Ho Shin Kim

2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides as potent transient receptor potential vanilloid 1 (TRPV1) antagonists: structure-activity relationships of 2-amino derivatives in the N-(6-trifluoromethylpyridin-3-ylmethyl) C-region.

A series of N-(2-amino-6-trifluoromethylpyridin-3-ylmethyl)-2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides were designed combining previously identified pharmacophoric elements and evaluated as hTRPV1 antagonists. The SAR analysis indicated that specific hydrophobic interactions of the 2-amino substituents in the C-region of the ligand were critical for high hTRPV1 binding potency. In particular, compound 49S was an excellent TRPV1 antagonist (K(i(CAP)) = 0.2 nM; IC(50(pH)) = 6.3 nM) and was thus approximately 100- and 20-fold more potent, respectively, than the parent compounds 2 and 3 for capsaicin antagonism. Furthermore, it demonstrated strong analgesic activity in the rat neuropathic model superior to 2 with almost no side effects. Compound 49S antagonized capsaicin induced hypothermia in mice but showed TRPV1-related hyperthermia. The basis for the high potency of 49S compared to 2 is suggested by docking analysis with our hTRPV1 homology model in which the 4-methylpiperidinyl group in the C-region of 49S made additional hydrophobic interactions with the hydrophobic region.

2-(3-Fluoro-4-methylsulfonylaminophenyl)propanamides as potent TRPV1 antagonists: structure activity relationships of the 2-oxy pyridine C-region.

The structure activity relationships of 2-oxy pyridine derivatives in the C-region of N-(6-trifluoromethyl-pyridin-3-ylmethyl) 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides as hTRPV1 antagonists were investigated. The analysis indicated that the lipophilicity of the 2-oxy substituents was critical for potent antagonism and 4 or 5 carbons appeared to be optimal for activity. Multiple compounds proved to have comparable activity to 1, which had been reported as the most potent antagonist for capsaicin activity among the previous series of compounds. Further analysis of compounds 22 (2-isobutyloxy) and 53 (2-benzyloxy) in the formalin test in mice demonstrated strong analgesic activity with full efficacy. Docking analysis of 53S using our hTRPV1 homology model indicated that the A- and B-region 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamide made important hydrophobic and hydrogen bonding interactions with Tyr511 and that the C-region 6-trifluoromethyl and 2-benzyloxy groups of pyridine occupied the two hydrophobic binding pockets, respectively.

2-Alkyl/alkenyl substituted pyridine C-region analogues of 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides as highly potent TRPV1 antagonists

A series of 2-aryl pyridine C-region derivatives of 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides were investigated as hTRPV1 antagonists. Multiple compounds showed highly potent TRPV1 antagonism toward capsaicin comparable to previous lead 7. Among them, compound 9 demonstrated anti-allodynia in a mouse neuropathic pain model and blocked capsaicin-induced hypothermia in a dose-dependent manner. Docking analysis of 9 with our hTRPV1 homology model provided insight into its specific binding mode.

TRPV1 antagonist with high analgesic efficacy: 2-Thio pyridine C-region analogues of 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides

A series of 2-thio pyridine C-region analogues of 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides were investigated as hTRPV1 antagonists. Among them, compound 24S showed stereospecific and excellent TRPV1 antagonism of capsaicin-induced activation. Further, it demonstrated strong anti-allodynic in a rat neuropathic pain model. Consistent with its action in vitro being through TRPV1, compound 24S blocked capsaicin-induced hypothermia in mice. Docking analysis of 24S with our hTRPV1 homology model was performed to identify its binding mode.

α-Substituted 2-(3-fluoro-4-methylsulfonamidophenyl)acetamides as potent TRPV1 antagonists

A series of α-substituted acetamide derivatives of previously reported 2-(3-fluoro-4-methylsulfonamidophenyl)propanamide leads (1, 2) were investigated for antagonism of hTRPV1 activation by capsaicin. Compound 34, which possesses an α-m-tolyl substituent, showed highly potent and selective antagonism of capsaicin with Ki(CAP)=0.1 nM. It thus reflected a 3-fold improvement in potency over parent 1. Docking analysis using our homology model indicated that the high potency of 34 might be attributed to a specific hydrophobic interaction of the m-tolyl group with the receptor.

Synthesis and biological evaluation of C-ring truncated deguelin derivatives as heat shock protein 90 (HSP90) inhibitors

Based on the lead compound L-80 (compound 2), a potent heat shock protein 90 (HSP90) inhibitor, a series of C-ring truncated deguelin analogs were designed, synthesized and evaluated for Hypoxia Inducible Factor-1α (HIF-1α) inhibition as a primary screening method. Their structure-activity relationship was investigated in a systematic manner by varying the A/B ring, linker and D/E ring, respectively. Among the synthesized inhibitors, compound 5 exhibited potent HIF-1α inhibition in a dose-dependent manner and significant antitumor activity in human non-small cell lung carcinoma (H1299), with better activities than L-80. It also inhibited in vitro hypoxia-mediated angiogenic processes in human retinal microvascular endothelial cells (HRMEC). The docking study of 5 showed a similar binding mode as L-80: it occupied the C-terminal ATP-binding pocket of HSP90, indicating that the anticancer and antiangiogenic activities of 5 were derived from HIF-1α destabilization by inhibiting the C-terminal ATP-binding site of hHSP90.

α-Methylated simplified resiniferatoxin (sRTX) thiourea analogues as potent and stereospecific TRPV1 antagonists.

A series of α-methylated analogues of the potent sRTX thiourea antagonists were investigated as rTRPV1 ligands in order to examine the effect of α-methylation on receptor activity. The SAR analysis indicated that activity was stereospecific with the (R)-configuration of the newly formed chiral center providing high binding affinity and potent antagonism while the configuration of the C-region was not significant.

2-(4-Methylsulfonylaminophenyl) propanamide TRPV1 antagonists: Structure-activity relationships in the B and C-regions.

On the basis of the previous lead N-4-t-butylbenzyl 2-(3-fluoro-4-methylsulfonylaminophenyl) propanamide (3) as a potent TRPV1 antagonist, structure-activity relationships for the B (propanamide part) and C-region (4-t-butylbenzyl part) have been investigated for rTRPV1 in CHO cells. The B-region was modified with dimethyl, cyclopropyl and reverse amides and then the C-region was replaced with 4-substituted phenyl, aryl alkyl and diaryl alkyl derivatives. Among them, compound 50 showed high binding affinity with K(i)=21.5nM, which was twofold more potent than 3 and compound 54 exhibited potent antagonism with K(i(ant))=8.0nM comparable to 3.

The SAR analysis of TRPV1 agonists with the α-methylated B-region

A series of TRPV1 agonists with amide, reverse amide, and thiourea groups in the B-region and their corresponding α-methylated analogues were investigated. Whereas the α-methylation of the amide B-region enhanced the binding affinities and potencies as agonists, that of the reverse amide and thiourea led to a reduction in receptor affinity. The analysis indicated that proper hydrogen bonding as well as steric effects in the B-region are critical for receptor binding.