Ipsen completes Kartos Therapeutics acquisition

Ipsen announced on 21 August 2026 that it has completed the acquisition of Kartos Therapeutics, a clinical-stage biopharmaceutical company. The acquisition adds navtemadlin, a late-stage MDM2 inhibitor in Phase III development for myelofibrosis, to Ipsen's oncology pipeline. Under the merger agreement, Ipsen made an upfront payment of $450 million, with potential additional milestone payments of up to $1.3 billion plus sales-related milestones. Navtemadlin is being studied as an add-on to ruxolitinib for patients with suboptimal response, aiming to improve clinical outcomes. The acquisition strengthens Ipsen's late-stage oncology pipeline and addresses an unmet need in myelofibrosis.