Abstract 5543: Inhibition of the tyrosine kinase receptor Axl blocks cell invasion and promotes apoptosis in pancreatic cancer cells

Pancreatic cancer is virtually a uniformly lethal disease and a better understanding of the molecular basis of this malignancy is needed to discover new ways to prevent or treat this deadly disease. A central feature of malignant cells is their ability to disseminate from the primary tumor and establish local and distant metastases. In most cases, cancer patients with localized disease have significantly better prognosis than those with metastatic tumors and the majority of cancer mortality is associated with metastatic disease rather than the primary tumor. The receptor tyrosine kinase Axl is overexpressed in over 50% of pancreatic cancers and expression of Axl in these cancers is highly associated with a poor prognostic outcome for patients. Axl is a TAM family receptor tyrosine kinase involved in multiple aspects of tumorigenesis. Increased expression of Axl is associated with increased oncogenic transformation, cell survival, proliferation, migration, angiogenesis, and cellular adhesion. The known ligand for Axl is the Growth Arrest Specific Gene-6 (Gas6) protein and it's binding to Axl leads to Axl autophosphorylation and activation of downstream signaling pathways including MAPK and PI3K/Akt pathways. We discovered and developed a small molecule Axl kinase inhibitor, HCI-2084, and explored it for the effectiveness of targeting the Axl kinase in cell-based models of pancreatic cancer. HCI-2084 is a 2-((2,5-substitutedpyrimidin-4-yl)amino)-N,N-dimethyl benzene sulfonamide that has low nanomolar (IC50 = 12 nM) activity against the Axl kinase in a biochemical assays. In further biochemical evaluation, HCI-2084 was shown to inhibit the entire TAM family of kinases (IC50 Axl = 12 nM; IC50 Mer = 60 nM; Tyro3 = 71% inhibition at 200 nM). HCI-2084 inhibits a small number of additional kinases when screened in a kinase panel of over 500 kinases and has demonstrated an ADMET profile suggesting it may be a potential clinical candidate. In cell proliferation assays, HCI-2084 significantly inhibited pancreatic cancer cell growth at concentrations as low as 30 nM. In pharmacodynamic assays, HCI-2084 dramatically inhibited Akt signaling (pAKT S473) downstream of GAS6 stimulation in pancreatic cancer cell lines. Consistent with the known function of Axl, HCI-2084 inhibited Gas6-induced migration and invasion of pancreatic cancer cells in vitro and potently induces apoptosis. Mechanistically, HCI-2084 decreases the expression of genes involved in Epithelial-Mesenchyma