Variability and exposure-response relationships of isavuconazole plasma concentrations in the Phase 3 SECURE trial of patients with invasive mould diseases

Lower blood levels of isavuconazole in critically ill patients compared with other populations: possible need for therapeutic drug monitoring

BACKGROUND

Isavuconazole is first-line treatment of invasive aspergillosis. Therapeutic drug monitoring (TDM) is deemed not necessary, since most patients reached therapeutic levels (>1 mg/L) in large studies. Low levels were reported in some critically ill patients admitted to the ICU. The aim was to compare isavuconazole levels between critically ill and non-critically ill patients.

MATERIALS AND METHODS

Retrospective analysis of data from all patients treated with standard-dose isavuconazole between 1 January 2019 and 26 October 2022 was performed. The following data were collected: TDM results from the first 30 days of therapy; ward of admission; demographic and clinical characteristics; continuous renal replacement therapy; extracorporeal membrane oxygenation; and co-administered drugs.

RESULTS

Seventy-two patients (median age 65 years) and 188 TDM measurements (mean number of samples per patient 2.6 ± 1.7) were included; 33 (45.8%) were ICU patients (3 also had haematological disorders); 39 (54.2%) were non-ICU patients, of whom 31 had haematological disorders. In all patients, the mean isavuconazole blood level was 3.33 ± 2.26 mg/L. Significantly lower levels were observed in the ICU versus the non-ICU population: mean 2.02 ± 1.22 versus 4.15 ± 2.31 mg/L (P < 0.001). Significantly higher rates of subtherapeutic levels were observed in ICU patients compared with the non-ICU population: all determinations <2 mg/L in 33.3% versus 7.7%, and all determinations <1 mg/L in 12.1% versus 0%, respectively. Predictors of lower isavuconazole levels were admission to the ICU, BMI > 25 kg/m2, bilirubin > 1.2 mg/dL and the absence of haematological disorder.

CONCLUSIONS

ICU patients had significantly lower isavuconazole blood levels compared to non-ICU population. The TDM of isavuconazole for efficacy should be performed in ICU.

Antifungal Therapies for Aspergillus spp.: Present and Future

Currently available and recommended options for the treatment of pulmonary aspergillosis include the triazoles, echinocandins, and amphotericin B products. These therapies have significant limitations. Only the azoles are available orally, but their use is often limited by toxicities, drug-drug interactions, pharmacokinetic variability, and emerging resistance. While the echinocandins are safe agents and may have a role in combination therapy, they are unproven as monotherapy. Amphotericin B preparations are toxic and require intensive monitoring. Finally, aspergillosis continues to be a disease conferring substantial morbidity and mortality, and clinical trials have not identified a therapeutic approach clearly associated with improved outcomes. As a result, there is a great need for new options in the treatment of invasive aspergillosis. Ideally, such options would be safe, have high oral bioavailability, have favorable pharmacokinetics to sequestered sites and retain activity against azole-resistant isolates. Reassuringly, there is a robust pipeline of novel therapies in development. Rezafungin (a once-weekly dosed echinocandin) and ibrexafungerp (oral agent with same mechanism of action as echinocandins) will likely be reserved for combination therapy or refractory/intolerance scenarios with no other options. Inhaled opelconazole is an attractive option for combination therapy and prophylaxis of pulmonary aspergillosis. Development of an oral form of amphotericin B that avoids nephrotoxicity and electrolyte disturbances is an exciting development. Finally, olorofim and fosmanogepix, two agents with novel mechanisms of action and oral formulations, hold significant potential to challenge the triazole antifungals place as preferred therapies. However, many questions remain regarding these novel agents, and at the time of this writing, none of these agents have been robustly studied in Phase III studies of aspergillosis, and so their promise remains investigational.

Early attainment of isavuconazole target concentration using an increased loading dose in critically ill patients with extracorporeal membrane oxygenation

BACKGROUND

In critically ill patients with extracorporeal membrane oxygenation (ECMO) attainment of target concentration of isavuconazole is delayed using the routine loading dose.

OBJECTIVES

We investigated the influence of increasing the first loading dose of isavuconazole on plasma concentrations in critically ill patients treated with ECMO.

METHODS

Fifteen patients were included in this study, and isavuconazole concentrations were measured at several timepoints starting 2 h after the first isavuconazole dose up to 168 h. By interim analysis of isavuconazole concentrations and meticulous screening for adverse events, the first loading dose was stepwise increased from 200 to 300 mg, and finally to 400 mg.

RESULTS

Seven of 15 patients (47%) received standard isavuconazole loading dosage with 200 mg as the first dose, 3/15 (20%) received 300 mg, and 5/15 (33%) received 400 mg isavuconazole as the first dose, followed by subsequent standard dosing in all patients. In patients receiving 400 mg as the first dose all isavuconazole concentrations were significantly higher at timepoints up to the first 24 h, resulting in higher proportions of isavuconazole concentrations ≥1 mg/L compared with patients with other loading dosages. In timepoints ≥24 h after isavuconazole initiation all patient groups reached comparable plasma concentrations, regardless of the first loading dose regimen. We did not observe concentrations above ≥5 mg/L or any adverse events related to isavuconazole administration.

CONCLUSIONS

In critically ill patients with ECMO the 400 mg loading dose of isavuconazole resulted in immediate median isavuconazole plasma concentrations ≥1 mg/L and remained constant above this threshold after the first loading dose.

Antimicrobials in patients with hematologic malignancies and recipients of hematopoietic cell transplantation and other cellular therapies

BACKGROUND

Appropriate use of antimicrobials for hematologic malignancy, hematopoietic stem cell transplant recipients, and other cellular therapies is vital, with infection causing significant morbidity and mortality in this unique population of immunocompromised hosts. However, often in this population the choice and management of antimicrobial therapy is complex. When selecting an antimicrobial agent, key considerations include the need for dose adjustments due to renal or hepatic impairment, managing drug interactions, the potential for additive drug toxicity among those receiving polypharmacy and therapeutic drug monitoring. Other factors include leveraging pharmacodynamic principles to enable optimization of directed therapy against challenging pathogens, as well as judicious use of antimicrobials to limit drug resistance and adverse drug reactions.

SUMMARY

This review summarizes the clinical considerations for commonly used antimicrobials in this setting, including antibacterial, antiviral, and antifungal agents.

Utility of triazole antifungal therapeutic drug monitoring: Insights from the Society of Infectious Diseases Pharmacists: Endorsed by the Mycoses Study Group Education and Research Consortium

Triazole antifungals (i.e., fluconazole, itraconazole, voriconazole, posaconazole, and isavuconazole) are commonly used in clinical practice to prevent or treat invasive fungal infections. Most triazole antifungals require therapeutic drug monitoring (TDM) due to highly variable pharmacokinetics, known drug interactions, and established relationships between exposure and response. On behalf of the Society of Infectious Diseases Pharmacists (SIDP), this insight describes the pharmacokinetic principles and pharmacodynamic targets of commonly used triazole antifungals and provides the rationale for utility of TDM within each agent.

