Harnessing IMGN853-mediated cell cytoxicity response by modulating FRα expression in ovarian cancer.

Abstract

e17061 Background: Ovarian cancer (OC) is the fifth leading cause of cancer-related death among women in the United States. Standard treatment includes debulking surgery followed by platinum based chemotherapy. While most tumors respond to this treatment, 70% of the tumors recur and develop into a chemo-resistant disease. There is a need for new therapies targeting recurrent chemoresistant OC. To address this need, Mirvetuximab Soravtansine (ImmunoGen, Waltham, MA) has developed an antigen-drug conjugate (ADC) containing DM4, a highly potent maytansinoid derivative that induces the cell cycle arrest, conjugated to an antibody targeting folate receptor alpha (FRα). Mirvetuximab Soravtansine (IMGN853), was tested in Phase I clinical trials on women with recurrent OC and showed low grade toxicity profile and activity in platinum-resistant disease. The goal of this study is to characterize the mechanism(s) leading to IMGN853 resistance in OC and test whether anticancer drugs targeting these mechanisms could be used in combination with IMGN853 for an additive/synergistic therapeutic effect. Methods: In vitro experiments were performed to detect and modulate FRα expression. Results: We show that sensitivity of OC cell lines to IMGN853 correlates with the expression levels of FRα (R = 0.82). Long-term exposure of sensitive cells to sublethal doses of IMGN853 induces drug resistance which correlates with decreased FRα expression. Anti-cancer drugs such as dexamethasone (Dex), which induces glucocorticoid receptors, or epigenetic modulators (Trichostatin A and 5-Azacytidine) induce FRα expression in SKOV3 and OVCAR8 OC cells, suggesting the possibility to use these drugs to maintain sensitivity of OC cells to IMGN853 and increase its therapeutic window. The therapeutic benefits of combining each of these drugs with IMGN853 will be further tested in mice using ovarian cancer patients’ derived xenografts with different FRα expression levels. Conclusions: These findings have clinical implications as they indicate that OC sensitivity to IMGN853 is modulated in part by changes in FRα levels. Resistance to this drug may be overcome by simultaneous treatment with Dex or other anti-cancer drugs such as TSA or AZA.