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Current and investigational treatments for spinal muscular atrophy

Introduction: Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder in humans characterized by impaired motor neuron function resulting in muscle weakness and atrophy. It is clinically classified into four main types based on age of onset and clinical severity. SMA is caused by a reduced level of functional survival motor neuron (SMN) protein. The physiological relevance of SMN has been implicated in pre-mRNA splicing and its critical involvement in cellular processes in the axons of motor neurons. Areas covered: At present, no effective treatment is available for SMA. Current therapeutic strategies for treating SMA focus on SMN expression augmentation and the development of neuroprotective agents. Preclinical successes from approaches including gene therapy, antisense oligonucleotides, small molecule drugs and stem cell technology have been described and their clinical relevance has been discussed. However, clinical trials of drug compounds conducted hitherto have not shown conclusive evidence to support any particular type of drug compound as an effective intervention for curing SMA patients. Expert opinion: Among the current therapeutic strategies, vector-based gene therapy is one of the most promising candidates for treating SMA. Its success and safety demonstrated in preclinical studies in mouse models and non-human primates have given us optimism in translating the technology into the clinic. Major challenges yet to be addressed are the efficient penetration of the blood-brain-barrier, the route of delivery that maximizes global distribution with a minimal invasive technique to the patient and the timing of the treatment for patients to achieve the highest therapeutic benefits.