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May 22, 2023

The Enablement Challenge for Genus Claims Under U.S. Patent Law: How Much Disclosure Is Enough After Amgen v. Sanofi?

The Enablement Requirement and Benefit of Genus Claims

While patented technology and U.S. patent laws are often complex, the foundation of our patent system is based on a fairly simple quid pro quo. In exchange for publicly disclosing information that advances science and technology, the U.S. government will grant the disclosing party a patent providing a set of exclusionary rights for a limited period of time (i.e., a limited monopoly) so the disclosing party can prosper from their inventive efforts. To ensure the exclusionary rights afforded to the disclosing party are commensurate with the information disclosed, patent applicants must satisfy an enablement requirement, which requires the specification of a patent to “contain a written description of the invention . . . in such full, clear, and exact terms as to enable any person skilled in the art to which [the invention] pertains . . . to make and use the same”1 without undue experimentation,2 where the “invention” is delineated by the claims within the patent. In other words, the enablement requirement is there to ensure that the scope of the monopoly awarded does not extend beyond that fairly invented and disclosed to the public by the patent applicant. Failure to satisfy this requirement is significant as it will prevent an applicant from securing a patent in the first place or, if a patent is acquired, cause the issued patent to be invalid and unenforceable.

For pharmaceuticals and other life-science-based technologies, it is common to seek protection for genus-based claims. These claims are directed to a group of related items with a common functionality (e.g., a group of chemicals providing a common physiological effect), as opposed to individual members, or species, of such group. The motivation for seeking claims of this type is straightforward: claims directed to a group of items defined by their function instead of structure offer a broader scope of protection, and therefore better guard against competitor design-arounds and ensure a better return on research and development efforts is realized. Depending on the technology at hand, however, the number of individual species populating a genus may be so large that it is not practical or even possible to carry out the research required to identify and disclose every species of a genus within a patent application. Thus, the million (or billion) dollar question for genus-based claims is: does the enablement requirement require a patent’s specification teach one of ordinary skill in the pertinent art to make and use all, or substantially all, species encompassed by the claimed genus?

Amgen, Inc. v. Sanofi

On May 18, 2023, in Amgen, Inc. v. Sanofi, No. 21-757, the Supreme Court unanimously affirmed the Federal Circuit’s finding that two of Amgen’s patents—U.S. Patent No. 8,829,165 (the "’165 Patent”) and U.S. Patent No. 8,859,741 (the “’741 Patent”)—were not enabled and answered the above-posed question in the affirmative:

If a patent claims an entire class of processes, machines, manufactures, or compositions of matter, the patent’s specification must enable a person in the art to make and use the entire class. In other words, the specification must enable the full scope of the invention as defined by its claims. The more one claims, the more one must enable.3

The Court’s opinion, authored by Justice Gorsuch, thus makes clear that the bar for enabling genus claims is a high one. The pertinent question for applicants, particularly in the life sciences, then is: how much and/or what type of disclosure is required for these types of claims? While the answer to this question will clearly depend on the nature of the technology to which the claims relate, the Court did provide some limited guidance on the issue.

In Amgen, the Court indicated that enablement of an entire genus does not necessarily require that applicants describe how to make and use every single species within the genus and that “it may suffice to give an example (or a few examples) if the specification also discloses ‘some general quality . . . running through’ the class,”4 provided that general quality “reliably enable[s] a person skilled in the art to make and use all of what is claimed, not merely a subset.”5 The outcome of Amgen makes clear, however, that for the unpredictable arts such “general quality” or “common quality” cannot simply be the shared functional effect provided by the members of the genus around which the genus claim is built. Rather, such quality must seemingly be one of structure or other characteristic that (i) facilitates the functional effect reflected in the genus claim and (ii) allows one of ordinary skill in the pertinent art to identify each respective member in the recited genus with a reasonable, but not undue, amount of experimentation relative to the invention and the technological field to which it belongs.6 In the unpredictable arts, like that of the technology in Amgen, the identification of a common quality may often prove difficult.

The disclosures provided by Amgen in support of its genus claims and the Court’s treatment of the same also provide some insight with respect to disclosures that are likely to prove insufficient to establish enablement for genus-based claims as well as potential alternative strategies for meeting the requirement. The technology at issue in Amgen relates to development of monoclonal antibodies that reduce low-density lipoprotein (“LDL”) cholesterol, which is commonly referred to as “bad cholesterol” due its contribution in the development of cardiovascular disease, heart attacks, and strokes. More specifically, the technology relates to monoclonal antibodies which inhibit PCSK9, a naturally occurring protein that binds to and degrades LDL receptors that normally allow the body to extract LDL cholesterol from the bloodstream. To broadly protect these antibodies, Amgen filed for and obtained protection for claims in the ’165 and ’741 Patents directed to monoclonal antibodies which (1) bind to particular amino acid residues of PCSK9 and (2) block PCSK9 from binding to LDL receptors. In other words, Amgen secured patent protection for antibodies which exhibit specific functional effects as opposed to antibodies with a particular structure. As an aside, both Amgen and Sanofi initially secured patent protection for PCSK9-inhibiting drugs corresponding to antibodies with unique amino acid sequences. Later, Amgen obtained the broader ’165 and ’741 Patents and sued Sanofi for infringement, prompting Sanofi to initially claim, and the district court and Federal Circuit to later find, invalidity on enablement grounds.

