Effect of Errors in Priority Application

Amgen Inc v Pfizer Canada ULC 2020 FC 522 Southcott J
            1,341,537 / filgrastim / NEUPOGEN / NIVESTYM

Yesterday’s post gave an overview of the facts and discussed the main substantive holding in this decision, namely that the invention was obvious. This post turns to two priority issues: the effect of errors in the priority application; and disclosure of data in the priority application.

The 537 patent claimed priority from a prior US application — the 959 application — and there was a significant debate as to whether priority could properly be claimed. It is unusual to see this issue discussed at length in Canadian cases (here’s the only other case I’ve seen since this blog started), so the decision on this point is interesting for that reason alone. Because the 537 patent is governed by the old Act, the question was whether the prior application was for “the same invention” [186]. Under the new Act, s 28.1(1)(a)(i), the question is whether the prior application “disclos[es] the subject-matter defined by the claim.” Because of the different wording, it is not entirely clear that Southcott J’s analysis would apply under the new Act, but his analysis did not turn on the precise wording, so it may well provide useful guidance.

Errors in priority application
As discussed in yesterday’s post, the invention relates to filgrastim, which is a recombinant DNA version of the naturally occurring “granulocyte colony-stimulating factor” or “G-CSF” [12]. The 959 priority application listed (i) the amino acids sequence of the naturally occurring G-CSF; (ii) the corresponding DNA codons; (iii) the corresponding cDNA. There were admittedly typographical errors in all three sequences [198]. These errors had been corrected in the application as filed. The parties did not identify any jurisprudential guidance on the issue of whether such errors implied that the priority application does not disclose “the same invention” [198]. Relying on the principle that the skilled person reads the invention with a mind willing to understand [204], Southcott J held that the skilled person would be capable of “resolving” the errors [202], would not be “stymied” [204] and would not conclude that the two applications “are in substance directed to different inventions” [203]. On the facts, this conclusion strikes me as sound for the reasons given by Southcott J.

More broadly, Southcott J’s holding means that the mere presence of errors in the priority application does not preclude claiming priority from it. However, he did not purport to set out a specific test. On the facts, it seems that the errors were relatively easily corrected [199]-[200], so his decision would be consistent with a rule that a skilled person must be able to correct the errors without undue effort. But his decision is also consistent with a more relaxed rule; given that the errors could be readily resolved, it was not necessary for Southcott J to address the question of whether misleading errors would preclude a priority claim.

I would suggest that the case law on prior disclosure for purposes of anticipation might be relevant. Under the current Act, the test for claiming priority is whether the priority application “disclos[es] the subject-matter defined by the claim,” while the test for anticipation under 28.2 (1) is whether “[t]he subject-matter defined by a claim” has been “disclosed.” The similarity in text of the provisions suggests that the applicable test for “disclosure” might be the same (subject to purposive considerations to the contrary). The leading case on disclosure for the purposes of anticipation is Sanofi 2008 SCC 61, which adopted the two part “enabling disclosure” test set out in Synthon [2005] UKHL 59. In Synthon the question was whether Smithkline Beecham's (SB) patent, claiming a particular polymorph pf paroxetine methanesulfonate ("PMS") [8], was anticipated by Synthon's prior application which also described how to make PMS [4]. However, the disclosure in the prior application was quite misleading: “A person skilled in the art, reading both documents, would think that they identified different polymorphs” [9]. The House of Lords nonetheless held that the disclosure requirement was satisfied. If the same “disclosure” test applies to claiming priority, this suggests that priority might properly be claimed even if the errors in the priority document were misleading, so long as it “disclos[es] the subject-matter defined by the claim,” in the sense that “disclosure” is used in Sanofi and Synthon. This also seems reasonable on policy grounds. Otherwise, in a case like Synthon, where Synthon's prior application anticipated SB's patent notwithstanding the errors, it would seem that Synthon should be able to claim priority for its own subsequent filing based on that prior application, notwithstanding the errors. Were that not the case, SB's patent would be anticipated by Synthon's prior application, and Synthon's filing would be anticipated by SB's patent, and neither party would be able to obtain a patent for lack of novelty, even though it was uncontested that the compound itself was new. (I say "in a case like Synthon," because this scenario did not arise on the facts, as Synthon's prior application was a PCT application.)

Disclosure of data
A second point of interest relates to disclosure of data in the priority document. It was agreed that one of the claims, Claim 47, included a requirement for biological activity (in particular, granulocyte colony-stimulating activity). The parties seemed to have proceeded on the assumption that this meant that in order to disclose the same invention, the priority application had to disclose tests establishing the biological activity. While the tests disclosed in the priority application were not the same as those disclosed in 537 patent, Southcott J held that the tests disclosed in the priority application adequately established the biological activity; the same tests do not have to be disclosed, so long as the same activity is disclosed [211]. That holding seems right to me, so far as it goes.

While that disposed of the point on the facts, I’d question the assumption that it was necessary for the tests establishing the activity to be disclosed in the priority application at all, even though the claim includes a requirement for biological activity. While an invention must be useful, if utility can be demonstrated, the data establishing that utility need not be disclosed in the patent itself. If the data need not be disclosed in the patent, it is difficult to see why it must be disclosed in the priority application. So, suppose that granulocyte colony-stimulating activity had been demonstrated before either the priority date or the filing date, but the 537 patent itself did not disclose any data supporting utility. Aside from any priority issues, Claim 47 would nonetheless be valid, because it is not necessary to disclose evidence of demonstrated utility in the patent itself. Now suppose the disclosure in the priority application was exactly the same as that in the 537 patent, which is to say that neither of them disclosed any data. It would seem that if the disclosure in the priority application is exactly the same as in the Canadian patent, the same invention / same subject matter requirement must be satisfied. So, if biological activity is demonstrated, the Canadian application can properly claim priority from the priority application, even if neither the priority application nor the Canadian application discloses the data. This suggests that if the Canadian application disclosed the data, but the priority application did not, the Canadian application should still be able to claim priority; it doesn’t seem reasonable that the Canadian applicant should be a worse position because of having disclosed more information.