Seagen Inc. v. Daiichi Sankyo, Inc., Astrazeneca Pharmaceuticals Lp

N OTE: This disposition is nonprecedential.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 T ONNIES HORTON, Willkie Farr & Gallagher LLP,
Chicago, IL, argued for appellant. Also represented by
D EVON WESLEY EDWARDS , New York, NY; D ANE SOWERS ,
Case: 24-1878 Document: 68 Page: 1 Filed: 12/02/2025

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SEAGEN INC. v. DAIICHI SANKYO, INC. 2
Washington, DC.
P RESTON K. RATLIFF , II, Paul Hastings LLP, New York,
NY, argued for appellees. Also represented by J USTIN
F LEISCHACKER , L UCAS L. K RESSEL ; STEPHEN BLAKE
K INNAIRD, N AVEEN M ODI, I GOR VICTOR T IMOFEYEV , D ANIEL
ZEILBERGER , Washington, DC.
SHEHLA WYNNE, Office of the Solicitor, United States
Patent and Trademark Office, Alexandria, VA, argued for
intervenor. Also represented by P ETER J. AYERS , MARY L.
K ELLY , WILLIAM L AMARCA , N ICHOLAS T HEODORE MATICH ,
IV.
CHRISTOPHER N EIL SIPES , Covington & Burling LLP,
Washington, DC, for appellee AstraZeneca Pharmaceuti-
cals LP. Also represented by BRADLEY K EITH ERVIN,
N ICHOLAS L ANE EVOY , ROBERT J ASON F OWLER.
______________________
Before L OURIE, REYNA , and CHEN, Circuit Judges.
L OURIE, 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: 2 Filed: 12/02/2025

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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
Case: 24-1878 Document: 68 Page: 3 Filed: 12/02/2025

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