Patenting Antibodies — the Latest Case Law and What Biotech Companies Need to Know

Introduction

Antibody-based therapies have revolutionized modern medicine. They have led to unprecedented success in treating various cancers, autoimmune diseases, and other conditions, many of which previously had no known treatment.

The need for broad patent protection for new antibodies is therefore a major concern of the antibody-related research community. Several recent court decisions dealing with enablement and written description of a broad genus of antibodies have cast a veil on the ability of inventors and their assignees to receive claims of worthwhile scope. It has become difficult to obtain and enforce a genus claim that goes beyond one or two specific antibodies.

The critical hurdle is that if a genus claim of therapeutic antibodies contains any semblance of biological function, the need for an understanding of structure-function correlation rears its head. Such understanding is a common requirement for the two portions of the statute, 35 U.S.C. § 112 (a): enablement and written description.[1]

The Legal Landscape

While the underpinning factual analyses used for both portions of the statute have become increasingly similar, the legal requirements are not identical. Enablement of a genus claim requires evidence that, at the desired priority date, a person of skill in the art could achieve the full scope of the claim “without undue experimentation.” In contrast, written description requires evidence that, at the desired priority date, the inventor had “possession” of the full scope of the claim. A genus claim must comply with both. Let us now look at each one in turn.

Enablement
Two cases on the enablement of a genus of antibodies control today’s legal landscape: In re Wands (1988) and Amgen v. Sanofi (2023).

In re Wands established the eponymous eight “Wands factors” by which to measure claim enablement (or lack thereof) in view of a specification, in the context of the state of the art at the time of filing. The Wands factors are (1) the quantity of experimentation necessary; (2) the amount of direction or guidance presented; (3) the presence or absence of working examples; (4) the nature of the invention; (5) the state of the prior art; (6) the relative skill of those in the art; (7) the predictability or unpredictability of the art; and (8) the breadth of the claims. All eight need to be considered and balanced in order to reach a conclusion.

The important thing to understand about the Wands factors is that the claims in the case contain no biological function. The claims are to plain antibodies defined by antigen binding; what we will call its “binding definition.” The court upheld the claims in Wands as enabled by screening alone.

That was not the situation, however, in Amgen v. Sanofi, where the Court of Appeals did not uphold the enablement of the claims. The major distinction between the two cases is that, in addition to antigen binding (as in Wands), the claims in Amgen have a biological function: the binding of antigen also has to block the antigen’s interaction with its cellular receptor. The lack of predictability of how to obtain antibodies that bound to the antigen and that blocked the receptor compounded the enablement problem. In 2023, in affirming the decision of the court in Amgen, the U.S. Supreme Court added the need to set forth the existence of a “general quality common” to all members of the genus that would perform the required biological function. We will call this the “common quality” test.

Written Description
The main cases controlling the landscape for written description of a genus of antibodies are Regents of U. California v. Eli Lilly (1997), Capon v. Eshhar (2005), AbbVie Deutschland v. Janssen Biotech (Fed. Cir. 2014), and Juno v. Kite (2021).

In Regents, the court held that to meet the written description for a genus of biomolecules, the specification, in the context of the state of the art at the filing date, had to set forth either of two alternatives. The first alternative echoes the “common quality” analysis later used in Amgen for enablement: it is to establish a common structure-function correlation between the claimed molecular structure and its biological function. The second alternative is to describe a representative number of species encompassed by the genus. Either one will do.

A few years later, the court in Capon used an analysis reminiscent of the eight factors in Wands, and enunciated several elements to determine if a specification shows sufficient written description to support genus claims. These “Capon factors” are defined as (1) the nature of the invention at issue; (2) the extent and content of the prior art; (3) the maturity of the science or technology; (4) the predictability of the aspect at issue; (5) the scope of the claimed invention; and (6) other considerations appropriate to the subject matter. As in Wands for enablement, all Capon factors need to be considered and balanced when analyzing the written description of the full scope of a genus claim.

AbbVie Deutschland applied the Regents “representative number of examples” alternative to a genus of antibodies. It held that the examples in the specification were in a single class that was not representative of the genus in that they failed to encompass another class to which the accused antibody belonged.

And in Juno, the court applied Regents, this time to a genus of single-chain antibodies fusions. The fusions are multicomponent nucleic acid sequences, where only one of the sequence components is that of a single-chain antibody, while the other component is not. The court analyzed each component under the Regents two alternative test. The claim failed the written description requirement.

Confluence of Enablement and Written Description
Under the present state of the law, the conclusion reached by the courts as to compliance with full-scope enablement for genus claims with biological functions starts with a balancing of the Wands factors. Applying Amgen, the courts then focus on the presence or absence of a common quality among all members of the genus.

