In vitro antifungal activity of 2-(4-substituted phenyl)-3(2H)-isothiazolones.

The in vitro antifungal activity of several N2-phenyl-3(2H)-isothiazolones substituted at C4 of the phenyl moiety with heterocyclic nucleus or groups of different physico-chemical properties against four human pathogenic fungi was determined by broth macrodilution method; results were compared with those obtained with itraconazole and ketoconazole. These isothiazolones showed moderate to high activity against some or all tested strains and in comparison with the reference drugs, 5-chloro-2-(4-nitrophenyl)isothiazol-3-one (1g), 5-chloro-2-phenylisothiazol-3-one (1c), 4-[4-(5-chloro-3-oxo-3H-isothiazol-2-yl)phenyl]-1,4-dihydrotriazol-5-one (1s) and 2-(4-nitrophenyl)isothiazol-3-one (2g) against Aspergillus niger, 5-chloro-2-(4-nitrophenyl)isothiazol-3-one (1g) and 4-[4-(5-chloro-3-oxo-3H-isothiazol-2-yl)phenyl]piperazine-1-carboxamide (1q) against Trichophyton mentagrophytes had comparable activity, compounds 1g and 2g showing higher activity against Microsporum canis. Antifungal activity was favored by the presence of chlorine at C5 of the isothiazolone and/or the presence of nitro group or heterocyclic nucleus at C4 of the phenyl ring and proper hydrophilicity of the molecule.

Modulatory effect of cAMP on fungal ergosterol level and inhibitory activity of azole drugs.

The functions and biosynthesis of sterols have been effective targets for fungal control in different areas, including pharmaceutical and agricultural applications. Fungi are among the organisms that synthesize sterols, principally ergosterol. In this paper, the effect of dibutyryl-cAMP (db-cAMP) on ergosterol level and the interaction of drugs that would change the concentration of cAMP with antifungal drugs have been investigated. Sterols were extracted from Candida albicans, and ergosterol was measured using the gas chromatography method. The interaction of different agents was measured by the broth dilution method. It was found that phosphodiesterase inhibitors reverse the inhibitory activity of azole antifungal drugs. Evaluating the ergosterol level of C. albicans incubated with db-cAMP revealed that it increased ergosterol level. Further experiments provided evidence attributing the observed interaction between azoles and phosphodiesterase inhibitors to the relationship between ergosterol and cAMP. The possible significance of this interaction includes potentiation of antifungal activity of drugs by manipulating the cAMP level.

Synthesis and in vitro antifungal and cytotoxicity evaluation of substituted 4,5-dihydronaphtho[1,2-d][1,2,3]thia(or selena)diazoles.

Unsubstituted 4,5-dihydronaphtho[1,2-d][1,2,3]thia (or selena)diazoles (2a, 2b), prepared from the semicarbazone (1a), were nitrated using fuming nitric acid at 0 degrees C to yield various mono-nitrated dihydronaphthalenes (3a-3e). Related sulfamoyl derivatives (4a, 4b) were prepared using chlorosulfonic acid, followed by the addition of ammonia solution. Synthesis of 6,9-dimethoxy-4,5-dihydronaphtho[1,2-d][1,2,3]thiadiazole derivative (2c) was performed using 5,8-dimethoxy-alpha-tetralone semicarbazone (1b) and thionylchloride at low temperature. At 10 ppm concentration, all compounds showed low toxicity (higher than 80% survival) on brine shrimps, while at 100 ppm concentration compounds 2d, 3d, and 4b exhibited toxicity (less than 60% survival). Compounds 3a, 3e, and especially 4a showed significant antifungal activity against Cryptococcus neoformans. Compound 4a, while being the most active antifungal agent in this series, possessed low toxicity.

In vitro and in vivo activities of syn2836, syn2869, syn2903, and syn2921: new series of triazole antifungal agents.

