The US Patent and Trademark Office has released a memorandum that provides updated guidance on how examination of claims directed to antibodies is to be assessed with respect to the written description requirement (35 U.S.C. § 112(a)). In providing the updated guidance, the USPTO has followed the Federal Circuit's recent decision in Amgen Inc. v. Sanofi (Fed. Cir. 2017) [“Amgen”). The memorandum indicates that:

" in view of the Amgen decision, adequate written description of a newly characterized antigen alone should not be considered adequate written description of a claimed antibody to that newly characterized antigen, even when preparation of such an antibody is routine and conventional".

The guidance goes against USPTO practice to date, under which it had been possible to obtain broad claims to an antibody to a "new" antigen even without production of an actual antibody, or with the disclosure of only one or two specific antibodies, provided that the antigen was fully characterized. Under this new guidance, it is likely that patentees will now be significantly limited in the breadth of antibody claims that they can obtain, and in some instances may only be entitled to claim specific antibodies defined by structure.

Written description and antibodies at the USPTO prior to Amgen

US patent law requires that, among other things, a patent specification contains a written description of the invention and details how to make and use the invention. These two requirements are known as the "written description" and "enablement" requirements. The intent and underlying tests for the written description and enablement requirements are quite different.

Originally, the written description requirement was simply used as a tool to prevent the addition of new matter to old disclosures. The Courts then expanded the role of the written description requirement so that it is now used to establish that the applicant had possession of the invention at the time of filing and was not simply inviting further research, i.e. the inventor had actually invented what was being claimed at the time the application for the patent was filed. In contrast, the enablement requirement exists to ensure that the inventor has adequately described how to make and use the invention being claimed without requiring undue further experimentation.

In many instances there is little difference between describing an invention and enabling it, and the line between the two requirements can blur. This may be particularly true for mechanical inventions, where describing the invention and enabling the invention often go hand-in-hand. However, in other circumstances this may not be the case – a description that is enabling does not necessarily demonstrate that the inventor had possession of the invention, and vice versa. In a landmark decision in 2010 (Ariad Pharmaceuticals, Inc. v. Eli Lilly & Co), the Federal Circuit explained that in fields such as "chemical and chemical-like inventions”, “requiring a written description of the invention plays a vital role in curtailing claims that do not require undue experimentation to make and use, and thus satisfy enablement, but that have not been invented, and thus cannot be described.

Despite this somewhat ominous statement by the Federal Circuit in 2010, there was some leniency in the practice applied to antibody claims. Prior to Amgen, when assessing written description in relation to antibody inventions, the USPTO in their Manual of Patent Examining Procedure (MPEP) followed the guidance set by Noelle v. Lederman (355 F.3d 1343 (CAFC 2004)), where it was held that an applicant satisfies the disclosure requirements for broad claims encompassing generically-described antibodies, provided that the applicant had characterized a novel antigen - either by its structure, formula, chemical name, or physical properties, or by depositing the protein in a public depository.

This leniency was based on the notion that the state of the art in antibody production was conventional or routine. It was considered routine to obtain an antibody specific for an antigen by inoculating an animal, collecting antibodies made by the animal and testing the antibodies for binding specificity to the antigen. It was not necessary to understand the structure of the antibody to prepare antibodies against a well characterized antigen. Thus, prior to Amgen, applicants were able to obtain broad claims to an antibody specific for an antigen when that antigen had been newly characterized.

Federal Circuit rejects the "newly characterized antigen" test as a means to satisfy written description

In Amgen, the Federal Circuit considered, amongst other things, whether claims directed to the broad genus of monoclonal antibodies that bind to specific amino acid residues on PCSK9 and block PCSK9 from binding to low density lipoprotein (LDL) receptors were sufficiently described in the application so as to satisfy the written description requirement. Significantly, the claims did not place any structural limitations on the antibody.

In its decision, the Federal Circuit rejected the use of the "newly characterized antigen test" for assessing written description with respect to antibody claims. The Federal Circuit argued that this test incorrectly permitted a finding of adequate written description merely from a finding of enablement, permitting a situation where the patentee would be allowed to "claim antibodies by describing something that is not the invention, i.e. the antigen". The Federal Circuit determined the correct test for written description in relation to antibodies is whether or not the applicants have disclosed a sufficient number of species of antibodies to demonstrate possession of the claimed genus, or adequately described the structural (and optionally functional) characteristics of the genus of antibodies such that the species may be recognized by practitioners in the field.

Looking forward

The Federal Circuit and USPTO have again confirmed that the written description and enablement requirements are separate and distinct, and both need to be satisfied for a patent to validly claim an invention. In the case of antibody inventions, this puts the onus back on the patent applicant to provide a written description in the patent specification of the claimed antibodies per se, and not just of the target to which the antibody binds. The written description may, for example, be based on sequencing of one or more antibodies, or based on one or more deposited hybridomas. If an applicant can show that the disclosed antibodies share structural features that correlate with their function (e.g. binding specificity), then generic claims may still be available, albeit narrower than previously possible. If no such showing can be made, then a patent applicant may be limited to particular sequenced antibodies or antibodies produced by deposited hybridomas.

Given the importance of the therapeutic antibody market, it is expected that US courts will continue to refine the boundaries of what disclosure is required for therapeutic antibodies. However, the days of obtaining patent protection for an entire genus of antibodies based solely on disclosure of a newly characterized antigen appear to be over, at least in the US. While obtaining broad antibody claims may now be more difficult, strategies exist for maximising protection for antibody inventions, which we at Davies Collison Cave can advise upon. We suggest that patentees review their antibody patents to identify those with generic claims that may now be open to attack in view of the Amgen decision. Depending on the disclosure in the patent and the date of issuance, there may be an opportunity to apply for reissue of the patent with amended claims.