Isavuconazole Exposure in Critically Ill Patients Treated with Extracorporeal Membrane Oxygenation: Two Case Reports and a Narrative Literature Review

Effective dosing of isavuconazole in patients supported by extracorporeal membrane oxygenation (ECMO) is important due to the role of isavuconazole as a first-line treatment in patients with influenza- and COVID-19-associated pulmonary aspergillosis. To date, robust pharmacokinetic data in patients supported by ECMO are limited. Therefore, it is unknown whether ECMO independently impacts isavuconazole exposure. We measured isavuconazole plasma concentrations in two patients supported by ECMO and estimated individual pharmacokinetic parameters using non-compartmental analysis and two previously published population pharmacokinetic models. Furthermore, a narrative literature review on isavuconazole exposure in adult patients receiving ECMO was performed. The 24 h areas under the concentration-time curve and trough concentrations of isavuconazole were lower in both patients compared with exposure values published before. In the literature, highly variable isavuconazole concentrations have been documented in patients with ECMO support. The independent effect of ECMO versus critical illness itself on isavuconazole exposure cannot be deduced from our and previously published (case) reports. Pending additional data, therapeutic drug monitoring is recommended in critically ill patients, regardless of ECMO support.

Epidemiology, Modern Diagnostics, and the Management of Mucorales Infections

Mucormycosis is an uncommon, yet deadly invasive fungal infection caused by the Mucorales moulds. These pathogens are a WHO-assigned high-priority pathogen group, as mucormycosis incidence is increasing, and there is unacceptably high mortality with current antifungal therapies. Current diagnostic methods have inadequate sensitivity and specificity and may have issues with accessibility or turnaround time. Patients with diabetes mellitus and immune compromise are predisposed to infection with these environmental fungi, but COVID-19 has established itself as a new risk factor. Mucorales also cause healthcare-associated outbreaks, and clusters associated with natural disasters have also been identified. Robust epidemiological surveillance into burden of disease, at-risk populations, and emerging pathogens is required. Emerging serological and molecular techniques may offer a faster route to diagnosis, while newly developed antifungal agents show promise in preliminary studies. Equitable access to these emerging diagnostic techniques and antifungal therapies will be key in identifying and treating mucormycosis, as delayed initiation of therapy is associated with higher mortality.

Clinical Features and Treatment Progress of Invasive Mucormycosis in Patients with Hematological Malignancies

The incidence rate of invasive mucormycosis (IM) in patients with hematological malignancies (HMs) is increasing year by year, ranging from 0.07% to 4.29%, and the mortality rate is mostly higher than 50%. With the ongoing pandemic of COVID-19, COVID-19-associated mucormycosis (CAM) also became a global health threat. Patients with high risk factors such as active HMs, relapsed/refractory leukemia, prolonged neutropenia may still develop breakthrough mucormycosis (BT-MCR) even under the prophylaxis of Mucorales-active antifungals, and such patients often have higher mortality. Rhizopus spp. is the most common genus associated with IM, followed by Mucor spp. and Lichtheimia spp. Pulmonary mucormycosis (PM) is the most common form of IM in patients with HMs, followed by rhino-orbital-cerebral mucormycosis (ROCM) and disseminated mucormycosis. The prognosis of IM patients with neutrophil recovery, localized IM and receiving early combined medical-surgical therapy is usually better. As for management of the disease, risk factors should be eliminated firstly. Liposome amphotericin B (L-AmB) combined with surgery is the initial treatment scheme of IM. Those who are intolerant to L-AmB can choose intravenous formulations or tablets of isavuconazole or posaconazole. Patients who are refractory to monotherapy can turn to combined antifungals therapy.

A Hybrid Algorithm Combining Population Pharmacokinetic and Machine Learning for Isavuconazole Exposure Prediction

OBJECTIVES

Maximum a posteriori Bayesian estimation (MAP-BE) based on a limited sampling strategy and a population pharmacokinetic (POPPK) model is used to estimate individual pharmacokinetic parameters. Recently, we proposed a methodology that combined population pharmacokinetic and machine learning (ML) to decrease the bias and imprecision in individual iohexol clearance prediction. The aim of this study was to confirm the previous results by developing a hybrid algorithm combining POPPK, MAP-BE and ML that accurately predicts isavuconazole clearance.

METHODS

A total of 1727 isavuconazole rich PK profiles were simulated using a POPPK model from the literature, and MAP-BE was used to estimate the clearance based on: (i) the full PK profiles (refCL); and (ii) C24h only (C24h-CL). Xgboost was trained to correct the error between refCL and C24h-CL in the training dataset (75%). C24h-CL as well as ML-corrected C24h-CL were evaluated in a testing dataset (25%) and then in a set of PK profiles simulated using another published POPPK model.

RESULTS

A strong decrease in mean predictive error (MPE%), imprecision (RMSE%) and the number of profiles outside ± 20% MPE% (n-out20%) was observed with the hybrid algorithm (decreased in MPE% by 95.8% and 85.6%; RMSE% by 69.5% and 69.0%; n-out20% by 97.4% and 100% in the training and testing sets, respectively. In the external validation set, the hybrid algorithm decreased MPE% by 96%, RMSE% by 68% and n-out20% by 100%.

CONCLUSION

The hybrid model proposed significantly improved isavuconazole AUC estimation over MAP-BE based on the sole C24h and may improve dose adjustment.

What Is New in Pulmonary Mucormycosis?

Mucormycosis is a rare but life-threatening fungal infection due to molds of the order Mucorales. The incidence has been increasing over recent decades. Worldwide, pulmonary mucormycosis (PM) presents in the lungs, which are the third main location for the infection after the rhino-orbito-cerebral (ROC) areas and the skin. The main risk factors for PM include hematological malignancies and solid organ transplantation, whereas ROC infections are classically favored by diabetes mellitus. The differences between the ROC and pulmonary locations are possibly explained by the activation of different mammalian receptors—GRP78 in nasal epithelial cells and integrin β1 in alveolar epithelial cells—in response to Mucorales. Alveolar macrophages and neutrophils play a key role in the host defense against Mucorales. The diagnosis of PM relies on CT scans, cultures, PCR tests, and histology. The reversed halo sign is an early, but very suggestive, sign of PM in neutropenic patients. Recently, the serum PCR test showed a very encouraging performance for the diagnosis and follow-up of mucormycosis. Liposomal amphotericin B is the drug of choice for first-line therapy, together with correction of underlying disease and surgery when feasible. After a stable or partial response, the step-down treatment includes oral isavuconazole or posaconazole delayed release tablets until a complete response is achieved. Secondary prophylaxis should be discussed when there is any risk of relapse, such as the persistence of neutropenia or the prolonged use of high-dose immunosuppressive therapy. Despite these novelties, the mortality rate from PM remains higher than 50%. Therefore, future research must define the place for combination therapy and adjunctive treatments, while the development of new treatments is necessary.

