TO 11: RSA F: ABBV-CLS-7262

This clinical trial will involve a Study Regimen for the study drug ABBV-CLS-7262 hypothesized to be important in the pathophysiology of amyotrophic lateral sclerosis (ALS) and other neurodegenerative conditions when activated chronically (Costa-Mattioli et al. 2020). Study Objectives Primary Efficacy Objective -- To evaluate the efficacy of ABBV-CLS-7262 on ALS disease progression. Secondary Efficacy Objective -- To evaluate the effects of ABBV-CLS-7262 on selected secondary measures of ALS disease progression, including survival. Safety Objectives -- To evaluate the safety of ABBV-CLS-7262 in patients with ALS. Pharmacokinetics Objective -- To quantify the steady state concentrations of A-1684909 and/or any active or inactive metabolites in plasma after long-term oral dosing of ABBV-CLS-7262 once daily (QD). Exploratory Objectives -- To evaluate the effects of ABBV-CLS-7262 on selected biomarkers and exploratory endpoints.