The Safety and Tolerability Study With ER2001 Intravenous Injection in Adults With Early Manifest Huntington's Disease

Inclusion Criteria:

1. Patient has documented ability to understand the written study informed consent forms (ICFs) at the time of screening and has provided signed written informed consent priorto any study procedures.
2. 25 Years to 55 Years. Gender is not limited.
3. Early manifest HD as defined by a UHDRS total functional capacity (TFC) score of 9 to 13 and a diagnostic classification level (DCL) of 4.
4. HTT gene expansion testing with the presence of ≥40 CAG repeats.
5. Ability to undergo and tolerate MRI scans.
6. Ability to undergo and tolerate lumbar puncture.
7. All HD medications given for motor, behavioral, and cognitive symptoms have beenstable for 3 months prior to Screening.
8. Other concomitant medications have been stable for 1 month prior to Screening.
9. organ function measured prior to administration of study treatment.
10. Postmenopausal or evidence of non-childbearing status for women of childbearingpotential. Male patients must use a condom during treatment and for 6 months after thelast dose of ER2001 when having sexual intercourse with a pregnant woman or with awoman of childbearing potential. Female partners of male patients should also use ahighly effective form of contraception if they are of childbearing potential.

Exclusion Criteria:

1. History of attempted suicide or suicidal ideation with plan (i.e., active suicidalideation) that required hospital visit and/or change in level of care within 12 monthsprior to screening.
2. Current active psychosis, confusional state, or violent behavior.
3. Bleeding tendency or history of coagulation disorder; As long as the investigatorconfirms that there is no evidence of bleeding tendency or coagulation dysfunction atpresent.
4. ECG with corrected QT interval (QTc) > 480 ms and/or indication of uncontrolledcardiac conditions, as judged by the investigator (e.g. unstable ischemia,uncontrolled ventricular arrhythmia, recent (within 3 months) myocardialinfarction,congestive heart failure, electrolyte disturbances, etc.)
5. Patients with HIV, Treponema pallidum, Hepatitis B, or Hepatitis C infection.
6. Need to take antiretroviral drugs, including antiretroviral drugs as preventivetreatment.
7. Current or recurrent disease, infection, or other significant concurrent medicalcondition or medications that could confound clinical and laboratory evaluations orcould affect a subject's safety or their ability to undergo the neurosurgicalprocedure or comply with the procedures and study visit schedule.
8. Clinical diagnosis of chronic migraines.
9. Presence of an implanted deep brain stimulation device, ventriculoperitoneal or otherCSF shunt, or other implanted catheter.
10. Preexisting structural brain lesions (such as tumor, arteriovenous malformation) asassessed by a centrally read MRI scan during the screening period.
11. Any history of gene therapy, RNA or DNA investigational agents, such as antisenseoligonucleotides (ASO), cell transplantation or any other experimental brain surgery.
12. Treatment with investigational therapy within 4 weeks prior to screening or 5 drugelimination half-lives of investigational therapy, whichever is longer.
13. Unable or unsafe to perform lumbar puncture on the patient.
14. In the Investigator's judgment, that Parkinson's disease, multiple system atrophy andother dystonia diseases may be combined.
15. Patients who are hypersensitive to any ingredients in the formulation of ER2001.
16. Malignancy within 5 years of screening, except for basal or squamous cell carcinoma ofthe skin or carcinoma in situ of the cervix that has been successfully treated.
17. Concurrent or planned concurrent participation in any interventional clinical study,including explicit pharmacological and non-pharmacological interventions.Observational studies are acceptable.
18. Any serious medical condition or clinically significant laboratory, vital signs, orabnormalities at screening that, in the Investigator's judgment, precludes thepatient's safe participation in and completion of the study.