08:32 AM EDT, 06/27/2025 (MT Newswires) -- Ultragenyx Pharmaceutical ( RARE ) shares were over 4% higher premarket Friday after the company said the US Food and Drug Administration granted breakthrough therapy designation to GTX-102 as a treatment for Angelman syndrome.

The designation is based on results from a phase 1/2 study in 74 patients with a full maternal UBE3A gene deletion, which showed sustained improvements across multiple symptom domains when treated for up to three years, the company said.

Ultragenyx said enrollment is ongoing in its phase 3 Aspire study, which began in December and will include about 120 children aged four to 17 with Angelman syndrome.

A second study, Aurora, is expected to begin later this year and will evaluate GTX-102 in additional genotypes and age groups, Ultragenyx said.