Although discussion continues as to whether measuring PD-L1 expression in cancers is a clinically useful predictive biomarker for response to PD-1/PD-L1 inhibitors33, other PD-L1-positive cancers in dogs including osteosarcoma, hemangiosarcoma, mast cell tumour, mammary adenocarcinoma, lymphoma and prostate adenocarcinoma13, 15, 29, 31, could also be targeted by c4G12. This evidence concerns the gene PDCD1 and osteosarcoma.