Identification And Characterization Of A Novel Smoothened Antagonist For The Treatment Of Cancer With Deregulated Hedgehog Signaling

The Hedgehog (Hh) pathway is a highly conserved signaling system that plays an important role in embryonic development and tissue homeostasis through regulation of cell differentiation and proliferation, and deregulated Hh signaling has been implicated in variety of cancers. Two distinct mechanisms are responsible for inappropriate and uncontrolled Hh pathway activation in human malignancies: ligand-dependent, due to over-expression of Hh ligand, and ligand-independent, resulting from genetic mutations in pathway components such as Patched (Ptch) and Smoothened (Smo). Smo, a member of the class F G-protein coupled receptor family, is a key regulator of Hh signaling pathway, and therefore is an attractive target for pathway modulation. We have identified a potent and selective small molecule antagonist of Smo. This novel molecule (LY2940680) binds to the Smo receptor and potently inhibits Hh signaling in Daoy, a human medulloblastoma tumor cell line, and C3H10T½, a mouse mesenchymal cell line. Importantly, LY2940680 binds to and inhibits the functional activity of resistant Smo mutant (D473H) produced by treatment with GDC-0449 (a Smo antagonist from Genentech). LY2940680 also has excellent pharmacokinetic properties in rodent and non-rodent species. Treatment of Ptch +/− p53 −/− transgenic mice, which spontaneously develop medulloblastoma, with oral administration of LY2940680 produced remarkable efficacy and significantly improved their survival. Magnetic resonance imaging of these mice revealed rapid kinetics of anti-tumor activity. Immunohistochemistry analysis of medulloblastoma tumors showed that LY2940680 treatment induced Caspase-3 activity and reduced proliferation. LY2940680 inhibited Hh regulated gene expression in the subcutaneous xenograft tumor stroma and produced significant anti-tumor activity. In summary, we have characterized an orally bio-available small molecule Smo antagonist that may provide therapeutic benefit to cancer patients with deregulated Hh signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2819. doi:10.1158/1538-7445.AM2011-2819