Amgen v. Sanofi: The Enablement Tax on Functional Genus Claims

Amgen Inc. v. Sanofi, 598 U.S. 594 (2023), No. 21-757, decided May 18, 2023, is the Supreme Court’s most consequential statement on the enablement requirement in decades. The unanimous opinion by Justice Gorsuch affirmed the invalidation of Amgen’s broad antibody claims and, in doing so, reaffirmed a principle as old as American patent law: the breadth of a patent’s claims must be matched by the breadth of what its specification actually teaches. Though decided in 2023, the case remains the governing framework for any functional or genus claim and is essential reading for the life-sciences and chemistry bars.

At a glance

• Case: Amgen Inc. v. Sanofi, 598 U.S. 594 (2023), No. 21-757
• Decided: May 18, 2023; unanimous (9-0), opinion by Justice Gorsuch; Federal Circuit affirmed
• Holding: A patent specification must enable a skilled artisan to make and use the entire scope of the claimed invention; Amgen’s functional genus claims were not enabled
• Status: Final

The statutory requirement and the claims

Section 112(a) of the Patent Act, 35 U.S.C. § 112(a), requires that a patent’s specification describe the invention in terms sufficient to enable a person skilled in the art to make and use it. Enablement is the consideration the inventor gives in exchange for the patent’s exclusionary right — the public’s price for the monopoly is a disclosure that genuinely teaches the invention.

Amgen’s patents claimed a genus of antibodies defined not by their structure but by their function: the entire class of antibodies that bind to particular amino-acid residues on the PCSK9 protein and thereby block it from degrading LDL receptors (the mechanism relevant to lowering cholesterol). The functional definition potentially embraced a vast number of distinct antibodies — by some accounts millions. Yet the specification disclosed the amino-acid sequences of only 26 antibodies and offered two methods for finding others: a “roadmap” for generating and screening candidate antibodies, and a “conservative substitution” technique for tweaking known ones.

The holding: claim the genus, enable the genus

The Court held the claims not enabled. Its governing proposition is simple to state and demanding in application: “the more a party claims, the more it must enable.” A specification may claim an entire class of embodiments, and need not describe each one, if it discloses some general quality reliably enabling a skilled artisan to reach the full scope of the class. But where the claimed genus is vast and the disclosure amounts to a method of trial-and-error discovery, the specification does not enable the class — it assigns a research program.

Amgen’s “roadmap” and “conservative substitution” were, in the Court’s view, precisely that: instructions to make candidate antibodies and test them to see whether they fall within the functional definition. That is undue experimentation — a hunt across a functional landscape rather than a teaching of how to reach its full extent.

A century-old patent bargain, reaffirmed

The opinion is consciously rooted in historical precedent, and the lineage matters because it signals continuity rather than innovation. The Court invoked O’Reilly v. Morse (the telegraph case, where Morse’s claim to all use of electromagnetism for printing characters at a distance was held overbroad), The Incandescent Lamp Patent (where a claim to fibrous and textile incandescing conductors failed because the patentees had not enabled the full claimed class), and Holland Furniture and Minerals Separation. The throughline is that functional claiming untethered from a commensurate disclosure has always failed the enablement requirement. Amgen did not invent a new test; it declined to relax an old one for the biologics era.

Open questions

Amgen leaves the legal standard intact but its application contested. How much disclosure is “enough” for a functional genus remains intensely fact-specific, and the line between an acceptable general quality and an impermissible research assignment will be litigated antibody by antibody, compound by compound. The decision also does not address the related — and frequently co-pending — written-description requirement, which polices functional claiming through a different doctrinal lens. Practitioners should expect both doctrines to be deployed together against broad claims.

Implications for inventors and businesses

• Match scope to disclosure. Broad functional or genus claims invite enablement attack unless the specification genuinely teaches how to reach the full claimed class. Narrower, structurally supported claims are more durable.
• Disclose representative diversity and a real path. A handful of examples plus a screening protocol may not enable a vast functional genus. Build the specification to support the breadth actually claimed.
• Expect heightened scrutiny in life sciences and chemistry. Antibody, biologic, and chemical-genus claims are the natural targets of Amgen-based challenges; portfolio strategy should account for the heightened bar.

Frequently asked questions

What did Amgen claim that was the problem? A genus of antibodies defined by their function — what they bind to and what they block — rather than by their structure, potentially covering an enormous number of antibodies the specification did not actually teach how to make across the full range.

Did the Court create a new enablement test? No. It applied the longstanding “full scope” enablement principle, grounding the result in precedents stretching back to O’Reilly v. Morse and The Incandescent Lamp Patent.

What is the practical takeaway for patent drafting? Claim no broader than the disclosure can support. The more expansive and functional the claim, the more the specification must enable a skilled artisan to reach the entire claimed scope without undue experimentation.

Authorities and sources

• Amgen Inc. v. Sanofi, 598 U.S. 594 (2023), No. 21-757 (May 18, 2023). Caption, citation, date, unanimous Gorsuch authorship, and holding corroborated across Sterne Kessler, Faegre Drinker, Greenberg Traurig, and Cooley case analyses.