GSK subsidiary TESARO receives court ruling in AnaptysBio dispute

GSK plc subsidiary, TESARO, Inc., confirmed on April 27, 2026, that the Delaware Chancery Court has granted AnaptysBio, Inc.'s motion to dismiss TESARO's claim for anticipatory breach.

The court's ruling, however, does not address the merits of the principal contractual dispute between the parties. It also does not impact TESARO's remaining claim against AnaptysBio for a declaratory judgment. GSK and TESARO maintain that AnaptysBio's allegations are without merit and intend to pursue their claim at trial.

TESARO initiated the litigation following allegations by AnaptysBio that TESARO had not fulfilled certain requirements of a license agreement entered into in March 2014. AnaptysBio had stated its intention to revoke TESARO's license for dostarlimab.

Dostarlimab, marketed as Jemperli, is approved in over 35 countries for specific types of endometrial cancer. GSK and TESARO have reported significant growth for Jemperli, driven by expanded approvals for endometrial cancer in the US and EU. A clinical trial program is ongoing to evaluate dostarlimab's potential in other cancers, including rectal, colon, and head and neck cancers.