The Food and Drug Administration (FDA) has granted Fast Track designation to QR-421a (ProQR), a first-in-class RNA-based oligonucleotide being investigated for the treatment of vision loss associated with Usher syndrome type 2 and non-syndromic retinitis pigmentosa.

Usher syndrome type 2 is caused by mutations in exon 13 of the USH2A gene, which results in the loss of functional usherin protein. QR-421a works by excluding the genetic defect from the USH2A mRNA, thereby leading to the expression of a shortened but functional usherin protein, which may modify the underlying disease.

The treatment will be investigated in a Phase 1/2 safety and tolerability trial (STELLAR) where patients (N=18) will receive either a single dose administration of QR-421a via intravitreal injection or a sham procedure. The primary outcome measures include the frequency and severity of ocular and non-ocular adverse events.

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“We are very pleased with the Fast Track designation the FDA granted us for QR-421a,” said Daniel de Boer, Chief Executive Officer of ProQR. “Patients with Usher syndrome, the leading cause of combined deafness and blindness, currently have no available therapies for their vision loss and this designation emphasizes the high unmet need in this disease.”

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