Population Pharmacokinetics, Exposure-Safety, and Probability of Target Attainment Analyses for Isavuconazole in Japanese Patients With Deep-Seated Mycoses

Isavuconazonium sulfate is the water-soluble prodrug of the novel, broad-spectrum, triazole antifungal agent isavuconazole. Its pharmacokinetics (PK) and exposure-response relationship have been well investigated, but not in a Japanese patient population. The objectives of this analysis were to (1) develop a population PK model for Japanese patients with deep-seated mycoses and healthy subjects, and to identify significant covariates; (2) determine the probability of PK-pharmacodynamic (PK-PD) target attainment in Japanese patients by a clinical dosing regimen; and (3) evaluate the exposure-safety relationship of isavuconazole in Japanese patients. Data from 2 phase 1 studies and 1 phase 3 study in Japanese patients were pooled to develop the population PK model using NONMEM. The PK of isavuconazole in Japanese patients was best described as a 2-compartment model with a Weibull absorption function and first-order elimination. The identified covariates on clearance were creatinine clearance and lean body mass. The probability of target attainment showed that >90% of simulated Japanese patients would achieve the PK-PD target, an exposure index corresponding to 50% survival of nonneutropenic infected mice, with minimal inhibitory concentration values of ≤1 mg/L according to Clinical and Laboratory Standards Institute methodology and of ≤2 mg/L according to European Committee on Antimicrobial Susceptibility Testing methodology by the clinical dosing regimen. No apparent relationships were found for any of the exposure parameters of isavuconazole with any assessed safety end points in Japanese patients. Taken together, the clinical dosing regimen is appropriate for the treatment of Japanese patients with deep-seated mycoses.

Variability of Isavuconazole Trough Concentrations during Longitudinal Therapeutic Drug Monitoring

Isavuconazole (ISA), a triazole antifungal agent, is licensed for the treatment of invasive aspergillosis and mucormycosis. Therapeutic drug monitoring (TDM) is a cornerstone of treatment efficacy for triazole antifungals due to their pharmacokinetic variability, except for ISA, for which the utility of TDM is still uncertain. We performed a retrospective study that aimed to assess the inter- and intra-individual variability of ISA trough concentrations (Cmin) and to identify the determinants involved in such variability. ISA Cmin measured in adult patients at the Grenoble Alpes University Hospital between January 2018 and August 2020 were retrospectively analyzed. In total, 304 ISA Cmin for 33 patients were analyzed. The median ISA Cmin was 2.8 [25th−75th percentiles: 2.0−3.7] mg/L. The inter- and intra-individual variability was 41.5% and 30.7%, respectively. Multivariate analysis showed independent covariate effects of dose (β = 0.004 ± 3.56 × 10−4, p < 0.001), Aspartate aminotransférase (ASAT) (β = 0.002 ± 5.41 × 10−4, p = 0.002), and protein levels (β = 0.022 ± 0.004, p < 0.001) on ISA Cmin, whereas C reactive protein levels did not show any association. This study, conducted on a large number of ISA Cmin, shows that ISA exposure exhibits variability, explained in part by the ISA dose, and ASAT and protein levels.

Challenges in the Treatment of Invasive Aspergillosis in Immunocompromised Children

Invasive aspergillosis (IA) is associated with significant morbidity and mortality. Voriconazole remains the drug of choice for the treatment of IA in children; however, the complex kinetics of voriconazole in children make dosing challenging and therapeutic drug monitoring (TDM) essential for treatment success. The overarching goal of this review is to discuss the role of voriconazole, posaconazole, isavuconazole, liposomal amphotericin B, echinocandins, and combination antifungal therapy for the treatment of IA in children. We also provide a detailed discussion of antifungal TDM in children.

Isavuconazole for COVID-19-Associated Invasive Mold Infections

Isavuconazole is a broad-spectrum antifungal drug recently approved as a first-line treatment for invasive aspergillosis and as a first or alternative treatment for mucormycosis. The purpose of this review was to report and discuss the use of isavuconazole for the treatment of COVID-19-associated aspergillosis (CAPA), and COVID-19-associated mucormycosis (CAM). Among all studies which reported treatment of CAPA, approximately 10% of patients were reportedly treated with isavuconazole. Considering 14 identified studies that reported the use of isavuconazole for CAPA, isavuconazole was used in 40% of patients (95 of 235 treated patients), being first-line monotherapy in over half of them. We identified six studies that reported isavuconazole use in CAM, either alone or in combination therapy. Overall, isavuconazole was used as therapy in 13% of treated CAM patients, frequently as combination or sequential therapy. The use of isavuconazole in CAPA and CAM is complicated by the challenge of achieving adequate exposure in COVID-19 patients who are frequently obese and hospitalized in the ICU with concomitant renal replacement therapy (RRT) or extracorporeal membrane oxygenation (ECMO). The presence of data on high efficacy in the treatment of aspergillosis, lower potential for drug–drug interactions (DDIs) and for subtherapeutic levels, and no risk of QT prolongation compared to other mold-active azoles, better safety profile than voriconazole, and the possibility of using an intravenous formulation in the case of renal failure are the advantages of using isavuconazole in this setting.

Isavuconazole plasma concentrations in critically ill patients during extracorporeal membrane oxygenation

BACKGROUND

Isavuconazole is an antifungal drug used for treatment of invasive fungal infections. Critically ill COVID-19 and influenza patients require extracorporeal membrane oxygenation (ECMO) in cases with severe acute respiratory distress syndrome and have risk factors for invasive pulmonary aspergillosis. Little is known about isavuconazole plasma concentrations during ECMO.

OBJECTIVES

To determine isavuconazole plasma concentrations in seven patients treated with intravenous isavuconazole under ECMO and the influence of the ECMO circuit immediately after the first isavuconazole dose.

METHODS

Critically ill patients treated with isavuconazole (standard doses) and ECMO were included in this study. Sixty-four blood samples used for measurement of isavuconazole concentrations were collected at several timepoints starting 2 h after the first isavuconazole dose up to 168 h. An additional 27 blood samples were drawn from the inflow and outflow line of the membrane oxygenator to assess any potential isavuconazole clearance effect of the ECMO oxygenation device and the lines.

RESULTS

Median isavuconazole trough levels above 1 μg/mL (min. 0.83, max. 1.73) or 2 μg/mL (min. 0.84, max. 2.97) were achieved 24 h or 96 h after the first dose of isavuconazole. The isavuconazole plasma concentrations pre (inflow line) and post (outflow line) the membrane oxygenator were directly correlated (ρ = 0.987, R2 = 0.994, P < 0.001). Post membrane oxygenator isavuconazole concentrations were directly correlated to contemporaneous samples obtained from the arterial lines of patients (ρ = 0.942, R2 = 0.945, P < 0.001).

CONCLUSIONS

Isavuconazole concentrations might be influenced by the higher volume of distribution due to ECMO therapy, but were not altered by the ECMO oxygenator and achieved median plasma concentrations >1 μg/mL 24 h after the first loading dose.

