Benzinga | Oct 26, 2020 04:04PM EDT

UPDATE: GeneTx And Ultragenyx Announce Highest Doses Associated With A Significant But Reversible Safety Issue

Efficacy in multiple functional measures observed in all five patients treated

Highest doses associated with a significant but reversible safety issue

Study amendment planned to focus on lower end of dose range

Conference call to discuss results planned for 5pm Eastern Time

SARASOTA, Fla. and NOVATO, Calif., Oct. 26, 2020 (GLOBE NEWSWIRE) -- GeneTx Biotherapeutics LLC and Ultragenyx Pharmaceutical Inc. (NASDAQ:RARE), companies partnered in the development of intrathecally administered GTX-102, an investigational treatment for Angelman syndrome, today announced positive interim data from the Phase 1/2 study of GTX-102. Preliminary results from the first five patients treated indicate substantial improvements in all patients in at least two disease domains including communication, behavior, sleep, gross motor function, and fine motor function as measured by the Clinical Global Impression of Improvement Scale for Angelman Syndrome (CGI-I-AS) at day 128. At the highest doses, all five patients experienced a serious adverse event (SAE) of lower extremity weakness believed to be related to local inflammation due to GTX-102. Following these events, the companies paused enrollment and dosing. These SAEs were assessed as mild or moderate in severity and have generally improved over a period of a few weeks while disease domain improvements have been sustained for three months. The study protocol will be amended to reduce the dose-level range and modify the administration process, which is expected to reduce further drug-related SAEs.

"The work that the GeneTx team and Dr. Scott Dindot and his lab have conducted over these last years provided the opportunity to impact Angelman syndrome in a fundamental manner with a potent antisense oligonucleotide," noted Emil D. Kakkis, M.D., Ph.D., CEO and President of Ultragenyx. "These initial GTX-102 findings raise the possibility of improving some of the significant symptoms of Angelman syndrome."

"The UBE3A antisense transcript targeted by GTX-102 is a viable target for treatment," stated Scott Stromatt, M.D., Chief Medical Officer of GeneTx. "The results observed to date are encouraging and we look forward to resuming dosing at lower doses to help avoid side effects."

"So far we are seeing rapid improvements in multiple areas, including some kids doing things they've never done before, and I don't believe this rate of progress in development skills has been seen before in Angelman syndrome," commented Elizabeth M. Berry-Kravis, M.D., Ph.D., Professor of Pediatrics, Neurological Sciences and Biochemistry, Rush University Medical Center, and investigator in the GTX-102 clinical study. "It is especially amazing that families are asking me repeatedly when they can start treatment again despite the side effects that their child experienced. That speaks to the value of what they were seeing in their child."