Ipsen has struck a definitive agreement to acquire Kartos Therapeutics in a move aimed at strengthening its late-stage oncology portfolio and accelerating development of a promising treatment for Myelofibrosis.

 

At the center of the deal is navtemadlin, an investigational Navtemadlin designed to reactivate the tumor-suppressing function of p53. The drug is being studied as an add-on therapy to standard treatment in patients who respond poorly to existing care.

 

"This acquisition further strengthens our late-stage oncology pipeline and reflects our continued focus on bringing transformational treatments to people living with cancer,” said David Loew, CEO, Ipsen.

 

“We are excited by the potential of navtemadlin to define a new treatment paradigm for patients with myelofibrosis who have a suboptimal response to current standard of care, addressing a critical care gap and offering the potential for a new therapeutic option as early as 2028.”

 

The acquisition targets a major unmet need in myelofibrosis care, where the current standard therapy, Ruxolitinib, can reduce spleen enlargement and symptom burden but fails a significant subset of patients. Those who discontinue treatment often face poor outcomes, with median survival estimated at just 1–2 years.

 

Navtemadlin is currently being evaluated in the global Phase III POIESIS trial, which is enrolling more than 600 patients across over 250 sites. The study is testing the drug as an add-on to ruxolitinib in intermediate- and high-risk TP53 wild-type patients who have shown suboptimal response.

 

Early clinical data from a Phase Ib/II study previously presented at the European Hematology Association Congress showed encouraging signs of activity, including reductions in spleen volume, symptom improvement, and potential disease-modifying effects such as changes in variant allele frequency and bone marrow fibrosis.

 

"As a treating clinician who cared for more than a thousand patients with myelofibrosis, I have seen first-hand the significant care gap for patients with myelofibrosis who remain symptomatic or have persistent splenomegaly despite ruxolitinib treatment. 

 

"Navtemadlin has the potential to enhance the existing standard of care through an add-on approach designed to move patients with a suboptimal response into a clinical responder group by optimizing their care. 

 

"We believe this innovative treatment paradigm could meaningfully improve outcomes for patients while avoiding unnecessary over-treatment of those already responding well," said Srdan Verstovsek, Chief Medical Officer of Kartos Therapeutics, commented

 

Experts in blood cancers also pointed to the broader implications of combination therapy approaches. 

 

“Myelofibrosis remains a serious and rare blood cancer associated with a substantial symptom burden and progressive splenomegaly that significantly impact quality of life,” said John Mascarenhas, affiliated with Icahn School of Medicine at Mount Sinai. 

 

“The clinical rationale for combining navtemadlin with ruxolitinib is very compelling, and the emerging data suggest the synergistic potential to deepen responses and address the underlying biology of the disease.”