Comparative study of [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p as novel PD-L1 targeting PET probes for tumor imaging.

ABSTRACT

PD-L1 is expressed in many tumors but rarely in normal tissues, therefore, it can be a target of PET imaging. In this work, we developed new peptide-based PET probes [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p with yields of 20-25 % and 40-55 %, respectively. [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p were synthesized within 30 min with high molar activities. [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p showed good stability in vivo and in vitro. In vitro cell studies showed [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p target PD-L1 specifically, with high uptake of 61.52 ± 4.39 and 19.29 ± 2.17 %ID/1 million cells in B16F10 cells at 60 min, respectively. Biodistribution results showed that both [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1p had lower liver accumulation. In vivo PET imaging results showed that [18F]AlF-PAI-PDL1p had a high tumor uptake of 4.23 ± 0.81 %ID/g at 2 h and increased uptake of 6.60 ± 1.01 %ID/g at 12 h. [68Ga]Ga-PAI-PDL1p also showed high tumor uptake of 2.30 ± 0.20 %ID/g at 2 h and slightly increased uptake of 3.80 ± 0.26 %ID/g at 6 h. In conclusion, [18F]AlF-PAI-PDL1p and [68Ga]Ga-PAI-PDL1 seemed to be potential tracers for PET imaging of PD-L1 expression.