Abstract P5-06-03: Combination of the PARP inhibitor E7449 with eribulin +/- carboplatin in preclinical models of triple negative breast cancer

Abstract

Abstract Introduction: In a small neoadjuvant study in patients with triple negative breast cancer (TNBC) the combination of eribulin plus carboplatin was effective, with a pathologic complete response rate of 43% following 4 cycles of treatment. Significant numbers of sporadic TNBC tumors are deficient in DNA repair capacity and share clinical and pathological features with hereditary BRCA1 mutant disease. PARP inhibitors have demonstrated synthetic lethality in cancer cells with defective DNA repair and have therapeutic potential for TNBC. In this study we describe the combination of PARP inhibitor E7449 with eribulin +/- carboplatin in preclinical models of TNBC. Methods: E7449, an orally available PARP inhibitor, was administered in combination with eribulin +/- carboplatin to 4 s.c. xenograft models of TNBC: MDA-MB-436 (BRCA1 mutant, PTEN deficient), MDA-MB-468 (BRCA wild type, PTEN deficient), HCC1806 and MDA-MB-231 (BRCA and PTEN wild type). Results and Discussion: Addition of E7449 to eribulin significantly delayed tumor progression in PTEN deficient MDA-MB-468 xenografts. In the BRCA1 mutant and PTEN deficient MDA-MB-436 xenograft model, combination of E7449 with eribulin enhanced antitumor activity versus eribulin alone. Similar potentiation was observed for carboplatin upon combination with E7449. Treatment of MDA-MB-436 xenografts with the triple combination of E7449 + eribulin + carboplatin was more efficacious than any double combination and was well tolerated at the doses examined. In contrast, no significant combination activity was observed for E7449 plus eribulin in the BRCA and PTEN wild type xenografts HCC1806 and MDA-MB-231, and similarly no potentiation of carboplatin was observed in an MDA-MB-231 xenograft. Notably, combination activity was observed in the BRCA1 mutant (MDA-MB-436) and PTEN deficient (MDA-MB-436 and MDA-MB-468) xenografts and not in the BRCA and PTEN wild-type models (HCC1806 and MDA-MB-231). Data from ongoing studies to evaluate the combination activity of E7449 + eribulin in patient-derived xenograft (PDx) models of TNBC will be presented at the meeting. Potential biomarkers of sensitivity to the combination are under investigation in both cell line xenograft and PDx models and will be described. Conclusion: The addition of E7449 to eribulin +/- carboplatin increased antitumor activity in a subset of TNBC models. Biomarker studies aimed at a better understanding of the underlying cause of sensitivity are underway. The preclinical data support assessment of E7449 + eribulin + carboplatin combination therapy in the current phase I/II clinical trial. Citation Format: Sharon McGonigle, Jiayi Wu, Donna Kolber-Simonds, Natalie C Twine, Jue-lon Shie, Noel Taylor, Sergei Agoulnik, Zoltan Dezso, Shannon McGrath, Mark Matijevic, Shanqin Xu, Galina Kuznetsov, Mary Woodall-Jappe, Kenichi Nomoto. Combination of the PARP inhibitor E7449 with eribulin +/- carboplatin in preclinical models of triple negative breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-06-03.