No Dose Adjustment for Isavuconazole Based on Age or Sex

Therapeutic drug monitoring of azole antifungal agents

Deep-seated mycoses are generally opportunistic infections that are difficult to diagnose and treat. They are expected to increase with the spread of advanced medical care and aging populations, thus highlighting the need for safe, effective, and rapid drug-based treatments. Depending on a patient's age, sex, underlying diseases, and immune system status, therapeutic drug monitoring (TDM) may be important for assessing variable pharmacokinetic parameters, as well as preventing drug-drug interactions, adverse events, and breakthrough infections caused by fungal resistance. Azole antifungal agents play an important role in the prevention and treatment of deep-seated fungal infections, with each azoles having its own unique pharmacokinetic properties and specific adverse events. Therefore, it is necessary to use national and international guidelines to build evidence for the expansion of TDM indications. This review focuses on the clinical utility and future perspectives of TDM using azole antifungal agents, in the context of recent evidence in the literature.

Optimization of oral isavuconazole dose for population in special physiological or pathological state: a physiologically based pharmacokinetics model-informed precision dosing

OBJECTIVE

To recommend precision dosing and improve therapeutic efficacy against invasive fungal disease, a physiologically based pharmacokinetic model (PBPK) of oral isavuconazole (ISA) was established and used to explore its disposition across populations in different physiological and pathological states.

METHODS

Twenty-five pharmacokinetic (PK) studies of oral ISA were identified through a systematic search of PubMed. Concentration-time data were extracted using WebPlotDigitizer. Physiochemical parameters were obtained from published literature and DrugBank. Model development and simulation used the Simcyp population-based simulator, and visual predictive check and predictive error were used for the model evaluation. Probability of target attainment and the cumulative fraction of response analyses were performed for dose optimization.

RESULTS

The developed PBPK model was successfully validated in different populations. Most predicted concentration-time points aligned with the observed data, with acceptable predictive errors for the critical parameters. We predicted the PK profiles and parameters of ISA in a population with severe hepatic impairment (HI), a population with obesity and paediatric patients aged 1 to less than 6 years old. The probability of target attainment and cumulative fraction of response analyses indicated that the population with severe HI should have half the maintenance dose. The population with obesity and population with severe HI should have a loading dose of 300 mg every 8 h for 2 days. For paediatric patients aged 1 to less than 6 years old, a weight-based dosing regimen (5.38 mg/kg) of ISA was suggested.

CONCLUSION

The predicted value aligns with observations, suggesting ISA's potential predictability in PK profiles for other populations. The recommended dosing regimens increase our understanding of the use of ISA in special populations.

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Isavuconazonium Sulfate

A Biopharmaceutics Classification System (BCS)-based biowaiver monograph is presented for isavuconazonium sulfate. A BCS-based biowaiver is a regulatory option to substitute appropriate in vitro data for in vivo bioequivalence studies. Isavuconazonium sulfate is the prodrug of isavuconazole, a broad-spectrum azole antifungal indicated for invasive fungal infections. While the prodrug can be classified as a BCS Class III drug with high solubility but low permeability, the parent drug can be classified as a BCS Class II drug with low solubility but high permeability. Interestingly, the in vivo behavior of both is additive and leads isavuconazonium sulfate to act like a BCS class I drug substance after oral administration. In this work, experimental solubility and dissolution data were evaluated and compared with available literature data to investigate whether it is feasible to approve immediate release solid oral dosage forms containing isavuconazonium sulfate according to official guidance from the FDA, EMA and/or ICH. The risks associated with waiving a prodrug according to the BCS-based biowaiver guidelines are reviewed and discussed, noting that current regulations are quite restrictive on this point. Further, results show high solubility but instability of isavuconazonium sulfate in aqueous media. Although experiments on the dissolution of the capsule contents confirmed 'very rapid' dissolution of the active pharmaceutical ingredient (API) isavuconazonium sulfate, its release from the commercial marketed capsule formulation Cresemba is limited by the choice of capsule shell material, providing an additional impediment to approval of generic versions via the BCS-Biowaiver approach.

