Clinical pharmacology of systemic antifungal agents: a comprehensive review of agents in clinical use, current investigational compounds, and putative targets for antifungal drug development

New developments in chemotherapy for non-invasive fungal infections

Dermatomycosis and subcutaneous mycosis comprise the non-invasive fungal infections commonly encountered in clinical practice around the world. The limited activity of early topical antifungal agents prompted the development of more effective systemic agents. While griseofulvin has been used for more than four decades, the use of early azoles, such as ketoconazole have resulted in better patient compliance and thus greater success. However, poor response and recurrence in dermatomycosis, as well as toxicity associated with ketoconazole therapy, has led to the search for newer antifungal agents and more effective treatment strategies. Terbinafine, itraconazole and fluconazole have the advantage of non-toxicity and a broad spectrum of activity. An overview of non-invasive fungal infections, antifungal agents in clinical use and recent developments in antifungal therapy is reviewed in this article.

Antifungal pharmacodynamics: concentration-effect relationships in vitro and in vivo

The pharmacodynamics of antifungal compounds involve relationships among drug concentrations, time, and antimicrobial effects in vitro and in vivo. Beyond better understanding of a drug's mode of action, characterization of these relationships has important implications for setting susceptibility breakpoints, establishing rational dosing regimens, and facilitating drug development. Important advances have been made in the experimental investigation of pharmacokinetics and pharmacodynamics of antifungal drugs; however, much remains to be learned about specific pathogens and specific sites of infection. Increased incorporation of pharmacokinetic and pharmacodynamic principles in experimental and clinical studies with antifungal agents is an important objective that will benefit the treatment and prophylaxis of life-threatening invasive fungal infections in immunocompromised patients.

Caspofungin: pharmacology, safety and therapeutic potential in superficial and invasive fungal infections

Invasive fungal infections are important causes of morbidity and mortality in hospitalised patients. Current therapy with amphotericin B and antifungal triazoles has overlapping targets and is limited by toxicity and resistance. The echinocandin lipopeptide caspofungin is the first of a new class of antifungal compounds that inhibit the synthesis of 1,3-beta-D-glucan. This homopolysaccharide is a major component of the cell wall of many pathogenic fungi and yet is absent in mammalian cells. It provides osmotic stability and is important for cell growth and cell division. In vitro, caspofungin has broad-spectrum antifungal activity against Candida and Aspergillus spp. without cross-resistance to existing agents. The compound exerts prolonged post-antifungal effects and fungicidal activity against Candida spp. and causes severe damage of Aspergillus fumigatus at the sites of hyphal growth. Animal models have demonstrated efficacy against disseminated candidiasis and disseminated and pulmonary aspergillosis, both in normal and in immunocompromised animals. Caspofungin possesses favourable pharmacokinetic properties and is not metabolised through the cytochrome P450 (CYP) enzyme system. It showed highly promising antifungal efficacy in Phase II and III clinical trials in immunocompromised patients with oesophageal candidiasis. Caspofungin was effective in patients with invasive aspergillosis intolerant or refractory to standard therapies. Based on its documented antifungal efficacy and an excellent safety profile, caspofungin has been approved recently by the US Food and Drug Administration for the treatment of invasive aspergillosis in patients who are refractory to or intolerant of other therapies (i.e., amphotericin B, lipid formulations of amphotericin B, and/or itraconazole). Phase III clinical trials in patients with candidaemia and in persistently febrile neutropenic patients requiring empirical antifungal therapy are ongoing. This paper reviews the preclinical and clinical pharmacology of caspofungin and its potential role for treatment of invasive and superficial fungal infections in patients.

A clinical perspective for the management of invasive fungal infections: focus on IDSA guidelines. Infectious Diseases Society of America

Invasive fungal infections, especially candidiasis and aspergillosis, are a major cause of morbidity and mortality. Many controversies surround the management of these infections. A critical overview of the recent Infectious Diseases Society of America practice guidelines is provided, as are comments on both the conundrums and future perspectives in medical mycology.

