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• Dual vector and AAV.SPR technologies combine to drive supraphysiological levels of full-length MYO7A in non-human primate retina, reaching the macula without foveal detachment
• Six-month GLP toxicology study establishes NOAEL at the highest dose tested, with no systemic toxicity and biodistribution confined largely to the retina
• Atsena plans to submit an IND for ATSN-301 in 2027
• Data presented at the ESGCT 33^rd Annual Congress and detailed in a manuscript posted to bioRxiv

DURHAM, NC — October 30, 2026 — Atsena Therapeutics, a clinical-stage gene therapy company focused on reversing or preventing blindness from inherited retinal disease, today announced new preclinical data for ATSN-301, a gene therapy for the treatment of Usher Syndrome Type 1B (USH1B). ATSN-301 combines Atsena’s proprietary dual AAV vector (DNA recombination) technology with its laterally spreading AAV.SPR capsid to reconstitute full-length MYO7A and deliver it to the macula without the need for foveal detachment. The data demonstrated robust, full-length MYO7A expression, a favorable safety margin and no observed adverse effect level (NOAEL) at the highest dose tested in a six-month GLP toxicology study. These results are detailed in a manuscript posted to bioRxiv and in a presentation at the European Society for Gene and Cell Therapy (ESGCT) 33^rd Annual Congress, taking place October 27-30, 2026, in Hamburg, Germany.

“These preclinical data show our dual vectors doing exactly what they were engineered to do: reconstituting full-length MYO7A at supraphysiological levels and reaching the macula from an extrafoveal injection, without the surgical risk of foveal detachment. We are the first to show MYO7A expression in the nonhuman primate retina by immunohistochemistry of retinal cross sections, confirming that the protein is expressed in the right cells and layers of the retina, not just present in a tissue sample,” said Shannon E. Boye, Ph.D., Co-Founder and Chief Scientific Officer of Atsena Therapeutics. “Additionally, the six-month GLP toxicology study demonstrated a clean safety margin at the highest dose tested. These data support our plan to submit an IND in 2027.”

ATSN-301 for Usher Syndrome Type 1B

MYO7A, the gene mutated in USH1B, encodes a protein essential for hearing and vision. Patients are born profoundly deaf with vestibular dysfunction and typically develop progressive retinitis pigmentosa in the first decade of life. There are no currently approved treatments for vision loss associated with USH1B. The MYO7A coding sequence (~6.7 kb) exceeds the ~4.8 kb packaging capacity of a single AAV vector, requiring a dual vector approach to deliver the full-length gene. ATSN-301 reconstitutes full-length MYO7A by co-delivering two AAV vectors that recombine at the DNA level, an approach that avoids intentional production of multiple truncated proteins (split inteins) or transcripts (mRNA trans-splicing or RNA End Joining) that have the potential to generate truncated proteins that carry a possible toxic gain-of-function risk. In addition, ATSN-301 splits the MYO7A gene upstream of the tail domain, so the front-half vector encodes none of it. Because the tail domain binds other cellular proteins, this design avoids any potential gain-of-function effects from a truncated product. Other dual-vector approaches split further downstream, meaning their front-half vector encodes part of the tail domain.

In preclinical testing, Atsena’s optimized dual vectors, packaged in the AAV.SPR capsid, produced supraphysiological levels of full-length MYO7A in cynomolgus macaques. Following extrafoveal subretinal injection, AAV.SPR’s lateral spread delivered MYO7A to the macula and distal retina without surgical detachment of the fovea, an important consideration for USH1B patients who often retain central vision well into adulthood.

A six-month GLP toxicology study in non-human primates established a NOAEL for ATSN-301 at the highest dose evaluated. Truncated protein was minimal and had no impact on retinal safety, with no electroretinogram (ERG) changes and clean retinal histopathology. There was also no treatment-related systemic toxicity, no meaningful immunogenicity, and biodistribution was confined almost entirely to the injected retina. Atsena plans to submit an Investigational New Drug (IND) application to the U.S. Food and Drug Administration (FDA) for ATSN-301 in 2027.

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. Preclinical studies in non-human primates have demonstrated that AAV.SPR promotes transgene expression well beyond subretinal injection bleb margins, 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. AAV.SPR is the capsid platform underlying ATSN-201 (XLRS), ATSN-301 (USH1B), and ATSN-401 (Stargardt disease). For more information, visit atsenatx.com/our-approach/laterally-spreading-aav/.

About Dual Vector Technology

Some of the most prevalent inherited retinal diseases are caused by mutations in genes too large to fit inside a single adeno-associated virus (AAV) vector, placing them out of reach for conventional gene therapy approaches. The field has pursued several strategies to reconstitute a full-length protein from two AAV vectors, including DNA recombination, protein trans-splicing (split-intein), mRNA trans-splicing, and RNA end-joining, each reconstituting the gene at a different stage — DNA, protein, or RNA — and with different design trade-offs.

