3AcFNP-59 for Positron Emission Tomography Imaging of Cholesterol Trafficking and Utilization

Cholesteryl ester analogues of [¹⁸F]FNP-59 have the ability to provide information on cholesterol trafficking and utilization at earlier time points than those of [¹⁸F]FNP-59 or [¹³¹I]NP-59. It is well-known that free cholesterol and cholesteryl esters have differing distribution profiles and that they can be interconverted enzymatically. Substitution of the ester influences the rate of cholesterol ester hydrolysis and the subsequent mixing of cholesterol esters with the lipid pool in the body. This can be utilized by preparing esters that are more readily taken up by lipoprotein, are quickly hydrolyzed and mixed with the endogenous lipid pool and delivered to tissues of interest more quickly than free cholesterol analogues that require esterification for lipoprotein association. The acetyl ester of FNP-59 demonstrated the preferred uptake properties and response to adrenal cortical manipulation, indicating its ability to image hormone production. Finally, dosimetry studies were conducted in preparation for the clinical translation of [¹⁸F]3AcFNP-59.