New York, April 6
Delivering drug to the foetus as it develops in the womb may one day treat Usher syndrome, a genetic disorder characterised by deafness and progressive vision loss affecting an estimated 4 to 17 of every 100,000 people, suggests new research.

The findings, published in the journal Nucleic Acid Research, suggest an avenue to treat and prevent intractable genetic disorders before birth.

The researchers from Oregon Health & Science University (OHSU) in the US injected a specially designed synthetic molecule into the developing inner ear of foetal mice 12 days after fertilisation.

The study found that the technique corrected the expression of a mutated gene that causes Usher syndrome.

The technique does not directly translate to clinical applications in people.

However, the new research combined with previous findings suggests it may be possible to deliver the drug therapy through amniotic fluid in the womb to the foetus.

The scientists designed a synthetic antisense oligonucleotide, or ASO, which targets and then attaches to precise nucleic acid sequences.

In this case, the molecule was designed to target pre-messenger RNA, a class of molecules that influences when, where, and how strongly genes are expressed in a cell.

When scientists injected the ASO into the developing inner ear of foetal mice carrying the gene mutation, the mice developed with no symptoms of Usher syndrome.

"This shows that direct administration of the ASO to the inner ear restored hearing and balance," said senior author John Brigande, principal investigator for the Oregon Hearing Research Center at OHSU.

Researchers expect to move from a mouse model to nonhuman primates, which more closely model human hearing loss, before the technique would be ready for human clinical trials.

Brigande said he expects it will be useful in potentially treating and preventing several types of congenital forms of hearing and balance disorders.

Foetal drug therapy for deafness shows promise