Researchers at Columbia University have found a way to apply CRISPR, a tool used in gene therapies, to new types of disease, reports News Medical. The study was carried out on mice with a retinal disease called retinitis pigmentosa, but the findings are hoped to be applicable to many other diseases, including Huntington’s disease, corneal dystrophies, and Marfan syndrome.

Retinitis pigmentosa is a degenerative retinal disease that affects vision. It is thought to occur in approximately one in every 4,000 people, and can lead to problems with seeing things at night and outside the center of the field of vision.

Retinitis pigmentosa is a genetic disease that can come in two forms: autosomal dominant and autosomal recessive. In the autosomal recessive form, affected people have two copies of the genetic variant that causes the disease. This makes it more straightforward to treat through gene therapies because the process should target both copies of the same gene. There are currently six companies developing gene therapies to treat the recessive form of retinitis pigmentosa. However, those with the autosomal dominant form of the condition have only got one disease-causing gene variant, and the matching gene from the other parent is healthy. This means that the gene therapy process is more complex because only one of the two genes should be changed.

The new technique, developed by Dr. Tsang and his team, modifies CRISPR to do this. The standard technique uses one guide RNA to find and replace the genetic variant with a healthy gene, while the new method uses two guide RNAs to do this. This increases the probability of affecting the unwanted gene variant by 60%, from 30% to 90%. In addition, the new method is thought to also be useful for treating cells that are non-dividing, such as those in the eyes, heart, and brain, whereas the standard form of CRISPR is known to work less well for these cell types.

The development of the gene therapy technique CRISPR is hoped to enable the treatment of many other diseases, in addition to retinitis pigmentosa. It is anticipated to be particularly useful for autosomal dominant genetic conditions, and those that affect non-dividing cells. Human trials are expected to begin in around three years, dependent on further successful research.

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