QR-449

QR-449 is an experimental antisense oligonucleotide (ASO) developed by ProQR Therapeutics for the treatment of Usher syndrome type 2A (USH2A) and non-syndromic retinitis pigmentosa. It was specifically designed to target mutations in exon 13 of the *USH2A* gene, which encodes the usherin protein. The therapeutic mechanism involves exon skipping, where the ASO binds to the pre-mRNA to induce the exclusion of the mutation-bearing exon 13 during splicing. This process aims to restore the reading frame and enable the production of a truncated but functional usherin protein, potentially slowing or preventing the progressive vision loss characteristic of these conditions. While initially part of ProQR's ophthalmology pipeline, QR-449 was eventually superseded by QR-421a (ultevursen), a more advanced candidate targeting the same exon.