Echinocandins in children

Usage of Antifungal Agents in Pediatric Patients Versus Adults: Knowledge and Gaps

Invasive fungal infections (IFIs) present significant challenges in managing hospitalized and immunocompromised pediatric patients, contributing to high morbidity and mortality. Despite advancements in diagnostics and treatment, outcomes remain suboptimal due to unique clinical epidemiology, lack of pediatric-specific trials, and varied pharmacokinetics. The emergence of new antifungal classes and agents has expanded our options for preventing and treating IFIs in children, enhancing the safety and effectiveness of antifungal therapy. The oral formulations of ibrexafungerp, fosmanogepix and olorofim along with the extended dosing intervals of rezafungin show promising features for effective antifungal treatment in pediatrics. Despite the promising potential of novel antifungal drugs, their performance in heavily immunosuppressed patients remains unstudied. Until then, dedicated antifungal stewardship programs for high-risk patients are essential to optimize therapeutic outcomes, improve patient care, and limit the emergence of resistance.

Antifungal Drug-Drug Interactions with Commonly Used Pharmaceutics in European Pediatric Patients with Acute Lymphoblastic Leukemia

Leukemia is one of the leading childhood malignancies, with acute lymphoblastic leukemia (ALL) being the most common type. Invasive fungal disease is a concerning problem also at pediatric hemato-oncology units. Available guidelines underline the need for antifungal prophylaxis and give recommendations for proper treatment in various clinical scenarios. Nonetheless, antifungal agents are often involved in drug-drug interaction (DDI) occurrence. The prediction of those interactions in the pediatric population is complicated because of the physiological differences in adults, and the lack of pharmacological data. In this review, we discuss the potential DDIs between antifungal agents and commonly used pharmaceutics in pediatric hemato-oncology settings, with special emphasis on the use of liposomal amphotericin B and ALL treatment. We obtained information from Micromedex^® and Drugs.com^® interaction checking databases and checked the EudraVigilance^® database to source the frequency of severe adverse drug reactions that resulted from antifungal drug interactions. Several major DDIs were identified, showing a favorable safety profile of echinocandins and liposomal amphotericin B. Interestingly, although there are numerous available drug interaction checking tools facilitating the identification of potential serious DDIs, it is important to use more than one tool, as the presented searching results may differ between particular checking programs.

Echinocandins - structure, mechanism of action and use in antifungal therapy

With increasing number of immunocompromised patients as well as drug resistance in fungi, the risk of fatal fungal infections in humans increases as well. The action of echinocandins is based on the inhibition of β-(1,3)-d-glucan synthesis that builds the fungal cell wall. Caspofungin, micafungin, anidulafungin and rezafungin are semi-synthetic cyclic lipopeptides. Their specific chemical structure possess a potential to obtain novel derivatives with better pharmacological properties resulting in more effective treatment, especially in infections caused by Candida and Aspergillus species. In this review we summarise information about echinocandins with closer look on their chemical structure, mechanism of action, drug resistance and usage in clinical practice. We also introduce actual trends in modification of this antifungals as well as new methods of their administration, and additional use in viral and bacterial infections.

Pharmacokinetic, efficacy, and safety considerations for the use of antifungal drugs in the neonatal population

INTRODUCTION

Invasive fungal infections are an important cause of morbidity and mortality in infants, particularly in extreme prematurity. Successful systemic treatment requires consideration of antifungal efficacy, safety, and pharmacokinetics, including optimization of dosing in this population.

AREAS COVERED

This review summarizes published pharmacokinetic data on four classes of antifungal agents used in the neonatal population. Alterations in absorption, distribution, drug metabolism and clearance in infants compared to adult populations are highlighted. Additionally, pharmacodynamics, safety, and therapeutic drug monitoring are discussed. Recent advancements in neonatal antifungal pharmacotherapies are examined, with emphasis on clinical application.

EXPERT OPINION

Over the last two decades, published studies have provided increased knowledge on pharmacokinetic considerations in the neonatal population. Future research should focus on filling in the knowledge gaps that remain regarding the benefits and risks of combination antifungal therapy, the rising use of micafungin for invasive candidiasis given its fungicidal activity against polyene and azole-resistant Candida species and its minimal adverse effect profile, and the need for pharmacokinetic and safety data of broad spectrum triazoles, like voriconazole and posaconazole, in infants. Furthermore, efforts should focus on well-designed trials, including population pharmacokinetic studies, to develop dosing recommendations with subsequent implementation into clinical practice.

Review on Current Status of Echinocandins Use

Fungal infections are rising all over the world every year. There are only five medical compound classes for treatment: triazoles, echinocandins, polyenes, flucytosine and allylamine. Currently, echinocandins are the most important compounds, because of their wide activity spectrum and much lower sides effects that may occur during therapy with other drugs. Echinocandins are secondary metabolites of fungi, which can inhibit the biosynthesis of β-(1,3)-D-glucan. These compounds have fungicidal and fungistatic activity depending on different genera of fungi, against which they are used. Echinocandin resistance is rare—the major cause of resistance is mutations in the gene encoding the β-(1,3)-D-glucan synthase enzyme. In this review of the literature we have summarized the characteristics of echinocandins, the mechanism of their antifungal activity with pharmacokinetics and pharmacodynamics, and the resistance issue.

