The purpose of this study is to allow RC88 treatment of patients with advanced solid tumours to assess the safety and tolerability of clinical pharmacology studies

The main purpose of this Phase I study is to test RC88 at different dose levels to see if it is safe and well tolerated when given once every 2 weeks.

Inclusion Criteria:

1. All subjects must be ≥ 18 years at the first screening examination / visit.
2. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 1.
3. Life expectancy of at least 12 weeks
4. Phase I must be histologically or cytologically confirmed and have failed standard therapy (disease progression after treatment) or are intolerant,unable to receive, or nonexistent to standard care,Patients with partial,advanced or metastatic malignant solid tumors;
5. Phase II-Advanced malignant solid tumor with MSLN expression
6. Patients with malignant pleural mesothelioma were assessed using mRECIST criteria, and those with other cancers were assessed using RECIST V1.1 criteria
7. Phase II-Mesothelin (MSLN) positive as confirmed by the central laboratory.
8. Adequate organ function
9. Voluntarily sign an informed consent form

Exclusion Criteria:

1. Cancer metastases in the brain
2. Active infection or past hepatitis B or C infection
3. Major surgery less than 1 month before the start of the study
4. Uncontrolled heart disease
5. History of allergy to mesothelin-directed antibodies, tubulysin, monoclonal antibodies related compounds