Abstract 1237: Biological effects of a FRα-targeting antibody-drug conjugate, IMGN853 (mirvetuximab soravtansine) in high-grade serous ovarian cancer

Abstract

Abstract Objective: Autophagic cell death is an important mechanism induced by blocking folate receptor (FRα) in inhibiting tumor growth. Here, our objective is to examine the biological effects of IMGN853 (mirvetuximab soravtansine) in preclinical models of ovarian cancer and to identify potential combination therapies. Methods: In vitro, immunoblotting, assays for cell viability, proliferation and cell cycle by fluorescence-activated cell sorting (FACS) were performed in an array of high grade serous carcinoma (HGSC) cell lines. Autophagy flux and activities of autophagy factors were also determined. In vivo, metastasis mouse models were used for testing the therapeutic efficacy of IMGN853 monotherapy or in combination with olaparib or cisplatin. Potential synergy with these drugs was assessed using in vitro assays. The resulting tumors were subjected to immunohistochemistry and reverse phase protein arrays (RPPA). Results: Data from the Cancer Genome Atlas Data (TCGA) revealed that FRα copy-number alterations was significantly correlated with shorter disease-free survival in patients with HGSC. Autophagy marker LC3 was upregulated following monotherapy with IMGN853 as well as in combination of IMGN853 with olaparib or cisplatin in HGSC cell lines such as OVCA8 and OVCA432, which express high-level of FRα. Experiments using metastatic HGSC models showed that IMGN853 monotherapy reduced tumor growth (30% change); the combination of IMGN853 and olaparib was superior to olaparib monotherapy (24% change; p 0.0033). Integrated analysis on RPPA revealed increased expression of ABL1 and PEA15 in the groups treated with IMGN853 monotherapy or in combination with olaparib. We further found reduced FRα expression and increased caspase 3 expression in IMGN853 groups compared with control. Conclusion: Our results point to sustained autophagy in FRα positive cells as a mechanism of effect of IMGN853. These findings could have implications for clinical development of anti-FRα therapies, especially in combination with other drugs such as olaparib. Citation Format: Anca Chelariu-Raicu, Elaine Stur, Cristina Ivan, Robert L. Coleman, Anil K. Sood, Wen Yunfei. Biological effects of a FRα-targeting antibody-drug conjugate, IMGN853 (mirvetuximab soravtansine) in high-grade serous ovarian cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1237.