Clinical Study of mRNA Vaccine in Patients With Advanced Malignant Solid Tumors

Inclusion Criteria: * Are ≥18 years old, without limitation of sex at time of consent. * Patients with malignant solid tumors confirmed by histopathology or cytology and having at least one measurable lesion. * Fresh biopsy specimens can be provided for vaccine preparation. * Patients with malignant solid tumors who develop secondary drug resistance after receiving PD-1/PD-L1 drug therapy, including but not limited to gastric cancer, esophageal cancer, and other gastrointestinal tumors of MSI-H Exclusion Criteria: * It is known that it is allergic to any tumor vaccine and Sintilimab preparations; Or have experienced severe allergic reactions to other monoclonal antibodies in the past; * The predicted number of new antigens is less than 10; * Those who are pregnant or breastfeeding; * Those with an expected survival period of less than 3 months;