Amsterdam UMC
Responsive
Amsterdam, The Netherlands
Not yet recruitingRare disease
A Study of ATSN-201 Gene Therapy for Patients with X-linked Retinoschisis (RS1-associated) to Assess Safety and Visual Function
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What is this trial about?
A plain-language summary of the goals, design and what participants do
The study focuses on a rare inherited eye condition called RS1-associated X-linked Retinoschisis, which is caused by a problem with the RS1 gene and leads to progressive loss of vision. The investigational therapy is a gene‑delivery product named ATSN-201, which contains an adeno-associated viral vector serotype 44.9 containing the human HRS1 gene and is given as a single injection under the retina. The purpose of the study is to determine the effect of ATSN-201 on visual function.
Participants will receive the injection in one eye and will be followed for several months to assess changes in vision. Simple eye tests will be used, such as a test that measures light sensitivity across the retina (microperimetry), a scan that provides detailed pictures of retinal layers (spectral domain optical coherence tomography), and standard reading charts that evaluate sharpness of vision (best-corrected visual acuity and low luminance visual acuity measured with ETDRS charts). Additional questionnaires will ask about daily visual abilities and overall impression of change. Safety will be monitored by recording any unwanted effects.
The research process
The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.
Who can join the trial?
4 criteria
- You must be at least 6 years old.
- You must be a genetically male patient who has been given a clinical diagnosis of X‑linked retinoschisis (XLRS) caused by a disease‑causing change (called a pathogenic or likely pathogenic mutation) in the RS1 gene, or you must be a genetically female patient with the same diagnosis caused by two disease‑causing changes (one on each copy of the RS1 gene, known as biallelic mutations).
- Your best corrected visual acuity (BCVA) must be between 34 and 73 letters on the ETDRS chart, which is similar to a Snellen acuity of about 20/200 to 20/40 (a measure of how clearly you can see at a distance).
- Eye imaging with spectral‑domain optical coherence tomography (SD‑OCT) must show a split in the central retina called foveal schisis.
Who cannot join the trial?
6 criteria
- You must not have taken any carbonic anhydrase inhibitor medicine (a drug that lowers eye pressure) by mouth or as eye drops within one month before the screening visit.
- You must not have participated in a previous eye gene or cell therapy study.
- You must have a presence of macular schisis (a splitting of the central part of the retina); if this is absent, you cannot join.
- Your best corrected visual acuity (BCVA) cannot be better than 75 ETDRS letters (which is roughly the same as a Snellen acuity of 20/32, meaning you see slightly worse than normal vision).
- You cannot have existing eye problems that greatly raise the risk of vision loss from the study’s subretinal injection, such as advanced glaucoma (severe pressure damage to the optic nerve), optic neuropathy (damage to the nerve that carries visual signals), uveitis (inflammation inside the eye), or a history of corneal transplant surgery (replacement of the clear front part of the eye).
- You must not have had any intraocular surgery (eye surgery inside the eye), including laser treatment, within six months before screening, and you cannot plan to have any such surgery during the first 12 months of the study.
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Verified sites
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Azienda Ospedaliera Universitaria Universita' Degli Studi Della Campania Luigi Vanvitelli
Verified
Naples, ItalyLudwig Maximilian University Of Munich
Responsive
Munich, Germany
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Investigated drugs
ATSN-201 is a gene‑therapy medicine that is given as a tiny injection under the retina (the back part of the eye). It uses a harmless virus to carry a normal copy of the HRS1 gene into the eye’s cells. The goal is to replace the faulty gene that causes X‑linked retinoschisis, a condition where the retina splits and vision gets worse. By delivering the correct gene, the treatment hopes to improve the structure of the retina and help patients see better. This therapy is being studied in a clinical trial to see if it is safe and works well for people with this rare eye disease.
What is already known about the treatment
ATSN-201 - ATSN-201 is given as a subretinal injection of a concentrated solution containing an adeno‑associated viral vector (serotype 44.9) that carries a normal copy of the RS1 gene. It is currently an investigational gene‑therapy product being studied in early‑phase clinical trials and is not yet approved for general medical use. The treatment is designed for people with X‑linked retinoschisis, a rare inherited eye disease caused by mutations in the RS1 gene that lead to vision loss. The virus delivers the healthy RS1 gene into retinal cells, where it produces the missing protein, helping to restore normal cell connections and improve visual function; it is classified as a gene‑replacement therapy using an AAV vector.
Investigated diseases
X-linked retinoschisis - This is an inherited eye disorder caused by mutations in the RS1 gene. It usually appears in early childhood and leads to a splitting of the retinal layers, especially in the central retina. The separation disrupts normal retinal function, resulting in reduced visual acuity and difficulty seeing fine detail. Over time, the condition can cause additional changes such as peripheral retinal holes or reduced peripheral vision. The disease often progresses slowly, with gradual worsening of visual performance.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525886-38-00Protocol codeATSN-201-1Estimated enrolment76 patients
sourced from the EU Clinical Trials Register and site verification
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