• Written informed consent.

• Male or female, ≥18 years of age.

• Patients with any 1 of the following histologically confirmed tumors and who qualifies for new or continued CPI therapy and relapsing to/after standard therapy or the patient has refused or does not tolerate standard therapy:

‣ Inoperable/metastatic cutaneous malignant melanoma

⁃ Relapsed or newly diagnosed locally advanced inoperable/metastatic TNBC

⁃ Inoperable advanced/metastatic non-squamous NSCLC

⁃ Inoperable and/or advanced Synovial or myxoid round cell sarcoma

⁃ Inoperable and/or advanced osteosarcoma

⁃ Inoperable and/or advanced colorectal cancer, patients assessed as positive for NY-ESO-1 or MAGE-A3 expression at baseline

⁃ Inoperable and/or advanced/metastatic sarcoma, patients assessed as positive for NY-ESO-1 or MAGE-A3 expression at baseline

• Measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1.

• Tumor lesion which is deemed feasible for biopsy and injection

• ECOG/WHO performance status 0 to 1.

• Acceptable liver and renal function, defined as:

‣ Total bilirubin ≤1.5 x upper limit of normal (ULN; does not include patients with Gilbert's Disease), and

⁃ Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤3.0 x ULN, and

⁃ Serum creatinine ≤1.5 x ULN

• Acceptable hematological function, defined as:

‣ Hemoglobin ≥9 g/dL, and

⁃ Neutrophils ≥1.5 x 109/L, and

⁃ Platelet count ≥100 x 109/L Patients may be transfused to meet the hemoglobin entry criteria.

• Acceptable coagulation status defined by international normalized ratio (INR) of blood clotting, prothrombin time and activated partial thromboplastin time within ≤1.5 x upper limit of normal.

⁃ Negative pregnancy test at screening in all women of childbearing potential (WOCBP). Such patients must agree to use a highly effective method of contraception (Appendix 1) during study intervention and for 3 months after the last virus treatment, 4 months after the last dose of pembrolizumab, and 12 months after CPO dosing. Male patients and male partners of female patients must also use barrier contraception, i.e., condom, for the time periods specified for WOCBP, plus a further 3 month period.

⁃ Urine pregnancy tests should have a sensitivity of at least 25 mIU/mL for human chorionic gonadotropin (hCG). If the urine test is positive, it must be followed by a quantitative analysis of hCG concentration in blood.

⁃ Prior therapy with an immune CPI is allowed provided a 6-week washout period is observed for patients with prior programmed cell death (PD)1 or PDL1 treatment