Interested in participating? Learn about future study opportunities that may be right for you.

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STUDY| Clinical Interventional

mRNA Investigational Phase 1/2


18+ years of age icon

You are 18 years of age or older

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Have been diagnosed with GSDIII

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Have a history of liver disease or low blood sugar (hypoglycemia)

Why are we doing this study?

An mRNA-based investigational medicine (called UX053) is being tested for possible use in the treatment of glycogen storage disease type III (GSDIII).

Ultragenyx is sponsoring this global study to determine if UX053 is a safe and effective treatment for adults with GSDIII.

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Additional travel support may be available

Ultragenyx recognizes that your participation in clinical research has an impact on your (and your loved ones’) time. We may provide compensation and travel support for participation in our clinical trials—the details may vary program to program. You will learn more during the consent process.

What is involved?

This study has two options.
You would only participate in one option, based on when you enroll.

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Single Infusion:
3 clinic visits over 3 months with 1 visit as an overnight stay, plus 5 home-health visits

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Up to 5 Infusions:
About 9 clinic visits over 1 year with 5-7 overnight stays and 8-9 home-health visits

What you can expect?

As a participant in either study option, you can expect the following:

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Infusion of UX053 or placebo into your arm

Lab tests

Lab tests

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Medical questionnaires

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Glucose monitoring

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Diet diary

Interested in participating or have questions? Get started
Scientist and mRNA gene therapy

mRNA is an exciting new opportunity for rare disease treatment
mRNA are medicines that instruct cells in the body to make proteins when certain proteins are missing and need to be replaced—like the one missing with GSDIII. Scientists are exploring the use of mRNA therapy to treat rare and ultra-rare diseases.

Learn about mRNA therapy and its connection to rare disease

This study is approved by the Institutional Review Board (IRB), an established organization that protects the rights and welfare of patients participating in research activities.

Get Started

To learn about current and future studies, you only need to fill out the form once.
*All fields are required.


By submitting this form, you confirm that a diagnosis of GSDIII has been made by a medical professional.

If you would like to know more about your privacy and the data you submit and data we collect while you are on this website, please see below or visit our privacy policy.

What happens after you submit your information?

Our Patient Enrollment Liaison (PEL) team will contact you by email or phone within one business day to discuss your study eligibility and answer questions.

If you choose to be contacted by email, be sure to check your spam folder for an email from [email protected], if it’s not in your regular inbox.

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Got Questions?

Email our PEL team about current and future medical research opportunities.

Glycogen Storage Disease lll (GSDIII) patient representation Glycogen Storage Disease lll (GSDIII) patient representation

Patient portrayal.

GSDIII is caused by a glycogen debranching enzyme deficiency that results in glycogen accumulation in the liver and muscles, disrupting the regulation of glucose. This can lead to extensive damage to the liver and muscles over time.

If you are thinking about joining a study, our Patient Enrollment Liaison (PEL) team is here to help. Every member of our PEL team has a robust professional background and clinical expertise and experience to help answer your questions. Your PEL team member will assist in exploring clinical and nonclinical studies and can determine if you or someone you care for may be eligible to take part. Your PEL is here to make the process as easy as possible.

To speak with a PEL about current and future medical research opportunities, please email our PEL team at [email protected].

When you voluntarily submit your personal data, Ultragenyx stores and processes this information in an electronic database consistent with our Privacy Policy. Ultragenyx will use this information to contact you to fulfill your request regarding Ultragenyx research opportunities.

Clinical and nonclinical studies provide invaluable information to treat, diagnose, or discover new breakthroughs in treating rare and ultra-rare diseases. By choosing to participate in research, you may help advance treatments, provide crucial insights, and ultimately improve the quality of life for others living with a rare or ultra-rare disease. You might also benefit from learning more about your condition, gain access to specific care, or achieve faster access to treatment. All efforts of participation, big and small, can make a difference.

Ultragenyx is leading the future of rare disease medicine. We leverage our experience, insight, and commitment to help move the rare disease community forward. Our primary goal is to provide medicines to those with limited options, and to help patients face rare disease head on with courage and confidence.

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