Comparison of single versus dual vector delivery of AAV-SPY-DYS45-55 for Duchenne muscular dystrophy

PROJECT SUMMARY Comparison of single versus dual vector delivery of AAV-SPY-DYS45-55 for Duchenne muscular dystrophy MyoGene Bio is a startup dedicated to developing cutting edge therapies for muscle diseases. In this proposal, MyoGene Bio, in conjunction with research partners at UCLA, will advance development of our CRISPR/Cas9 gene editing therapeutic, SPY-DYS45-55, for Duchenne muscular dystrophy (DMD). Duchenne is a devastating muscle wasting disorder with no cure that is typically caused by out-of-frame mutations in the DMD gene. SPY-DYS45-55 removes a mutational hotspot in the DMD gene by generating an in-frame exon 45-55 deletion to restore the reading frame for half of all Duchenne patients. This deletion is associated with a very mild phenotype in human Becker muscular dystrophy patients. Systemic delivery of gene editing platforms to muscle represents a significant challenge. Certain serotypes of recombinant adeno-associated virus (AAV) have tropism to skeletal muscle and heart. However, due to the large size of SpCas9, dual vectors are required for delivery of SPY-DYS45-55. Dual AAV vectors could be problematic in that they may require higher amounts of virus to be injected, may be less efficient, and may increase manufacturing costs. These higher doses may be more likely to lead to serious adverse events. Thus, an alternative approach is to utilize SaCas9 (~1kb smaller) in a single vector. Here, AAV-SPY-DYS45-55 will be dosed as either a single or dual vector approach in our novel mouse model containing a mutated human DMD gene and dystrophin restoration and preliminary functional improvement will be assessed. Ultimately, these studies will generate important data for how to optimally deliver and translate SPY-DYS45-55, and potentially other CRISPR-based therapies, to patients with Duchenne muscular dystrophy.PROJECT NARRATIVE Comparison of single versus dual vector delivery of AAV-SPY-DYS45-55 for Duchenne muscular dystrophy In this proposal, MyoGene Bio will further develop our product, SPY-DYS45-55, a gene editing platform that permanently removes genetic mutations for approximately half of all Duchenne muscular dystrophy patients. This work will inform on the optimal delivery strategy for best restoration of the dystrophin protein which is otherwise lacking in Duchenne. Since Duchenne has no cure and only limited treatments, SPY-DYS45-55 offers a potential disease-modifying therapy for a large cohort of Duchenne patients.