Inclusion Criteria:  Able and willing to provide written informed consent and willing to comply with the study's requirements. Male or female age >18 years at screening. Metastatic or locally advanced solid tumor that has progressed on, is refractory to, or for which there is no efficacious standard of care therapy.  Demonstrate adequate organ function as defined below. All screening laboratory assessments should be performed within 14 days of treatment initiation and include the following:  Absolute neutrophil count (ANC) ≥1.5 × 109/L； Platelets ≥100 × 109/L；Hemoglobin ≥9 g/dL or ≥5.6 mmol/L Measured or calculated creatinine clearance (CrCl) ≥ 60 mL/min Total bilirubin ≤1.5 × ULN OR direct bilirubin ≤ULN for subjects with total bilirubin levels > 1.5× ULN； Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN OR ≤5 × ULN for subjects with liver metastases. Performance status of 0 or 1 on the ECOG Performance Scale. Life expectancy >12 weeks at Baseline. Women of childbearing potential must have negative serum pregnancy test within 3 days prior to receiving the first study drug administration. For women of childbearing potential, must be willing to use an adequate method of contraception from 30 days prior to the first study drug administration and 120 days following last day of study drug administration. Male subjects of childbearing potential must be surgically sterile or must agree to use adequate method of contraception during the study and at least 120 days following the last day of study drug administration.  Exclusion Criteria:  Received prior TLR7/8 agonists (excluding topical agents). Has untreated or uncontrolled central nervous system (CNS) involvement. Will receive concurrent chemotherapy, immunotherapy, biologic, hormonal therapy, or other therapies for cancer. Received systemic interferon alfa (IFNα) prior to enrollment. Unresolved toxicities from prior therapy, defined as having not resolved to CTCAE v5.0 Grade 0 or 1, with exception of endocrinopathies from prior therapy, alopecia, and vitiligo. Treatment with systemic corticosteroids. Concomitant or planned use of sensitive substrates of major cytochrome P450 enzymes. Has an active infection requiring systemic therapy. Has known active infection with the human immunodeficiency virus, Unstable/inadequate cardiac function. Uncontrolled concurrent illness. A history of interstitial lung disease. A history of coagulopathy resulting in uncontrolled bleeding or other bleeding disorders. Participated in a clinical study of an investigational agent within 30 days of screening. Has known psychiatric, substance abuse, or other disorders that would interfere with cooperation with the requirements of the study in the opinion of the investigator. Is pregnant or breastfeeding.