Inclusion Criteria:
* The patient is ≥12 to \<18 years old at the time of informed consent.
* The patient is diagnosed with Gaucher disease based on the following criteria:
1. Glucocerebrosidase (GBA) activity reduced to ≤30% of the lower limit of normal, or
2. GBA activity reduced by \>30% of the lower limit of normal, but confirmed by glucocerebrosidase (GBA) genotype.
* Postmenarchal female patients must have a documented negative pregnancy test prior to enrollment and throughout the study.
* Patients must have been receiving enzyme replacement therapy (ERT) for a minimum of 24 months at a monthly dose equivalent to 30 U/kg to 130 U/kg of enzyme, with treatment ongoing at the time of enrollment. Patients must meet pre-specified treatment goals defined as:
1. Hemoglobin levels: ≥11.0 g/dL for females and ≥12.0 g/dL for males;
2. Platelet count ≥100,000/mm³;
3. Spleen volume \<10.0 multiples of normal (MN);
4. Liver volume \<1.5 MN.
* After explaining and discussing all relevant aspects of the study with the patients and their guardians, patients and their guardians must voluntarily sign the written informed consent form approved by the institutional ethics committee.
* Cytochrome P450 2D6 (CYP2D6) genotype testing shows extensive metabolizers (EMs) or intermediate metabolizers (IMs).
* Patients agree to avoid consuming grapefruit and grapefruit juice.
* Patients agree to discontinue medications listed as contraindicated for concomitant use.
* Participants must be able to cooperate fully as determined by the Principal Investigator to be eligible for the study.
Exclusion Criteria:
* Underwent substrate reduction therapy (SRT) for GD or received miglustat treatment within 12 months prior to enrollment.
* Underwent partial or total splenectomy prior to enrollment or experienced active, clinically significant splenic infarction within the previous 12 months.
* The patient is transfusion-dependent; has a history of esophageal varices or liver infarction; elevated liver enzymes; significant congenital cardiac defect; coronary artery disease; left-sided heart failure; clinically significant arrhythmias; or conduction defects such as Type 2 second-degree or third-degree atrioventricular (AV) block, complete bundle branch block, prolonged QTc interval, or sustained ventricular tachycardia (VT).
* Presence of significant comorbidities, as determined by the Principal Investigator, which may affect study data or confound study results (e.g., malignancies, primary biliary cirrhosis, autoimmune liver disease, pulmonary complications, cardiac structural or functional abnormalities, etc.).
* The patient with any clinically significant disease other than GD.
* Experienced severe bone disease such as new-onset bone crises or fractures within 12 months prior to enrollment.
* The patient has received an investigational product within 30 days prior to enrollment.
* The patient has a known hereditary galactose intolerance, Lapp lactase deficiency, glucose galactose malabsorption, or is a CYP2D6 ultra-rapid metabolizer or indeterminate metabolizer.
* The patient is currently receiving erythropoiesis-stimulating agents (e.g., erythropoietin) or long-term systemic corticosteroid therapy, or received such treatment within 6 months prior to enrollment.
* Positive hepatitis B surface antigen (HBsAg) test results with detectable hepatitis B virus DNA load; positive hepatitis C virus (HCV) antibody with confirmation by HCV RNA polymerase chain reaction (PCR) testing; and positive human immunodeficiency virus (HIV) antibody at screening.
* Presence of non-GD-related hemolytic anemia (such as due to iron, folate, and/or vitamin B12 deficiency or infection/immune-mediated causes) at screening. Patients with folate deficiency, vitamin B12 deficiency-related anemia, or iron deficiency-related anemia at screening are ineligible for study enrollment and will be considered screening failures. Patients may receive treatment for underlying conditions and be re-screened at the discretion of the Principal Investigator.
* The patient and their guardian are unable to comprehend the nature, scope, and potential consequences of the study.
* The Principal Investigator determines that the patient is unsuitable for participation in the clinical trial based on the subject's overall condition.
