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12-month results from Part A of LIGHTHOUSE Trial reinforce ATSN-201’s favorable safety profile and durable structural and functional benefits in patients with X-linked retinoschisis

Three-year data from Phase 1/2 trial confirm durable efficacy and tolerability of ATSN-101 in patients with Leber congenital amaurosis type 1

Atsena is advancing ATSN-201 and ATSN-101 into pivotal clinical trials in 2026

DURHAM, NC, May 7, 2026 – Atsena Therapeutics, a clinical-stage gene therapy company focused on using the life-changing power of genetic medicine to reverse or prevent blindness, this week presented data from three studies at the Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting in Denver, CO. The presentations included 12-month data for ATSN-201 in X-linked retinoschisis (XLRS), three-year data for ATSN-101 in Leber congenital amaurosis type 1 (LCA1), and a novel approach to measuring functional vision in inherited retinal diseases.

“Atsena is advancing two gene therapies into pivotal clinical trials — ATSN-201 for XLRS and ATSN-101 for LCA1 — making us one of a very small number of gene therapy companies with two programs in late-stage clinical development. The data we presented at ARVO 2026 reinforce our confidence in both,” said Kenji Fujita, MD, Chief Medical Officer of Atsena Therapeutics. “The 12-month Part A results for ATSN-201 demonstrate durable structural improvements and meaningful functional gains in XLRS patients, supported by a consistently favorable safety profile. The ATSN-101 data confirm durable vision improvements and sustained tolerability through at least three years post-treatment.”

ATSN-201 in X-linked Retinoschisis: 12-Month Part A Results:

Lesley Everett, MD, PhD, Assistant Professor of Ophthalmology at the Casey Eye Institute at Oregon Health & Science University, presented 12-month safety and efficacy results from Part A of the Phase 1/2/3 LIGHTHOUSE Trial. ATSN-201 continued to demonstrate a favorable safety profile across all nine adult patients, with no drug-related serious adverse events, no dose-limiting toxicities, and no patient discontinuations. Foveal schisis closure was maintained in seven of nine treated eyes at 12 months — a result not observed in untreated eyes — and statistically significant improvements in microperimetry, best-corrected visual acuity, and low-luminance visual acuity were observed in treated eyes. Patient screening is underway for Part C of the LIGHTHOUSE Trial, the study’s pivotal Phase 3 portion, with enrollment expected to complete by end of Q1 2027 and a Biologics License Application (BLA) filing targeted for 2028.

ATSN-101 in Leber Congenital Amaurosis: 36-Month Results:

Artur Cideciyan, PhD, Research Professor of Ophthalmology at the Scheie Eye Institute at the University of Pennsylvania, presented three-year safety and efficacy data from the Phase 1/2 clinical trial evaluating ATSN-101 in 15 patients with LCA1. Patients treated at the high dose continued to demonstrate clinically meaningful improvements in dark-adapted full-field stimulus testing (FST), with a mean improvement of approximately 20 decibels — a 100-fold gain in light sensitivity — that has been durable through at least three years post-treatment. ATSN-101 was well-tolerated with no drug-related serious adverse events and no patient discontinuations. Atsena expects to initiate a global pivotal Phase 3 trial for ATSN-101 in the second half of 2026.

Modified Multi-Luminance Mobility Test (modMLMT):

Alexandra Garafalo, Research Project Manager at the Scheie Eye Institute at the University of Pennsylvania, presented a poster describing a modified version of the Multi-Luminance Mobility Test (modMLMT) developed to better capture functional vision benefits in patients with retained rod function, such as those with LCA1. The modMLMT demonstrated treatment effect in more patients treated with ATSN-101 than the standard MLMT, and Atsena plans to use the modMLMT in the pivotal clinical trial evaluating ATSN-101 for LCA1.

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 ATSN-201
ATSN-201 is Atsena’s investigational gene therapy leveraging AAV.SPR, a novel, laterally spreading capsid designed to efficiently target photoreceptors in the central retina while avoiding the surgical risks of foveal detachment. It is currently being evaluated in the Phase 1/2/3 LIGHTHOUSE Trial, which consists of three parts (A, B and C) and six cohorts. The Phase 1/2 portion includes cohorts 1-3 (Part A) and cohorts 4-5 (Part B), while cohort 6 (Part C) is the pivotal Phase 3 portion of the study.

