The Food and Drug Administration (FDA) has granted Orphan Drug designation to reldesemtiv (Cytokinetics) for the treatment of amyotrophic lateral sclerosis (ALS). 

Reldesemtiv is believed to work by slowing the rate of calcium release from the regulatory troponin complex of fast skeletal muscle fibers. This then sensitizes the sarcomere, a functional unit of skeletal muscle, to calcium, leading to an increase in muscle contractility. 

A phase 2 trial (FORTITUDE-ALS; N=458) evaluating the efficacy, safety and tolerability of reldesemtiv showed that the investigational treatment did not achieve its primary end point of significant change from baseline in the percent predicted slow vital capacity (SVC) after 12 weeks of dosing (P =.11). However, patients treated with reldesemtiv were found to have declined numerically less than those administered placebo for SVC and ALS Functional Rating Scale-Revised (ALSFRS-R), with larger differences emerging over time. As for safety, the most common treatment-emergent adverse effects were fatigue, nausea and headache. 

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“We believe treatment with reldesemtiv may represent a complementary approach to other potential therapies by directly addressing impaired muscle function and weakness that affects patients with ALS,” said Fady I. Malik, MD, PhD, Cytokinetics’ EVP of Research and Development.

In addition to ALS, Cytokinetics is investigating reldesemtiv for the treatment of spinal muscular atrophy, for which it was granted Orphan Drug status as well. 

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