Caspofungin: an echinocandin antifungal agent

BACKGROUND: The mainstays of treatment for nosocomial fungal infections have been amphotericin B and azole derivatives. Caspofungin acetate is a new echinocandin antifungal agent with a mechanism of action that targets a structural component of the fungal cell wall. OBJECTIVE: This article describes the pharmacologic properties and potential clinical usefulness of caspofungin. METHODS: Relevant information was identified through searches of MEDLINE (1966-September 2001). Iowa Drug Information Service (1966-September 2001), and International Pharmaceutical Abstracts (1970-September 2001), as well as meeting abstracts of the Infectious Diseases Society of America and the Interscience Conference on Antimicrobial Agents and Chemotherapy (1996-2001), using the terms caspofungin, MK-0991, pneumocandin, echinocandin, candin, and beta-(1,3)-glucan inhibitor. RESULTS: In vitro, caspofungin exhibits antifungal activity against an array of clinically important yeasts and molds, including Candida and Aspergillus spp. The proposed susceptibility breakpoint for caspofungin against Candida spp, the most common cause of nosocomial fungal infections, is a minimum inhibitory concentration of < or =1 microg/mL. In humans, caspofungin has a volume of distribution of 9.67 L, is extensively bound to albumin (97%), has a plasma elimination half-life of 9 to 11 hours, and is metabolized to inactive metabolites in the liver. Dose adjustment based on age, sex, race, or renal function does not appear to be necessary, although patients with moderate hepatic insufficiency (Child-Pugh score 7-9) should receive a lower maintenance dose. The results of clinical trials, although somewhat preliminary, suggest that caspofungin is effective in the treatment of esophageal and oropharyngeal candidiasis and invasive aspergillosis. When combined with other antifungal agents, caspofungin produces a synergistic or additive effect against a variety of clinically important fungi. The most commonly reported adverse events with caspofungin have included fever, infusion-related reactions, headache, nausea, elevations in liver transaminase levels, and histamine-type reactions. The recommended dosage in adults is 70 mg IV on day 1 followed by 50 mg/d, with the duration of treatment depending on the severity of the patient's underlying condition and the clinical response. CONCLUSION: Although additional studies are needed, caspofungin appears to be a promising agent for the treatment of patients with difficult-to-treat or life-threatening fungal infections.     

Caspofungin: an overview

The echinocandins are a novel class of antifungal agents that have come into use over the past 10 years. The mechanism of action of these lipopeptide agents is via noncompetitive inhibition of the synthesis of 1,3-beta-glucans, which are fungal cell wall constituents. All agents of this class are only available in an intravenous formulation. The first approved agent of this class was caspofungin (Cancidas). Caspofungin is a therapeutic option for patients with candidal esophagitis and deep-seated candidal infections, and is an alternative therapy for Aspergillus infections, especially in the salvage setting. In addition, it is a therapeutic option for the empiric therapy of febrile neutropenia. The usefulness of this agent in treating less common fungal infections has been cited in anecdotal reports. One major limitation of this drug is the lack of an oral formulation. Caspofungin may be considered as a component of combination antifungal regimens. Caspofungin represents a significant advance in the care of patients with serious fungal infections.     

Caspofungin: the first representative of a new antifungal class

Caspofungin (MK-0991; L-743,872) belongs to the echinocandin family, a new class of antifungal agents that act on the fungal cell wall by inhibiting glucan synthesis. Data in vitro, and experimental studies, have demonstrated that caspofungin has antifungal activity against yeasts of the genus Candida (including isolates resistant to azoles and amphotericin B), several species of filamentous fungi, including Aspergillus, and certain dimorphic fungi, such as Histoplasma, Blastomyces and Coccidioides. In vitro and in animals, caspofungin shows additive or synergic antifungal activity with amphotericin B and triazoles. It also possesses activity against Pneumocystis carinii. Clinical trials have shown caspofungin to be well tolerated and effective in invasive aspergillosis in patients refractory or intolerant to standard treatment (45% favourable responses), in oropharyngeal and oesophageal candidiasis (67-93% favourable responses with an efficacy similar to those of amphotericin B and fluconazole), and in invasive candidiasis with efficacy equivalent to that of amphotericin B, and better tolerability. The results of these first clinical trials were promising, and led to the approval of caspofungin for invasive aspergillosis after failure of, or intolerance to, standard therapy. Further studies are required to define the exact role of caspofungin in the antifungal armamentarium.     

