GSK unit and AnaptysBio trade lawsuits over Jemperli

GSK has escalated a dispute over rights to its cancer immunotherapy Jemperli, after its subsidiary Tesaro filed a complaint against AnaptysBio in the Delaware Court of Chancery, alleging breach of contract.

The lawsuit has resulted in a swift response from AnaptysBio, which almost immediately filed its own complaint arguing that Tesaro has – under pressure from GSK – unlawfully modified the terms of their agreement on the product, which dates back to 2014.

PD-1 inhibitor Jemperli (dostarlimab) was originally discovered by AnaptysBio and licensed to Tesaro before its merger with GSK in 2019 in a $5.1 billion deal. It is a major contributor to GSK's oncology business, with sales nearly doubling to £600 million ($783 million) in the first nine months of the year, driven by recent approvals in the US and Europe for primary advanced or recurrent endometrial cancer.

In its lawsuit, Tesaro is asking the Delaware court to agree that breaches of the 2014 licensing deal mean that it can end the current contract, retain a perpetual licence to dostarlimab, and cut the royalty and milestone payments it owes AnaptysBio in half.

AnaptysBio, meanwhile, is asserting that Tesaro has failed to meet the obligations of their agreement, including that it would not conduct or participate in "research, development, manufacturing, or commercialisation" of any PD-1 antagonist other than those licensed by AnaptysBio to Tesaro.

Specifically, that refers to running clinical trials of GSK/Tesaro drugs – including antibody-drug conjugates (ADCs) – in combination with PD-1 inhibitors that compete with Jemperli, like MSD's Keytruda (pembrolizumab).

It also suggests that Tesaro has not made the required effort to "obtain the optimum commercial return" for Jemperli in markets around the world. GSK said it is running a "robust and ambitious" clinical trial programme to evaluate the potential use of dostarlimab in additional indications, including rectal, colon, and head and neck cancers.

In a statement, GSK and Tesaro said they are "firmly of the view that these allegations are entirely without merit."

The two lawsuits follow suggestions that AnaptysBio has been preparing to revoke Tesaro's license for dostarlimab, which first reached the market in 2021 and, along with various indications in endometrial cancer, is also used to treat mismatch repair-deficient (dMMR) recurrent or advanced solid tumours.

Friction between the companies over Jemperli dates back to 2020, when AnaptysBio filed a complaint against GSK over its intention to test its PARP inhibitor Zejula (niraparib) alongside Keytruda, rather than Jemperli. That resulted in a cash settlement to AnaptysBio, plus a royalty on Zejula sales and an increase in royalties paid on Jemperli.

Photo by engin akyurt on Unsplash