真菌耐药的分子机制及新型抗真菌药物

真菌耐药性的发生率日益增多,严重影响了抗真菌药物的治疗效果。在分子水平上了解真菌耐药性的发生机制对控制其耐药性的发展和新型抗真菌药物的研究和开发十分重要。本文介绍了近年来真菌耐药性研究的新进展,以及目前正处于研究阶段的新型抗真菌药物。     

Sordaricin antifungal agents

Compounds based on sordaricin were prepared via organometallic addition onto a fully protected sordaricin aldehyde. The fungal growth inhibition profiles for these compounds were established and the results are presented here. The synthesis of homologated sordaricin as well as ether and ester derivatives is presented, and structural rearrangement products upon oxidation. These compounds were evaluated as agents to inhibit fungal growth.     

New synthetic antifungal agents

Summary New antifungal agents of the aromatic disulphide and sulphenamide type have been investigated by chemosynthesis.A large number of substances has been screened using several tests against various representative micro-organisms.In vitro tests of isomeric disulphides, symmetrically substituted with various groupings, revealed substances with high in vitro activity against human pathogenic fungi, amongst N, N'-monosubstituted bis-amides of 2,2'-diphenyldisulphide-dicarboxylic acid. Some of these substances show activity equal to or greater than that of the best-known natural and synthetic antifungal agents.The postulation of interdependence between the activity of these substances and the possibility in such molecules of tautomeric phenomena with prototropic equilibrium and also the proved importance of the sulphenamide function for antimycotic activity, led to investigation of N-substituted benzisothiazol-3-ones. Also these compounds proved highly active against pathogenic fungi.The level and range of activity of the bis-n.butylamide of 2,2' diphenyl-disulphide-dicarboxylic acid and N-cyclohexyl-benzisothiazol-3-one suggested the therapeutic study of these substances.For this reason, a pilot clinical investigation was carried out, which clearly showed that the two compounds, incorporated in suitable bases, are generally well tolerated by human skin either normal or with epidermomycotic lesions.The two compounds under test, when applied directly to epidermomycotic areas of various types (groin epidermophytia, erythrasma, pityriasis versicolor, monilial intertrigo and perlèche, athlete's foot, etc.) showed high antifungal activity, equal to or greater than that of well-known antifungal drugs in current therapeutic use.Read in the meeting of the First Congress of the International Society for Tropical Dermatology, Naples, June 8–13, 1964.     

Pharmacogenomics of systemic antifungal agents

The genomic era offers a multitude of new technologies that may make the promise of personalized medicine a reality for patients in this century. Numerous new antifungal agents have been developed over the past two decades, but use of these agents requires optimization of pharmacokinetics and dosing to achieve efficacy and minimize toxicity. This article reviews the potential application of pharmacogenomics to the use of antifungal agents, highlighting genetic variation that may affect absorption, distribution, metabolism, and elimination of these compounds.     

Pediatric pharmacology of antifungal agents

Pediatric age groups display important differences in host biology, predisposing conditions, epidemiology, and presentation of fungal infections relative to the adult population. Over the past decade, major advances have been made in the field of medical mycology. Most importantly, an array of new antifungal agents has entered the clinical arena. Although pediatric approval of several of these agents remains to be established, the pediatric development of antifungal agents is moving forward. Invasive fungal infections will remain important causes for morbidity and mortality in immunocompromised pediatric patients. Although the availability of new therapeutic options is an important advance, antifungal therapy has become increasingly complex, and a thorough understanding of the available antifungal armamentarium is essential for the successful management of individual patients.     

Novel broad-spectrum metal-based antifungal agents

Summary Copper(II) complexes of the type [Cu(L)X], where L=tridentate anion of 2-acetylpyridineN ⁴-diethyl thiosemicarbazone and X=C1 or Br, were screened against seven fungal strains pathogenic to man viz.Aspergillus niger, Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Tricophyton rubrum, Epidermophyton foccosum andMicrosporum canis. The greater growth inhibition exhibited by the bromo complex can be explained on the basis of its lower Cu(II)/Cu(I) redox couple and greater covalent bonding. These compounds represent a novel class of metal-based antifungal agents which provide opportunities for a large number of synthetic variations for modulation of the activities.     

Antifungal activity of nontraditional antifungal agents

Invasive fungal infections are becoming increasingly important in the management of critically ill and immunocompromised patients. As organ and stem cell transplantation becomes more prominent and immune therapies are employed for diseases such as rheumatoid arthritis and plaque psoriasis, the population of patients at risk continues to grow. Many invasive fungal infections are associated with extremely high mortality rates. Antifungal options are limited and novel therapies are intriguing as we attempt to improve patient outcomes and preserve the antifungal armamentarium. Many other classes of pharmaceuticals typically seen as non-antifungal do in fact have significant antifungal activity. Prominent among these are calcineurin inhibitors, antiarrhythmics, antidepressants, antibacterials, and others. Some have activity alone and some augment the activity of conventional antifungals. Unfortunately, clinical data are lacking for most of these agents and their role in therapy remains undefined. This review focuses on several representative non-antifungal agents with antifungal activity.     