Atsena’s dual-vector platform is built on DNA recombination using a dual hybrid design in which two vectors co-transduce the same cell and their transgene halves are joined through the cell’s natural recombination and joining processes. Splice donor and acceptor sites then remove any intervening sequence from the transcript, yielding full-length mRNA before translation. Because this mechanism relies only on the cell’s own DNA recombination and splicing machinery, it does not require the deliberate expression of an additional protein or RNA species, which is a potential safety advantage. Atsena delivers this dual vector technology with the AAV.SPR capsid, which enables efficient transduction of foveal cones without the need for surgical detachment.

Atsena is applying this dual vector platform across its pipeline, including ATSN-301 for USH1B and ATSN-401 for Stargardt disease. For more information, visit atsenatx.com/our-approach/dual-vector-technology/.

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 Phase 3 clinical trial for X-linked retinoschisis (XLRS), a genetic condition typically diagnosed in childhood that often leads to blindness later in life. Atsena is also developing ATSN-101, an 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 and Atsena expects to initiate a global pivotal Phase 3 clinical trial evaluating ATSN-101 in the coming months. Atsena is advancing ATSN-301 toward an IND in 2027, and is also developing ATSN-401, a gene therapy for Stargardt disease. Atsena’s pipeline is powered by a proprietary adeno-associated virus (AAV) technology platform, featuring its novel laterally spreading AAV.SPR capsid and proprietary dual vector technology, designed to overcome the challenges presented by inherited retinal disease. For more information, visit atsenatx.com.

Investor and Media Contact

Argot Partners
[email protected]

Business Contact
[email protected]

ATSN-201 demonstrated structural and functional benefit in Parts A and B, including microperimetry improvements exceeding the level the FDA has defined as supportive of potential approval

Atsena also reported new data demonstrating that three patients treated at the pivotal dose have achieved driving-eligible vision (20/40 or better), and the earliest-treated patient has shown sustained benefit through three years of follow-up

Pivotal Part C cohort enrollment progressing rapidly and expected to complete Q1 2027;
topline results anticipated 1H 2028; BLA filing targeted for 2H 2028

DURHAM, NC — October 7, 2026 — Atsena Therapeutics, a clinical-stage gene therapy company focused on reversing or preventing blindness from inherited retinal disease, today announced the presentation of preliminary safety and efficacy results from Parts A and B of the Phase 1/2/3 LIGHTHOUSE Study evaluating ATSN-201 in patients with X-linked retinoschisis (XLRS) at the American Academy of Ophthalmology (AAO) 2026 Annual Meeting, taking place October 9 – 12 in New Orleans, LA.

“Data presented this week at AAO and last week at the American Academy of Optometry annual meeting show that ATSN-201 has the potential to provide clinically meaningful benefit to patients with XLRS. The majority of patients treated at the pivotal dose we are advancing in Phase 3 have achieved microperimetry improvements exceeding seven decibels across five or more loci, the level the FDA has identified as a clinical outcome supportive of approval, as well as structural and visual acuity gains that have continued to build over time,” said Kenji Fujita, M.D., Chief Medical Officer of Atsena Therapeutics. “Additionally, today we reported that three of the nine patients treated at our pivotal dose have achieved visual acuity of 20/40 or better, the threshold commonly required for driving eligibility in the United States. This would represent a meaningful improvement in independence for people living with this disease. These results give us confidence in the dose now advancing through Part C, the pivotal Phase 3 portion of the LIGHTHOUSE Study. Enrollment is progressing rapidly, a clear sign of the urgency physicians and patients share for a therapy addressing a disease with no approved treatment options.”

Preliminary safety and efficacy results for Parts A and B presented at AAO:

Thomas S. Aleman, M.D., Irene Heinz Given and John LaPorte Given endowed Professor of Ophthalmology at the Scheie Eye Institute and The Children’s Hospital of Philadelphia, Department of Ophthalmology, University of Pennsylvania, presented 12-month safety and efficacy results for 18 adult patients and six-month results for three pediatric patients enrolled in Parts A and B, the Phase 1/2 portion of the LIGHTHOUSE Study. ATSN-201 was administered via subretinal injection to one eye per patient. Part A tested three doses (low, medium, and high) of ATSN-201 in three cohorts of three adults each. Part B evaluated two dose volumes (low and high), in two cohorts of three adults each, alongside a three-adult untreated control cohort and a three-patient pediatric cohort dosed at the low volume. In total, Parts A and B enrolled 21 patients: 18 treated (15 adults, 3 pediatric) and 3 untreated adult controls.

ATSN-201 demonstrated a favorable safety profile across all subjects, with no drug-related serious adverse events, and no dose-limiting toxicities.