Use of Micafungin for the Prevention and Treatment of Invasive Fungal Infections in Everyday Pediatric Care in France: Results of the MYRIADE Study

BACKGROUND

Invasive fungal infections are responsible for significant morbidity and mortality. Safety and effectiveness of antifungal agents is a particular concern in pediatric populations, where data are often limited. Micafungin is an echinocandin with demonstrated antifungal activity against a wide spectrum of Candida spp.; this subanalysis of data from the MYRIADE study describes the use of micafungin and its therapeutic outcomes in pediatric patients, in normal clinical practice.

METHODS

MYRIADE was an observational, multicenter, national, prospective, longitudinal study conducted from January 2010 to December 2012, in patients treated with micafungin using a prophylactic or curative strategy, across 17 sites [oncohematology (n = 8), neonatal intensive care units (ICUs) (n = 5) and pediatric ICUs (n = 4)]. The treatment regimen, the achievement of the therapeutic objective and the tolerance were reported.

RESULTS

The study population consisted of 110 pediatric patients (31 neonates, 24 children <2 years old and 55 children ≥2 to <16 years old). The therapeutic objective was achieved in 49/64 (76.6%) oncohematology patients, 28/29 (96.6%) neonatal ICU patients and 12/14 (85.7%) pediatric ICU patients. Twenty-four (21.8%) children developed an adverse event (AE); more AEs were observed in oncohematology patients compared with ICU patients [17 (26.1%) vs. 7 (15.6%)]. Only one serious AE, reported in an oncohematology patient, was considered related to micafungin.

CONCLUSIONS

In the first large observational study of micafungin treatment or prophylaxis conducted under real-world conditions in France, micafungin was effective and well tolerated for prophylaxis of invasive fungal infections in pediatric oncohematology patients and for curative purposes in pediatric and neonatal ICU patients.

The Role of Antifungals in Pediatric Critical Care Invasive Fungal Infections

Invasive fungal infections (IFIs) have seen considerable increase in pediatric intensive care units over the past several decades. IFIs are predominantly caused by Candida species, and candidemia is the third most common cause of healthcare-associated bloodstream infections (BSIs) in children. IFIs are opportunistic infections that affect pediatric patients in critical care resulting in significant morbidity and mortality especially in those with a compromised immune system. IFIs are the leading cause of death in children with comorbidities such as immunosuppression, and pediatric ICU admission has been shown to be an independent risk factor for mortality. Management of IFI and fungal sepsis is broad and encompasses several key components that include prompt initiation of therapy and rapid source identification and control. This study reviews important antifungals in the pediatric critical care setting including the pharmacologic properties, antifungal spectrum, adverse effects, and clinical uses of agents belonging to the four major classes of antifungals—the polyenes, azoles, echinocandins, and pyrimidine analogue flucytosine. The polyenes and azoles are the most often used classes of antifungals. The echinocandins are a relatively newer class of antifungal agents that offer excellent Candida activity and are currently recommended as the first-line therapy for invasive candidiasis.

Echinocandin prophylaxis in patients undergoing haematopoietic cell transplantation and other treatments for haematological malignancies

Antifungal prophylaxis is the standard of care for patients undergoing intensive chemotherapy for haematological malignancy or haematopoietic cell transplantation (HCT). Prophylaxis with azoles reduces invasive fungal infections and may reduce mortality. However, breakthrough infections still occur, and the use of azoles is sometimes complicated by pharmacokinetic variability, drug interactions, adverse events and other issues. Echinocandins are highly active against Candida species, including some organisms resistant to azoles, and have some clinical activity against Aspergillus species as well. Although currently approved echinocandins require daily intravenous administration, the drugs have a favourable safety profile and more predictable pharmacokinetics than mould-active azoles. Clinical data support the efficacy and safety of echinocandins for antifungal prophylaxis in haematology and HCT patients, though data are less robust than for azoles. Notably, sparse evidence exists supporting the use of echinocandins as antifungal prophylaxis for patients with significant graft-versus-host disease (GvHD) after HCT. Two drugs that target (1,3)-β-d-glucan are in development, including an oral glucan synthase inhibitor and an echinocandin with unique pharmacokinetics permitting subcutaneous and weekly administration. Echinocandins are a reasonable alternative to azoles and other agents for antifungal prophylaxis in patients undergoing intensive chemotherapy for haematological malignancy or those receiving HCT, excluding those with significant GvHD.

Echinocandins: The Expanding Antifungal Armamentarium

The echinocandins are large lipopeptide molecules that, since their discovery approximately 41 years ago, have emerged as important additions to the expanding armamentarium against invasive fungal diseases. Echinocandins exert in vitro and in vivo fungicidal action against most Candida species and fungistatic action against Aspergillus species. However, the population of patients at risk for developing invasive fungal infections continues to increase. New therapeutic strategies using echinocandins are needed to improve clinical outcomes in patients with invasive fungal disease.

Development of New Strategies for Echinocandins: Progress in Translational Research

Echinocandins are N-acyl-substituted cyclic hexapeptides with potent in vitro and in vivo activity against Candida species that are used for primary treatment and prevention of candidemia and invasive candidiasis. Recent progress in the translational research of echinocandins has led to new approaches for treatment of central venous catheter Candida biofilms. Other studies have laid the experimental and clinical foundation for use of extended dosing intervals for administration of echinocandins in treatment and prevention of candidemia and invasive candidiasis.

Pharmacokinetics and pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

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.