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Spinal muscular atrophy is a genetic disease that affects the part of the nervous system that controls voluntary muscle movement. SMA involves the loss of the spinal nerve cells called motor neurons.
Most forms of SMA are caused by mutations in a gene called SMN, which stands for "survival of motor neurons," although there are also non-SMN-related forms of SMA. The age of onset and disease severity relate to the level of SMN protein produced.
SMN-related SMA is usually broken down into three main categories. Type 1 is the most severe with the earliest age of onset, and type 3 is the least severe, with the latest age of onset. Some doctors add a type 4 for moderate or mild SMA that begins in adulthood.
Research Pipeline
Although there are methods to manage the symptoms of SMA, there are currently no drugs for any forms of SMA. Recent discoveries in SMA research, however, have resulted in a better understanding of the disease mechanism, and have resulted in a large number of new therapies in development.
Many of these approaches are genetic approaches, not dissimilar to those used in the muscular dystrophies. These approaches aim to either repair or replace the mutated gene, SMN1, or upregulate other genes that can perform the same function. Indeed, some of the same drugs under development for other genetic disorders may be applicable to SMA. Other potential SMA drugs may overlap with ALS therapies, as both diseases result in degeneration of motor neurons.
Research Strategies
As of 2011, there are at least eight companies working on potential SMA therapies. Strategies to treat SMA include:
- Drugs that increase the amount of SMN2 (a protein very similar to SMN1) produced by the body.
- Drugs that encourage cells to include a section of the SMN2 gene called exon 7, which stabilizes the SMN2 protein.
- Drugs that allow the body to ignore specific types of mutation that can cause SMA.
- Gene-replacement techniques through which a functional copy of SMN1 can be introduced through gene therapy.
- Drugs that protect motor neurons from degeneration.
- Stem cell therapies that are designed to either support existing motor neurons, and/or to replace them with new motor neurons.
A Trial and Reason to Hope
MDA has funded a large number of studies into SMA therapies through its main research program, including a clinical trial of hydroxyurea in SMA type I patients. Results from this trial should be published soon.
SMA is a disease with exciting opportunities for therapies, and there are many new strategies that have real potential to help people with SMA.
MVP recently awarded Repligen Corp. $1,423,247 to get a novel SMA drug into a Phase I trial. The compound upregulates SMN protein, and MVP funding will allow the company to finish the necessary preclinical testing to get the drug ready for patient trials, and to complete Phase I trials in both healthy volunteers and SMA patients. |
