Canada’s Intellectual Property Firm

Federal Court upholds validity of one pneumococcal vaccine patent, but holds two other patents invalid

Authored byLei Liu

Update: Wyeth’s appeal was discontinued.

On April 30, 2021, the Federal Court issued its decision relating to the validity of three patents relating to Pfizer’s PREVNAR 13, a 13-valent pneumococcal polysaccharide protein conjugate vaccine: Merck v Wyeth, 2021 FC 317. Merck sought to impeach Wyeth’s Canadian Patent Nos. 2,604,363 (363 Patent), 2,650,056(056 Patent) and 2,803,111 (111 Patent) on the basis that Merck believed that Wyeth (now Pfizer) would assert the patents against Merck’s 15-valent pneumococcal polysaccharide protein conjugate vaccine, V114. Merck filed a New Drug Submission for V114 during trial. The Court upheld the validity of the 363 Patent (though construed the claims to be limited to the specified 13 serotypes), but declared the 056 and 111 Patents invalid.


This article focuses on the 363 Patent, which relates to multivalent immunogenic compositions, as well as uses thereof and processes for making the compositions. In upholding the validity of the 363 patent, the Court examined issues of claim construction, anticipation, and obviousness.

The technology

Streptococcus pneumoniae (also referred to as S. pneumoniae) causes many pneumococcal infections and is classified into different serotypes depending on the polysaccharide that encapsulates the bacteria. More than 90 serotypes of S. pneumoniae were known before the development of PREVNAR 13.

Polysaccharide-only pneumococcal vaccines were not very immunogenic in children under the age of two. It was known before the development of PREVNAR 13 that by conjugating polysaccharides to carrier proteins, the immune response to the polysaccharide could be enhanced.

In 2000, PREVNAR 7, covering 7 serotypes, became the first approved protein conjugate vaccine in the world. While there were attempts to develop 11-valent pneumococcal polysaccharide protein conjugate vaccines, no such products were approved before PREVNAR 13.

Claim construction

Claim 1 of the 363 Patent recites “[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.” (emphasis added).

The Court concluded that Claim 1 of the 363 Patent is limited to the 13 serotypes of S. pneumonia recited in the claim. In so doing, the Court rejected Wyeth’s argument that the 363 Patent describes a “platform” technology and the skilled person would have used the platform to add other serotypes in a future vaccine. The Court reasoned that “even if the word ‘comprising’ used in claim language could be regarded as open-ended, the inclusion of other elements requires some justification. The basis for such an inclusion must be found within the confines of the patent.”

While the Court found the 363 Patent contained sufficient bases for adjuvants, buffers and other excipients that may be further comprised in the claimed immunogenic composition, there was no such basis to go beyond the 13 serotypes. The Court commented that notwithstanding that other serotypes were known in the art, the 363 Patent did not mention a need, a desire, or a basis for adding any other serotype.

The Court also found it difficult to accept Wyeth’s construction that more than 13 serotypes are within the claim scope as it is not clear how to choose a cap on the number of serotypes covered. Without a cap, the Court reasoned that “the ambit of Wyeth’s monopoly could grow over the life of the 363 Patent as new serotypes – or their structure – are discovered. This would be contrary to the fundamental principles of claims construction.”

In light of the construction limiting the 363 Patent claims to the specified 13 serotypes rather than a “platform” for making a vaccine with greater coverage, the Court did not address Merck’s assertions of overbreadth and inutility.


The Court concluded that Claim 1 of the 363 Patent is novel. While a 2004 publication discloses the same 13 serotypes recited in Claim 1, it is silent on the carrier protein used to conjugate the different serotypes and is also silent on the immunogenicity of the 13-valent vaccine. The Court ruled that Merck had not met its burden to prove that the skilled person would have inferred from this publication that all 13 serotypes of the 13-valent vaccine had to be individually conjugated with the claimed single carrier protein, or that 13 serotypes all conjugated with the carrier protein would be immunogenic.

The Court further held that even if the elements were disclosed, the 2004 publication would not have enabled the skilled person to make the invention without undue burden.


The Court concluded that the claims of the 363 Patent are not obvious.

Merck and Wyeth agreed that the inventive concept of the claims including claim 1 is a multivalent immunogenic conjugate composition containing polysaccharides with 13 specified pneumococcal serotypes, each individually conjugated with a unique carrier protein, and potentially containing adjuvants.

The Court was not convinced that the skilled person would have expected that a 13-valent protein conjugate vaccine would be immunogenic. The Court also found that the evidence shows that conjugating is a complex endeavour and that the increasing reports on immune interference could have deterred the skilled person to pursue a 13-valent protein conjugate vaccine all conjugated with the specified carrier protein.

In considering whether the invention of the 363 Patent was “obvious to try,” the Court held that the skilled person would not have achieved the invention without prolonged and arduous experimentation.

The formulation patents

The 056 Patent and the 111 Patent relate to formulations of immunogenic compositions. The Court held both invalid for obviousness, and certain claims were held invalid for obviousness type double-patenting over the 363 Patent.

Wyeth may appeal to the Federal Court of Appeal as of right.

Should you have any questions, please do not hesitate to contact a member of the Pharmaceutical Litigation Group.

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