About Usher syndrome type 2

What is Usher syndrome type 2?
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).
What causes Usher syndrome type 2?
USH2 is most commonly caused by mutations (or mistakes) in a gene in the DNA called the USH2A gene. This gene is responsible for the formation of the usherin protein. The mutation results in a lack of (functional) usherin protein and disrupts a process called photo transduction in the light detecting cells (rods and cones) in the retina causing RP.
Treatment
The hearing impairment that patients can experience is often manageable with hearing aids or cochlear implants. However, there are currently no available treatment options that target the underlying cause of the vision loss associated with this disease.

About QR-421a

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 12,000 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.

Beyond QR-421a, we are developing QR-411, targeting the approximately 1,000 patients that have Usher syndrome due to the c.7595-2144G>A mutation in USH2A.

Clinical trials
QR-421a is in the pre-clinical phase of testing. We are moving this program towards a first clinical trial in humans as soon as possible. Updates will be posted to this website so please check back regularly.

Information for patients

QR-421a is an experimental medicine that we are developing to treat RP in patients with Usher syndrome due to mutations in a specific part of the USH2A gene, called exon 13. We are moving this program towards a first clinical trial in patients as soon as possible. For more information about the program please visit this page since we will post regular updates here first. If you have any other questions please read the FAQ or contact us through the contact form.

Partnership with FFB

We teamed up with the Foundation Fighting Blindness (FFB) to develop QR-421a for Ushers Syndrome. In the partnership the foundation supports the trial financially and provides knowledge and knowhow on the disease, including through the learnings from the “RUSH2A” natural history study FFB is conducting. Learn more about the Foundation Fighting Blindness and read our press release.

FAQ

What is QR-421a?
QR-421a is an experimental medicine that is designed to treat RP associated with Usher syndrome type 2 caused by mutations in exon 13 of the USH2A gene. By restoring functional usherin protein expression, QR-421a aims to treat the underlying cause of RP associated with the disease. QR-421a has shown promising results in the laboratory but has not been tested in humans yet.
When and where will QR-421a be tested?
ProQR is moving this program towards first clinical trials in patients as soon as possible. Updates will be posted to this website so please check back regularly.
What are known exon 13 mutations of the USH2A gene?
Different mutations cause Usher syndrome type 2. The most common mutations in exon 13 of the USH2A gene are the c.2299delG and the c.2276G>T mutation. A list of known exon 13 mutations can be found here. We recommend that you talk to your physician if you have questions regarding genetic mutations.

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