18 F-Labeled dihydropyridines via Hantzsch reaction for positron emission tomography of P-glycoprotein dysfunction

Despite the availability of various C-11-labeled positron emission tomography (PET) tracers for assessing P-glycoprotein (P-gp) function, there are still limitations related to complex metabolism, high lipophilicity, and low baseline uptake. This study aimed to address these issues by exploring a series of customized dihydropyridines (DHPs) with enhanced stability and reduced lipophilicity as alternative PET tracers for P-gp dysfunction. Compared with verapamil and the rest DHPs, dimethyl 4-(4-fluorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (1) exhibited superior cellular uptake differences between the human gastric cancer cell line SGC7901 and its drug-resistant counterpart. [F-18]1 is successfully synthesized using a novel "hot-Hantzsch" approach in 22.1 +/- 0.1 % radiochemical yields. MicroPET/CT imaging demonstrated that the uptake of [F-18]1 in the brains of P-gp blocked mice increased by > 3 times compared to the control group. Additionally, [F-18]1 displayed favorable lipophilicity (log D = 2.3) and excellent clearance characteristics, making it a promising tracer candidate with low background noise and high contrast.