The purpose of the study is to evaluate the efficacy and safety of rezvilutamide in combination with androgen deprivation therapy (ADT) in participants with androgen receptor (AR) positive, high-risk salivary duct carcinoma (SDC).

The procedures include screening, treatment and follow-up period. The treatment includes rezvilutamide plus Luteinizing Hormone Releasing Hormone agonist (LHRHa) for up to 2 years.

Inclusion Criteria:

• Provision of signed and dated informed consent form
• Stated willingness to comply with all study procedures and availability for the duration of the study
• Histologically confirmed salivary duct carcinoma and stage III or IVa or IVb according to AJCC Cancer Staging Manual Eighth Edition
• Completed SDC surgery, and adjuvant radiotherapy is planned or ongoing or has completed
• Androgen receptor (AR) positive
• White blood cell (WBC) ≥ 3.0 x 10^9/L, Neutrophil count≥ 1.5 x 10^9/L, Platelet count (PLT) ≥ 75 x 10^9/L, Haemoglobin (Hb) ≥ 90 g/L
• Serum creatinine (Cr) < 1.5 x upper limit of normal(ULN) or creatinine clearance ≥ 50 ml/min.
• Total bilirubin (TBIL) < 1.5 x ULN, AST< 2.5 x ULN, and ALT< 2.5 x ULN
• Eastern Cooperative Oncology Group (ECOG) performance status 0, 1 or 2, and ability to take oral medication
• For females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation and for an additional 1 year after the end of study intervention administration
• For males of reproductive potential: use of condoms or other methods to ensure effective contraception with partner

Exclusion Criteria:

• Received prior anti-AR pathway therapy
• Treatment with another investigational drug or chemotherapy within 6 months
• History of hypothalamus or pituitary dysfunction
• History of seizure
• Clinically uncontrolled diseases, such as septic shock, uncontrolled hypertension, unstable angina, New York Heart Association (NYHA) class III or IV heart disease, clinically unstable arrhythmia, myocardial infarction (in the past 6 months)
• Previous cancer except skin cancer rather than malignant melanoma or any cancer curatively treated > 5 years prior to study entry
• Pregnancy or lactation