According to a press release from the American Academy of Neurology published by EurekAlert, new research published in Neurology further suggests that established spinal muscular atrophy (SMA) drug nusinersen could be effective in treating older children and young adolescents.
Nusinersen, marketed and more commonly known in the United States as Spinraza, received FDA approval for the treatment of infant-onset SMA in the days preceding Christmas, 2016. The new study involved participants up to 15 years old who were monitored for periods approaching three years.
About Spinal Muscular Atrophy
Spinal muscular atrophy is a genetic disorder generally characterized by the progressive wasting of motor neurons, nerve cells that connect to and control muscle movement. Over time the muscles affected weaken and atrophy. Proximal (close to the center of the body) muscles and neurons are more commonly affected.
Individual cases of SMA vary widely in their severity and age of onset. To distinguish between the most common forms of the condition, SMA is divided into four subtypes numbered I-IV.
Type I, the most common and severe form of spinal muscular atrophy, affects children in their infancy and is frequently congenital. People born with type I SMA are unable to move their heads or sit up unassisted, and most don’t survive early childhood.
Type II develops in older babies, usually between 6 and 12 months of age. Type II SMA patients may eventually sit unassisted, but require support to stand or walk. These individuals often live into young adulthood.
People with type III and IV SMA have largely unaffected life expectancies. Type III is the childhood-onset form of the condition; type IV is the very rare adult-onset form. Individuals with type III may only require a wheelchair later in life, and those with type IV may only develop moderate muscle weakness.
About the Study
The Neurology study, supported in part by Spinraza manufacturer Biogen Inc., involved 28 patients with types II (11 participants) and III (17 participants) spinal muscular atrophy. Participants knowingly received two to three injections of nusinersen over a period of about three months.
The children were then observed for up to six months. Overall, researchers noted a significant improvement in the clinical status of the participants. One of the 11 participants with type II SMA started walking independently following a year and a half of treatment – most with type II SMA never walk.
Two of the four children with type III SMA who required walking assistance at the beginning of the study regained their ability to walk independently. Ambulatory type-III SMA patients walked an average 36 meters further in six-minute distance tests than they had before receiving treatment.
The results are highly encouraging for nusinersen, though the drug has already been approved by the FDA for all forms of spinal muscular atrophy. The small scale of the study, as well as the failure to include a control group, could potentially skew results – as such, the announcement should be taken with a gain of salt.
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