A New Strategy to Treat SMA in Infants

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According to Medical Xpress, scientists have pinpointed how a potentially new treatment effectively targets spinal muscular atrophy (SMA). The results from the research could lead to further development in SMA treatments but also development of treatments for other genetic diseases as well.

Spinal muscular atrophy, often abbreviated as SMA, is a rare genetic disorder that causes muscle weakness and degeneration. In infants with SMA, many experience trouble breathing and die before the age of two. Most cases of SMA are caused by a mutation in the SMN1 gene. There are four types of SMA, distinguished by the age it affects patients and the severity of the condition. There is no known cure for this condition. To read more about SMA, click here.

Although there is no cure for SMA, researchers and doctors are working to find a way to stop the progression of the disease. In fact, up until recently, there had been no effective treatment for the condition. The recently approved drug nusinersen was a breakthrough for patients with the condition, and now researchers are pushing the envelope for more options.

A potential drug on the horizon is RG-7916, and it is currently in a phase II clinical trial through the pharmaceutical company Roche. To run this study, co-lead author of the study Kristen Johnson, PhD, looked at molecules that are analogous to RG-7916 to get a better understanding of the how RG-7916 functions.

“Understanding the mechanisms behind drugs is so critical for treating the right kinds of patients,” Johnson says.

“Plus, the more you understand about the mechanism of a drug, the better physicians can watch out for possible side effects.”

Scientists concluded that in order for RG-7916 to be truly effective, it would require RNA mis-splicing. It turns out that RNA mis-splicing is active in not only SMA but for a variety of other genetic diseases like Menkes disease.

These diseases all share a common denominator, and that is something wrong with the process in which the cell reads and interprets the genetic code, which is needed to produce proteins. During the process, the genetic information must be cut up and spliced into functional bits of information.

Specifically, for SMA, assembly of the protein SMN (survival of motor neuron) is blocked and spliced mistakenly.

The authors of the study, along with co-leader Peter Schultz, PhD, president of Scripps Research, found that similar molecules to RG-7916 did in fact correctly attack the SMN2 sequence that is known for causing SMA.

When the drug molecule similar to RG-7916 was set in place, the pre-RNA sequence was spliced and cut up correctly and a fully functional SMN protein was the outcome.

Johnson explains this in more depth: “This drug basically allows the equipment that drives splicing—which we call splicing enhancers—to sit on the preRNA in right location. This causes the right fragmenting of the RNA so it produces the right protein.”

Another added bonus surrounding this discovery is that RG-7916 also attaches to a closeby protein, and this combination makes the treatment even more specified for targeting the mutation.

Johnson is hopeful about the future of this development, and says “the complementary studies are an encouraging sign that RG-7916 is on the right track, although it will still need to pass key toxicology studies and clinical studies.”

For now, Johnson is also focusing on seeing how this new finding can assist more patients, like older kids with less severe types of SMA.

This research is not only groundbreaking for SMA in infants, but also could potentially have implications for other types of SMA as well as other diseases too. To read more about the research, click here.


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