Jeong In Yun

Small molecule inhibitors of the hedgehog signaling pathway for the treatment of cancer.

Over the past decade, the Hedgehog signaling pathway has attracted considerable interest because the pathway plays important roles in the tumorigenesis of several types of cancer as well as developmental processes. It has also been observed that Hedgehog signaling regulates the proliferation and self-renewal of cancer stem cells. A great number of Hedgehog pathway inhibitors have been discovered through small molecule screens and subsequent medicinal chemistry efforts. Among the inhibitors, several Smo antagonists have reached the clinical trial phase. It has been proved that the inhibition of Hedgehog signaling with Smo antagonists is beneficial to cancer patients with basal cell carcinoma and medulloblastoma. In this review, we provide an overview of Hedgehog pathway inhibitors with focusing on the preclinical and/or clinical efficacy and molecular mechanisms of these inhibitors.

KRC-408, a novel c-Met inhibitor, suppresses cell proliferation and angiogenesis of gastric cancer

Among many cancer therapeutic targets, c-Met receptor tyrosine kinase has recently given particular attention. This kinase and its ligand, hepatocyte growth factor (HGF), play a central role in cell proliferation and the survival of several human cancers. Thus, we developed KRC-408 as a novel c-Met inhibitor and investigated its anti-cancer effects on human gastric cancer. KRC-408 inhibited the phosphorylation of c-Met and its constitutive downstream effectors such as phosphatidylinositol 3-kinase (PI3K), Akt, Mek, and Erk. This compound was found to exert anti-cancer effects stronger than those of 5-fluorouracil (5-FU) on gastric cancer cells, especially cell lines that overexpressed c-Met. Interestingly, cytotoxicity of KRC-408 was lower than that of 5-FU in normal gastric cells. Apoptosis induced by KRC-408 was accompanied by increased levels of cleaved caspase-3 and PARP as well as DNA condensation and fragmentation. Flow cytometry analysis showed an accumulation of gastric cancer cells in the G2/M phase with concomitant loss of cells in the S phase following treatment with this drug. In the angiogenesis studies, KRC-408 inhibited tube formation and migration of human umbilical vein endothelial cells (HUVECs), and suppressed microvessel sprouting from rat aortic rings ex vivo along with blood vessel formation in a Matrigel plug assay in mice. Results of an in vivo mouse xenograft experiment showed that the administration of KRC-408 significantly delayed tumor growth in a dose-dependent manner, and suppressed Akt and Erk phosphorylation as well CD34 expression in tumor tissues. These findings indicate that KCR-408 may exert anti-tumor effects by directly affecting tumor cell growth or survival via the c-Met receptor tyrosine kinase pathway. We therefore suggest that KRC-408 is a novel therapeutic candidate effective against gastric cancers that overexpress c-Met.

Novel bis-ortho-alkoxy-para-piperazinesubstituted-2,4-dianilinopyrimidines (KRCA-0008) as potent and selective ALK inhibitors for anticancer treatment

The synthesis of bis-ortho-alkoxy-para-piperazinesubstituted-2,4-dianilinopyrimidines is described and their structure-activity-relationship to anaplastic lymphoma kinase (ALK) is presented. KRCA-0008 is selective and potent to ALK and Ack1, and displays drug-like properties without hERG liability. KRCA-0008 demonstrates in vivo efficacy comparable to Crizotinib in xenograft mice model.

Design and synthesis of triazolopyridazines substituted with methylisoquinolinone as selective c-Met kinase inhibitors

A series of triazolopyridazines substituted with methylisoquinolinone were designed and synthesized. Some of the triazolopyridazines strongly inhibited c-Met kinase and showed good anti-proliferative activity against a panel of c-Met-amplified gastric cancer cell lines (MKN-45, SNU-5 and Hs746T).

Discovery of novel tetrahydroisoquinoline-containing pyrimidines as ALK inhibitors.

Exploration of the two-position side chain of pyrimidine in LDK378 with tetrahydroisoquinolines (THIQs) led to discovery of 8 and 17 as highly potent ALK inhibitors. THIQs 8 and 17 showed encouraging in vitro and in vivo xenograft efficacies, comparable with those of LDK378. Although THIQ analogs (8a-o and 17a-i) prepared were not as active as their parent compounds, both 8 and 17 have significant inhibitory activities against various ALK mutant enzymes including G1202R, indicating that this series of compounds could be further optimized as useful ALK inhibitors overcoming the resistance issues found from crizotinib and LDK378.

Stereoselective construction of 2,6-cis-disubstituted tetrahydropyrans via intramolecular amide enolate alkylation: total synthesis of (-)-centrolobine.

A highly stereoselective construction of 2,6-cis-disubstituted tetrahydropyrans was achieved by using an intramolecular amide enolate alkylation with KHMDS. The efficiency and practicality of this methodology was successfully demonstrated in the total synthesis of (-)-centrolobine (1).

ALK inhibitors of bis- ortho -alkoxy- para -piperazinesubstituted-pyrimidines and -triazines for cancer treatment

Syntheses of various bis-ortho-alkoxy-para-piperazineanilino-pyrimidines and -triazines of KRCA-0008 analogs are described and their structure–activity-relationship to anaplastic lymphoma kinase (ALK) is discussed. 5-trifluoromethyl-2,4-pyrimidine analog (2) seems to be most potent in both biochemical and cellular assay in this study, however it shows inferior mice xenograft activity to Crizotinib presumably due to its sub-optimal PK parameters. 4,6-disubstituted pyrimidine and 2,4-disubstituted triazine derivatives of KRCA-0008 are less potent or inactive to ALK wt., and this observation is explained with their molecular modeling compared to KRCA-0008.

Novel 2,4-dianilino-5-fluoropyrimidine derivatives possessing ALK inhibitory activities

A new series of 2,4-dianilino-5-fluoropyrimidine derivatives were designed and synthesized and their anaplastic lymphoma kinase (ALK) inhibitory activities were evaluated by biochemical and cell-based assays in order to discover a new ALK inhibitor. Most compounds synthesized showed good inhibitory activities against ALK and good cytotoxic activities in H3122 cell line. The best compound 6f showed good activity against wild-type ALK along with crizotinib-resistant mutant ALK, and it showed 6 times better activity in cell-based assay than crizotinib. Some SAR studies were performed by the comparisons of the activities between 6 and the designed-synthesized compounds.