In turn, the conclusion regarding full-scope written description starts with a common structure-function correlation or representative number of examples under Regents. It further depends on a balancing of the Capon factors and on the full-scope representativeness of examples under AbbVie. Under Juno, the court then applies this analysis to every structural element of the claim.

The confluence of both aspects of the statute leads to what we may call the “Wands/Capon” factors, supplemented by either alternative in Regents and by the search for a “common quality” under Amgen.

How to Draft and Defend Antibody-Related Genus Claims

In most instances when the court has examined a genus claim to an antibody per se that includes a biological function, or to a method of using an antibody, it has held that the claim lacked either full-scope enablement or full-scope written description. It should be obvious that one solution to the problem of complying with the overall statute for a genus claim lies in avoiding the inclusion of any biological function. Let us explore possible ways of achieving this.

Promising Antibody Genus Claims: Claim as a Product Per Se
The first approach is not to rely solely on method-of-treatment claims, such as administering to a patient an antibody that treats a disease. A priori, the inclusion of a treatment step introduces a biological function into the claim. The claim is then susceptible to questions about structure-function correlations or common qualities and to a balancing of the Wands/Capon factors. If we use method-of-treatment claims — as we invariably will — we must be aware that such claims are highly vulnerable to challenge.

A claim format based on antibody products per se without function has a better chance of surviving challenges. Several formats come to mind, depending on whether the target to which the antibody binds is novel.

When the Target is Not Novel: Claim by Using a Competitive Assay Format
A very common scenario occurs when the target X is not novel. Assume that the inventor has discovered that blocking the known target leads to a heretofore-unknown beneficial therapeutic effect. In such a situation, claiming the antibody per se by its binding to the target may not be possible, as such antibody may be considered obvious. Assume that our inventor has made one specific antibody (a), which performs a newly discovered therapeutic effect when it binds to target X. The specific antibody (a) is novel; that is, there is no identical antibody in the prior art. Because it exhibits the therapeutic effect, the antibody can be demonstrated to be nonobvious.

Now assume that our inventor has sequenced antibody (a) or placed its production cells on deposit at the American Type Culture Collection. Claiming only antibody (a) (known as the “reference antibody”) will produce a narrow claim that can easily be avoided by competitors. Yet with the sequence (or deposit), our inventor can put forth a claim with some scope beyond antibody (a). The claim should include a part (b) drawn to a genus of antibodies that compete with antibody (a) in its binding to target X:

Model claim. An antibody that binds to target X, selected from the group consisting of:
(a) a reference antibody, wherein the light chain of said reference antibody comprises the amino acid sequence of SEQ ID NO: 1 and the heavy chain of said reference antibody comprises the amino acid sequence of SEQ ID NO: 2 [alternatively, antibody (a) can be claimed by its ATCC deposit number]; and
(b) an antibody that competitively inhibits the binding of reference antibody (a) to target X.

Part (b) is a genus that could prevent others from making highly similar antibodies to (a) while literally avoiding the reference antibody.

A challenge for lack of full-scope enablement of a claim with a similar competitive binding requirement was made and fended off in Johns Hopkins University v. CellPro, Inc. (1998), an encouraging precedent. Another, more recent case dealing with a genus of antibodies claimed by competitive binding to a reference is Immunex Corporation v. Sanofi-Aventis U.S. LLC, et al. (2020). The reference antibody in Immunex, just like that in our model claim, is defined by its light- and heavy-chain sequences.

Neither the proposed model claim nor those in Hopkins or Immunex contain any biological function. They are to a genus of antibodies defined by nothing but a competitive immunoassay. Such immunoassays are more like the immunoassay claims that survived in Wands than the claims that were invalidated in Amgen.

Automated Screening for Claims Formatted as Competitive Assays 
The immediate enablement question raised by our model claim is: Can a person of skill in the art (POSA) generate new antibodies that fall within limitation (b) without undue experimentation? A POSA would do so by running an immunoassay test to detect competition for target X between a new antibody and reference antibody (a). While some of the tests may be positive and others not, the law post-Amgen is that some amount of routine screening is still permissible to comply with the enablement requirement.

There is another argument in favor of routine screening for enablement analysis of a genus of antibodies claimed in competitive assay format: the advent of automated artificial intelligence (AI)-assisted, high-throughput methods. Screening for antibodies that bind a target and finding among those the ones that compete with a reference antibody for it are no longer as slow and labor intensive as they were in the past. In 2025, these tasks are done by computerized AI-assisted robots.

If the equipment to do AI-assisted high-throughput screening is not readily available, the specification should at least describe how modern day screening is done by such techniques. The inventor will then be able to rely on two strengthened Wands factors: the advanced state of the art (factor 5) and the high level of skill (factor 6).

