Coxsackievirus A21 combined with pembrolizumab partially increased the number of PD-L1+ tumour cells and exhibited well tolerance in a clinical trial.324 This indicates that the combination of OVs and ICIs may enhance antitumour efficacy while limiting toxicity, compared with that of monotherapy.325 Thus far, four OVs have been approved for cancer treatment worldwide, among which Talimogene laherparepvec (T-VEC) for melanoma is the first widely approved and recognised OV.326. This evidence concerns the gene CD274 and melanoma.