How fasudil works
SMA is a neurodegenerative disorder that affects voluntary muscle movement, due to the loss of motor neurons in the spinal cord. SMA has several subtypes, and most are caused by mutations in the SMN1 gene that makes the SMN protein required for motor neuron survival.
Research has shown that loss of the SMN1 gene function can result in increased levels of RhoA, a protein that is part of the RhoA-ROCK signaling pathway and regulates the formation of the actin cytoskeleton in nerve cells. The actin cytoskeleton provides a structural framework to the cell and its proper function is required for neurons to grow, branch out, and form neuromuscular junctions (NMJs), which are the point where a nerve cell and a muscle cell meet. An abnormal actin cytoskeleton due to increased Rho expression can result in neurons not forming proper NMJs, resulting in poor nerve cell signaling and muscle wasting.
Inhibiting the activity of Rho proteins using compounds such as fasudil may be able to restore proper actin cytoskeleton function in neurons and help them to form working NMJs.
Fasudil also acts directly on skeletal muscles, and aids in their development through enhanced expression of myogenin, a protein required for muscle formation.
Fasudil in pre-clinical studies
A pre-clinical study in a mouse model of SMA found that fasudil increased the life span of treated animals from 30.5 days to more than 300 days. While this longer life span is still only about half of that of healthy mice, fasudil treatment was also associated with increased skeletal muscle fiber size and improved development of NMJs over time. Fasudil administration did not work to increase levels of SMN protein or to preserve motor neurons. The results are “suggesting that the beneficial effects of fasudil could be muscle-specific,” the researchers wrote.
Higher doses of the drug were observed to be toxic to the animals.
Although fasudil is not approved for use as a therapy for any disease in the U.S., Canada, and Europe, it was approved by the Pharmaceuticals and Medicals Devices Agency (PMDA) of Japan in 1995 to treat cerebral vasospasm.
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