Legal disputes escalated between AnaptysBio and Tesaro (a GSK subsidiary) as both parties filed competing lawsuits over licensing rights and revenue tied to Jemperli. GSK/Tesaro moved to terminate the agreement and seek a permanent license, alleging material breaches; Anaptys countersued in Delaware Chancery Court arguing Tesaro materially breached the collaboration and tortiously interfered. Anaptys has also amended a stock repurchase plan and highlighted the financial importance of preserving royalty streams tied to Jemperli sales. The litigation centers on commercialization rights and testing strategies that affect milestone and royalty flows.