Pharmacokinetic Evaluation of CYP3A4-Mediated Drug-Drug Interactions of Isavuconazole With Rifampin, Ketoconazole, Midazolam, and Ethinyl Estradiol/Norethindrone in Healthy Adults

Phase 1 drug-drug interaction study to assess the effect of CYP3A4 inhibition and pan-CYP induction on the pharmacokinetics and safety of fosmanogepix in healthy participants

Immunocompromised patients are susceptible to fungal infections, and drug-drug interactions with antifungals may occur due to concomitant medications. Fosmanogepix [FMGX; active moiety manogepix (MGX)] targets glycosylphosphatidylinositol-anchored mannoprotein synthesis and maturation, essential for fungal virulence. This phase 1, fixed-sequence study in healthy participants evaluated the effect of strong CYP3A4 inhibitor itraconazole [Cohort 1 (n = 18); FMGX 500 mg intravenous (IV) twice a day (BID )+ itraconazole 200 mg oral once a day (QD)] and pan-CYP inducer rifampin [Cohort 2 (n = 18); FMGX 1,000 mg IV BID + rifampin 600 mg oral QD] on the pharmacokinetics of FMGX and MGX. In cohort 1, geometric mean (GM) MGX Cmax, AUC0-t, and AUCinf were almost similar with and without itraconazole administration. In Cohort 2, GM MGX Cmax was slightly lower and AUC0-t and AUCinf were significantly lower after rifampin administration, with the least squares GM ratio associated 90% confidence intervals (CIs) below 80 - 125% (no effect window). No deaths, serious adverse events (SAEs), or FMGX-related withdrawals were reported. In both cohorts, a total of 188 AEs (n = 30; 186 mild; two moderate) were reported. In all, 37 of 188 AEs (n = 12) were considered FMGX related (most frequent: headache, nausea, and hot flush). Administration of FMGX alone and with itraconazole or rifampin was safe and well tolerated. A strong CYP3A4 inhibitor had no effect on FMGX or MGX exposure. A strong pan-CYP inducer had no effect on FMGX exposure but demonstrated ~45% decrease in MGX exposure.

CLINICAL TRIALS

This study is registered with ClinicalTrials.gov as NCT04166669 and with EudraCT as number 2019-003586-17.

Pharmacological management of invasive mold infections in solid organ transplant recipients

INTRODUCTION

Solid organ transplant (SOT) recipients face an increased susceptibility to invasive fungal infection (IFI) due to filamentous fungi. Post-transplant invasive aspergillosis (IA) and mucormycosis are related to exceedingly high mortality rates and graft loss risk, and its management involve a unique range of clinical challenges.

AREAS COVERED

First, the current treatment recommendations for IA and mucormycosis among SOT recipients are critically reviewed, including the supporting evidence. Next, we discussed particular concerns in this patient population, such as drug-drug interactions (DDIs) between triazoles and post-transplant immunosuppression or treatment-related toxicity. The role for immunomodulatory and host-targeted therapies is also considered, as well as the theoretical impact of the intrinsic antifungal activity of calcineurin inhibitors. Finally, a personal opinion is made on future directions in the pharmacological approach to post-transplant IFI.

EXPERT OPINION

Despite relevant advances in the treatment of mold IFIs in the SOT setting, such as the incorporation of isavuconazole (with lower incidence of DDIs and better tolerability than voriconazole), there remains a large room for improvement in areas such as the position of combination therapy or the optimal strategy for the reduction of baseline immunosuppression. Importantly, future studies should define the specific contribution of newer antifungal agents and classes.

Nanotherapeutics for the delivery of antifungal drugs

The treatment of fungal infections is challenging with high death rates reported among immunocompromised patients. The currently available antifungals suffer from poor bioavailability and solubility, pharmacokinetics, and drug resistance, with limited cellular uptake. The clinical pipeline of new antifungals is dry. The incorporation of antifungal drugs into polymer-based nanocarriers to form nanotherapeutics is a promising approach to enhance the therapeutic outcomes of the available antifungal drugs. This review summarizes different polymer-based nanotherapeutics strategies that have been explored for the delivery of antifungals, resulting in enhanced therapeutic outcomes, such as improved pharmacokinetics, targeted/sustained delivery, prolonged drug circulation, retention of the drugs at the localized site of action, and overcoming drug resistance when compared with the free antifungal drugs.

