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Phase 3 Safety and Efficacy Trial of FLT201 Gene Therapy in Patients with Gaucher Disease Type 1 Using Drug Combination

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What is this trial about?

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

The study focuses on Gaucher Disease Type 1, a rare inherited condition in which the body lacks enough of the enzyme that breaks down a fatty substance called glucocerebroside. Without this enzyme, fat builds up in the spleen, liver, bones and blood, leading to anemia, low platelet counts, enlarged organs, and bone problems. The investigational treatment is a one‑time infusion of FLT201, a form of gene therapy that uses a harmless virus to deliver a working copy of the gene that makes the missing enzyme, beta-glucocerebrosidase. Participants may continue their usual medicines such as the oral solution containing sirolimus, the hard capsules with tacrolimus, the injectable form of methylprednisolone, and the tablet form of prednisolone while receiving the study drug.

The main aim of the trial is to see whether the single infusion of FLT201 can keep blood‑cell levels, spleen and liver size, and bone health stable over a year. After the infusion, participants attend regular clinic visits for about 12 months during which blood tests, imaging scans, and questionnaires are used to monitor safety and how well the therapy works. The study tracks changes in blood counts, organ volumes, enzyme activity, and quality‑of‑life measures without exposing participants to any unnecessary procedures.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment

    After you agree to take part, you are officially enrolled in the study and assigned a study identification number.

  2. Step 2

    Baseline assessments

    A series of tests are performed before any study medication is given. these include blood tests, urine tests, a physical examination, imaging of the spleen and liver, and questionnaires about your health and quality of life.

    You may continue taking your usual medicines such as sirolimus (rapamune oral solution), tacrolimus (tacforius capsules), prednisolone tablets, and methylprednisolone injection, unless your doctor advises otherwise.

  3. Step 3

    Gene therapy infusion

    You receive a single intravenous infusion of the study drug flt201, a gene therapy product. the infusion contains 2,000,000,000,000 vector genomes per millilitre and is administered in one session.

  4. Step 4

    Immediate post‑infusion monitoring

    After the infusion you remain in the clinic for observation. staff check your vital signs, watch for any immediate reactions, and may repeat selected laboratory tests.

  5. Step 5

    Regular follow‑up visits

    You attend scheduled visits over the next 52 weeks. at each visit blood samples are taken to measure hemoglobin, platelet count, enzyme activity of beta‑glucocerebrosidase, and other safety laboratory values.

    Imaging studies are repeated to assess spleen volume and liver volume. questionnaires are completed to evaluate your quality of life and fatigue levels.

    Any side effects or health changes are recorded, and additional safety tests such as electrocardiograms may be performed as needed.

  6. Step 6

    Final assessment at week 52

    At the 52‑week visit the primary and secondary outcomes are evaluated. the stability of your hemoglobin level, platelet count, and organ sizes are compared with the baseline results.

    The study team also reviews long‑term safety data, including any adverse events that occurred during the year.

Who can join the trial?

6 criteria

  • Be at least 18 years old when screened for the study.
  • Have a confirmed medical diagnosis of Gaucher disease type 1.
  • Show a stable hemoglobin level at the start of the trial (hemoglobin is the part of blood that carries oxygen).
  • Show a stable platelet count at the start of the trial (platelets are tiny cells that help blood clot).
  • Be receiving either enzyme replacement therapy (ERT) or substrate reduction therapy (SRT) without any breaks for at least two years.
  • Meet any other study‑specific inclusion requirements that are defined in the trial protocol.

Who cannot join the trial?

8 criteria

  • Having Gaucher disease type 2 or type 3, which are more severe forms of the condition – this makes you ineligible.
  • Testing positive for AAVS3 neutralizing antibodies, which are proteins that can block the study drug from working.
  • Having abnormal lab test results, health conditions, or other diseases that could make participation unsafe.
  • Having a positive pregnancy test or being lactating (breast‑feeding).
  • Having a history of a hematopoietic stem cell transplant or bone marrow transplant, or any solid organ transplant (surgery to replace an organ such as a kidney or liver).
  • Having received any gene therapy or cell therapy before, which are treatments that change genetic material or use specially modified cells.
  • Having had a total removal of the spleen (total splenectomy).
  • Any other reasons defined by the study protocol that would prevent participation.
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Investigated drugs

  • Rapamune oral solution

    is a liquid medicine taken by mouth that contains sirolimus. Sirolimus helps suppress the immune system, which can be important for patients who have had organ transplants or need to reduce immune activity. In this trial, it is used as part of the standard background treatment to keep the immune system from reacting strongly.

