GMP-Compliant Radiosynthesis of [18F]GP1, a Novel PET Tracer for the Detection of Thrombi

Thrombus formation and thromboembolic events play important roles in various cardiovascular pathologies. The key receptor involved in platelet aggregation is the fibrinogen receptor glycoprotein IIb/IIIa. [18F]GP1, a derivative of the GPIIb/IIIa antagonist elarofiban, is a specific 18F-labeled small-molecule radiotracer that binds with high affinity to GPIIb/IIIa receptors of activated platelets. An improved, robust and fully automated radiosynthesis of [18F]GP1 has been developed. [18F]GP1 has been synthesized with decay corrected radiochemical yields of 38 ± 6%, with a radiochemical concentration up to 1900 MBq/mL, molar activities of 952–9428 GBq/µmol and a radio-chemical purity >98%. After determination of the optimal reaction conditions, in particular for HPLC separation, adaption of the reaction conditions to PET center requirements, validation of the manufacturing process and the quality control methods, the synthesis of [18F]GP1 was successfully implemented to GMP standards and was available for clinical application. We describe the GMP-compliant synthesis of the novel radiotracer [18F]GP1. Moreover, we provide some proof-of-concept examples for clinical application in the cardiovascular field. PET/CT with the novel small-molecular radiotracer [18F]GP1 may serve as a novel highly sensitive tool for visualizing active platelet aggregation at the molecular level.