The effect of the triazene compound CT913 on ovarian cancer cells in vitro and its synergistic interaction with the PARP-inhibitor olaparib.

OBJECTIVES:Extending the therapeutic spectrum of PARP-inhibitors (PARPi) beyond BRCA1-deficiency and/or overcoming PARPi-resistance is of high clinical interest. This is particularly true for the identification of innovative therapeutic strategies for ovarian cancer, given the recent advances in the use of PARPi in clinical practice. In this regard, the combination of PARPi with chemotherapy is a possible strategy for defining new therapeutic standards. In this study, we analyzed the therapeutic effect of novel triazene derivatives, including the drug CT913 and its metabolite CT913-M1 on ovarian cancer cells and describe their interaction with the PARPi olaparib. METHODS:In vitro assays for drug characterization including RNA-Seq were applied in a selected panel of ovarian cancer cell lines. RESULTS:CT913 treatment conferred a dose-dependent reduction of cell viability in a set of platinum-sensitive and platinum-resistant ovarian cancer cell lines with an IC50 in the higher micromolar range (553-1083 μM), whereas its metabolite CT913-M1 was up to 69-fold more potent, especially among long-term treatment (IC50 range: 8-138 μM). Neither of the drugs sensitized for cisplatin. CT913 conferred synthetic lethality in BRCA1-deficient ovarian cancer cells, indicating that its effect is augmented by a deficiency in homologous recombination repair (HR). Furthermore, CT913 showed a synergistic interaction with olaparib, independently of BRCA1 mutational status. CT913 strongly induced CDKN1A transcription, suggesting cell cycle arrest as an early response to this drug. It moreover downregulated a variety of transcripts involved in DNA-repair pathways. CONCLUSIONS:This is the first study, suggesting the novel triazene drug CT913 as enhancer drug for extending the therapeutic spectrum of PARPi.