Cadonilimab as Neoadjuvant Therapy in Resectable Stage II-III MSI-H/dMMR Colorectal Cancer

Inclusion Criteria:

1. Willing and able to provide written informed consent.
2. Male or female subjects \> 18 years
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
4. Histological or cytological documentation of adenocarcinoma of the colon or rectum; Tumor tissues were identified as mismatch repair-deficient (dMMR) by immunohistochemistry (IHC) method or microsatellite instability-high (MSI-H) by polymerase chain reaction (PCR) in local site; For colon cancer must be determined by CT or MRI scans as locally advanced (T4) or cN1-2 \[with the definition of a clinically positive lymph node being any node ≥ 1.0 cm\]). Participants should be eligible for radical resection of R0.
5. At least one measurable lesion as defined by RECIST 1.1
6. Willing and able to provide 2ml blood and archived tumor tissue sample for MSI status testing. Patients who do not have adequate archival tumor tissue available should undergo a fresh tumor biopsy
7. Adequate bone marrow, hepatic and renal function as assessed by the following laboratory requirements conducted within 7 days of starting study treatment.
8. Willingness of men and women of reproductive potential to observe conventional and effective birth control for the duration of treatment and for 120 days following the last dose of study treatment; this may include barrier methods such as condom or diaphragm with spermicidal gel.

Exclusion Criteria:

1. Previous any systemic anticancer therapy for colorectal cancer disease, including chemotherapy, radiothapy or immunotherapy
2. Previously received anti-programmed death-1 (PD-1) or its ligand (PD-L1) antibody, anti-cytotoxic T lymphocyte-associated antigen 4 (cytotoxic T-lymphocyte-associated Protein 4, CTLA-4) antibody or other drug/antibody that acts on T cell costimulation or checkpoint pathways.
3. Subjects with known allergy to monoclonal antibodies
4. Previous or concurrent cancer that is distinct in primary site or histology from colon cancer within 2 years prior to study drug treatment.
5. Concurrent with active autoimmune disease or Participants with a history of autoimmune disease who may recur
6. Subjects receiving immunosuppressive agents (such as steroids, or corticosteroids at physiologic replacement doses, equivalent to ≤ 10 mg prednisone daily ) for any reason within 14 days before the study drug treatment.
7. Uncontrolled hypertension or hyperglycemia within 14 days before the study drug treatment.
8. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring frequent drainage (recurrent within 14 days of study drug treatment)
9. History of interstitial lung disease, noninfectious pneumonia, or poorly controlled lung disease (including pulmonary fibrosis, acute lung disease).
10. Active systemic bacterial, viral, or fungal infection， requiring systemic treatment within 14 days before study drug treatment.
11. Positive test for hepatitis B virus surface antigen with HBV DNA\> 500 IU/mL（\> 2500copies/mL）at screening or untreated Chronic hepatitis B
12. Positive test for hepatitis C virus ribonucleic acid (if antihepatitis C virus antibody tested positive) at screening;
13. Known history of testing positive for human immunodeficiency virus (HIV)
14. Major surgery for any reason, except diagnostic biopsy, within 28 days of the first administration of study drug. The subject must fully recovered from prior treatment before the first administration of study drug
15. Previous allogeneic stem cell transplantation or organ transplantation
16. Previous history of myocarditis, cardiomyopathy, and malignant arrhythmias
17. Vaccination within 4 weeks of the first administration of study drug and throughout the study is prohibited, except for administration of inactivated vaccines (eg, inactivated influenza vaccines).
18. All other underlying medical condition (including laboratory abnormalities) that is detrimental to study drug administration, or may affect drug toxicity or AE interpretation, or may result in inadequate or reduced adherence to study drug; Alcohol or drug abuse or dependence
19. Pregnancy or lactation
20. Concurrent participated in another therapeutic clinical trial