A Study of LY4256984 in Participants With Sporadic Amyotrophic Lateral Sclerosis

Inclusion Criteria: * Have a definite, possible, or probable diagnosis of sporadic amyotrophic lateral sclerosis (ALS) made by a physician experienced with the management of ALS * ALS symptom onset as determined by the Investigator within 24 months of Screening * Have a body mass index (BMI) within the range of greater than or equal to 18.0 and less than or equal to 35.0 kilogram per square meter (kg/m²) (inclusive) Exclusion Criteria: * Have a history or presence of medical illness including, but not limited to, any cardiovascular, renal, hepatic, gastrointestinal, respiratory, hematological, endocrine, psychiatric, or neurological disease, convulsions, or any clinically significant laboratory abnormality * Have a history of another neurodegenerative disease or significant dementia/severe cognitive problems * Have serum alanine aminotransferase (ALT), aspartate transferase (AST), or total bilirubin levels greater than 2 x upper limit of normal. * Have a significant renal impairment (estimated glomerular filtration rate \<60 milliliters per minute \[mL/min\]/1.73 m²). * Have a 12-lead electrocardiogram (ECG) abnormality at screening, in the opinion of the investigator, that increases the risks associated with participating in the study * Show clinically significant abnormalities in lumbar spine previously known or determined by screening lumbar X-ray or fluoroscopy (if performed)