Recent advances in antifungal pharmacotherapy for invasive fungal infections

Invasive fungal infections carry significant morbidity and mortality. Candida species have become one of the most frequent causes of bloodstream infections, and infections caused by molds such as Aspergillus are becoming more frequent in immunocompromised patients. As this population grows, more invasive fungal infections can be anticipated. In the past, treatment options have been limited for many of these infections due to toxicity and efficacy concerns with the available antifungals. Fortunately, the past few years have brought exciting developments in antifungal pharmacotherapy. Lipid-based formulations of amphotericin B were introduced in the 1990s to attenuate adverse effects caused by amphotericin B deoxycholate (Fungizone, Bristol-Myers Squibb). Most recently, the echinocandins have been added to our antifungal regimen with the introduction of caspofungin (Cancidas, Merck and Co.) and voriconazole (Vfend, Pfizer), a new triazole, has come to market. The introduction of the echinocandins has invigorated the discussion about combination antifungal therapy. Evidence-based studies using these new agents are accumulating, and they are assuming important roles in the pharmacotherapy of invasive fungal infections in seriously ill and complex patients.     

Echinocandins in invasive candidiasis]

Invasive fungal infections on the intensive care unit are predominantly caused by Candida spp., most frequently manifesting as candidemia. In spite of increasing treatment options during the last 2 decades, mortality of invasive candidiasis remains high with 20-50%. With the echinocandins, a new class of antifungal drugs with activity against clinically relevant Aspergillus and Candida spp. has become available since the beginning of the new millennium. The echinocandins have shown convincing efficacy in numerous multicenter, mostly double-blinded phase III clinical trials. These trials compared current standard treatment regimens with the echinocandins anidulafungin, caspofungin, and micafungin. All trials observed noninferiority of the new drugs against the standard treatment; in the case of anidulafungin, superiority against fluconazole was demonstrated. Especially in trials utilizing amphotericin B as comparator, significantly less treatment-related adverse events were observed when using an echinocandin. Echinocandins have a low drug-drug interaction profile and are only marginally affected by liver function. Especially in ICU (intensive care unit) patients frequently showing single- or multiorgan failure and receiving a multitude of drugs with complex interactions, echinocandins have become the treatment of first choice for invasive candidiasis.     

Inhibition of HIV by chemokine receptor antagonists: exciting new targets,complex development

The prevalence of invasive fungal infections is increasing and the infections are becoming a major problem in immunocompromised children and neonates. Fortunately, there has been a recent surge in the development of new antifungal agents. Caspofungin, the first licensed echinocandin, is a novel class of antifungal and is approved for use in children 3 months of age or older for the treatment of invasive candidiasis, salvage therapy for invasive aspergillosis and as empirical therapy for febrile neutropenia. This article reviews the published data on the use of caspofungin in immunocompromised children and neonates with invasive fungal infections.     

Caspofungin therapy in immunocompromised children and neonates

The prevalence of invasive fungal infections is increasing and the infections are becoming a major problem in immunocompromised children and neonates. Fortunately, there has been a recent surge in the development of new antifungal agents. Caspofungin, the first licensed echinocandin, is a novel class of antifungal and is approved for use in children 3 months of age or older for the treatment of invasive candidiasis, salvage therapy for invasive aspergillosis and as empirical therapy for febrile neutropenia. This article reviews the published data on the use of caspofungin in immunocompromised children and neonates with invasive fungal infections.     

