Micafungin: a brief review of pharmacology, safety, and antifungal efficacy in pediatric patients

Comparison of Efficacy and Safety of Caspofungin Versus Micafungin in Pediatric Allogeneic Stem Cell Transplant Recipients: A Retrospective Analysis

INTRODUCTION

The high morbidity and mortality associated with invasive fungal infections (IFIs) provide the rationale for antifungal prophylaxis in immuno-compromised pediatric patients undergoing hematopoietic stem cell transplantation (HSCT). Caspofungin and micafungin are antifungal agents of interest for prophylaxis of IFIs because of their potency against Candida and minimal toxicity or interactions with other drugs. Few studies have demonstrated the safety and efficacy of such echinocandins as prophylaxis for IFIs in patients undergoing HSCT.

METHODS

This retrospective cohort study compared caspofungin and micafungin for prevention of IFIs in 93 pediatric patients undergoing HSCT for oncological or non-oncological disease. The observation began with the first dose of antifungal agent and ended 3 months after transplantation.

RESULTS

Patients in the micafungin group had a higher overall treatment success rate of 87.2 versus 84.8% in the caspofungin group, but the difference was not significant. There were no statistically significant differences in the incidence or type of proven/probable IFIs between the 2 groups. The low incidence of death did not differ statistically between the groups. Patients in the caspofungin group presented more frequently with fever, during and after neutropenia. In both groups, we observed an expected worsening of blood chemistry parameters. There were no adverse events definitely attributable to the two antifungal agents.

CONCLUSION

These results demonstrate good efficacy and tolerability for caspofungin and micafungin. However, better results with respect to the incidence and resolution of fever in the micafungin group may suggest its use in preference to that of caspofungin.

Safety and Efficacy of Intermittent Intravenous Administration of High-Dose Micafungin

BACKGROUND

The use of mold-active azoles for antifungal prophylaxis after allogeneic stem cell transplantation (SCT) is hindered by adverse events and drug-drug interactions. Higher doses of echinocandins administered intermittently may be an alternative in this setting.

METHODS

This was a single-center, observational 5-year study to characterize the safety and efficacy of intermittent administration of high-dose intravenous micafungin (≥5 doses of ≥300 mg micafungin 2-3 times weekly) in patients with acute leukemia and allogeneic SCT recipients.

RESULTS

A total of 104 patients (84 allogeneic SCT recipients and 20 patients with leukemia) received intermittent high-dose intravenous micafungin, 83 (79.8%) as prophylaxis. Large variability in the micafungin dosing regimen was observed; 78 (75%) patients received >75% of their course as 300 mg micafungin 3 times weekly. Liver function tests decreased from baseline to end of treatment (EOT; P < .001). Patients with normal baseline liver function (n = 55 [52%]) maintained similar enzyme levels throughout the study. For patients with abnormal baseline liver function (n = 49 [47%]), liver function tests significantly improved from baseline to EOT (P ≤ .005). Duration and/or micafungin dosing algorithms were not associated with liver toxicity at EOT. There were no significant changes in renal function, and infusion-related reactions or deaths were not observed. Five of 83 (6.0%) patients in the prophylaxis group developed a breakthrough fungal infection.

CONCLUSIONS

In this largest cohort of patients to date, intermittent administration of high-dose micafungin was well tolerated, without any associated liver or renal function abnormalities, and may be considered an alternative antifungal prophylactic strategy. Prospective studies are needed to further validate these findings.

Improvement of overall survival after allogeneic hematopoietic stem cell transplantation for children and adolescents: a three-decade experience of a single institution

Allogeneic stem cell transplantation (allo-SCT) has become an essential component of the treatment for a variety of diseases in pediatric patients. During the past decades, advances in the transplant technology, availability of hematopoietic stem cells and supportive care not only have resulted in improved outcomes, but also have expanded the transplant options. However, these features have been studied mainly in adult populations. This investigation analyzed changes in patient profile, transplantation, graft characteristics and outcome among 250 children and adolescent patients who received allo-SCT in a single center between 1983 and 2010. In the 2000-2010, compared with the 1983-1999 period, a significantly higher 5-year overall survival (64% versus 52%, P=0.03) was observed together with a significant decrease of non-relapse mortality (27% versus 9%, P=0.0002). The progression-free survival was comparable between the two periods (49% versus 57%; P=0.17). The 5-year cumulative incidence of relapse was 24% between 1983 and 1999, and 34% between 2000 and 2010 (P=0.08). Major advances in supportive care practice have been made over the past decade, resulting in a significant survival benefit for the pediatric population undergoing allo-SCT. However, post-transplant relapse remains the leading cause of failure of this therapeutic approach, and preventing relapse represents a major challenge today.