Rationale for combination antifungal therapy

The relentless increase of invasive fungal infections and poor outcomes associated with available antifungal agents prompted the search for better therapeutic strategies. Combining antifungal drugs was recommended as a means to enhance efficacy in a variety of invasive infections including cryptococcosis, candidiasis, and aspergillosis. With the exception of cryptococcal meningitis, data from controlled clinical trials supporting such combinations are sparse. Moreover, little consensus exists regarding which combinations are synergistic or antagonistic in vitro and in vivo. Based on available data, several principles underlie these combinations.

An antisense-based functional genomics approach for identification of genes critical for growth of Candida albicans

Converting the complete genome sequence of Candida albicans into meaningful biological information will require comprehensive screens for identifying functional classes of genes. Most systems described so far are not applicable to C. albicans because of its difficulty with mating, its diploid nature, and the lack of functional random insertional mutagenesis methods. We examined artificial gene suppression as a means to identify gene products critical for growth of this pathogen; these represent new antifungal drug targets. To achieve gene suppression we combined antisense RNA inhibition and promoter interference. After cloning antisense complementary DNA (cDNA) fragments under control of an inducible GAL1 promoter, we transferred the resulting libraries to C. albicans. Over 2,000 transformant colonies were screened for a promoter-induced diminished-growth phenotype. After recovery of the plasmids, sequence determination of their inserts revealed the messenger RNA (mRNA) they inhibited or the gene they disrupted. Eighty-six genes critical for growth were identified, 45 with unknown function. When used in high-throughput screening for antifungals, the crippled C. albicans strains generated in this study showed enhanced sensitivity to specific drugs.

Pharmacodynamics of amphotericin B in a neutropenic-mouse disseminated-candidiasis model

In vivo pharmacodynamic parameters have been described for a variety of antibacterials. These parameters have been studied in correlation with in vivo outcomes in order to determine which dosing parameter is predictive of outcome and the magnitude of that parameter associated with efficacy. Very little is known about pharmacodynamics for antifungal agents. We utilized a neutropenic mouse model of disseminated candidiasis to correlate pharmacodynamic parameters (percent time above MIC [T > MIC], area under the concentration time curve [AUC]/MIC ratio, and peak serum level/MIC ratio) for amphotericin B in vivo with efficacy, as measured by organism number in homogenized kidney cultures after 72 h of therapy. Amphotericin B was administered by the intraperitoneal route. Drug kinetics for amphotericin B in infected mice were nonlinear. Serum half-lives ranged from 13 to 27 h. Infection was achieved by intravenous inoculation with 10(6) CFU of yeast cells per ml via the lateral tail vein of neutropenic mice. Groups of mice were treated with fourfold escalating total doses of amphotericin B ranging from 0.08 to 20 mg/kg of body weight divided into 1, 3, or 6 doses over 72 h. Increasing doses produced concentration-dependent killing, ranging from 0 to 2 log(10) CFU/kidney compared to the organism number at the start of therapy. Amphotericin B also produced prolonged dose-dependent suppression of growth after serum levels had fallen below the MIC. Nonlinear regression analysis was used to determine which pharmacodynamic parameter best correlated with efficacy. Peak serum level in relation to the MIC (peak serum level/MIC ratio) was the parameter best predictive of outcome, while the AUC/MIC ratio and T > MIC were only slightly less predictive (peak serum level/MIC ratio, coefficient of determination [R(2)] = 90 to 93%; AUC/MIC ratio, R(2) = 49 to 69%; T > MIC, R(2) = 67 to 85%). The total amount of drug necessary to achieve various microbiological outcomes over the treatment period was 4.8- to 7.6-fold smaller when the dosing schedule called for large single doses than when the same amount of total drug was administered in 2 to 6 doses. Given the narrow therapeutic window of amphotericin B and frequent treatment failures, these results suggest the need for a reevaluation of current dosing regimens.

