A historic breakthrough in the fight against cancer
Scientists have reached a major milestone: for the first time, anti-cancer immune cells have been produced directly inside a patient’s body, without prior extraction or laboratory manipulation. This breakthrough, reported notably by Doctissimo, concerns what are known as in vivo CAR-T cells — a new generation of immunotherapy that could profoundly transform the treatment of many cancers, including pediatric cancers.
What is CAR-T cell therapy?
Since 2018, CAR-T therapy has been approved in Europe to treat certain blood cancers in children and young adults, particularly acute lymphoblastic leukemia and some lymphomas. The principle is to collect the patient’s T lymphocytes (white blood cells that play a key role in the immune system), genetically modify them in the laboratory so they can recognize and destroy cancer cells, and then reinfuse them into the patient.
This treatment has already enabled remissions in cases where chemotherapy had failed.
However, this process has significant limitations:
- A long manufacturing time (4 to 6 weeks), during which the child’s condition may worsen
- Very high costs, often around €1 million
- Complex logistics, requiring shipment to specialized laboratories in Europe
- Limited accessibility for many families worldwide
The in vivo CAR-T revolution: the body as a laboratory
This new research approach overcomes many of these constraints. Instead of extracting and modifying cells outside the body, researchers have developed targeted delivery systems — particularly lipid nanoparticles (similar to those used in mRNA COVID-19 vaccines) or viral vectors — capable of introducing genetic instructions directly into T lymphocytes inside the body.
In practical terms, a simple injection could be enough to reprogram a patient’s immune cells, enabling them to identify and attack tumor cells. According to studies published in Nature and Science in 2025, this approach has already demonstrated proof of concept in animal models and early phase 1 clinical trials.
Why is this particularly important for pediatric cancers?
Children with cancer face specific challenges: their developing bodies respond differently to treatments, treatment timelines can be critical, and families face immense psychological and logistical burdens.
Any advancement that can shorten treatment timelines, reduce costs, and expand access to innovative therapies represents real hope for thousands of children and their families.
In vivo CAR-T therapies could eventually transform a treatment currently limited to a few specialized hospitals into a much more widely accessible therapy.
Where does the research stand?
Early clinical trials in humans are currently underway. Kelonia Therapeutics notably presented encouraging data in late 2025 at the American Society of Hematology congress on patients treated with an in vivo CAR-T therapy targeting multiple myeloma.
In France, the UNITC consortium, which includes the Institut Carnot OPALE — specialized in pediatric cancers — is actively working to structure a national research ecosystem around these therapies.
While the road to widespread clinical application remains long, the scientific foundations are now solid.
What progress is being made for pediatric cancers?
Cell therapies such as CAR-T are rapidly expanding in oncology, sometimes showing spectacular results, including for very advanced cancers. However, children still have limited access to these treatments.
In 2024, 1,369 adult patients benefited from these therapies in France, compared with only 25 children (source: PMSI SCO).
To make these therapies a reality in pediatric oncology, Imagine for Margo has funded seven major research programs aimed at optimizing their use, particularly for childhood brain tumors.
Among these are two large-scale clinical trials using CAR-T cells to treat relapsed neuroblastoma and leukemia.
At Imagine for Margo, our mission is to fund research and innovation in pediatric cancers to cure more children and improve treatments. Our role is also to inform families and the general public about the most promising advances and to support them.
Every discovery like this brings us one step closer to a world where no child dies from cancer.
📖 Source: Doctissimo