Ipsen Acquires Kartos Therapeutics for $450M, Bolstering Its Oncology Portfolio
The biopharmaceutical group Ipsen announced on Monday the acquisition of biotech firm Kartos Therapeutics for an initial amount of $450M. This move allows it to incorporate navtemadlin, an advanced-stage drug candidate targeting myelofibrosis, a rare blood disease, with preliminary efficacy data deemed promising.
A Strategic Acquisition in Rare Oncology
Ipsen has signed a definitive agreement to acquire Kartos Therapeutics, announced on Monday, June 29, 2026. The acquisition price is set at $450M at closing. Additional milestone payments, which could reach up to $1.3 billion, are also planned for Kartos shareholders, including a significant regulatory milestone and sales-related milestones. The transaction is expected to close before the end of the third quarter of 2026, subject to approval by U.S. antitrust authorities (Hart-Scott-Rodino Antitrust Improvements Act). According to the group, the operation will be accretive to current operating income starting in 2029, with limited dilution to the 2026 financial outlook.
Navtemadlin, a Phase III MDM2 Inhibitor Against Myelofibrosis
The main asset acquired, navtemadlin, is an oral MDM2 inhibitor currently being evaluated as a complementary treatment to ruxolitinib in patients with suboptimal response to myelofibrosis. The Phase III POIESIS clinical trial, the primary registration program, is based on encouraging earlier data. During the Phase Ib/II trial (KRT-232-109), navtemadlin added to ruxolitinib showed significant activity in poorly responding patients. At week 24, among 19 patients, 42% achieved at least a 25% reduction in spleen volume and 32% achieved at least a 35% reduction. The product also demonstrated potentially disease-modifying activity: 71% of evaluable patients (n=7) achieved at least a 20% reduction in the allelic frequency of driver mutations and 57% showed an improvement in bone marrow fibrosis of grade ≥1. Phase III POIESIS data, involving more than 600 patients at over 250 sites, are expected in 2027.
Myelofibrosis and Unmet Therapeutic Need
Myelofibrosis is a rare myeloproliferative neoplasm affecting approximately 1.5 individuals per 100,000 inhabitants in North America and Europe. Ruxolitinib, a JAK inhibitor, is the standard treatment for this blood disease. However, a significant proportion of patients do not respond adequately to ruxolitinib, and about 50 to 75% discontinue treatment after three years. Following discontinuation of ruxolitinib, outcomes are severe with a median overall survival of 1 to 2 years, highlighting the urgent need for new therapeutic strategies.