Antifungal activity and pharmacokinetics of posaconazole (SCH 56592) in treatment and prevention of experimental invasive pulmonary aspergillosis: correlation with galactomannan antigenemia

The antifungal efficacy, safety, and pharmacokinetics of posaconazole (SCH 56592) (POC) were investigated in treatment and prophylaxis of primary pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of POC at 2, 6, and 20 mg/kg of body weight per os; itraconazole (ITC) at 2, 6, and 20 mg/kg per os; or amphotericin B (AMB) at 1 mg/kg intravenously. Rabbits treated with POC showed a significant improvement in survival and significant reductions in pulmonary infarct scores, total lung weights, numbers of pulmonary CFU per gram, numbers of computerized-tomography-monitored pulmonary lesions, and levels of galactomannan antigenemia. AMB and POC had comparable therapeutic efficacies by all parameters. By comparison, animals treated with ITC had no significant changes in outcome variables in comparison to those of untreated controls (UC). Rabbits receiving prophylactic POC at all dosages showed a significant reduction in infarct scores, total lung weights, and organism clearance from lung tissue in comparison to results for UC (P < 0.01). There was dosage-dependent microbiological clearance of A. fumigatus from lung tissue in response to POC. Serum creatinine levels were greater (P < 0.01) in AMB-treated animals than in UC and POC- or ITC-treated rabbits. There was no elevation of serum hepatic transaminase levels in POC- or ITC-treated rabbits. The pharmacokinetics of POC and ITC in plasma demonstrated dose dependency after multiple dosing. The 2-, 6-, and 20-mg/kg dosages of POC maintained plasma drug levels above the MICs for the entire 24-h dosing interval. In summary, POC at > or =6 mg/kg/day per os generated sustained concentrations in plasma of > or =1 microg/ml that were as effective in the treatment and prevention of invasive pulmonary aspergillosis as AMB at 1 mg/kg/day and more effective than cyclodextrin ITC at > or =6 mg/kg/day per os in persistently neutropenic rabbits.

Recent developments in molecular genetics of Candida albicans

The frequency of opportunistic infections caused by the fungus Candida albicans is very high and is expected to continue to increase as the number of immunocompromised patients rises. Research initiatives to study the biology of this organism and elucidate its pathogenic determinants have therefore expanded significantly during the last 5-10 years. The past few years have also brought continuous improvement in the techniques to study gene function by gene inactivation and by regulated gene expression and to study gene expression and protein localization by using gene reporter systems. As steadily more genomic sequence information from this human fungal pathogen becomes available, we are entering a new era in antimicrobial research. However, many of the currently available molecular genetics tools are poorly adapted to a genome-wide functional analysis in C. albicans, and further development of these tools is hampered by the asexual and diploid nature of this organism. This review outlines recent advances in the development of molecular tools for functional analysis in C. albicans and summarizes current knowledge about the genomic and genetic variability of this important human fungal pathogen.

Comparative toxicities and pharmacokinetics of intrathecal lipid (amphotericin B colloidal dispersion) and conventional deoxycholate formulations of amphotericin B in rabbits

The lipid formulation of amphotericin B, Amphotec (ABCD), has not been used intrathecally. After a single intrathecal dose or after four doses, conventionally formulated deoxycholate amphotericin B (AMB) (Fungizone) resulted in higher levels of amphotericin B in the cerebrospinal fluid of rabbits than did ABCD. Clinically and histologically, ABCD was about threefold less toxic than AMB after a single dose and 3- to 30-fold less toxic after multiple dosing. These data are encouraging for the potential use of ABCD as an intrathecal treatment.

