Gene therapy vectors spread from one eye to another

The two eyes communicate not only in disease, but also in response to treatment.

David J. Calkins

A study on primates proves that viruses used in gene therapies can spread from one eye to another in three months after administration.

The investigation stems from unexpected results in human clinical trials. A few years ago, gene therapy for hereditary ocular disorder treated only one eye in patients – leaving the second eye as an untreated control. However, significant improvements were seen in both eyes. Scientists suspected viral spreading.

Three monkeys received injections of AAV2 (adeno-associated viruses serotype 2) into their right eyes. After three months, viral DNA was detected in all major parts of the eyes: the retina, the optic nerve, the anterior segment, the optic chiasm.

The transmission probably occurred via optic nerves.

The results will influence the assessment of previous clinical trials, as well as modify the design of future clinical trials. Usage of the second eye as control was more ethical, as all patients would receive a chance to preserve sight. Now, clinical trials will need control groups with patients receiving sham treatment (such as saline solution instead of gene therapy).

Source: Gensight Biologics

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