Design, synthesis and evaluation of novel indirubin-based N-hydroxybenzamides, N-hydroxypropenamides and N-hydroxyheptanamides as histone deacetylase inhibitors and antitumor agents.

Several novel indirubin-based N-hydroxybenzamides, N-hydropropenamides and N-hydroxyheptanamides (4a-h, 7a-h, 10a-h) were designed using a fragment-based approach with structural features extracted from several previously reported HDAC inhibitors, such as SAHA (vorinostat), MGCD0103 (mocetinostat), nexturastat A and PXD-101 (belinostat). The biological results reveal that our compounds showed excellent cytotoxicity toward three common human cancer cell lines (SW620, PC-3 and NCI-H23) with IC50 values ranging from 0.09 to 0.007 µM. The cytotoxicity of the compounds was equipotent or even up to 10-times more potent than adriamycin and up to 205-times more potent than SAHA. Among the series of N-hydroxypropenamides, compounds 10a-d were the most potent HDAC inhibitors as well as cytotoxicity toward the cell lines tested. In addition, the strong inhibitory activites toward HDAC of our compounds were observed with IC50 values of below-micromolar range. Especially, compound 4a inhibited HDAC6 with an IC50 value of 29-fold lower than that against HDAC2 isoform. Representative compounds 4a and 7a were found to significantly arrest SW620 cells at G0/G1 phase. Compounds 7a and 10a were found to strongly induce apoptosis in SW620 cells. Docking studies revealed some important features affecting the selectivity against HDAC6 isoform. The results clearly demonstrate the potential of the indirubin-hydroxamic acid hybrids and these compounds should be very promising for further development.

Quinazoline-Based Hydroxamic Acids: Design, Synthesis, and Evaluation of Histone Deacetylase Inhibitory Effects and Cytotoxicity.

In our search for novel histone deacetylases inhibitors, we have designed and synthesized a series of novel hydroxamic acids and N-hydroxybenzamides incorporating quinazoline heterocycles (4a - 4i, 6a - 6i). Bioevaluation showed that these quinazoline-based hydroxamic acids and N-hydroxybenzamides were potently cytotoxic against three human cancer cell lines (SW620, colon; PC-3, prostate; NCI-H23, lung). In term of cytotoxicity, several compounds, e.g., 4g, 4c, 4g - 4i, 6c, and 6h, displayed from 5- up to 10-fold higher potency than SAHA (suberoylanilidehydroxamic acid, vorinostat). The compounds were also generally comparable to SAHA in inhibiting HDACs with IC50 values in sub-micromolar range. Some compounds, e.g., 4g, 6c, 6e, and 6h, were even more potent HDAC inhibitors compared to SAHA in HeLa extract assay. Docking studies demonstrated that the compounds tightly bound to HDAC2 at the active binding site with binding affinities higher than that of SAHA. Detailed investigation on the estimation of absorption, distribution, metabolism, excretion, and toxicity (ADMET) suggested that compounds 4g, 6c, and 6g, while showing potent HDAC2 inhibitory activity and cytotoxicity, also potentially displayed ADMET characteristics desirable to be expected as promising anticancer drug candidates.

Design, synthesis and evaluation of novel N-hydroxybenzamides/N-hydroxypropenamides incorporating quinazolin-4(3H)-ones as histone deacetylase inhibitors and antitumor agents.

In our search for novel small molecules targeting histone deacetylases, we have designed and synthesized several series of novel N-hydroxybenzamides/N-hydroxypropenamides incorporating quinazolin-4(3H)-ones (4a-h, 8a-d, 10a-d). Biological evaluation showed that these hydroxamic acids were generally cytotoxic against three human cancer cell lines (SW620, colon; PC-3, prostate; NCI-H23, lung cancer). It was found that the N-hydroxypropenamides (10a-d) were the most potent, both in term of HDAC inhibition and cytotoxicity. Several compounds, e.g. 4e, 8b-c, and 10a-c, displayed up to 4-fold more potent than SAHA (suberoylanilide hydroxamic acid, vorinostat) in term of cytotoxicity. These compounds also comparably inhibited HDACs with IC50 values in sub-micromolar range. Docking experiments on HDAC2 isozyme revealed some important features contributing to the inhibitory activity of synthesized compounds, especially for propenamide analogues. Importantly, the free binding energy computed was found to have high quantitative correlation (R2 ∼ 95%) with experimental results.

5-aryl-1,3,4-thiadiazole-based hydroxamic acids as histone deacetylase inhibitors and antitumor agents: synthesis, bioevaluation and docking study.

