Inclusion Criteria:
* Sex: male/female;
* Age:6-18 years at the time of randomization;
* Clinical diagnosis in accordance with the DSM-5 diagnosis of ASD;
* Diagnosis of ASD using the K-SADS-PL-C DSM-5 and CARS;
* A severity score of ≥ 4 on the CGI scale;
* Subjects must be able to participate and deemed suitable for participation in the study, at the investigator's discretion, and be able to follow the study evaluation schedule;
* The parent or guardian agrees to accompany the subject to all clinical visits and to provide information about the subject's behavior and symptoms, and must agree to supervise the subject's compliance with protocol-specified procedures and the use of study drug doses;
* The parent or guardian is willing and able to give written informed consent in accordance with local requirements. When the subject is capable of making the decision to consent to participation in the study, the subject is likewise willing and able to provide written informed consent in accordance with local requirements.
Exclusion Criteria:
1. Neurologic/Psychiatric Disorders
* Concurrent comorbidity with any other mental disorder (other than ADHD) as diagnosed by the K-SADS-PL-C DSM-5;
* Neurologic disorders or prior head trauma resulting in coma;
* Unstable or uncontrollable clinically significant psychiatric and/or neurological disorders that may interfere with safety or efficacy outcome;
* Unstable or uncontrolled irritability in the judgment of the investigator;
* Any suicide attempts in the opinion of the investigator at the time of screening that he/she is at risk for suicidal behavior or in his/her medical history;
* A history of seizures within the past 6 months;
* A history of alcohol or other substance abuse/dependence.
2. Cardiovascular Disease
* Current cardiovascular disease not effectively controlled in the opinion of the investigator;
* Clinically significant abnormalities (e.g., twice consecutive measurements) as confirmed by ECG at screening, including, but not limited to: QTc: ≥450 milliseconds, absence of predominant sinus rhythm, and second or third degree a-v block.
3. Diseases of other organ systems
* Accompanying other diseases or conditions (pulmonary, gastrointestinal, hepatic, renal, metabolic, immune system, or obesity) that may interfere or whose treatment may interfere with the conduct of the study; or where, in the opinion of the Investigator, discontinuation of the Prohibited Substance may pose an unacceptable risk to the subject.
* Evidence of gastrointestinal bleeding, e.g., active gastric ulcer;
* History of coagulopathy, bleeding disorders or blood disorders;
4. Other exclusion criteria
* Marked respiratory depression;
* Acute or severe bronchial asthma;
* Known or suspected paralytic bowel obstruction;
* Allergic to buprenorphine;
* Participation in a drug study within 30 days prior to randomization or within 5 times the half-life of the molecule to be studied, whichever is longer; or drug study; or participation in a study testing a medical device within 30 days prior to randomization, or the device is still in action. active;
* History of blood loss greater than 250 mL within 3 months prior to screening;
* Medications permitted since 4 weeks prior to screening that have NOT been clearified and stable, and medications permitted for the treatment of epilepsy since 3 months prior to screening that have NOT been clearified and stable.
* Usage of a prohibited medication within 2 weeks prior to the screening visit (and ensuring at least 4 weeks of washout time prior to the baseline assessment) or usage of a prohibited medication within 5 times of half-life prior to the randomization (whichever is longer).
