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Safety and efficacy of AAV2/8 vector delivering human ARSB gene with prednisone and methylprednisolone in pediatric MPS VI patients – Phase I/II extension

Registered drugNo placebo
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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 children with Mucopolysaccharidosis type VI, a rare condition where the body cannot break down certain complex sugars, leading to buildup that can affect joints, heart, and eyes. Participants will receive a single intravenous infusion of the experimental gene therapy called FT005, which uses an aden-associated viral vector serotype 2/8 containing the human ARSB gene to deliver a working copy of the missing enzyme to the liver. Standard background medicines such as prednisone and methylprednisolone may be given to help control inflammation. The purpose of the study is to evaluate the safety and potential benefit of this approach.

After an initial screening visit, the child will come to the clinic for the infusion, which takes a short time. Over the following months, regular check‑ups will include simple urine tests that measure urinary GAGs (substances that indicate disease activity), a walking assessment called the 6-minute walk test to see how far the child can walk, and breathing tests such as forced vital capacity to evaluate lung function. Additional routine examinations, like eye checks and heart monitoring, will be performed to watch for any side effects. The study continues with periodic visits for up to several years to gather information on safety and how the therapy may improve the child’s health.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Begin Background Oral Prednisone

    You will start taking prednisone by mouth as a background medication for the study. The specific dose, how often you will take it, and the length of treatment are determined by the study protocol.

    Prednisone is a type of steroid that helps reduce inflammation and is used to support your safety while you receive the gene therapy.

  2. Step 2

    Receive Background Intravenous Methylprednisolone

    You will receive methylprednisolone through an intravenous (IV) line. This medication is also a steroid and is given to further protect you during the gene‑therapy treatment.

    The exact dose, frequency, and duration of the IV methylprednisolone are specified in the study protocol.

  3. Step 3

    Receive Gene‑Therapy Infusion

    You will be given a single intravenous infusion of the test product, an adeno‑associated viral vector serotype 2/8 that carries the human arsb gene. The product is provided as a solution for infusion.

    The infusion is performed by a qualified health‑care professional and is the core treatment being evaluated in the trial. Details about the exact amount infused and the length of the infusion are defined by the study protocol.

  4. Step 4

    Participate in Ongoing Safety and Efficacy Evaluations

    After the infusion, you will attend scheduled visits during which the study team will check for any side effects, including dose‑limiting toxicities, adverse events, and serious adverse events.

    You will undergo various examinations such as abdominal ultrasound, eye examinations, tests for antibodies against the ARSB protein, and cardiac assessments (ECG and echocardiography).

    Your ability to walk for six minutes and climb stairs for three minutes will be measured, as will lung function tests called forced vital capacity (FVC) and forced expiratory volume in one second (FEV1).

    You will complete a health‑assessment questionnaire (HAQ or CHAQ) to report how you feel and function.

    Urine samples will be collected on three consecutive days to measure urinary glycosaminoglycans (GAGs), which help determine how well the gene therapy is working.

    All of these evaluations are performed according to the study schedule, which is outlined in the trial protocol.

Who can join the trial?

4 criteria

  • You have a confirmed diagnosis of MPS VI based on laboratory tests that show the missing enzyme (a biochemical test) and a DNA test that finds the gene change (a molecular test).
  • You are between 5 and 16 years old, including the ages of 5 and 16.
  • You have been receiving enzyme replacement therapy (ERT) for at least 12 months before joining the study, and you will keep taking it until about 7‑14 days before the study drug is given.
  • You or your legal guardian have signed a written informed consent form, showing you understand the study, agree to follow the study rules (protocol), and will take part in the long‑term follow‑up visits.

Who cannot join the trial?

