Jan 8 (Reuters) – AnaptysBio said on Thursday it filed a partial motion to dismiss a claim by GSK’s oncology unit, which alleges the biotech breached their contract, escalating a legal dispute over royalties tied to sales of the cancer drug Jemperli.
The dispute centers on a 2014 agreement between AnaptysBio and oncology unit Tesaro that gave the latter rights to develop and sell Jemperli, a PD-1 inhibitor approved for certain endometrial cancers.
GSK did not immediately respond to Reuters’ request for a comment outside business hours.
A trial to resolve claims is scheduled for July 14–17, 2026, and the court is expected to hear AnaptysBio’s motion by early March.
Tesaro filed a lawsuit against AnaptysBio in a Delaware court on November 20, accusing it of breaching the agreement and arguing that the alleged breach allowed Tesaro to terminate the deal, halve royalty and milestone payments, and secure a permanent license to the drug.
AnaptysBio countersued a day later, accusing Tesaro of violating exclusivity terms by participating in trials of rival PD-1 drugs, including Merck’s Keytruda, and failing to fully maximize Jemperli’s commercial potential.
It also alleged that GSK interfered with the agreement by favoring its antibody-drug conjugate programs over Jemperli.
Under the license, Anaptys is entitled to tiered royalties: 8% on annual net sales below $1 billion, 12% on sales between $1 billion and $1.5 billion, 20% on sales from $1.5 billion to $2.5 billion, and 25% on sales above $2.5 billion. Royalty payments are set to continue at least until key patents expire in 2035 in the United States and 2036 in the European Union.
(Reporting by Puyaan Singh in Bengaluru; Editing by Sherry Jacob-Phillips)
