We report the syntheses and activities of a wide range of thiazolides [viz. 2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis B virus replication, with QSAR analysis of our results. The prototypical thiazolide, nitazoxanide [2-hydroxybenzoyl-N-(5-nitrothiazol-2-yl)amide; NTZ] 1 is a broad spectrum antiinfective agent, effective against anaerobic bacteria, viruses and parasites. By contrast, 2-hydroxybenzoyl-N-(5-chlorothiazol-2-yl)amide 3 is a novel, potent and selective inhibitor of hepatitis B replication (EC50 = 0.33 μm) but is inactive against anaerobes. Several 4′- and 5′-substituted thiazolides show good activity against HBV; by contrast, some related salicyloylanilides show a narrower spectrum of activity. The ADME properties of 3 are similar to 1, viz. the O-acetate is an effective prodrug and the O-aryl glucuronide is a major metabolite. The QSAR study shows a good correlation of observed EC90 s for intracellular virions with thiazolide structural parameters. Finally we discuss the mechanism of action of thiazolides in relation to the present results.

We report the activities of a number of thiazolides [2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis C virus (HCV) genotypes IA and IB, using replicon assays. The structure-activity relationships (SARs) of thiazolides against HCV are less predictable than against hepatitis B virus (HBV), though an electron-withdrawing group at C(5') generally correlates with potency. Among the related salicyloylanilides, the m-fluorophenyl analogue was most promising; niclosamide and close analogues suffered from very low solubility and bioavailability. Nitazoxanide (NTZ) 1 has performed well in clinical trials against HCV. We show here that the 5'-Cl analogue 4 has closely comparable in vitro activity and a good cell safety index. By use of support vector analysis, a quantitative structure-activity relationship (QSAR) model was obtained, showing good predictive models for cell safety. We conclude by updating the mode of action of the thiazolides and explain the candidate selection that has led to compound 4 entering preclinical development.

A number of furanocoumarins isolated from grapefruit juice have been found to inhibit CYP3A4 activity in vitro. In this study, we have designed and synthesised a range of analogues based on bergamottin to investigate the relationship between chemical structure and inhibition of CYP3A4 activity. Studies were performed using human liver microsomes and human intestinal S9 fraction, with testosterone as the marker substrate. With the exception of the coumarin and phenolic furanocoumarin derivatives, which were inactive, the alkyloxy-furanocoumarin analogues were found to inhibit CYP3A4 activity in a dose dependent manner, with observed IC50 values ranging from 0.13 +/- 0.03 to 49.3 +/- 1.9 microM. The unsaturated furan derivatives were found to exhibit time-dependent inhibition, showing a 2-, 4- and 14-fold increase in potency for 6',7'-epoxybergamottin, 6',7'-dihydroxybergamottin and bergamottin, respectively after a preincubation period of ten minutes. Reduction of the furan moiety resulted in an 11-fold decrease in inhibitory potency, suggesting that this functional group is key to the interaction between these compounds and CYP3A4.

Aim:The only small molecule drugs currently available for treatment of influenza A virus (IAV) are M2 ion channel blockers and sialidase inhibitors. The prototype thiazolide, nitazoxanide, has successfully completed Phase III clinical trials against acute uncomplicated influenza.Results: We report the activity of seventeen thiazolide analogs against A/PuertoRico/8/1934(H1N1), a laboratory-adapted strain of the H1N1 subtype of IAV, in a cell culture-based assay. A total of eight analogs showed IC 50 s in the range of 0.14-5.0 μM. Additionally a quantitative structure-property relationship study showed high correlation between experimental and predicted activity based on a molecular descriptor set. Conclusion: A range of thiazolides show useful activity against an H1N1 strain of IAV. Further evaluation of these molecules as potential new small molecule therapies is justified. Graphical abstract:OR 2 A number of thiazolides (R 1 = a 3, 4 or 5-substituent; R 2 = H or CH 3 CO; R 3 = a 4´ -or 5´-substituent) are active with IC 50 = 0.14-5.0 µM against a prototypical H1N1 strain of influenza A virus in MDCK cells; a QSAR regression model was developed, showing good correlation between predicted and measured in vitro activity.Since the prototype nitazoxanide has successfully completed Phase III clinical trials against acute uncomplicated influenza, this molecule series has considerable potential for future development.