Novel Gene Delivery Development for Spinal Muscular Atrophy

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DESCRIPTION (provided by applicant): Spinal muscular atrophy (SMA) is a genetic disorder characterized by the loss of lower motor neurons (LMNs) residing along the entire length of the spinal cord. SMA is caused by a reduction in the expression of the survival motor neuron (SMN) protein. The disease has an incidence of 1 in 6000, and in general, the earlier the symptoms, the shorter lifespan of patients. To date there are no effective therapies, particularly for the most severe forms of this lethal disease. Many lines of evidence support that increased amounts of SMN protein in motor neurons lessen disease severity. To date, therapeutic approaches have mainly focused on evaluating drugs for increasing SMN levels or enhance residual SMN function. Despite years of screening, no drugs have been identified to be fully effective for increasing SMN levels for a restorative therapy. Given the known genetic defect, in which SMN levels are decreased, gene replacement strategies may offer promise for SMA patients. New enhancements in viral vectors are demonstrating significant promise for a number of neurological disorders. This proposal seeks to develop novel gene delivery platforms based on a non-toxic, long-term expressing vector system; adeno-associated virus (AAV). While gene and drug delivery to the spinal cord has remained a challenge, we have recently discovered a unique ability for AAV serotype 9 to be highly efficient at delivering genes to spinal cord motor neurons of new born mice following vascular delivery. Indeed, in some areas of the spinal cord, over 90% of motor neurons were targeted by an AAV9-GFP marker gene, demonstrating the potential for AAV9 to be an effective gene delivery platform for SMA. Furthermore, we have demonstrated preliminary results that AAV9 is efficient at delivering genes to skeletal muscle across the entire body. These results are meaningful given that AAV9 targets both motor neurons and skeletal muscles, which are significantly affected in this disease. Our proposal seeks to further enhance this delivery platform in efforts to develop successful treatment strategies in SMA. This work will provide important information for translating an SMN gene replacement strategy to the clinic for SMA patients and provide needed information in efforts to develop an Investigational New Drug (IND) application. The aims of this proposal are specific goals for this NINDS developmental program to advance promising therapies to the clinic. Aim 1: Optimize vascular injection of AAV9-GFP to neonatal animals for maximal gene delivery to lower motor neurons. Aim 2: Evaluate optimal delivery of AAV9 expressing SMN for neonatal gene replacement in a mouse model of Type 2 SMA for improved function and survival. PUBLIC HEALTH RELEVANCE: Spinal muscular atrophy (SMA) is a genetic disorder characterized by the loss of lower motor neurons (LMNs) residing along the entire length of the spinal cord. To date, therapeutic approaches have mainly focused on evaluating drugs for increasing SMN levels or enhance residual SMN function. Despite years of screening, no drugs have been identified to be fully effective for increasing SMN levels for a restorative therapy. Given the known genetic defect, in which SMN levels are decreased, gene replacement strategies may offer promise for SMA patients. We have discovered a novel delivery platform for highly efficient targeting of motor neurons in neonatal animals. We will develop these findings for the potential to translate into human SMA clinical trials.