Ipsen agreed to buy Kartos Therapeutics in a deal valued at $450 million upfront, with potential milestone payments up to $1.75 billion, to add navtemadlin—an MDM2 inhibitor in Phase 3—to its oncology pipeline. The drug is being evaluated as an add-on to ruxolitinib in intermediate- and high-risk TP53 wild-type myelofibrosis with suboptimal response. The Phase 3 POIESIS trial is designed to enroll more than 600 patients across 250-plus sites, positioning navtemadlin for a potential 2028 launch if results support efficacy. Ipsen framed the acquisition as strengthening its late-stage oncology pipeline and expanding beyond earlier oncology assets. For investors, the deal also reflects a continuing willingness to pay for late-stage assets that can fit into existing standard-of-care combinations, especially in disease areas with unmet durability needs.