PIN in Combination With Sintilimab in Previously Treated pMMR/MSS CRC With Hepatic Metastases

Inclusion Criteria:

1. Age 18-75 (inclusive).
2. Eastern Cooperative Oncology Group (ECOG) performance status ≤2 and Estimated life expectancy of more than 3 months.
3. Histologically confirmed diagnosis of unresectable locally advanced, recurrent or metastatic CRC with hepatic metastases have failed at least two lines of prior treatment.
4. Tumor tissues were identified as pMMR by immunohistochemistry (IHC) method or MSS by polymerase chain reaction (PCR).
5. At least one measurable lesion at baseline according to investigators Response Evaluation Criteria in Solid Tumours 1.1 (RECIST 1.1).
6. Patients with injectable lesions (those suitable for direct injection or injection with the assistance of medical imaging) in the liver metastatic lesions, defined as follows: at least one injectable lesion in the skin, mucous membrane, subcutaneous tissue, lymph node or visceral organ with a longest diameter ≥10 mm.
7. Subjects are willing to accept tumor rebiopsy in the process of this study.
8. Adequate organ function as defined by the following criteria:

   * Absolute neutrophil count (ANC) ≥ 1 x 10\^9/L, Platelet count ≥50 x 10\^9/ L, hemoglobin (Hgb) ≥ 80g/L ;
   * Serum creatinine≤1.5 upper limit of normal (ULN) or creatinine clearance (as estimated by Cockcroft Gault) ≥60 mL/min;
   * Serum aspartate amino transferase (AST) and alanine aminotransferase (ALT), ≤5 x ULN ; Total serum bilirubin ≤3 x ULN);
   * Cardiac ejection fraction ≥ 50%, no evidence of pericardial effusion as determined by an echocardiogram (ECHO), and no clinically significant electrocardiogram (ECG) findings;
   * International Normalized Ratio (INR) ≤ 1.5 times the upper limit of normal (ULN), and Activated Partial Thromboplastin Time (APTT) ≤ 1.5 times ULN;
   * Baseline oxygen saturation \>91% on room air.
9. Previous treatments must be completed for more than 4 weeks prior to the enrollment of this study, and subjects have recovered to \<= grade 1 toxicity (except for hematological toxicities and clinically non-significant toxicities such as alopecia).
10. Pregnancy tests for women of childbearing age shall be negative; Both men and women agreed to use effective contraception during treatment and during the subsequent 1 year.
11. Voluntarily participate in this clinical trial and sign an informed consent form.

Exclusion Criteria:

1. Participants with DNA mismatch repair-deficient or microsatellite instability-high (dMMR /MSI-H) CRC.
2. Advanced CRC without hepatic metastases.
3. Subjects are being treated with either corticosteroids (\>10 mg daily prednisone equivalent) or other immunosuppressive medications within 14 days of enrollment.
4. Active central nervous system disease involvement (but allow patients with prior brain metastases treated at least 4 weeks prior to enrollment that are clinically stable and do not require intervention), or prior history of Common Terminology Criteria for Adverse Events (CTCAE) Grade ≥3 drug-related Central Nervous System (CNS) toxicity.
5. Presence or suspicion of fungal, bacterial, viral, or other infection that is uncontrolled or requiring intravenous (IV) antimicrobials for management.
6. Any serious underlying medical (eg, pulmonary, renal, hepatic,gastrointestinal, or neurological) or psychiatric condition or any issue that would limit compliance with study requirements.
7. Major surgery or trauma occurred within 28 days prior to enrollment, or major side effects have not been recovered.
8. Received cytotoxic chemicals, monoclonal antibodies, immunotherapy or other intervene within 4 weeks or 5 half-lives before enrollment.
9. Received radiotherapy within 3 months before enrollment.
10. Patients with primary immunodeficiency or autoimmune diseases requiring immunosuppressive therapy.
11. The presence of uncontrollable serous membrane fluid, such as massive pleural effusion or ascites.
12. Previous or concurrent cancer within 3 years prior to treatment start except for curatively treated cervical cancer in situ, non-melanoma skin cancer, superficial bladder tumors \[Ta (non-invasive tumor), Tis (carcinoma in situ) and T1 (tumor invades lamina propria)\].
13. Known positive test result for human immunodeficiency virus (HIV) or acquired immune deficiency syndrome (AIDS).
14. Prior organ allograft transplantations or allogeneic hematopoietic stem cell transplantation.
15. History of allergy or intolerance to study drug components.
16. Pregnant or breast-feeding. Women of childbearing potential must have a pregnancy test performed within 7 days before the enrollment, and a negative result must be documented.
17. Being participating any other trials or withdraw within 4 weeks.
18. Researchers believe that other reasons are not suitable for clinical trials.