AnaptysBio files lawsuit against Tesaro and GSK over license deal

November 26, 2025 4:05 PM EST

AnaptysBio Inc. (NASDAQ: ANAB) filed a lawsuit in Delaware Chancery Court claiming Tesaro Inc. materially breached their collaboration and exclusive license agreement, according to a company filing.

The complaint, initially filed November 20 and made public November 26, also alleges that GlaxoSmithKline, Tesaro's parent company, tortiously interfered with the collaboration agreement. AnaptysBio seeks a court declaration that it is entitled to all rights and remedies under the agreement.

Tesaro and GSK responded by filing their own complaint against AnaptysBio on November 26, claiming AnaptysBio breached the collaboration agreement. The case is captioned as Tesaro, Inc. and Tesaro Development, Ltd. v. AnaptysBio, Inc., in Delaware Chancery Court.

The dispute centers on a collaboration and exclusive license agreement between the parties, though specific details of the alleged breaches were not disclosed in the filing. AnaptysBio included a copy of its complaint as an exhibit to its Form 8-K filing with the Securities and Exchange Commission.



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