This study is a Phase I/II Clinical Study to Evaluate the Safety, Tolerability, Pharmacokinetics and Initial Efficacy of JS212 in Subjects with Advanced Malignant Solid Tumour. Patients will be enrolled in two stages: a dose-escalation stage and a dose expansion stage.

Inclusion Criteria:

1. Subjects of either sex who are 18 to 75 years of age (inclusive of 18 and 75 years) at the time of signing the consent form;
2. Histologically or cytologically confirmed advanced malignant solid tumors;
3. Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1;
4. Expected survival of ≥ 12 weeks;
5. Subjects have at least 1 measurable lesion according to RECIST v1.1 criteria (without measurable lesions are allowed during dose escalation phase);

Exclusion Criteria:

1. Presence of active central nervous system metastasis. If previous radiotherapy or surgery, etc. has been received, and the imaging examination within 4 weeks before the first dose suggests that the brain metastasis is stable without exacerbation or new neurological symptoms, and hormone therapy has been discontinued two weeks before the first dose, screening is allowed; for the presence of meningeal metastasis and brainstem metastasis, regardless of the treatment or not, screening is not allowed;
2. Presence of clinically symptomatic pleural effusion, ascites, or pericardial effusion that requires repeated management (puncture or drainage, etc.);
3. Presence of medically uncontrolled hypertension, or with a history of hypertensive crisis or hypertensive encephalopathy;
4. Presence of a history of (non-infectious) interstitial lung disease (ILD)/non-infectious pneumonia requiring steroid therapy (e.g., idiopathic pulmonary fibrosis, mechanized pneumonia, drug-induced pneumonia, radiation pneumonitis, idiopathic pneumonia, etc.), and current ILD/non-infectious pneumonia;
5. Presence of clinically significant lung-specific co-morbidities including, but not limited to, any underlying lung disease (e.g., pulmonary embolism, severe asthma, severe COPD, restrictive lung disease, etc., diagnosed within 3 months prior to the first study dose) and any autoimmune, connective tissue, or inflammatory disease with pulmonary involvement (e.g., rheumatoid arthritis, Scheugelin's syndrome, sarcoidosis, etc.) and prior total pneumonectomy;
6. Presence of a history of immunodeficiency, including a positive test for Human Immunodeficiency Virus (HIV), or a known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation；
7. the presence of other factors that may cause them to be forced to terminate the study midway, such as serious physical or mental illness or abnormal laboratory tests, which may increase the risk of participation in the study, affect treatment compliance, or interfere with the results of the study, and which, in the judgment of the investigator, make the subject unsuitable for participation in this study；