US court rules against GSK in dispute with AnaptysBio

27th Apr 2026 07:51

(Sharecast News) - A US court has granted a motion to dismiss filed by biotech AnaptysBio in a dispute with GSK's oncology unit, it was confirmed on Monday.

Tesaro launched litigation against AnaptysBio in November, claiming it was in breach of its agreement regarding cancer treatment Jemperli. AnaptysBio countersued, and filed the partial motion to dismiss in January.

Dan Faga, chief executive of AnaptysBio, said: "The court's decision affirms what we have maintained from the beginning: Tesaro's anticipatory breach claim was baseless, and this ruling is an important validation of our efforts to protect our contractual rights to the Jemperli royalty stream for our shareholders."

However, GSK insisted that the ruling - made by the Delaware Chancery Court - did not address the merits of the principal contractual dispute between the parties, and that it had no impact on Tesaro's remaining claim against AnaptysBio for declaratory judgement.

"GSK and Tesaro are firmly of the view that these allegations are entirely without merit and remain focused on pursuing that claim at trial," it concluded.

AnaptysBio and Tesaro, which GSK acquired in 2019, signed the agreement to develop and sell Jemperli, the brand name for dostarlimab, in 2014. Jemperli is currently approved in over 35 countries for use in certain endometrial cancers.

However, Tesaro has accused AnaptysBio of breaching the agreement, thereby allowing it to terminate the deal, reduce royalty and milestone payments and secure a permanent licence to the drug.

AnaptysBio has countersued, accusing Tesaro of violating exclusivity terms.

Earlier in April, AnaptysBio became a royalty management company after it spun off its biopharma business as First Tracks Biotherapeutics. Its business is now focused on two specific deals, with GSK for Jemperli and with American firm Vanda Pharmaceuticals for imsidolimab.

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