The in vitro and in vivo activities of four azole compounds belonging to a new series of 2(2,4-difluorophenyl)-3-(4-substituted piperazin-1-yl)-1-(1,2,4-triazol-1-yl) butanol antifungal agents is described. The compounds were selected from a library of azole compounds synthesized by our group. The in vitro activities of Syn2869, Syn2836, Syn2903, and Syn2921 against a panel of over 240 recently collected clinical isolates of yeast and molds were determined, and the results were compared with those obtained with fluconazole (FLC), itraconazole (ITC), and amphotericin B (AMB). The MICs at which 90% of the isolates were inhibited (MIC(90)s) for the four test compounds for strains of Candida spp. ranged from <0.048 to 0.78 microg/ml. All compounds were also active against FLC-resistant Candida albicans and other Candida sp. strains. Moreover, MIC(90)s for strains of Cryptococcus neoformans, Aspergillus spp., Trichophyton spp., and Microsporum spp. were also low and ranged from <0.048 to 0.39 microg/ml. The test compounds produced a fungistatic pattern during the time-kill kinetic studies. In vivo studies indicated that all four test compounds have good efficacies against C. albicans in a murine systemic infection model and significantly improved the survival rates of the infected mice. The results for Syn2903 were similar to those for FLC, while the other compounds were slightly less effective but had ranges of activities similar to the range of activity of ITC. The compounds were also evaluated against an Aspergillus fumigatus systemic infection. Syn2903 was also superior to ITC, whereas the efficacy data for the other compounds were similar to those for ITC. It was concluded from the data generated for this new series of azole compounds in the studies described above that further pharmacokinetic and toxicologic evaluations are warranted prior to selection of a candidate compound for preclinical testing.

Synthesis and in vitro antifungal and cytotoxicity evaluation of thiazolo-4H-1,2,4-triazoles and 1,2,3-thiadiazolo-4H-1,2,4-triazoles.

The increasing clinical importance of drug-resistant fungal pathogens has lent additional urgency to microbiological and antifungal research. Various thiazolo(or 1,2,3-thiadiazolo)thiosemicarbazides (2a-2e), 3-thiono-1,4-dihydrotriazolothiazoles-(or 1,2,3-thiadiazoles) (3a-3e), their related substituted thio-4H-1,2,4-triazoles (4a-4p) and sulfones (5a-5o) were synthesized. Most of the compounds tested for antifungal activity exhibited significant effects against Cryptococcus neoofrmans and Sacchromyces cerevisiae at MIC ranges of 0.53 to 12.5 micrograms/mL, whereas their activities were moderate against Candida albicans and weak against Aspergillus fumigatus. At 10 ppm concentration, all compounds showed low toxicity on brine shrimps (higher than 80% survival), except compounds 4c and 2c. At 100 ppm concentration most of the compounds showed toxicity except compounds 2b, 2e, 3c, 3d, 3e, and 4e. Compounds 4b, 4c, and 4h showed in vitro cytotoxicity against Kbalb cell lines and compounds 4c and 4g against 143B cell lines at 0.1 mM concentration.

Evaluation of methylthio-, methylsulfinyl-, and methylsulfonyl-analogs of alkanes and alkanoic acids as cardiac inotropic and antifungal agents.

A group of alkane and alkanoic acid compounds of general formula MeS(O)m(CH2)nR [m = 0-2; n = 1, 5, 13; R = Me, CO2H(Na)] were synthesized for evaluation as cardiac inotropic and antifungal agents. Inotropic activity was determined as the ability of the test compound to modulate in vitro guinea pig atrium contractility. The oxidation state of the S-atom was an important determinant of inotropic modulation since the thio (m = 0) analogs exhibited a positive inotropic effect. In contrast, the sulfinyl (m = 1) and sulfonyl (m = 2) analogs exhibited a negative inotropic effect. A pentyl spacer (n = 5) provided the largest positive or negative inotropic effect. The relative positive, and negative, inotropic potency orders with respect to the R-substituent were Me > or = CO2H, and CO2Na > or = Me, respectively. The most potent positive inotrope MeS(CH2)5Me (EC50 = 4.49 x 10(-6) M) could serve as a useful lead-compound for the design of a new class of positive inotropic agents. In a broad spectrum antifungal screen, the minimal inhibitory concentration (MIC) range for the five most active compounds was MeSO2(CH2)5Me (0.46-1.83 mM), MeS(CH2)13Me (0.31-1.23 mM), MeSO(CH2)13Me (< 0.009-1.87 mM), MeSO2(CH2)13Me (0.27-1.09 mM), and MeS(CH2)13CO2H (0.27-1.09 mM), relative to the reference drug Ampotericin B (< 0.0002-0.002 mM). The most active antifungal agent MeSO(CH2)13Me was selective against C. guillermondi, C. neoformans, S. cerevisiae, and A. fumigatus (strain TIMM 1776).

