Activity of ketoconazole and its deacyl derivative against Plasmodium falciparum and Candida isolates

Exploiting large-scale drug-protein interaction information for computational drug repurposing

BACKGROUND

Despite increased investment in pharmaceutical research and development, fewer and fewer new drugs are entering the marketplace. This has prompted studies in repurposing existing drugs for use against diseases with unmet medical needs. A popular approach is to develop a classification model based on drugs with and without a desired therapeutic effect. For this approach to be statistically sound, it requires a large number of drugs in both classes. However, given few or no approved drugs for the diseases of highest medical urgency and interest, different strategies need to be investigated.

RESULTS

We developed a computational method termed "drug-protein interaction-based repurposing" (DPIR) that is potentially applicable to diseases with very few approved drugs. The method, based on genome-wide drug-protein interaction information and Bayesian statistics, first identifies drug-protein interactions associated with a desired therapeutic effect. Then, it uses key drug-protein interactions to score other drugs for their potential to have the same therapeutic effect.

CONCLUSIONS

Detailed cross-validation studies using United States Food and Drug Administration-approved drugs for hypertension, human immunodeficiency virus, and malaria indicated that DPIR provides robust predictions. It achieves high levels of enrichment of drugs approved for a disease even with models developed based on a single drug known to treat the disease. Analysis of our model predictions also indicated that the method is potentially useful for understanding molecular mechanisms of drug action and for identifying protein targets that may potentiate the desired therapeutic effects of other drugs (combination therapies).

Ketoconazole, a cytochrome P(450) inhibitor can potentiate the antimalarial action of α/β arteether against MDR Plasmodium yoelii nigeriensis

The emergence of multidrug resistant (MDR) strains of Plasmodium falciparum in South East Asia and other tropical countries, is posing serious challenge for the international efforts to eradicate malaria. New drug target/ACT/non-ACT combinations need to be discovered to control the spread of MDR malaria. The present communication deals with antimalarial potential of a new combination comprising of ketoconazole (KTZ) (an antifungal/inhibitor of CYP3A4) and artemisinin derivative α/β arteether (ART). In vitro interactions of these drugs against chloroquine sensitive/resistant P. falciparum (Pf3D7/K1) have shown an overall additive interaction with mean sum fractional inhibitory concentrations (∑FICs) of 1.1±0.33 against 3D7 and 1.51±0.42 against K1 strains. Sub-curative doses of KTZ (150mg/kg×7 days) combined with ART (6.25-12.5mg/kg×5 days) both administered orally have shown 100% curative action against MDR P. yoelii nigeriensis in Swiss mice. Besides lower dose of KTZ (75mg/kg) which is non-curative itself, in combination with 12.5mg/kg×5 days of ART treatment, was also 100% curative. Further studies on mechanism of action of KTZ (150mg/kg single dose) have shown that significant inhibitory action of the antifungal drug is through very high level of suppression of CYP (nearly 90%) compared to that of healthy mice liver. The companion drug therapy comprising of KTZ together with ART (25mg/kg×1 dose) also produced more than 50% inhibitory effect on the CYP enzyme level. Since the ART is known to be rapidly metabolized by the liver cytochrome P450 (CYP) 3A4 to Dihydroquinghasu, the combined therapy with KTZ (a strong CYP 3A4 inhibitor) may influence the pharmacokinetics of ART and consequently slow down the drug metabolism and prolong the plasma life of the active drug, which would contribute to enhanced antimalarial action of ART against MDR P. yoelii nigeriensis.

In vitro activity of antifungal drugs against Plasmodium falciparum field isolates

The increasing resistance of the malaria parasite Plasmodium falciparum to currently available drugs necessitates a continuous effort to develop new antimalarial agents. We therefore aimed to assess the in vitro activity of the antifungal drugs clotrimazole, fluconazole, ketoconazole, itraconazole, voriconazole, flucytosine, amphotericin B, and caspofungin against field isolates of P. falciparum from Lambaréné, Gabon. Using the histidin-rich protein 2 (HRP-2) assay we determined the drug susceptibility (EC(50), EC(90)) of 16 field isolates obtained from outpatients attending the Albert Schweitzer Hospital in Lambaréné, Gabon. For fluconazole, itraconazole and caspofungin the in vitro growth inhibition of these drugs is reported for the first time. Our data indicate that clotrimazole, fluconazole, itraconazole and caspofungin show median EC(50) values of 3.1 µg/mL, 1.9 µg/mL, 1.1 µg/mL and 1.1 µg/mL respectively. Ketoconazole, voriconazole, flucytosine and amphotercin B showed no relevant growth inhibition within the range of drug concentrations used in this study.