In support of the function-based genus claims in the ’165 and ’741 Patents, Amgen disclosed the amino acid sequence of 26 antibodies which provide the above-noted functionality as well as the three-dimensional structure for two of the antibodies. Seemingly adopting Sanofi’s contention that the antibodies providing the above functionalities and protected by Amgen’s claims cover potentially millions of undisclosed antibodies, the Court found the above disclosure insufficient to enable the full scope of Amgen’s genus claims.7 Accordingly, in the absence of an identified common quality consistent with that noted above, the inclusion of examples corresponding to a small subset of a vastly populated genus will not be sufficient to enable genus-based claims.

In a further effort to support its function-based genus claims, Amgen also disclosed two methods for identifying other antibodies providing the above functionalities. The first method, referred to in the case as a “roadmap,” comprised a series of successive steps which the Court characterized as instructing one to: (1) generate a set of antibodies; (2) test the antibodies for PCSK9 binding; (3) test the antibodies found to bind to PCSK9 generally for binding to the particular amino acid residues of PCSK9 which facilitate its binding to LDL receptors; and (4) test those antibodies found to bind to the particular amino acid residues to see if they actually prevent PCSK9 from binding to LDL receptors.8 The second method, referred to in the case as “conservative substitution” was characterized by the Court as requiring one to (1) start with an antibody known to provide the above-noted functions; (2) substitute select amino acids in the antibody; (3) test the resulting antibody to see if it provides the above-noted functions.9 While the Court did not close the door on the possibility of the disclosure of methodologies for identifying the members of a claimed genus being a viable substitute for actually disclosing each respective member of the genus, it did not find Amgen’s methods as enabling to the claimed genus. Rather, the Court equated Amgen’s two methods to mere trial-and-error processes that would require undue experimentation.10

Accordingly, in some cases, the disclosure of methods referring to the manner in which the respective members of a genus can be identified, made, and used may be a more reasonable path to establishing enablement than actually disclosing every member of the genus. However, the Court has signaled that such methods must be more than a general invitation to conduct general research until certain milestones are reached and the desired functionality recited in the genus claim is realized. To be sure, developing methods which clearly lead one of skill in the art to each member of a claimed genus with only reasonable experimentation for the technology as to satisfy the enablement requirement will, for many technologies, be no easy task.


In light of Amgen and the Court’s clarification that the enablement requirement for genus-based claims is a high one, it will not be surprising if, at least in the life sciences, patent applicants see an uptick in enablement-based rejections at the United States Patent Office or patentees see increased invalidity challenges on enablement grounds in federal court or the Patent Trial and Appeals Board. To guard against such rejections and challenges, patent applicants pursuing broad genus-based claims in instances where it is not practical to identify all species of the genus should try, at least to the extent that it is possible, to identify a structure or other characteristic common to all species in the genus and elaborate as to how the same can be identified by one of skill in the art within their patent applications. Such common structure or characteristic will likely need to (i) facilitate the functionality reflected in the genus claim and (ii) allow one of ordinary skill in the pertinent art to identify each respective member in the recited genus with only a reasonable amount of experimentation to be viable. The disclosure of non-trial-and-error-based methods which clearly detail how each respective member of the claimed genus can be identified, made, and used can also be implemented into initial application filings to provide another potential avenue for satisfying the enablement requirement.

As both of the above-noted options will likely prove difficult for many technologies, players in these fields should factor in the enablement challenge for genus-based claims into their business decisions and forecast anticipated research and development returns which account for scenarios where patent protection can only be obtained for individual species of a genus which are known and demonstrable. As a part of this calculus, the ease and likelihood in which competitors will independently develop alternative species within the genus should be taken into account. Furthermore, in view of Amgen, patent applicants should certainly employ claim and filing strategies which intentionally insulate their commercial embodiments from genus-based claims that are more sensitive to enablement challenges. In this regard, patent applicants should make sure to seek protection for claims which are specifically directed to the species in the applicant’s possession.

Stites & Harbison, PLLC’s full-service Intellectual Property & Technology Group regularly assists clients in the acquisition, management, licensing, and litigation of patents, copyrights, trademarks, and trade secrets. For questions, comments, or assistance with any intellectual property-related matters, please contact the author or any of the other attorneys in our group.

1 35 U.S.C. § 112(a).
2 See In re Wands, 858 F.2d 731, 737 (Fed. Cir. 1988).
3 Amgen, Inc. v. Sanofi, No. 21-757 at p. 13.
4 Id. (citing Incandescent Lamp Patent, 159 U.S. 465, 475 (1895).
5 Id.
6 Id. at 14–15 (noting “[A] specification [is not] necessarily inadequate just because it leaves the skilled artist to engage in some measure of adaptation or testing.” and “What is reasonable [experimentation] will depend on the invention and the underlying art.”).
7 See id. at 6, 15.
8 Id. at 5–6.
9 See id. at 6.
10 See id. at 16–17.

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