Echinocandin antifungals: review and update

The echinocandins are a new and unique class of antifungal agents that act on the fungal cell wall by way of noncompetitive inhibition of the synthesis of 1,3-beta-glucans. All agents of this class are of parenteral formulation, with no oral preparations available. Caspofungin (Cancidas) was the first approved echinocandin, followed recently by micafungin (Mycamine) and anidulafungin (Eraxis). The precise role of the echinocandins in the antifungal armamentarium is still unfolding. Caspofungin is approved for the treatment of candidal esophagitis and candidemia, salvage therapy of Aspergillus infections and for empirical therapy of febrile neutropenia. Micafungin is likewise approved for candidal esophagitis, in addition to antifungal prophylaxis for hematopoietic stem cell transplant recipients. Anidulafungin is also approved for treatment of candidal esophagitis, as well as therapy of candidemia. There has been anecdotal use of these agents to treat less common fungal pathogens, as well as limited use as a component of combination antifungal therapy. The echinocandins are an important addition to the antifungal armamentarium in the treatment of fungal infections in both immunocompromised patients and those with normal immunity.     

Caspofungin: an overview

The echinocandins are a novel class of antifungal agents that have come into use over the past 10 years. The mechanism of action of these lipopeptide agents is via noncompetitive inhibition of the synthesis of 1,3-β-glucans, which are fungal cell wall constituents. All agents of this class are only available in an intravenous formulation. The first approved agent of this class was caspofungin (Cancidas^®). Caspofungin is a therapeutic option for patients with candidal esophagitis and deep-seated candidal infections, and is an alternative therapy for Aspergillus infections, especially in the salvage setting. In addition, it is a therapeutic option for the empiric therapy of febrile neutropenia. The usefulness of this agent in treating less common fungal infections has been cited in anecdotal reports. One major limitation of this drug is the lack of an oral formulation. Caspofungin may be considered as a component of combination antifungal regimens. Caspofungin represents a significant advance in the care of patients with serious fungal infections.     

Voriconazole: therapeutic review of a new azole antifungal

The new triazole antifungal, voriconazole (Vfend, Pfizer Ltd), was developed for the treatment of life-threatening fungal infections in immunocompromised patients. The drug, which is available for both oral and intravenous administration, has broad-spectrum activity against pathogenic yeasts, dimorphic fungi and opportunistic moulds. Unlike fluconazole (Diflucan, Pfizer Ltd), voriconazole has potent in vitro activity against Aspergillus spp., Fusarium spp. and Scedosporium apiospermum. In Phase II/III trials, voriconazole was well-tolerated and had excellent clinical efficacy in patients with fluconazole-sensitive and -resistant candida infection, aspergillosis, and various refractory fungal infections. The US Food and Drug Administration approved voriconazole in May 2002 for the treatment of invasive aspergillosis, and serious infections caused by Fusarium and S. apiospermum in patients who are intolerant of, or refractory to, other antifungal agents. In Europe, voriconazole is approved by the European Medicines Agency for the treatment of invasive aspergillosis, serious infections caused by Fusarium and S. apiospermum, and fluconazole-resistant serious invasive candida infections (including C. krusei).     

Posaconazole: a new antifungal weapon

The last twenty years, the incidence of invasive fungal infections (IFI) has risen dramatically due to the prolongation of survival of patients with multiple risk factors for fungal infections. Amphotericin B was for more than 40 years the gold standard for almost all IFI, but toxicity and resistance, especially of new and emerging pathogens remained important issues. Fluconazole and itraconazole have also the same disadvantage of resistance. Voriconazole, a new triazole antifungal has offered an additional option, but the problem of resistant aspergillosis, and zygomycosis remains. Echinocandins (caspofungin, micafungin and anidulafungin) are active only against Candida and Aspergillus spp., but not against Fusarium, Scedosporium and Zygomycetes. Posaconazole is the most recently approved triazole with broad spectrum activity against Candida spp., Aspergillus spp., Cryptococcus neoformans, Zygomycetes, dermatiaceous, dimorphic, and other fungal pathogens. Interestingly, posaconazole is active against Candida spp., resistant to fluconazole and itraconazole, and Aspergillus fumigatus resistant to fluconazole itraconazole, amphotericin B, and voriconazole. The results from clinical trials of posaconazole as salvage treatment are encouraging. Multicenter clinical trials have also established its role in the prophylaxis of (IFI) in the severely immunocompromised patients such as those after hematopoietic stem cell transplantation (HSCT) who developed graft versus host disease (GVHD), as well as the neutropenic patients with an acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) after myeloablative chemotherapy. Posaconazole has pharmacokinetic advantages and low side effect profile, which are very important, especially in the seriously ill population.     