Clinical efficacy of new antifungal agents

Several new options are now available for treating serious fungal infections. All three echinocandin agents currently available have been shown in randomized, blinded clinical trials to be efficacious in treating candidemia and invasive candidiasis. By contrast, the demonstrated efficacy of the echinocandins for the treatment of invasive aspergillosis has been based on historically controlled salvage treatment trials in patients failing or intolerant of other therapies. The new triazole agents, voriconazole and posaconazole, have a broad spectrum of antifungal activity. Voriconazole has become the agent of choice for invasive aspergillosis. On the basis of compassionate treatment data, posaconazole appears to be effective for treatment of zygomycosis. These agents have also been shown to be effective in the treatment of non-Aspergillus mould infections, several of the endemic mycoses and serious Candida infections.     

Therapeutic drug monitoring of eculizumab: Rationale for an individualized dosing schedule

The annual cost of eculizumab maintenance therapy in paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic–uremic syndrome (aHUS) exceeds $300,000 per patient. A better understanding of eculizumab pharmacokinetics and subsequent individual dose adjustment could reduce this cost. We measured the trough eculizumab concentration in 9 patients with maintenance therapy (aHUS, n = 7; PNH, n = 2) and determined: 1) the intra- and inter-individual variability; 2) the influence of weight on eculizumab pharmacokinetics; and 3) the rate of elimination of eculizumab following discontinuation. A one-compartment model was developed to describe the pharmacokinetics of eculizumab and predicted complement activity by body weight. Trough eculizumab concentrations were >50 µg/mL in 9/9, >100 µg/mL in 8/9, and >300 µg/mL in 5/9 of patients. Intra-individual variability was low but eculizumab concentrations, closely correlated with patient weight (R² = 0.66, p = 0.034), varied broadly (55 ± 12 to 733 ± 164 µg/mL). Pharmacokinetic modeling showed that the elimination half-life varied greatly, with an increase from 7.8 d in a patient weighing 100 kg to 19.5 d in a 40 kg patient. We predicted that infusions of 1200 mg could be spaced every 4 or 6 weeks in patients weighing <90 and <70 kg, respectively. In this pilot study, the current recommended use of a fixed eculizumab dose for maintenance therapy is associated with excessively high trough concentrations in many patients. Further prospective larger studies are now required to support an individualized schedule adjusted for patient weight and based on the observed trough serum eculizumab concentration.     

Therapeutic drug monitoring of eculizumab: Rationale for an individualized dosing schedule

The annual cost of eculizumab maintenance therapy in paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic–uremic syndrome (aHUS) exceeds $300,000 per patient. A better understanding of eculizumab pharmacokinetics and subsequent individual dose adjustment could reduce this cost. We measured the trough eculizumab concentration in 9 patients with maintenance therapy (aHUS, n = 7; PNH, n = 2) and determined: 1) the intra- and inter-individual variability; 2) the influence of weight on eculizumab pharmacokinetics; and 3) the rate of elimination of eculizumab following discontinuation. A one-compartment model was developed to describe the pharmacokinetics of eculizumab and predicted complement activity by body weight. Trough eculizumab concentrations were >50 µg/mL in 9/9, >100 µg/mL in 8/9, and >300 µg/mL in 5/9 of patients. Intra-individual variability was low but eculizumab concentrations, closely correlated with patient weight (R² = 0.66, p = 0.034), varied broadly (55 ± 12 to 733 ± 164 µg/mL). Pharmacokinetic modeling showed that the elimination half-life varied greatly, with an increase from 7.8 d in a patient weighing 100 kg to 19.5 d in a 40 kg patient. We predicted that infusions of 1200 mg could be spaced every 4 or 6 weeks in patients weighing <90 and <70 kg, respectively. In this pilot study, the current recommended use of a fixed eculizumab dose for maintenance therapy is associated with excessively high trough concentrations in many patients. Further prospective larger studies are now required to support an individualized schedule adjusted for patient weight and based on the observed trough serum eculizumab concentration.     

Substituted indoloquinolines as new antifungal agents

Cryptolepine (2) possesses desirable properties to serve as a lead in developing new antifungal agents. Using SAR techniques, several analogues of cryptolepine were designed to increase potency and to broaden the antifungal spectrum over several opportunistic microorganisms. A number of 2-substituted indoloquinolines have been synthesized and evaluated in antifungal screens and several have been shown to increase potency and expand the antifungal spectrum of cryptolepine. Comparison of MICs of a number of these analogues with standard antifungal agents, shows them to be comparable to Amphotericin B and Ketoconazole.     

