REG - GSK PLC - Initiation of litigation against AnaptysBio Inc

GSKAnnouncement

21/11/2025 07:00

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RNS Number : 4514I  GSK PLC  21 November 2025

Issued: 20 November 2025, London UK

 

TESARO, a GSK subsidiary, initiates litigation against AnaptysBio, Inc.

 

 

GSK plc (LSE/NYSE: GSK) subsidiary, TESARO, Inc., confirms it has initiated
litigation against AnaptysBio, Inc. in the Delaware Chancery Court. This
action contends that recent conduct by AnaptysBio is in material breach of the
existing license agreement with TESARO regarding the oncology treatment
Jemperli (dostarlimab). The breach entitles TESARO to terminate the current
license agreement, obtain a perpetual and irrevocable license to dostarlimab,
and to reduce the royalties and milestone payments due by TESARO to AnaptysBio
by 50%.

 

TESARO has initiated this litigation following allegations made by AnaptysBio
that TESARO has not fulfilled certain requirements of the license agreement
entered in March 2014 and that AnaptysBio intends to revoke TESARO's licence
for dostarlimab. GSK and TESARO are firmly of the view that these allegations
are entirely without merit.

 

Jemperli is currently approved in over 35 countries for use in certain
endometrial cancers, the most common gynaecologic cancer in the United States.
GSK and TESARO have reported significant growth for Jemperli driven by label
expansions in endometrial cancer, including in the US and EU. A robust and
ambitious clinical trial programme to evaluate the potential use of
dostarlimab in additional cancers, including rectal, colon and head and neck,
is ongoing.

 

About GSK

GSK is a global biopharma company with a purpose to unite science, technology,
and talent to get ahead of disease together. Find out more at gsk.com.

 

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Cautionary statement regarding forward-looking statements

GSK cautions investors that any forward-looking statements or projections made
by GSK, including those made in this announcement, are subject to risks and
uncertainties that may cause actual results to differ materially from those
projected. Such factors include, but are not limited to, those described in
the "Risk Factors" section in GSK's Annual Report on Form 20-F for 2024, and
GSK's Q3 Results for 2025.

 

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