Preclinical comparative study of [(18)F]AlF-PSMA-11 and [(18)F]PSMA-1007 in varying PSMA expressing tumors

A wide variety of (18)F-labeled PSMA-targeting PET radiotracers have been developed, including [(18)F]AlF-PSMA-11. As there is only limited data on the comparison with other (18)F-labeled PSMA PET tracers, a comparative preclinical study between [(18)F]AlF-PSMA-11 and [(18)F]PSMA-1007 was conducted. Mice with varying PSMA expressing tumors (C4-2, 22Rv1 and PC-3, each n = 5) underwent two PET/CT scans with both [(18)F]AlF-PSMA-11 and [(18)F]PSMA-1007. Ten additional mice bearing C4-2 xenografts were subjected to ex vivo biodistribution with either [(18)F]AlF-PSMA-11 (n = 5) or [(18)F]PSMA-1007 (n = 5). Absolute SUV(mean) and SUV(max) values were significantly higher for [(18)F]PSMA-1007 scans in both C4-2 tumors (p < 0.01) and 22Rv1 tumors (p < 0.01). In C4-2 xenograft bearing mice, the tumor-to-organ ratios did not significantly differ between [(18)F]AlF-PSMA-11 and [(18)F]PSMA-1007 for liver, muscle, blood and salivary glands (p > 0.05). However, in 22Rv1 xenograft bearing mice, all tumor-to-organ ratios were higher for [(18)F]AlF-PSMA-11 (p < 0.01). In healthy organs, [(18)F]PSMA-1007 uptake was higher in the liver, gallbladder, small intestines and glands. Biodistribution data confirmed the increased uptake in the heart, small intestines and liver with [(18)F]PSMA-1007. Absolute tumor uptake was higher with [(18)F]PSMA-1007 in all tumors. Tumor-to-organ ratios did not differ significantly in high PSMA expressing tumors, but were higher for [(18)F]AlF-PSMA-11 in low PSMA expressing tumors. Furthermore, [(18)F]PSMA-1007 showed higher uptake in healthy organs.