Ipsen Completes Acquisition of Kartos and Strengthens Its Myelofibrosis Portfolio
The biopharmaceutical laboratory has closed the acquisition of American company Kartos Therapeutics, adding navtemadlin to its portfolio, an experimental treatment for myelofibrosis then in phase III trial.
Ipsen Integrates Navtemadlin, an Oral MDM2 Inhibitor
Ipsen announced on August 21, 2026 that it had completed the acquisition of Kartos Therapeutics, a clinical-stage biopharmaceutical company. The transaction brings to the group navtemadlin, an oral MDM2 inhibitor in development for myelofibrosis.
The candidate is being studied in combination with ruxolitinib in patients with myelofibrosis showing a response deemed suboptimal to this standard treatment. The phase III POIESIS study aims to determine whether the addition of navtemadlin improves clinical outcomes compared to ruxolitinib administered alone in this population.
According to the group, early clinical data indicate that navtemadlin could transform suboptimal ruxolitinib responses into clinically significant responses in intermediate-risk and high-risk patients with wild-type TP53 status. Ipsen points to a potential disease-modifying benefit, in addition to improved clinical outcomes.
The acquisition comes one month after a clinical setback for the laboratory, which had announced on July 24, 2026 the failure of its phase III BOLD trial on Bylvay in biliary atresia, a rare pediatric liver disease.
Myelofibrosis: Frequent Treatment Interruptions with Standard Therapy
Myelofibrosis is a myeloproliferative neoplasm frequently linked to alterations in the JAK/STAT pathway, in which patients develop bone marrow fibrosis. The decline in bone marrow function shifts blood production to other organs, most often the spleen, leading to splenomegaly, with a risk of transformation into acute myeloid leukemia.
The median age at diagnosis is between 67 and 69 years, and the disease affects approximately 1.5 persons per 100,000 in the United States and Europe. Between 75 and 89% of patients present with intermediate or high-risk disease at diagnosis, and more than 95% have wild-type TP53 status.
Ruxolitinib, a JAK inhibitor, is the standard first-line treatment. According to the press release, a significant proportion of patients nonetheless presents an initial suboptimal response, and approximately 50 to 75% discontinue treatment after three years.
Median overall survival is generally one to two years after treatment discontinuation, a point highlighted by the group to justify the need for new therapeutic strategies.
Ipsen Continues Its Development in Oncology
Ipsen (Euronext: IPN; ADR: IPSEY) is a biopharmaceutical company active in three therapeutic areas: oncology, rare diseases and neurosciences. The group indicates that it relies on centers located in the United States, France and the United Kingdom, with teams present in more than 40 countries.
This acquisition is part of a busy sequence for the laboratory. On July 30, 2026, it had raised its annual guidance, with expected growth beyond 20% and operating margin targeted above 37%.
