Slovenia's groundbreaking gene therapy shows promising early results

Two children who have received a pioneering gene replacement therapy for the rare neurodevelopmental disorder CTNNB1 developed in Slovenia are showing signs of progress, a promising start to clinical testing that will soon expand to more children.

After a Slovenian boy, Urban became the first patient in the world to receive the therapy in December 2025, the drug named after him was also administered to a Portuguese girl in early May, CE Report quotes The Slovenia Times.

Another child is slated to receive the therapy in September and a total of twelve from around the world will eventually receive the treatment, head of the clinical trial at the University Medical Centre in Ljubljana Damjan Osredkar told the Slovenian Press Agency (STA).

"So far, none of the children receiving treatment have experienced any serious medical complications, which means that we are currently meeting the study's primary objective of assessing the safety of the treatment," Osredkar said.

An independent commission that monitors patient safety and is informed of all developments in real time has allowed the study to continue.

The drug's effectiveness has also been confirmed by the parents of both children and by the standardized scales used to assess them, Osredkar added, as both children have shown improvement in gross and fine motor skills.

"Before treatment, he could not take a single step; four months later, he can stand on his legs independently," said Špela Miroševič, Urban's mother and a biopsychologist who spearheaded the drug's development.

His verbal skills have also improved substantially. "Before the treatmnent, he would repeat a few words - daddy, helmet, granny, grandpa - but he never initiated speech... This has changed now. The first word he said unprompted was 'television," she told public broadcaster TV Slovenija.

The children's development will be monitored for the next five years.

The CTNNB1 syndrome is a rare genetic neurodevelopmental disorder that causes varying degrees of intellectual disability, developmental delays, and problems with motor control.

It was first identified in 2012 and affects approximately 500 identified patients worldwide, though the true figure is likely to be significantly higher because the symptoms are often mistaken for cerebral palsy.

The development of the gene therapy started in 2021.

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