ATSN-201 is the first XLRS gene therapy to demonstrate preliminary evidence of efficacy and safety in a Phase 1/2 trial, with the majority of patients demonstrating improvements in retinal structure (foveal schisis closure) and meaningful improvements in retinal and visual function as assessed by microperimetry, best-corrected visual acuity and low-luminance visual acuity. ATSN-201 has demonstrated a favorable safety profile and has been well-tolerated for up to one year post-treatment. This 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 and Orphan Designation from the European Medicines Agency. Enrollment for this study is ongoing. For more information, visit ClinicalTrials.gov (Identifier: NCT05878860).

About GUCY2D-associated Leber congenital amaurosis (LCA1)
LCA1 is a monogenic eye disease that disrupts the function of the retina. It is caused by mutations in the GUCY2D gene and results in early and severe vision impairment or blindness. LCA1 is one of the most common forms of LCA, affecting approximately 20 percent of patients who live with this group of inherited retinal diseases. There are currently no approved treatments for LCA1.

About ATSN-101
ATSN-101 is a first-in-class, investigational, subretinal AAV5 gene therapy being developed for Leber congenital amaurosis type 1 (LCA1). ATSN-101 has completed a Phase 1/2 trial with positive results, and Atsena expects to initiate a global pivotal Phase 3 clinical trial evaluating ATSN-101 in the second half of 2026. As part of a strategic collaboration, Nippon Shinyaku Co., Ltd. has exclusive commercial rights for ATSN-101 in the U.S. and Japan, while Atsena retains commercial rights in the rest of the world.

About 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 a pivotal clinical trial for X-linked retinoschisis (XLRS), a genetic condition that is typically diagnosed in childhood and leads to blindness later in life. The company’s proprietary pipeline also includes gene therapies in development for Usher Syndrome Type 1B and for Stargardt Disease. Atsena is also developing ATSN-101, a first-in-class, investigational gene therapy for Leber congenital amaurosis type 1 (LCA1), as part of its exclusive strategic collaboration with Nippon Shinyaku Co., Ltd. ATSN-101 has completed a Phase 1/2  trial with positive results (https://doi.org/10.1016/s0140-6736(24)01447-8), and Atsena expects to initiate a global pivotal Phase 3 clinical trial evaluating ATSN-101 in the second half of 2026.

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/.

Investor and Media Contact:
Argot Partners
[email protected]

Business Contact:
[email protected]

Six-month data from adult Cohort 4 show structural and functional improvements and a favorable safety profile; early safety data from pediatric Cohort 5 are consistent with adult cohorts

Enrollment underway in pivotal Part C cohort; FDA is aligned with primary endpoint of microperimetry at 52 weeks; BLA filing is targeted for 2028

DURHAM, NC, May 4, 2026 – Atsena Therapeutics, a clinical-stage gene therapy company focused on using the life-changing power of genetic medicine to reverse or prevent blindness, presented interim six-month results from Part B of the Phase 1/2/3 LIGHTHOUSE Trial evaluating ATSN-201 in patients with X-linked retinoschisis (XLRS) at the Foundation Fighting Blindness Retinal Therapeutics Innovation Summit on May 1, 2026, in Denver, CO.

“Part B of our LIGHTHOUSE study is delivering exactly as we expected — a favorable safety profile, schisis resolution, and functional improvements at six months that closely replicate what we observed at the same time point in Part A of the study. Foveal schisis closure was observed in four of six treated adults, and there was no structural change observed in untreated control subjects or untreated contralateral eyes. The kinetics of microperimetry response across Cohort 4 mirror what we saw in Part A of the study. No serious adverse events were observed in any Part B cohort, including in our pediatric patients,” said Shannon Boye, PhD, Co-Founder and Chief Scientific Officer of Atsena.

“Enrollment in the pivotal Part C cohort is now underway, and this marks a significant milestone for patients with XLRS and for Atsena. ATSN-201 is the first gene therapy to advance to a registrational trial for XLRS, a disease with no approved treatments. We remain on track for a BLA filing in 2028,” said Kenji Fujita, MD, Chief Medical Officer of Atsena.

