Lysogene S.A. announced that, following discussions with the U.S. Food and Drug Administration (FDA), a clinical hold was issued for the clinical trial AAVance (NCT03612869), a global Phase 2/3 clinical trial of LYS-SAF302, a gene therapy for the treatment of Mucopolysaccharidosis Type IIIA (MPS IIIA, also known as Sanfilippo syndrome type A). To date, 19 out of 20 patients have been treated, and all patients remain in the study and are being followed per study protocol. The primary and secondary trial endpoints are based on the analyses of these 19 patients already enrolled and there is no anticipated impact on the current clinical trial timelines. The clinical hold follows observations in some patients of localized findings on MRI images at the intracerebral injection sites. The localized nature of the findings suggests a potential connection to delivery. To date, no clinical symptoms have been observed that could be directly attributed to the observed MRI findings and all findings have been reported to competent authorities, ethics committees and the trial’s DSMB (Data Safety Monitoring Board). All trial participants continue to be closely monitored by their care teams. A path forward has been discussed with FDA, and Lysogene looks forward to gathering additional information to better understand the safety profile of LYS-SAF302.