By Colin Kellaher

Ultragenyx Pharmaceutical Inc. and GeneTx Biotherapeutics LLC on Monday said the U.S. Food and Drug Administration has removed the clinical hold on a study of GTX-102 for the treatment of the genetic disorder Angelman syndrome.

The companies said GeneTx may now begin dosing naive patients in a phase 1/2 open-label, multiple-dose study evaluating the safety, tolerability, and plasma and cerebrospinal fluid concentrations of GTX-102 in pediatric patients.

The FDA late last year put the study on hold after all five patients in the program developed lower extremity weakness at the highest doses.

The adverse events were assessed as mild or moderate in severity, and all fully resolved, and the companies later filed an amended dosing and administration plan with the FDA.

Ultragenyx, a Novato, Calif., biopharmaceutical company, formed a partnership with startup biotechnology company GeneTx in August 2019 to develop GTX-102, with Ultragenyx receiving an exclusive option to acquire GeneTx.

Write to Colin Kellaher at colin.kellaher@wsj.com

(END) Dow Jones Newswires

09-27-21 0908ET