The search for newer histone deacetylase (HDAC) inhibitors has attracted a great deal of interest of medicinal chemists worldwide, especially after the first HDAC inhibitor (Zolinza(®), widely known as SAHA or Suberoylanilide hydroxamic acid) was approved by the FDA for the treatment of Tcell lymphoma in 2006. As a continuity of our ongoing research in this area, we designed and synthesized a series of 5-aryl-1,3,4-thiadiazole-based hydroxamic acids as analogues of SAHA and evaluated their biological activities. Most of the compounds in this series, e.g. compounds with 5-aryl moiety being 2- furfuryl (5a), 5-bromofuran-2-yl (5b), 5-methylfuran-2-yl (5c), thiophen-2-yl (5d), 5-methylthiophen-2-yl (5f) and pyridyl (5g-i), were found to have potent anticancer cytotoxicity with IC50 values of generally 5- to 10-fold lower than that of SAHA in 4 human cancer cell lines assayed. Those compounds with potent cytotoxicity were also found to have strong HDAC inhibition effects. Docking studies revealed that compounds 5a and 5d displayed high affinities towards HDAC2 and 8.

Synthesis, bioevaluation and docking study of 5-substitutedphenyl-1,3,4-thiadiazole-based hydroxamic acids as histone deacetylase inhibitors and antitumor agents.

Since the first histone deacetylase (HDAC) inhibitor (Zolinza®, widely known as suberoylanilide hydroxamic acid; SAHA) was approved by the Food and Drug Administration for the treatment of T-cell lymphoma in 2006, the search for newer HDAC inhibitors has attracted a great deal of interest of medicinal chemists worldwide. As a continuity of our ongoing research in this area, we designed and synthesized a series of 5-substitutedphenyl-1,3,4-thiadiazole-based hydroxamic acids as analogues of SAHA and evaluated their biological activities. A number of compounds in this series, for example, N(1)-hydroxy-N(8)-(5-(2-chlorophenyl)-1,3,4-thiadiazol-2-yl)octandiamide (5b), N(1)-hydroxy-N(8)-(5-(3-chlorophenyl-1,3,4-thiadiazol-2-yl)octandiamide (5c) and N(1)-hydroxy-N(8)-(5-(4-chlorophenyl)-1,3,4-thiadiazol-2-yl)octandiamide (5d), were found to possess potent anticancer cytotoxicity and HDAC inhibition effects. Compounds 5b-d were generally two- to five-fold more potent in terms of cytotoxicity compared to SAHA against five cancer cell lines tested. Docking studies revealed that these hydroxamic acid displayed higher affinities than SAHA toward HDAC8.

Novel isatin-based hydroxamic acids as histone deacetylase inhibitors and antitumor agents.

Accumulated clinical studies have demonstrated that histone deacetylase (HDAC) inhibitors show great potential for the treatment of cancer. SAHA (Vorinostat, trade name Zolinza) was approved by the FDA in 2006 for the treatment of the cutaneous manifestations of cutaneous T-cell lymphoma. As a continuity of our ongoing effort to identify novel small molecules targeting these important enzymes, we designed and synthesized two series of isatin-3'-oxime- and isatin-3'-methoxime-based hydroxamic acids (3a-g and 6a-g) as analogues of SAHA. Generally in both series it was found that, compounds bearing no substituent or with 5'-F, 5'-Cl, 7'-Cl substitutents on the isatin moiety exhibited good inhibition against histone-H3 and histone-H4 deacetylation at the concentrations of 1 µM, as evaluated by Western Blot assay. The compounds also displayed potent cytotoxicity against five cancer cell lines with IC50 values of as low as 0.08 µM, more than 45-fold lower than that of SAHA. Docking study performed with selected compounds 3a and 6a revealed that these compounds bound to HDAC8 with higher affinities compared to SAHA. Compounds 3a and 6a also bound to HDAC2 at the binding site with high binding affinity. These findings should encourage further elaboration with the isatin moiety to produce more potent HDAC inhibitors with potential anticancer activity.

2-Aryl- and 2-amido-benzothiazoles as multifunctional vasodilators on rat artery preparations.

