Ipsen agreed to acquire Kartos Therapeutics for $450 million upfront and up to $1.75 billion total, securing late-stage blood cancer asset navtemadlin, a p53-restoring oral MDM2 inhibitor. The deal centers on navtemadlin’s Phase 3 POIESIS trial, evaluating it as add-on therapy to ruxolitinib in intermediate- and high-risk TP53 wild-type myelofibrosis after suboptimal JAK inhibitor response. Kartos framed the strategy around addressing a care gap: many patients discontinue therapy within a few years due to inadequate responses. Ipsen positioned the acquisition as a way to strengthen its late-stage oncology pipeline and add a clearly defined regulatory path. For investors and competitors, the acquisition also highlights the market’s focus on p53 pathway modulation as an intensification layer beyond JAK inhibition, with POIESIS targeting more than 600 patients across 250+ sites and potential launch timing as early as 2028.