NO-donors. Part 17: Synthesis and antimicrobial activity of novel ketoconazole-NO-donor hybrid compounds

Novel hybrid compounds combining the antifungal drug ketoconazole with a diazen-1-ium-1,2-diolate or an organic nitrate moiety and the corresponding NO-donors without ketoconazole were synthesized and their activities against a broad variety of fungal strains were tested. Hybridization modifies the spectrum of antimicrobial activities and generally, the ketoconazole-NO-donor hybrids are more potent than ketoconazole. The NO-donors alone show insufficient effectiveness.

Potent antimalarial activity of clotrimazole in in vitro cultures of Plasmodium falciparum

The increasing resistance of the malaria parasite Plasmodium falciparum to currently available drugs demands a continuous effort to develop new antimalarial agents. In this quest, the identification of antimalarial effects of drugs already in use for other therapies represents an attractive approach with potentially rapid clinical application. We have found that the extensively used antimycotic drug clotrimazole (CLT) effectively and rapidly inhibited parasite growth in five different strains of P. falciparum, in vitro, irrespective of their chloroquine sensitivity. The concentrations for 50% inhibition (IC(50)), assessed by parasite incorporation of [(3)H]hypoxanthine, were between 0.2 and 1.1 microM. CLT concentrations of 2 microM and above caused a sharp decline in parasitemia, complete inhibition of parasite replication, and destruction of parasites and host cells within a single intraerythrocytic asexual cycle (approximately 48 hr). These concentrations are within the plasma levels known to be attained in humans after oral administration of the drug. The effects were associated with distinct morphological changes. Transient exposure of ring-stage parasites to 2.5 microM CLT for a period of 12 hr caused a delay in development in a fraction of parasites that reverted to normal after drug removal; 24-hr exposure to the same concentration caused total destruction of parasites and parasitized cells. Chloroquine antagonized the effects of CLT whereas mefloquine was synergistic. The present study suggests that CLT holds much promise as an antimalarial agent and that it is suitable for a clinical study in P. falciparum malaria.

The use of 5-fluorocytosine and ketoconazole in the culture of the erythrocytic stages of Plasmodium falciparum and some tumor cell lines

In vitro culture systems are often contaminated by bacteria and fungi. It is therefore often necessary to supplement culture media with agents such as penicillin/streptomycin, gentamycin or amphotericin B. The latter cannot be used in the in vitro culture of erythrocytic stages of P. falciparum, and thus anti-fungal agents have not been regularly used in this system. We describe the prophylactic use of 5-fluorocytosine (5-FC) and ketoconazole (KTZ) in tissue cultures at concentrations up to 300 and 10 micrograms/ml respectively which have no effect on the growth of P. falciparum (FCR-3 strain). A melanoma cell line (C32) and a line of uterine carcinoma (C41) were also unaffected by similar concentrations of 5-FC and KTZ. When dissolved in complete culture medium (RPMI 1640) with 10% human plasma, the minimum inhibitory concentration of 5-FC for a susceptible strain of Candida remained below 2 micrograms/ml. These experiments suggest that 5-FC (at 50 micrograms/ml) alone or in combination with KTZ (at 1 microgram/ml) is a useful addition to the armamentarium of antimicrobials available to the tissue culture biologist for a variety of cell culture systems.

Descriptive statistical analyses of serial dilution data

The serial dilution assay (for example, an in vitro antimicrobic susceptibility test or a serum antibody titer assay) is an important technique in biomedical research. The structure of the experiment forces grouping of the threshold concentrations into intervals. Statistical methods to analyse threshold concentrations from a batch of serial dilution assays should account for the grouping of the data. Many traditional subject area analyses, however, ignore the grouped nature of the data. This article discusses the discrepancy between the traditional subject area approach and the usual statistical approach for analysing such grouped data.

Ketoconazole. Mechanism of action, spectrum of activity, pharmacokinetics, drug interactions, adverse reactions and therapeutic use

Ketoconazole is a well-tolerated oral antifungal agent with a broad spectrum of activity in vitro, but in vitro testing has not yet been correlated to in vivo results. In addition, many variables that can alter in vitro test results have been identified. The drug shows effectiveness in the treatment of paracoccidioidomycosis, chronic mucocutaneous candidiasis, oral thrush, coccidioidomycosis and histoplasmosis. It was recently approved for use in blastomycosis. It is not yet approved for use in dermatophyte infections, but a large body of literature exists supporting this application. Ketoconazole has several reported drug interactions, including lower bioavailability with cimetidine, accumulation of cyclosporin during concurrent therapy and a possible disulfiram-like reaction with alcohol. It is highly protein bound to albumin and is extensively metabolized. Dosage adjustment is not required in renal failure. The main side effects are gastrointestinal and occur in 5-10% of the patients. Rare side effects include gynecomastia and hepatotoxicity. The latter is reported to occur in 1 of 12,000 patients. Ketoconazole impairs testosterone synthesis, and therefore it is recommended that administration more than once daily be avoided in men. The usual dosage is 200-400 mg administered once daily. Few comparative or controlled studies have been published thus far. How it compares to amphotericin B is not known. The optimum dosage and the optimum duration of therapy are not established.