Ipsen agreed to acquire Kartos Therapeutics for $450 million upfront, with potential milestones up to $1.3 billion, securing navtemadlin—an oral MDM2 inhibitor aimed at restoring p53 function. Navtemadlin is in Phase 3 for intermediate and high-risk TP53 wild-type myelofibrosis as an add-on to ruxolitinib, with Ipsen describing a regulatory pathway and an active Phase 3 program.