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Angelman Gene Therapy Trial Paused

A clinical trial of a gene therapy for Angelman syndrome is on hold, Spectrum reports. It adds that two participants experienced an adverse effect that affected their ability to walk.

The 20-patient clinical trial from Ultragenyx and GeneTx began last February and, according to, the small clinical trial aims to evaluate the safety and tolerability of their drug GTX-102, an antisense oligonucleotide, among patients with maternal UBE3A gene deletion to reactivate paternal UBE3A expression. 

According to Spectrum, the companies reported last month that they had enrolled five patients into their dose-escalation trial and had begun to inject the drug into the participants. However, all the participants experienced leg weakness when given high doses of the drug and two participants were unable to walk, Spectrum reports. It adds that the researchers suspect this side effect to be due to inflamed nerves near the injection site.

While the researchers tell Spectrum that the participants have recovered and that some also appear to be benefitting from the treatment, the trial remains on hold and the companies will seek a go-ahead from the US Food and Drug Administration before resuming.