Ultragenyx
29th September 2025
Dear Community Members:
We want to take a moment to update you on UX055 the gene therapy program for CDKL5 Deficiency Disorder (CDD) currently being developed by Ultragenyx.
Some of you may know the company has several late-stage programs, some of which have experienced delays. These delays have impacts on programs like UX055. With six programs in phase 3 status, there is a need for some programs to move into the commercial space to unlock earlier stage programs that are currently constrained and in need of resources.
It is important for the community to know Ultragenyx remains committed to this program. They continue to recognize the urgent need for treatments in CDD and are not ending the program. However, we also want to share honestly about some of the challenges they are facing.
We know how much hope this program represents for our community, and we remain in close communication with Ultragenyx to ensure they understand the needs of individuals and families living with CDD. They are assuring us that the program has not been stopped or abandoned. UX055 remains an important part of Ultragenyx’s work, and they continue to evaluate the best path forward.
As soon as we have any additional information to share, we will update you.
Thank you for your continued strength, advocacy, and commitment to one another. Together, we will keep pushing forward for the treatments our community so urgently needs.
With gratitude and determination,
