In Re Immunex Corporation Patent Application No. 583,988, (2011) 89 C.P.R. (4th) 34, the Patent Appeal Board held that broad claims to monoclonal antibodies are allowable in the absence of a working example when the antigen is a novel polypeptide that has been fully characterized, for example, by its complete amino acid sequence. This decision brings Canada in line with other jurisdictions, such as the US and UK, in this regard.

Immunex’s patent application was filed on November 24, 1988, with claims directed to monoclonal antibodies immunoreactive with IL-1R polypeptides, as well as antibodies claimed in a product-by-process format. The antibody claims were originally rejected by the patent examiner because such an antibody had not been produced by the filing date. The main issue was whether these claims were sufficiently supported by the description. In addressing this issue, the Board considered whether the claims were enabled, adequately described and had utility.


The Board found that there were two types of IL-1 receptors, Type I and Type II, which were antigenically different. However, the description in the application was only directed to a Type I receptor. Thus, the monoclonal antibody claims to any IL-1R polypeptide was not enabled across its scope since the task of isolating a Type II receptor for use as an immunogen would have been an undue burden. Fortunately for Immunex, the Board was also of the opinion that the antibody claims could be enabled if they were appropriately limited to Type I IL-1R polypeptides and invited Immunex to make the necessary amendments to limit the claims to an antibody that binds to a Type I receptor.

Submission of post-filing data to support that the description was enabling at the time of filing is typically rejected. However, the Board was willing to accept that post-filing data may provide an indication that the description was enabling, at least with respect to anti-Type I IL-1R monoclonal antibodies, as these antibodies were produced without requiring undue burden by following a protocol very similar to the one described in the application. Accordingly, applicants should include prophetic examples in the description when claiming monoclonal antibodies.

Adequate Description

Prior to Immunex, patent examiners were instructed to reject claims to a monoclonal antibody for lacking a sufficient description unless the applicant had prepared a working example at the time of filing or provided an explicit description of the epitope to which the monoclonal antibody binds, for example, in terms of a binding pocket defined by specific non-contiguous amino acids. In Immunex, the Board held that the novel Type I IL-1 receptor was adequately described by the provision of a DNA sequence encoding such a receptor. However, a working example may still factor into whether the written description is sufficient in cases where the antigen is complex or where the antigen, although novel, may be cross-reactive because it possesses an epitope common to a known antigen. The Board also held that claims reciting therapeutic or diagnostic antibodies or claims reciting antibodies with special attributes would require correspondingly detailed support.


In Consolboard Inc. v. MacMillan Bloedel (Saskatchewan) Ltd., [1981] 1 S.C.R. 504, the Supreme Court held that the utility of the claimed product need not be mentioned in the description or the claims if it would have been apparent to a skilled person. In Immunex, the Board held that it would have been apparent that an anti-Type I IL-1 receptor monoclonal antibody would at least be useful in assays for immunopurification of IL-1 receptor polypeptides.