Pioneering studies have recently been conducted to develop a 68Ga-labeled linear peptide GZP–based granzyme B–targeting radiotracer, 68Ga-1,4,7–triazacyclononane-1,4,7-triacetic acid–GZP (68Ga-NOTA-GZP), for PET monitoring of tumor immunotherapy in mouse models (25–27). Here, GZMB is linked to neoplasm.