Phase 1 Gene Therapy for Duchenne Muscular Dystrophy Using a Translational Optimized AAV Vector

Abstract

Efficient and widespread gene transfer is required for successful treatment of Duchenne muscular dystrophy (DMD). Here, we performed the first clinical trial using a chimeric adeno-associated virus (AAV) capsid variant (designated AAV2.5) derived from a rational design strategy. AAV2.5 was generated from the AAV2 capsid with five mutations from AAV1. The novel chimeric vector combines the improved muscle transduction capacity of AAV1 with reduced antigenic crossreactivity against both parental serotypes, while keeping the AAV2 receptor binding. In a randomized double-blind placebo-controlled phase I clinical study in DMD boys, AAV2.5 vector was injected into the bicep muscle in one arm, with saline control in the contralateral arm. A subset of patients received AAV empty capsid instead of saline in an effort to distinguish an immune response to vector versus minidystrophin transgene. Recombinant AAV genomes were detected in all patients with up to 2.56 vector copies per diploid genome. There was no cellular immune response to AAV2.5 capsid. This trial established that rationally designed AAV2.5 vector was safe and well tolerated, lays the foundation of customizing AAV vectors that best suit the clinical objective (e.g., limb infusion gene delivery) and should usher in the next generation of viral delivery systems for human gene transfer.

Single Amino Acid Modification of Adeno-Associated Virus Capsid Changes Transduction and Humoral Immune Profiles

“…The resulting AAV2.5 mutant was found to transduce skeletal muscle with an efficiency higher than that of AAV2 but lower than that of AAV1. Interestingly, the AAV2.5 mutant displayed a unique NAb profile different from those of AAV1 and AAV2 and was capable of promoting higher transgene expression levels in mice preimmunized against AAV2 (7). In this study, we further elucidated that the insertion of single amino acid at residue 265 of AAV2 VP1 changed the humoral immune profiles as well as the efficiency of muscle transduction.…”

“…A similar phenomenon was demonstrated with the NAb profiles of AAV1 and AAV2.5 capsids (7). These observations suggested that the engineered AAV2.5 mutant has a unique NAb profile and might therefore facilitate repeat administration (7).…”

Engraftment of a Galactose Receptor Footprint onto Adeno-associated Viral Capsids Improves Transduction Efficiency

“…For instance, AAV2i8G9 is a one-of-akind, chimeric strain that can potentially serve as a vector candidate for selective gene transfer to cardiac and musculoskeletal tissue through intravenous infusion. Specifically, the selective muscle tropism and ability to avoid liver sequestration makes AAV2i8G9 an optimal vector for systemic gene therapy of muscular dystrophies (33)(34)(35). We determined recently that the strain described previously, AAV2i8, yields sustained transgene expression levels in primate muscle tissue 3 .…”

Adeno-Associated Viral Vectors Based on Serotype 3b Use Components of the Fibroblast Growth Factor Receptor Signaling Complex for Efficient Transduction

“…We have shown that replacing critical amino acids in the AAV2 and AAV3b capsid with the corresponding amino acids from AAV1 confers enhanced skeletal and cardiac muscle transduction (Bowles et al, 2012;Piacentino et al, 2012). In the next set of experiments we evaluated the influence of heparin on the more efficient version of the AAV3b capsid, termed SASTG (Piacentino et al, 2012).…”