July 9, 2026 —
Atsena Therapeutics announced the selection of a lead clinical candidate for ATSN-401, its investigational gene therapy program for Stargardt disease, the most common inherited macular dystrophy. The company is now advancing ATSN-401 through IND-enabling studies.
Stargardt disease is most commonly caused by mutations in the ABCA4 gene, which encodes a transporter expressed in photoreceptors. Loss of functional ABCA4 leads to accumulation of toxic bisretinoid compounds in the retinal pigment epithelium, driving progressive photoreceptor and RPE cell death. The disease typically causes bilateral central vision loss beginning in childhood or adolescence, and there are currently no approved treatments that address the underlying genetic cause.
ATSN-401 is designed to deliver full-length, functional ABCA4 to photoreceptors in the central retina. Because the ABCA4 coding sequence is too large to fit into a single AAV vector, Atsena uses a proprietary dual-vector DNA recombination platform. The approach splits the ABCA4 gene across two vectors; after co-transduction, the two halves recombine at the DNA level to produce full-length ABCA4 mRNA and protein.
The program also uses Atsena’s proprietary AAV.SPR capsid, a laterally spreading AAV capsid designed to transduce the central retina from a peripheral subretinal injection site. This approach may allow retinal surgeons to avoid detaching the dystrophic macula, a potential safety advantage in Stargardt disease where the macula is already structurally compromised.
AAV.SPR is also being used in Atsena’s ATSN-201 program for X-linked retinoschisis, which is currently in the pivotal Phase 3 portion of the LIGHTHOUSE trial. The capsid has demonstrated lateral spreading behavior in human subjects in that ongoing clinical program, supporting its broader application across inherited retinal diseases requiring central retinal delivery.
Preclinical studies of ATSN-401 in mouse and non-human primate models supported selection of the lead candidate. Atsena reported robust and properly localized ABCA4 expression, meaningful reduction of bisretinoid compounds, and a manageable safety profile at well-tolerated doses. The company said the selected candidate stood out across criteria including expression, efficacy, and safety.
Stargardt disease affects approximately 60,000 patients across the United States, Canada, and the European Union. Because disease pathology centers on the macula, conventional subretinal delivery approaches that require detachment of the central retina may pose additional surgical concerns. Atsena believes AAV.SPR’s ability to spread from peripheral injection sites could be a key differentiator for ATSN-401.
The program adds to Atsena’s expanding inherited retinal disease pipeline, which includes late-stage clinical programs in X-linked retinoschisis and LCA1, as well as earlier pipeline candidates for USH1B and Stargardt disease. If ATSN-401 advances successfully into clinical testing, it could represent a differentiated dual-vector AAV strategy for addressing one of the most common genetic causes of macular degeneration in children and young adults.
