Synthesis, Preclinical Toxicity, and Biodistribution of [¹⁸F]AVT-011 to Assess the P-Glycoprotein Function

Many studies have reported the role of P-glycoprotein (Pgp) in chemoresistance in various pathological conditions such as cancer and neurodegenerative diseases, such as Alzheimer's. In this study, we are reporting the high-performance liquid chromatography (HPLC)-based purification of fluorine-18 [¹⁸F]AVT-011 and its preclinical evaluation. AVT-011 was labeled with ¹⁸F using the nucleophilic substitution method by heating the reaction mixture at 110°C for 10 min, followed by purification using preparative HPLC and C18ec cartridge. The in vitro cell uptake study was carried out in U87 cells with and without an inhibitor. The preclinical toxicity was carried out in CD1 mice in three groups, including control, AVT-011 treated, and [¹⁸F]AVT-011 treated. The biodistribution study was done in CD1 mice (n = 12) after intravenous injection of 4-6 MBq [¹⁸F]AVT-011, and mice were sacrificed at various time intervals. A dose of 3.7 ± 0.7 MBq of [¹⁸F]AVT-011 was injected intravenously in the healthy Swiss albino mice, and the whole-body micro-positron emission tomography was acquired at 0-, 30-, 60-, and 120-min postinjection. The radiochemical purity of [¹⁸F]AVT-011 was 97 ± 1.5% as evaluated by radio-HPLC with a yield of 14 ± 2% and was stable up to 95% under in vitro conditions in blood and in vivo conditions up to 4 h. The in vitro cell uptake study showed a significant difference in control (27.4 ± 2.1%) and blocked U987 cells (73.2 ± 3.2%) after incubation of 120 min. The tissue distribution in mice showed the highest uptake in the liver (17.3 ± 2.4%), kidneys (16.6 ± 3.1%), lungs (10.4 ± 2.9%), and spleen (5.6 ± 0.8%) at 15 min, and the activity was washed out with time. The radioactivity cleared through the hepatorenal pathway. The animal imaging study also demonstrates a similar biodistribution pattern. [¹⁸F]AVT-011 showed higher specific activity than the cartridge-based method but showed similar biological activity.