In November 2012, the Supreme Court of Canada unanimously voided1 Pfizer's patent for Viagra2, to the consternation of the pharmaceutical industry. Much of the commentary at the time revolved around the Court's finding that sildenafil (marketed as ViagraTM) was the only compound that was effective as claimed, out of an enormous number of possibilities. As such, the Court held that proper disclosure is a crucial element of the bargain between a patentee and the public and that Pfizer had failed to uphold its end of the bargain.
But was this indeed the case? Could the outcome have been different? And where does this leave prospective patentees in Canada now?
By way of background, Pfizer's patent for ViagraTM disclosed a new use for a class of compounds for the treatment of erectile dysfunction. The broadest claim, claim 1, was directed to the use of a compound of formula (I), which was calculated to encompass roughly 260 quintillion possible compounds. Subsequent claims cascaded down to successively smaller ranges, with claims 6 and 7 each reciting a single compound, one of which was sildenafil (claim 7).
Based on evidence presented at the hearing3, the Court characterized the invention as the use of sildenafil for treating erectile dysfunction, because Pfizer's tests indicated that only sildenafil was effective in treating erectile dysfunction while none of the other compounds had been shown to be effective in doing so. Given this characterization, the Court found that the invention was insufficiently disclosed, rendering the skilled reader unable to practice the invention.
The Court however recognized the practice of drafting cascading claims, noting that the useful claim will usually be the one at the end concerning an individual compound. The Court's decision therefore appears to hinge on the finding that two individual compounds were claimed, and only one was effective, thus obscuring the true invention and denying the public its right to proper disclosure. This begs the question of whether the outcome would have been different if only one individual compound, sildenafil, had been claimed.
Alternatively, the decision suggests that the invention would have been properly disclosed if both individually-claimed compounds had been effective in treating erectile dysfunction. Subsequent courts seem to have adopted this
interpretation. For example, a patent that disclosed a class of compounds for treating inflammation, and contained cascading claims ending in three individually-claimed compounds, was upheld on the basis that the skilled reader was not misled by there being a number of compounds that appeared to be interesting, because all individually-claimed compounds worked4. Similarly, a patent that included a group of six individually-claimed compounds for treating tumors through selective inhibitory activity was upheld on the basis that all six compounds exhibited selective inhibition and there was no attempt to hide the best inhibitor candidate5.
Pfizer might therefore have prevailed if sildenafil had been the only individual compound claimed, or if it could have been determined that the compound of claim6 also worked as claimed6, had not the specification stated that "certain especially preferred compounds" were tested and "one" of these compounds was effective. The Court interpreted these statements as requiring further research to determine which of the two individually-claimed compounds was useful, taking a dim view of what it considered to be Pfizer's attempts to "game" the system. Prospective patentees would be well served to take these decisions into consideration when pursuing patent protection in Canada.
Originally published in LifeSigns - Life Sciences Legal Trends in Canada
Footnotes
1 The Supreme Court revised its earlier order on June 4, 2013, removing the statements indicating that the patent is invalid and void, and stating that Teva had established that its allegations, that the patent is not valid, were justified under the relevant statutory regulations.
2 Teva Canada Ltd. v. Pfizer Canada Inc., 2012 SCC 60
3 Pfizer Canada Inc. v. Novopharm Ltd., 2009 FC 638
4 Pfizer Canada Inc. v. Apotex Inc., 2014 FC 314
5 Teva Canada Ltd. v. Novartis AG, 2013 FC 141
6 This appears to have been the case since, shortly after the decision on ViagraTM, Pfizer adduced evidence that the compound of claim 6 was in fact tested before the Canadian filing date and found to be useful for treating erectile dysfunction (Pfizer Ireland Pharmaceuticals v. Apotex Inc., 2014 FCA 13)
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