Purpose: The current study presents [(18)F]PARPi as imaging agent for PARP1 expression.
Procedures: [(18)F]PARPi was generated by conjugating a 2H-phthalazin-1-one scaffold to 4-[(18)F]fluorobenzoic acid. Biochemical assays, optical in vivo competition, biodistribution analysis, positron emission tomography (PET)/X-ray computed tomography, and PET/magnetic resonance imaging studies were performed in subcutaneous and orthotopic mouse models of glioblastoma.
Results: [(18)F]PARPi shows suitable pharmacokinetic properties for brain tumor imaging (IC50 = 2.8 ± 1.1 nM; logPCHI = 2.15 ± 0.41; plasma-free fraction = 63.9 ± 12.6 %) and accumulates selectively in orthotopic brain tumor tissue. Tracer accumulation in subcutaneous brain tumors was 1.82 ± 0.21 %ID/g, whereas in healthy brain, the uptake was only 0.04 ± 0.01 %ID/g.
Conclusions: [(18)F]PARPi is a selective PARP1 imaging agent that can be used to visualize glioblastoma in xenograft and orthotopic mouse models with high precision and good signal/noise ratios. It offers new opportunities to non-invasively image tumor growth and monitor interventions.
Keywords: Glioblastoma; Imaging; Orthotopic; PARP1; PET.