Safety of high-dose micafungin for patients with hematological diseases

This study was conducted as a retrospective, observational, exploratory cohort study with the aim of elucidating the safety profile of micafungin at doses exceeding 150 mg daily. We identified adult patients with hematological diseases who had received micafungin therapy for ≥ 7 consecutive days. Twenty-six patients administered micafungin at 300 mg daily (high-dose group) were compared with 58 patients administered micafungin at 150 mg daily (standard-dose group). The most frequent adverse events (AEs) were hepatotoxicity, hypertension and diarrhea. AEs were recorded in 42 (72%) and 19 (73%) patients in the standard-dose and high-dose groups, respectively (p = 1.00). Hepatobiliary AEs were noted in 28 (48%) and 15 (58%) patients, respectively (p = 0.48). Serious AEs and resultant treatment discontinuation were infrequent. Our results suggest that micafungin was safe and well tolerated at 300 mg daily.

Brazilian guidelines for the management of candidiasis - a joint meeting report of three medical societies: Sociedade Brasileira de Infectologia, Sociedade Paulista de Infectologia and Sociedade Brasileira de Medicina Tropical

Candida infections account for 80% of all fungal infections in the hospital environment, including bloodstream, urinary tract and surgical site infections. Bloodstream infections are now a major challenge for tertiary hospitals worldwide due to their high prevalence and mortality rates. The incidence of candidemia in tertiary public hospitals in Brazil is approximately 2.5 cases per 1000 hospital admissions. Due to the importance of this infection, the authors provide a review of the diversity of the genus Candida and its clinical relevance, the therapeutic options and discuss the treatment of major infections caused by Candida. Each topography is discussed with regard to epidemiological, clinical and laboratory diagnostic and therapeutic recommendations based on levels of evidence.

Newer antifungal agents

PURPOSE OF REVIEW

In recent years there has been an evolution of a better understanding of the pharmacology and clinical indications of existing antifungal agents and also the development of new broad-spectrum triazoles and a newer class of antifungal agents, the echinocandins. The availability of these agents has broadened the therapeutic options of invasive fungal disease among children and consequently antifungal therapy has become increasingly complex.

RECENT FINDINGS

Adoption of adult guidelines' recommendations has been used to guide pediatric treatment as specific pediatric data were often lacking. This approach has not always selected the most appropriate therapy for newborns or young infants, as the under-dosage of voriconazole based on adult data revealed. Therefore, a detailed understanding of the available antifungal agents in children is crucial for the successful treatment of these serious infections.

SUMMARY

In this review we summarize the main findings regarding antifungal treatment among children that have been recently published, focusing on the pharmacology and pediatric use of newer antifungal agents.

Novel dendrimeric lipopeptides with antifungal activity

A series of new cationic lipopeptides containing branched, amphiphilic polar head derived from (Lys)Lys(Lys) dendron and C(8) or C(12) chain at C-end were designed, synthesized and characterized. Antimicrobial in vitro activity expressed as minimal inhibitory concentration (MIC) was evaluated against Gram-positive and Gram-negative bacteria and yeasts from the Candida genus. A significant enhancement of antimicrobial potency along with increased selectivity against Candida reference strains was detected for derivatives with the C(12) residue. Several compounds were characterized by a low hemotoxicity. The antifungal activity of branched lipopeptides is multimodal and concentration dependent. Several compounds, studied in detail, induced potassium leakage from fungal cells, caused morphological alterations of fungal cells and inhibited activity of candidal β(1,3)-glucan synthase.