Population Pharmacokinetics of Isavuconazole in Adult: A Systematic Review

Isavuconazole (ISA) is a second generation broad-spectrum triazole antifungal drug derived from voriconazole structure, and its oral capsules is currently the only oral preparation approved for invasive mucormycosis. In recent years, population pharmacokinetic studies of ISA have been reported continuously. This paper aims to summarize the characteristics of population pharmacokinetic models of ISA in adults, and provide theoretical basis for individualized administration of ISA. We systematically searched PubMed, Embase, CNKI, Wanfang, VIP and other databases to collect population pharmacokinetic models published from the establishment of the database to March 2023. A total of 6 studies were included in this review, including healthy men and women, invasive fungal infections with malignant tumors or neutropenia, solid organ transplantation. The dose of ISA was 40-400mg for single-dose. The multiple-dose of ISA was 200mg every 8 hours for the first 48 hours and then 200mg once daily. All studies used a two-compartment model, first-order elimination. For oral formulations, except for one study that used first-order absorption, the others used Weibull absorption. Body mass index (BMI) was the most common covariable, followed by total body weight, lean body mass, race, sex, population type (healthy volunteers/patients), and creatinine clearance. These studies included several covariates, and the clearance rate (CL) was similar among populations. In the future, external validation and population pharmacokinetic studies in special populations such as patients with severe liver disease and ECMO support are needed.

Real-World, Multicenter Case Series of Patients Treated with Isavuconazole for Invasive Fungal Disease in China

BACKGROUND

The incidence of invasive fungal disease (IFD) has increased significantly, and IFD is a major cause of mortality among those with hematological malignancies. As a novel second-generation triazole antifungal drug offering both efficacy and safety, isavuconazole (ISA) is recommended by various guidelines internationally for the first-line treatment of invasive aspergillosis (IA) and invasive mucormycosis (IM) infecting adults. Given that it was only approved in China at the end of 2021, there is currently a lack of statistical data regarding its usage in the Chinese population. The primary objective of this report is to describe early experiences with ISA for the treatment of IFD.

METHODS

This was a real-world, multicenter, observational case series study conducted in China. It included patients from three centers who received ISA treatment from January 2022 to April 2023. A retrospective assessment on patient characteristics, variables related to ISA administration, the treatment response of IFD to ISA, and potential adverse events attributed to ISA was conducted.

RESULTS

A total of 40 patients met the inclusion criteria. Among them, 12 (30%) were diagnosed with aspergillosis, 2 (5%) were diagnosed with candidiasis, 12 (30%) were diagnosed with mucormycosis, and 14 cases did not present mycological evidence. The predominant site of infection was the lungs (36), followed by the blood stream (8), sinuses (4), and respiratory tract (2). The overall response rate was 75% (30 patients), with male patients having a higher clinical response than female patients (24/24 versus 6/16, p = 0.000) and autologous stem cell transplant patients having a higher clinical response than allogeneic stem cell transplant patients (6/6 versus 4/10, p = 0.027). During the observation period, four patients experienced adverse effects associated with ISA, but none of them discontinued the treatment.

CONCLUSIONS

Our findings suggest that ISA, a novel first-line treatment for IA and IM, is associated with a high clinical response rate, low incidence, and a low grade of adverse effects. Given the short time that ISA has been available in China, further research is needed to identify its efficacy and safety in the real world.

