TESARO update on AnaptysBio Inc. litigation

Summary by AI ^BETAClose X

GSK plc's subsidiary, TESARO, Inc., has received an update on its litigation with AnaptysBio, Inc., as the Delaware Chancery Court granted AnaptysBio's motion to dismiss TESARO's claim for anticipatory breach. This ruling does not affect TESARO's ongoing claim for declaratory judgment, which GSK and TESARO intend to pursue at trial, maintaining their belief that AnaptysBio's allegations are without merit. The dispute originated from AnaptysBio's claims that TESARO failed to meet license agreement requirements and its intention to revoke TESARO's license for dostarlimab, the active ingredient in GSK's Jemperli, a drug approved in over 35 countries for certain endometrial cancers and undergoing further clinical trials for other cancer types.

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GSK PLC

27 April 2026

Issued: 27 April 2026, London UK

TESARO, a GSK subsidiary, provides update on AnaptysBio, Inc. litigation

GSK plc (LSE/NYSE: GSK) subsidiary, TESARO, Inc., confirms that the Delaware Chancery Court has granted the motion to dismiss filed by AnaptysBio, Inc. against TESARO's claim for anticipatory breach. The court's ruling does not address the merits of the principal contractual dispute between the parties and has no impact on TESARO's remaining claim against AnaptysBio for declaratory judgment. GSK and TESARO are firmly of the view that these allegations are entirely without merit and remain focused on pursuing that claim at trial.

TESARO initiated this litigation following allegations made by AnaptysBio that TESARO has not fulfilled certain requirements of the license agreement entered in March 2014 between the parties and that AnaptysBio intends to revoke TESARO's licence for dostarlimab.

Jemperli, which is the brand name for dostarlimab, 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.

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