Novel Pyrrolobenzodiazepine Benzofused Hybrid Molecules Inhibit Nuclear Factor-Kb Activity And Synergize With Bortezomib And Ibrutinib In Hematologic Cancers

Chronic lymphocytic leukemia (CLL) and multiple myeloma are incurable hematologic malignancies that are pathologically linked with aberrant nuclear factor-kappa B (NF-KB) activation. In this study, we identified a group of novel C8-linked benzofused pyrrolo[2,1c][1,4]benzodiazepine monomeric hybrids capable of sequence-selective inhibition of NF-KB with low nanomolar LD50 values in CLL (n=46) and multiple myeloma cell lines (n=5). The lead compound, DC-1-192, significantly inhibited NF-KB DNA binding after just 4 h of exposure, demonstrating inhibitory effects on both canonical and non-canonical NF-KB subunits. In primary CLL cells, sensitivity to DC-1-192 was inversely correlated with RelA subunit expression (r2=0.2) and samples with BIRC3 or NOTCH1 mutations showed increased sensitivity (P=0.001). RNAsequencing and gene set enrichment analysis confirmed the over-representation of NF-KB regulated genes in the downregulated gene list. Furthermore, in vivo efficacy studies in NOD/SCID mice, using a systemic RPMI 8226 human multiple myeloma xenograft model, showed that DC1-192 significantly prolonged survival (P=0.017). In addition, DC1-192 showed synergy with bortezomib and ibrutinib; synergy with ibrutinib was enhanced when CLL cells were co-cultured on CD40L-expressing fibroblasts in order to mimic the cytoprotective lymph node microenvironment (P=0.01). Given that NF-KB plays a role in both bortezomib and ibrutinib resistance mechanisms, these data provide a strong rationale for the use of DC-1-192 in the treatment of NF-KB-driven cancers, particular