High-performance liquid chromatographic assay for the determination of novel triazole antifungal agents in tissue. Application to tissue distribution studies.

A simple and rugged reversed-phase high-performance liquid chromatographic method with ultraviolet absorbance detection at 263 nm was developed and validated for the analysis of novel triazole antifungal agents SYN-2869 and its derivatives in tissues. The method involved homogenization with 0.01 M phosphate buffer (pH 7.8) for lung, brain and spleen tissues. The liver and kidneys were homogenized with acetonitrile:acetone (1:1). The plasma proteins were precipitated with ice-cold acetonitrile and supernatent was evaporated to dryness. The reconstituted samples were injected onto an HPLC system. SYN-2869 was separated from the matrix components on a symmetry C(18) column using a aqueous mobile phase of acetonitrile and water with a flow rate of 1 mL/min. A step gradient of 40-80% acetonitrile eluted SYN-2869 and the internal standard (SYN-2506). The linear range was 0.5-10 microgram/g (r(2) > 0.99). The limit of quantitation was 0.5 microgram/g. The inter-day precision and accuracy for SYN 2869 standard concentration were from 2.6 to 7.4% and from -1.56 to +3.29%, respectively. The method was applied to tissue samples collected from single intravenous administration to mice to evaluate the distribution of these novel antifungal agents to different tissues.

Interspecies comparison of pharmacokinetics of the novel triazole antifungal agent SYN-2869 and its derivatives.

The pharmacokinetics and distribution in tissue of several novel triazole antifungal agents were studied in different animal species in order to select an appropriate lead compound. The purpose of the study was also to determine species differences in pharmacokinetics for SYN azoles to select the most appropriate species for secondary efficacy and toxicological evaluation of the selected compound. SYN-2836, SYN-2869, SYN-2903, and SYN-2921 were rapidly absorbed into the systemic circulation and reached maximum concentrations (C(max)s) of 7.31 +/- 2.53, 6.29 +/- 0.85, 6.16 +/- 0.39, and 3.41 +/- 0.34 microg/ml, respectively, in BALB/c mice after administration of an oral dose of 50 mg/kg of body weight, with bioavailability being greater than 45% in all mice. The areas under the concentration-time curve from time zero to infinity (AUC(0-infinity)s) after administration of a single intravenous dose of 20 mg/kg to mice varied between 25.0 and 63.6 microg. h/ml. The half-life was in the range of 4.5 to 6 h. In Sprague-Dawley rats there was no significant difference in AUC(0-infinity) after administration of a single intravenous dose of 20 mg/kg, but on oral administration, the bioavailability of SYN-2836 was extremely low, while that of SYN-2869 was only 14.7%. In New Zealand White rabbits the C(max) and the time to reach C(max) for SYN-2836 and SYN-2869 after administration of a single oral dose of 50 mg/kg were similar. There were significant differences in AUC(0-infinity) and half-life between SYN-2836 and SYN-2869. On the other hand, in beagle dogs the C(max) and AUC(0-infinity) of SYN-2836 after administration of a single oral dose of 30 mg/kg were 4.82 +/- 1.54 microg/ml and 41.8 +/- 15.7 microg. h/ml, respectively, which were threefold higher than those of SYN-2869. The concentrations of the SYN compounds in tissue indicated that the AUC(0-infinity)s of SYN-2836, SYN-2869, SYN-2903, and SYN-2921 in mouse lungs were significantly different from each other. The ratios of the concentrations of the SYN azoles in lungs to those in plasma were also significantly different from those for itraconazole. Among the SYN azoles the highest concentration in the lungs was found for SYN-2869. The higher level of distribution of SYN-2869 into lung tissue was considered to contribute to the potent efficacy in respiratory tract infection models compared with the potency of itraconazole. Significant differences in the pharmacokinetics of these compounds were observed in different animal species, and selection of an animal model for further evaluation was based on results obtained from these studies.

