Spinraza and SMA by Jonathan Smith

Individuals with SMA experience a loss of motor neurons - the nerve cells responsible for the generation of impulses which produce movement in the limbs and body - in the spinal cord. This is due to a genetic defect affecting the SMN1 gene which produces the Survival Motor Neuron Protein (SMNP). Over time, insufficient levels of SMNP lead to a decline in the number of motor neurons within the spinal cord, resulting in a loss of movement, muscle weakness, and reduced function and independence. Individuals with SMA retain some movement due to the presence of a less powerful version of the SMN1 gene called SMN2 (Scientists like to keep things simple!)

“...so far, Spinraza has managed to satisfy the criteria for safety and effectiveness”

Spinraza, when injected directly into the central nervous system, effectively converts the less powerful SMN2 gene into SMN1, which produces normal amounts of SMNP and therefore prevents loss of motor neurons and the functional issues that come with muscle weakness in SMA. For anyone feeling confused at this point, that’s the science bit over, and the outcome is that this is ‘so far, so good’ for Spinraza as a treatment for SMA! Therapeutic drugs have to pass through a multitude of hoops before they can be approved for license to use on actual human beings and, so far, Spinraza has managed to satisfy the criteria for safety and effectiveness.

So much so that in December 2016 it was granted approval from the Food and Drug Administration in the USA for use in SMA, and additional funding was provided. An article published in the Lancet in 2016 demonstrated the effects of Spinraza on a group of SMA infants <7 months old, noting improvements in motor function and survival rates in the majority of participants.
http://thelancet.com/journals/lancet/article/ PIIS0140-6736(16)31408-8/abstract)