Open-Label Treatment Phase (36 weeks) At the Baseline visit, subjects will return to the clinic and the following assessments will be performed/administered: review of inclusion and exclusion criteria for continued eligibility, vital signs, blood for safety labs and biomarkers, ECG, ALSFRS-R questionnaire, slow vital capacity (SVC), baseline strength as measured by hand held dynamometry (HHD), and Columbia Suicide Severity Rating Scale (C-SSRS). At this visit, study drug will be dispensed, and adverse events, concomitant medications and therapies will be assessed and documented. At subsequent visits during the Treatment Phase, similar assessments will be performed.