Acrophialophora fusispora brain abscess in a child with acute lymphoblastic leukemia: review of cases and taxonomy

A 12-year-old girl with acute lymphoblastic leukemia was referred to King Faisal Specialist Hospital and Research Center. The diagnosis without central nervous system (CNS) involvement was confirmed on admission, and chemotherapy was initiated according to the Children Cancer Group (CCG) 1882 protocol for high-risk-group leukemia. During neutropenia amphotericin B (AMB) (1 mg/kg of body weight/day) was initiated for presumed fungal infection when a computed tomography (CT) scan of the chest revealed multiple nodular densities. After 3 weeks of AMB therapy, a follow-up chest CT revealed progression of the pulmonary nodules. The patient subsequently suffered a seizure, and a CT scan of the brain was consistent with infarction or hemorrhage. Because of progression of pulmonary lesions while receiving AMB, antifungal therapy was changed to liposomal AMB (LAMB) (6 mg/kg/day). Despite 26 days of LAMB, the patient continued to have intermittent fever, and CT and magnetic resonance imaging of the brain demonstrated findings consistent with a brain abscess. Aspiration of brain abscess was performed and the Gomori methenamine silver stain was positive for hyphal elements. Culture of this material grew Acrophialophora fusispora. Lung biopsy showed necrotizing fungal pneumonia with negative culture. The dosage of LAMB was increased, and itraconazole (ITRA) was added; subsequently LAMB was discontinued and therapy was continued with ITRA alone. The patient demonstrated clinical and radiological improvement. In vitro, the isolate was susceptible to low concentrations of AMB and ITRA. A. fusispora is a thermotolerant, fast-growing fungus with neurotropic potential. We report the first case of human infection involving the CNS. Acrophialophora resembles Paecilomyces but differs in having colonies that become dark and in the development of phialides along the sides or at the tips of echinulate brown conidiophores. Conidia are borne in long chains and are smooth or ornamented with fine-to-coarse echinulations, sometimes in spiral bands. The taxonomy of the genus Acrophialophora is reviewed, and Acrophialophora nainiana and Acrophialophora levis are considered as synonyms of A. fusispora.

Itraconazole-amphotericin B antagonism in Aspergillus fumigatus: an E-test-based strategy

We examined an E-test-based strategy for testing the combination of itraconazole and amphotericin B, the latter given either sequentially or concomitantly, in isolates of Aspergillus fumigatus. An antagonistic interaction between the two drugs was noted, especially with the sequential administration of amphotericin B. This in vitro antagonism was reversible.

Invasive aspergillosis. Disease spectrum, treatment practices, and outcomes. I3 Aspergillus Study Group

A review of representative cases of invasive aspergillosis was conducted to describe current treatment practices and outcomes. Eighty-nine physicians experienced with aspergillosis completed case forms on 595 patients with proven or probable invasive aspergillosis diagnosed using modifications of the Mycoses Study Group criteria. Pulmonary disease was present in 56%, with disseminated infection in 19%. The major risk factors for aspergillosis were bone marrow transplantation (32%) and hematologic malignancy (29%), but patients had a variety of underlying conditions including solid organ transplants (9%), AIDS (8%), and pulmonary diseases (9%). Overall, high antifungal failure rates occurred (36%), and complete antifungal responses were noted in only 27%. Treatment practices revealed that amphotericin B alone (187 patients) was used in most severely immunosuppressed patients while itraconazole alone (58 patients) or sequential amphotericin B followed by itraconazole (93 patients) was used in patients who were less immunosuppressed than patients receiving amphotericin B alone. Response rate for patients receiving amphotericin B alone was poor, with complete responses noted in only 25% and death due to or with aspergillosis in 65%. In contrast, patients receiving itraconazole alone or following amphotericin B had death due to or with Aspergillus in 26% and 36%, respectively. These results confirm that mortality from invasive aspergillosis in severely immunosuppressed patients remains high even with standard amphotericin B. Improved responses were seen in the less immunosuppressed patients receiving sequential amphotericin B followed by itraconazole and those receiving itraconazole alone. New approaches and new therapies are needed to improve the outcome of invasive aspergillosis in high-risk patients.

