SMA – Spinal muscular atrophy

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 SMA is related to 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 relates to the level of SMN protein produced.

SMN-related SMA is usually broken down into three 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

Stage of Development of Treatments for Spinal Muscular Atrophy

There are no treatments for any of the forms of SMA. Recent discoveries in SMA research, however, have resulted in a better understanding of the disease mechanism, and have recently 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 up-regulate other genes that can perform the same function. Indeed, some of the same drugs, such as MDA-sponsored PTC-124 may be able to be used to treat both diseases. Other potential SMA drugs may overlap with ALS therapies, as both diseases result in degeneration of nerves.

Research Strategies

In 2008, there are 16 companies working on potential SMA therapies. Strategies to treat SMA include:

  • Gene therapy to replace the mutated gene
  • Treatment with neuroprotective growth factors
  • Up-regulation of other genes that can replace SMN1
  • Genetic treatments to coax the cells to "read through" or "ignore" the mutation
  • Genetic treatments to cause production of the protein missing in the mutated area
  • Treatments which prevent nerve cell death
  • Stem cell treatments to promote nerve growth or boost surviving cells

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. This trial is ongoing.

SMA is a disease with exciting new opportunities for therapies, and there are many new strategies which have real potential to help people with the disease.