A screening of the MMV Pathogen Box® reveals new potential antifungal drugs against the etiologic agents of chromoblastomycosis.

Chromoblastomycosis (CBM) is a chronic subcutaneous mycosis caused by traumatic implantation of many species of black fungi. Due to the refractoriness of some cases and common recurrence of CBM, a more effective and less time-consuming treatment is mandatory. The aim of this study was to identify compounds with in vitro antifungal activity in the Pathogen Box® compound collection against different CBM agents. Synergism of these compounds with drugs currently used to treat CBM was also assessed. An initial screening of the drugs present in this collection at 1 µM was performed with a Fonsecaea pedrosoi clinical strain according to the EUCAST protocol. The compounds with activity against this fungus were also tested against other seven etiologic agents of CBM (Cladophialophora carrionii, Phialophora verrucosa, Exophiala jeanselmei, Exophiala dermatitidis, Fonsecaea monophora, Fonsecaea nubica, and Rhinocladiella similis) at concentrations ranging from 0.039 to 10 µM. The analysis of potential synergism of these compounds with itraconazole and terbinafine was performed by the checkerboard method. Eight compounds inhibited more than 60% of the F. pedrosoi growth: difenoconazole, bitertanol, iodoquinol, azoxystrobin, MMV688179, MMV021013, trifloxystrobin, and auranofin. Iodoquinol produced the lowest MIC values (1.25-2.5 µM) and MMV688179 showed MICs that were higher than all compounds tested (5 - >10 µM). When auranofin and itraconazole were tested in combination, a synergistic interaction (FICI = 0.37) was observed against the C. carrionii isolate. Toxicity analysis revealed that MMV021013 showed high selectivity indices (SI ≥ 10) against the fungi tested. In summary, auranofin, iodoquinol, and MMV021013 were identified as promising compounds to be tested in CBM models of infection.

Discovery of the FDA-approved drugs bexarotene, cetilistat, diiodohydroxyquinoline, and abiraterone as potential COVID-19 treatments with a robust two-tier screening system.

Coronavirus Disease 2019 (COVID-19) caused by the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is associated with a crude case fatality rate of about 0.5-10 % depending on locality. A few clinically approved drugs, such as remdesivir, chloroquine, hydroxychloroquine, nafamostat, camostat, and ivermectin, exhibited anti-SARS-CoV-2 activity in vitro and/or in a small number of patients. However, their clinical use may be limited by anti-SARS-CoV-2 50 % maximal effective concentrations (EC50) that exceeded their achievable peak serum concentrations (Cmax), side effects, and/or availability. To find more immediately available COVID-19 antivirals, we established a two-tier drug screening system that combines SARS-CoV-2 enzyme-linked immunosorbent assay and cell viability assay, and applied it to screen a library consisting 1528 FDA-approved drugs. Cetilistat (anti-pancreatic lipase), diiodohydroxyquinoline (anti-parasitic), abiraterone acetate (synthetic androstane steroid), and bexarotene (antineoplastic retinoid) exhibited potent in vitro anti-SARS-CoV-2 activity (EC50 1.13-2.01 µM). Bexarotene demonstrated the highest Cmax:EC50 ratio (1.69) which was higher than those of chloroquine, hydroxychloroquine, and ivermectin. These results demonstrated the efficacy of the two-tier screening system and identified potential COVID-19 treatments which can achieve effective levels if given by inhalation or systemically depending on their pharmacokinetics.

Antimicrobial activity of iodoquinol 1%-hydrocortisone acetate 2% gel against ciclopirox and clotrimazole.

Commercially available topical formulations consisting of iodoquinol 1%-hydrocortisone acetate 2%, ciclopirox 0.77%, and clotrimazole 1%-betamethasone dipropionate 0.5% were assessed for their antimicrobial activity against cultures of Micrococcus luteus, Propionibacterium acnes, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Corynebacterium aquaticum, Trichophyton mentagrophytes, Malassezia furfur, Microsporum canis, Candida albicans, Trichophyton rubrum, or Epidermophyton floccosum. At 1 and 5 minutes following inoculation into suspensions of each product, aliquots were removed, serially diluted, and plated onto appropriate agar to determine the log reduction in colony-forming units (CFUs) for each organism. Iodoquinol 1% produced the broadest and greatest antimicrobial activity as measured by a 3-log reduction of CFU, active against all microbes tested following incubation times of 1 or 5 minutes, except M luteus. By contrast, ciclopirox 0.77% and clotrimazole 1% showed activity against P aeruginosa and T rubrum, with ciclopirox also killing M luteus, P acnes, M canis, C albicans, and E floccosum at 5 minutes. Iodoquinol 1%-hydrocortisone acetate 2% also was the only product that showed effective antibacterial reduction of MRSA at 1 minute.