Sex, Gender, and the Regulation of Prescription Drugs: Omissions and Opportunities

The regulation of prescription drugs is an important health, safety, and equity issue. However, regulatory processes do not always consider evidence on sex, gender, and factors such as age and race, omissions that advocates have highlighted for several decades. Assessing the impact of sex-related factors is critical to ensuring drug safety and efficacy for females and males, and for informing clinical product monographs and consumer information. Gender-related factors affect prescribing, access to drugs, needs and desires for specific prescribed therapies. This article draws on a policy-research partnership project that examined the lifecycle management of prescription drugs in Canada using a sex and gender-based analysis plus (SGBA+) lens. In the same time period, Health Canada created a Scientific Advisory Committee on Health Products for Women, in part to examine drug regulation. We report on grey literature and selected regulatory documents to illustrate the extent to which sex and gender-based analysis plus (SGBA+) is utilized in regulation and policy. We identify omissions in the management of prescription drugs, and name opportunities for improvements by integrating SGBA+ into drug sponsor applications, clinical trials development, and pharmacovigilance. We report on recent efforts to incorporate sex disaggregated data and recommend ways that the management of prescription drugs can benefit from more integration of sex, gender, and equity.

A Pharmacokinetic Bioequivalence Study Comparing Different-Strength and -Size Capsules of Isavuconazonium Sulfate in Healthy Japanese Subjects

Isavuconazonium sulfate is the water-soluble prodrug of the novel, broad-spectrum, triazole antifungal agent isavuconazole. A size 0 elongated hard capsule containing 100 mg equivalent of isavuconazole is the currently marketed oral formulation in countries where it is approved. An alternative oral formulation, based on a lower-strength and smaller-size capsule, is required for pediatric and adolescent patients, as well as for some adult Japanese patients, especially those with difficulties swallowing larger capsules. This study was conducted to evaluate the bioequivalence of a size 0 elongated capsule containing 100 mg equivalent of isavuconazole and a size 3 capsule containing 40 mg equivalent of isavuconazole, after administration of 200 mg equivalent of isavuconazole (5 size 3 capsules or 2 size 0 elongated capsules) under fasted conditions. Bioequivalence of isavuconazole between the formulations was demonstrated, since point estimates (90%CI) for the ratio of the size 0 elongated capsules vs the size 3 capsules for maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were within the acceptable range of 0.8 to 1.25. It was confirmed that both formulations were well tolerated, and no new safety signals were observed in healthy Japanese adult male subjects.

Isavuconazole Therapeutic Drug Monitoring in critically ill ICU patients - a monocentric retrospective analysis

BACKGROUND

The broad-spectrum triazole isavuconazole is used for the treatment of invasive aspergillosis and mucormycosis. Data regarding human plasma concentrations in clinical routine of the drug are rare.

OBJECTIVES

Plasma concentrations of isavuconazole were determined in critically ill ICU patients while considering different patients' characteristics.

METHODS

Retrospective analysis of isavuconazole plasma concentrations were obtained as part of routine therapeutic drug monitoring (TDM) of ICU patients with invasive aspergillosis or other fungal infections treated with isavuconazole. Plasma levels 0-4h after last dosing were defined as peak levels (C_max ), those 20-28h after last dosing as trough levels (C_min ).

RESULTS

Overall, 223 isavuconazole levels of 41 patients were analysed, divided into 141 peak levels and 82 trough levels. The overall median C_max was 2.36 μg/mL (mean 2.43 μg/mL, range 0.41 - 7.79 μg/mL) and the overall median C_min was 1.74 μg/mL (mean 1.77 μg/mL, range 0.24 - 4.96 μg/mL). In total, 31.7% of the C_min values of the total cohort were below the plasma target concentrations of 1 μg/mL, defined as EUCAST antifungal clinical breakpoint for Aspergillus fumigatus. Both peak and trough plasma levels of isavuconazole were significantly lower among patients with a body-mass-index (BMI) ≥ 25. In addition, a significant correlation was observed between isavuconazole trough levels and sepsis-related organ failure assessment (SOFA) score.

CONCLUSIONS

This study shows that isavuconazole plasma concentrations vary in critical ill ICU patients. Significantly lower isavuconazole levels were associated with elevated BMI and higher SOFA score indicating a need of isavuconazole TDM in this specific patient population.

