Holding: Disclosure of a broad genus does not provide adequate written description for a narrower subgenus or species unless the specification includes reasonably specific support showing possession of that narrower scope.
Seagen owns US Patent No. 10,808,039 which claims an antibody-drug conjugate (ADC) for treatment of cancer. An ADC typically includes an antibody, a cytotoxic drug, and a linker protein that connects the antibody and the drug. Independent claim 1 of the ‘039 Patent claims an ADC that includes a linker with a tetrapeptide, a chain of four amino acids. The claimed tetrapeptide is a Gly/Phe-only tetrapeptide, where each amino acid is either glycine or phenylalanine. Glycine is able to exist in only a single spatial arrangement, while phenylalanine can exist in two different spatial arrangements, creating a total of 81 different species in the claimed tetrapeptide subgenus.
In November 2011, Daiichi invented an ADC used to treat cancer and marketed under the name Enhertu®. Enhertu® includes a Gly/Phe-only tetrapeptide with the sequence Gly-Gly-Phe-Gly. The structure and the mechanism of action of Enhertu® were publicly disclosed in December 2015. The ’039 Patent was filed in July 2019 and claims priority to US Application No. 10/983,340, which was filed in November 2004. The ‘340 Application describes an ADC with an antibody, a drug moiety, and a linker protein with a peptide unit that connects the antibody and drug moiety. However, the ‘340 Application does not explicitly disclose the Gly/Phe-only tetrapeptide that is claimed in the ‘039 Patent. Therefore, Enhertu® is prior art to the ‘039 Patent, unless Seagen could show that the ‘340 Application provided support for the claimed Gly/Phe-only tetrapeptide.
Seagen filed suit against Daiichi for infringement of the ‘039 Patent in October 2020. In December 2020, Daiichi petitioned for post-grant review (PGR) of the ‘039 Patent. At the district court, the jury found that the ‘340 Application provided written description support for a Gly/Phe-only tetrapeptide, and the ‘039 Patent was entitled to the November 2004 priority date of the ‘340 Application. The jury also found that Enhertu® infringed the ‘039 Patent. Daiichi moved for JMOL, but this motion was denied. However, in the concurrent PGR proceeding, the PTAB issued a final written decision holding the claims of the ‘039 Patent to be unpatentable.
To be able to claim priority to an earlier application’s priority date, the previous application must provide a written description. This description must reasonably convey to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date. Daiichi argued that no reasonable jury could have found that the ‘340 Application sufficiently disclosed the Gly/Phe-only tetrapeptide subgenus claimed in the ‘039 Patent. The ‘340 Application discloses that the peptide unit can be any of many types of peptides, such as a dipeptide, tripeptide, tetrapeptide, up to a dodecapeptide. The ‘340 Application also discloses 83 different options for amino acids that may be included in the peptide. Therefore, the ‘340 Application discloses over 47 million different types of tetrapeptide units. The Federal Circuit held that this broad disclosure is not sufficient for the ‘340 Application to provide adequate written description for the ‘039 Patent.
A disclosure of a broad genus, without more, is not sufficient to provide written description for claims that are limited to a particular subgenus or species. Claims to a particular species or subgenus require reasonably specific disclosure to show that the inventor possessed that invention at the time of the filing date. In this case, the ‘039 Patent claims 81 specific tetrapeptides of the 47 million that are disclosed in the ‘340 Application. Absent a more specific disclosure related to those 81 tetrapeptides, the ‘340 Application cannot provide adequate written description for the claims of the ‘039 Patent. Therefore, the Federal Circuit held that the ‘039 Patent could not claim priority to the ‘340 Application, and Daiichi’s public disclosure of Enhertu® in 2015 acts as prior art that invalidates the ‘039 Patent.
Seagen argued that the ‘340 Application would direct a skilled artisan to the claimed Gly/Phe-only tetrapeptide subgenus. The ‘340 Application provided a specific example of a Gly-Phe-Leu-Gly (GFLG) tetrapeptide, and Seagen’s expert testified that it would have been a “straightforward leap” for the skilled artisan to modify the GFLG tetrapeptide to a GFFG tetrapeptide that would be covered by the claimed Gly/Phe-only tetrapeptide subgenus. However, the Federal Circuit stated that the fact that a skilled artisan would have to make a “leap” to come up with the claimed subgenus proves that the ‘340 Application itself did not actually disclose the claimed peptide.
In addition to finding a lack of written description, the Federal Circuit also held that the ‘039 Patent did not meet the enablement requirement. Enablement requires that a patent’s specification describe the invention in a way that allows a person of skill in the art to make and use the invention. The specification must enable the full scope of the invention as described by the claims without requiring undue experimentation. In addition to the claimed tetrapeptide, claim 1 of the ‘039 Patent also recited that the ADC includes a drug moiety that is intracellularly cleaved in a patient from the antibody. This would require a skilled artisan to perform assays to determine whether an ADC met this functional limitation, a trial and error process too large and unpredictable to fall under the scope of reasonable experimentation.
Federal Circuit Precedential 
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