The neuroprotective agent riluzole [2-amino-6-(trifluoromethoxy)benzothiazole] has been shown to antagonize neuronal high-voltage activated Ca(2+) currents. In the search for novel scaffolds leading to potential antihypertensive agents, a series of 2-aryl- and 2-amido-benzothiazoles (HUP) were assessed for their vasorelaxing property on rat aorta rings and for their L-type Ba(2+) currents [I(Ba(L))] blocking activity on single myocytes isolated from the rat tail artery. HUP5 and HUP30, the most potent of the series, inhibited phenylephrine-induced contraction with IC50 values in the range 3-6 µM. The presence of endothelium did not modify their spasmolytic activity. Both HUP5 and HUP30 increased tissue levels of cGMP and shifted to the left the concentration-response curve to sodium nitroprusside. In rings precontracted by phenylephrine, tetraethylammonium or 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) shifted to the right the concentration-relaxation curves of HUP5 and HUP30. The antispasmodic effect of HUP5 and HUP30 was more marked on rings stimulated with 25/30 mM than with 60 mM K(+). HUP5 and HUP30 antagonized both extracellular Ca(2+) influx and Ca(2+) mobilization from intracellular stores in response to phenylephrine: this effect was not modified by the presence of ODQ. I(Ba(L)) was partly inhibited by HUP5 and blocked by HUP30 in a concentration-dependent as well as ODQ-independent manner. In conclusion, HUP5 and HUP30 are vasorelaxing agents that stimulate soluble guanylyl cyclase, activate K(+) channels, and block extracellular Ca(2+) influx. The present benzothiazole derivatives form a novel class of multifunctional vasodilators which may give rise to effective antihypertensive agents.

New benzothiazole/thiazole-containing hydroxamic acids as potent histone deacetylase inhibitors and antitumor agents.

Results from clinical studies have demonstrated that inhibitors of histone deacetylase (HDAC) enzymes possess promise for the treatment of several types of cancer. Zolinza(®) (widely known as SAHA) has been approved by the FDA for the treatment of T-cell lymphoma. As a continuity of our ongoing research to find novel small molecules to target these important enzymes, we synthesized a series of benzothiazole-containing analogues of SAHA and found several compounds with very potent anticancer cytotoxicity. In this study, three more compounds of this type, including N(1)-(6-chlorobenzo[d]thiazol-2-yl)-N(8)-hydroxyoctanediamide (3a), N(1)-[6-(trifluoromethyl)benzo[d]thiazol-2-yl]-N(8)-hydroxyoctanediamide (3b) and N(1)-(thiazol-2-yl)-N(8)-hydroxyoctanediamide (6) were synthesized and evaluated for HDAC inhibition and cytotoxic activities. All three compounds showed very potent HDAC inhibitory effects. Docking revealed that both two compounds 3a, 3b showed higher affinities towards HDAC(8) compared to SAHA. In vitro, compound 3a exhibited cytotoxicity equipotent to SAHA against five human cancer cell lines. In term of in vivo activity, compound 3a demonstrated equivalent efficacy to SAHA in mouse xenograft model.

Synthesis and biological evaluation of a series of 2-(substitutedphenyl)benzothiazoles.

A series of 2-phenylbenzothiazoles has been synthesized either by i) condensation of different aromatic aldehydes with 2-aminothiophenol or ii) condensation of N-(2-chlorophenyl)benzothioamides in KOH catalyzed by potassium fericyanide. The structures of synthesized compounds were confirmed by IR, MS, and (1)H-NMR. The results of biological activity screening showed that six compounds including 2-phenylbenzothiazol (1a), 2-(2-chlorophenyl)benzothiazole (1b), 2-(3-chlorophenyl)benzothiazole (1c), 2-(4-hydroxyphenyl)benzothiazole (1e), 2-(4-dimethylaminophenyl)benzothiazole (1h) and 2-(2,3,4-trimethoxyphenyl)benzothiazole (1i) exhibited significant antibacterial activities; two compounds (1a, 1e) exhibited antifungal activities. Especially, 1e showed considerable antimicrobial activity against both A. niger and F. oxysporum. The brominated derivative of 1e displayed extended spectrum against all four bacterial strains tested with lower MIC values. In vitro cytotoxicity of the synthesized compounds was evaluated on three cancer cell lines (A549, HT1080, MCF7-MDR). The results indicated that three compounds (1e, 1g, 1i) exhibited significant cytotoxic activity on A549 and MCF7-ADR cells (IC(50), 10.07-13.21 µg/ml). Brominated and nitrated derivatives (1k, 1l, respectively) of 1e exhibited even more potent cytotoxicity.

Synthesis and Biological Evaluation of A Series of (Benzo[d]thiazol-2-yl)cyclohexanecarboxamides and (Benzo[d]thiazol-2-yl)cyclohexanecarbothioamides.

A series of benzothiazole derivatives including N-(benzo[d]thiazol-2-yl)cyclohexanecarboxamides (2a-g) and N-(benzo[d]thiazol-2-yl)cyclohexancarbothioamides (3b-d) have been synthesized and evaluated for cytotoxic and antimicrobial activities. Two compounds including N-(6-ethoxybenzo[d]thiazol-2-yl)cyclohexanecarboxamide (2c) and N-(6-ethoxybenzo[d]thiazol-2-yl)cyclohexanecarbothiamide (3c) demonstrated significant cytotoxicity against three cancer cell lines (A549, MCF7-MDR and HT1080) while most of compounds exhibited moderate inhibitory effects on the growth of Staphyllococcus aureus and some other fungi.