An oncolytic virus for use in a method of treating or preventing cutaneous squamous cell carcinoma (CSCC), renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC), triple negative breast cancer (TNBC), small cell lung cancer (SCLC), advanced recurrent head and neck cancer, squamous cell carcinoma of the head and neck (SCCHN), nasopharyngeal carcinoma (NPC), hepatocellular carcinoma (HCC), anal cancer, colorectal cancer (CRC), basal cell carcinoma (BCC), Merkel cell carcinoma, appendiceal carcinoma, sarcoma of the skin, recurrent melanoma after surgery, advanced or metastatic urothelial carcinoma, liver metastases, microsatellite instability high cancer (MSI-H), mixed advanced solid tumors, virally caused cancer, locoregionally advanced cancer, pediatric cancer, cancer in patients with no or minimal pre-existing anti-cancer immunity, cancer as first line therapy, cancer in previously treated patients, cancer in patients who have not received checkpoint blockade therapy, and/or cancer in patients who have received checkpoint blockade therapy, wherein the oncolytic virus: is, or is derived from, a clinical isolate which has been selected by comparing the abilities of a panel of three or more clinical isolates of the same viral species to kill tumor cells of two or more tumor cell lines in vitro and selecting a clinical isolate which is capable of killing cells of two or more tumor cell lines more rapidly and/or at a lower dose in vitro than one or more of the other clinical isolates in the panel； comprises (i) a fusogenic protein-encoding gene； and (ii) an immune stimulatory molecule or an immune stimulatory molecule-encoding gene； comprises (i) a GM-CSF-encoding gene； and (ii) an immune co-stimulatory pathway activating molecule or an immune co-stimulatory pathway activating molecule-encoding gene； and/or comprises a gene encoding a CTLA-4 inhibitor.La présente invention concerne un virus oncolytique pour son utilisation dans le traitement ou la prévention d'un
