AnaptysBio files lawsuit against Tesaro over collaboration breach

AnaptysBio Inc. (NASDAQ: ANAB) filed a complaint in Delaware Chancery Court alleging that Tesaro Inc., a GSK subsidiary, materially breached their collaboration agreement and that GSK tortiously interfered with the contract.

The complaint contends that Tesaro violated exclusivity obligations by participating in clinical trials with PD-1 antagonists that compete with Jemperli, including Keytruda, despite agreeing not to conduct research or development of any PD-1 antagonist other than those licensed by AnaptysBio. The filing also alleges Tesaro failed to use commercially reasonable efforts to obtain optimum commercial return for Jemperli by favoring GSK's antibody-drug conjugate products.

In 2020, AnaptysBio filed a similar complaint against GSK regarding planned clinical trials of Zejula in combination with Keytruda without consent. That dispute resulted in a settlement including cash payment, royalties on Zejula and increased royalties on Jemperli sales.

Tesaro filed its own lawsuit against AnaptysBio on November 20, seeking injunctive relief and claiming AnaptysBio breached the collaboration agreement by improperly alleging Tesaro's breach. The parties agreed to request an expedited schedule with trial anticipated in July 2026.

Under the March 2014 collaboration agreement, AnaptysBio receives tiered royalties on Jemperli sales: 8% on net sales below $1 billion, 12% between $1 billion and $1.5 billion, 20% between $1.5 billion and $2.5 billion, and 25% above $2.5 billion. The company anticipates a $75 million milestone payment once Jemperli achieves $1 billion in worldwide net sales.

Milestone and royalty payments to AnaptysBio continue during the legal proceedings. Currently, Jemperli receivables are payable to Sagard through a monetization agreement until Sagard receives $600 million by March 2031 or $675 million thereafter.

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