PARP inhibitors are proven chemotherapeutics and serve as lead structures for the development of PARP-targeted in vivo imaging probes. Given the clinical potential of PARP imaging for the detection and stratification of various cancers, the development of novel PARP imaging probes with improved pharmacologi-cal profiles over established PARP imaging agents is warranted. Here, we present a novel 18F-labeled PARP radiotracer based on the clinically superior PARP inhibitor talazoparib. An automated radiosynthesis of [18F]talazoparib (RCY: 13 ± 3.4 %; n = 4; molar radioactivity 52 – 176 GBq/μmol) was achieved using a “Design of Experiments” (DoE) optimized copper-mediated radiofluorination reaction. The chiral product was isolated from the reaction mixture using 2D reversed-phase/chiral radio-HPLC (>99% ee). (8S, 9R)-[18F]Talazoparib demonstrated PARP binding in HCC1937 cells in vitro and showed an excellent tumor-to-blood ratio in xeno-graft-bearing mice (10.2 ± 1.5). Despite expected uptake into muscle, bone, and abdominal tissue, a favorable pharmacological profile in terms of excretion, blood half-life, and target engagement was observed in the pilot in vivo study. This synthesis of [18F]talazoparib exemplifies how a DoE based tracer development pipeline can enable the radiosyntheses of clinically relevant but synthetically challenging radiolabeled compounds of high interest to the imaging community.
DoE Optimization Empowers the Automated Preparation of Enantiomerically Pure [18F]Talazoparib and its In Vivo Evaluation as a PARP Radiotracer.
