Spinal muscular atrophy

Spinal muscular atrophy, or SMA, is a genetic disease affecting motor neurons in the spinal cord and the control of muscle movement. It is caused by a mutation of the survival motor neuron gene 1, or SMN1, which affects nerve cells and leads to debilitating muscle function and sometimes fatal muscle weakness.1

There are four primary types of SMA based on age of onset and the manifestation of the disease. Type 1 is the most common and severe type of SMA and is usually diagnosed during an infant’s first six months. Type 2, diagnosed in children between the ages of 6 months and 2 years, results in a delay or failure to reach motor milestones. Children with Type 3, usually diagnosed before age 3 and sometimes as late as their teenage years, learn to walk but have mobility problems as they grow. Type 4 is rare, with mild motor impairment usually beginning after age 35.2,3 Approximately 50% of Type 3 patients with SMA are believed to maintain ambulatory function today and an increasing number of Type 2 patients with SMA are expected to remain ambulatory with the advent of complementary new therapies that can enable motor milestones.4

In collaboration with Astellas, Cytokinetics is developing a fast skeletal muscle troponin activator (FSTA) for the potential treatment of SMA.

  1. About SMA. Cure SMA. Available at: Accessed March 22, 2019.
  2. Types of SMA. Cure SMA. Available at: Accessed March 22, 2019
  3. Spinal Muscular Atrophy Fact Sheet. National Institute of Neurological Disorders and Stroke. Available at: Accessed March 22, 2019
  4. Zeres et al. Journal of Neurological Sciences 146 (1997) 67-72