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

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.

Pharmacokinetics of isavuconazole at different target sites in healthy volunteers after single and multiple intravenous infusions

BACKGROUND

Invasive aspergillosis is a severe fungal infection that affects multiple organ systems including the CNS and the lungs. Isavuconazole, a novel triazole antifungal agent, has demonstrated promising activity against Aspergillus spp. However, data on the penetration of isavuconazole into the CNS and ELF and intracellular accumulation remain limited.

MATERIALS AND METHODS

We conducted a prospective single-centre pharmacokinetic (PK) study in 12 healthy volunteers. Subjects received seven doses of 200 mg isavuconazole to achieve an assumed steady-state. After the first and final infusion, plasma sampling was conducted over 8 and 12 h, respectively. All subjects underwent one lumbar puncture and bronchoalveolar lavage, at either 2, 6 or 12 h post-infusion of the final dose. PBMCs were collected in six subjects from blood to determine intracellular isavuconazole concentrations at 6, 8 or 12 h. The AUC/MIC was calculated for an MIC value of 1 mg/L, which marks the EUCAST susceptibility breakpoint for Aspergillus fumigatus and Aspergillus flavus.

RESULTS

C max and AUC0-24h of isavuconazole in plasma under assumed steady-state conditions were 6.57 ± 1.68 mg/L (mean ± SD) and 106 ± 32.1 h·mg/L, respectively. The average concentrations measured in CSF, ELF and in PBMCs were 0.07 ± 0.03, 0.94 ± 0.46 and 27.1 ± 17.8 mg/L, respectively. The AUC/MIC in plasma, CSF, ELF and in PBMCs under steady-state conditions were 106 ± 32.1, 1.68 ± 0.72, 22.6 ± 11.0 and 650 ± 426 mg·h/L, respectively.

CONCLUSION

Isavuconazole demonstrated moderate penetration into ELF, low penetrability into CSF and high accumulation in PBMCs. Current dosing regimens resulted in sufficient plasma exposure in all subjects to treat isolates with MICs ≤ 1 mg/L.

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.

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.

Clinical research advances of isavuconazole in the treatment of invasive fungal diseases

Purpose

Invasive fungal diseases (IFD) are a major global public health concern. The incidence of IFD has increased the demand for antifungal agents. Isavuconazole (ISA) is a new triazole antifungal agent that has shown promising efficacy in the prophylaxis and treatment of invasive fungal diseases. The aim of this review is to summarize the recent real-world experiences of using ISA for the treatment and prevention of IFD.

Methods

We performed a comprehensive literature search of the MEDLINE, PubMed, Embase, and Cochrane databases for clinical applications of ISA in the real world. Tables and reference lists are presented for this systematic review.

Results

IFD poses a major threat to public health and causes high mortality rates. ISA may provide a good treatment. For example, the efficacy of ISA in the treatment of invasive aspergillosis (IA) is comparable to that of voriconazole, and its efficacy in the treatment of invasive mucormycosis (IM) is similar to that of liposomal amphotericin B (L-AmB); therefore, ISA is recommended as the first-line treatment for IA and IM. ISA can also achieve good efficacy in the treatment of invasive candidiasis (IC) and can be used as an alternative to de-escalation therapy after first-line drug therapy. In addition, most studies have shown the efficacy and safety of ISA for the prophylaxis of IFD.

Conclusion

Taken together, ISA are expected to become a new choice for the treatment and prevention of IFD because of their good tolerability, high bioavailability, and few drug interactions.

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.