Fine Particulate Matter Exposure Levels in Patients with Normal-Tension Glaucoma and Primary Open-Angle Glaucoma: A Population-Based Study from Taiwan

Patients with NTG or POAG with more than one outpatient or discharge diagnosis from the ophthalmology department were included in the study. These data were merged with the PM2.5 data from the Air Quality Monitoring Network for analysis. This was a case−control study, with 1006 participants in the NTG group and 2533 in the POAG group. To investigate fine particulate matter (PM2.5) exposure levels in patients with normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG), patient data were obtained from Taiwan’s Longitudinal Health Insurance Database 2000 for the 2008 to 2013 period. We used a multivariate logic regression model to assess the risk for each participant. The PM2.5 exposure levels were divided into four groups: <25th percentile (Q1), <617 μg/mm3; 25th to 50th percentile (Q2), 617 to 1297 μg/mm3; 50th to 75th percentile (Q3), 1297 to 2113 μg/mm3; and >75th percentile (Q4), >2113 μg/mm3. The results are expressed in terms of odds ratio (OR) and 95% CI. A multiple logistic regression was used to compare the results of the NTG group with those of the POAG group. Compared with the PM2.5 Q1 level, the OR of the PM2.5 Q2 level was 1.009 (95% CI 0.812−1.254), the PM2.5 Q3 level was 1.241 (95% CI 1.241−1.537, p < 0.05), and the PM2.5 Q4 level was 1.246 (95% CI 1.008−1.539, p < 0.05). Our research reveals that compared with POAG, the risk of developing NTG is more closely related with PM2.5 exposure, and PM2.5 has a concentration−dose effect. It is hoped that in the future, in the clinical judgment of NTG and POAG, the level of PM2.5 in the environment can be taken as a risk factor.

Pharmacokinetics, Safety, and Tolerability of Single and Multiple Doses of Isavuconazonium Sulfate in Healthy Adult Japanese Subjects

Isavuconazonium sulfate is the water‐soluble prodrug of the novel, broad‐spectrum, triazole antifungal agent isavuconazole. This was a first‐in‐Japanese study assessing the pharmacokinetics, safety, and tolerability of isavuconazonium sulfate. The study was conducted in 2 parts: part 1 (single ascending dose; 100‐, 200‐, and 400‐mg equivalent of isavuconazole oral or intravenous administration); and part 2 (multiple doses for 16 days; 200‐mg equivalent of isavuconazole oral or intravenous administration; once‐daily administration with a loading regimen every 8 hours for the first 48 hours). A total of 60 and 16 subjects were randomized in part 1 and part 2, respectively. Observed clearance was lower in this study compared to what was previously reported in predominantly White populations and similar to clearance in non‐Japanese Asian populations. The range of the plasma isavuconazole concentration in this study was within the range of the pivotal phase 3 study, with no relationship between isavuconazole exposure and either efficacy or safety. There were no serious adverse events, and all reported treatment‐emergent adverse events were of mild intensity. This study confirmed that isavuconazonium sulfate was safe and well tolerated in healthy adult Japanese subjects.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Efficacy and safety of Isavuconazole for the treatment of invasive Aspergillus infection - an update of the literature

INTRODUCTION

Invasive aspergillosis is associated with high morbidity and mortality in immunocompromised patients. It is now increasingly reported in critically ill patients, including those with respiratory viral infections, such as influenza and COVID-19. Antifungal management is challenging due to diagnostic delay, adverse drug reactions, drug-drug interactions, narrow therapeutic window, and the emergence of resistance. Isavuconazole is the most recent FDA approved azole for the treatment of invasive aspergillosis, with data continuing to accumulate.

AREAS COVERED

The authors review the safety and efficacy of isavuconazole in the management of invasive aspergillosis based on the currently available evidence. The authors also report on the structure, mechanism of action, pharmacokinetic properties, in vitro and in vivo studies as well as clinical safety and efficacy reports of isavuconazole since its FDA approval.

EXPERT OPINION

Isavuconazole is non-inferior to voriconazole and is a safe, effective, and better tolerated option for the treatment of invasive aspergillosis. It offers several advantages over other antifungal agents, including having a better adverse event profile with respect to hepatotoxicity, neuro-visual toxicity, QTc prolongation, as well as a stable pharmacokinetic profile obviating the need for therapeutic drug monitoring. Further studies are needed to evaluate its performance in prophylaxis against invasive aspergillosis as well as in the treatment of aspergillosis in critically ill patients without underlying cancer or transplant.

Consensus guidelines for the diagnosis and management of invasive fungal disease due to moulds other than Aspergillus in the haematology/oncology setting, 2021

Invasive fungal disease (IFD) due to moulds other than Aspergillus is a significant cause of mortality in patients with malignancies or post haemopoietic stem cell transplantation. The current guidelines focus on the diagnosis and management of the common non-Aspergillus moulds (NAM), such as Mucorales, Scedosporium species (spp.), Lomentospora prolificans and Fusarium spp. Rare but emerging NAM including Paecilomyces variotii, Purpureocillium lilacinum and Scopulariopsis spp. are also reviewed. Culture and histological examination of tissue biopsy specimens remain the mainstay of diagnosis, but molecular methods are increasingly being used. As NAM frequently disseminate, blood cultures and skin examination with biopsy of any suspicious lesions are critically important. Treatment requires a multidisciplinary approach with surgical debridement as a central component. Other management strategies include control of the underlying disease/predisposing factors, augmentation of the host response and the reduction of immunosuppression. Carefully selected antifungal therapy, guided by susceptibility testing, is critical to cure. We also outline novel antifungal agents still in clinical trial which offer substantial potential for improved outcomes in the future. Paediatric recommendations follow those of adults. Ongoing epidemiological research, improvement in diagnostics and the development of new antifungal agents will continue to improve the poor outcomes that have been traditionally associated with IFD due to NAM.

A Visual and Comprehensive Review on COVID-19-Associated Pulmonary Aspergillosis (CAPA)

Coronavirus disease 19 (COVID-19)-associated pulmonary aspergillosis (CAPA) is a severe fungal infection complicating critically ill COVID-19 patients. Numerous retrospective and prospective studies have been performed to get a better grasp on this lethal co-infection. We performed a qualitative review and summarized data from 48 studies in which 7047 patients had been included, of whom 820 had CAPA. The pooled incidence of proven, probable or putative CAPA was 15.1% among 2953 ICU-admitted COVID-19 patients included in 18 prospective studies. Incidences showed great variability due to multiple factors such as discrepancies in the rate and depth of the fungal work-up. The pathophysiology and risk factors for CAPA are ill-defined, but therapy with corticosteroids and anti-interleukin-6 therapy potentially confer the biggest risk. Sampling for mycological work-up using bronchoscopy is the cornerstone for diagnosis, as imaging is often aspecific. CAPA is associated with an increased mortality, but we do not have conclusive data whether therapy contributes to an increased survival in these patients. We conclude our review with a comparison between influenza-associated pulmonary aspergillosis (IAPA) and CAPA.

