RARE Daily

ProQR Reports Positive Results of QR-421a in Usher Syndrome

March 24, 2021

Rare Daily Staff

ProQR Therapeutics reported positive results from a planned analysis of its phase 1/2 Stellar trial of QR-421a in adults with Usher syndrome and non-syndromic retinitis pigmentosa due to USH2A exon 13 mutations.

In the trial, QR-421a demonstrated benefit on multiple measures of vision that moved in concordance, including visual acuity, visual fields, and optical coherence tomography retinal imaging, after a single dose. QR-421a was observed to be well tolerated with no serious adverse events reported.

Based on these findings, the company said it plans to advance QR-421a into two parallel pivotal phase 2/3 trials by year end 2021—one in early-moderate patients, one in advanced patients.

Usher syndrome is the leading cause of combined deafness and blindness. People with Usher syndrome type 2a are usually born with hearing loss and start to have progressive vision loss during adulthood. The vision loss can also occur without hearing loss in a related disease called non-syndromic retinitis pigmentosa. Usher syndrome type 2a and non-syndromic retinitis pigmentosa can be caused by mutations in the USH2A gene. To date, there are no pharmaceutical treatments approved or in clinical development that treat the vision loss associated with mutations in USH2A.

QR-421a is a first-in-class investigational RNA therapy designed to address the underlying cause of vision loss in Usher syndrome type 2a and non-syndromic retinitis pigmentosa due to mutations in exon 13 of the USH2A gene. QR-421a is designed to restore functional usherin protein by using an exon skipping approach with the aim to stop or reverse vision loss in patients. QR-421a is intended to be administered through intravitreal injections in the eye and has been granted orphan drug designation in the United States and the European Union and received fast track and rare pediatric disease designations from the U.S. Food and Drug Administration.

“We’re pleased to have met all the objectives we set for the Stellar trial, including determining suitable registration endpoints, the dose, dosing interval, and patient population for the phase 2/3 pivotal trials,” said Aniz Girach, chief medical officer of ProQR, “With just a single dose, QR-421a demonstrated clinical proof of concept with benefit observed in treated eyes compared to the untreated eyes in multiple concordant measures of vision.”

Girach noted that QR-421a would be the company’s second program targeting a severe inherited retinal disease that is moving into pivotal trials, further validating ProQR’s RNA therapy platform and its capabilities to take programs through clinical development.

Photo: Aniz Girach, chief medical officer of ProQR

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