Efficacy measurements included structural change, measured as foveal schisis closure on optical coherence tomography (OCT), and visual function measurements, including microperimetry, best corrected visual acuity (BCVA) and low luminance visual acuity (LLVA). Microperimetry response is the primary endpoint of the pivotal Phase 3 portion of the LIGHTHOUSE Study and is defined as ≥7dB average improvement across central qualifying loci. Visual acuity response is defined as an improvement of 10 or more letters on either BCVA or LLVA.

Across the three doses tested in Part A, ATSN-201 demonstrated structural and functional benefit at every dose level. The lowest dose, 1.1E10 vg/eye (the pivotal dose), was selected to advance into Part C, the pivotal Phase 3 portion of the study, based on a consistent efficacy profile together with a more favorable tolerability profile relative to higher doses.

Pivotal dose results: Among the nine patients treated at the pivotal dose (combining the low-dose cohort from Part A, the low-volume cohort from Part B, and the pediatric cohort from Part B), seven of nine demonstrated a response on at least one of the two visual function measures (microperimetry and/or visual acuity). Five of nine were OCT responders, six of nine were microperimetry responders, and three of nine were visual acuity responders. Zero of nine untreated fellow eyes were responders by OCT, microperimetry, or visual acuity.

Full population results: Across all 18 patients treated in Parts A and B, 13 of 18 demonstrated a response on at least one of the two visual function measures (microperimetry and/or visual acuity). Twelve of 18 were OCT responders, nine of 18 were microperimetry responders, and nine of 18 were visual acuity responders. One of 18 untreated fellow eyes was a microperimetry responder, and one was a visual acuity responder; none were OCT responders. None of the three untreated control patients were OCT or microperimetry responders; one was a visual acuity responder.

Other newly reported data from the LIGHTHOUSE Study:

A recent analysis evaluated BCVA for the eight of nine patients treated at the pivotal dose who had baseline visual acuity worse than 20/40. At the most recent measurement, three of these patients had achieved visual acuity of 20/40 or better, the threshold commonly required for driving eligibility in the United States. Of the five remaining patients, three also showed improvement in visual acuity, and two were unchanged compared to baseline.

In July 2026, the earliest-treated patient in the LIGHTHOUSE study (one of the nine patients treated with the pivotal dose) reached three years of follow-up after a single administration of ATSN-201. At 36 months post-treatment, the patient’s foveal schisis remains closed, and sustained improvements in microperimetry (+12dB), BCVA (+19 letters) and LLVA (+22 letters) were observed.

Enrollment of Part C of the LIGHTHOUSE trial is progressing rapidly and expected to complete by the end of Q1 2027. Topline results are anticipated in the first half of 2028. Data from the Phase 3 cohort are expected to support a potential Biologics License Application (BLA) filing targeted for the second half of 2028.

About X-linked Retinoschisis (XLRS)

XLRS is a monogenic X-linked disease caused by mutations in the RS1 gene, which encodes retinoschisin (RS1), 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 often to blindness. XLRS primarily affects males and is typically diagnosed in early childhood. Approximately 30,000 males in North America and Europe have XLRS, for which there are currently no approved, disease-specific 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 being evaluated in the LIGHTHOUSE trial, which consists of three parts (A, B and C) across six cohorts. Parts A and B comprised the Phase 1/2 portion of the study, testing different dose concentrations and injection volumes, in both adult and pediatric patients. Part C is the pivotal Phase 3 portion of the study, a randomized, controlled trial of 76 patients ages 5 and older, with microperimetry as the primary endpoint and a 52-week primary readout. The pivotal cohort began dosing in June 2026 and is enrolling ahead of expectations at sites in the U.S. and the United Kingdom, with additional sites in Europe and Canada expected to open later this year. For more information, visit ClinicalTrials.gov (Identifier: NCT05878860).

In the completed Phase 1/2 portion of the study, ATSN-201 was the first XLRS gene therapy to demonstrate evidence of efficacy and safety, with the majority of patients showing 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, with data now extending out beyond one year in all 15 adult patients and as long as three years in the earliest treated patient. ATSN-201 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.

ATSN-201 is an investigational gene therapy. Its safety and efficacy have not been established by the U.S. Food and Drug Administration or any other regulatory authority.

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, 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 Phase 3 clinical trial for X-linked retinoschisis (XLRS), a genetic condition typically diagnosed in childhood that often leads to blindness later in life. Atsena is also developing ATSN-101, an 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 and Atsena expects to initiate a global pivotal Phase 3 clinical trial evaluating ATSN-101 in the coming months. Atsena’s pipeline of clinical and preclinical assets, including gene therapies in development for Usher syndrome type 1B and Stargardt disease, is powered by a proprietary adeno-associated virus (AAV) technology platform, featuring its novel laterally spreading AAV.SPR capsid, designed to overcome the challenges presented by inherited retinal disease. For more information, visit atsenatx.com.

Investor and Media Contact:
Argot Partners
[email protected]

Business Contact:
[email protected]