New drugs and novel targets for treatment of invasive fungal infections in patients with cancer

Invasive fungal infections have emerged as important causes of morbidity and mortality in profoundly immunocompromised patients with cancer. Current treatment strategies for these infections are limited by antifungal resistance, toxicity, drug interactions, and expense. In order to overcome these limitations, new antifungal compounds are being developed, which may improve our therapeutic armamentarium for prevention and treatment of invasive mycoses in high-risk patients with neoplastic diseases.

Agents for treatment of invasive fungal infections

The incidence of fungal infections continues to rise as the population of immunocompromised individuals increases. Despite the enlarging numbers of infections, there are only a few antifungal agents for treatment of deep-seated, invasive infections. These agents include amphotericin B, flucytosine, terbinafine, and several azoles. Progress has been made in understanding the role of these agents in a variety of infections and this article examines in detail these agents and their prophylactic, empiric, and therapeutic uses in invasive mycoses. This article focuses on general concepts of antifungal therapies and provides a detailed review of each antifungal agent available for treatment of deep-seated mycoses.

Compartmental pharmacokinetics and tissue distribution of multilamellar liposomal nystatin in rabbits

The plasma pharmacokinetics of multilamellar liposomal nystatin were studied in normal, catheterized rabbits after single and multiple daily intravenous administration of dosages of 2, 4, and 6 mg/kg of body weight, and drug levels in tissues were assessed after multiple dosing. Concentrations of liposomal nystatin were measured as those of nystatin by a validated high-performance liquid chromatography method, and plasma concentration data were fitted into a two-compartment open model. Across the investigated dosage range, liposomal nystatin demonstrated nonlinear kinetics with more than proportional increases in the AUC(0-24) and decreasing clearance, consistent with dose-dependent tissue distribution and/or a dose-dependent elimination process. After single-dose administration, the mean C(max) increased from 13.07 microg/ml at 2 mg/kg to 41.91 microg/ml at 6 mg/kg (P < 0.001); the AUC(0-24) changed from 11.65 to 67.44 microg. h/ml (P < 0.001), the V(d) changed from 0.205 to 0. 184 liters/kg (not significant), the CL(t) from 0.173 to 0.101 liters/kg. h (P < 0.05), and terminal half-life from 0.96 to 1.51 h (P < 0.05). There were no significant changes in pharmacokinetic parameters after multiple dosing over 14 days. Assessment of tissue concentrations of nystatin near peak plasma levels after multiple dosing over 15 days revealed preferential distribution to the lungs, liver, and spleen at that time point. Substantial levels were also found in the urine, raising the possibility that renal excretion may play a significant role in drug elimination. Liposomal nystatin administered to rabbits was well tolerated and displayed nonlinear pharmacokinetics, potentially therapeutic peak plasma concentrations, and substantial penetration into tissues. Pharmacokinetic parameters were very similar to those observed in patients, thus validating results derived from infection models in the rabbit and allowing inferences to be made about the treatment of invasive fungal infections in humans.

Practice guidelines for the treatment of candidiasis. Infectious Diseases Society of America

