Friday, March 22, 2013

Claim to Single Compound Distinguishes Sildenafil

Novartis Pharmaceuticals Canada Inc v Teva Canada Ltd / zoledronate (NOC) 2013 FC 283 Hughes J
            ZOMETA ACLASTA / zoledronate / 1,338,895, 1,338,937

The insufficiency at issue in Sildenafil 2012 SCC 60 is very different from the traditional how-to-make insufficiency, and it is convenient to give them different names. For now, at least, I will refer to “Sildenafil insufficiency” and “classical insufficiency” by analogy with “Biogen insufficiency” (overbreadth) and “classical insufficiency” in UK law.

Sildenafil insufficiency was raised in respect of the ‘937 patent. (For an overview the facts, see yesterday’s post.) While the patent claims zoledronate specifically, zoledronate is not singled out in the disclosure. The disclosure of the ‘937 patent begins by stating that it relates to a class of compounds with the following structure (formula I):

From pages 5-7 the patent lists compounds of formula I to which the invention “relates” or “relates more particularly” or “preferably relates” or “relates firsts and foremost,” but these are all classes of compounds. Zoledronate does fall within the class, but it is not specifically named [69]. The invention is also said to “relate[] specifically to the compounds of formula I and the salts thereof, especially the inner salts and pharmaceutically acceptable salts thereof with bases mentioned in the Examples” [70]. There are about thirty-two compounds specifically named in the twenty examples, and zoledronate appears in two examples. The examples are all examples of how to make the compounds. Note also that this statement says that the invention relates specifically to salts with bases mentioned in the Example, not to compounds mentioned in the examples. So, even though zoledronate is mentioned in the Examples, it is not being singled out as a particularly efficacious compound; it is the salts which are particularly useful. There is no statement in the disclosure of which compounds have been tested for potency, nor is there any evidence discussed by Hughes J as to which compounds had been tested as of the date of the priority application. Zoledronate itself was made and tested in July 1987, which is after the priority application was filed, but before the Canadian application was filed [107].

From this we see that the ‘937 patent is similar to the patent at issue in Sildenafil, in that “No specific attributes or characteristics are ascribed to [the claimed compound] that would set it apart from the other compounds,” and “the patent itself suggests that the entire class of claimed compounds will be effective” [134, quoting Sildenafil [66-67]]. Hughes J nonetheless held that:

the '937 patent, because it claims only one compound, zoledronate, is, on a case-by-case basis, distinguishable from that considered by the Supreme Court in Teva [138].

This distinction does have a sound basis in the passages from Sildenafil [80] quoted by Hughes J at [136]:

The skilled reader knows that, when a patent contains cascading claims, the useful claim will usually be the one at the end concerning an individual compound. . . . However, the public's right to proper disclosure was denied in this case, since the claims ended with two individually claimed compounds, thereby obscuring the true invention.

The SCC acknowledged that even though the disclosure did not specifically identify the compound of particular interest, the claims are part of the specification, and a skilled person would know that the claimed compounds are normally of particular interest. This implies that claiming individual compounds is tantamount to specifically identifying them in the disclosure. The difficulty in Sildenafil was that two compounds were identified, while only one was truly of interest. In this case, only one compound was claimed, so not even a “minor research project” would be needed to identify the compound of interest.

The distinction between one individual compound claim and two, is nonetheless a fine one. This is not to doubt the validity of the distinction. A line must be drawn somewhere, and as just discussed, there is a sound basis for this distinction both functionally and in Sildenafil itself. It does illustrate once again that the Federal Courts appear not to be inclined to use Sildenafil insufficiency aggressively.

On a slightly different point, while the Sildenafil decision formally turned on “what is the invention,” the "key issue in this appeal" was that "patentees cannot be allowed to 'game' the system" [80] (discussed here). It seems to me that the number of claims is not the only distinction to be drawn between this case and Sildenafil. In Sildenafil only one compound had been tested, while in this case it is not clear to me from the decision how many compounds had been tested. Zoledronate had been tested only after the priority application, and it seems unlikely that the priority application had been filed before any compounds at all had been tested. So I would suspect that as of the Canadian filing date, multiple compounds had been tested and shown to have had at least some efficacy. This means the situation may have been more like Imatinib (here), in which several compounds had been tested but none had emerged as the clear favourite. It would have been interesting to have had a more extensive discussion of the "gaming the system" issue from Hughes J, as was carried out by Snider J in her Imatinib decision (discussed here).

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