AnaptysBio Files A Partial Motion To Dismiss Tesaro's Anticipatory Breach Of Contract Claim In Delaware Chancery Court Related To Pending Litigation Between Anaptys, GSK, And TESARO

AnaptysBio, Inc. (NASDAQ:ANAB), a clinical-stage biotechnology company focused on delivering innovative immunology therapeutics, filed a partial motion to dismiss Tesaro's anticipatory breach of contract claim in Delaware Chancery Court related to pending litigation between Anaptys, GSK, and TESARO, Inc. ("Tesaro") regarding their Collaboration and Exclusive License Agreement ("Collaboration Agreement"), which entitles Anaptys to receive royalties upon sales of Jemperli.

As previously disclosed, Anaptys approached Tesaro to engage in good faith discussions to potentially resolve Anaptys' claims that Tesaro and GSK had breached the Collaboration Agreement. On Nov. 20, 2025, Tesaro, without notice to Anaptys and with discussions ongoing, initiated a lawsuit against Anaptys, claiming that Anaptys had repudiated the Collaboration Agreement and seeking a declaration that Tesaro had not breached.

In response, Anaptys filed its own Complaint in Delaware Chancery Court, requesting a court declaration that Tesaro has materially breached the parties' Collaboration Agreement and that GSK, Tesaro's corporate parent, has tortiously interfered with the Collaboration Agreement.

Further, on Dec. 30, 2025, Anaptys filed a Motion to Dismiss Tesaro's anticipatory breach of contract claim in the same court. The motion, unsealed on Jan. 8, 2026, explains why, as a matter of law, Anaptys has never repudiated the Collaboration Agreement and how Anaptys has only sought to vindicate its contract rights (which cannot be a repudiation). Anaptys' motion also explains why Delaware's anti-SLAPP law applies, as the law exists to prevent strategic lawsuits aimed at deterring good‑faith efforts to assert legal rights, such as Tesaro's lawsuit.

Tesaro and GSK contend that Anaptys' Motion to Dismiss stays all discovery, a contention that Anaptys strongly opposes as the two companies work toward the scheduled July 14-17 trial date. The court is expected to hear Anaptys' Motion to Dismiss by early March pursuant to Delaware's anti-SLAPP law.