Susceptibility testing of Dientamoeba fragilis ATCC 30948 with iodoquinol, paromomycin, tetracycline, and metronidazole.

Susceptibility testing was performed on Dientamoeba fragilis ATCC 30948 in a dixenic culture with Klebsiella pneumoniae and Bacteroides vulgatus. D. fragilis was cocultured with the bacteria in TYGM-9 medium (ATCC medium 1171). The activities of antiparasitic drugs were assessed by counting viable D. fragilis trophozoites with a hemacytometer by trypan blue exclusion. The minimal amebicidal concentrations of the following four drugs were determined: iodoquinol at 128 micrograms/ml, paromomycin at 16 micrograms/ml, tetracycline (questionably) at 32 micrograms/ml, and metronidazole at 32 micrograms/ml.

Susceptibility of an emetine-resistant mutant of Entamoeba histolytica to multiple drugs and to channel blockers.

Previously a cloned emetine-resistant mutant of the protozoal parasite Entamoeba histolytica was shown to overexpress a gene for an ameba homolog of the mammalian P-glycoprotein, a plasma membrane pump that removes hydrophobic drugs from multidrug-resistant tumor cells. Three sets of experiments were performed to better characterize the multidrug-resistant phenotype of the emetine-resistant amebae. First, the emetine resistance of the mutant amebae was reversed by concentrations of calcium and sodium channel blockers effective in reversing drug resistance by multidrug-resistant tumor cells, but it was reversed only in the presence of very high concentrations of the tricyclic antidepressants. Second, the mutant amebae showed cross-resistance to antiamebic drugs used to treat luminal infection (iodoquinol and diloxanide) but were not cross-resistant to drugs used to treat invasive disease (chloroquine and metronidazole). Third, when amebae were loaded with radiolabeled emetine, the mutant parasites released the drug at approximately 1.6 times the rate of the wild-type organisms. We conclude that the emetine-resistant E. histolytica parasites have some but not all the features of the multidrug-resistant phenotype.

[Reliability of the PEHPS culture medium for the in vitro evaluation of antiamebic drugs]. / Confiabilidad del medio de cultivo pehps para la evaluación in vitro de drogas antiamibianas.

Monophasic liquid media for axenical cultivation of Entamoeba histolytica, have permitted to define diverse aspects of this parasite's biology, without associated organisms interference. In addition, these media have allowed the in vitro evaluation of new drugs with potential antiamebic properties. PEHPS, a new medium recently developed in our laboratory, was used in order to determine its usefulness in the searching for new antiamebic compounds. The antiamebic potency of currently employed drugs in clinical therapy: emetine, metronidazole and diiodohydroxyquinoline on E. histolytica, strain HM-1, trophozoites grown in PEHPS was tested. The IC50 for each drug was 0.082 microgram/ml, 0.10 micrograms/ml and 5.84 micrograms/ml respectively. Results obtained with each drug are statistically reliable and reproducible, and agree with the species sensibility reported by several other authors. Accordingly, we propose PEHPS as a useful medium for new antiamebic drug research.

Genotoxicity of amebicide and anthelmintic drugs in Escherichia coli pol A+/pol A-.

The amebicides dehydroemetine and chloroquine diphosphate and the anthelmintic pyrvinium pamoate, previously reported to be mutagenic in Salmonella typhimurium (Cortinas de Nava et al., 1983), were clearly shown to be genotoxic in the Escherichia coli pol A+/pol A- assay. Two other antiparasitic drugs, diiodohydroxyquin and 4-hexylresorcinol, were also found to be genotoxic in E. coli, while iodochlorhydroxyquin preferentially inhibited the pol A+ strain. From the 3 alternative testing methods employed, the liquid suspension succeeded in detecting 5 antiparasitic drugs as genotoxic; the microsuspension identified 2, and the disc diffusion method only 1. However, the metabolic activation system could only be coupled successfully and in a reproducible way to the microsuspension assay.

Bio-antimutagenic effect of L-cysteine on diiodohydroxyquinoline-induced micronuclei in Swiss mice.

The mutagenic potential of diiodohydroxyquinoline (DIHQ), a common anti-amebic drug, was tested using the in vivo micronucleus test in Swiss mice following oral administration. It was found to be mutagenic in a dose-dependent manner. Using the same model system, the bio-antimutagenic effect of the sulfhydryl compound L-cysteine against DIHQ was established.