Combining a muscle-tropic AAV capsid with a muscle-specific promoter enhances skeletal muscle gene delivery while reducing off-target expression

Abstract

Viral vector technologies based on adeno-associated viruses (AAVs) have demonstrated promising ability to deliver genetic cargo to a range of organs in vivo, with several novel candidates showing clinical efficacy in human trials over the past decade. However, naturally occurring AAV serotypes are limited in their ability to target skeletal muscle, an important gene therapy target for many neuromuscular disorders. This means that high doses of natural AAV serotypes are required to achieve therapeutically effective doses in muscle. To overcome this, novel AAV vectors that achieve greater muscle transduction efficiency have been engineered by inserting targeting peptides into the AAV9 capsid variable regions. Here, we describe the investigation of a reported muscle-homing capsid, MyoAAV1A, combined with a clinically validated muscle-specific promoter, MHCK7. We profiled in vivo delivery efficiency to murine skeletal muscle and found that the combination of MyoAAV1A with the MHCK7 promoter maintains transgene expression in skeletal muscle, and reduces off-target expression, particularly in the liver. This highlights a promising capsid-promoter combination to progress in future preclinical research for skeletal muscle gene therapy.