Current perspectives on echinocandin class drugs

It has been nearly a decade since caspofungin was approved for clinical use as the first echinocandin class antifungal agent, followed by micafungin and anidulafungin. The echinocandin drugs target the fungal cell wall by inhibiting the synthesis of β-1,3-D-glucan, a critical cell wall component of many pathogenic fungi. They are fungicidal for Candida spp. and fungistatic for moulds, such as Aspergillus fumigatus, where they induce abnormal morphology and growth properties. The echinocandins have a limited antifungal spectrum but are highly active against most Candida spp., including azole-resistant strains and biofilms. As they target glucan synthase, an enzyme absent in mammalian cells, the echinocandins have a favorable safety profile. They show potent MIC and epidemiological cutoff values against susceptible Candida and Aspergillus isolates, and the frequency of resistance is low. When clinical breakthrough occurs, it is associated with high MIC values and mutations in Fks subunits of glucan synthase, which can reduce the sensitivity of the enzyme to the drug by several thousand-fold. Such strains were not adequately captured by an early clinical breakpoint for susceptibility prompting a revised lower value, which addresses the FKS resistance mechanism and new pharmacokinetic/pharmacodynamic studies. Elevated MIC values unlinked to therapeutic failure can occur and result from adaptive cell behavior, which is FKS-independent and involves the molecular chaperone Hsp90 and the calcineurin pathway. Mutations in FKS1 and/or FKS2 alter the kinetic properties of glucan synthase, which reduces the relative fitness of mutant strains causing them to be less pathogenic. The echinocandin drugs also modify the cell wall architecture exposing buried glucans, which in turn induce a variety of important host immune responses. Finally, the future for glucan synthase inhibitors looks bright with the development of new orally active compounds.

[Why might micafungin be the drug of choice in pediatric patients?]

Micafungin is an echinocandin approved by the European Medicines Evaluation Agency for the treatment of invasive candidiasis in children, including premature infants born before 29 weeks of pregnancy, and as prophylaxis in children undergoing hematopoietic stem-cell transplantation or patients at risk of prolonged neutropenia. This drug has good activity in several Candida spp., including those resistant to fluconazole. Although micafungin is active against Aspergillus spp., it has been used mainly in combination therapy for invasive aspergillosis. There is ample information on the use of micafungin in children, including neonates, and this drug is the only echinocandin approved for use in infants aged less than 3 months. The efficacy, pharmacokinetics and safety of micafungin have been evaluated in phase II and III clinical trials in children, in which its efficacy and safety were demonstrated in comparison with liposomal amphotericin B and fluconazole. The pharmacokinetic profile of micafungin in children allows once daily intravenous administration, with greater clearance than in adults, and consequently pediatric doses are relatively higher. The most appropriate dose in children weighing less than 40 kg is 2 mg/kg/day in the treatment of invasive candidiasis and 1 mg/kg/day as prophylaxis in children undergoing hematopoietic stem-cell transplantation. Doses in neonates should be higher. In premature infants, the most appropriate doses to achieve levels in the brain parenchyma are 7 mg/kg/day and 10 mg/kg/day in those weighing more and less than 1,000 g, respectively. Micafungin has few drug-drug interactions and an acceptable safety profile. Withdrawal of this drug due to adverse effects is rare, although transaminase monitoring is recommended during treatment, as well as evaluation of the risk-benefit balance in patients with liver disease or concomitant administration of hepatotoxic drugs.

[Liver toxicity of micafungin. Is this drug safe?]

Micafungin was commercialized in Japan in 2002 and has been used in more than 750,000 patients. As a member of the candin family, the drug's clinical and analytical tolerability is very good, both in adults and in children, including neonates. In this latter population, micafungin is the most frequently used candin. The most common adverse effects are nausea and elevated transaminase levels. Preclinical studies showed the development of benign liver tumors in rats treated with extremely high doses of the drug for prolonged periods. These data were not reproduced in other species and no cases have been reported in humans.

[Echinocandins in children]

Echinocandins are a new class of antifungal agents with a specific mechanism of action. These drugs inhibit the enzyme 1,3β-D-glucan synthetase which is responsible for the formation of 1,3β-D-glucan, an essential fungal cell wall component. They have a good activity against Candida species and Aspergillus. Three agents are available at the present time or under development : caspofungin, micafungin and anidulafungin. These drugs require intravenous administration. Efficacy, safety, rare drugs interactions and specificity of action are advantages for therapy of invasive fungal infections. In France, micafungin and caspofungin are approved for a pediatric use.

Invasive Candida infections in solid organ transplant recipient children

Solid organ transplantation (SOT) is now an accepted therapy for many end-stage organ disorders and fungal infections are the principal cause of infection-related mortality in SOT recipients. Among invasive fungal infections, Candida species are the most common pathogens identified, associated with high mortality rates. The epidemiology and clinical manifestations of Candida infections vary with the type of organ transplantation. This article reviews invasive Candida infections in pediatric SOT recipients.