A French pharmaceutical company is spending up to $1.75 billion to acquire an American biotechnology firm and add a promising treatment for a rare blood cancer to its lineup. The deal, announced on Sunday the 28th of June, represents one of the most significant acquisitions in the cancer drug development space so far this year.
Ipsen, which is headquartered in Paris and listed on the Euronext stock exchange, has agreed to buy Kartos Therapeutics, a privately held company based in Redwood City in the United States state of California. The initial payment will be $450 million in cash at the point of completion. Beyond that, Kartos shareholders stand to receive additional payments of up to $1.3 billion. Those payments are tied to specific future events. The largest is linked to receiving formal regulatory approval for the drug at the centre of the deal. Others are linked to reaching certain levels of sales.
The total value of the transaction could therefore reach $1.75 billion, though that figure depends on performance targets being met over a number of years. The deal is expected to close by the end of September 2026, pending the usual regulatory checks required under American competition law.
The drug Ipsen is buying the company for is called navtemadlin. It is a tablet taken by mouth. It is still in clinical trials and has not yet been approved for sale in any market. Its target condition is myelofibrosis. This is a form of cancer that affects the bone marrow, the soft tissue inside bones where blood cells are produced. In myelofibrosis, scar tissue builds up inside the marrow, disrupting the normal production of blood cells and causing the spleen to enlarge as it tries to compensate. The condition can cause severe fatigue, pain, breathlessness and significant reductions in quality of life. It is considered rare and disproportionately affects older adults.
The current standard treatment for myelofibrosis is a drug called ruxolitinib. It helps many patients but does not work equally well for everyone. A substantial number of patients do not respond adequately to ruxolitinib or eventually stop responding to it over time. Navtemadlin is being developed specifically for those patients. Clinical trial data shows it works as an additional treatment given alongside ruxolitinib in patients with intermediate and high-risk forms of the disease who are not getting sufficient benefit from ruxolitinib alone.
The way navtemadlin works is scientifically distinct from most existing cancer treatments. It targets a protein called MDM2 that effectively acts as a brake on the body’s own natural defence against tumours. Healthy cells contain a protein called p53 whose job is to suppress tumour growth. In many cancer cells, MDM2 is overactive and blocks p53 from doing that job. Navtemadlin inhibits MDM2, releasing p53 to restore its natural tumour suppressing function. This mechanism is specific enough to be of interest in several types of blood cancer, and Kartos has been investigating it in myelofibrosis as well as in other related conditions including polycythaemia vera and acute myeloid leukaemia.
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David Loew, the chief executive of Ipsen, said navtemadlin could become a new treatment option for myelofibrosis patients as early as 2028. He described the acquisition as strengthening the company’s late-stage cancer drug pipeline and as consistent with Ipsen’s focus on delivering what he called transformational treatments to people living with cancer.
Ipsen’s finance team said the deal is expected to begin contributing positively to the company’s core operating profit from 2029 onward. For the current financial year, the impact on profitability is expected to be limited. The deal is structured in a way that front-loads risk for Ipsen but protects it from overpaying if the drug does not reach the commercial milestones that would trigger the larger additional payments.
As Reuters reported in its coverage of the announcement, the acquisition continues a period of active expansion for Ipsen in the cancer space. In October last year, the company agreed to buy the French biotechnology company ImCheck Therapeutics in a deal worth up to one billion euros, focused on a new class of cancer antibodies. That transaction was aimed at adding earlier stage research capabilities. The Kartos deal by contrast is focused squarely on a single late-stage drug that could be ready for regulatory submission in the near future.
Kartos Therapeutics was founded to develop treatments for blood cancers and had navtemadlin as its central programme. The company employed approximately 66 people at its last reported headcount. Goldman Sachs and PJT Partners acted as financial advisers to Kartos’s shareholders during the negotiations.
For patients with myelofibrosis who do not respond well to current treatment, the prospect of a new option reaching the market within two years is the most significant aspect of the deal. For Ipsen, the acquisition is a bet that navtemadlin will clear the remaining regulatory steps and that the market for blood cancer drugs will sustain the valuations being attached to it.
About the Author
Marcel Chidozie is a tech analyst and writer covering foreign news, fintech, and emerging technologies at TechRegard. Based in Nigeria, He's passionate about translating complex tech developments into compelling, accessible stories for diverse audiences. His work focuses on how technology shapes innovation across Africa and globally.
