Inclusion Criteria:  Must have an identified, reliable caregiver Confirmed diagnosis of Familial ALS or Sporadic ALS First ALS symptoms occurred ≤36 months before screening Able to swallow solids No known active COVID-19 infection at screening Vital capacity ≥50% predicted value (for sex, age, ethnic origin, and height) at screening  Exclusion Criteria:  History of dementia/severe cognitive problems at screening Use of riluzole (Rilutek®) at a dose which has NOT been stable for >1 months prior to Baseline. Use of edaravone (Radicava®) within 1 month prior to screening or intention of initiating edaravone within 3 months after receiving the first dose of ABBV-CLS-7262. History of clinically significant medical conditions (other than ALS) or any other reason, including any physical, psychological, or psychiatric condition that, in the opinion of the Investigator, would compromise the safety or interfere with the subject's participation in the study, or would make the subject an unsuitable candidate to receive study drug, or would put the subject at risk by participating in the study. History of abnormal screening laboratory or imaging results that, in the opinion of the Investigator, are indicative of any significant cardiac, endocrinologic, hematologic, hepatic, immunologic, infectious, metabolic, urologic, pulmonary, gastrointestinal, dermatologic, psychiatric, renal, neurologic, and/or other major disease that would preclude administration of ABBV-CLS-7262. If female, is known to be pregnant, breastfeeding, considering becoming pregnant, or donating/banking eggs during the study or within 30 days or >5 half-lives (whichever is longer) after the last dose of study drug If male, plans to donate sperm or father a child during the study or within 30 days after the last dose of study drug. Known to have received any investigational product within 30 days or 5 half-lives of the drug (whichever is longer) prior to the first dose of study drug or is currently enrolled in another clinical study. History of ABBV-CLS-7262 use prior to participation in this study Recent (within 6 months prior to Screening) history of drug or alcohol abuse Previous participation in a stem cell clinical study Current or anticipated use of diaphragmatic pacing during the study period Tracheostomy or use of non-invasive ventilatory support ≥22 hours a day