GSK, Anaptysbio sue each other over Jemperli revenue

Core Viewpoint - Anaptysbio and GSK are engaged in a legal dispute over alleged breaches of contract related to the marketing of the cancer immunotherapy Jemperli, with both companies filing lawsuits against each other [1][2]. Group 1: Legal Dispute - Anaptysbio claims GSK violated their decade-old agreement by testing its experimental cancer drugs alongside competitors of Jemperli, such as Merck's Keytruda [2]. - GSK initiated the lawsuit first, asserting that Anaptysbio's actions constituted a material breach of the license agreement, seeking to terminate the agreement and reduce royalties owed to Anaptysbio [4]. - Anaptysbio's countersuit alleges that GSK's testing of other PD-1 drugs before Jemperli breached the terms of their license [4]. Group 2: Background of the Agreement - The lawsuits stem from a 2014 deal between Anaptysbio and Tesaro, which licensed Jemperli, a PD-1 inhibitor similar to Keytruda and Opdivo [3]. - GSK acquired Tesaro in 2019 for $5.1 billion, primarily for the ovarian cancer drug Zejula, but also recognized the potential of Jemperli [3]. Group 3: Financial Implications - Jemperli generated sales of approximately $785 million through the first nine months of 2025, with projections to reach $1 billion by year-end [6]. - Anaptysbio stands to receive a $75 million milestone payment and royalties of 8% on sales up to $1 billion, increasing to 12% on sales between $1 billion and $1.5 billion [6].