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.

Effects of food on the pharmacokinetics of ensartinib in healthy Chinese subjects

Ensartinib is a promising, aminopyridazine-based small molecule that potently inhibits anaplastic lymphoma kinase. This random, two-period, crossover study evaluated the effects of food on the pharmacokinetics of ensartinib after a single dose (225 mg) in healthy Chinese subjects. The pharmacokinetic parameters of ensartinib were calculated using non-compartmental analysis. Twenty-four Chinese healthy subjects aged 20-44 years were included in this study. The area under the concentration-time curve of ensartinib was approximately 25% lower after the intake of a high-fat, high-calorie meal prior to dosing, whereas the maximum plasma concentration was decreased by approximately 37%, illustrating the statistically significant effect of food on ensartinib pharmacokinetics. In addition, food intake prolonged the absorption phase of ensartinib (median time to maximum plasma concentration, from 4.5 to 6 h). Population pharmacokinetic (PopPK) analysis was conducted using NONMEM, and the influences of food, age, sex, body weight, and body mass index were studied via covariate analysis. In this analysis, ensartinib plasma concentrations were best described by a one-compartment model with Weibull absorption. The final model included food and age as covariates on apparent distribution and apparent clearance. Based on the final PopPK model, food was identified as a significant covariate for apparent clearance, apparent volume of distribution, and absorption rate constant, consistent with the results of non-compartmental pharmacokinetic analysis.

Predictors of Voriconazole Trough Concentrations in Patients with Child-Pugh Class C Cirrhosis: A Prospective Study

This prospective observational study aimed to clinically describe voriconazole administrations and trough concentrations in patients with Child–Pugh class C and to investigate the variability of trough concentration. A total of 144 voriconazole trough concentrations from 43 Child–Pugh class C patients were analyzed. The majority of patients (62.8%) received adjustments. The repeated measured trough concentration was higher than the first and final ones generally (median, 4.33 vs. 2.99, 3.90 mg/L). Eight patients with ideal initial concentrations later got supratherapeutic with no adjusted daily dose, implying accumulation. There was a significant difference in concentrations among the six groups by daily dose (p = 0.006). The bivariate correlation analysis showed that sex, CYP2C19 genotyping, daily dose, prothrombin time activity, international normalized ratio, platelet, and Model for end-stage liver disease score were significant factors for concentration. Subsequently, the first four factors mentioned above entered into a stepwise multiple linear regression model (variance inflation factor <5), implying that CYP2C19 testing makes sense for precision medicine of Child–Pugh class C cirrhosis patients. The equation fits well and explains the 34.8% variety of concentrations (R² = 0.348). In conclusion, it needs more cautious administration clinically due to no recommendation for Child–Pugh class C patients in the medication label. The adjustment of the administration regimen should be mainly based on the results of repeated therapeutic drug monitoring.

A physiologically based pharmacokinetic analysis to predict the pharmacokinetics of intravenous isavuconazole in patients with or without hepatic impairment

Isavuconazole (ISA) is an azole antifungal used in the treatment of invasive aspergillosis and mucormycosis. Patients with mild and moderate hepatic impairment have lower clearance (CL) as compared to the healthy population. Currently, there is no data on ISA in patients with severe hepatic impairment (Child-Pugh Class C). The purpose of this study was to build a physiologically based pharmacokinetic (PBPK) model to describe the pharmacokinetics (PK) of intravenous ISA, and to predict changes in ISA disposition in different patient populations and in patients with hepatic impairment to guide personalized dosing. By incorporating the systemic and drug specific parameters of ISA, the model was initially developed in healthy population and validated with 10 independent PK profiles obtained from healthy subjects and from patients with normal liver function. The results showed a satisfactory predictive capacity, with most of the relative predictive errors being between ±30% for area under the curve (AUC) and C_max The observed plasma concentration-time profiles of ISA were well described by the model predicted profiles. The model adequately predicted the reduced CL of ISA in patients with mild and moderate hepatic impairment. Furthermore, the model predicted a decrease in CL of about 60% in patients with severe hepatic impairment. Therefore, we recommend reducing the dose by 50% in patients with severe hepatic impairment. The model also predicted differences in the PK of ISA between Caucasian and Asian population, with the CL ratio of 0.67 in Chinese vs Caucasian population. The developed PBPK model of ISA provides a reasonable approach for optimizing the dosage regimen in different ethnic populations and in patients with severe hepatic impairment.