Infections due to Candida species are the most common of the fungal infections. Candida species produce a broad range of infections, ranging from nonlife-threatening mucocutaneous illnesses to invasive process that may involve virtually any organ. Such a broad range of infections requires an equally broad range of diagnostic and therapeutic strategies. This document summarizes current knowledge about treatment of multiple forms of candidiasis and is the guideline of the Infectious Diseases Society of America (IDSA) for the treatment of candidiasis. Throughout this document, treatment recommendations are scored according to the standard scoring scheme used in other IDSA guidelines to illustrate the strength of the underlying data. The document covers 4 major topical areas. The role of the microbiology laboratory. To a greater extent than for other fungi, treatment of candidiasis can now be guided by in vitro susceptibility testing. The guidelines review the available information supporting current testing procedures and interpretive breakpoints and place these data into clinical context. Susceptibility testing is most helpful in dealing with infection due to non-albicans species of Candida. In this setting, especially if the patient has been treated previously with an azole antifungal agent, the possibility of microbiological resistance must be considered. Treatment of invasive candidiasis. In addition to acute hematogenous candidiasis, the guidelines review strategies for treatment of 15 other forms of invasive candidiasis. Extensive data from randomized trials are really available only for therapy of acute hematogenous candidiasis in the nonneutropenic adult. Choice of therapy for other forms of candidiasis is based on case series and anecdotal reports. In general, both amphotericin B and the azoles have a role to play in treatment. Choice of therapy is guided by weighing the greater activity of amphotericin B for some non-albicans species (e.g., Candida krusei) against the lesser toxicity and ease of administration of the azole antifungal agents. Flucytosine has activity against many isolates of Candida but is not often used. Treatment of mucocutaneous candidiasis. Therapy for mucosal infections is dominated by the azole antifungal agents. These drugs may be used topically or systemically and have been proven safe and efficacious. A significant problem with mucosal disease is the propensity for a small proportion of patients to suffer repeated relapses. In some situations, the explanation for such a relapse is obvious (e.g., relapsing oropharyngeal candidiasis in an individual with advanced and uncontrolled HIV infection), but in other patients the cause is cryptic (e.g., relapsing vaginitis in a healthy woman). Rational strategies for these situations are discussed in the guidelines and must consider the possibility of induction of resistance over time. Prevention of invasive candidiasis. Prophylactic strategies are useful if the risk of a target disease is sharply elevated in a readily identified group of patients. Selected patient groups undergoing therapy that produces prolonged neutropenia (e.g., some bone-marrow transplant recipients) or who receive a solid-organ transplant (e.g., some liver transplant recipients) have a sufficient risk of invasive candidiasis to warrant prophylaxis.

Distribution of lipid formulations of amphotericin B into bone marrow and fat tissue in rabbits

The distribution of the three currently available lipid formulations of amphotericin B (AmB) into bone marrow and fat tissue was evaluated in noninfected rabbits. Groups of four animals each received either 1 mg of AmB deoxycholate (D-AmB) per kg of body weight per day or 5 mg of AmB colloidal dispersion, AmB lipid complex, or liposomal AmB per kg per day for seven doses. Plasma, bone marrow, fat, and liver were collected at autopsy, and AmB concentrations were determined by high-performance liquid chromatography. At the investigated dosages of 5 mg/kg/day, all AmB lipid formulations achieved at least fourfold-higher concentrations in bone marrow than did standard D-AmB at a dosage of 1 mg/kg/day. Concentrations in bone marrow were 62 to 76% of concurrent AmB concentrations in the liver. In contrast, all AmB formulations accumulated comparatively poorly in fat tissue. The results of this study show that high concentrations of AmB can be achieved in the bone marrow after administration of lipid formulations, suggesting their particular usefulness against disseminated fungal infections involving the bone marrow and against visceral leishmaniasis.

Single allele knock-out of Candida albicans CGT1 leads to unexpected resistance to hygromycin B and elevated temperature

Almost all eukaryotic mRNAs are capped at their 5'-terminus. Capping is crucial for stability, processing, nuclear export and efficient translation of mRNA. We studied the phenotypic effects elicited by depleting a Candida albicans strain of mRNA 5'-guanylyltransferase (mRNA capping enzyme; CGT1). Construction of a Cgt1-deficient mutant was achieved by URA-blaster-mediated genetic disruption of one allele of the CGT1 gene, which was localized on chromosome III. The resulting heterozygous mutant exhibited an aberrant colony morphology resembling the 'irregular wrinkle' phenotype typically obtained from a normal C. albicans strain upon mild UV treatment. Its level of CGT1 mRNA was reduced two- to fivefold compared to the parental strain. Proteome analysis revealed a large number of differentially expressed proteins confirming the expected pleiotropic effect of CGT1 disruption. The disrupted strain was significantly more resistant to hygromycin B, an antibiotic which decreases translational fidelity, and showed increased resistance to heat stress. Proteome analysis revealed a 50-fold overexpression of Ef-1alphap and a more than sevenfold overexpression of the cell-wall heat-shock protein Ssa2p. Compared to a reference strain, the cgt1/CGT1 heterozygote was equally virulent for mice and guinea pigs when tested in an intravenous infection model of disseminated candidiasis.

