Press Release

Ipsen completes acquisition of Kartos Therapeutics, strengthening late-stage Oncology pipeline

PARIS, FRANCE, 21 AUGUST 2026 - Ipsen (Euronext: IPN; ADR: IPSEY) announced today it has completed the acquisition of Kartos Therapeutics, a clinical-stage biopharmaceutical company adding late-stage MDM2 inhibitor navtemadlin in Phase III clinical development in myelofibrosis.

About navtemadlin

Navtemadlin is an investigational oral MDM2 inhibitor being developed as an add-on therapy to ruxolitinib for patients with myelofibrosis who have a suboptimal response to ruxolitinib. The Phase III POIESIS study is evaluating whether the addition of navtemadlin could improve clinical outcomes compared with ruxolitinib alone in this patient population. Early clinical data demonstrate navtemadlin has the potential to transform suboptimal responses to standard of care ruxolitinib into clinically meaningful responses in patients with intermediate and high risk TP53wt myelofibrosis, to provide both enhanced clinical outcomes and potential disease-modifying benefit.

About myelofibrosis

Myelofibrosis is a myeloproliferative neoplasm, frequently linked to alterations in the JAK/STAT pathway, in which patients develop bone marrow fibrosis due to the abnormal proliferation of hematopoietic stem cells and secretion of fibrogenic cytokines. As marrow function declines, blood production shifts to other organs, most often the spleen, leading to splenomegaly. Myelofibrosis is characterized by bone marrow failure, fibrosis, splenomegaly and a high symptom burden that can significantly affect quality of life, including fatigue, night sweats and other progressive symptoms. It also carries a risk of transformation to acute myeloid leukemia. The median age at diagnosis is approximately 67–69 years and the condition affects around 1.5 per 100,000 people in the U.S. and Europe. Approximately 75–89% of patients are intermediate- or high-risk at diagnosis and more than 95% are TP53wt. Ruxolitinib, a JAK inhibitor, is the first-line standard of care; however, it is estimated that a significant proportion of patients have an initial suboptimal response and approximately 50%-75% discontinue treatment after three years. Median overall survival is typically one to two years after treatment discontinuation, underscoring the need for new strategies that can increase the number of patients that can achieve optimal clinical outcomes.

About Ipsen

We are a global biopharmaceutical company with a focus on bringing transformative medicines to patients in three therapeutic areas: Oncology, Rare Disease and Neuroscience. Our pipeline is fueled by internal and external innovation and supported by nearly 100 years of development experience and global hubs in the U.S., France and the U.K. Our teams in more than 40 countries and our partnerships around the world enable us to bring medicines to patients in more than 100 countries. Ipsen is listed in Paris (Euronext: IPN) and in the U.S. through a Sponsored Level I American Depositary Receipt program (ADR: IPSEY). For more information, visit ipsen.com.

Ipsen Contacts

Investors

Henry Wheeler henry.wheeler@ipsen.com +33 7 66 47 11 49
Khalid Deojee khalid.deojee@ipsen.com +33 6 66 01 95 26

Media

Sally Bain sally.bain@ipsen.com +1 857 320 0517
Anne Liontas anne.liontas.ext@ipsen.com +33 7 67 34 72 96

Disclaimers and/or forward-looking statements

The forward-looking statements, objectives and targets contained herein are based on Ipsen’s management strategy, current views and assumptions. Such statements involve known and unknown risks and uncertainties that may cause actual results, performance or events to differ materially from those anticipated herein. All of the above risks could affect Ipsen’s future ability to achieve its financial targets, which were set assuming reasonable macroeconomic conditions based on the information available today. Use of the words ‘believes’, ‘anticipates’ and ‘expects’ and similar expressions are intended to identify forward-looking statements, including Ipsen’s expectations regarding future events, including regulatory filings and determinations. Moreover, the targets described in this document were prepared without taking into account external-growth assumptions and potential future acquisitions, which may alter these parameters. These objectives are based on data and assumptions regarded as reasonable by Ipsen. These targets depend on conditions or facts likely to happen in the future, and not exclusively on historical data. Actual results may depart significantly from these targets given the occurrence of certain risks and uncertainties, notably the fact that a promising medicine in early development phase or clinical trial may end up never being launched on the market or reaching its commercial targets, notably for regulatory or competition reasons. Ipsen must face or might face competition from generic medicine that might translate into a loss of market share. Furthermore, the research and development process involves several stages each of which involves the substantial risk that Ipsen may fail to achieve its objectives and be forced to abandon its efforts with regards to a medicine in which it has invested significant sums. Therefore, Ipsen cannot be certain that favorable results obtained during preclinical trials will be confirmed subsequently during clinical trials, or that the results of clinical trials will be sufficient to demonstrate the safe and effective nature of the medicine concerned. There can be no guarantees a medicine will receive the necessary regulatory approvals or that the medicine will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from