Ipsen agreed to acquire Kartos Therapeutics for $450 million upfront, with potential milestones that could total $1.75 billion, to expand its late-stage oncology portfolio. The deal centers on navtemadlin, a Phase 3-stage oral MDM2 inhibitor aiming to restore p53 function in TP53 wild-type myelofibrosis patients with suboptimal response to ruxolitinib. Kartos’ Phase 3 POIESIS program is designed to enroll more than 600 patients across 250 sites, with a potential launch as early as 2028 discussed by management. Ipsen positioned the acquisition as a pipeline reinforcement that adds a clear regulatory pathway and commercial potential. This transaction also highlights ongoing pharma interest in p53-restoration strategies as add-on approaches to established JAK inhibitor standards—particularly for the subset that discontinues due to inadequate response.