This is a Phase II, open-label, non-randomized, multicenter study to evaluate the clinical efficacy and safety of HG146 in participants with recurrent or metastatic adenoid cystic carcinoma. This study is divided into two stages. 40 participants will be enrolled in the first stage. The efficacy and safty data will apply to make go or no go decision. Then the second stage will continue to enroll 100 Particapants.

Inclusion Criteria:

• Signed informed consent form (ICF) and able to comply with study.
• Age ≥18 years, gender unlimited.
• Recurrent or metastatic adenoid cystic carcinoma with evidence of disease progression (imaging progression or clinical evidence of progression) within one year of histological or cytological diagnosis.
• Estimated survival >12 weeks, as determined by the investigator.
• The United States Eastern Cancer Consortium (ECOG) physical status score 0-1.
• Has adequate organ function.
• At least 1 measurable tumor lesion according to RECISTv1.1 criteria.

Exclusion Criteria:

• Symptomatic central nervous system (CNS) metastases that have required steroids within 4 weeks prior to first dose of study treatment.
• Received prior therapies targeting HDAC.
• Chemotherapy was received within 21 days before the first administration of the study treatment, and anti-tumor therapy such as radiotherapy, biotherapy, targeted therapy, and immunotherapy was received within 28 days before the first administration of the study treatment [small molecule targeted drugs, Chinese medicines with anti-tumor indications, and local palliative radiotherapy were 14 times before the first administration of the study drug.
• Used strong CYP3A4 inhibitors or inducers within 7 days before the first use of the investigational drug.
• Major surgery or major injury <=28 days before the first dose of study treatment,or anticipated major surgery during the study.
• Prior allogeneic bone marrow transplantation or other solid organ transplantation
• Active infection requiring systemic treatment.
• Current or past presence of other malignancies (other than adequately treated basal cell or squamous cell carcinoma of the skin and carcinoma in situ of the cervix), unless radical treatment has been performed and there is no evidence of recurrence and metastasis in the last 5 years.
• A person is known to be allergic to any active ingredient or excipient of the investigational drug.
• Pregnant or lactating women.
• patients with drug abuse or chronic alcohol abuse that may affect the evaluation of the test results.](streamdown:incomplete-link)