March 26 webinar about Sanfilippo type A gene therapy program (UX111)

February 19, 2024

Ultragenyx is conducting a gene therapy clinical trial for Sanfilippo syndrome type A. This trial has been going on for many years and, as a community, we have been anticipating updates on the interim outcomes of this trial.

Ultragenyx has provided a letter to the community regarding the UX111 program for Sanfilippo syndrome Type A (MPS IIIA), also shared below.

Cure Sanfilippo Foundation hosted a town hall webinar on March 26, 2024, in collaboration with the National MPS Society and Ultragenyx. The event was moderated by the organizations’ scientific officers Cara O’Neill, MD, of Cure Sanfilippo Foundation and Matthew Ellinwood, DVM, PhD, of the National MPS Society in conjunction with leaders from Ultragenyx.

During this webinar, you hear directly from Ultragenyx leaders regarding the scientific learnings to date and future plans for the program.

Background information on this and other trials can be found here for your reference.

Letter From Ultragenyx

February 6, 2024

Dear Members of the MPS III Community,

We hope that this letter finds you and your families well.

Ultragenyx has received questions from the community regarding our ongoing research, and we want to ensure that you have access to timely and accurate information that responds to those questions. We are writing today regarding the status of the UX111 (formerly ABO-102) gene therapy program for Sanfilippo syndrome type A (MPS IIIA).

Program Announcement
Today Ultragenyx announced that we will present the latest data on the effects of UX111, an investigational gene therapy, on toxic heparan sulfate (HS) exposure in cerebral spinal fluid (CSF) fluid in patients living with MPS IIIA at the WORLDSymposium 2024 in San Diego, California taking place February 4-9, 2024.

These data are from the ongoing pivotal Transpher A study and its associated long-term follow-up study. As an important reminder, UX111 continues to be studied in clinical trials as a potential treatment for MPS IIIA, and its safety and efficacy have not yet been established and it has not been approved by any regulatory agency.

Next Steps
We are looking forward to hosting a webinar with the patient advocacy organizations who represent the MPS III community to expand upon this news and answer the community’s questions as part of our commitment to providing families with timely information. We are working with the Cure Sanfilippo Foundation to host a webinar and will partner with them and other patient advocacy organizations to ensure families have an equal opportunity to participate. We will be in touch with the community with more information as the webinar planning advances.

Thank You!
Ultragenyx, study site physicians, and study teams are working closely together to support all patients and their families in their ongoing participation to collect safety and efficacy data in the Transpher A and long-term follow-up studies. We are grateful for the participation of all patients and families who are contributing to this program and appreciate their commitment in completing this research. The totality of data collected over the entire duration of the studies and from each study participant plays a critical role in understanding the potential benefits and risks of UX111 and in planned data submissions to regulatory agencies like the US Food and Drug Administration (FDA) and European Medicines Agency (EMA).

The Ultragenyx team would also like to express our sincere appreciation to the organizations representing the MPS III community and the families affected by MPS IIIA who have been a fierce ally throughout the development of this gene therapy program. This research would not be possible without you. We will continue to share timely information with the scientific and family communities as the ongoing research progresses. In the meantime, please visit our Patient Advocacy website at to access rare disease education and tools.

On Behalf of the UX111 Team,
Kristin Voorhees, MA
Director of Patient Advocacy

Read the print-version of the letter from Ultragenyx.

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