Atsena Therapeutics Initiates Part B of Phase 1/2 Clinical Trial Evaluating Gene Therapy ATSN-201 to Treat X-linked Retinoschisis

Atsena Therapeutics announced the initiation of Part B of the LIGHTHOUSE study, a phase 1/2 clinical trial evaluating subretinal injection of ATSN-201 for the treatment of X-linked retinoschisis (XLRS). ATSN-201, a gene therapy product candidate, 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.

“We are pleased to initiate Part B of the LIGHTHOUSE study of ATSN-201 following successful enrollment and dosing of Part A. The functional and structural improvements seen in Part A validate our novel AAV.SPR spreading capsid,” Patrick Ritschel, Chief Executive Officer of Atsena Therapeutics, said in a company news release. “Importantly, Part B will enroll both adult and pediatric participants. The Rare Pediatric Disease designation granted for ATSN-201 highlights the unmet need for a treatment, and we remain focused on advancing a therapeutic option for these patients.”

Part A of the study evaluated the safety and tolerability of three different doses of ATSN-201 administered through subretinal injection. After reviewing early safety data from Part A, the Data Monitoring Committee has recommended proceeding to Part B using 1.0E11 vg/mL, a concentration that offered the optimal balance of tolerability and efficacy based on preliminary clinical results, according to Atsena. Part B is 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. Patients in the control arm will be observed off-therapy for 1 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.

“A major benefit of ATSN-201 is that it does not need to be precisely placed underneath a specific retinal region. This gives surgeons more discretion regarding bleb placement during subretinal surgery and allows for safe delivery of the healthy gene to the critical portion of the retina,” Kenji Fujita, MD, Atsena’s Chief Medical Officer, said in a company news release. “By testing different volumes in Part B, we will better understand the optimal administration of ATSN-201 to achieve the broadest effect.”

Currently, there are no approved treatments for XLRS, which is typically diagnosed in early childhood and primarily affects males. XLRS is characterized by schisis, or abnormal splitting of retinal layers, which causes impaired visual acuity that is not correctable with glasses and ultimately leads to blindness. Approximately 30,000 males in the US and EU have this inherited retinal disease.

The LIGHTHOUSE study is a phase 1/2, open-label, dose-escalation and dose-expansion clinical trial evaluating the safety and tolerability of ATSN-201 in male patients ages 6 and older with a clinical diagnosis of XLRS caused by pathogenic or likely pathogenic mutations in RS1. Enrollment for this study is ongoing. For more information, visit ClinicalTrials.gov (Identifier: NCT05878860).

ATSN-201 has received Orphan Drug and Rare Pediatric Disease designations from the FDA.