The Role of the Inventive Concept in an Obvious to Try Analysis

Eli Lilly Canada Inc v Apotex Inc 2023 FCA 125 Rivoalen JA: de Montigny, Gleason JJA affg 2020 FC 816 St-Louis J

2,371,684 / tadalafil / CIALIS ADCIRCA / FC Selection / FC Anticipation

This case is ultimately a straightforward example of the asserted claims being invalid on an obvious-to-try analysis, but because of the way it was argued it also sheds some light on the role of the inventive concept in the obviousness analysis.

The asserted claims of the 684 patent are to dosage forms of tadalafil for treating ED, namely doses from 1 to about 20 mg, as well as specific doses within that range, including 2.5, 5, 10 and 20 mg doses [FC 197-213]. The question in this case was whether the 684 patent is valid over the prior art 2,226,784 patent, which claims tadalafil for the treatment of ED, and disclosed a dose range from 0.2 to 400 mg [12]. At trial, St-Louis J held on the facts that starting from the knowledge that doses from .02 to 400 mg were useful, it would be routine for the skilled team to carry out the trials necessary to narrow that down to the range providing the best balance between efficacy, and safety and tolerability, and they would be motivated to do so [FC 325–28]. The claimed invention was therefore obvious to try [FC 323, 330]. The FCA has now affirmed on that basis [65]–[80].

Lilly’s challenge on appeal was to find a question of law to attack in St-Louis J’s essentially factual finding. Lilly argued that St-Louis J had erred in her construction of the inventive concept, a question of law [48] arising at step 3 of the Windsurfing test for obviousness, which was adopted in Sanofi 2008 SCC 61 [67]. Lilly waffled in its argument as to what constituted the specific inventive concept, before settling on the position that the inventive concept is that the claimed dose remains effective in treating ED, with a reduced flushing side-effect as compared to larger doses of tadalafil [20]–[27], [61]. (As an aside, getting an extra four years of exclusivity on a popular drug on the basis of reduced flushing would be grist for the mill for critics of evergreening practices. From a PR perspective, it is probably a good thing for Lilly that this patent was invalidated.)

There has been a debate as to the role of inventive concept in assessing obviousness, which came to the fore in Shire 2021 FCA 52. One central issue is whether the inventive concept is the “end point” of the obviousness inquiry (Shire [65]), or is rather a “distraction” that can be avoided if it is unhelpful Ciba 2017 FCA 225 [76]–[77]: see here. Rivoalen JA held that in this case, it did not matter whether Lilly was right as to the nature of the inventive concept; the claims were invalid for obviousness in any event [49].

As noted, St-Louis J used an obvious-to-try analysis, which was endorsed by Rivoalen JA [65]. (So far as I can tell, Lilly did not dispute that the obvious-to-try test was appropriate.) St-Louis J found that carrying out a drug dosing study is typically done in Phase II clinical trials, and it is normally routine work [FC 325]. Such studies aim to identify the dosage that provides the best balance of efficacy, safety and tolerability [69]. In reviewing the factors relevant to an obvious-to-try analysis, Rivoalen JA pointed out that the reduced flushing that was eventually identified as an advantage of the optimal dose does not change the aim of identifying the dose range that offers the best balance [72]. Further, on the facts that the dosing study in this case was routine; again, this conclusion is not affected by the fact that reduced flushing turned out to be one of the advantages of the optimal dose [73]–[77]. After carrying out this routine dosing study, the skilled person would be motivated to identify and commercialize the optimal dose [79]. Consequently, the claimed dosage range was obvious [80].

To summarize, there was nothing inventive about carrying out the dosing study and identifying the optimal dose—and that conclusion does not depend on the precise properties of the final dose. While minimizing the flushing side effect was one goal of the dosing study, it is possible that the optimal dose would not have reduced flushing significantly; while flushing was a side effect of interest, it is a relatively minor side-effect, certainly compared to other side-effects such as passing out from low blood pressure. So, before carrying out the trials, the skilled person might not have predicted that the optimal dose would have reduced flushing. Nonetheless, there was nothing inventive about the dosing studies, even though not all the specific properties of the optimal dose could not have been predicted ex ante. This is really the whole point of the obvious-to-try analysis: when something is obvious to try (finding the optimal dose) and the trials themselves are routine, the resulting product is obvious, even if not all of its properties could have been predicted in advance.

In other words, apart from the distraction of the inventive concept debate, this was a perfectly ordinary application of the obvious-to-try test, and the patent was invalidated on that basis both at trial and on appeal.

What does this tell us about the role of the inventive concept? Rivoalen JA was very explicit that she was accepting Lilly’s construction of the inventive concept only for the sake of argument, and her conclusion did not turn on whether that was the true inventive concept [49], [61]. On its face, this implies that it is not always necessary to identify the inventive concept in order to assess obviousness.

But there is also a debate as to how to define the inventive concept. In this case, Lilly seemed to be using it to mean new information that was disclosed in the patent and embodied in the claimed subject-matter. But the inventive concept has also been equated to “the solution taught by the patent” (Bristol-Myers 2017 FCA 76 [65]). In a previous post, I argued that the focus on the obviousness inquiry should be on whether the subject-matter defined by the claim is the solution to the objective problem that would have faced the skilled person. This is consistent with Rivoalen JA’s analysis in this case. In a dosage study, the problem is to find the dose that best balances efficacy against side-effects. In this case, the solution to that problem was a dose from 1 to about 20 mg. On the facts, that solution was obvious on an obvious-to-try analysis.

So perhaps the underlying issue is how to define the inventive concept. If we define it as the solution to the objective problem, then perhaps it is the proper focus of the obviousness inquiry; that view is at least consistent with the result and analysis in this case. On that view, the real lesson of this case is that if we are going to use the inventive concept as part of the obviousness analysis, we cannot allow the patentee free rein in defining it.

Finally, St-Louis J had also held that that the 684 patent was anticipated by the prior art 784, and she had an extended discussion of whether the 684 patent was a selection patent, evidently on the view that this had important consequences for validity. I had criticized her analysis of both these points: see here and here. In light of her holding that the patent was invalid for obviousness, Rivoalen JA found it unnecessary to address these issues; she added that “[t]hese reasons, however, should not be viewed as endorsing the Judge’s findings or reasons in respect of these issues” [82].