Applied Genetic Technologies Corporation reported updated interim three-month pediatric results and additional adult safety results out to as long as 24 months from its ongoing Phase 1/2 dose escalation study of AGTC-401. AGTC-401 is a recombinant AAV viral vector-based gene therapy targeting mutations in the CNGB3 gene in patients with achromatopsia (ACHMB3). Data from seven pediatric patients support previously reported findings from adults treated with AGTC-401, which demonstrated encouraging biologic activity and a favorable safety profile.

There were no new Suspected Unexpected Serious Adverse Reactions (SUSARs) and for the three previously reported SUSARs, the inflammation continues to improve with steroid treatment. Based on the totality of the ACHMB3 data generated to date from 31 patients over as long as 24 months, AGTC plans to advance the clinical development of AGTC-401 subject to consultation with the U.S. Food and Drug Administration (FDA) at an End-of-Phase 2 (EOP2) meeting in the first half of 2022. The Company also reported updated results from a parallel study of AGTC-402 targeting CNGA3 mutations in patients with achromatopsia that are consistent with previously reported results in adults, provide no indication of clinical improvements, and do not support further clinical development.

Most patients with CNGA3 mutations express a mutant protein that is not typically found in patients with CNGB3 mutations, which the Company believes may have impacted results seen in patients that received AGTC-402. AGTC will continue to follow the ACHMA3 patients for long-term safety observations. In the Phase 1/2 dose escalation study of AGTC-401 in ACHMB3 patients, a total of 21 adults were treated over a 100-fold dose range in five groups and a total of ten pediatric patients were treated at the three highest dose groups.

The primary purpose of any Phase1/2 clinical trial is to identify a well-tolerated dose that provides clinical benefit to patients. The Company believes that the data to date support that the 1.1E+12vg/mL dose is well tolerated and provides clinical benefit in both adult and pediatric patients. As previously reported, in both the ACHMB3 and ACHMA3 trials, treatment with the highest doses of AGTC-401 and AGTC-402, respectively, led to three cases of severe ocular inflammation in pediatric patients, which were reported as SUSARs.

No new additional SUSARs have been reported and the inflammation in all previously reported SUSARs improved with an adjusted steroid regimen. Two SUSARs (one in ACHMA3 and one in ACHMB3) have since fully resolved and one (ACHMA3) continues to resolve, with all three patients' best corrected visual acuity returning to baseline. Secondary outcome measures evaluating efficacy were assessed by standard visual function tests such as perimetry.

The company defined two pediatric patients (17 and 7 years old) in the 1.1E+12 vg/mL dose group as responders based on improvements in visual sensitivity. Therefore, of the three adults and four children (total n=7) in the 1.1E+12 vg/mL dose group, four (>50%) are visual sensitivity responders. These patients also had improvements in quality of life as measured by a patient reported outcome survey developed specifically for patients with achromatopsia.

The two other pediatric patients in the 1.1E+12 vg/mL dose group and three pediatric patients ages 7 years and younger in the 3E+12vg/mL dose group (total n=5) could not sufficiently concentrate and consistently complete the visual sensitivity testing. Similar to other trials where endpoints are adapted for young children, AGTC plans to work closely with clinicians and regulators to develop potential adaptations for younger patients for visual sensitivity testing. The Company is currently working on an EOP2 meeting package for the FDA and expects to receive feedback in the first half of 2022.

Subject to these discussions with FDA, the Company plans to initiate the next phase of AGTC-401 clinical development. The clinical program will be based on the favorable risk benefit profile of the 1.1E+12 vg/mL dose, which had a generally safe and well tolerated safety profile across all patients and signs of biologic response based on improvements in visual sensitivity and other measures of visual function.