Project Summary/Abstract
1 in 500 newborns suffers from genetic hearing loss (HL), and there are no FDA-approved drugs or biological treatments
for any type of HL. Genome editing that disrupts or repairs DNA mutations or modulates RNA levels is being developed
into new therapies for many diseases. Despite the unprecedented progress, the translation of genome editing into therapy
in humans has been challenging due to the obstacles in delivery, safety, and efficacy. This is particularly relevant for in
vivo editing therapy due to the added complexity, including damped editing efficiency, inefficiency in reaching the target
cells, and the lack of evidence of translatability from animal (mouse) into humans. In this proposal, we will develop first-
in-class CRISPR-Cas-based therapeutics for genetic hearing loss by conducting IND-enabling studies of AAV2-mediated
delivery of SaCas9-KKH/gRNA to target two dominant genetic hearing loss, DFNA41 due to a P2RX2 mutation and
DFNA2 due to a KCNQ4 mutation. This project will be conducted by a consortium of five core teams with unique and
complementary expertise and experience in gene and editing treatments for genetic hearing loss, from animal models to
human trials, editing technology, and regulatory processes. We have recently conducted the first successful gene therapy
of OTOF clinical trial by dual adeno-associated virus (AAV) that leads to hearing restoration in children with congenital
genetic hearing loss DFNB9, which included a safety study of AAV in non-human primates (NHPs) and the development
of a minimally invasive surgical procedure for AAV inner ear delivery in humans. We have further developed a large
animal pig model of dominant genetic hearing loss DFNA36 by inserting a mutation into the TMC1 gene and successfully
rescued hearing in the pig model by local AAV delivery of editing complex, demonstrating the cross-species
translatability of editing therapy for genetic hearing loss. For the current proposal, we have obtained the therapeutic
benefit of hearing rescue results by AAV2 delivery of SaCas9-KKH/gRNA to treat DFNA41 and DFNA2 mouse models,
which lays the foundation of an IND-enabling study. Leveraging our unparalleled expertise and experience in human
genetic hearing loss, including efficacious editing treatment in mouse and pig models, AAV safety study in NHP, and the
first successful human gene therapy clinical trial, we will conduct the following studies: 1). Establish off-target editing
profiles in human cells and human inner ear tissues; 2). Efficacy study by escalating doses of AAV2 in DFNA41 and
DFNA2 mouse models; 3). Biodistribution and toxicity study in WT mice by an escalating dose of AAV2; 4).
Biodistribution and toxicity study of GLP grade AAV2 in NHP; 5). Patient natural history study, and 6). Regulatory
Interactions & IND completion. We have assembled a team of experts in each area with a project manager to execute the
plan, develop a streamlined regulatory path for two types of DFNA deafness, and disseminate this regulatory information
to the scientific community. Successful completion of the IND-enabling studies makes our approach applicable to over 20
dominant genetic hearing loss due to hair cell mutations.