Emerging fungal pathogens: evolving challenges to immunocompromised patients for the twenty-first century

Opportunistic fungi have emerged during the past decade as important causes of morbidity and mortality in immunocompromised patients. Candida species constitute the third to fourth most common causes of nosocomial blood stream infections, and Aspergillus species have emerged as the most common infectious cause of pneumonic mortality in bone marrow/stem cell transplant recipients. Among HIV-infected patients, meningoencephalitis due to Cryptococcus neoformans ranks among the most common AIDS-defining infections. Hyaline septated filamentous fungi, such as Fusarium species, Acremonium species, Paecilomyces species, and Trichoderma species, are increasingly reported as causing invasive mycoses refractory to conventional therapy. Dematiaceous septated filamentous fungi, such as Pseudallescheria boydii, Bipolaris species, and Cladophialophora bantiana cause pneumonia, sinusitis, and CNS infection unresponsive to current therapy. An increasing number of different members of the class of Zygomycetes are reported as causing lethal infections, despite aggressive medical and surgical interventions. Yet the treatment for zygomycosis has not changed in approximately 40 years. The prevalence of the endemic mycoses, such as those due to Penicillium marneffei, Coccidioides immitis, and Histoplasma capsulatum, has been reported to expand rapidly in response to environmental exposures and increased numbers of vulnerable hosts in endemic regions of the world. Dermatophytoses are occurring with increasing prevalence and morbidity in elderly and immunocompromised patients. As we enter the next millennium, we may anticipate that emergent fungal infections will continue to develop in the settings of permissive environmental conditions, selective antifungal pressure, and an expanding population of immunocompromised hosts.

Role of newer azoles in surgical patients

Fungal infection has become an important cause of morbidity and mortality in critically ill surgical patients. Surgical patients at highest risk for invasive mycoses include those undergoing extensive abdominal surgery, those with underlying malignancy or other immunosuppressive conditions, and patients undergoing transplantation. Nosocomial candidemia remains a major complication for patients in surgical intensive units; however, the epidemiology of invasive fungal infection continues to change with molds and yeasts other than Candida albicans emerging as important causes of infection especially in immunosuppressed patients. This changing epidemiology has resulted in the need for an expanded armamentarium of antifungal therapies. One effective approach has been the utilization of higher doses of well-tolerated azoles, such as fluconazole, particularly against yeasts with dose-dependent susceptibility. Alternatively, the presumptive use of therapeutic doses of fluconazole may be indicated in intensive care unit patients with persistent leukocytosis and fever in whom a source of fever cannot be identified, particularly if the patient is extensively colonized at mucosal sites with yeast. New azoles with an expanded spectrum of activity are in development. These include agents include voriconazole, which has activity against resistant yeasts and molds and is in phase III clinical trials, posaconazole (Sch 56592) and ravuconazole (BMS-207147)--both of which are less advanced in clinical development, but which also offer an expanded spectrum of activity. Other new azoles with expanded activity are still in the early phases of development. In this review, strategies for optimizing use of the clinically available new azoles and the potential for new agents are discussed.

High-performance liquid chromatographic determination of liposomal nystatin in plasma and tissues for pharmacokinetic and tissue distribution studies

A reliable reversed-phase high-performance liquid chromatographic method was developed for the determination of liposomal nystatin in plasma. Nystatin is extracted by 1:2 (v/v) liquid-liquid extraction with methanol. Separation is achieved by HPLC after direct injection on a muBondapak C18 analytical column with a mobile phase composed of 10 mM sodium phosphate, 1 mM EDTA, 30% methanol and 30% acetonitrile adjusted to pH 6. Detection is by ultraviolet absorbance at 305 nm. Quantitation is based on the sum of the peak area concentration of the two major isomers of nystatin, which elute at 7.5-8.5 and 9.5-10.5 min. The assay was linear over the concentration range of 0.05 to 50 microg/ml. The lower limit of quantitation was 0.05 microg/ml, sufficient for investigating the plasma pharmacokinetics of liposomal nystatin in preclinical studies. Accuracies and intra- and inter-day precision showed good reproducibility. With minor modifications, this method also was used for assaying nystatin in various non-plasma body fluids and tissues.

