Stroke of 'Genus': Amgen Inc. v. Sanofi

By Kelsey Nix

The U.S. Supreme Court recently struck down broad patent claims covering a genus of antibodies, reaffirming in a 9-0 decision that a patent must “enable” the full scope of its claims (Amgen Inc. v. Sanofi[1]). Amgen, Inc., (Amgen) a biopharmaceutical company, had developed cholesterol-lowering antibody drugs, and obtained two patents. Amgen then sued competitor Sanofi, which had produced similar antibodies for lowering cholesterol. Amgen alleged that its broad genus claims covered Sanofi’s particular antibodies, though Amgen’s patents did not specifically disclose the sequences in Sanofi’s accused product.

The Delaware district court found Amgen’s patent claims invalid because the patents did not enable a person of ordinary skill in the art (POSITA) to make and use their full scope. Amgen appealed, and the Court of Appeals for the Federal Circuit affirmed. The Supreme Court unanimously affirmed the lower court rulings.

The Technology: Cholesterol-Lowering Antibodies

PCSK9 is a naturally occurring protein that tends to increase the amount of bad LDL cholesterol in the blood. Amgen’s antibodies reduce LDL cholesterol by binding to and interfering with the PCSK9 protein. Amgen’s patents disclosed, and enabled POSITAs to recreate, 26 specific antibody sequences—26 keys that fit the right keyhole on PCSK9—and thus reduce LDL cholesterol.

But Amgen’s genus claims encompassed millions of antibodies—much broader than the 26 specific antibodies that Amgen disclosed. In other words, Amgen claimed not just 26 keys, but all possible keys that fit the PCSK9 keyhole.

Amgen also argued that its patents included two guides for finding more PCSK9-fitting antibodies: (1) a “roadmap” for testing new antibodies for suitability, and (2) a “conservative substitution” method for starting with known working examples and trying a swap of similar building blocks.

Supreme Court Analysis: Has the Patentee Upheld Its Side of the Bargain? 

The Supreme Court begins by emphasizing the patent “bargain.”[2] The patent system is rooted in a quid pro quo between the inventor and the public. In exchange for teaching the world how to make and use an invention, the inventor gets an exclusive right to monopolize it for a time. The enablement requirement of patents is thus baked into the basic bargain: enablement is the quid, and the grant of a patent is the quo.

The Court then explains that the enablement doctrine has remained consistent throughout American patent history, changing little as other requirements have come and gone.[3] Instead of discussing and applying the body of recent enablement caselaw, the Court reaches back to the greatest hits of the nineteenth century, analogizing monoclonal antibodies to Morse’s telegraph and Edison’s light bulb. “While the technologies in these older cases may seem a world away from the antibody treatments of today, the decisions are no less instructive for it.”[4]

The Court summarizes the patent statute’s enablement requirement:

If a patent claims an entire class of processes, machines, manufactures, or compositions of matter, the patent’s specification must enable a person skilled 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.[5]

But the Court leaves some room for claiming a genus. The genus can be enabled by disclosing “some general quality running through the class that gives it a peculiar fitness for the particular purpose.”[6] The Court also underscores that leaving a “reasonable amount of experimentation” for the POSITA does not defeat enablement. Of course, “reasonable” is a variable yardstick: “[w]hat is reasonable in any case will depend on the nature of the invention and the underlying art.”[7]

With this analytical framework, the Supreme Court concluded that “Amgen has failed to enable all that it has claimed, even allowing for a reasonable degree of experimentation.”[8] The Court also dismissed Amgen’s “roadmap” and “conservative substitution” arguments, finding that they constituted only “research assignments” that left too much work to trial and error. “That is not enablement,” and does not justify excluding competitors who do the work of “painstaking” experimentation.[9]

Significance of Amgen

What are the takeaways from Amgen for patent practitioners?

  • Patents should include a robust set of species claims. Wherever the enablement of broad claims might be tenuous, the inventor might need to rely on these narrower species claims.
  • Inventors face a strategic choice when deciding when to file a patent application for technologies under continuous development. The advantages of filing early to win a first-to-file race must be balanced against a better developed disclosure that can enable more and broader species claims or a genus.
  • Under the doctrine of equivalents, something that “performs substantially the same function in substantially the same way to obtain the same result” as a claimed invention still infringes.[10] Because a competitor cannot make an insubstantial change to a claimed species, the doctrine of equivalents often can effectively increase the scope of patent protection for a narrow patent claim.
  • Keeping prosecution open after patent issuance is already good practice. The ability to add new claims to bolster an existing set of species claims gives another reason to file a continuation application after receiving a notice of allowance.
  • Amgen gives accused infringers another arrow in their quiver to assail the validity of an asserted claim in litigation. 

The Federal Circuit’s analytical framework should still guide patent practice. The Federal Circuit and district courts seem likely to return to the same analysis ultimately upheld in Amgen: applying the well-worn Wand factors[11] to determine if a POSITA would need to conduct undue experimentation to arrive at the full scope of the claimed matter. These factors include the amount of experimentation needed, the amount of guidance and working examples given, as well as the nature and predictability of the art. Broad claims will likely fail if supported only by coarse roadmaps, as in Amgen. But how much additional guidance must accompany a valid genus claim will continue to be tested on a case-by-case basis.

Is It Still Possible To Claim a Pharmaceutical Genus?

Amgen and Sanofi disagreed on whether claiming a pharmaceutical genus is practical under the full scope enablement standard. Some leading scholars argued in an amicus brief that the full scope enablement standard is too demanding and effectively blocks all genus claims for therapeutic drugs.[12] Amgen, in its brief, called the effects of the full scope test “particularly severe in the biotech and pharmaceutical industries.”[13] Sanofi countered by citing examples of pharmaceutical genus claims that survived full scope enablement challenges.[14]

The Supreme Court sidestepped the possible consequences of its decision on the industry, writing that the practical effect of full scope enablement as applied to modern drug discovery “is a policy judgment that belongs to Congress.”[15]


Amgen did not change existing patent law, but is still a significant decision. Technology-practicing entities defending against infringement suits should be aware that the path to attack the enablement of genus claims has been more clearly lit. On the other side, patentees should be prepared to defend the enablement of their genus claims on the facts, as the legal standard has again been sanctioned.

If you have questions related to this alert, please contact Kelsey Nix, Co-Chair of IP Litigation, or the Smith Anderson lawyer with whom you currently work.

Special thanks to contributing author and Smith Anderson summer associate, Ken Chu.  

[1] 143 S. Ct. 1243 (2023).

[2] Id. at 1251.

[3] The enablement requirement is now found in 35 U.S.C. §112.

[4] Amgen, 143 S. Ct. at 1252.

[5] Id. (emphasis added).

[6] Id. (internal citations and quotations omitted).

[7] Id. at 1255.

[8] Id. at 1256.

[9] Id. at 1256–57.

[10] Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 608 (1950).

[11] See In re Wands, 858 F.2d 731, 737 (Fed. Cir. 1988).

[12] Brief of Intellectual Property Professors as Amici Curiae in Support of Petitioners, Amgen Inc. v. Sanofi, 143 S. Ct. 1243 (2023) (No. 21-757).

[13] Brief for Petitioners at 39, Amgen Inc. v. Sanofi, 143 S. Ct. 1243 (2023) (No. 21-757).

[14] Brief for Respondents at 44–45, Amgen Inc. v. Sanofi, 143 S. Ct. 1243 (2023) (No. 21-757).

[15] Amgen Inc. v. Sanofi, 143 S. Ct. 1243, 1257 (2023).



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