Micafungin: a review of its use in the prophylaxis and treatment of invasive Candida infections in pediatric patients

Assessment of micafungin dosage regimens against Candida spp. in pediatric patients undergoing hematopoietic stem cell transplantation: a pharmacokinetic/pharmacodynamic analysis using Monte Carlo simulation

The objective of this study was to evaluate the efficacy of various micafungin dosing regimens against Candida spp. in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT). Monte Carlo simulations were conducted using pharmacokinetic (PK) parameters and pharmacodynamic (PD) data to determine the probabilities of target attainment and cumulative fractions of response in terms of area under the concentration curve/minimum inhibition concentration targets of micafungin. Current standard clinical micafungin dosing regimens of 1 and 2 mg/kg/day were appropriate for the prevention and treatment of Candida glabrata infection in pediatric patients undergoing HSCT, respectively. Moreover, the high-dose prophylactic dosage (2 mg/kg/day) and therapeutic dosage (4 mg/kg/day) should be the preferred option to optimize efficacy against Candida albicans. However, none of the simulated regimens was effective against Candida parapsilosis in pediatric HSCT patients. These PK/PD-based simulations rationalize and optimize the micafungin dosing regimens against Candida spp. in pediatric patients undergoing HSCT.

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.

Effects of methyl oleate and microparticle-enhanced cultivation on echinocandin B fermentation titer

Echinocandin B (ECB) is a key precursor of antifungal agent Anidulafungin, which has demonstrated clinical efficacy in patients with invasive candidiasis. In this study, the effects of microparticle-enhanced cultivation and methyl oleate on echinocandin B fermentation titer were investigated. The results showed that the titer was significantly influenced by the morphological type of mycelium, and mycelium pellet was beneficial to improve the titer of this secondary metabolism. First, different carbon sources were chosen for the fermentation, and methyl oleate achieved the highest echinocandin B titer of 2133 ± 50 mg/L, which was two times higher than that of the mannitol. The study further investigated the metabolic process of the fermentation, and the results showed that L-threonine concentration inside the cell could reach 275 mg/L at 168 h with methyl oleate, about 2.5 times higher than that of the mannitol. Therefore, L-threonine may be a key precursor of echinocandin B. In the end, a new method of adding microparticles for improving the mycelial morphology was used, and the addition of talcum powder (20 g/L, diameter of 45 µm) could make the maximum titer of echinocandin B reach 3148 ± 100 mg/L.

Micafungin: A Review in the Prophylaxis and Treatment of Invasive Candida Infections in Paediatric Patients

Intravenous micafungin (Mycamine^®; Funguard^®), an echinocandin, is approved in the EU for the treatment of invasive candidiasis in children (including neonates) and adolescents (<16 years of age) and as prophylaxis against Candida infections in patients undergoing haematopoietic stem cell transplantation (HSCT) or who are expected to have neutropenia for ≥10 days. This narrative review focuses on the use of micafungin in paediatric indications approved in the EU, which may vary from those approved elsewhere in the world. Micafungin has a broad spectrum of in vitro activity against clinically relevant isolates of Candida spp. (including fluconazole-resistant Candida glabrata isolates), a low propensity for emergence of resistant isolates and a convenient once-daily regimen. In paediatric substudies and a small multinational, phase 3 trial in neonates with proven invasive candidiasis, intravenous micafungin was effective and generally well tolerated in the treatment of candidaemia and other types of invasive candidiasis and as prophylaxis against fungal infections in patients undergoing HSCT. Hence, micafungin remains an important option for the prophylaxis and treatment of invasive Candida infections in paediatric and adult patients.

Pharmacokinetic and safety profiles of repeated-dose prophylactic micafungin in children and adolescents undergoing hematopoietic stem cell transplantation

Micafungin is a potent echinocandin antifungal that can be used for both prophylaxis and treatment of Candida infections. This open-label study assessed the pharmacokinetics and safety profile of prophylactic micafungin in children and adolescents (aged 4 mo to 16 y) undergoing hematopoietic stem cell transplantation. Patients received once-daily doses of either 1 or 1.5 mg/kg micafungin, based on their body weight, for 10 to 14 days. In total, 40 patients received micafungin. Area under the plasma micafungin concentration-time curve was highest in patients aged 6 to 11 years in the 1.5 mg/kg treatment group. Peak plasma micafungin concentration displayed no age-related differences, but was higher in the 1.5 mg/kg versus the 1 mg/kg group. Clearance at steady state by weight and volume of distribution by weight were considerably higher in patients aged 4 months to 5 years. Results from this study show that age and body weight affect micafungin pharmacokinetics in pediatric patients undergoing hematopoietic stem cell transplantation.

Antifungal therapy in children: an update

Invasive fungal infections are a common problem in children affected by primary or secondary immunodeficiencies. Thanks to an increased knowledge about their mechanisms of action and their pharmacokinetic and toxicity profiles, the use of these drugs in common and uncommon invasive infections in immunocompromised children has improved over the last decades. Choosing the most appropriate antifungal drug is a serious challenge for any clinician, also considering that, in most cases, therapy has to be started before cultures are available, the choice being driven by clinical symptoms and statistical criteria only. In this study, we performed a systematic review of literature, providing antifungal treatment recommendations for paediatric patients which can help clinicians find the most suitable treatment for each specific case. Principal antifungal drugs-ranging from first-generation antimycotics to the latest molecules-are classified according to their targets, and of each group, the pharmacokinetic profile, clinical indications and side effects are extensively described.

Structure-activity relationship for FDA approved drugs as inhibitors of the human sodium taurocholate cotransporting polypeptide (NTCP)

The hepatic bile acid uptake transporter sodium taurocholate cotransporting polypeptide (NTCP) is less well characterized than its ileal paralog, the apical sodium dependent bile acid transporter (ASBT), in terms of drug inhibition requirements. The objectives of this study were (a) to identify FDA approved drugs that inhibit human NTCP, (b) to develop pharmacophore and Bayesian computational models for NTCP inhibition, and (c) to compare NTCP and ASBT transport inhibition requirements. A series of NTCP inhibition studies were performed using FDA approved drugs, in concert with iterative computational model development. Screening studies identified 27 drugs as novel NTCP inhibitors, including irbesartan (Ki = 11.9 μM) and ezetimibe (Ki = 25.0 μM). The common feature pharmacophore indicated that two hydrophobes and one hydrogen bond acceptor were important for inhibition of NTCP. From 72 drugs screened in vitro, a total of 31 drugs inhibited NTCP, while 51 drugs (i.e., more than half) inhibited ASBT. Hence, while there was inhibitor overlap, ASBT unexpectedly was more permissive to drug inhibition than was NTCP, and this may be related to NTCP possessing fewer pharmacophore features. Findings reflected that a combination of computational and in vitro approaches enriched the understanding of these poorly characterized transporters and yielded additional chemical probes for possible drug-transporter interaction determinations.

[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.

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

Invasive fungal infections are a major cause of morbidity and mortality in children with hematological malignancies and those undergoing allogeneic hematopoietic stem-cell transplantation (HSCT). Although several new antifungal compounds recently became available, some are not yet approved for the use in the pediatric population. Among the new class of echinocandins, micafungin has been licensed in Europe and Japan for children including neonates. Because micafungin is well tolerated and exhibits few clinical relevant drug-drug interactions, the compound is of particular interest for prophylaxis and treatment of invasive mycoses in pediatric patients with cancer or following allogeneic HSCT. This review will focus on the currently available pediatric data of micafungin with emphasis on pharmacokinetics, efficacy, and safety.