Ipsen is buying Kartos Therapeutics for $450 million upfront to acquire navtemadlin (an MDM2-targeting p53 reactivator) as Kartos’ Phase 3 program advances in myelofibrosis. The oral small molecule is intended to improve outcomes for patients who stop or underperform on standard JAK therapy. Ipsen said the acquisition is meant to pad its pipeline and potentially deliver the next-generation option in the intermediate and high-risk TP53 myelofibrosis population, with a Phase 3 topline expected next year.