* Key Inclusion Criteria\*\*: * Subjects who are able to provide written informed consent form (ICF). * Subjects who are males or females must be ≥ 18 years and ≤ 80 years of age at the screening visit. * Subjects who have clinically definite ALS, clinically probable ALS, or clinically probable-laboratory supported ALS as specified in the revised version of the El Escorial World Federation of Neurology criteria. * Subjects must have an ALS disease duration (from first symptom onset to the screening visit) ≤ 2 years. * Subjects with a body mass index (BMI) ≥ 19 kg/m2 at the screening visit. * Subjects whose percent-predicted Forced Vital Capacity (%FVC) is ≥ 70% or percent-predicted Slow Vital Capacity (%SVC) is ≥ 60%, adjusted for sex, age, and height at the screening visit. * The ALSFRS-R score ≥ 30 during the screening period, and the three respiratory scores (dyspnea, upright respiration, and respiratory insufficiency) must be full marks. * Key Exclusion Criteria\*\*: * Serum Anti-AAV9 neutralizing antibody titer ≥ 1:100. * Current or previous exposure to gene therapy, stem cell products, and solid organ transplantation. * Subjects who have implanted or are estimated to require a diaphragmatic pacing system during the study period. * Any thromboembolic event, such as deep vein thrombosis, pulmonary arteriovenous embolism, and jugular vein embolism, has occurred within 6 months before the administration. * Suffering from autoimmune diseases or ongoing immune-related therapy, except intranasal, inhalation, ocular, topical, intra-articular corticosteroid therapy or corticosteroid physiological replacement therapy. * Active or chronic uncontrolled infection within 4 weeks before the administration, deemed unacceptable in the discretion of the investigator. * Evidence of human immunodeficiency virus (HIV) and treponema pallidum (TP) infection, as documented by the treatment for HIV or TP, or by HIV or TP antibodies positivity at the screening visit. * Has a positive serum pregnancy test at screening (females of childbearing potential only), a positive urine or serum pregnancy test at baseline (Day -1. females of childbearing potential only), or is nursing.