The effect of the DcpS inhibitor D156844 on the protective action of follistatin in mice with spinal muscular atrophy

• D156844/follistatin treatment increases the average lifespan of and delays disease end stage in SMNΔ7 SMA mice.
• D156844/follistatin treatment further increases growth rate over follistatin.
• D156844/follistatin treatment further improved motor impairments over follistatin or D156844.

Spinal muscular atrophy (SMA), a leading genetic cause of pediatric death in the world, is an early-onset disease affecting the motor neurons in the anterior horn of the spinal cord. This degeneration of motor neurons leads to loss of muscle function. At the molecular level, SMA results from the loss of or mutation in the survival motor neuron 1 (SMN1) gene. The number of copies of the nearly duplicated gene SMN2 modulates the disease severity in humans as well as in transgenic mouse models for SMA. Most preclinical therapeutic trials focus on identifying ways to increase SMN2 expression and to alter its splicing. Other therapeutic strategies have investigated compounds which protect affected motor neurons and their target muscles in an SMN-independent manner. In the present study, the effect of a combination regimen of the SMN2 inducer D156844 and the protectant follistatin on the disease progression and survival was measured in the SMNΔ7 SMA mouse model. The D156844/follistatin combination treatment improved the survival of, delayed the end stage of disease in and ameliorated the growth rate of SMNΔ7 SMA mice better than follistatin treatment alone. The D156844/follistatin combination treatment, however, did not provide additional benefit over D156844 alone with respect to survival and disease end stage even though it provided some additional therapeutic benefit over D156844 alone with respect to motor phenotype.