Invasive candidiasis in the intensive care unit

OBJECTIVE: To review epidemiologic trends, advances in diagnosis and susceptibility testing, therapeutic options and guidelines, and management strategies for invasive candidiasis as relevant to the intensive care unit physician. DATA SOURCES, STUDY SELECTION, DATA EXTRACTION, DATA SYNTHESIS: Nonstructured review of peer-reviewed original articles, review articles, abstracts, guidelines, and consensus statements appearing in Medline, major scientific journals, and conference proceedings. CONCLUSIONS: Invasive candidiasis is a problem associated with substantial morbidity and mortality that is highly prevalent in the intensive care unit setting. Recent epidemiologic studies have shown a trend toward increasing numbers of infections and a shift toward infections caused by non-albicans Candida species. Guidelines for the management of these diseases have been published and recommend amphotericin B, fluconazole, or caspofungin as the primary therapeutic option. The choice of agent should depend on local epidemiology and patient factors. The role of newer antifungal agents for this population, such as the new azoles and echinocandins, remains to be determined. Priority areas of research include diagnostics, risk identification, and management strategy assessment such as prophylactic, preemptive, and empirical therapy.     

Voriconazole: therapeutic review of a new azole antifungal

The new triazole antifungal, voriconazole (Vfend^®, Pfizer Ltd), was developed for the treatment of life-threatening fungal infections in immunocompromised patients. The drug, which is available for both oral and intravenous administration, has broad-spectrum activity against pathogenic yeasts, dimorphic fungi and opportunistic moulds. Unlike fluconazole (Diflucan^®, Pfizer Ltd), voriconazole has potent in vitro activity against Aspergillus spp., Fusarium spp. and Scedosporium apiospermum. In Phase II/III trials, voriconazole was well-tolerated and had excellent clinical efficacy in patients with fluconazole-sensitive and -resistant candida infection, aspergillosis, and various refractory fungal infections. The US Food and Drug Administration approved voriconazole in May 2002 for the treatment of invasive aspergillosis, and serious infections caused by Fusarium and S. apiospermum in patients who are intolerant of, or refractory to, other antifungal agents. In Europe, voriconazole is approved by the European Medicines Agency for the treatment of invasive aspergillosis, serious infections caused by Fusarium and S. apiospermum, and fluconazole-resistant serious invasive candida infections (including C. krusei).     

Update on new antifungal therapy

Increases in rates as well as morbidity and mortality associated with fungal infections have necessitated the need for additional antifungal agents. Recent research has resulted in the introduction of 3 new antifungal agents: micafungin, anidulafungin, and posaconazole. Micafungin and anidulafungin, both potent inhibitor of 1,3-beta-D-glucan synthase, are the second and third available agents in the echinocandins class that are available in clinical practice. Posaconazale, a potent inhibitor of ergosterol synthesis, is a new agent in the triazole class that has shown promising clinical efficacy in the treatment and prophylaxis of invasive fungal infections due to Candida as well as molds. This article reviews the clinical efficacy as well as the approved uses and dosages associated with the use of these new antifungal agents. Other considerations, such as precautions, administration techniques, potential drug interactions, and common adverse effects associated with the use of these agents, are also reviewed.     

