This study aims to evaluate the safety, tolerability, PK characteristics, immunogenicity, and preliminary anti-tumor efficacy of SCTB39-1 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, over 18 years old;
3. Survival duration more than 3 months;
4. ECOG score ≤ 1 point;
5. Participants in Phase Ia (dose-escalation phase) are required to meet the following criteria: histologically or cytologically confirmed diagnosis of advanced malignant solid tumour;
6. Participants in Phase Ib (dose-expansion phase) and Phase II are required to meet the following criteria: Histologically or cytologically confirmed specific type advanced malignant solid tumours;
7. At least one measurable tumor lession according to RECIST v1.1;
8. 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 5 years prior to the enrollment;
3. Participants with brainstem, meningeal, spinal metastases, or compression; active central nervous system metastases;
4. Significant bleeding risk;
5. Presence of pleural effusion, peritoneal effusion, or ascites;
6. History of permanent discontinuation of immunotherapy due to immune-related toxicity or occurrence of ≥ Grade 3 irAEs;
7. Presence of any active autoimmune disease or a history of autoimmune disease with an expected recurrence;
8. History of severe allergies, severe drug allergies (including unapproved investigational drugs);
9. History of organ transplantation or stem cell transplantation;
10. Need for immunosuppressive drugs within 2 weeks prior to enrollment or anticipated during the study;
11. Received chemotherapy, immunotherapy, biologic therapy, or other anti-tumor treatments within 4 weeks before enrollment;
12. Pregnant or breastfeeding female.