This include two parts, Stage 1 is a dose climbing study and Stage 2 is a dose extending study.

This study is a study of MAX-40279 in patients with advanced / metastatic solid tumors. This study include two Parts, the Part 1 will assess the safety and efficacy of the dose climbing level of MAX-40279, and recommend a dose extending level of MAX-40279 for stage 2.

Inclusion Criteria:

1. Signed informed consent form.
2. Males and/or females over age 18 and 75.
3. Histologically or cytologically documented local advanced / metastatic solid tumors who have failed standard treatment or cannot obtain standard treatment in the dose escalation stage; dose expansion stage group A: relapsed and refractory advanced gastric cancer; dose expansion stage group B: relapsed and refractory extensive stage small cell lung cancer; dose expansion stage group C: other relapsed and refractory solid tumors except group A
4. At least one measurable lesion according to the Response Evaluation Criteria in Solid Tumors (RECIST 1.1).
5. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
6. Expected survival of more than 3 months.

Exclusion Criteria:

1. The adverse reactions of previous anti-tumor treatment have not recovered to CTCAE 5.0 grade evaluation ≤ 1 (except alopecia and other adverse reactions without safety risks judged by the investigator)
2. Subject is known to have previous serious allergic reactions to macromolecular protein preparations/monoclonal antibodies, or known to any component of the test drug
3. Active systemic infectious diseases requiring intravenous antibiotic treatment 2 months before the first medication
4. Subject has poorly controlled cardiovascular and cerebrovascular clinical symptoms or diseases, including but not limited to: such as: (1) NYHA class II or higher heart failure or LVEF < 50%; (2) unstable angina pectoris; (3) myocardial infarction and cerebral infarction within 6 months; (4) clinically significant supraventricular or ventricular arrhythmias are still poorly controlled without clinical intervention or clinical intervention
5. brain metastases, spinal cord compression, carcinomatous meningitis with clinical symptoms, or other evidence of uncontrolled brain and spinal cord metastases, Patients who are not suitable by the investigator's judgment
6. Patients who have experienced ≥ grade 3 immune-related adverse events in immunotherapy (except grade 3 hypothyroidism that can be controlled by drugs)
7. Patients who have other malignant tumors within 5 years before enrollment,Exceptions: a. radical cervical carcinoma in situ or non-melanoma skin cancer; b. radical second primary cancer without recurrence within five years; c. the investigator believes that the double primary cancer can benefit from this study; d. the investigator has clearly excluded which primary tumor source the metastasis