Inclusion Criteria:
* \- Aged 18-75 years, male or female;
* Patients with histopathologically confirmed salivary gland malignancy of the head and neck: recurrent/metastatic disease without curative-intent therapeutic options (surgery/radiotherapy), or unresectable locally-advanced disease, with at least one measurable lesion (≥10 mm on spiral CT, complying with RECIST version 1.1);
* HER-2-negative and AR-positive status determined by immunohistochemistry (IHC);
* Availability of evaluable tumor tissue (paraffin-embedded specimen obtained within the past 2 years or fresh tumor tissue);
* ECOG performance status of 0 or 1;
* Expected survival ≥12 weeks;
* Adequate major-organ function within 2 weeks prior to study treatment initiation, meeting the following criteria:
* Bone marrow: haemoglobin ≥100 g/L, white blood cell count ≥4.0 × 10⁹/L or absolute neutrophil count ≥2.0 × 10⁹/L, platelet count ≥100 × 10⁹/L, in the absence of transfusion or colony-stimulating factor support;
* Liver: total serum bilirubin ≤1.5 × upper limit of normal (ULN); aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤1.5 × ULN;
* Kidney: serum creatinine ≤1.5 × ULN OR creatinine clearance ≥60 mL/min; blood urea nitrogen ≤200 mg/L;
* Urine protein: negative; if urine protein is 1+, 24-hour total urinary protein must be \<500 mg;
* Glucose: within normal range; or patients with diabetes with stable glycaemic control under ongoing management;
* Cardiac function: no myocardial infarction within 1 year; no unstable angina; no symptomatic severe arrhythmia; no cardiac insufficiency;
* For women of child-bearing potential: negative serum pregnancy test within 7 days before the first dose of study drug. Men with reproductive potential and women at risk of pregnancy must use highly-effective contraceptive measures throughout the study (e.g., oral contraceptives, intrauterine device, sexual abstinence, or barrier contraception combined with spermicide), and continue contraception for 12 months after treatment completion;
* Subjects voluntarily participate in this study, provide written informed consent, demonstrate good compliance, and are willing to complete follow-up assessments;
* Patients for whom the investigator judges treatment may confer clinical benefit.
Exclusion Criteria:
* \- Patients with prior exposure to anti-androgen therapy or CDK4/6 inhibitors.
* Patients receiving ongoing anti-neoplastic treatment.
* Patients who have participated in, or are participating in, another investigational drug/therapy clinical trial within 4 weeks prior to the first dose of study drug.
* Patients who received haematopoietic stimulating factors, such as granulocyte-colony-stimulating factor (G-CSF) or erythropoietin, within 1 week before the first administration of study drug.
* Positive serology for human immunodeficiency virus (HIV) antibody or \*Treponema pallidum\* antibody.
* Patients with active hepatitis B or hepatitis C:
* HBsAg-positive or HBcAb-positive subjects with detectable HBV DNA (value above the upper limit of normal);
* Subjects with positive HCV antibody and detectable HCV RNA (value above the upper limit of normal).
* Symptomatic and clinically significant pleural effusion or ascites requiring therapeutic intervention.
* Active pulmonary disease (interstitial pneumonia, pneumonitis, obstructive pulmonary disease, asthma) or history of active pulmonary tuberculosis.
* Presence of any uncontrolled clinical conditions, including but not limited to:
* Persistent or active (severe) infection;
* Poorly-controlled diabetes mellitus;
* Cardiac disease (New York Heart Association (NYHA) class III/IV congestive heart failure or cardiac conduction block).
* Occurrence of any of the following events within 6 months prior to first-dose administration: deep-vein thrombosis or pulmonary embolism; myocardial infarction; severe or unstable arrhythmia or angina pectoris; percutaneous coronary intervention, acute coronary syndrome, coronary artery bypass grafting; cerebrovascular accident, transient ischaemic attack, cerebral embolism.
* Prior history of stem-cell transplantation or solid-organ transplantation.
* History of substance abuse of psychotropic agents without successful abstinence, or history of psychiatric disorders.
* Other severe, acute or chronic medical conditions or laboratory abnormalities which, in the investigator's judgement, may increase risks associated with study participation or confound the interpretation of study results.
* Patients deemed by the investigator to have poor compliance, or with other conditions rendering them unsuitable for trial participation.
* Patients with a history of another malignancy within the past five years.
