“Comprising” in Claim Construction & Application of the “Obvious to Try” Test: Key Takeaways from the Federal Court’s decision in Merck et al. v Wyeth LLC

June 1, 2021
By Melanie Szweras, Scott MacKendrick and Nicole LaBerge

In the recent Federal Court decision in Merck Sharp & Dohme Corp and Merck Canada Inc v Wyeth LLC (2021 FC 317), Associate Chief Justice Gagné provides important guidance on the meaning of the term “comprising”, as well as further clarification of the “obvious to try” test for obviousness. Justice Gagné’s reasons also speak to the drafting of patent applications that deal with compositions of matter, in particular, vaccines.  

An action to impeach three patents pertaining to PREVNAR®13

Merck Canada Inc. and Merck Sharp & Dohme Corp. (Merck) sought to impeach three Canadian patents, one composition patent 2,604,363 (the 363 Patent) and two formulation patents 2,650,056 (the 056 Patent) and 2,803,111 (the 111 Patent), belonging to Wyeth LLC (Wyeth). The patents pertain to a 13-valent pneumococcal polysaccharide protein conjugate vaccine commercialized under the name PREVNAR®13. PREVNAR®13 is a polysaccharide protein conjugate (PCV) vaccine directed towards Streptocococcus pneumoniae (S. pneumoniae), a bacteria that causes many pneumococcal infections such as meningitis, pneumonia, and bacteraemia, as well as other milder infections. Merck alleged Wyeth’s patents lacked inventiveness.

An open-ended claim construction of “comprising” must be justified

The central claim at issue was claim 1 of the 363 Patent. The claim, reproduced below, relates to a multivalent immunogenic composition having polysaccharide-protein conjugates. Merck argued that the claim was limited to exactly 13 serotypes, while Wyeth contended the claim covered 13 or more serotypes. Each serotype is directed towards a distinct species of S. pneumoniae.

Claim 1 of the 363 Patent:

A multivalent immunogenic composition, comprising 13 distinct polysaccharide-protein conjugates, together with a physiologically acceptable vehicle, wherein each of the conjugates comprises a capsular polysaccharide from a different serotype of Streptococcus pneumonia conjugated to a carrier protein, and the capsular polysaccharides are prepared from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F, wherein the carrier protein is CRM197.

Ultimately, Justice Gagné agreed with Merck’s construction of the term “comprising”, finding that the claim was directed to exactly 13 serotypes. Justice Gagné rejected Wyeth’s argument that claim 1 disclosed a “platform” for making a vaccine with greater coverage. Relying on the Federal Court of Appeal decision in Purdue Pharma v Canada (Attorney General)1, Justice Gagné held that even if the word “comprising” when used in claim language could be regarded as open-ended, the inclusion of other elements requires some justification to be found within the patent.

While Justice Gagné held that when one reads the patent as a whole, one finds sufficient bases for adding adjuvants, buffers and other excipients, there was no basis to go beyond 13 serotypes. Moreover, the summary of the invention describes the invention as providing a 13-valent pneumococcal conjugate composition comprising the seven serotypes contained in PREVNAR 7 in addition to six additional serotypes. The detailed description provides a rationale for the inclusion of the original seven serotypes as well as the additional six serotypes. Further, all sixteen examples provided refer only to the specific 13 serotypes recited in the claims.

Prolonged and arduous experimentation carries weight in “Obvious to Try” Analysis

Having determined the 363 Patent was limited to only 13 serotypes, Justice Gagné next considered the patent’s validity. It was found to be novel, as no prior art disclosed and enabled the invention. On obviousness, Justice Gagné found Merck satisfied the first and third branches of the “obvious to try” test outlined in Apotex Inc. v Sanofi-Synthelabo Canada Inc.2 Evidence showed that what would be tried ought to work and the prior art provided a motive to find the solution that the patent addresses. Despite satisfying these two branches of the test, Justice Gagné held that the person skilled in the art would not have arrived at the invention without prolonged and arduous experimentation. This was supported by the fact that development of PREVNAR®13 took many years. The complexity of factors relating to development of the conjugate process, such as the structure of the polysaccharide, the length of the polysaccharide chain, use of linker, the carrier protein, the ratio of polysaccharide protein, how the polysaccharide is activated and conjugated to the carrier protein, and the conditions of conjugation (pH, temperature, time, reactants, etc.) further supported this. In finding this, Justice Gagné affirms that the second prong of the “obvious to try” test in Sanofi can be just as important a factor as the considerations of “ought to work” and “motive to try”. This finding also builds on the recent Federal Court of Appeal decision in Janssen et al. v The Minister of Health (2021 FCA 45)(read our article here), where the court stated that “more or less self-evident that what is being tried ought to work” is just one factor in the “obvious to try” test. Even where it is more or less self-evident that what is being tried ought to work, an invention can still be found not obvious to try.

Formulation patents invalid for obviousness

The other two contested patents (the 056 Patent and the 111 Patent), relating to formulations that stabilize and inhibit precipitation on immunogenic compositions, were found invalid for obviousness. Justice Gagné held there was nothing inventive about trying a surfactant to see if it would work in a polysaccharide-protein conjugate formulation. Further, the 13-valent claims of the 111 Patent were held invalid for obviousness-type double patenting as they were deemed to be obvious variants of the invention claimed in the 363 Patent.

Patent Drafting Practice Points

This decision serves to remind patent applicants that use of the term “comprising” in claims will not be construed open-endedly in all cases. There must be justification in the patent to arrive at an open-ended construction. Where an exact number is provided in a claim, drafters should be careful not to unnecessarily restrict the intended claimed subject-matter. In the present situation, if the patentee had wanted to protect a platform for vaccines, the claim should have included language such as “at least 13 serotypes” to make clear that more serotypes were possible, but that at least those 13 were required to be present.

1 2011 FCA 132 at para 22.

2 2008 SCC 61 at para 69 [Sanofi].

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