11C-GSK1482160

The overexpression of P2X7R is associated with neuroinflammation and plays an important role in various neurodegenerative diseases. The [¹⁸F]fluoropropyl derivative of GSK1482160, [¹⁸F]IUR-1602, has been first prepared and examined as a new potential P2X7R radioligand. The reference standard IUR-1602 was synthesized from tert-butyl (S)-5-oxopyrrolidine-2-carboxylate, fluoropropylbromide, and 2-chloro-3-(trifluoromethyl)benzylamine with overall chemical yield 13% in three steps. The target tracer [¹⁸F]IUR-1602 was synthesized from desmethyl-GSK1482160 with 3-[¹⁸F]fluoropropyl tosylate, prepared from propane-1,3-diyl bis(4-methylbenzenesulfonate) and K[¹⁸F]F/Kryptofix2.2.2, in two steps and isolated by HPLC combined with SPE in 2-7% decay corrected radiochemical yield. The radiochemical purity was >99%, and the molar activity at end of bombardment (EOB) was 74-370 GBq/μmol. The potency of IUR-1602 in comparison with GSK1482160 was determined by a radioligand competitive binding assay using [¹¹C]GSK1482160, and the binding affinity K_i values for IUR-1602 and GSK1482160 are 23.6 and 3.07 nM, respectively. The initial in vitro evaluation results, 8-fold less potency of [¹⁸F]IUR-1602 compared to [¹¹C]GSK1482160, prevent further in vivo evaluation of [¹⁸F]IUR-1602 in animals and human.

A radio-analytical RP-HPLC method was developed and validated to support production of the P2X7-receptor-targeted [¹¹C]GSK1482160 radiopharmaceutical. Method validation included characterization of retention times, peak shapes, linearity, accuracy, precision, selectivity, limits of detection and quantitation (UV signal), radiochemical stability, as well as analytical method range and robustness. The validated radio-HPLC method is suitable for the definition of [¹¹C]GSK1482160 radiochemical identity, radiochemical purity, as well as molar activity, and is being employed in support of human studies with [¹¹C]GSK1482160.