This clinical trial will utilize a neoantigen nanovaccine constructed from the bacterial membranes of an engineered Lactococcus lactis strain (FOLactis). This platform, independently developed by our center, expresses KRAS antigenic peptides. The vaccine will be administered as adjuvant therapy to post-operative patients with colorectal or pancreatic cancer who carry KRAS mutations and are at high risk of recurrence. The study aims to assess the safety, immunogenicity, and preliminary efficacy of this neoantigen nanovaccine in a clinical setting.

1. Pre-vaccination Screening: Detection of KRAS hotspot mutations in the patient's tumor tissue.

2. Vaccine Composition and Administration: The vaccine utilizes a neoantigen nanovaccine constructed from the bacterial membranes of engineered Lactococcus lactis, independently developed by the Cancer Center of Nanjing Drum Tower Hospital. It is administered via subcutaneous or intralymph node injection.

   The study consists of two phases: Dose Escalation and Dose Expansion. The Dose Escalation phase involves the vaccine alone, while the Dose Expansion phase combines the vaccine with anti-PD-1 antibody and anti-CTLA-4 antibody, as detailed below:

   Dose Escalation Phase: Conducted according to a "3+3" design. The neoantigen nanovaccine is tested at two dose levels: 1.5mg and 3.0mg. Each injection has a total volume of 2.0ml, administered subcutaneously or via ultrasound-guided injection into bilateral inguinal lymph nodes. Vaccination Schedule: A total of 9 vaccinations are planned on Days 1, 4, 8, 15, 22, 43, 64, 85, and 106. Vaccinations #1 and #5-#9: Ultrasound-guided bilateral inguinal lymph node injection combined with subcutaneous injection in the subdeltoid region,accompanied by intravenous cyclophosphamide (200mg/m²) on the same day. Vaccinations #2, #3, and #4: Subcutaneous injection. Efficacy and Safety Monitoring: Radiographic efficacy evaluations are performed every 12 weeks for the first two years post-surgery, and every 24 weeks thereafter. Adverse events are assessed following each vaccination.

   Dose Expansion Phase: The vaccine dose for this phase is determined based on results from the Dose Escalation phase. The vaccination procedure remains the same. Twenty eligible post-operative colorectal cancer patients and twenty eligible post-operative pancreatic cancer patients will be enrolled for continued observation of efficacy and side effects. The nanovaccination schedule follows the Dose Escalation phase protocol. The anti-CTLA-4 antibody is administered on D1 and D43. The anti-PD-1 antibody is administered starting on the first day of vaccination, once every three weeks, until disease progression, unacceptable toxicity, or completion of 6 cycles, whichever occurs first.

3. Immunological Follow-up: Hematological immune monitoring, including lymphocyte immunophenotyping and cytokine profiling, is performed pre-vaccination and on Days 1, 22, 43, 85, and 106 after the first vaccination.

Inclusion Criteria:

• Age ≥18 years and ≤75 years, with an ECOG performance status of 0-1.
• Patients with histologically confirmed colorectal adenocarcinoma or pancreatic adenocarcinoma who have undergone radical resection (R0) and completed at least 4 cycles of postoperative adjuvant chemotherapy.
• Postoperative pathological stage for colorectal cancer is IIIA, IIIB, or IIIC. For pancreatic cancer, postoperative pathological stage is I, II, or III. The tumor must harbor at least one of the following KRAS hotspot mutations: G12D, G12V, G12R, G12A, G12S, G12C, or G13D.
• No radiological evidence of tumor recurrence or metastasis.
• Patients must meet the following hematologic criteria: Lymphocyte count ≥0.5×10⁹/L, neutrophil count ≥1.5×10⁹/L, white blood cell count >2.5×10⁹/L; Hemoglobin ≥90 g/L; Platelet count ≥90×10⁹/L.
• Patients must meet the following biochemical criteria: Total bilirubin ≤1.5 × upper limit of normal (ULN); AST and ALT ≤1.5 × ULN; Serum creatinine ≤1.5 × ULN or creatinine clearance ≥30 mL/min.
• Patients must meet the following coagulation criteria: INR or PTT ≤1.5 × ULN.
• Patients of childbearing potential must employ adequate contraception or other birth control methods before enrollment and throughout the trial.
• Signed informed consent form has been obtained.
• Ability to comply with the study protocol and follow-up procedures.

Exclusion Criteria:

• Patients with colorectal cancer exhibiting microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) or harboring BRAF mutations.
• Pancreatic cancer patients with neuroendocrine tumor components are excluded.
• Patients with a history of other malignancies, except for carcinoma in situ of the cervix, treated squamous cell carcinoma or bladder epithelial tumors (Ta and TIS), or other malignancies that have been curatively treated (at least 5 years prior to enrollment).
• Prior treatment with anticancer vaccines or any antibodies targeting T-cell co-regulatory proteins (e.g., anti-PD1, anti-PDL1, or anti-CTLA4).
• Patients with HIV, HCV, or HBV infection; uncontrolled coronary artery disease or asthma; uncontrolled cerebrovascular disease; or any other condition deemed by the investigator as grounds for exclusion.
• Patients who are on immunosuppressants or systemic corticosteroid therapy for immunosuppressive purposes (at a dose >10 mg/day prednisone or equivalent) and have continued use within 2 weeks prior to enrollment.
• Poorly controlled cardiac clinical symptoms or diseases, such as: Heart failure of NYHA Class II or higher; Unstable angina; Myocardial infarction within the past year; Clinically significant supraventricular or ventricular arrhythmia requiring treatment or intervention; QTc >450 ms (males); QTc >470 ms (females).
• Abnormal coagulation function (INR >2.0, PT >16 s), bleeding tendency, or current thrombolytic or anticoagulant therapy. Prophylactic use of low-dose aspirin or low molecular weight heparin is allowed.
• Patients with active infection; unexplained fever ≥38.5°C within 7 days prior to medication; baseline white blood cell count >15×10⁹/L; or suppurative and chronic infections with non-healing wounds.
• Pregnant or lactating women. Women of childbearing potential must have a negative pregnancy test within 7 days prior to enrollment.
• Substance abuse, or clinical, psychological, or social factors that may affect the provision of informed consent or the conduct of the study.
• Known or suspected allergy to drugs used in immunotherapy.
• Inability to undergo immunological and clinical follow-up assessments.
• Known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation.
• Participation in other interventional drug clinical trials concurrently.