Case: 24-1878 Document: 68 Page: 1 Filed: 12/02/2025

NOTE: This disposition is nonprecedential.

United States Court of Appeals for the Federal Circuit ______________________

SEAGEN INC., Appellant

v.

DAIICHI SANKYO, INC., ASTRAZENECA PHARMACEUTICALS LP, Appellees

JOHN A. SQUIRES, UNDER SECRETARY OF COMMERCE FOR INTELLECTUAL PROPERTY AND DIRECTOR OF THE UNITED STATES PATENT AND TRADEMARK OFFICE, Intervenor ______________________

2024-1878 ______________________

Appeal from the United States Patent and Trademark Office, Patent Trial and Appeal Board in No. PGR2021- 00030. ______________________

Decided: December 2, 2025 ______________________

SARA TONNIES HORTON, Willkie Farr & Gallagher LLP, Chicago, IL, argued for appellant. Also represented by DEVON WESLEY EDWARDS, New York, NY; DANE SOWERS, Case: 24-1878 Document: 68 Page: 2 Filed: 12/02/2025

2 SEAGEN INC. v. DAIICHI SANKYO, INC.

Washington, DC.

PRESTON K. RATLIFF, II, Paul Hastings LLP, New York, NY, argued for appellees. Also represented by JUSTIN FLEISCHACKER, LUCAS L. KRESSEL; STEPHEN BLAKE KINNAIRD, NAVEEN MODI, IGOR VICTOR TIMOFEYEV, DANIEL ZEILBERGER, Washington, DC.

SHEHLA WYNNE, Office of the Solicitor, United States Patent and Trademark Office, Alexandria, VA, argued for intervenor. Also represented by PETER J. AYERS, MARY L. KELLY, WILLIAM LAMARCA, NICHOLAS THEODORE MATICH, IV.

CHRISTOPHER NEIL SIPES, Covington & Burling LLP, Washington, DC, for appellee AstraZeneca Pharmaceuti- cals LP. Also represented by BRADLEY KEITH ERVIN, NICHOLAS LANE EVOY, ROBERT JASON FOWLER. ______________________

Before LOURIE, REYNA, and CHEN, Circuit Judges. LOURIE, Circuit Judge. The instant case is an appeal from a final written deci- sion of the United States Patent Trial and Appeal Board (“the Board”) in a post-grant review (“PGR”) proceeding holding claims 1–5, 9, and 10 of Seagen Inc.’s (“Seagen”) U.S. Patent 10,808,039 (“the ’039 patent”) invalid. Daiichi Sankyo, Inc. v. Seagen Inc., No. 10,808,039, 2024 WL 168076 (P.T.A.B. Jan. 16, 2024). It is a companion case to Seagen Inc. v. Daichii Sankyo Co., Ltd., Nos. 23-2424, 24- 1176, slip op. (Fed. Cir. 2025), decided by this court today, where we hold that the same claims of the ’039 patent are invalid for lack of adequate written description and enable- ment. Id. at 12, 18. At oral argument, Seagen conceded that a determina- tion of invalidity for the ’039 patent in the companion case Case: 24-1878 Document: 68 Page: 3 Filed: 12/02/2025

SEAGEN INC. v. DAIICHI SANKYO, INC. 3

renders the instant appeal moot. See Oral Arg. at 11:50– 12:08, available at https://www.cafc.uscourts.gov/oral-ar- guments/24-1878_10062025.mp3 (“[P]ractically speaking, if this court invalidates the patent [i]n either appeal . . . then the case would be over.”). That concession is in accord with our case law. XY, LLC v. Trans Ova Genetics, 890 F.3d 1282, 1294 (Fed. Cir. 2018) (invalidity determina- tion renders moot “all pending or co-pending actions”); see also Biogen Int’l GMBH v. Mylan Pharms. Inc., 18 F.4th 1333, 1346 (Fed. Cir. 2021) (declining to “reach the merits of the parties’ arguments in [a] companion IPR case” when claims at issue held invalid on appeal from district court). We thus dismiss Seagen’s appeal of the PTAB’s decision as moot. DISMISSED