Despite black-letter law that IPRs can only resolve patentability based on prior art patents and printed publications, enablement and written description support can be key issues, particularly in life sciences patents with functional antibody claims. A final written decision in Daiichi Sankyo Company Limited v. Alethia Biotherapeutics, Inc. (IPR2015-00291) found such claims unpatentable after finding that the priority application failed to pass muster from a § 112 standpoint, but that the invention was disclosed in a reference published after the priority document was filed but before the filing of the continuation-in-part that was challenged.

The patent at issue in Daiichi Sankyo claims methods of using an antibody that specifically binds to a protein (Siglec-15) in the treatment of bone diseases such as osteoporosis. Such claims are commonly employed to protect therapeutic antibodies—biological molecules that, when they specifically bind to proteins on cells, stimulate a patient’s immune system to attack those cells and provide a therapeutic effect. These claims are “functional” because the antibody is defined in terms of the protein to which it binds and its effect when administered.

Here, the patent owner did not dispute that a reference, Hiruma, disclosed using an antibody that specifically binds to Siglec-15 in a method of treatment as recited in the challenged claims. The Board accepted that the parent application identified, before Hiruma, the protein Siglec-15 and mentioned developing an antibody that would specifically bind to Siglec-15, using known techniques. However, it was disputed whether that was enough for the challenged claims to be entitled to priority to the parent application. Without the benefit of priority, Hiruma was prior art to the patent under § 102(a), rendering the claims unpatentable.

Thus, the question before the Board was whether the parent application describes and enables antibodies having the desired functional properties. The Board found neither requirement satisfied.

Emphasizing a lack of guidance provided in the specification of the parent application and no actual examples of antibodies having the claimed function, the Board stated that to arrive at the claimed invention, a person of ordinary skill in the art would have had to engage in undue experimentation. Here, the Board turned back an argument that Section 112 was satisfied once the protein Siglec-15 had been identified and known techniques could be used to identify antibodies with the desired functions. Rather, the Board viewed the parent application as akin to a research plan that would require substantial work to complete and entailed uncertainty as to whether an antibody that both specifically binds to Siglec-15 and delivers the sought-after therapeutic effect could be found. Such experimentation was considered “undue,” and the Board concluded that the parent application fails to show possession of the genus of antibodies recited in the challenged claims.

It followed that the challenged claims were not entitled to priority of the parent application, and that Hiruma is anticipatory prior art under § 102(a). The finding that the parent application was not sufficient to disclose the invention also doomed the patent owner’s attempt to antedate Hiruma, as the patent owner had pointed to the parent application as evidence of earlier conception.

Takeaways

For petitioners, this case is another example of how compliance with § 112 can be challenged in an IPR. This case reinforces a prior Board holding (IPR2014-00414) that established that priority dates could be resolved in an IPR as part of determining whether a patent or printed publication is available as prior art to challenged patent claims.

For patent owners developing new treatments, this case highlights the challenges arising from pressure to file early, for example in advance of a collaboration or interactions with a CRO. While it still may be advisable to file early, applicants should bear in mind that an early filing is only as good as the support it provides for later pursued claims. With respect to functional antibody claims in particular, this case underscores that for previously characterized antigens, it may not be enough to rely on a target antigen sequence and potential therapeutic effects for support, and that doing so in a priority filing may render a patent susceptible to intervening prior art challenges in an IPR.