Daniel de Boer, Founder and CEO of ProQR, discusses his company’s clinical program focusing on Usher syndrome is a rare genetic disease that is the leading cause of combined deafness and blindness. Patients with Usher syndrome type 2 (USH2), the most common type of Usher Syndrome, have a moderate to severe hearing impairment from birth and commonly experience the first symptoms of night blindness in their second decade of life, which progresses to complete blindness by the third or fourth decade of life. The progressive vision loss in these patients is known as retinitis pigmentosa (RP).
ProQR is developing a novel investigational drug called QR-421a to treat RP in patients that have USH2 due to a mutation in a specific part of the USH2A gene, called exon 13. In the Western world there are approximately 16,000 patients that experience vision loss due to a mutation in exon 13 of the USH2A gene. QR-421a is designed to exclude exon 13 from the USH2A mRNA, thereby removing the mutation in exon 13. This approach is also known as exon skipping.
RNA is the “blueprint” for protein synthesis. Skipping of exon 13 in the “blueprint” is expected to lead to a shortened but functional usherin protein. By restoring functional usherin protein expression, QR-421a aims to treat the underlying cause of RP associated with USH2. QR-421a is intended to be administered via intravitreal (into the eye) injections.