A Study of HG381 Administered to Patients With Advanced Solid Tumors

Inclusion Criteria: * Capable of giving signed informed consent. * Life expectancy of at least 3 months. * Histological or cytological documentation of an advanced solid tumor，subjects with advanced/recurrent solid tumors, who have progressed on, be intolerant of, or ineligible for, all available therapies for which clinical benefit has been established. * Measurable disease per RECIST version 1.1, there is at least one measurable lesion during the screening period. * Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1. * Adequate organ function : Hematologic system: Hemoglobin ≥9 g/dL, Absolute neutrophil count \[ANC\] ≥1.5x10\^9/L, Platelets ≥100x10\^9/L, INR ≤ 1.5 and APTT ≤1.5 x ULN; Hepatic system: Total bilirubin ≤1.5 x ULN, ALT and AST ≤ 2.5 x ULN; Renal system: serum creatinine ≤1.5×ULN or creatinine clearance ≥50 mL/min (calculated by the Cockcroft-Gault formula); Cardiac system: left ventricular ejection fraction (LVEF) ≥50% ; QT interval (QTcF) ≤470 ms for women, and ≤450 ms for men; Endocrine system: Thyroid-stimulating hormone (TSH) is within the normal limits. * Subjects with fertility must agree to take medically approved effective contraceptive measures during the entire trial period and at least 3 months after the last medication. Exclusion Criteria: * Chemotherapy, radiotherapy, biological therapy, endocrine therapy, immunotherapy and other anticancer therapy within 4 weeks. * Concurrent medical condition requiring the use of other systemic immunosuppressive treatment within 4 weeks before the first dose of study treatment. * Receipt of any live vaccine within 4 weeks of the start of study treatment. * Receipt of unmarketed clinical trial drugs or treatments within 4 weeks of the start of study treatment. * Receipt of surgery or interventional treatment (excluding tumor biopsy, puncture, etc.) within 4 weeks of the start of study treatment. * History or evidence of cardiovascular and cerebrovascular diseases risk. * Subjects with uncontrolled diabetes. * Symptomatic central nervous system (CNS) metastases or asymptomatic CNS metastases that have required steroids within 2 weeks prior to first dose of study treatment. * Currently or in the past suffering from malignant tumors. * Uncontrollable pleural effusion, pericardial effusion or ascites still need to be drained frequently after appropriate intervention. * Active or suspected autoimmune disease. * History of idiopathic pulmonary fibrosis, interstitial lung disease, or organizing pneumonia, or evidence of active, non-infectious pneumonitis. * Toxicity from previous treatment including: Toxicity Grade ≥3 related to prior immunotherapy and that led to study treatment discontinuation; Toxicity related to prior treatment that has not resolved to Grade ≤ 1. * Subjects who have acute bacterial, viral or fungal infections and require systemic anti-infective treatment. * Positive test for syphilis antibodies or human immunodeficiency virus (HIV) antibodies. * Subjects who are allergic to test drugs and excipients. * Women who are pregnant or breastfeeding. * Known drug or alcohol abuse. * Patients with mental or neurological diseases. * Prior allogeneic or autologous bone marrow transplantation or other solid organ transplantation. * Subjects who have a history of serious systemic disease or any other reason are not suitable to participate in this trial as judged by the investigator.