Isavuconazonium Sulfate Use in Multi-Modal Management of Invasive Mucormycosis in Four Pediatric Allogeneic Hematopoietic Cell Transplant Patients

Prolonged neutropenia increases the risk for lethal invasive fungal infections (IFIs) such as those caused by Rhizopus species. Isavuconazonium sulfate is a new triazole that lacks pediatric dosing recommendations. Clinical courses of 4 pediatric patients with IFIs in the peri-allogeneic hematopoietic cell transplantation (alloHCT) period between 2015 and 2017 were reviewed. The reviews included previously unreported pharmacokinetic and safety data, and the IFIs included Rhizopus. Isavuconazonium sulfate was initiated with a loading dose followed by daily dosing, adjusted to a goal trough concentration of >3 mg/L based on adult literature. This target was achieved at a median of 7 days, demonstrating varying rates of metabolism. Renal insufficiency, electrolyte disturbances, and transaminitis were noted, although attribution was confounded by other alloHCT complications. One patient survived infection-free to hospital discharge and 1 of 3 deceased patients had evidence of an unresolved IFI (case 2). Case 2 was subtherapeutic for 39% of the duration of treatment, compared with others at an average of 29%, suggesting this target trough to be clinically relevant because case 2 demonstrated positive sinus and nasal cultures for Rhizopus on autopsy. We recommend initiation of isavuconazonium 10 mg/kg with a maximum dose of 372 mg. A loading dose of 10 mg/kg is used every 8 hours for 6 doses followed by 10 mg/kg dosing every 24 hours. Monitoring must continue beyond steady state. If early monitoring is not possible, we recommend a first drug level at week 3. If dose increases are required, a partial reload has been more successful instead of increasing daily doses. Further larger studies are needed to demonstrate optimum dosing in pediatric patients.

Interaction between flucloxacillin and azoles: Is isavuconazole next?

BACKGROUND

Isavuconazole is a triazole antifungal drug, approved for the treatment of invasive aspergillosis and mucormycosis. It has been previously reported that an interaction between flucloxacillin and voriconazole may lead to subtherapeutic voriconazole exposure, when used concomitantly. Since isavuconazole is also metabolised via cytochrome P450 enzymes, the same interaction may be expected.

OBJECTIVES

We aim to document exposure to isavuconazole in patients concomitantly treated with flucloxacillin.

PATIENTS

We report two patients treated with both isavuconazole and flucloxacillin, in whom we determined isavuconazole concentrations.

RESULTS

Low isavuconazole trough concentrations (<1 mg/L) were observed in two patients under concomitant treatment with flucloxacillin.

CONCLUSIONS

In combination with flucloxacillin, low isavuconazole concentrations were observed but an adequate isavuconazole exposure may be reached with dose augmentation. Therapeutic drug monitoring of isavuconazole is recommended to ensure an adequate exposure.

A Large Retrospective Assessment of Voriconazole Exposure in Patients Treated with Extracorporeal Membrane Oxygenation

BACKGROUND

Voriconazole is one of the first-line therapies for invasive pulmonary aspergillosis. Drug concentrations might be significantly influenced by the use of extracorporeal membrane oxygenation (ECMO). We aimed to assess the effect of ECMO on voriconazole exposure in a large patient population.

METHODS

Critically ill patients from eight centers in four countries treated with voriconazole during ECMO support were included in this retrospective study. Voriconazole concentrations were collected in a period on ECMO and before/after ECMO treatment. Multivariate analyses were performed to evaluate the effect of ECMO on voriconazole exposure and to assess the impact of possible saturation of the circuit's binding sites over time.

RESULTS

Sixty-nine patients and 337 samples (190 during and 147 before/after ECMO) were analyzed. Subtherapeutic concentrations (<2 mg/L) were observed in 56% of the samples during ECMO and 39% without ECMO (p = 0.80). The median trough concentration, for a similar daily dose, was 2.4 (1.2-4.7) mg/L under ECMO and 2.5 (1.4-3.9) mg/L without ECMO (p = 0.58). Extensive inter-and intrasubject variability were observed. Neither ECMO nor squared day of ECMO (saturation) were retained as significant covariates on voriconazole exposure.

CONCLUSIONS

No significant ECMO-effect was observed on voriconazole exposure. A large proportion of patients had voriconazole subtherapeutic concentrations.

Concomitant use of isavuconazole and CYP3A4/5 inducers: Where pharmacogenetics meets pharmacokinetics

BACKGROUND

Isavuconazole is a triazole antifungal drug, approved for the treatment of invasive aspergillosis and mucormycosis. Isavuconazole is metabolised by CYP3A4 and CYP3A5, and it has been shown that the CYP3A inducer rifampin reduces isavuconazole exposure. By extrapolation, the concomitant use of isavuconazole with moderate and strong CYP450 inducers is contraindicated, although it is known that some CYP450 inducers are less potent in comparison with rifampin.

OBJECTIVES

We aim to document exposure to isavuconazole in patients concomitantly treated with a CYP450 inducer that is less potent compared to rifampin. Moreover, although it is well known that CYP3A enzymes are important for the metabolism of isavuconazole, this induction effect has never been studied in combination with the patient's CYP3A genotype.

PATIENTS

We report three patients treated with both isavuconazole and a CYP3A inducer that is less potent compared to rifampin (rifabutin or phenobarbital), in whom we determined isavuconazole concentrations.

RESULTS

These cases suggest that the CYP3A4/5 genotype is an important determinant for isavuconazole exposure and that it might also influence the CYP450 induction interaction.

CONCLUSIONS

CYP3A inducers that are less potent compared to rifampin, may be combined with isavuconazole in patients with loss of CYP3A5 activity (CYP3A5*3/*3). Therapeutic drug monitoring is recommended during this combination. However, low-isavuconazole exposure was observed in the extensive metaboliser with CYP3A4*1/*1 and CYP3A5*1/*3 alleles.

Clinical and Pharmacological Considerations for Concomitant Administration of Posaconazole and Isavuconazole with Letermovir

We sought in this case-control retrospective study to compare posaconazole and isavuconazole (PCZ and IVC, respectively) plasma trough concentration (C _trough) levels in high-risk allogeneic hematopoietic cell transplant (HCT) recipients who received letermovir (LET) or not. PCZ/IVC C _trough levels were not found to be significantly different between cases and controls, as they were 1.31 mg/liter (median) (interquartile range [IQR], 0.90) versus 1.36 mg/liter (IQR, 1.16) (P = 0.31) and 3.20 mg/liter (IQR, 2.40) versus 2.35 mg/liter (IQR, 1.50) (P = 0.17), respectively. In conclusion, we observed PCZ/IVC C _trough levels within the expected range and no significant effect of LET coadministration.

Therapeutic Drug Monitoring of Isavuconazole: Serum Concentration Variability and Success Rates for Reaching Target in Comparison with Voriconazole

Isavuconazole (ISZ) is used in the treatment of aspergillosis and mucormycosis. The purpose of this study was to evaluate the therapeutic drug monitoring (TDM) of ISZ samples from a clinical setting performed at Statens Serum Institut. Materials/methods: Isavuconazole serum concentrations were determined by fluorescent detection on a UHPLC. Serum-ISZ (s-ISZ) results were included and compared to those of serum-voriconazole (s-VRZ) in a 33 month period from March 2017. Clinical data were obtained for patients receiving ISZ. The therapeutic range was initially 2-10 mg/L, but was adjusted to 2-5 mg/L during the study period except for selected patients with Mucorales infections who received off-label doses of ISZ. Results: A total of 273 s-ISZ and 1242 s-VRZ measurements from 35 and 283 patients, respectively, were included. Seventeen patients had received both ISZ and VRZ with TDM within the study period. The median s-ISZ was 4.3 mg/L (0.5-15.4 mg/L) with 83% of measurements within the therapeutic index. The median s-VRZ was 2.6 mg/L (0.2-21.9 mg/L) with 67% of measurements within the therapeutic index. The median intra-/interindividual coefficient of variation (CV) was 43.4%/54.8% for ISZ compared to 53.2%/83.3% for VRZ. For patients receiving ISZ, the adverse events were mostly gastroenteric and few drug-drug interactions were observed. Furthermore, immediate change from ISZ to VRZ treatment seemed to lead to prolonged metabolism of ISZ with detection up to 35 days after discontinuation. Conclusions: The majority of patients achieved s-ISZ levels well within the therapeutic range with less intra/interindividual CV than patients receiving VRZ.