Efficacy of the echinocandin caspofungin against disseminated aspergillosis and candidiasis in cyclophosphamide-induced immunosuppressed mice

The in vivo efficacy of the echinocandin antifungal caspofungin acetate (caspofungin; MK-0991) was evaluated in models of disseminated aspergillosis and candidiasis in mice with cyclophosphamide (CY)-induced immunosuppression. Caspofungin is a 1, 3-beta-D-glucan synthesis inhibitor efficacious against a number of clinically relevant fungi including Aspergillus and Candida species. Models of CY-induced transient or chronic leukopenia were used with once daily administration of therapy initiated 24 h after microbial challenge. Caspofungin was effective in treating disseminated aspergillosis in mice that were transiently leukopenic (significant prolongation of survival at doses of > or =0.125 mg/kg of body weight and a 50% protective dose [PD(50)] of 0.245 mg/kg/day at 28 days after challenge) or chronically leukopenic (50 to 100% survival at doses of > or =0.5 mg/kg and PD(50)s ranging from 0.173 to 0.400 mg/kg/day). Caspofungin was effective in the treatment and sterilization of Candida infections in mice with transient leukopenia with a 99% effective dose based on reduction in log(10) CFU of Candida albicans/gram of kidneys of 0.119 mg/kg and 80 to 100% of the caspofungin-treated mice having sterile kidneys at caspofungin doses from 0.25 to 2.0 mg/kg. In Candida-infected mice with chronic leukopenia, caspofungin was effective at all dose levels tested (0.25 to 1.0 mg/kg), with the log(10) CFU of C. albicans/gram of kidneys of caspofungin-treated mice being significantly lower (>99% reduction) than that of sham-treated mice from day 4 to day 28 after challenge. Also, 70 to 100% of the caspofungin-treated, chronic leukopenic mice had sterile kidneys at caspofungin doses of 0.5 to 1.0 mg/kg from day 8 to 28 after challenge. Sterilization of Candida infections by caspofungin in the absence of host leukocytes provides compelling in vivo evidence for fungicidal activity against C. albicans. Further human clinical trials with caspofungin against serious fungal infections are in progress.     

Head-to-head comparison of the activities of currently available antifungal agents against 3,378 Spanish clinical isolates of yeasts and filamentous fungi

We have compared the activities of posaconazole and other currently available antifungal agents against a collection of 3,378 clinical isolates of yeasts and filamentous fungi. A total of 1,997 clinical isolates of Candida spp., 359 of other yeast species, 697 strains of Aspergillus spp., and 325 nondermatophyte non-Aspergillus spp. were included. The average geometric means of the MICs of agents that were tested against Candida spp. were 0.23 microg/ml for amphotericin B, 0.29 microg/ml for flucytosine, 0.97 microg/ml for fluconazole, 0.07 microg/ml for itraconazole, 0.04 microg/ml for voriconazole, 0.15 microg/ml for caspofungin, and 0.03 microg/ml for posaconazole. Voriconazole and posaconazole were active in vitro against the majority of isolates, with resistance to fluconazole and itraconazole, and against Cryptococcus neoformans and other Basidiomycota yeasts. Posaconazole was the most active of antifungal agents tested against Aspergillus spp., with an average geometric mean of 0.10 microg/ml. It was active against Paecilomyces spp., Penicillium spp., Scedosporium apiospermum, and some black fungi, such as Alternaria spp. Multiresistant filamentous fungi, such as Scedosporium prolificans, Scopulariopsis brevicaulis, and Fusarium solani, were also resistant to voriconazole, caspofungin, and posaconazole. Amphotericin B and posaconazole were found to be active against most of the Mucorales strains tested. Posaconazole and currently available antifungal agents exhibit a potent activity in vitro against the majority of pathogenic fungal species.     

Bench-to-bedside review: <Emphasis Type="Italic">Candida</Emphasis> infections in the intensive care unit