  • Methylprednisolone injectable solution

    is a steroid given by injection into a vein. It contains methylprednisolone hydrogen succinate, which reduces inflammation and calms an over‑active immune response. In the study, it is used as a background medication to control inflammation that can occur in Gaucher disease.

  • FLT201 gene therapy

    is the experimental treatment being tested. It is a one‑time infusion of a specially designed virus (an adeno‑associated viral vector) that carries a copy of the human beta‑glucocerebrosidase gene. This gene helps the body produce the missing enzyme that causes Gaucher disease, aiming to improve the body’s ability to break down certain fats and reduce disease symptoms.

  • Tacforius hard capsules

    contain tacrolimus, an oral medication that also suppresses the immune system. It is taken as a prolonged‑release capsule, meaning the drug is released slowly over time. In the trial, it is part of the background regimen to help keep the immune system from reacting against the gene therapy.

  • Prednisolone soluble tablets

    are oral tablets that contain prednisolone, another steroid that reduces inflammation and immune activity. These tablets dissolve easily in the mouth and are used as background therapy to manage inflammation and support overall treatment stability during the study.

What is already known about the treatment

  • Rapamune 1 mg/mL oral solution

    This medication is taken by mouth as a liquid oral solution. Sirolimus is an approved immunosuppressant that is widely used in transplant patients and certain rare diseases. It works by blocking the mTOR pathway, which stops signals that tell immune cells to grow and divide. It is classified as a macrolide immunosuppressant.

  • METHYLPREDNISOLONE VIATRIS 1 g, poudre pour solution injectable (I.V.)

    This product is a powder that is reconstituted and given by intravenous infusion. Methylprednisolone hydrogen succinate is an approved corticosteroid used to reduce inflammation and suppress the immune system. It binds to glucocorticoid receptors inside cells and changes gene activity to lower inflammatory chemicals. It belongs to the glucocorticoid class of drugs.

  • FLT201

    The drug is supplied as a sterile solution for infusion and is administered intravenously. FLT201 is an investigational gene‑therapy product that is currently being studied in clinical trials and has not yet received market approval. It carries a modified adeno‑associated virus that delivers a functional copy of the human beta‑glucocerebrosidase gene, allowing patients’ cells to produce the missing enzyme needed in Gaucher disease type 1. It is classified as a gene‑therapy vector.

  • Tacforius 1 mg prolonged-release hard capsules

    This medication comes as hard capsules that are swallowed whole. Tacrolimus is an approved immunosuppressant used mainly to prevent organ rejection after transplantation. It inhibits the calcineurin enzyme, which stops T‑cells from becoming active and reduces immune responses. It is classified as a calcineurin inhibitor.

  • Prednisolone 5mg Soluble Tablets

    The drug is provided as soluble tablets that are taken by mouth. Prednisolone is an approved corticosteroid used to treat inflammation and various autoimmune conditions. It works by binding to glucocorticoid receptors and altering gene expression to suppress inflammatory pathways. It belongs to the glucocorticoid class.

Investigated diseases

Gaucher disease type 1 - Gaucher disease type 1 is an inherited disorder caused by a deficiency of the enzyme beta‑glucocerebrosidase, leading to the accumulation of fatty substances called glucocerebroside in certain cells. This buildup enlarges the spleen and liver, reduces blood cell counts, and can cause bone pain, fractures, and reduced bone density. The condition usually progresses slowly, with symptoms appearing in childhood or adulthood and gradually worsening over many years. It does not involve the central nervous system, distinguishing it from other forms of Gaucher disease.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-520765-50-00Protocol codeFLT201-03Estimated enrolment45 patientsSponsorSpur Therapeutics Limited

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