Core Recommendations for Antifungal Stewardship: A Statement of the Mycoses Study Group Education and Research Consortium

In recent years, the global public health community has increasingly recognized the importance of antimicrobial stewardship (AMS) in the fight to improve outcomes, decrease costs, and curb increases in antimicrobial resistance around the world. However, the subject of antifungal stewardship (AFS) has received less attention. While the principles of AMS guidelines likely apply to stewarding of antifungal agents, there are additional considerations unique to AFS and the complex field of fungal infections that require specific recommendations. In this article, we review the literature on AMS best practices and discuss AFS through the lens of the global core elements of AMS. We offer recommendations for best practices in AFS based on a synthesis of this evidence by an interdisciplinary expert panel of members of the Mycoses Study Group Education and Research Consortium. We also discuss research directions in this rapidly evolving field. AFS is an emerging and important component of AMS, yet requires special considerations in certain areas such as expertise, education, interventions to optimize utilization, therapeutic drug monitoring, and data analysis and reporting.

Isavuconazole for the treatment of patients with invasive fungal diseases involving the central nervous system

The incidence of invasive fungal diseases (IFDs) with central nervous system (CNS) involvement is increasing due to the rising numbers of immunocompromised individuals, such as patients receiving chemotherapy, transplantation procedures, or immune-modulating therapies. CNS IFDs cause significant morbidity and mortality, and treatments are complicated by difficulties in identifying fungal pathogens and delivering antifungal agents to the CNS. Isavuconazole is a novel triazole with broad-spectrum activity that has shown good blood–brain barrier penetration in animal models. We present a retrospective analysis of isavuconazole in the treatment of patients with CNS IFDs and who either participated in the phase III VITAL or SECURE clinical trials, or were included in a named-patient program. A total of 36 patients were identified, including 27 patients from the clinical trials. Of these patients, 47.2% had hematologic malignancies, while 13.9% had no identifiable underlying conditions. Mucorales, Aspergillus species, and Cryptococcus species accounted for 30.6%, 22.2%, and 13.9% of infections, respectively. The overall survival rate was 80.6% at day 42 and 69.4% at day 84, and at the end of treatment, a complete or partial clinical response was achieved in 58.3% of patients. Isavuconazole exhibited clinical activity in a variety of CNS IFDs.

Clinical experience with isavuconazole in healthy volunteers and patients with invasive aspergillosis in China, and the results from an exposure-response analysis

BACKGROUND

Isavuconazole is a broad-spectrum triazole for the treatment of invasive fungal disease (IFD).

OBJECTIVE

To investigate the clinical experience with isavuconazole in Chinese individuals.

PATIENTS/METHODS

Participants were Chinese healthy volunteers from a Phase I pharmacokinetics (PK) and safety study of single/multiple doses of isavuconazole (n = 36) and Chinese patients from the global Phase III SECURE study that assessed safety and efficacy of isavuconazole vs voriconazole for IFD treatment (n = 26).

RESULTS

No clinically relevant differences in PK were found between Chinese and Western participants, although exposure was increased in Chinese volunteers. Treatment-emergent adverse events (TEAEs) were reported in 75.0% of healthy volunteers, many of which were infusion-related. No serious AEs were reported. In SECURE, findings in Chinese patients (n = 26) were similar to the global population. For patients who received ≥1 dose of study drug, allcause mortality from first dose to Day 42 was 10.0% (1/10) with isavuconazole and 25.0% (4/16) with voriconazole (treatment difference [95% confidence interval, CI]: -15.0% [-43.2%, 13.2%]). Overall response at the end of treatment for patients with proven/probable IFD was 25.0% and 16.7% with isavuconazole and voriconazole, respectively (treatment difference [95% CI] -8.3% [-60.2%, 43.5%]). Isavuconazole was associated with lower incidence of hepatobiliary, eye, skin, subcutaneous tissue and psychiatric disorders compared with voriconazole and lower incidence of treatment-related TEAEs, serious TEAES or death overall.

CONCLUSIONS

Although further research is required, this study demonstrated a favourable risk-benefit profile of isavuconazole in Chinese patients.

Review of Pharmacologic Considerations in the Use of Azole Antifungals in Lung Transplant Recipients

Mold-active azole antifungals are commonly prescribed for the prevention of invasive fungal infections in lung transplant recipients. Each agent exhibits a unique pharmacologic profile, an understanding of which is crucial for therapy selection and optimization. This article reviews pharmacologic considerations for three frequently-used azole antifungals in lung transplant recipients: voriconazole, posaconazole, and isavuconazole. Focus is drawn to analysis of drug-interactions, adverse drug reactions, pharmacokinetic considerations, and the role of therapeutic drug monitoring with special emphasis on data from the post-lung transplant population.

Isavuconazole Prophylaxis in Patients With Hematologic Malignancies and Hematopoietic Cell Transplant Recipients

BACKGROUND

Isavuconazole (ISA) is an attractive candidate for primary mold-active prophylaxis in high-risk patients with hematologic malignancies or hematopoietic cell transplant (HCT) recipients. However, data supporting the use of ISA for primary prophylaxis in these patients are lacking.

METHODS

We conducted a retrospective review of breakthrough invasive fungal infections (bIFIs) among adult hematologic malignancy patients and HCT recipients who received ≥7 days of ISA primary prophylaxis between 1 September 2016 and 30 September 2018. The incidence of bIFIs in patients receiving ISA was compared to those receiving posaconazole (POS) and voriconazole (VOR) during the same time period.

RESULTS

One hundred forty-five patients received 197 courses of ISA prophylaxis. Twelve bIFIs (Aspergillus fumigatus [5], Aspergillus species [2], Mucorales [2], Fusarium species [2], and Candida glabrata [1]) occurred, representing 8.3% of patients and 6.1% of courses, after a median duration of 14 days of ISA prophylaxis. All bIFIs occurred during periods of neutropenia. Seven patients (58.3%) died within 42 days of onset of bIFI. In addition, bIFIs complicated 10.2% of ISA, 4.1% of POS, and 1.1% of VOR courses among patients with de novo or relapsed/refractory acute myeloid leukemia during the study period, with invasive pulmonary aspergillosis (IPA) complicating 6.8% of ISA, 1.3% of POS, and zero VOR courses.

CONCLUSIONS

Although ISA has been approved for treatment of invasive Aspergillus and mucormycosis, we observed an increased rate of bIFI, notably IPA, using ISA for primary prophylaxis. These results support the need for further study to determine the role of ISA as primary prophylaxis.

