ANAPTYSBIO, INC

On November 20, 2025, we filed a Verified Complaint in Delaware Chancery Court, requesting a court declaration that TESARO, Inc. (“Tesaro”) has materially breached the parties’ Collaboration and Exclusive License Agreement (“Collaboration Agreement”) and that GSK, Tesaro’s corporate parent, has tortiously interfered with the Collaboration Agreement. We have requested that the court declare that we are entitled to all rights and remedies under the Collaboration Agreement.

While we had approached Tesaro to engage in good faith discussions to potentially resolve these claims, on November 20, 2025, Tesaro, without notice, initiated a lawsuit against us. Tesaro’s complaint includes a request for a declaration that it has not breached the Collaboration Agreement and for an injunction prohibiting AnaptysBio from terminating the Collaboration Agreement. Tesaro also alleges that AnaptysBio has materially breached the agreement, entitling Tesaro to exercise certain rights and remedies under the agreement. Tesaro’s claim for breach is predicated on an allegation that AnaptysBio improperly alleged that Tesaro had breached the Collaboration Agreement, which allegedly caused an anticipatory breach of contract. Through that claim, we believe that Tesaro seeks to improperly punish us for and restrain us from exercising our legal rights under the Collaboration Agreement in violation of Delaware’s anti-SLAPP statute. We believe that Tesaro’s claims are entirely without merit and have moved to dismiss the anticipatory breach claim.