JPI-547, a novel dual inhibitor of PARP1/2 and tankyrase is more effective than first-generation PARP inhibitors in preclinical BRCA1/2-mutated cancer models

BACKGROUND: Poly(ADP-ribose) polymerase (PARP) inhibitors are highly effective therapies for BRCA1/2-mutated tumors. However, most patients eventually develop acquired resistance. Here, we report that JPI-547, a second-generation PARP inhibitor targeting both PARP1/2 and tankyrase, demonstrates potent antitumor activity in olaparib-sensitive and resistant BRCA1/2 mutant models. METHODS: Olaparib-resistant (OR) models were generated using BRCA-mutated human ovarian and breast cancer cell lines and ovarian Patient-Derived Tumor Xenograft (PDTX) by exposing to olaparib. For clinical relevance, public mRNA microarray datasets of ovarian and breast cancer were analyzed. RESULTS: JPI-547 demonstrated better antitumor efficacy in both olaparib-sensitive and resistant BRCA-mutated preclinical models than first-generation PARP inhibitors. Mechanistically, the on-target inhibition of PARP1/2 and tankyrase by JPI-547 strongly inhibited the restoration of homologous recombination (HR) activity by suppressing RAD51 expression. This action resulted in the retardation of tumor growth in olaparib-sensitive and resistant ovarian PDTX models. Furthermore, high RAD51 expression was significantly associated with poor prognosis in ovarian and breast cancer patients based on public mRNA expression data. CONCLUSION: These results suggest the scientific rationale for further clinical development of JPI-547 for treating both PARP inhibitor-sensitive patients and those resistant to first-generation PARP inhibitors in BRCA-mutated cancers.