Part B of the study is evaluating nine adults and three pediatric patients with XLRS. The adult cohort is divided into three arms: two arms evaluating different injection volumes and an untreated control arm. Patients in the control arm will have the option to receive treatment after one year of observation. This part of the study will continue to assess safety and efficacy, including microperimetry, visual acuity, and macular structure.

Safety and efficacy highlights from the interim six-month Part B data include:

• The kinetics of structural and functional responses in Cohort 4 were consistent with those observed in Cohorts 1-3.
  • Foveal schisis closure at Month 6 was confirmed in 4 of 6 treated adults (67%) in Cohort 4. Notably, none of the three untreated control subjects and none of the six untreated contralateral eyes demonstrated foveal schisis closure.
  • Microperimetry response at Month 6 for Part B closely mirrors that observed for Part A at the same time point.
• A favorable safety profile was observed across all Part B cohorts
  • No serious adverse events (SAEs), no instances of macular hole formation or retinal detachment, and no subject discontinuations were observed.
  • Subretinal deposits observed in a subset of subjects in Cohort 4 were resolved with transient steroid treatment.
• A clean safety profile was observed in pediatric subjects (Cohort 5, ages 8–12), with no SAEs, no subretinal deposits, no macular hole formation, no retinal detachment, and no discontinuations.

Part C of the LIGHTHOUSE Trial is the Phase 3 pivotal portion of the study, enrolling a total of 76 patients with XLRS across leading clinical sites in North America and Europe. Patients are separated into two groups: treatment and control. Patients in the treatment arm will receive treatment with ATSN-201, while patients in the control arm will be observed for 12 months and then have the option to receive treatment with ATSN-201. The primary endpoint is microperimetry at 52 weeks, as aligned with the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), with visual acuity and optical coherence tomography (OCT) as key secondary endpoints. Patient screening is underway, and enrollment is expected to be completed by the end of the first quarter of 2027. Data from the Phase 3 cohort are expected to support a Biologics License Application (BLA) filing in 2028.

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 ATSN-201
ATSN-201 is Atsena’s investigational gene therapy leveraging AAV.SPR, a novel, laterally spreading capsid designed to efficiently target photoreceptors in the central retina while avoiding the surgical risks of foveal detachment. It is currently being evaluated in the Phase 1/2/3 LIGHTHOUSE Trial, which consists of three parts (A, B and C) and six cohorts. The Phase 1/2 portion includes cohorts 1-3 (Part A) and cohorts 4-5 (Part B), while cohort 6 (Part C) will serve as the Phase 3 portion of the study.

ATSN-201 is the first XLRS gene therapy to demonstrate preliminary evidence of efficacy and safety in a Phase 1/2 trial, with the majority of patients demonstrating improvements in retinal structure (foveal schisis closure) and meaningful improvements in retinal and visual function as assessed by microperimetry, best-corrected visual acuity and low-luminance visual acuity. ATSN-201 has demonstrated a favorable safety profile and has been well-tolerated for at least one year post-treatment. This 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 and Orphan Designation from the European Medicines Agency. Enrollment for this study is ongoing. For more information, visit ClinicalTrials.gov (Identifier: NCT05878860).

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 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 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 a pivotal clinical trial for X-linked retinoschisis (XLRS), a genetic condition that is typically diagnosed in childhood and leads to blindness later in life. The company’s proprietary pipeline also includes gene therapies in development for Usher Syndrome Type 1B and for Stargardt Disease. Atsena is also developing ATSN-101, a first-in-class, investigational gene therapy for Leber congenital amaurosis type 1 (LCA1), as part of its exclusive strategic collaboration with Nippon Shinyaku Co., Ltd. ATSN-101 has completed a Phase 1/2  trial with positive results (https://doi.org/10.1016/s0140-6736(24)01447-8), and Atsena expects to initiate a global pivotal Phase 3 clinical trial evaluating ATSN-101 in the second half of 2026.

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/.

Investor and Media Contact:
Argot Partners
[email protected]

Business Contact:
[email protected]