Patents and Prior Art: Federal Court Clarifies Standards for Anticipation and Obviousness

The Federal Court’s recent decision in Alexion Pharmaceuticals, Inc. v. Amgen Canada Inc. (2025 FC 754) offers important guidance on the use of prior art for anticipation arguments in patent validity.

This patent infringement case relates to Canadian Patent No. 2,645,810 (810 Patent), which is associated with biologic drug eculizumab. Eculizumab, a recombinant humanized monoclonal antibody, is currently the only approved treatment in Canada for paroxysmal nocturnal hemoglobinuria – a rare disease that causes the premature destruction of red blood cells.

Background

Alexion Pharmaceuticals, Inc. (Alexion), the patent holder, brought patent infringement actions under section 6(1) of the Patented Medicines (Notice of Compliance) Regulations alleging that Amgen Canada Inc.’s (Amgen) proposed biosimilar would infringe the 810 Patent. Amgen admitted infringement but argued the claims at issue were invalid on the grounds of anticipation and obviousness. The arguments were focused on claims 1 and 2 of the 810 Patent (Asserted Claims), and the court’s analysis was limited to claim 1.

Limit on Prior Art Used in Anticipation

Novelty is a requirement for patentability under subsection 28.2 of the Patent Act, which requires that the subject matter of a claim must not have been previously disclosed.

In considering anticipation, Justice Furlanetto’s analysis focused on the first part of the two-part test from Apotex Inc. v. Sanofi-Synthelabo Canada Inc. (2008 SCC 61) (Sanofi): 1) prior disclosure and 2) enablement.

Prior disclosure must have clear direction so that a skilled person would in every case and without possibility of error be led to the claimed invention. A skilled person is deemed unimaginative and uninventive but, at the same time, has an ordinary level of competence and knowledge incidental to the field of the patent and is reasonably diligent in keeping up with advances. It is not suggested that the exact invention be publicly disclosed, however, it should be that if the prior disclosure’s subject matter were carried out, infringement of the patent would result (Sanofi at paras 23, 25). Moreover, the prior disclosure must be contained in a single reference which provides the skilled person with all of the information necessary to produce the invention.

Amgen argued that the Asserted Claims were anticipated by U.S. Patent Application Publication No. 2003/023972 (US972) – which describes an antibody preparation (5G1.1 + peptide). While US972 discloses amino acid sequences resembling those in the 810 Patent, it omits a critical component – CDR3 of the heavy chain. US972 refers generally to another patent, U.S. Patent No. 6,355,245 (US245), for the construction of 5G1.1, using “incorporation by reference” language without specifying a paragraph or section or even use of the CDR3 heavy chain.

Amgen argued that a skilled person could derive the missing sequence from US245 and reconstruct the claimed antibody, essentially asking the court to incorporate one prior art document into another. It was Alexion’s position that US972 alone does not disclose the invention with the necessary clarity or completeness, and that US245 merely describes a murine antibody unrelated to eculizumab. Since US972 does not provide the full antibody sequence of eculizumab itself, Alexion argued the Asserted Claims of the 810 Patent were not disclosed and therefore were not anticipated.

Incorporation by Reference

The court considered whether US972 disclosed enough information by incorporating US245 to lead a skilled person to the construction of eculizumab.

As described in the case law, Justice Furlanetto reiterated that one must be able to look to a single publication to find all the information necessary to produce the invention without inventive skill. This single prior publication must contain clear direction as to lead the skilled person to the invention in every instance without chance for error. While incorporation by reference is a recognized legal concept, the court emphasized that for anticipation to succeed, a single prior art document or a clearly incorporated document must provide sufficient direction. Here, the court determined that a skilled person would need to engage in a complex process akin to reverse engineering to reveal eculizumab’s sequence, which goes beyond the passive reading required for anticipation. The use of multiple documents and interpretive steps did not meet the high standard set in Sanofi for clear disclosure. Therefore, the Asserted Claims were not anticipated.

Obviousness

Given the disclosures in US972 and US245, a reader may expect that the defendant would be successful invalidating the 810 Patent on obviousness. Interestingly, that was not the case here.

Section 28.3 of the Patent Act recognizes that the subject matter of a claim in a patent application cannot have been obvious on the claim date to a skilled person having regard to the state of the art. A high threshold is associated with obviousness which requires that the skilled person would have come directly to the invention without hindsight playing a role. It is necessary to consider whether the state of the art and the inventive concept could have been pieced together without inventiveness, through only their common general knowledge (CGK). Obviousness was evaluated by the court under the four-step framework established by the Supreme Court of Canada in Sanofi (para 67).

Amgen argued that no differences exist between the state of the prior art available and the inventive concept. Based on this argument, the court will consider if the skilled person would have in fact combined these references and, if so, whether they would have arrived at the claimed invention without inventiveness. While it is possible to mosaic prior art references not part of CGK, the party alleging obviousness must establish that the skilled person would have been motivated to combine those references.

Interestingly, Justice Furlanetto concluded that the inventive concept of the Asserted Claims could not be arrived at without significant gaps being filled. For instance, the skilled person would not have linked US972 and US245 in the manner Amgen proposed without employing a degree of creativity or hindsight.

Ultimately, the court held that Amgen failed to establish that claims 1 and 2 of the 810 Patent were invalid for either anticipation or obviousness.

Takeaways

This decision reinforces the high evidentiary threshold necessary to invalidate patent claims for anticipation and obviousness. Notably, anticipation requires that a skilled person be led directly and unequivocally to the claimed invention by a single prior reference. There may be a fact situation that could support an incorporation by reference; this case did not. This case provides detailed guidance for both those challenging patents and for patentees navigating biosimilar litigation in Canada.

Please contact the authors or a member of the Intellectual Property Group at Aird & Berlis LLP if you have any questions or require assistance in regard to patent claims.