Abstract
ENMD-2076 is a novel, orally-active molecule that has been shown to have significant activity against Aurora A kinase as well as multiple receptor tyrosine kinases (RTK). We investigated the single agent activity of ENMD-2076 against MM cells in vitro and in vivo, and in combination with lenalidomide. ENMD-2076 free base showed significant cytotoxicity against MM cells with a mean LC50 of 3.84±0.86 μM at 48 hours in vitro. Cytotoxicity was associated with cleavage of caspase 3, 8, 9 and PARP, and loss of mitochondrial membrane potential as early as 6 hours. ENMD-2076 free base inhibited c-kit, FGFR-1, 3 and VEGFR1 and subsequently inhibition of downstream targets phosphorylated (p)-BAD, p-Foxo1a and p-GSK-3β was observed at 6 hours. NOD/SCID mice implanted with H929 human plasmacytoma xenografts and treated for 30 days with 50, 100, 200mg/kg/d ENMD-2076 showed a dose-dependent inhibition of tumor growth (Figure 1), with minimal toxicity as assessed by the stable weight of treated animals. Immunohistochemical staining of tumors from sacrificed animals showed significant reduction in Ki67 at all dose levels of treatment compared to control tumors. An increase in cleaved caspase-3 was observed on Western blot from the lysates of H929 tumors obtained from treated animals. ENMD-2076 free base also showed synergistic cytotoxic activity when combined with lenalidomide against H929, MM1.R and MM1.S cells as assessed by MTT assay and Annexin-V/PI staining. Using the Chou-Talalay method, the combination indices (CI) were < 1 for all three cell lines across a range of concentrations of ENMD-2076 free base (0.25–1.0 μM) plus lenalidomide (2.5–10 μM) indicating synergistic activity (CI=0.362 H929; CI=0.315 MM1.R; CI=0.415 MM1.S). Our results provide rationale for the investigation of ENMD-2076 alone and in combination with lenalidomide in patients with multiple myeloma.
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Disclosures: No relevant conflicts of interest to declare.
