the claims of a patent all relate to the same invention and it is up to the patentee to clearly explain the reasons for claims that differ in the scope of protection.