Therapeutic AAV9-mediated Suppression of Mutant SOD1 Slows Disease Progression and Extends Survival in Models of Inherited ALS

Abstract

Mutations in superoxide dismutase 1 (SOD1) are linked to familial amyotrophic lateral sclerosis (ALS) resulting in progressive motor neuron death through one or more acquired toxicities. Involvement of wild-type SOD1 has been linked to sporadic ALS, as misfolded SOD1 has been reported in affected tissues of sporadic patients and toxicity of astrocytes derived from sporadic ALS patients to motor neurons has been reported to be reduced by lowering the synthesis of SOD1. We now report slowed disease onset and progression in two mouse models following therapeutic delivery using a single peripheral injection of an adeno-associated virus serotype 9 (AAV9) encoding an shRNA to reduce the synthesis of ALS-causing human SOD1 mutants. Delivery to young mice that develop aggressive, fatal paralysis extended survival by delaying both disease onset and slowing progression. In a later-onset model, AAV9 delivery after onset markedly slowed disease progression and significantly extended survival. Moreover, AAV9 delivered intrathecally to nonhuman primates is demonstrated to yield robust SOD1 suppression in motor neurons and glia throughout the spinal cord and therefore, setting the stage for AAV9-mediated therapy in human clinical trials.

Protective and Toxic Neuroinflammation in Amyotrophic Lateral Sclerosis

“…This approach includes the use of interfering RNA to decrease production of misfolded toxic proteins. These techniques have lead to success and positive results in animal models [150,151]. Currently, this approach is being translated in the clinic to patients with ALS; however, no long-term outcome data have been published [152].…”

Intravenous Injections in Neonatal Mice

“…Similar results were also obtained in the same SMA mouse model following IV injection of antisense oligonucleotides 8,9 . Future applications include the delivery of other cell and gene therapies, as well as the creation of neonatal models for developmental disorders of the CNS and the periphery to exogenously express a cDNA or an RNAi cassette 24 . Intravenous injection is an approved clinical method of delivery; therefore, utilization of this technique may be advantageous in preclinical studies for a variety of agents.…”

Current developments in gene therapy for amyotrophic lateral sclerosis

“…Lifespan was extended by up to 39% when treatment was initiated at birth in G93A mice and SOD1 protein levels in motor neurons and glial cells were significantly reduced in non-human primates treated with the therapeutic shRNA construct. The group also demonstrated the ability of AAV9 to efficiently transduce motor neurons and astrocytes in vivo, a property essential to any viral gene therapy delivery system aimed towards translation into human trials [69].…”

“…AAV and LV-based vectors show strong potential for delivering shRNA to knockdown SOD1 mRNA in ALS mouse models [67][68][69]. Briefly, AAV vectors provide long-term transgene expression, show minimal pathogenicity, low immunogenicity and are easy to manufacture at high titers in large-scale production for research.…”