Atsena Therapeutics presented interim 6-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.

Part B of the study is evaluating 9 adults and 3 pediatric patients with XLRS. The adult cohort is divided into 3 arms—2 arms evaluating different injection volumes and an untreated control arm. Patients in the control arm will have the option to receive treatment after 1 year of observation. This part of the study will continue to assess safety and efficacy, including microperimetry, visual acuity, and macular structure, the company said in a press release. 

The interim 6-month data showed that 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, the company said, none of the 3 untreated control subjects and none of the 6 untreated contralateral eyes demonstrated foveal schisis closure. The company also noted that microperimetry response at Month 6 for Part B closely mirrors that observed for Part A at the same time point. In addition, a favorable safety profile was observed across all Part B cohorts. The company reported no serious adverse events (SAEs), no instances of macular hole formation or retinal detachment, and no subject discontinuations were observed. Also, subretinal deposits observed in a subset of subjects in Cohort 4 were resolved with transient steroid treatment. Finally, 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, the company said in the press release.

Part C of LIGHTHOUSE  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 2 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 US Food and Drug Administration (FDA) and the European Medicines Agency (EMA), with visual acuity and optical coherence tomography 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 filing in 2028, the company said.