Currently pending before the U.S. Supreme Court are three petitions for certiorari dealing with the “written description” requirement in the Patent Act, 35 U.S.C. §112. While each petition presents a distinct question for review, the high court has rarely heard cases presenting issues involving the “written description” requirement and its impact on patent invalidity.
Section 112 of the Patent Act comprises, among other provisions, the “written description” requirement. The relevant statutory provision states that:
The specification [of the patent application] shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention. [35 U.S.C. §112(a)].
The written description or specification of a patent application sets forth the “four corners” of the patentable subject matter from which the asserted claims must be based. Issued patents lacking in adequate disclosure under the written description requirement are prone to successful invalidity attack. The requirement mandates that the description enable a person skilled in the art to make and use the claimed invention without undue experimentation. In several recent cases involving drugmakers, the Federal Circuit has invoked that requirement to invalidate patents, prompting repeated requests for the Supreme Court to clarify the law.
In Amgen Inc. v. Sanofi, 987 F.3d 1080, No. 2020-1074 (CAFC 2021), the Federal Circuit held that Amgen’s patents on the cholesterol medication Repatha were invalid on the ground that the written description of the invention failed to meet the “enablement” requirement, i.e., the description failed to properly enable a person skilled in the art to make or use the invention without undue experimentation. The CAFC panel further held that “enablement” is an issue for judges rather than juries, thereby treating the question much like claim construction.
It is well established that to prove that a claim is invalid for lack of enablement, a challenger must show by clear and convincing evidence that a person of ordinary skill in the art would not be able to practice the claimed invention without “undue experimentation.” In this case, the District Court held after a jury trial that the claims in Amgen’s patents were overly broad and the written description was more of a “road map” than a clear and concise description of how to make the drug.
The Federal Circuit patent agreed, finding that, although the specification provides some guidance, including data regarding certain embodiments, considering the disclosed roadmap in light of the unpredictability of the art, any reasonable factfinder would conclude that the patent does not provide significant guidance or direction to a person of ordinary skill in the art for the full scope of the claims. Here, even assuming that the patent’s “roadmap” provided guidance for making antibodies with binding properties similar to those of the working examples, no reasonable factfinder could conclude that there was adequate guidance beyond the narrow scope of the working examples that the patent’s “roadmap” produced.
Further, according to the panel (quoting the District Court opinion), the only ways for a person of ordinary skill to discover undisclosed claimed embodiments would be through either “trial and error, by making changes to the disclosed antibodies and then screening those antibodies for the desired binding and blocking properties,” or else “by discovering the antibodies de novo” according to a randomization-and-screening “roadmap.” Either way, the required experimentation “would take a substantial amount of time and effort.”
As a result, Amgen’s patents on Repatha were affirmed by the CAFC to be invalid for lack of proper enablement under the written description requirement.
In April, the Supreme Court invited U.S. Solicitor General Elizabeth Prelogar’s to file a brief on the petition, a signal that the Court is likely to hear the case. The Solicitor General has not yet filed a brief in the case.
Amgen Petition for Certiorari, November 2021 (with appendix)

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Two petitions were filed more recently seeking an appeal from CAFC rulings interpreting the written description requirement under Section 112.
In Juno Therapeutics Inc., et al. v. Kite Pharma, Inc., Juno presents the following question:
Is the adequacy of the “written description of the invention” to be measured by the statutory standard of “in such full, clear, concise, and exact terms as to enable any person skilled in the art to make and use the same,” or is it to be evaluated under the Federal Circuit’s test, which demands that the “written description of the invention” demonstrate the inventor’s “possession” of “the full scope of the claimed invention,” including all “known and unknown” variations of each component?
According to Juno, “possession” of the full scope of the patented invention is an “impossible” standard to meet and not supported by Section 112.
Juno Therapeutics’ Petition for Certiorari, June 13, 2022
In Biogen International GmbH v. Mylan Pharmaceuticals, Inc., Biogen is seeking to overturn a ruling by the Federal Circuit panel that invalidated its patent covering its multiple sclerosis drug Tecfidera, arguing that the Federal Circuit has improperly held that Section 112 requires proof that an invention is “effective,” which the company said has no basis in law.
Biogen Petition for Certiorari, June 2022
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Each of the above cases present important questions concerning the breadth and scope of the written description requirement. While it is unlikely the Supreme Court will grant all three petitions, proper guidance is seemingly needed in the subject and practitioners would be served if all three cases were taken up.
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Richard A. Catalina, Jr. is a senior partner and Chair of the Intellectual Property and Complex Litigation Department of Jardim, Meisner and Susser, P.C. Mr. Catalina specializes in litigating patent, trademark, trade secret and related Lanham Act disputes, and inter partes proceedings before the Patent Trial and Appeal Board. Mr. Catalina has been practicing law for more than 33 years and has litigated more than one hundred matters in federal and state courts across the U.S, as well as inter and ex partes matters before the Trademark Trial and Appeal Board and the Patent Trial and Appeal Board.