PTAB Decision invalidating claims finding lack of written description and later priority date upheld by Federal Circuit

Procedural History

Regents of the University of Minnesota v. Gilead Sciences, Inc., Case No. 2021-2168 (Fed. Cir. Mar. 6, 2023) is an appeal by the Regents of the University of Minnesota (“Minnesota”) from a final written decision of the Patent Trial and Appeal Board (“the Board”) holding that claims 1-9, 11-21, and 23-28 of U.S. Patent 8,815,830 (“the ’830 Patent”) are unpatentable as anticipated by the asserted prior art. The Federal Circuit affirmed.


Gilead Sciences, Inc. (“Gilead”) filed a petition for inter partes review (“IPR”) asserting that several claims of the ’830 Patent were not entitled to their claimed priority date and were anticipated by Gilead’s patent publication, “Sofia”, which the parties agreed disclosed every limitation of the challenged claims. The challenged claims of ’830 Patent were directed to phosphoramidate prodrugs of nucleoside derivatives that prevent viruses from reproducing or cancerous tumors from growing. Within this genus falls Gilead’s drug, sofosbuvir, which is FDA-approved for treating chronic hepatitis C infections.

The application that issued as the ’830 Patent claimed priority from four applications, outlined in the table below:



 U.S. Provisional App. 60/634,677 ("P1")

 Dec. 9, 2004

 Int. App. PCT/US2005/044442 ("NP2")

Dec. 8, 2005 

 U.S. Patent App. 11/721,325 ("NP3")

June 8, 2007 

 Sofia Publication

Jan. 21, 2010 

 U.S. Patent App. 13/753,252 ("NP4")

Jan. 29, 2013 

The Board held that NP2-P1 failed to provide written description sufficient to support the ’830 Patent’s priority claim and found that NP2 and NP3 contained the same disclosure. According to the Board, “these documents contained neither ipsis verbis support nor sufficient blaze marks to guide the skilled artisan to the claims of the ’830 patent. Thus, the challenged claims were not entitled to a priority date earlier than their own filing date of March 28, 2014. They were thus anticipated by Sofia.” (Slip Op. at 5) (citation omitted). The key issue Minnesota raised on appeal was whether the Board erred in holding that NP2-P1 did not show a written description of what is claimed in the ’830 Patent.1


“Written description of an invention claimed as a genus of chemical compounds [] raises particular issues because [] written description of a broad genus requires description not only of the outer limits of the genus but also of either a representative number of members of the genus or structural features common to the members of the genus, in either case with enough precision that a relevant artisan can visualize or recognize the members of the genus.” (Slip Op. at 6.) The Court acknowledged that Minnesota was not arguing it described a sufficient number of species to constitute written description of the claimed subgenus, but instead, that “its earlier NP2-P1 applications literally described, or provided blaze marks to, the subgenus of the ’830 claims . . . .” (Slip Op. at 6.) However, the Court did not agree that Minnesota did either.

First, Minnesota asserted that combining seven claims found in NP2-P1, each containing R substituents with multiple variables, provided an ipsis verbis disclosure of the subgenus claimed in the ’830 Patent. The Board was not persuaded, and the Court agreed, stating, “[f]ollowing this maze-like path, each step providing multiple alternative paths, is not a written description of what might have been described if each of the optional steps had been set forth as the only option.” (Slip Op. at 8.)  The Court further stated, “. . . the listings of possibilities are so long, and so interwoven, that it is quite unclear how many compounds actually fall within the described genera and subgenera.” (Slip Op. at 9.)

Second, Minnesota asserted that NP2-P1 provided sufficient blaze marks to provide written description support. The Board evaluated “whether one of skill in the art would have been able to visualize or recognize the members of the claimed genus by searing for blaze marks that guide a skilled artisan to the claimed subgenera” and found that they would not.  (Slip Op. at 11.) The Court agreed with the Board, stating that “the structures here are so extensive and varied that the structures of NP2-P1 claim 47, which, through its multiple dependencies, encompasses a significantly larger genus than that claimed in the ’830 patent, are not sufficiently common to that of claim 1 of the ’830 patent to provide written description support.” (Slip Op. at 11.)

Ultimately, the Court agreed with the Board’s conclusion that NP2-P1 do not provide sufficient written description to support the ’830 Patent claims. (Slip Op. at 11.) And, because NP3 provides the same disclosure as NP2, it also did not provide sufficient written description to support the ’830 Patent claims.  (Slip Op. at 11.) Therefore, the Court upheld the Board’s determination that the claims of the ’830 Patent were “entitled to a priority date no earlier than March 28, 2014, making Sofia prior art to them.” (Slip Op. at 11.)


Key Takeaways

  1. Sufficiently describing a genus under Ariad requires a description of a claimed genus disclosing either (1) “a representative number of species falling within the scope of the genus,” or (2) “structural features common to the members of the genus,” either of which must enable one of skill in the art “to visualize or recognize the members of the genus.”
  2. Patent disclosures with multiple structures so extensive and varied, through multiple dependencies, and encompassing a significantly large genus, may be inadequate to provide written description support under the Federal Circuit’s “blaze marks” analysis.
  3. Common structural features between chemical structures in a claim and a putative priority disclosure should be present in such a manner that a skilled artisan can visualize the near-entirety of the claimed structure.


The other two issues were (i) whether there was an Administrative Procedure Act violation and (ii) whether Minnesota was entitled to sovereign state entity immunity from IPR.  The Court rejected both arguments.

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