6种抗真菌药物对皮肤癣菌体外抗真菌活性评价

目的评价6种抗真菌药物对皮肤癣菌体外抗真菌活性。方法采用CLSI推荐的M-38P方案对分离自足癣和体、股癣的皮肤癣菌进行联苯苄唑、硝酸舍他康唑、硝酸异康唑、盐酸布替萘芬、阿莫洛芬、利拉萘酯6种抗真菌药物敏感性测定。结果联苯苄唑MIC范围为0．03—4mg／L,MIC50为1mg／L,MIC90为2mg／L。硝酸舍他康唑分别为0．06—16mg／L、0．5mg／L和2mg／L。硝酸异康唑分别为0．03～2mg／L、0．25mg／L和0．5mg／L。盐酸布替萘芬分别为0．0025～0．04mg／L、0．01mg／L和0．02mg／L。阿莫罗芬分别为0．01～〉0．08mg／L、0．02mg／L和0．04mg／L。利拉萘酯分别为0．004—0．625mg／L、0．039mg／L和0．312mg／L。结论6种抗真菌药物对皮肤癣菌均有强的抗菌活性,由强到弱依次为布替萘芬、阿莫罗芬、利拉萘酯和咪唑类药物。     

Promising antifungal agents: A minireview

In the recent past, prevalence of life threatening fungal diseases have increased rapidly in immune-compromised cases such as acquired immunodeficiency syndrome (AIDS), cancer, organ transplant etc. Side by side, the appearance of drug resistance to the presently available antifungal therapeutics is on a rapid rise. It has become a top priority for the academia and pharmaceutical industries to develop new antifungal agents able to combat this resistance, and at the same time, possess potential broad spectrum of activity and minimum toxicity. An understanding of the pharmacological interactions between antifungal agents and their targets offers opportunities for design of new therapeutics. This review discusses the various methodology of drug design, structure activity relationships (SARs), and mode of action of variety of new antifungal agents.     

Lipid-based antifungal agents: a concise overview

The development of lipid formulations of antifungal drugs has been a remarkable progress in the systemic antifungal arena. The lipid-based amphotericin B formulations; amphotericin B lipid complex (ABLC), amphotericin B colloidal dispersion (ABCD), and liposomal amphotericin B (L-AMB) have been in clinical use since the 1990s. They are significantly less nephrotoxic than the parent compound and can be safely used at higher doses. The primary cost of these formulations is significantly high and the extent of data related to their head-to-head comparison remains limited. The lipid formulation of nystatin, liposomal nystatin, is another lipid-based polyene under development. Available data concerning the in vitro activity, pharmacokinetic profile, in vivo efficacy, and safety of these formulations are summarized in this overview.     

New antifungal agents for the systemic mycoses

The azoles are the prominent broad spectrum oral antifungal agents in use or under clinical investigation for the systemic mycoses. This class of antifungal agents is represented by the marketed drug ketoconazole (Nizoral) and the experimental triazoles furthest along in clinical trials in the United States, itraconazole and fluconazole. Ketoconazole use is limited by its side effect profile and activity spectrum. Itraconazole appears to be better tolerated and less toxic to liver function, does not cause adrenal suppression and is more active against Aspergillus and Sporothrix schenckii. Fluconazole appears to be a highly promising agent due its highly favorable pharmacokinetic profile; it is water soluble, is well tolerated, is not metabolized to inactive constituents, it has a long half-life and, unlike the other azoles, high cerebrospinal fluid levels are readily attained for consideration in meningeal mycoses. It remains to be determined what place these new triazoles have in managing immunosuppressed patients including those with acquired immune deficiency syndrome known as AIDS. Other experimental antifungal agents, including ambruticin, amphotericin B methyl ester and saramycetin are also described. Sales figures are presented of drugs marketed in the United States for the systemic mycoses and reflect the growing problem of fungal diseases in the population.Presented as part of the Everett S. Beneke Symposium in Mycology, May 27, 1988.     

Sordarin oxazepine derivatives as potent antifungal agents

The synthesis and biological activity of sordarin oxazepine derivatives are described. The key step features a regioselective oxidation of an unprotected triol followed by double reductive amination to afford the ring-closed products. The spectrum of antifungal activity for these novel derivatives includes coverage of Candida albicans, Candida glabrata, and Cryptococcus neoformans.     

Studies on hydrazone derivatives as antifungal agents

The increasing clinical importance of drug-resistant fungal pathogens has urged additional need to fungal research and new antifungal compound development. For this purpose, some N-(1-benzyl-2-phenylethylidene)-N′-[4-(aryl)thiazol-2-yl]hydrazone (1a-e) and N-(1-phenylbutylidene)-N′-[4-(aryl)thiazol-2-yl]hydrazone (2a-e) derivatives were synthesised and evaluated for antifungal activity. Their antifungal activities against standard and clinical strands of Candida albicans, Candida glabrata, Candida utilis, Candida tropicalis, Candida krusei, Candida zeylanoides, and Candida parapsilosis were investigated. A significant level of activity was observed.