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

A wide variety of ¹⁸F-labeled PSMA-targeting PET radiotracers have been developed, including [¹⁸F]AlF-PSMA-11. As there is only limited data on the comparison with other ¹⁸F-labeled PSMA PET tracers, a comparative preclinical study between [¹⁸F]AlF-PSMA-11 and [¹⁸F]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 [¹⁸F]AlF-PSMA-11 and [¹⁸F]PSMA-1007. Ten additional mice bearing C4-2 xenografts were subjected to ex vivo biodistribution with either [¹⁸F]AlF-PSMA-11 (n = 5) or [¹⁸F]PSMA-1007 (n = 5). Absolute SUV_mean and SUV_max values were significantly higher for [¹⁸F]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 [¹⁸F]AlF-PSMA-11 and [¹⁸F]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 [¹⁸F]AlF-PSMA-11 (p < 0.01). In healthy organs, [¹⁸F]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 [¹⁸F]PSMA-1007. Absolute tumor uptake was higher with [¹⁸F]PSMA-1007 in all tumors. Tumor-to-organ ratios did not differ significantly in high PSMA expressing tumors, but were higher for [¹⁸F]AlF-PSMA-11 in low PSMA expressing tumors. Furthermore, [¹⁸F]PSMA-1007 showed higher uptake in healthy organs.