Isavuconazole Therapeutic Drug Monitoring during Long-Term Treatment for Chronic Pulmonary Aspergillosis

Isavuconazole is the newest triazole antifungal, and it displays a favorable pharmacokinetic and safety profile. Less is known about its long-term use in immunocompetent hosts. We performed a retrospective service evaluation of isavuconazole therapeutic drug monitoring in patients with chronic pulmonary aspergillosis. Adverse events (AEs) and dose adjustments made during routine clinical practice were recorded, and AEs were classified based on Common Terminology Criteria for Adverse Events v5.0. Forty-five patients (mean age, 64 years) had 285 isavuconazole blood drug levels measured (mean level, 4.1 mg/liter). A total of 117 measurements (41%) were performed on patients on a 100-mg daily dose instead of 200 mg, and all had blood levels of >1 mg/liter. Age (P = 0.012) and a daily dose of 200 mg versus 100 mg (P = 0.02) were independent predictors of levels of >6 mg/liter. AEs were recorded for 25 patients (56%). The mean drug level at the first measurement was 5.5 ± 2 mg/liter for patients reporting AEs, compared with 4.2 ± 1.7 mg/liter for those not reporting AEs (P = 0.032). The cutoff threshold best predictive of an AE was 4.6 mg/liter (area under the concentration-time curve, 0.710). Sixteen patients (36%) discontinued isavuconazole therapy due to AEs. Twenty-six patients (58%) continued on isavuconazole beyond 6 months. Asthma (P = 0.022) and a daily dose of 200 mg versus 100 mg (P = 0.048) were associated with AEs of grade 2 or higher. A reduced daily dose (100 mg versus 200 mg) of isavuconazole resulted in satisfactory drug levels in a substantial number of patients; it was better tolerated and enabled continuation of therapy for prolonged periods.

Isavuconazole: Mechanism of Action, Clinical Efficacy, and Resistance

Increasing incidence of invasive fungal infections combined with a growing population of immunocompromised hosts has created a rising need for antifungal agents. Isavuconazole, a second-generation broad-spectrum triazole with activity against yeasts, dimorphic fungi, and molds, has a favorable safety profile and predictable pharmacokinetics. Patients typically tolerate isavuconazole well with fewer drug-drug interactions. Clinical trials have found it to be noninferior to voriconazole for invasive aspergillosis, an alternative therapy for salvage treatment of mucormycosis, and suitable for stepdown therapy with invasive candidiasis. Cross-resistance with other triazoles is common. More studies are needed to determine the role of isavuconazole in anti-mold prophylaxis in high-risk patients.

Isavuconazole-Animal Data and Clinical Data

The treatment of invasive fungal infections has deeply evolved in the last years with the inclusion of new antifungals, mainly new azoles (i.e., posaconazole, isavuconazole), to the therapeutic armamentarium. This review focuses on the role of isavuconazole for treating the most important invasive fungal infections both in animals and humans (hematological and non-hematological patients).

Tacrolimus dose modification in patients receiving concomitant isavuconazole after hematopoietic stem cell transplantation

INTRODUCTION

Isavuconazole is increasingly being used for antifungal prophylaxis during stem cell transplantation. Isavuconazole is a moderate inhibitor of Cytochrome P4503A4, and tacrolimus levels are anticipated to be elevated when given concomitantly with isavuconazole. We developed and validated a dose-modified tacrolimus regimen to better achieve and maintain target tacrolimus levels.Methods: Allogeneic stem cell transplantation recipients who received concomitant tacrolimus and isavuconazole from September 2017 to September 2018 were included. Tacrolimus was adjusted to achieve a target range 8-12 ng/ml. Intravenous tacrolimus was first initiated at 0.02 mg/kg/day on day 1, and transitioned to oral therapy using a 2:1 conversion ratio (n = 48). Clinical observations showed high interpatient variability. The intravenous dose was then reduced to 0.017 mg/kg/day, and oral:intravenous conversion changed to 3.1:1 (n = 24).

RESULTS

Interpatient variability was high (lower in the 0.017 mg/kg/day group; P < 0.0217). Patients in the 0.017 mg/kg/day group required fewer dose changes (P < 0.023) and had fewer levels >15 ng/ml (P < 0.021). Median tacrolimus dose declined over time; 0.016, 0.012 and 0.011 on days 1, 7 and 10 for patients receiving 0.02 mg/kg/day and 0.017, 0.014 and 0.013 in the 0.017 mg/kg group. Day 10 tacrolimus accumulation factor was 1.42 R_ac(Cmax) in the 0.02 mg/kg/day cohort compared to 1.23 R_ac(Cmax) in the 0.017 mg/kg/day cohort (P < 0.015). When transitioned to oral therapy, a oral:intravenous conversion ratio >3.1:1 was shown to improve chances for achieving target levels (P > 0.0744).

CONCLUSION

We recommend initiating intravenous tacrolimus dose at 0.017 mg/kg/day and using a 3.1:1 oral:intravenous conversion to reduce interpatient variability, drug accumulation and the number of suboptimal tacrolimus levels. Tacrolimus requires frequent drug level monitoring.

Isavuconazole Treatment in a Mixed Patient Cohort with Invasive Fungal Infections: Outcome, Tolerability and Clinical Implications of Isavuconazole Plasma Concentrations

Isavuconazole (ISA) is a triazole antifungal agent recommended for treatment of invasive aspergillosis or mucormycosis. The objective of this study was to evaluate ISA levels in a real world setting in a mixed patient cohort including patients with non-malignant diseases and extracorporeal treatments, and to correlate findings with efficacy and safety outcomes. We investigated 33 ISA treatment courses in 32 adult patients with hematological and other underlying diseases and assessed the clinical response, side effects and ISA trough plasma concentrations. ISA treatment led to complete and partial response in 87% of patients and was well tolerated. The median ISA plasma concentration was 3.05 µg/mL (range 1.38–9.1, IQR 1.93–4.35) in patients without renal replacement therapy (RRT) or extracorporeal membrane oxygenation (ECMO) and significantly lower in patients with RRT including cases with additional ECMO or Cytosorb^® adsorber therapy (0.88 µg/mL, range 0.57–2.44, IQR 0.71–1.21). After exclusion of values obtained from four patients with ECMO or Cytosorb^® adsorber the median concentration was 0.91 µg/mL (range 0.75–2.44, IQR 0.90–1.36) in the RRT group. In addition to previous recommendations we propose to monitor ISA trough plasma concentrations in certain circumstances including RRT, other extracorporeal treatments and obesity.

Lessons from isavuconazole therapeutic drug monitoring at a United Kingdom Reference Center

We determined isavuconazole serum concentrations for 150 UK patients receiving standard isavuconazole dosing regimens, including serial therapeutic drug monitoring for several patients on prolonged therapy. Mean trough isavuconazole concentrations in these patients were virtually identical to those reported previously from clinical trials, although greater variability was seen in patients below 18 years of age. Serial monitoring in patients receiving prolonged therapy suggested gradual, near-linear accumulation of the drug over many weeks.

Extrapolating Antifungal Animal Data to Humans - Is it reliable?

PURPOSE OF REVIEW

This article aimed to review animal models of antifungals and identifies human literature to assess if the extrapolation of results is reliable.

