Preclinical Characterization of AZD9574, a Blood–Brain Barrier Penetrant Inhibitor of PARP1

Abstract Purpose: We evaluated the properties and activity of AZD9574, a blood–brain barrier (BBB) penetrant selective inhibitor of PARP1, and assessed its efficacy and safety alone and in combination with temozolomide (TMZ) in preclinical models. Experimental Design: AZD9574 was interrogated in vitro for selectivity, PARylation inhibition, PARP-DNA trapping, the ability to cross the BBB, and the potential to inhibit cancer cell proliferation. In vivo efficacy was determined using subcutaneous as well as intracranial mouse xenograft models. Mouse, rat, and monkey were used to assess AZD9574 BBB penetration and rat models were used to evaluate potential hematotoxicity for AZD9574 monotherapy and the TMZ combination. Results: AZD9574 demonstrated PARP1-selectivity in fluorescence anisotropy, PARylation, and PARP-DNA trapping assays and in vivo experiments demonstrated BBB penetration. AZD9574 showed potent single agent efficacy in preclinical models with homologous recombination repair deficiency in vitro and in vivo. In an O6-methylguanine-DNA methyltransferase (MGMT)–methylated orthotopic glioma model, AZD9574 in combination with TMZ was superior in extending the survival of tumor-bearing mice compared with TMZ alone. Conclusions: The combination of three key features—PARP1 selectivity, PARP1 trapping profile, and high central nervous system penetration in a single molecule—supports the development of AZD9574 as the best-in-class PARP inhibitor for the treatment of primary and secondary brain tumors. As documented by in vitro and in vivo studies, AZD9574 shows robust anticancer efficacy as a single agent as well as in combination with TMZ. AZD9574 is currently in a phase I trial (NCT05417594). See related commentary by Lynce and Lin, p. 1217