RESUMO
GW 471552, GW 471558, GW 479821, GW 515716, GW 570009, and GW 587270 are members of a new family of sordarin derivatives called azasordarins. The in vitro activities of these compounds were evaluated against clinical isolates of yeasts, including Candida albicans, Candida non-albicans, and Cryptococcus neoformans strains. Activities against Pneumocystis carinii, Aspergillus spp., less common molds, and dermatophytes were also investigated. Azasordarin derivatives displayed significant activities against the most clinically important Candida species, with the exception of C. krusei. Against C. albicans, including fluconazole-resistant strains, MICs at which 90% of the isolates tested are inhibited (MIC(90)s) were 0.002 microg/ml with GW 479821, 0.015 microg/ml with GW 515716 and GW 587270, and 0.06 microg/ml with GW 471552, GW 471558, and GW 570009. The MIC(90)s of GW 471552, GW 471558, GW 479821, GW 515716, GW 570009, and GW 587270 were 0.12, 0.12, 0.03, 0.06, 0.12, and 0.06 microg/ml, respectively, against C. tropicalis and 4, 0.25, 0.06, 0.25, 0.5, and 0.5 microg/ml, respectively, against C. glabrata. In addition, some azasordarin derivatives (GW 479821, GW 515716, GW 570009, and GW 58720) were active against C. parapsilosis, with MIC(90)s of 2, 4, 4, and 1 microg/ml, respectively. The compounds were extremely potent against P. carinii, showing 50% inhibitory concentrations of
Assuntos
Antibióticos Antineoplásicos/farmacologia , Antifúngicos/farmacologia , Fungos/efeitos dos fármacos , Animais , Arthrodermataceae/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Meios de Cultura , Humanos , Indenos , Masculino , Testes de Sensibilidade Microbiana , Pneumocystis/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Células Tumorais Cultivadas , Leveduras/efeitos dos fármacosRESUMO
The antifungal effect of GM 237354, a sordarin derivative, was studied in an in vitro pharmacokinetic (PK)-pharmacodynamic dynamic system (bioreactor) which reproduces PK profiles observed in a previously described model of drug efficacy against murine systemic candidiasis. Immunocompetent mice infected intravenously with 10(5) CFU of Candida albicans were treated with GM 237354 at 2.5, 10, and 40 mg/kg of body weight every 8 h subcutaneously for 7 days. Free concentrations in serum were calculated by multiplying total concentrations measured in vivo by 0.05, the free fraction determined in vitro by equilibrium dialysis. In the bioreactor the inoculum was approximately 10(6) CFU/ml; and a one-compartment PK model was used to reproduce the PK profiles of free and total GM 237354 in serum obtained in mice, and clearance of C. albicans was measured over 48 h. A good correlation was observed when the in vivo fungal kidney burden and the area under the survival time curve were compared with the in vitro broth "burden," although only when free in vivo levels in serum were reproduced in vitro. GM 237354 displayed a 3-log decrease effect both in vivo and in vitro. The very few reports available on in vitro-in vivo correlations have been obtained with antibiotics. The good in vitro-in vivo correlation obtained with an antifungal agent shows that the in vitro dynamic system could constitute a powerful investigational tool prior to assessment of the efficacy of an anti-infective agent in animals and humans.
