Errors in a particular section (exon 13) of the USH2A gene are thought to be associated with more than 16,000 cases of inherited sight loss, and there is currently no treatment available. ProQR has developed a special molecular “patch” that covers up the faulty section of genetic code, enabling retinal cells to use the rest of the USH2A genetic information to produce functional USH2A protein.
The treatment, currently known as QR421a, is administered via injection into the eye and has now been tested in a clinical trial involving twenty people with varying degrees of vision loss. With only one injection of QR-421a, the study showed benefits in the treated eye in comparison to the untreated eye in all participants across multiple eye tests. This included stabilization of central vision loss, as measured with an eye chart, in participants with more advanced visual impairment, and improvements in measures of retinal sensitivity in those at earlier stages of sight loss.
Importantly, the trial also demonstrated that QR421a is safe and well tolerated at various doses, with no serious side effects.
ProQR has agreed with medical regulators to advance QR-421a into final stage clinical testing in people with USH2A-associated sight loss. This will involve two phase 2/3 clinical trials, one for participants with more advanced sight loss (BCVA equal to or worse than 20/40) and the other for participants at an earlier stage of sight loss (BCVA better than 20/40). Both trials will run over two years at various centres in Europe and the USA (exact locations tbc).
All participants in these trials will need to have a genetic test result showing that their sight loss is caused by mutations in exon 13 of the USH2A gene. More information about genetic testing is available on our website and from our Helpline: 0300 111 4000; Helpline@RetinaUK.org.uk.