Brief of Law Professors Joshua D. Sarnoff, Sharon K. Sandeen, and Ana Santos Rutschman as Amici Curiae in Support of Respondents, Amgen, Inc. V. Sanofi, No. 21-757

44 Pages Posted: 13 Feb 2023

See all articles by Joshua D. Sarnoff

Joshua D. Sarnoff

DePaul University College of Law

Sharon K. Sandeen

Mitchell Hamline School of Law; Hanken School of Economics

Ana Santos Rutschman

Villanova University - Charles Widger School of Law

Date Written: February 10, 2023


For over two hundred years, the Patent Act has consistently required that an applicant for a patent actually conceive an invention and disclose what they have invented, in a manner that also enables skilled practitioners to make and use the invention conceived and disclosed. Courts have applied many different doctrines to invalidate patents or patent claims when applicants have sought to patent what they have not invented or disclosed, typically by claiming results or by claiming a genus of unenumerated structures that perform desired results or recited functions. Courts have made clear that such claims are not claims to “inventions” within the meaning of the Patent Act, because the applicants have not yet determined what structures would perform the desired or recited functions. Such invalid claims, where the applicant has failed to disclose a sufficient structural-functional relationship, have variously been referred to as not invented, overbroad, functional at the point of novelty, research plans, or not enabled.

Under the enablement doctrine, applicants: (1) cannot shift to the public the burden of “inventing” the claimed genus; and (2) must provide sufficient information for the public to “make and use” a properly disclosed and claimed genus invention. Although the decision of the U.S. Court of Appeals for the Federal Circuit in this case was clearly correct under In re Wands, 858 F.2d 731 (Fed. Cir. 1988), this Court needs to provide guidance on both aspects of the enablement standard in order to support its further refinement. First, how much of a structural-functional relationship must be disclosed to validly support a genus claim without improperly shifting the burden of inventing to skilled artisans? Second, for an already invented and properly disclosed genus, how much additional information must an applicant provide to “enable” skilled artisans to “make and use” the claimed genus? This second requirement must consider how much time, money, and effort can be imposed by applicants on skilled practitioners in regard to the scope of the invention actually claimed. The current “undue experimentation” standard in Wands, however, does not provide any meaningful referent to guide such analysis (“undue” compared to what?), and improperly conflates these two required inquiries. Nevertheless, the evidentiary factors identified in Wands remain relevant to the second inquiry.

This Court and the Federal Circuit have identified numerous concerns underlying the various patent law doctrines that prohibit claiming a genus of structures without disclosing a sufficient structural-functional relationship. In general, there are two important reasons not to permit such claims. The first is that granting such claims provides a disproportionate reward to applicants. Applicants are entitled to claim the particular structural species that they have identified that perform the desired functions. When they do so, applicants then may receive additional protection for functionally “equivalent” structures under the “doctrine of equivalents.” If applicants also can identify a common structural-functional relationship that sufficiently assures that other structures will perform the required functions, then (and only then) can they validly claim a genus of structures that they have not identified individually. This assures commensurability between the invention made and the rights granted. The second reason is that claiming a result or a research plan blocks sequential innovation and commercialization of additional structures that the applicant has not yet identified to possess the desired result or recited function, but has claimed using structural or functional language. This excessive claiming is particularly pernicious given the constrained experimental use exception adopted by the lower courts.

The instant case is an “easy case” in view of the complete lack of disclosure connecting structure to function. The case involves broad genus claims based entirely on desired and claimed functions. There is no disclosure that would indicate what structures are even likely to exhibit the recited functions, while requiring structures falling within the claimed genus to do so. This case thus does not require the Court to address how much of a structural-functional relationship must be identified and disclosed in order to invent, disclose, and properly claim a genus. Nor does this case require the Court to address the permissible amount of time, effort, and money that can be required of skilled practitioners to make and use a properly disclosed and claimed genus. The Court thus should affirm the decision below and invalidate the claims at issue without remand, while providing the required guidance for the lower courts to further develop the law of enablement.

Keywords: patent, functional claiming, enablement, written description, structural-functional relationship, genus-species, innovation, sequential invention, research plan, result or function

JEL Classification: O31, O32, O33, O34, O35, O36, O37, O38, O39

Suggested Citation

Sarnoff, Joshua D. and Sandeen, Sharon K. and Santos Rutschman, Ana, Brief of Law Professors Joshua D. Sarnoff, Sharon K. Sandeen, and Ana Santos Rutschman as Amici Curiae in Support of Respondents, Amgen, Inc. V. Sanofi, No. 21-757 (February 10, 2023). Available at SSRN: or

Joshua D. Sarnoff (Contact Author)

DePaul University College of Law ( email )

25 E. Jackson Blvd.
Chicago, IL 60604-2287
United States
312-362-6326 (Phone)

Sharon K. Sandeen

Mitchell Hamline School of Law ( email )

875 Summit Ave
St. Paul, MN 55105-3076
United States

Hanken School of Economics ( email )

P.O. Box 479
FI-00101 Helsinki, 00101

Ana Santos Rutschman

Villanova University - Charles Widger School of Law ( email )

299 N. Spring Mill Road
Villanova, PA 19085
United States

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