In Amgen v. Sanofi, the U.S. Supreme Court affirmed the Federal Circuit’s ruling that the claims at issue, directed to a genus of antibodies that bind to a particular region of a protein, were not enabled. In doing so, the Court made clear that patent claims venturing beyond the scope of an inventor’s actual discovery will not survive scrutiny under § 112(a)’s enablement requirement.¹ The Federal Circuit invalidated the Amgen patents-in-suit under § 112(a) because their shared specification failed to teach a person of skill in the art (a “POSA”) how to make and use the entire class of antibodies claimed when it only identified twenty-six.² While a patentee need not disclose every single member of the class claimed, the Supreme Court agreed with the Federal Circuit that the amount of experimentation required by a POSA to find other members of the class must be “reasonable.”³

The written description requirement allows a patent owner to justify claims setting the boundaries of a patent. Patents claiming a genus “require[] the disclosure of either a representative number of species falling within the scope of the genus or structural features common to the members of the genus so that one of skill in the art can ‘visualize or recognize’ the members of the genus” to satisfy the written description requirement.⁴ Unlike in Amgen, the Supreme Court recently declined an opportunity to clarify the written description requirement in Juno Therapeutics, Inc. v. Kite Pharma, Inc. Accordingly, practitioners should abide by the Federal Circuit’s written description standard as applied to broad genus claims in Juno.

In Juno Therapeutics, Inc. v. Kite Pharma, Inc., the Federal Circuit addressed written description in its evaluation of a patent for antigen receptors used in T cell therapy.⁵ Kite, the alleged infringer, argued that Juno’s patent failed § 112(a) and was invalid because Juno’s written description only identified two species of the “millions of billions” of the claimed genus of antigen receptors.⁶ Kite argued that such a limited disclosure would not allow a POSA to practice the invention as it also failed to disclose the shared structural features that would bind to specific targets, or allow recognition of genus members capable of binding to those targets from those that were not capable.⁷ A jury disagreed, finding that the written description of Juno’s patent satisfied § 112.⁸ But the Federal Circuit reversed, concluding that, because the patent claimed such a large genus, the specifications’ disclosure of two species was insufficient. Because a POSA would be unable to distinguish between members of the genus that achieve the claimed function and those that do not, the Court found that the patent did not sufficiently indicate that the inventors possessed the full scope of the genus that they chose to claim. ⁹ Thus, the Court held that the jury’s verdict was not supported by substantial evidence.¹⁰ The Supreme Court denied certiorari, leaving unclarified the question of when a patent’s written description demonstrates that the inventor’s “possession” of “the full scope of the claimed invention.”¹¹ If and until the Supreme Court weighs in as it did in Amgen, the Federal Circuit and district courts are left to define these boundaries themselves.

In the wake of Juno, the Federal Circuit has continued to apply a strict written description requirement for genus claims. For example, in BASF v. CSIRO, the Federal Circuit affirmed in part and reversed in part a jury’s determination that written description satisfied the requirements of § 112.¹² At issue was the validity of patents directed to fatty acid production from plant cells in which the asserted claims “address the blueprint [of the fatty acid production pathway] as well as implementations of that blueprint in plant seeds generally, and in canola specifically.”¹³ The specification shared by all patents-in-suit identified canola as the preferred embodiment of the invention, but the patents included claims covering “the ‘genus’ of plant cells.”¹⁴ The Federal Circuit found that substantial evidence existed to allow the jury to conclude that a POSA reading the specification would have expected the claimed invention to work in canola¹⁵, but reversed the jury’s determination that the specification provided sufficient written description for broader genus claims reaching any plant cell—as the specification did not necessarily demonstrate possession of the claimed invention for all plant cells, focusing instead on canola.¹⁶

In PureCircle. v. Sweegen, the Federal Circuit affirmed the invalidity of two patents-in-suit for failing to disclose in their written description a representative number of species or common structural features of the claimed genus of enzymes to identify those which would function as disclosed.¹⁷ Sweegen argued that the claim language of the patents at issue covered “at least one trillion enzymes that could potentially perform [the claimed] function.”¹⁸ Only one enzyme was given as a representative species, and no common structure of the genus was known at the time of the patent’s priority date.¹⁹ Because genus claimed was “enormous,” and “the one enzyme disclosed in the patents here has not been shown to be typical of the entire genus . . . claimed[,]” the court invalidated the patents for lack of written description.²⁰

District courts, too, continue to grapple with the bounds of the written description requirement for genus claims. For example, in Teva Pharms. v. Eli Lilly & Co., the district court granted Lilly’s motion for summary judgment in response to Teva’s suit alleging infringement of its patents directed towards a subset of headache-treating antibodies.²¹ Because the size of the genus of antibodies was “unknowable”²² and “[a] reasonable jury could not have found that the Patents-in-Suit disclosed more than one [antibody] within the scope of the Asserted Claims,” the district court agreed that Teva had failed to meet the written description requirement.²³

But in Plexxikon Inc. v. Novartis Pharms. Corp., the district court upheld a jury’s verdict in favor of Plexxikon when asked on appeal by Novartis to invalidate genus patents claiming protein “scaffolds” upon which functional moieties could be bound.²⁴ Despite the patents’ “broad”²⁵ genus and failure to disclose a representative species, their identification of common structural features to the genus, including three requisite chemicals and their arrangement in the disclosed genus,²⁶ was enough to survive appeal. The court left undisturbed the jury’s finding that these common structural features were sufficient to allow a POSA to recognize the members of the genus.²⁷

In Duke Univ. v. Sandoz, Inc., the district court denied Sandoz’s motion for a new trial, upholding the jury’s verdict and stating that a reasonable jury could have concluded that that Allergan’s patent for a genus of prostaglandins contained sufficient written description to satisfy the requirements of § 112.²⁸ Although the patent’s claimed genus contained “billions”²⁹ of potential species, and its written description disclosed none of them,³⁰ its identification of structural features common to the genus was enough to survive appeal.³¹ In the district court’s view, Sandoz failed to meet its burden to demonstrate that no reasonable jury could have concluded that the written description was insufficient.³²

Although the Federal Circuit may have applied a vigorous standard for written description in Juno, certain genus claims have continued to withstand scrutiny, particularly where the written description identifies structural features common to the genus. Practitioners should remain conscious of and strongly emphasize the common structural features of a claimed genus, especially where the patents’ specification is limited in disclosure of representative species. Unless and until the Supreme Court decides to clarify the written description standard, whether the written description of a given invention is sufficient to satisfy § 112(a)’s requirements will remain a fact-intensive inquiry shaped by the Federal Circuit’s guidance in Juno.