MavriX Bio’s Angelman Syndrome Gene Therapy MVX-220 Garners FDA Fast Track Designation

MavriX Bio’s MVX-220, an investigational adeno-associated virus (AAV) vector-based gene therapy, has received fast track designation from the FDA for the treatment of Angelman syndrome (AS).¹

The therapy’s initial development was financially supported by the Foundation for Angelman Syndrome Therapeutics (FAST) and took place at the University of Pennsylvania. MavriX Bio later licensed the product and is carrying out clinical development in conjunction with partner GEMMA Biotherapeutics (GEMMABio). MavriX is a portfolio company of AS2Bio, a FAST drug development accelerator.

"GEMMABio has been deeply honored to support MavriX Bio on the MVX-220 development program,” James M. Wilson, MD, PhD, thechief executive officer at GEMMABio, said in a statement.¹ “With fast track status, this program gains crucial momentum—it means the team can engage more closely with regulators and accelerate development milestones. For the AS community, fast track designation opens up a path toward bringing gene-targeted therapies to patients sooner.”

MVX-220 is intended to provide a functional copy of UBE3A, the disease-targeted gene, to the neurons. The FDA cleared MavriX’s investigational new drug application for MVX-220 in May of this year, thus paving the way for a planned phase 1/2 clinical trial (ASCEND-AS; NCT07181837). The first-in-human ASCEND-AS study, which is expected to launch in October 2025, will include approximately 12 patients with AS aged 4 to 50 years. The trial will be open to patients with AS with various genetic causes, including deletion, uniparental disomy, and imprinting center defects.

"The FDA's decision to grant fast track designation for MVX-220 reflects the urgent need for therapies for individuals living with AS," Allyson Berent, DVM, DACVIM, the chief development officer of MavriX Bio, added to the statement.¹ "This designation highlights the promise MVX-220 holds as a potential treatment for AS, and importantly, enables closer collaboration with the FDA and an accelerated path forward."

MVX-220 is not the only advanced therapeutic currently in development for AS.2 Ultragenyx is currently developing GTX-102 (also known as apazunersen), an antisense oligonucleotide product intended to treat AS. GTX-102 is currently being evaluated in a phase 3 clinical trial (NCT06415344).

GTX-102 was previously assessed in a phase 1/2 trial (NCT04259281) for AS.³ Interim data from that study were reported by the company in 2022.

"I am convinced we are seeing evidence of a therapeutic effect with GTX-102 though it's still early in the study,” primary investigator Erick Sell, MD, associate professor of neurology and director, Angelman clinic, Children's Hospital of Eastern Ontario, said in a July 2022 press release.³ “I am also encouraged by the improvements in quality of life that most of the families at my center are consistently reporting and believe that this could be a promising treatment for patients with AS."

REFERENCES
1. MavriX Bio receives FDA fast track designation for MVX-220 for treatment of Angelman syndrome. News release. MavriX Bio. September 22, 2025. Accessed September 29, 2025. https://firstwordpharma.com/story/6094777
2. GTX-102 (apazunersen): Antisense oligonucleotide for the potential treatment of Angelman syndrome (AS). Ultragenyx. Website. Accessed September 29, 2025. https://www.ultragenyx.com/our-research/pipeline/gtx-102-for-angelman-syndrome/
3. Ultragenyx and GeneTxprovide program update on GTX-102 for Angelman Syndrome including promising interim data from phase 1/2 study. News release. Ultragenyx. July 18, 2022. Accessed September 29, 2025. https://ir.ultragenyx.com/news-releases/news-release-details/ultragenyx-and-genetx-provide-program-update-gtx-102-angelman