The Study of Safety and Preliminary Efficacy of ALT001 in Patients With MultIple System Atrophy-Cerebellar Type

Inclusion Criteria: * 1\. Age between 30 and 75 years inclusive, either sex; * 2\. Clinically established or clinically probable MSA-C as defined by the 2022 MDS diagnostic criteria for multiple system atrophy; * 3\. Duration of MSA-C-related motor symptoms, including ataxia, no longer than 5 years; * 4\. Score ≤ 3 on Item 14 of the Unified Multiple System Atrophy Rating Scale (UMSARS) Part II (motor examination); * 5\. Estimated life expectancy ≥ 1 year as assessed by the investigator; * 6\. Voluntary participation in this study and provision of written informed consent Exclusion Criteria: * 1\. Presence of other diseases that may cause ataxia at screening (e.g., infectious diseases, immune-mediated diseases, tumors, paraneoplastic conditions, hereditary disorders, trauma, nutritional deficiencies, toxic exposure, or other neurodegenerative diseases); * 2\. Dementia indicated by the Mini-Mental State Examination (MMSE) at enrollment (score ≤17 for illiterate individuals, ≤20 for primary school education, or ≤24 for junior high school or above) or a prior definitive diagnosis of dementia; * 3\. Evidence of other central nervous system pathologies on brain MRI at screening suggesting a diagnosis of neurodegenerative diseases other than MSA; or other significant pathological findings on brain MRI at screening, including but not limited to: cerebral hemorrhage, acute cerebral infarction, aneurysm, vascular malformation, infectious lesions, brain tumors, or other space-occupying lesions (meningiomas or arachnoid cysts with a maximum diameter \<1 cm do not require exclusion); * 4\. Presence of immune-mediated diseases that are inadequately controlled or require treatment with biologic agents; * 5\. Known history of allergies to biologic agents, such as proteins or cell-based products; * 6\. Receipt of any vaccination within the past 1 month; * 7\. Patients with a prior definitive diagnosis of malignancy or those currently receiving anti-tumor drug therapy; * 8\. Patients with a prior definitive diagnosis of epilepsy or those currently taking anti-epileptic drugs; * 9\. Presence of lumbar spine diseases or deformities, or other contraindications to lumbar puncture; * 10\. Coagulation abnormalities at enrollment (e.g., platelet count \<100 × 10⁹/L; prothrombin time \[PT\] \>3 seconds), a prior diagnosis of coagulation disorders such as hemophilia, or current use of two or more antiplatelet agents; * 11\. Contraindications to MRI (e.g., claustrophobia, implanted cardiac pacemaker, or ferromagnetic metal); * 12\. Concurrent severe hepatic insufficiency, renal insufficiency, or severe cardiac insufficiency (severe hepatic insufficiency defined as ALT ≥1.5 times the upper limit of normal or AST ≥1.5 times the upper limit of normal; severe renal insufficiency defined as serum creatinine \[CRE\] ≥1.5 times the upper limit of normal or estimated glomerular filtration rate \[eGFR\] \<40 mL/min/1.73 m²; severe cardiac insufficiency defined as NYHA class 3-4), or any significant abnormalities on physical examination, vital signs, laboratory tests, or electrocardiogram that, in the investigator's opinion, require further examination or treatment, or may interfere with the study procedures or safety; * 13\. Active hepatitis B infection (positive for hepatitis B surface antigen, recurrent/persistent ALT elevation, positive serum HBV DNA, or serum HBV DNA \>2 × 10⁵ IU/mL); * 14\. Positive for hepatitis C virus antibody or a history of positive test results; * 15\. Positive for HIV or a history of positive test results; * 16\. Patients with a history of alcohol or substance abuse, or alcohol or substance dependence within the past 2 years; * 17\. Diagnosis of psychiatric disorders, severe anxiety, severe depression, or obvious suicidal ideation according to DSM-V diagnostic criteria; * 18\. Patients who are pregnant, lactating, or have the potential to become pregnant, or those planning a pregnancy; * 19\. Current participation in other interventional trials or use of other investigational biologic agents, drugs, or devices, or use of other investigational drugs within the past 1 month or within 5 half-lives of the drug; * 20\. Inability to comply with follow-up assessments due to other reasons; * 21\. Patients deemed by the investigator to be unsuitable for participation in this study.