Invasive mycoses are life-threatening opportunistic infections and have emerged as a major cause of morbidity and mortality in critically ill patients. This review focuses on recent advances in our understanding of the epidemiology, diagnosis and management of invasive candidiasis, which is the predominant fungal infection in the intensive care unit setting. Candida spp. are the fourth most common cause of bloodstream infections in the USA, but they are a much less common cause of bloodstream infections in Europe. About one-third of episodes of candidaemia occur in the intensive care unit. Until recently, Candida albicans was by far the predominant species, causing up to two-thirds of all cases of invasive candidiasis. However, a shift toward non-albicans Candida spp., such as C. glabrata and C. krusei, with reduced susceptibility to commonly used antifungal agents, was recently observed. Unfortunately, risk factors and clinical manifestations of candidiasis are not specific, and conventional culture methods such as blood culture systems lack sensitivity. Recent studies have shown that detection of circulating β-glucan, mannan and antimannan antibodies may contribute to diagnosis of invasive candidiasis. Early initiation of appropriate antifungal therapy is essential for reducing the morbidity and mortality of invasive fungal infections. For decades, amphotericin B deoxycholate has been the standard therapy, but it is often poorly tolerated and associated with infusion-related acute reactions and nephrotoxicity. Azoles such as fluconazole and itraconazole provided the first treatment alternatives to amphotericin B for candidiasis. In recent years, several new antifungal agents have become available, offering additional therapeutic options for the management of Candida infections. These include lipid formulations of amphotericin B, new azoles (voriconazole and posaconazole) and echinocandins (caspofungin, micafungin and anidulafungin).     

Echinocandin and triazole antifungal susceptibility profiles for Candida spp., Cryptococcus neoformans, and Aspergillus fumigatus: application of new CLSI clinical breakpoints and epidemiologic cutoff values to characterize resistance in the SENTRY Antimicrobial Surveillance Program (2009)

The SENTRY Antimicrobial Surveillance Program monitors global susceptibility and resistance rates for newer and established antifungal agents. The echinocandins displayed excellent potency against both Candida spp. and Aspergillus fumigatus in 2009 samples. Using the new Clinical and Laboratory Standards Institute breakpoint values for the echinocandins when testing Candida spp., we demonstrate low but measurable rates of resistance to all 3 echinocandins (anidulafungin, caspofungin, and micafungin) when tested against Candida glabrata. Three of the 8 isolates demonstrating in vitro echinocandin resistance harbored fks resistance mutations, including 1 C. glabrata. The triazoles, with the exception of itraconazole, also exhibited excellent potency and low levels of resistance when tested against clinical isolates of Candida spp., Cryptococcus neoformans, and A. fumigatus. Overall, echinocandin and triazole resistance rates were minimal; however, the distinct increase in echinocandin resistance observed among C. glabrata strains warrants further surveillance associated with molecular support.     

Micafungin: the US perspective

Invasive fungal infections cause considerable morbidity and mortality in nosocomial settings and amongst immunocompromised hosts. Invasive candidiasis and aspergillosis remain the most common invasive fungal infections, with Candida spp. constituting the fourth most common bloodstream infection in the USA. Currently available antifungal therapies include the polyene, antimetabolite, allylamine, azole and echinocandin drug classes. Micafungin, approved in March 2005 by the Food and Drug Administration for use in the USA, has shown safety and efficacy for the treatment of candidiasis and aspergillosis in clinical trials in Japan, Europe and South Africa. Micafungin holds promise as a first-line treatment option for candidiasis, as well as prophylaxis against invasive fungal infections during periods of neutropenia in high-risk patients.     

Echinocandin antifungals: review and update

The echinocandins are a new and unique class of antifungal agents that act on the fungal cell wall by way of noncompetitive inhibition of the synthesis of 1,3-β-glucans. All agents of this class are of parenteral formulation, with no oral preparations available. Caspofungin (Cancidas^®) was the first approved echinocandin, followed recently by micafungin (Mycamine^®) and anidulafungin (Eraxis^®). The precise role of the echinocandins in the antifungal armamentarium is still unfolding. Caspofungin is approved for the treatment of candidal esophagitis and candidemia, salvage therapy of Aspergillus infections and for empirical therapy of febrile neutropenia. Micafungin is likewise approved for candidal esophagitis, in addition to antifungal prophylaxis for hematopoietic stem cell transplant recipients. Anidulafungin is also approved for treatment of candidal esophagitis, as well as therapy of candidemia. There has been anecdotal use of these agents to treat less common fungal pathogens, as well as limited use as a component of combination antifungal therapy. The echinocandins are an important addition to the antifungal armamentarium in the treatment of fungal infections in both immunocompromised patients and those with normal immunity.