Re-administration of AAV-mediated gene therapy for OTOF-related deafness: a single-arm trial

Re-administration of adeno-associated virus (AAV)-mediated gene therapy remains challenging due to neutralizing antibodies (NAbs) induced by the initial dose. We previously conducted a single-arm trial showing that single-dose administration of AAV-hOTOF gene therapy in individuals with OTOF-related deafness is safe and leads to hearing improvements. Here we initially demonstrate that AAV1-hOTOF re-administration to the contralateral ear in Otof^-/- mice with peak serum NAb titers successfully rescued hearing with limited immune activation. After a protocol amendment of our trial, four patients (aged 2.2-3.4 years) with pre-existing NAbs (titers 1:135-1:3,645), who had previously received a single dose of the gene therapy, were enrolled to receive a second dose in the contralateral ear, as part of the ongoing trial, with a follow-up ranging from 26 weeks to 52 weeks. The primary endpoint was the occurrence of dose-limiting toxicities at 6 weeks and secondary endpoints included safety and auditory function. No dose-limiting toxicity occurred within 6 weeks. In the secondary outcomes, the 26-week average auditory brainstem response threshold in the second treated ear improved from >95 dB at baseline to 43 dB, 63 dB, 80 dB and 53 dB in patients 1-4, respectively. Safety assessment showed that all adverse events were grade 1-2, except one grade 3 decreased neutrophil count; no serious adverse events occurred. These data provide preliminary insights on the safety and efficacy of re-administration of AAV1-hOTOF gene therapy in patients with congenital deafness. Longer follow-up and larger cohorts are needed to establish the safety and efficacy of repeated administration of gene therapies. Trial registration no.: ChiCTR2200063181 .