iMN041 is an immunotherapeutic and an effective treatment in mouse xenograft models of pancreatic cancer, renal cancer and triple negative breast cancer

Abstract

Abstract Background iMN013 (5-aza-2',2'-difluorodeoxycytidine), a DNA methyl transferase inhibitor and ribonucleotide reductase inhibitor, and its prodrug iMN041 (3',5'-di-trimethylsilyl-2',2'-difluro-5- azadeoxycytidine), have been shown to be active in mouse xenograft models of hematogenous and solid tumors. In a xenograft of non-small cell lung cancer (NCI-H460), iMN041 treated mice demonstrated a marked inflammatory response upon analysis of tumor histology, which was hypothesized to be mediated by upregulation of natural killer (NK) cells. This study aimed to characterize the antitumor immune responses generated by iMN041 and test the efficacy iMN041 in solid tumors with poor prognosis. Methods In the Renca syngeneic mouse model, tumors were harvested following two doses of iMN041 or vehicle control, and analyzed by fluorescent-activated cell sorting for an antitumor immune response. iMN041 was also tested for tumor growth inhibition and animal survival for up to 42 days in xenograft models of pancreatic, renal, and triple negative breast cancer. Results Tumors from mice implanted with the Renca cell line and treated with iMN041 demonstrated an increase in granzyme B in NK (p = 0.024) and NKT cells (p = 0.004), an increase in the ratios of CD8-T to regulatory T cells (Treg) (p = 0.0026) and CD4-T to Treg cells (p = 0.022) and a decrease in myeloid-derived suppressor cells (p = 0.040), compared to vehicle controls. A significant decrease in MAGE-A positive tumor cells in treated mice, concordant with a proportional decrease in all live tumor cells, suggests that these cells are one of the main targets of the activated immune system. Xenograft models of the triple negative breast cancer cell line DU4475, renal cancer cell lines 786-O and Caki-1, and pancreatic cancer cell lines CFPAC-1 and SW1990, demonstrated significantly lower tumor volumes, and, where there were a sufficient number of events, significantly improved survival in treated mice compared to vehicle control mice. Conclusions In mouse cancer models, iMN041 is an effective treatment for solid tumors mediated in part through a unique antitumor immune response.