In the current study, we have evaluated whether the granzyme B targeting peptide biomarker, [18F]AlF-mNOTA-GZP, is able to stratify responders to ICI therapy in the HEPA 1-6 syngeneic model of HCC, using flow cytometry to correlate tumour biomarker retention with tumour-associated immune cells. This evidence concerns the gene GZMB and hepatocellular carcinoma.