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Study of Pariglasgene Brecaparvovec and Prednisolone for Adults with Glycogen Storage Disease Type Ia

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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 focused on studying a rare condition called Glycogen Storage Disease Type Ia (GSDIa). This disease affects how the body processes sugar, leading to low blood sugar levels. The study is testing a new treatment called Pariglasgene brecaparvovec, also known by its code name DTX401. This treatment involves a gene transfer method using a virus to deliver a specific gene, Glucose-6-phosphatase, to help improve sugar processing in the body. The trial aims to see if this treatment can reduce or eliminate the need for patients to rely on external sources of glucose to maintain normal blood sugar levels.

Participants in the study will receive either the new treatment or a placebo. The treatment is given as a solution through an infusion, which means it is delivered directly into the bloodstream. In addition to the main treatment, some participants will also take a medication called Prednisolone, which is a type of steroid that helps reduce inflammation. The study will compare the effects of the new treatment with those of the placebo over a period of time to determine its effectiveness and safety.

The study will last for several weeks, during which participants will be closely monitored. They will have regular check-ups and tests to track their health and how their bodies respond to the treatment. The goal is to gather information on how well the treatment works and any potential side effects. This research is important for finding new ways to help people with Glycogen Storage Disease Type Ia manage their condition more effectively.

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

    Initial assessment and randomization

    Upon joining the study, an initial assessment is conducted to confirm eligibility. This includes verifying the diagnosis of Glycogen Storage Disease Type Ia (GSDIa) through enzymatic activity tests or genetic testing.

    Participants are then randomly assigned to receive either the gene therapy treatment or a placebo.

  2. Step 2

    Gene therapy administration

    Participants receiving the gene therapy will be administered pariglasgene brecaparvovec via an intravenous infusion. This is a one-time procedure.

  3. Step 3

    Prednisolone treatment

    Following the infusion, participants will begin a course of prednisolone tablets. The dosage starts at 10 mg and is taken orally. The treatment is adjusted as needed throughout the study.

  4. Step 4

    Monitoring and follow-up

    Participants will be monitored regularly to assess their health and response to the treatment. This includes frequent blood tests and glucose monitoring using a continuous glucose monitoring (CGM) device.

    Participants are required to maintain a stable diet and record their daily intake of cornstarch and other carbohydrates in an electronic diary.

  5. Step 5

    Evaluation of outcomes

    The primary outcome is the change in daily cornstarch intake from the start of the study to week 48. Secondary outcomes include changes in glucose levels and the incidence of hypoglycemic events.

    Participants' progress and any side effects are documented throughout the study period.

  6. Step 6

    Completion of study

    The study concludes after 48 weeks. Participants undergo a final assessment to evaluate the overall impact of the treatment on their condition.

Who can join the trial?

11 criteria

  • Patients must be **8 years or older**.
  • Must have a confirmed diagnosis of **Glycogen Storage Disease Type Ia (GSDIa)**. This can be confirmed by a liver test showing low enzyme activity or a genetic test showing two problem-causing changes in the **G6PC gene**. If only one change is found, the diagnosis should match GSDIa and not show signs of GSDIb, like ongoing low white blood cells or bowel disease.
  • Currently following a treatment plan with **cornstarch** or similar, with stable health and nutrition. This means:
  • No more than a 10% change in daily cornstarch intake over the last 4 weeks.
  • No more than a 25% change in daily intake of other carbohydrates over the last 4 weeks.
  • No more than a 15% change in blood sugar levels within the target range (60-120 mg/dL) over the last 4 weeks, checked by a **Continuous Glucose Monitor (CGM)** or **Self-Monitoring of Blood Glucose (SMBG)**.
  • No hospital visits for low blood sugar or severe low blood sugar events in the 4 weeks before starting the study, unless caused by unavoidable events like infection or injury.
  • Willing and able to follow study rules, including hospital stays, blood tests, wearing a CGM, using a specific glucometer, keeping a diary of cornstarch and diet intake, and completing questionnaires. Must follow any changes in medication as directed by the study doctor.
  • If under 18, must have a parent or guardian willing to help with study requirements.
  • Women who can have children and men who are fertile must agree to use effective birth control during the study and for 48 weeks after the last dose if they leave the study early. Women must agree not to become pregnant, and men must agree not to father a child or donate sperm during this time.
  • Must be willing and able to sign a consent form after the study is explained. If under 18, must provide written agreement and have a parent or guardian sign the consent form.
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Investigated drugs

DTX401 is a gene therapy being studied for its potential to help patients with Glycogen Storage Disease Type Ia. This therapy uses a virus called Adenoassociated Virus Serotype 8 to deliver a specific gene into the patient's body. The goal of this treatment is to help the body produce an enzyme called glucose-6-phosphatase, which is important for maintaining normal blood sugar levels. By doing this, DTX401 aims to reduce or eliminate the need for patients to rely on external glucose sources to keep their blood sugar under control.

What is already known about the treatment

DTX401 – This medication is administered through an intravenous infusion, delivering a gene therapy treatment directly into the bloodstream. It is currently in the clinical trial phase, specifically a Phase 3 study, and is being investigated for its potential to treat Glycogen Storage Disease Type Ia (GSDIa). The main therapeutic goal is to reduce or eliminate the need for external glucose replacement therapy in patients. DTX401 works by using an adeno-associated virus serotype 8 vector to deliver a functional copy of the glucose-6-phosphatase gene, which is deficient in individuals with GSDIa, thereby restoring normal glucose metabolism. It is classified under gene therapy medications.

Investigated diseases

Glycogen Storage Disease Type Ia (GSDIa) – This is a rare genetic disorder that affects the body's ability to break down glycogen into glucose, which is necessary for energy. It is caused by a deficiency of the enzyme glucose-6-phosphatase, leading to the accumulation of glycogen in the liver and kidneys. Individuals with GSDIa often experience low blood sugar levels, especially between meals or during fasting. Symptoms may include an enlarged liver, growth delays, and increased levels of lactic acid in the blood. Over time, the condition can lead to complications such as kidney problems and liver adenomas. Management typically involves maintaining normal blood sugar levels through dietary modifications.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-508750-25-00Protocol codeDTX401-CL301Estimated enrolment57 patientsSponsorUltragenyx Pharmaceutical Inc.

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