Retinal Schisis Closure Maintained for 18 Months: ATSN-201 Gene Therapy Shows Early Signs of Sustained Efficacy

For patients with X-linked retinoschisis, impaired vision results from abnormal separation between retinal layers, a structural problem that glasses cannot repair. On September 30, Atsena Therapeutics announced 18-month follow-up results for its investigational gene therapy ATSN-201: among nine treated adults, seven treated eyes maintained closure of foveal schisis, and some eyes also showed improvements in visual function, providing early evidence of whether efficacy can persist.

The disease primarily affects males, is typically diagnosed in childhood, and is associated with mutations in the RS1 gene, which encodes the protein retinoschisin. ATSN-201 uses an adeno-associated virus capsid called AAV.SPR. According to the company, this vector is designed to spread outward from the subretinal injection site and reach photoreceptors in the central retina, with the aim of reducing the need for surgery that directly detaches the fovea.

These data come from Part A of the LIGHTHOUSE trial, an early Phase 1/2 study, and are not Phase 3 efficacy results. Nine adults were divided into three dose groups of three participants each. Each received a subretinal injection in one eye, while the other eye remained untreated. Laura Pardon presented these data at the American Academy of Optometry's 2026 annual meeting, and the ophthalmology publication Retinal Physician also reported the same results.

At 18 months after treatment, seven of the nine treated eyes maintained closure of foveal schisis, while none of the nine untreated eyes showed this change. Functional measurements also showed differences: six treated eyes improved by at least 7 decibels on microperimetry, while no untreated eyes met that threshold; seven treated eyes gained at least 10 letters on either best-corrected visual acuity or low-luminance visual acuity testing, while one untreated eye met that threshold. Microperimetry assesses sensitivity to light at different retinal locations, providing a different type of information from identifying letters on an eye chart.

The company said these nine adults experienced no drug-related serious adverse events, dose-limiting toxicities, or treatment discontinuations. However, the absence of these events does not mean there were no side effects, and a sample of nine people is also insufficient to rule out rare risks. The publicly released information consisted primarily of a conference presentation and a company announcement, without complete individual-level data or detailed statistical analyses. Although comparison with the other eye offers useful information, it cannot replace a larger randomized controlled trial and is insufficient to establish that the therapy can prevent vision loss over the long term.

Further validation will focus on Part C of LIGHTHOUSE. This pivotal Phase 3 study, which is currently enrolling participants, uses a randomized controlled design and is expected to include 76 patients aged five years and older. Its primary assessment will be microperimetry results at 52 weeks, using the same 7-decibel response threshold applied in this early study. According to Atsena's announcement and its release carried by GlobeNewswire, the company expects to complete enrollment in the first quarter of 2027, announce primary results in the first half of 2028, and aims to submit a biologics license application in the second half of 2028. These timelines remain company estimates; the larger trial will determine whether the signal of concurrent improvements in retinal structure and function can translate into reliable treatment benefits.