Antifungal activities of antineoplastic agents: Saccharomyces cerevisiae as a model system to study drug action

Recent evolutionary studies reveal that microorganisms including yeasts and fungi are more closely related to mammals than was previously appreciated. Possibly as a consequence, many natural-product toxins that have antimicrobial activity are also toxic to mammalian cells. While this makes it difficult to discover antifungal agents without toxic side effects, it also has enabled detailed studies of drug action in simple genetic model systems. We review here studies on the antifungal actions of antineoplasmic agents. Topics covered include the mechanisms of action of inhibitors of topoisomerases I and II; the immunosuppressants rapamycin, cyclosporin A, and FK506; the phosphatidylinositol 3-kinase inhibitor wortmannin; the angiogenesis inhibitors fumagillin and ovalicin; the HSP90 inhibitor geldanamycin; and agents that inhibit sphingolipid metabolism. In general, these natural products inhibit target proteins conserved from microorganisms to humans. These studies highlight the potential of microorganisms as screening tools to elucidate the mechanisms of action of novel pharmacological agents with unique effects against specific mammalian cell types, including neoplastic cells. In addition, this analysis suggests that antineoplastic agents and derivatives might find novel indications in the treatment of fungal infections, for which few agents are presently available, toxicity remains a serious concern, and drug resistance is emerging.

Safety and efficacy of multilamellar liposomal nystatin against disseminated candidiasis in persistently neutropenic rabbits

The activity of liposomal nystatin (L-Nys) against subacute disseminated candidiasis was investigated in persistently neutropenic rabbits. Antifungal therapy was administered for 10 days starting 24 h after intravenous inoculation of 10(3) blastoconidia of Candida albicans. Responses to treatment were assessed by the quantitative clearance of the organism from blood and tissues. Treatments consisted of L-Nys at dosages of 2 and 4 mg/kg of body weight/day (L-Nys2 and L-Nys4, respectively) amphotericin B deoxycholate at 1 mg/kg/day (D-AmB), and fluconazole at 10 mg/kg/day (Flu). All treatments were given intravenously once daily. Compared to the results for untreated but infected control animals, treatment with L-Nys2, L-Nys4, D-AmB, and Flu resulted in a significant clearance of the residual burden of C. albicans from the kidney, liver, spleen, lung, and brain (P < 0.0001 by analysis of variance). When the proportion of animals infected at at least one of the five tissue sites studied was evaluated, a dose-dependent response to treatment with L-Nys was found (P < 0.05). Compared to D-AmB-treated rabbits, mean serum creatinine and blood urea nitrogen levels at the end of therapy were significantly lower in animals treated with L-Nys2 (P < 0.001) and L-Nys4 (P < 0.001 and P < 0.01, respectively). L-Nys was less nephrotoxic than conventional amphotericin B and had dose-dependent activity comparable to that of amphotericin B for the early treatment of subacute disseminated candidiasis in persistently neutropenic rabbits.

The 1998 Garrod lecture. Current and future antifungal therapy: new targets for antifungal agents

Invasive fungal infections are a major problem in immunocompromised patients. The recent expansion of antifungal drug research has occurred because there is a critical need for new antifungal agents to treat these life-threatening invasive infections. The overview of the development of antifungal therapy which is provided herein reflects the increased interest in this very special area of infectious diseases. Although we have newer, less toxic, antifungal agents that are available for clinical use, their clinical efficacy in some invasive fungal infections, such as aspergillosis and fusariosis, is not optimal. Thus, intense efforts in antifungal drug discovery are still needed to develop more promising and effective antifungal agents for use in the clinical arena.