GSK and AnaptysBio Enter Legal Dispute Over Jemperli License Amid Allegations of Contract Breaches

TESARO, a GSK subsidiary, has initiated litigation against AnaptysBio in the Delaware Chancery Court, arguing that AnaptysBio's recent actions constitute a material breach of their license agreement for the oncology drug Jemperli (dostarlimab)1 2 3 4 5 8.

The alleged breach, according to TESARO, would allow them to terminate the existing agreement, secure a perpetual and irrevocable license for dostarlimab, and reduce royalties and milestone payments to AnaptysBio by 50%1 2.

This legal move follows claims by AnaptysBio that TESARO itself failed to comply with certain terms of the license, with AnaptysBio seeking to revoke TESARO’s license to market Jemperli1 2 3 5 8.

Both companies have publicly rejected each other's allegations, with GSK and TESARO maintaining that AnaptysBio's claims are entirely without merit1 2.

The litigation centers around the financial and commercial stakes in Jemperli, which is approved in over 35 countries for certain endometrial cancers and has seen significant growth after label expansions1 2 11.

The dispute has affected AnaptysBio’s share price and put future royalty payments from Jemperli at risk7.

Jemperli remains a key product for both companies, with multiple ongoing clinical trials for expanded indications beyond endometrial cancer1 11.

GSK has advised investors that projections regarding Jemperli and the litigation are subject to risk and uncertainty, as stated in their forward-looking cautionaries1 2.