The G protein-coupled receptor (GPCR) smoothened (SMO) is a key signaling component of the sonic hedgehog (Hh) pathway and a clinically validated target for cancer treatment. The FDA-approved SMO inhibitors GDC-0449/Vismodegib and LDE225/Sonidegib demonstrated clinical antitumor efficacy. Nevertheless, relatively high percentage of treated patients would eventually develop acquired cross resistance to both drugs. Here, based on published structure and activity of GDC-0449 inhibitor class, we replaced its amide core with benzimidazole which retained bulk of the SMO-targeting activity as measured in our Hh/SMO/Gli1-reporter system. Synthesis and screening of multiple series of benzimidazole derivatives identified HH-1, HH-13, and HH-20 with potent target suppression (IC50: <0.1 μmol/L) in the reporter assays. In NIH3T3 cells stimulated with a secreted Hh (SHH), these inhibitors dose dependently reduced mRNA and protein expression of the endogenous pathway components PTCH-1, Gli1, and cyclin D1 resulting in growth inhibition via G0/G1 arrest. Mechanistically, the SMO-targeted growth inhibition involved downregulation of mTOR signaling inputs and readouts consistent with diminished mTORC1/mTORC2 functions and apoptosis. In mice, as with GDC-0449, orally administered HH inhibitors blocked paracrine activation of stromal Hh pathway in Calu-6 tumor microenvironment and attenuated growth of PTCH+/-/P53-/- medulloblastoma allograft tumors. Furthermore, HH-13 and HH-20 potently targeted the drug-resistant smoothened SMO-D473H (IC50: <0.2 μmol/L) compared to the poor inhibition by GDC-0449 (IC50: >60 μmol/L). These results identify HH-13 and HH-20 as potent inhibitors capable of targeting naïve and drug-resistant Hh/SMO-driven cancers. The current leads may be optimized to improve pharmaceutical property for potential development of new therapy for treatment of Hh pathway-driven cancers.

中文翻译：

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新型平滑抑制剂，可用于靶向天真的和耐药性刺猬途径驱动的癌症。

G蛋白偶联受体（GPCR）平滑化（SMO）是声波刺猬（Hh）途径的关键信号成分，并且是经过临床验证的癌症治疗靶标。FDA批准的SMO抑制剂GDC-0449 / Vismodegib和LDE225 / Sonidegib具有临床抗肿瘤功效。然而，相对较高百分比的治疗患者最终将对两种药物产生后天交叉耐药性。在这里，根据已发布的GDC-0449抑制剂类别的结构和活性，我们用苯并咪唑代替了其酰胺核，苯并咪唑保留了在我们的Hh / SMO / Gli1-reporter系统中测得的大部分SMO靶向活性。合成和筛选了多个苯并咪唑衍生物系列，在报告基因检测中鉴定出具有有效靶点抑制作用的HH-1，HH-13和HH-20（IC50：<0.1μmol/ L）。在被分泌的Hh（SHH）刺激的NIH3T3细胞中，这些抑制剂剂量依赖性地降低了内源性途径组分PTCH-1，Gli1和cyclin D1的mRNA和蛋白质表达，从而导致了通过G0 / G1阻滞而导致的生长抑制。从机制上讲，靶向SMO的生长抑制涉及mTOR信号输入和读数的下调，与mTORC1 / mTORC2功能和凋亡的减少相一致。在小鼠中，与GDC-0449一样，口服HH抑制剂可阻断Calu-6肿瘤微环境中基质Hh途径的旁分泌激活，并减弱同种异体移植肿瘤PTCH + /-/ P53-/-髓母细胞瘤的生长。此外，与GDC-0449的抑制作用较弱（IC50：> 60μmol/ L）相比，HH-13和HH-20有效地靶向了耐药的平滑SMO-D473H（IC50：<0.2μmol/ L）。这些结果表明，HH-13和HH-20是有效的抑制剂，能够靶向天真的和耐药性的Hh / SMO驱动的癌症。可以对当前的引线进行优化，以改善药物特性，从而潜在地开发用于治疗Hh途径驱动的癌症的新疗法。