ProQR Announces Positive Results from Clinical Trial of QR-421a in Usher Syndrome and Plans to Start Pivotal Trials

• QR-421a demonstrated a concordant benefit in multiple measures of vision, including best corrected visual activity (BCVA), static perimetry, and retinal imaging (OCT)
• QR-421a observed to be well tolerated with no serious adverse events reported
• Two pivotal Phase 2/3 trials are expected to start by the end of 2021
• Management to host a conference call today at 8:15am EDT

LEIDEN, Netherlands & CAMBRIDGE, Mass., March 24, 2021 (GLOBE NEWSWIRE) -- ProQR Therapeutics N.V. (Nasdaq: PRQR) (the “Company”), a company dedicated to changing lives through the creation of transformative RNA therapies for inherited retinal diseases (IRDs), today announced 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 (nsRP) 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 (OCT) 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 plans to advance QR-421a to two parallel pivotal Phase 2/3 trials by year end 2021 – one in early-moderate patients, one in advanced patients.

“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, MD, 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. As expected, we saw benefits in both advanced and early-moderate patients in this slow progressing, debilitating eye disease, allowing us to advance this important investigational therapy for all patients with Usher syndrome and nsRP due to USH2A exon 13 mutations. Based on preliminary Regulatory guidance, we plan to submit protocols to advance QR-421a to pivotal testing. This is our second program targeting a severe inherited retinal disease that is moving into pivotal trials, which we believe further validates our RNA therapy platform and our capabilities to design and efficiently take these programs through clinical development.”

“The safety profile and efficacy findings for QR-421a are very encouraging,” said Robert Koenekoop, MD, MSc, PhD, FRCS(C), FARVO, a clinical-scientist from the Montreal Children’s Hospital and Professor of the McGill University Faculty of Medicine and Department of Pediatric Surgery. “Usher syndrome and non-syndromic retinitis pigmentosa due to USH2A exon 13 mutations are devastating retinal diseases representing a high unmet medical need, as there are no approved therapies to treat the severe vision loss associated with these diseases. Patients’ biggest hope for a therapy is to stop disease progression and prevent vision loss, and these findings suggest that QR-421a has the potential to stabilize vision. I look forward to this exciting program advancing into pivotal trial development.”

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