Assuntos
Antifúngicos/farmacologia , Candida albicans/efeitos dos fármacos , Animais , Antifúngicos/química , Antifúngicos/farmacocinética , Antifúngicos/uso terapêutico , Sítios de Ligação , Proteínas Sanguíneas/metabolismo , Candidíase/tratamento farmacológico , Candidíase/metabolismo , Modelos Animais de Doenças , Indenos , Masculino , Camundongos , Testes de Sensibilidade Microbiana , Modelos Biológicos , Estatística como Assunto , Resultado do TratamentoRESUMO
Sordarin derivatives constitute a new group of synthetic antifungal agents that selectively inhibit fungal protein synthesis. They have demonstrated in vitro activity against the most important fungal pathogens, both yeast and filamentous. This new family of compounds has also shown in vivo activity against murine Candida albicans, Histoplasma capsulatum, and Coccidioides immitis experimental infections, as well as against Pneumocystis carinii pneumonia in rats. After intravenous dosing in animals, both the area under the concentration-time curve and the elimination half-life were highest in Cynomolgus monkeys, followed by those in rats, mice, and rabbits. The volume of distribution at steady state for sordarin derivatives was similar in all species tested. The clearance in rats and mice was higher than for other species. GM 237354, a sordarin derivative, was characterized by high serum protein binding in mouse, rat, and monkey serum (unbound fraction, < or =5%). An indirect evaluation of the effect of liver function upon the metabolism of this class of compounds has been made in animals with impaired liver function such as Gunn rats, as well as in allometric studies that showed better correlations of half-life to liver blood flow than to animal body weight. Linearity of the main pharmacokinetic parameters was demonstrated after intravenous dosing of the representative compound GM 193663 at 10 and 20 mg/kg of body weight in rats. Allometry was used to determine whether human pharmacokinetic parameters can be predicted from animal data by regression analysis against body weight and liver blood flow. All these results have demonstrated that the human pharmacokinetics of sordarin derivatives can be forecast from animal data.
Assuntos
Antifúngicos/farmacocinética , Inibidores da Síntese de Proteínas/farmacocinética , Animais , Antifúngicos/sangue , Antifúngicos/química , Sítios de Ligação , Proteínas Sanguíneas/metabolismo , Indenos , Infusões Intravenosas , Masculino , Camundongos , Modelos Animais , Inibidores da Síntese de Proteínas/sangue , Inibidores da Síntese de Proteínas/químicaRESUMO
Translation elongation factor 2 (EF2), which in Saccharomyces cerevisiae is expressed from the EFT1 and EFT2 genes, has been found to be targeted by a new family of highly specific antifungal compounds derived from the natural product sordarin. Two complementation groups of mutants resistant to the semisynthetic sordarin derivative GM193663 were found. The major one (21 members) consisted of isolates with mutations on EFT2. The minor one (four isolates) is currently being characterized but it is already known that resistance in this group is not due to mutations on EFT1, pointing to the complex structure of the functional target for these compounds. Mutations on EF2 clustered, forming a possible drug binding pocket on a three-dimensional model of EF2, and mutant cell extracts lost the capacity to bind to the inhibitors. This new family of antifungals holds the promise to be a much needed and potent addition to current antimicrobial treatments, as well as a useful tool for dissection of the elongation process in ribosomal protein synthesis.
Assuntos
Antifúngicos/farmacologia , Fatores de Alongamento de Peptídeos/efeitos dos fármacos , Sequência de Aminoácidos , Sítios de Ligação , Resistência Microbiana a Medicamentos , Indenos , Dados de Sequência Molecular , Mutação , Fator 2 de Elongação de Peptídeos , Fatores de Alongamento de Peptídeos/química , Fatores de Alongamento de Peptídeos/genéticaRESUMO
GR135402, a sordarin derivative, was isolated in an antifungal screening program. GR135402, sordarin, and derivatives of both compounds were evaluated for their ability to inhibit cell-free translational systems from five different pathogenic fungi (Candida albicans, Candida glabrata, Candida krusei, Candida parapsilosis, and Cryptococcus neoformans). The activity profile of GR135402 is extended to other chemical compounds derived from sordarin. Experimental results indicate that sordarin analogs exert their antifungal effects by specifically inhibiting the protein synthesis elongation cycle in yeasts but do not affect protein synthesis machinery in mammalian systems. Intrinsically resistant strains owe their resistance to differences in the molecular target of sordarins in these strains. Preliminary studies performed to elucidate the mode of action of this new class of antifungal agents have shown that the putative target of sordarins is one of the protein synthesis elongation factors.