Emtricitabine (Emory University/Glaxo Wellcome/Triangle Pharmaceuticals).

Triangle Pharmaceuticals has licensed the development rights to emtricitabine (FTC), an antiviral nucleoside analog that is structurally related to 3TC, from Emory University [207618]. It is in phase III trials for HIV [324921] and in phase I/II trials for hepatitis B (HBV) [305302]. In June 1999, Triangle and Abbott Laboratories entered into an alliance for the development and marketing of six antiviral products, including FTC [326824]. An NDA was expected to be filed in 2000 [324921]. US-05814639 has been issued covering FTC [300465]. In April 2000, a report appeared in the South African media which suggested that a Triangle-sponsored trial (FTC-302), commenced in August 1999, had been halted [361984]. A total of 470 patients had been enrolled on the trial, which is a comparison of Coviracil and lamivudine, both drugs being used in combination with d4T and nevirapine. Patients with high viral loads received efavirenz instead of nevirapine. There was a higher than expected incidence of liver toxicity in this study and, in two cases, this liver toxicity resulted in death. Initially, Triangle reported that the trial was ongoing, although no additional patients were being enrolled at the time. However, the company received notification from the Medicines Control Council (MCC) in South Africa informing it that study FTC-302 should be terminated. The company is in ongoing discussions with the MCC [361792,361793]. Subsequently, the FDA also issued a hold on the trial, which is being carried out in South Africa under a US IND, and indicated that as a result of factors leading to this decision, study FTC-302 may not provide adequate support as part of an NDA submission. The planned NDA filing may now be delayed until the second half of 2001 and Triangle will discuss with the FDA any additional data required for the NDA application [361984].

Synthesis and antifungal activity of coumarins and angular furanocoumarins.

Angelicin, a naturally occurring furanocoumarin, that showed antifungal activity, was considered as a lead structure for a group of synthetic coumarins. Antifungal activities of the synthesized coumarins and angelicin derivatives were reported against Candida albicans, Cryptococcus neoformans, Saccharomyces cerevisiae and Aspergillus niger. Human cell line cytotoxicity of several coumarins was evaluated against KB cells. Angelicin and several potent antifungals showed to be non-toxic in this assay.

Synthesis and in vitro antifungal activity of 2-aryl-5-phenylsulfonyl-1,3,4-thiadiazole derivatives.

The synthesis and antifungal activity of a series of 2-nitroaryl-5-phenylsulfonyl-1,3,4-thiadiazoles (5a-e) are described. The in vitro antifungal activity of the compounds was determined against a variety of fungal strains in comparison to miconazole (CAS 22916-47-8) and fluconazole (CAS 86386-73-4). Two derivatives (5d, 5e) showed high activity against Candida albicans and Candida spp. having MIC values ranging from 0.048-3.12 micrograms/ml, providing higher potencies than the reference drug fluconazole. Compound 5a also showed high activity against Cryptococcus neoformans (MIC < 0.048 microgram/ml). The activity of this compound against Aspergillus niger and Aspergillus fumigatus was moderate (MIC = 1.56-6.25 micrograms/ml), while fluconazole was inactive. Moreover, the nitroimidazole derivative 5d possessed good activity against most fungal strains in comparison to fluconazole.

High-performance liquid chromatographic analysis of new triazole antifungal agent SYN-2869 and its derivatives in plasma.

A simple reversed-phase high-performance liquid chromatography (HPLC) method with UV detection was developed and validated for the quantitation of SYN-2869, a novel triazole antifungal agent and its analogs in rat plasma. The method involved a simple precipitation of plasma protein with acetonitrile (1:10 ratio). The reconstituted sample after evaporation to dryness was injected onto a HPLC column. SYN-2869 and its analogs were separated from the matrix components on a symmetry C18 column using an aqueous mobile phase of acetonitrile and water with a flow rate of 1 ml min(-1). A step gradient of 40-80% acetonitrile eluted all four compounds. The run time was 30 min. The linear range was 0.5 10 microg ml(-1)(r2 > 0.999). The limit of quantitation was 0.5 microg ml(-1). The inter-day precision and accuracy for SYN-2869 standard concentration were from 1.9 to 8.5% and from 1.4 to +/- 4.40%, respectively. The precision and accuracy of intra-day quality control samples were from 4.6 to 5.2% and from 4.6 to 12%, respectively.

