AMX0114 in Adult Participants With Amyotrophic Lateral Sclerosis

Inclusion Criteria: 1. Ability to understand the purpose and risks of this study, willingness to comply with the study and to provide informed consent in accordance with local laws and regulations. 2. Male or female, at least 18 years of age. 3. Diagnosis of clinically definite or clinically probable ALS, made by a physician who is experienced with management of ALS. 4. Time since onset of first symptom of ALS should be \<24 months prior to beginning the study. Date of ALS symptom onset is defined as the onset of weakness (in the limbs, bulbar region, or trunk). 5. If the participant is to be treated with riluzole and/or edaravone before or during the trial, then treatment must be previously started and maintained at a stable regimen for at least 30 days prior to starting the study and through the end of the study. 6. Women of childbearing potential (e.g., not post-menopausal for at least one year or surgically sterile) must agree to use an acceptable birth control method for the duration of the trial and 60 days after the last dose of Study Drug or be of non-childbearing potential. 7. Female participants or female partners of male participants must not be pregnant or plan to become pregnant for the duration of the trial and for up to 90 days after the last dose of Study Drug. 8. Male participants must agree to abstain from sperm donation for the duration of the trial and practice contraception with a female partner, for at least 90 days after last dose of Study Drug. Exclusion Criteria: 1. Presence of tracheostomy or permanent assisted ventilation. 2. SVC less than 65%. 3. Abnormal liver function defined as aspartate aminotransferase and/or alanine aminotransferase \> 3 times the upper limit of normal (ULN) and/or total bilirubin \> 1.5 times the ULN (obtained within 4 weeks of first dose) except when a result of Gilbert syndrome. 4. Abnormal renal function defined as estimated glomerular filtration rate (eGFR) \< 60 mL/min/1.73m2. 5. Other laboratory abnormalities, including abnormalities in platelet count, international normalized ratio, prothrombin time, and activated partial thromboplastin time. 6. Pregnant women (confirmed by a pregnancy test within 7 days prior to first dose) or women currently breastfeeding. 7. Current or previous clinically significant, unstable medical condition (other than ALS), that in the opinion of the Investigator could affect a participant's safety or ability to comply with the study. 8. Significant abnormalities in physical/neurological examination, vital signs, or electrocardiogram (ECG), which in the opinion of the Investigator could affect the safety of the participant. 9. Presence of unstable psychiatric disease, cognitive impairment, dementia or substance abuse that could affect the participant's ability to provide informed consent or comply with study procedures. 10. Current or previous enrollment in another trial involving use of an investigational therapy, in most cases within 30 days after the last dose of the study drug, prior to starting this study. 11. Current or previous treatment with small interfering ribonucleic acid, stem cell therapy, any ASO or gene therapy. 12. Any contraindications for lumbar puncture or repeated intrathecal injection and/or underlying disorders that could be affected by intrathecal injections. 13. Prior severe reaction or known hypersensitivity to any part of the Study Drug.