Atsena Therapeutics Announces Positive Clinical Data from Part A of Phase I/II Trial Evaluating ATSN-201 Gene Therapy to Treat X-linked Retinoschisis (XLRS)

First XLRS study to demonstrate efficacy and positive safety data in a Phase I/II trial

Majority of patients demonstrated successful efficacy readouts across structural measurements (foveal schisis closure) and had meaningful improvement on visual function measurements including MP, BCVA, and LLVA

Safe and well-tolerated up to one year post-treatment

/EIN News/ -- DURHAM, N.C., May 19, 2025 (GLOBE NEWSWIRE) -- Atsena Therapeutics, a clinical-stage gene therapy company focused on using the life-changing power of genetic medicine to reverse or prevent blindness, today announced positive clinical data results from Part A of the LIGHTHOUSE study, a Phase I/II clinical trial evaluating subretinal injection of ATSN-201 for the treatment of X-linked retinoschisis (XLRS). ATSN-201 leverages AAV.SPR, the company’s novel spreading capsid, to achieve therapeutic levels of gene expression in photoreceptors of the central retina while avoiding the surgical risks of foveal detachment. The best-in-class gene therapy product candidate has received Regenerative Medicine Advanced Therapy, Fast Track, Rare Pediatric Disease, and Orphan Drug Designations from the U.S. Food and Drug Administration.

“The full Part A data from the LIGHTHOUSE study reinforce the favorable safety profile and demonstrate encouraging structural and functional benefits across all three dose levels of ATSN-201,” said Kenji Fujita, MD, Chief Medical Officer of Atsena Therapeutics. “Interim data is available for nine adults who have been treated, and no serious adverse events related to treatment have been reported. We’re particularly pleased that the foveal schisis closure seen in 7 of 9 patients validates AAV.SPR’s ability to spread laterally beyond the subretinal injection blebs and enable safe gene delivery to the central retina. These findings represent a significant breakthrough, validating the use of our novel capsid to effectively treat inherited retinal disease and informing the safest and most effective path forward for Part B of the study, which is already underway. We look forward to advancing ATSN-201, which is on track to be the first gene therapy approved for XLRS.”

Part A of the study evaluated the tolerability and safety of three different doses of ATSN-201 administered through subretinal injection in three patients per cohort, for a total of nine adult patients. ATSN-201 was well tolerated in all nine patients with XLRS in Part A, and no serious adverse events related to treatment were reported. The majority of adverse events were related to the surgical procedure and were Grade 1-2 in severity. One serious adverse event, a fever of unknown origin with negative workup, occurred, which was unrelated to ATSN-201 or the surgical procedure. There were no dose-limiting toxicities, and no subjects discontinued from the study.

Efficacy highlights from the data include:

• Preliminary evidence of efficacy demonstrated at all dose levels
• 7 of 9 treated eyes had closure of foveal schisis, which was not demonstrated in untreated eyes
• On Microperimetry (MP), 67% of treated eyes (6/9) had an improvement of ≥ 7 dB in the 5 or more loci with the lowest sensitivity at baseline
• Statistically significant improvements were seen in Best Corrected Visual Acuity (BCVA) and Low Luminance Visual Acuity (LLVA)
• Structural improvements correlated with improvements in function
  

Enrollment is underway in Part B, a multicenter clinical trial that will evaluate nine additional adults and three pediatric patients with XLRS. The adult cohort will be broken down into three arms: low volume, high volume, and control (deferred treatment). Patients in the control arm will be observed for one year and then have the option to receive treatment. The pediatric cohort will be dosed after evaluating preliminary data from the adult cohort in Part B. This part of the study will continue to assess safety and efficacy, including microperimetry, visual acuity, and macular structure.

“We’re proud to share these clinical data that demonstrate ATSN-201 can be safely delivered subretinally in patients with extensive retinal schisis—a pivotal milestone for our XLRS program,” said Patrick Ritschel, Chief Executive Officer of Atsena Therapeutics. “These data underscore the promise of our novel spreading capsid and the urgency of addressing a devastating disease with no approved therapeutic solutions. We remain deeply committed to advancing gene therapies that can transform the lives of individuals living with XLRS and other inherited retinal diseases.”

Currently, there are no approved treatments for XLRS, which is typically diagnosed in early childhood and affects approximately 30,000 males in the U.S. and the EU combined. The LIGHTHOUSE study is a dose-escalation and dose-expansion clinical trial in male patients ages six and older with a clinical diagnosis of XLRS caused by mutations in the RS1 gene. Enrollment for this study is ongoing. For more information, visit ClinicalTrials.gov (Identifier: NCT05878860).

Interim results from Part A of the study were presented at the 2025 Association for Research in Vision and Ophthalmology and 2025 American Society for Gene and Cell Therapy annual meetings. Presentations can be found on the Presentations and Publications page of the Atsena website at www.atsenatx.com/news/presentations-and-publications.

About X-linked Retinoschisis (XLRS)
XLRS is a monogenic X-linked disease caused by mutations in the RS1 gene which encodes retinoschisin, a protein secreted primarily by photoreceptors. RS1 is localized to the extracellular surface of rods, cones, and bipolar cells. XLRS is characterized by schisis, or abnormal splitting of retinal layers, which causes impaired visual acuity that is not correctable with glasses and leads to progressive vision loss and ultimately blindness. XLRS primarily affects males and is typically diagnosed in early childhood. Approximately 30,000 males in the U.S. and EU have XLRS, for which there are currently no approved treatments.

About AAV.SPR
AAV.SPR, one of Atsena’s novel capsids, spreads laterally beyond the subretinal injection site to enable safe and efficient transduction of the central retina (where schisis cavities predominate in XLRS patient retinas) when injected into areas outside the macula. A preclinical study in non-human primates demonstrated that AAV.SPR promotes transgene expression well beyond subretinal injection bleb margins. This is in contrast to benchmark AAV vectors, which remain confined to the original bleb margins. At clinically relevant doses, AAV.SPR efficiently transduces foveal cones without the need for surgical detachment and has a favorable safety profile relative to benchmark capsids. For more information about the preclinical study and how AAV.SPR works, visit https://atsenatx.com/our-approach/laterally-spreading-aav/.

About Atsena Therapeutics
Atsena Therapeutics (“Atsena”) is a clinical-stage gene therapy company developing best-in-class treatments for the reversal or prevention of blindness from inherited retinal diseases. The company’s lead program is evaluating ATSN-201 in an ongoing Phase I/II clinical trial for X-linked retinoschisis (XLRS), a genetic condition that is typically diagnosed in childhood and leads to blindness later in life. ATSN-101, Atsena’s first-in-class, investigational gene therapy for Leber congenital amaurosis type 1 (LCA1) has completed a Phase I/II trial with positive results (https://doi.org/10.1016/s0140-6736(24)01447-8). Atsena is advancing ATSN-101 toward the initiation of a global pivotal trial as part of its exclusive strategic collaboration with Nippon Shinyaku Co., Ltd. Atsena’s pipeline is powered by novel adeno-associated virus (AAV) technology tailored to overcome the hurdles presented by inherited retinal diseases. Founded by pioneers in ocular gene therapy, Atsena is led by an experienced team dedicated to addressing the needs of patients with vision loss. For more information, please visit https://atsenatx.com/.

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