France-based Ipsen (Euronext: IPN; ADR: IPSEY) has agreed to acquire Kartos Therapeutics, a Redwood City, California-based clinical-stage company, in a definitive merger agreement that adds navtemadlin, an oral MDM2 inhibitor in Phase III development for myelofibrosis, to Ipsen's oncology portfolio. The deal gives Ipsen a late-stage hemato-oncology asset that it expects could reach patients as early as 2028, extending its oncology presence beyond its current rare disease and solid tumor focus.
Under the terms of the agreement, Ipsen will pay USD 450 million upfront at closing through a fully owned subsidiary. Kartos shareholders are eligible to receive up to USD 1.3 billion in additional milestone payments, including a significant regulatory approval milestone and sales-based milestones, bringing total potential consideration to USD 1.75 billion. The transaction is expected to close by the end of Q3 2026, subject to expiration of the Hart-Scott-Rodino waiting period and other customary conditions. Ipsen indicated the deal will be accretive to its core operating income from 2029, with limited dilution to 2026 full-year guidance.
Navtemadlin targets the MDM2 protein, which normally degrades p53, a critical tumor suppressor. By inhibiting MDM2, navtemadlin restores p53 function in TP53 wild-type (wt) tumor cells, potentially converting suboptimal responses to ruxolitinib (Jakafi) — the entrenched JAK inhibitor standard of care — into clinically meaningful responses. Phase Ib/II data for navtemadlin in 19 patients with suboptimal ruxolitinib responses showed 42% achieved at least a 25% spleen volume reduction and 71% of evaluable patients achieved a ≥20% reduction in driver variant allele frequency at Week 24, suggesting disease-modifying activity. The ongoing global Phase III POIESIS trial is enrolling more than 600 patients across more than 250 sites, with top-line data expected in 2027.