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.

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.

Population Pharmacokinetics of Intravenous Isavuconazole in Solid-Organ Transplant Recipients

Isavuconazole (ISA) is a triazole antifungal with activity against yeasts and molds. We established a population pharmacokinetic (pop PK) model of intravenous (i.v.) ISA to identify covariates that affect pharmacokinetics, using plasma samples from solid-organ transplant (SOT) recipients receiving peritransplant prophylaxis. Samples (n = 471) from 79 SOT recipients were utilized for pop PK analysis using nonlinear mixed-effect modeling NONMEM software. ISA (i.v.) PK parameters were best described by a two-compartment model. Significant covariates were sex on clearance (∼53% higher in women than men) and body mass index on peripheral volume of distribution. Incorporating drug exposure into Monte Carlo simulations, we demonstrated that standard ISA dosing is likely to attain the PK-pharmacodynamic (PD) target (area under the concentration curve/MIC ratio [AUC/MIC]) for treatment effectiveness against almost all infections caused by Aspergillus fumigatus isolates exhibiting MICs of ≤0.5 μg/ml (modal MIC). In contrast, standard dosing is predicted to attain PK-PD targets against <20% of infections caused by Candida albicans and Candida glabrata isolates exhibiting MICs of ≥0.016 and ≥0.5 μg/ml, respectively (modal MICs). These data are consistent with our SOT program's experience with ISA breakthrough infections, where 3 of 4 were caused by C. glabrata for which probabilities of PK-PD target attainment (PTA) were only 70% and 0% for isolates with MICs of 0.25 μg/ml and 1 μg/ml. Our findings provide important new insights into how ISA use might be optimized following SOT.

Isavuconazole in Hematological Patients: Results of a Real-Life Multicentre Observational Seifem Study

Invasive fungal diseases (IFDs) remain a major clinical issue in patients with hematological malignancies (HMs). To confirm the efficacy and safety of the new azole isavuconazole (ISV) in a clinical care setting, we planned a multicenter retrospective study; we collected data on all possible/probable/proven IFDs in patients with HMs treated with ISV in 17 centers. Between July 2016 and November 2018, 128 patients were enrolled, and 122 were fully evaluable. ISV was employed as the 1st line therapy in 43 (35%) patients and as a subsequent therapy in 79 (65%) patients. The response rate was 82/122 patients (67.2%); it was similar when using ISV as a 1st or 2nd line treatment (60.5% vs 70.9%, respectively; p = 0.24). In multivariate analysis, both female sex (OR: 2.992; CI: 1.22-7.34) and induction phase of treatment (OR: 3.953; CI: 1.085-14.403) were predictive of a favorable response. At a median follow-up of 5 months, 43 (35.2%) patients were dead; the 1-year overall survival (OS) was 49.9%. In multivariate analysis, the response to ISV (OR: 0.103; CI: 0.041-0.262) and IFD refractoriness to previous antifungals (OR: 3.413; CI: 1.318-8.838) were statistically significant for OS. Adverse events (AEs) were reported in 15/122 patients (12.3%); grade 3-4 AEs were reported in 5 (4%) and led to ISV discontinuation. Our study confirms the safety and tolerability of ISV, also in diseases other than acute leukemia. Phase of hematological disease, gender and refractoriness to previous antifungals are the main predictive factors for the aforementioned response and outcome.