Study of TdT-3 cell therapy safety in patients aged 1 year and older with relapsed or refractory acute leukemia or lymphoblastic lymphoma

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What is this study about?

This clinical trial studies the use of TdT-3, a special type of cell therapy that uses a patient’s own modified immune cells, in treating acute lymphoblastic leukemia or lymphoblastic lymphoma. These are serious blood cancers that have not responded to standard treatments or have returned after previous treatment. The therapy involves taking the patient’s own T-cells (a type of immune cell), modifying them in a laboratory to better recognize and fight cancer cells, and then returning them to the patient through an infusion into the bloodstream.

The purpose of this study is to test the safety of TdT-3 treatment and determine the most appropriate dose to use in future studies. Before receiving the cell therapy, patients will be given two medications called Fludarabine and Cyclophosphamide to prepare their body for the treatment. The treatment involves collecting the patient’s blood cells through a procedure called leukapheresis, processing these cells in a laboratory to create the TdT-3 therapy, and then giving the modified cells back to the patient.

During the study, doctors will closely monitor patients for any side effects and check how well the treatment works. They will take blood samples and perform various tests to track the modified cells in the body and measure the patient’s response to the treatment. The study will also look at how long the beneficial effects of the treatment last and whether patients can proceed to other treatments like stem cell transplantation if needed.

1 Initial blood collection

Your blood cells will be collected through a procedure called leukapheresis. This requires having at least 150 T-cells per microliter in your blood.

A pregnancy test will be performed within 24 hours before the procedure if applicable.

2 Preparation period

Your collected cells will be processed in a laboratory to create the TdT-3 treatment.

During this time, your health status will be monitored to ensure you are ready for the next phase.

3 Pre-treatment conditioning

You will receive two medications: Fludarabine and Cyclophosphamide to prepare your body for the treatment.

A pregnancy test will be performed before starting this phase if applicable.

4 TdT-3 treatment

The TdT-3 treatment will be given through an infusion into your vein.

The dose will be given in separate portions (fractionated doses) to ensure safety.

5 Monitoring period

You will be monitored for 28 days after the treatment to check for any side effects.

Regular tests will be performed to measure the treatment’s effectiveness.

Blood and bone marrow samples will be collected to track the TdT-3 cells in your body.

Your quality of life will be assessed through questionnaires at day 28.

6 Long-term follow-up

Follow-up visits will occur at 3, 6, 9, 12, and 24 months after treatment.

These visits will include health assessments and quality of life questionnaires.

Your immune system recovery will be monitored during this period.

Who Can Join the Study?

Must be at least 1 year old at screening
Must have adequate T-cell recovery (at least 100 CD4+ T cells in blood) from previous therapy
For children under 6 years and first 3 patients: must have an identified stem cell donor
Must be able to undergo a blood filtering procedure called leukapheresis with at least 150 T cells per microliter of blood
If previously had stem cell transplant: must be at least 100 days since transplant and 30 days since last donor lymphocyte treatment
If previously had CAR T-cell therapy: must be at least 30 days since last treatment
Women who can become pregnant must have negative pregnancy test within 24 hours before key procedures
Must have life expectancy of at least 3 months
Must have suitable blood cells collected through leukapheresis for manufacturing treatment
Must have leukemia or lymphoma that has either not responded to standard treatments or no standard treatments are available
Cancer cells must show presence of TdT protein in testing
Must have specific genetic marker (HLA-A*02:01) and tumor cells must express HLA-A2
Must have measurable disease either in bone marrow or visible tumors on scans
Must provide written informed consent (parents/guardians for minors)
Must have adequate physical function score (Lansky or Karnofsky score ≥50)
Must have adequate kidney, liver, lung, and heart function based on medical tests
Must not have significant heart rhythm problems

Who Cannot Join the Study?

History of other types of cancer (except non-melanoma skin cancer) in the past 2 years
Active central nervous system (brain and spinal cord) involvement with leukemia
Uncontrolled infections that require intravenous antibiotics or antifungal medications
Severe heart conditions including:
- Heart failure with symptoms
- Unstable heart rhythm problems
- Recent heart attack (within 6 months)
Severe liver problems with abnormal test results
Severe kidney problems requiring dialysis
Pregnancy or breastfeeding
Known HIV infection (Human Immunodeficiency Virus)
Active hepatitis B or C infection
Previous treatment with similar cell therapy within the last 6 months
Mental health conditions that could affect ability to understand or follow study requirements
Any other serious medical condition that could make participation unsafe

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

Site Name	City	Country	Status
Oslo Universitetssykehus HF	Oslo	Norway

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
Norway	Not yet recruiting	01.10.2025

Trial locations

TdT-3 is an experimental cell therapy that uses a patient’s own modified T-cells (a type of immune cell). The T-cells are genetically modified to recognize and target cells expressing TdT, which is found in certain types of leukemia and lymphoma. This is a personalized treatment where the patient’s own immune cells are collected, modified in a laboratory, and then given back to the patient.

Fludarabine is a chemotherapy medication used as part of the preparation treatment (conditioning) before receiving the cell therapy. It helps prepare the body by suppressing the immune system to help the modified T-cells work better.

Cyclophosphamide is also a chemotherapy medication used alongside Fludarabine in the conditioning treatment. Like Fludarabine, it helps prepare the body for the cell therapy by suppressing the immune system and creating space for the new modified T-cells to grow.

Acute lymphoblastic leukemia (ALL) – A type of blood cancer that affects white blood cells called lymphocytes in the bone marrow. The disease develops when young lymphocytes grow too quickly and don’t mature properly, leading to an accumulation of immature cells. These abnormal cells crowd out healthy blood cells in the bone marrow and can spread to other parts of the body. The condition typically develops quickly, over days or weeks.

Lymphoblastic lymphoma (LBL) – A rare cancer that develops from immature lymphocytes, similar to ALL, but primarily affects lymph nodes and other tissues rather than the bone marrow. The disease causes lymph nodes to become enlarged as abnormal lymphocytes accumulate within them. It can also affect other organs such as the spleen, liver, and sometimes the skin. The condition shares many biological features with ALL but manifests differently in the body.

Trial ID:

2024-519320-24-00

Protocol code:

TDT-TCR01

Trial Phase:

Phase I and Phase II (Integrated) – First administration to humans

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Study of TdT-3 cell therapy safety in patients aged 1 year and older with relapsed or refractory acute leukemia or lymphoblastic lymphoma

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