FDA Awards Fast Track Designation to ATSN-201 Gene Therapy for XLRS

The US Food and Drug Administration (FDA) has granted Fast Track designation to ATSN–201 for the treatment of X-linked retinoschisis (XLRS), marking the third FDA designation for the novel gene therapy.1

Announced by Atsena Therapeutics, on March 12, 2025, ATSN-201 was previously granted Orphan Drug and Rare Pediatric Disease designations from the regulatory agency, with the new designation allowing for Priority Review if relevant criteria are met.

“We are pleased that the FDA has granted Fast Track designation to ATSN-201, reinforcing its potential to address the significant unmet need in XLRS, a rare inherited retinal disease with no approved treatments,” said Patrick Ritschel, chief executive officer of Atsena Therapeutics.1

Fast Track designation is awarded to therapies that address serious or life-threatening diseases and demonstrate the potential to tackle these unmet medical needs. With this indication, companies may interact more frequently with regulators during the drug development process.2

XLRS is a genetic disorder primarily affecting males, caused by mutations in the RS1 gene which leads to abnormal retinal layer separation and visual impairment that is not correctable with glasses. Approximately 30,000 male patients in the US and the European Union are affected by XLRS. It is typically diagnosed in early childhood and there are no approved treatments.3

ATSN-201 utilizes Atsena Therapeutics’ novel spreading capsid to reach therapeutic gene expression in photoreceptors in the central retina and avoid the risks of foveal detachment linked to surgery. The company’s AAV.SPR capsid spreads laterally beyond the subretinal injection site to allow for safe and efficient transduction of the central retina after injection in areas outside the macula.1

Safety and tolerability of subretinal ATSN-201 is under investigation in the Phase 1/2 LIGHTHOUSE dose-escalation and dose-expansion clinical trial. LIGHTHOUSE is actively enrolling male patients aged ≥6 years with a diagnosis of XLRS based on mutations in the RS1 gene.

Atensa completed Part A of the LIGHTHOUSE study in December 2024, which evaluated the safety and efficacy of 3 dose levels of ATSN-201 in 9 adults with XLRS. Results from the initial part of the trial demonstrated structural and functional benefits at all dose levels, with no reports of serious adverse events linked to treatment.4

In January 2025, the company announced the initiation of Part B of LIGHTHOUSE, which plans to enroll adult and pediatric participants. After a review of early safety data, the Data Monitoring Committee recommended Part B use ATSN-2011.0E11 vg/mL for an optimal balance of tolerability and efficacy based on preliminary results.5

Part B of the trial will assess 9 additional adults and 3 pediatric patients with XLRS, with the population broken down into low-volume, high-volume, and control cohorts. The control cohort will be observed off-therapy for one year and then be offered ATSN-201 treatment. Pediatric patients will be dosed after evaluating preliminary data from the adult cohort.

“This designation, along with the previously granted Orphan Drug and Rare Pediatric Disease designations, marks an important milestone in advancing the development of ATSN-201," Ritschel added.1 "The Atsena team remains dedicated to developing transformative gene therapies and improving the quality of life of individuals suffering from XLRS and other inherited retinal diseases.”

References

1. Haserick B. Atsena Therapeutics granted U.S. FDA Fast Track designation for ATSN-201 gene therapy to treat X-linked retinoschisis. Atsena Therapeutics. March 12, 2025. Accessed March 12, 2025. https://atsenatx.com/press-release/atsena-therapeutics-granted-us-fda-fast-track-designation-for-atsn-201-gene-therapy-to-treat-x-linked-retinoschisis/.

2. Commissioner O of the. Fast track. U.S. Food and Drug Administration. Accessed March 12, 2025. https://www.fda.gov/patients/fast-track-breakthrough-therapy-accelerated-approval-priority-review/fast-track.

3. Sieving PA, MacDonald IM, Hoang S. X-Linked Congenital Retinoschisis. 2003 Oct 24 [Updated 2020 Nov 5]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1222/

4. Haserick B. Atsena Therapeutics announces dosing completed in part A of phase I/II clinical trial evaluating Gene Therapy ATSN-201 to treat X-linked retinoschisis. Atsena Therapeutics. December 16, 2024. Accessed March 12, 2025. https://atsenatx.com/press-release/atsena-therapeutics-announces-dosing-completed-in-part-a-of-phase-i-ii-clinical-trial-evaluating-gene-therapy-atsn-201-to-treat-x-linked-retinoschisis/.

5. Haserick B. Atsena Therapeutics initiates part B of phase I/II clinical trial evaluating Gene Therapy ATSN-201 to treat X-linked retinoschisis. Atsena Therapeutics. January 8, 2025. Accessed March 12, 2025. https://atsenatx.com/press-release/atsena-therapeutics-initiates-part-b-of-phase-i-ii-clinical-trial-evaluating-gene-therapy-atsn-201-to-treat-x-linked-retinoschisis/.