Abstract 4847: Evaluation of the combination of olaparib and cediranib in small-cell lung cancer cells

Metastatic Small cell lung cancer (SCLC) is exceptionally lethal, having a median survival of 9-10 months from the time of diagnosis and a 5 year survival rate of less than 2 percent. More effective treatment approaches to SCLC are desperately needed. Poly ADP-ribose polymerase (PARP) inhibitor such as olaparib exploit the concept of synthetic lethality by selectively targeting cancer cells with defective DNA repair pathways. Preclinical data indicates that SCLC cell lines overexpress PARP and are sensitive to PARP inhibition, and PARP inhibitors show promise in the clinical setting of SCLC. The identification of combination regimens that potentiate the efficacy of PARP inhibition would be of great clinical value. Recent findings indicate that olaparib and the vascular endothelial growth factor receptor (VEGFR) inhibitor, cediranib, is an effective therapeutic combination in patients with BRCA wild-type ovarian cancer. Therefore, we evaluated the efficacy of the olaparib and cediranib combinations in SCLC models. Human SCLC cell lines, NCI-H841, H526, COR-L24 and murine SCLC cell line TKOmTmG were sensitive to olaparib or cediranib therapy in vitro as determined by Cell Titer Glo® assay. Moreover, a significantly greater effect on cell viability was observed when olaparib and cediranib were used in combination. Likewise, in H841 xenograft models, single agent treatment of olaparib or cediranib inhibited tumor growth, and combination treatment of olaparib plus cediranib induced tumor regression. Western blot analysis indicated that treatment with cediranib or the combination of olaparib and cediranib induced PD-L1 protein expression both in vivo and in vitro. In TKOmTmG xenograft model in syngeneic mice, programmed death-ligand 1 (PD-L1) inhibitor plus olaparib or olaparib/cediranib combination resulted in superior combined efficacy compared to the respective single agent therapies in terms of tumor growth inhibition. These data indicate that olaparib plus cediranib may be an effective therapeutic strategy for the treatment of SCLC. Further study is warranted to understand the mechanism of action and clinical activity. Citation Format: Naoto Morikawa, Monique B. Nilsson, Irene Guijarro, You-Hong Fan, Alissa Poteete, John V. Heymach. Evaluation of the combination of olaparib and cediranib in small-cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4847.