International Society of Heterocyclic Chemistry--17th international congress. 1-6 August 1999, Vienna, Austria.

Approximately 1200 scientists attended this congress of heterocyclic chemistry, which focused on: New synthetic methods in heterocyclic chemistry; synthesis of bioactive heterocycles including natural products; heterocycles and asymmetric synthesis; heterocycles in bioorganic chemistry; new heterocyclic materials; structure and properties of heterocyclic compounds; solid-phase synthesis, combinatorial chemistry and heterocyclic scaffolds. These topics were covered in 600 posters and 100 plenary, invited and oral presentations. This report summarizes the highlights of the presentations related to the category of the synthesis of bioactive heterocycles including natural products.

(1)H-NMR and NOE studies of 2-cephems and 3-cephems.

The(1)H-NMR signals of 2-cephems and 3-cephems have been assigned and the Nuclear Overhauser Effect (NOE) study of these compounds was undertaken.

Synthesis and antifungal activities of myristic acid analogs.

Myristic acid analogs that are putative inhibitors of N-myristoyl-transferase were tested in vitro for activity against yeasts (Saccharomyces cerevisiae, Candida albicans, Cryptococcus neoformans) and filamentous fungi (Aspergillus niger). Several (+/-)-2-halotetradecanoic acids including (+/-)-2-bromotetradecanoic acid (14c) exhibited potent activity against C. albicans (MIC = 39 microM), C. neoformans (MIC = 20 microM), S. cerevisiae (MIC = 10 microM), and A. niger (MIC < 42 microM) in RPMI 1640 media. Improved synthetic methods have been developed for the synthesis of 12-fluorododecanoic acid (12a) and 12-chlorododecanoic acid (12c). Three novel fatty acids, 12-chloro-4-oxadodecanoic acid (8a), 12-phenoxydodecanoic acid (12i), and 11-(4-iodophenoxy)-undecanoic acid (13d) were also synthesized and tested.

Cytotoxic quinolines (Part 3). Synthesis of 1-azolylalkyl-4(1H)-quinolones as cytotoxic agents.

A series of 1-azolylalkyl-4(1H)-quinolones has been synthesized and evaluated for cytotoxic activity both in vitro and in vivo. The effects on cytotoxicity of varying substitution on the quinoline moiety was investigated. The insertion of a 5-amino group proved to be the most effective modification, resulting in a several-fold increase in cytotoxicity in vitro. Previously reported results indicated that the activity of this class of compounds may involve topoisomerase inhibition, but investigation of the current compounds has ruled out this possibility. One compound, 13, showed in vitro cytotoxicity notably superior to Adriamycin, however it demonstrated only slight or no in vivo efficacy depending on the model used.

Cytotoxic quinolines (part 1). Azolylalkyloxy quinolines and 1-azolylalkyl-4(1H)-quinolones.

A series of 4-azolylalkyloxyquinolines and 1-azolylalkyl-4(1H)-quinolones has been synthesized and evaluated for cytotoxicity against various cancer cell lines. 1-Phenyl-1,2,3-triazole and 1-methylpyrazole were found to be the most effective azoles. The length of the alkyl chain was critical, with 8 to 10 carbon atoms being optimal. Several of the compounds were found to be very cytotoxic in vitro towards various cancer cells. Compounds 9o, 10k, and 10r were evaluated in vivo, but were ineffective and exhibited acute general toxicity at higher dosages.

Cytotoxic quinolines (part 2). Azolylalkylamino and-thio quinolines.

A series of azolylalkylaminoquinolines and azolylalkylthioquinolines was synthesized and evaluated for cytotoxicity against various cancer cell lines. Structure-activity relationships previously established for azolylalkyloxyquinolines were generally found to apply for the present compounds. The azolylalkylaminoquinolines were found to be more cytotoxic than the corresponding thio compounds. Oxidation of 11a to sulfones 12 and 13 resulted in a reduction of cytotoxicity. Several of the compounds were found to be very cytotoxic in vitro towards different cancer cell lines. Compound 7d, the most cytotoxic in vitro against the P388 cell line in this series, was ineffective in vivo and exhibited significant general toxicity at higher dosages.