Written Description of Claims Formatted as Competitive Assays
Screening, no matter how high-tech, is not a proper method to comply with full-scope written description. Therefore, our arguments about the enablement of a claim that includes a binding definition plus competitive binding requirement do not apply to written description.

To comply with full-scope written description under Regents for part (b) of the model claim, the inventor is well-advised to provide multiple examples of additional antibodies and show that they successfully compete with antibody (a) to target X. The inclusion of multiple, and hopefully representative, examples of other antibodies will avoid the pitfall of AbbVie Deutschland. And Capon factor (3), the maturity of the technology, should also help.

Target Novel or Not: Claim by Using Means-Plus-Function Format
The next possibility for claiming a genus of antibodies without including biological function arises out of the “means-plus-function” statute, 35 U.S.C. § 112(f). This statute allows combination claims to be drafted solely by function, “without the recital of structure.”

Following the statute, we might draft an antibody per se claim as follows:

Model claim. In combination, (1) means for binding a molecular epitope in target X such that the binding of target X to its receptor Y is blocked, together with (2) a pharmaceutically acceptable carrier.

Since the case law suggests that means-plus-function claims not include any “means” structure whatsoever, there is no mention of an antibody or any other such “means.” Principally, the claim contains the function: “that the binding of target X to its receptor Y is blocked.”

In Ex Parte Aaron Keith Chamberlain, et al. (2024), the Patent Trial and Appeal Board approved means-plus-function claims for antibodies. Following Chamberlain, the specification supporting the “means” part of the model claim need not describe more than one example of an antibody that binds to target X.

However, as shown by the later In re Xencor (2025), the full scope of means-plus-function claims is not free from the rigorous written description requirement of Regents or Capon. It is therefore good practice to include as lengthy a description as possible of the many distinct “means” to carry out the claimed binding function. These may include antibodies of different types (e.g., IgG, IgE, IgD, IgM, single chain variables (ScFv), minibodies, nanobodies, chimeric, humanized, fully human, bivalent, fusions of antibodies, receptors, fusions of receptors, antibodies from different germ lines, and the like).

When Target is Novel: Claim by Antigen Binding Only
We will finally discuss the increasingly rare situation where an inventor discovers a heretofore-unknown target X. Assume that this is a novel receptor, the blocking of which leads to a biological result.[2] In such situation, and following Chiron v. Genentech (2004), the inventor may be able to present a genus claim to the antibody per se with a binding definition only:

Model claim. A monoclonal antibody that binds to target X.

Assume that no matter how much our inventor tries, she cannot, at the first filing date, deduce a common quality or common structure-function correlation for all members of the genus. She is then—at least initially—unable to meet the Wands/Capon requirements, the common quality of Amgen, or either of the two alternatives of Regents. Our inventor should therefore not immediately file for claims, even dependent ones, which include a biological function. Yet our inventor should not wait to file an application until she has elucidated a common quality or common structure-function correlation. She can still obtain a broad antibody genus claim with nothing but a binding definition.

For this to work, the specification should include detailed descriptions of at least two uses for the novel antibody: The first is a diagnostic immunoassay for the target and the second is therapy based on blocking the target.

For the first use, the specification should describe nonlabeled, labeled, and solid-phase-bound forms of the antibody. The labeled and solid-phase-bound antibodies can be used in various types of in vitro immunoassays or in vivo tissue imaging. Following In re Magerlein (1979), the nonlabeled antibody should be described as a useful intermediate that leads to the labeled and solid-phase-bound ones utilized in assays. These nonlabeled antibodies should immediately be claimed. With appropriate written description, our inventor may be able to obtain a genus claim to the new and nonobvious unlabeled antibody claimed as a per se product. Such a broad antibody claim should still dominate the use of the same antibody for therapeutic, as well as future, uses.

For the second use, the first specification should describe the therapeutic function that comes from blocking a pathway involving the novel target X. However, while not initially presented, a claim to a novel and nonobvious method of therapy focused on blocking (or activating) the novel target X should eventually be presented. This can happen when there is a better understanding of a common quality or a common structure-function correlation. Because such a claim will a priori include a biological function, it will bring along a full analysis under Amgen, Regents, and the Wands/Capon factors. However, because including a later-elucidated common quality will likely generate a new filing date, the inventor should not wait too long to file the therapy claim. If she does, her own published first patent application disclosing the therapy becomes prior art.

[1] For a more detailed and annotated version of this chapter, see Jorge Goldstein, “Solutions to the Problem of Antibody Genus Claims,” 52 AIPLA Quarterly Journal, No. 3, 513-64 (Summer 2024)

[2] For more detail on the treatment of the situation in this section, please see Goldstein, footnote 1.

This article appeared in the 2025 Life Sciences IP Tool Kit.