Poly(ADP-ribose) polymerase 1 (PARP1) is a multifunctional protein involved in diverse cellular functions, notably DNA damage repair. Pharmacological inhibition of PARP1 has therapeutic benefits for various pathologies. Despite the increased use of PARP inhibitors, challenges persist in achieving PARP1 selectivity and effective blood-brain barrier (BBB) penetration. The development of a PARP1-specific positron emission tomography (PET) radioligand is crucial for understanding disease biology and performing target occupancy studies, which may aid in the development of PARP1-specific inhibitors. In this study, we leverage the recently identified PARP1 inhibitor, AZD9574, to introduce the design and development of its ¹⁸F-isotopologue ([¹⁸F]AZD9574). Our comprehensive approach, encompassing pharmacological, cellular, autoradiographic, and in vivo PET imaging evaluations in non-human primates, demonstrates the capacity of [¹⁸F]AZD9574 to specifically bind to PARP1 and to successfully penetrate the BBB. These findings position [¹⁸F]AZD9574 as a viable molecular imaging tool, poised to facilitate the exploration of pathophysiological changes in PARP1 tissue abundance across various diseases.

The sigma-1 receptor (R) is a unique intracellular protein. R plays a major role in various pathological conditions in the central nervous system (CNS), implicated in several neuropsychiatric disorders. Imaging of R in the brain using positron emission tomography (PET) could serve as a noninvasively tool for enhancing the understanding of the disease's pathophysiology. Moreover, R PET tracers can be used for target validation and quantification in diagnosis. Herein, we describe the radiosynthesis, PET/CT imaging of novel R C-labeled radioligands based on 6-hydroxypyridazinone, [C]HCC0923 and [C]HCC0929. Two radioligands have high affinities to R, with good selectivity. In mice PET/CT imaging, both radioligands showed appropriate kinetics and distributions. Additionally, the specific interactions of two radioligands were reduced by compounds and (self-blocking). Of the two, [C]HCC0929 was further investigated in positive ligands blocking studies, using classic R agonist SA 4503 and R antagonist PD 144418. Both R ligands could extensively decreased the uptake of [C]HCC0929 in mice brain. Besides, the biodistribution of major brain regions and organs of mice were determined . These studies demonstrated that two radioligands, especially [C]HCC0929, possessed ideal imaging properties and might be valuable tools for non-invasive quantification of R in brain.