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Study of gene-modified stem cells (FT024) in children with TCIRG1-related osteopetrosis using treosulfan, thiotepa, and plerixafor for treatment

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is studying a treatment for children with autosomal recessive osteopetrosis, a rare genetic bone disease caused by mutations in the TCIRG1 gene. The condition causes bones to become unusually dense and prone to breaks. The study aims to evaluate a new treatment that uses modified stem cells from the patient's own body. The treatment involves collecting blood-forming stem cells from the patient, modifying them in a laboratory to correct the genetic defect, and then returning them to the patient through an infusion.

The main treatment being tested is called FT024, which consists of specially processed stem cells that have been modified using a lentiviral vector (a tool that delivers genetic material into cells). Several other medications will be used as part of the treatment process, including Trecondi (treosulfan), Tepadina (thiotepa), and Mozobil (plerixafor). These medications help prepare the body for the stem cell treatment.

The study will monitor patients for two years after treatment to check if the modified stem cells successfully integrate into the body and improve the condition. Doctors will track various health measures, including blood cell counts, need for blood transfusions, bone health, and overall survival. The treatment's safety will be closely monitored throughout the study period.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial preparation

    Your eligibility for the study has been confirmed based on the following criteria: you have autosomal recessive osteopetrosis caused by mutations in the TCIRG1 gene, you are between 28 days and 2 years old, and your body weight is at least 4 kg.

    The medical team will collect your stem cells (specifically CD34+ cells) for the treatment preparation.

  2. Step 2

    Cell preparation

    Your collected stem cells will be modified in a laboratory using a special technique to correct the genetic defect.

    The modified cells will be expanded (multiplied) to reach the required amount for treatment.

  3. Step 3

    Pre-treatment medication

    You will receive Trecondi (treosulfan) through an intravenous infusion.

    Tepadina (thiotepa) will be administered through an intravenous infusion.

    Mozobil (plerixafor) will be given as an injection under the skin.

  4. Step 4

    Cell infusion

    The modified stem cells will be given back to you through an intravenous infusion.

    Additional infusions ('boost') may be given if needed for your recovery.

  5. Step 5

    Follow-up monitoring

    Regular check-ups will occur at 1, 2, 3, 6, 9, 12, 18, and 24 months after the cell infusion.

    During these visits, blood tests will be performed to monitor your recovery.

    Your quality of life will be assessed at the start of treatment, and after 12 and 24 months.

Who can join the trial?

11 criteria

  • Patient must have a confirmed diagnosis of autosomal recessive osteopetrosis caused by mutations in the TCIRG1 gene, proven by either:
    • Clinical features of the disease and documented genetic changes in the TCIRG1 gene that cause severe infantile osteopetrosis
    • OR presence of severe symptoms such as:
      • Increased bone density throughout the body
      • Abnormally shaped long bones
      • Thickened skull base
      • Frequent bone fractures
      • Bone infections
      • Problems with vision or hearing due to nerve compression
      • Decreased bone marrow function
      • Patient must be between 28 days and 2 years old
      • Patient must weigh at least 4 kilograms (kg)
      • Both male and female patients can participate

Who cannot join the trial?

15 criteria

  • Active or uncontrolled infections that could interfere with the treatment
  • Major organ damage (such as severe heart, lung, liver or kidney problems)
  • Known HIV (Human Immunodeficiency Virus) infection
  • Active hepatitis B or hepatitis C infection
  • Previous unsuccessful bone marrow transplant or gene therapy
  • Participation in another clinical trial within the last 30 days
  • Any medical condition that could make the treatment unsafe
  • Inability to comply with study procedures and follow-up visits
  • Known allergies to medications used in the study
  • Pregnancy or breastfeeding
  • Mental conditions that prevent understanding of the study requirements
  • Blood disorders that could affect treatment success
  • Active cancer or history of cancer in the past 5 years
  • Severe neurological complications
  • Any condition that could interfere with the evaluation of study results
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Investigated drugs

TCIRG1 LVV-transduced hematopoietic stem cells are cells taken from the patient's own blood or bone marrow that have been modified in a laboratory. These cells are genetically altered using a special virus (lentiviral vector) to carry a corrected version of the TCIRG1 gene. This therapy is designed to treat a rare bone condition called autosomal recessive osteopetrosis by helping the body produce properly functioning bone cells. This is a cell and gene therapy where the patient's own stem cells are collected, modified, and then returned to their body. The modified cells are intended to help correct the genetic defect that causes the bone disease.

What is already known about the treatment

TCIRG1 LVV-transduced HSPCs - A gene therapy treatment involving hematopoietic stem and progenitor cells (HSPCs) that have been modified outside the body using a lentiviral vector to carry the TCIRG1 gene. The treatment is administered through intravenous infusion after the patient's own cells have been collected, modified, and expanded in the laboratory. This investigational therapy is currently being studied in clinical trials for children with autosomal recessive osteopetrosis caused by TCIRG1 gene mutations, a severe bone disorder. The modified cells are designed to produce the correct version of the TCIRG1 protein, which is essential for proper bone development and remodeling, potentially helping to restore normal bone formation and breakdown processes in affected patients.

Investigated diseases

Autosomal Recessive Osteopetrosis (ARO-1) – A rare genetic bone disorder caused by mutations in the TCIRG1 gene that affects how the body breaks down and rebuilds bone tissue. In this condition, bones become abnormally dense and hard, but they are actually more fragile than normal bones. The disease typically appears in early infancy and causes bones to grow abnormally throughout the body. This leads to various bone-related problems and can affect the formation of bone marrow cavities. The condition also impacts the blood-forming system, as the abnormally thick bones interfere with normal bone marrow function.
Trial detailsLast updated 2 Oct 2026
Age0-17PhasePhase I/IITrial ID2024-518972-30-00Estimated enrolment8 patientsSponsorFondazione Telethon Ets

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

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