This study aims to evaluate the safety, tolerability, PK characteristics, immunogenicity, and preliminary anti-tumor efficacy of SCTB39G as a monotherapy in adult patients with advanced malignant solid tumours. This study is an open label, multicentre, dose-escalation and dose-expansion Phase I/II clinical trial.

Inclusion Criteria:

• 1.Voluntarily sign the informed consent form (ICF);
• 2.Male or female, ≥ 18 years and ≤ 70 years old;
• 3.Survival duration more than 3 months;
• 4.ECOG score ≤ 1 point;
• 5.histologically or cytologically confirmed diagnosis of advanced malignant solid tumour；
• 6.At least one measurable tumor lession according to RECIST v1.1;
• 7.Adequate organ and bone marrow function.

Exclusion Criteria:

• 1.Has participated in another clinical study within 4 weeks prior to the first dose;
• 2.Other malignancies diagnosed within 1 years prior to the enrollment;
• 3. Participants with brainstem, meningeal, spinal metastases, or compression; active central nervous system metastases;
• 4.NSCLC at high risk of bleeding; Obvious invasion of tumor into adjacent organs of esophageal lesions leads to high risk of bleeding or fistula,or participants after endotracheal stent implantation;
• 5.Participants with portal hypertension due to portal vein tumor thrombus at risk of bleeding;
• 6.Presence of pleural effusion, peritoneal effusion, or ascites;
• 7.Received chemotherapy, immunotherapy, biologic therapy, or other antitumor treatments within 4 weeks before enrollment
• 8.History of permanent discontinuation of immunotherapy due to immune-related toxicity or occurrence of ≥ Grade 3 irAEs;
• 9.Presence of any active autoimmune disease or a history of autoimmune disease with an expected recurrence;
• 10.History of severe allergies, severe drug allergies (including unapproved investigational drugs);
• 11.History of organ transplantation or stem cell transplantation;
• 12.Need for immunosuppressive drugs within 2 weeks prior to enrollment or anticipated during the study;
• 13.Pregnant or breastfeeding female.