14 criteria

  • Cannot or will not follow the study requirements.
  • Has taken systemic corticosteroid therapy (steroid medicines that affect the whole body) or other immunosuppressive/immunomodulating drugs (medicines that lower the immune system) within 2 months before receiving the gene‑therapy product.
  • Is a woman of child‑bearing age who is pregnant, nursing, or unable to use reliable birth control for at least one year after the treatment.
  • Is a fertile man who does not agree to use male barrier contraception such as a condom.
  • Has any other health condition that would prevent completing follow‑up visits, as judged by the doctor.
  • Shows a detectable level of serum NAB to AAV8 (antibodies in the blood that could block the gene‑therapy virus) during screening.
  • Has participated in another clinical study with an investigational drug in the past 6 months, or joins another study while in this trial.
  • Is unable to perform the 6‑minute walk test (6MWT) (a test measuring how far a person can walk in six minutes).
  • Has a history of a severe anaphylactoid reaction (a serious allergic‑like response) to Naglazyme (the enzyme‑replacement therapy for MPS VI) that caused life‑threatening breathing problems.
  • Has a tracheostomy (a tube placed in the windpipe) or needs ventilatory assistance (machine‑helped breathing).
  • Shows evidence of progressive myelomalacia (softening of the spinal cord) that is likely to require neck surgery within the first six months after enrollment.
  • Has blood test results with AST or ALT (liver enzymes) higher than the normal range.
  • Has other chronic diseases or laboratory values that are clearly abnormal and could affect the study.
  • Is infected with hepatitis B, hepatitis C, or HIV (viral infections) at the time of screening.
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Investigated drugs

  • Prednisone

    is an oral medication that belongs to a group of drugs called corticosteroids. It helps reduce inflammation and suppresses the immune system. In this trial, prednisone is given to participants as part of the standard background treatment to manage symptoms related to their condition.

  • Adeno‑associated viral (AAV) serotype 8 vector with liver‑specific thyroxin‑binding globulin (TBG) promoter, driving the expression of the human ARSB gene

    is a gene‑therapy product. It is delivered through an intravenous infusion and works by using a harmless virus to carry a healthy copy of the ARSB gene into liver cells. Once inside the cells, the gene produces the missing enzyme that patients with Mucopolysaccharidosis type VI need, aiming to improve their disease symptoms.

  • Methylprednisolone

    is an intravenous corticosteroid. Like prednisone, it reduces inflammation and calms an overactive immune response. In this study, methylprednisolone is provided as part of the background care to help control inflammation during the trial.

What is already known about the treatment

  • Prednisone

    This medication is taken by mouth as a tablet. It is an approved and widely used corticosteroid that helps reduce inflammation and control immune reactions. It is commonly prescribed for conditions such as asthma, arthritis, and allergic reactions. Prednisone works by acting like the body’s natural hormone cortisol to calm the immune system, and it belongs to the glucocorticoid class.

  • Methylprednisolone

    This drug is given by intravenous injection directly into a vein. It is an approved corticosteroid used for severe inflammation, allergic reactions, and certain autoimmune diseases. Like other steroids, it mimics cortisol to lower immune activity and inflammation, and it is classified as a glucocorticoid.

  • Adeno-associated viral vector serotype 2/8 containing the human ARSB gene

    This therapy is delivered as a sterile solution for intravenous infusion. It is an investigational gene‑therapy product that has orphan‑drug status and is not yet approved for general use. The treatment is designed for patients with Mucopolysaccharidosis type VI, a rare genetic disorder, and works by inserting a normal ARSB gene into liver cells so they can produce the missing enzyme that breaks down harmful substances. It is classified as a viral vector‑based gene therapy.

Investigated diseases

Mucopolysaccharidosis type VI (MPS VI) - Mucopolysaccharidosis type VI (MPS VI) is a rare inherited disorder caused by a missing enzyme that breaks down certain complex sugars. Without this enzyme, the sugars build up in cells and tissues, especially in cartilage, bone, heart, lungs, and eyes. Children with MPS VI usually develop stiff joints, short stature, and may have heart valve thickening and breathing difficulties as they grow. The accumulation of these substances continues over time, leading to gradually worsening physical function and organ involvement.
Trial detailsLast updated 29 Oct 2026
Age0-17PhasePhase ITrial ID2026-525847-34-00Protocol codeMPSVI-FT005-02Estimated enrolment6 patientsSponsorFondazione Telethon Ets

sourced from the EU Clinical Trials Register and site verification

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