RECENT FINDINGS

Animal studies have helped identify AUC/MIC targets for new drugs and formulations such as isavuconazole and delayed release posaconazole that have translated to successful outcomes in humans. Models have also been influential in the identification of possible combination therapies for the treatment of aspergillosis, such as voriconazole and echinocandins. However, challenges are endured with animal models when it comes to replicating the pharmacokinetics of humans which has been exemplified with the newest itraconazole formulation. Additionally, animal models have displayed a survival benefit with the use of iron chelators and amphotericin for mucormycosis which was not demonstrated in humans.

SUMMARY

Animal models have been a staple in the development and optimization of antifungal agents. They afford the ability to investigate uncommon diseases, such as invasive fungal infections, that would otherwise take years and many resources to complete. Although there are many benefits of animal models there are also shortcomings. This is why the reliability of extrapolating data from animal models to humans is often scrutinized.

A Case Series and Literature Review of Isavuconazole Use in Pediatric Patients with Hemato-oncologic Diseases and Hematopoietic Stem Cell Transplantation

We analyzed the use of isavuconazole (ISA) as treatment or prophylaxis for invasive fungal disease (IFD) in children with hemato-oncologic diseases. A multicentric retrospective analysis was performed among centers belonging to the Italian Association for Pediatric Hematology and Oncology (AIEOP). Pharmacokinetic (PK) monitoring was applied by a high-performance liquid chromatography-tandem mass spectrometry (HLPC-MS/MS) assay. Twenty-nine patients were studied: 10 during chemotherapy and 19 after allogeneic hematopoietic stem cell transplantation (HSCT). The patients consisted of 20 males and 9 females with a median age of 14.5 years (age range, 3 to 18 years) and a median body weight of 47 kg (body weight range, 15 to 80 kg). ISA was used as prophylaxis in 5 patients and as treatment in 24 cases (20 after therapeutic failure, 4 as first-line therapy). According to European Organization for Research and Treatment of Cancer (EORTC) criteria, we registered 5 patients with proven IFD, 9 patients with probable IFD, and 10 patients with possible IFD. Patients with a body weight of <30 kg received half the ISA dose; the others received ISA on the adult schedule (a 200-mg loading dose every 8 h on days 1 and 2 and a 200-mg/day maintenance dose); for all but 10 patients, the route of administration switched from the intravenous route to the oral route during treatment. ISA was administered for a median of 75.5 days (range, 6 to 523 days). The overall response rate was 70.8%; 12 patients with IFD achieved complete remission, 5 achieved partial remission, 5 achieved progression, and 3 achieved stable IFD. No breakthrough infections were registered. PK monitoring of 17 patients revealed a median ISA steady-state trough concentration of 4.91 mg/liter (range, 2.15 to 8.54 mg/liter) and a concentration/dose (in kilograms) ratio of 1.13 (range, 0.47 to 3.42). Determination of the 12-h PK profile was performed in 6 cases. The median area under the concentration-time curve from 0 to 12 h was 153.16 mg·h/liter (range, 86.31 to 169.45 mg·h/liter). Common Terminology Criteria for Adverse Events grade 1 to 3 toxicity (increased transaminase and/or creatinine levels) was observed in 6 patients, with no drug-drug interactions being seen in patients receiving immunosuppressants. Isavuconazole may be useful and safe in children with hemato-oncologic diseases, even in the HSCT setting. Prospective studies are warranted.

A Single-Center, Open-Label Trial of Isavuconazole Prophylaxis against Invasive Fungal Infection in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation

Isavuconazole is a broad-spectrum triazole approved for treatment of invasive fungal infections (IFIs). In this open-label, single-arm study, we evaluated isavuconazole for antifungal prophylaxis after allogeneic hematopoietic cell transplantation (HCT). Adult patients admitted for first HCT received micafungin 150 mg i.v. daily from admission through day +7 (D+7) post-transplantation (±2 days) followed by isavuconazole prophylaxis (i.v./p.o. 372 mg every 8 hours for 6 doses and then 372 mg daily) through maximum D+98 post-HCT. Patients were followed through D+182. The primary endpoint was prophylaxis failure, defined as discontinuation of prophylaxis for proven/probable IFI; systemic antifungal therapy for >14 days for suspected IFI; toxicity leading to discontinuation; or an adverse event. Between June 2017 and October 2018, 99 patients were enrolled in the study, of whom 95 were included in our analysis. The median patient age was 57 years (interquartile range [IQR], 50 to 66 years). Sixty-four (67%) patients received peripheral blood, 17(18%) received bone marrow, and 14 (15%) received a cord blood allograft for acute leukemia (55%), lymphoma (17%), myelodysplastic syndrome (16%), or another hematologic disease (14%). One-third (n = 31; 33%) of patients underwent CD34⁺-selected HCT. Isavuconazole prophylaxis was given for a median of 90 days (IQR, 87 to 91 days). Ten patients (10.7%) met the primary endpoint. Candidemia occurred in 3 patients (3.1%), 1 of whom had grade III skin acute graft-versus-host disease (GVHD). Toxicity leading to discontinuation occurred in 7 patients (7.4%). The most common toxicity was liver function abnormalities in 5 patients, including grade 1 transaminitis in 2 patients and grade 3 hyperbilirubinemia in 3 patients. Four patients (4.2%) had early discontinuation of isavuconazole for reasons not meeting the primary study endpoint. Six patients died during the study period, including 3 during prophylaxis and 3 during follow-up. No deaths were attributed to isavuconazole. The majority (85%) of allogeneic HCT recipients completed isavuconazole prophylaxis according to protocol. The rate of breakthrough candidemia was 3.1%, and there were no invasive mold infections. Our data support the utility of isavuconazole for antifungal prophylaxis after HCT.

Antifungal Drugs Influence Neutrophil Effector Functions

There is a growing body of evidence for immunomodulatory side effects of antifungal agents on different immune cells, e.g., T cells. Therefore, the aim of our study was to clarify these interactions with regard to the effector functions of polymorphonuclear neutrophils (PMN). Human PMN were preincubated with fluconazole (FLC), voriconazole (VRC), posaconazole (POS), isavuconazole (ISA), caspofungin (CAS), micafungin (MFG), conventional amphotericin B (AMB), and liposomal amphotericin B (LAMB). PMN then were analyzed by flow cytometry for activation, degranulation, and phagocytosis and by dichlorofluorescein assay to detect reactive oxygen species (ROS). Additionally, interleukin-8 (IL-8) release was measured by enzyme-linked immunosorbent assay. POS led to enhanced activation, degranulation, and generation of ROS, whereas IL-8 release was reduced. In contrast, ISA-pretreated PMN showed decreased activation signaling, impaired degranulation, and lower generation of ROS. MFG caused enhanced expression of activation markers but impaired degranulation, phagocytosis, generation of ROS, and IL-8 release. CAS showed increased phagocytosis, whereas degranulation and generation of ROS were reduced. AMB led to activation of almost all effector functions besides impaired phagocytosis, whereas LAMB did not alter any effector functions. Independent from class, antifungal agents show variable influence on neutrophil effector functions in vitro Whether this is clinically relevant needs to be clarified.