Posaconazole and midostaurin in patients with FLT3-mutated acute myeloid leukemia: Pharmacokinetic interactions and clinical facts in a real life study

Midostaurin is used in combination with chemotherapy to treat patients with newly diagnosed FLT3-mutated acute myeloid leukemia. Chemotherapy-induced neutropenia exposes these patients to a significant risk of invasive fungal infections (IFIs). International guidelines recommend primary antifungal prophylaxis with posaconazole (PCZ) but nested analysis of a phase III trial showed that strong PCZ inhibition of CYP3A4 diminished midostaurin metabolism and increased midostaurin plasma levels; however, midostaurin-related adverse events (AEs) were only moderately exacerbated. We conducted a prospective multicenter real-life study to evaluate (i) how often concerns around PCZ-midostaurin interactions made the hematologist prescribe antifungals other than PCZ, (ii) how remarkably PCZ increased midostaurin plasma levels, and (iii) how significantly PCZ-midostaurin interactions influenced hematologic and safety outcomes of induction therapy. Although the hematologists were blinded to pharmacokinetic findings, as many as 16 of 35 evaluable patients were prescribed antifungal prophylaxis with micafungin, weak CYP3A4 inhibitor, in place of PCZ (p < 0.001 for deviation from guidelines). In the 19 patients managed as per guidelines, PCZ-midostaurin interactions were more remarkable than previously characterized, such that at the end of induction therapy midostaurin minimum plasma concentration (Cmin ) was greater than three times higher than reported; moreover, midostaurin Cmin , maximum plasma concentration, and area under the curve were more than or equal to four times higher with PCZ than micafungin. Hematologic outcomes (complete remission and duration of severe neutropenia) and safety outcomes (midostaurin-related any grade or grade ≥3 AEs) were nonetheless similar for patients exposed to PCZ or micafungin, as was the number of breakthrough IFIs. In waiting for randomized phase III trials of new prophylaxis regimens, these findings show that PCZ should remain the antifungal of choice for the midostaurin-treated patient.

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.

Evaluation of the Drug-Drug Interaction Potential of Ensitrelvir Fumaric Acid with Cytochrome P450 3A Substrates in Healthy Japanese Adults

BACKGROUND

Management of drug-drug interactions (DDIs) for ensitrelvir, a novel 3-chymotrypsin-like protease inhibitor of SARS-CoV-2 infection is crucial. A previous clinical DDI study of ensitrelvir with midazolam, a clinical index cytochrome P450 (CYP) 3A substrate, demonstrated that ensitrelvir given for 5 days orally with a loading/maintenance dose of 750/250 mg acted as a strong CYP3A inhibitor.

OBJECTIVES

The objectives of this study were to investigate the effect of ensitrelvir on the pharmacokinetics of CYP3A substrates, dexamethasone, prednisolone and midazolam, and to assess the pharmacokinetics, safety, and tolerability of ensitrelvir following multiple-dose administration of ensitrelvir.

METHODS

This was a Phase 1, multicenter, single-arm, open-label study in healthy Japanese adult participants. The effects of multiple doses of ensitrelvir in the fasted state on the pharmacokinetics of dexamethasone, prednisolone, and midazolam were investigated. Ensitrelvir was administered from Day 1 through Day 5, with a loading/maintenance dose of 750/250 mg for the dexamethasone and prednisolone cohorts whereas 375/125 mg for the midazolam cohort. Either dexamethasone, prednisolone, or midazolam was administered alone (Day - 2) or in combination with ensitrelvir (Day 5) in each of the cohorts. Additionally, dexamethasone or prednisolone was administered on Days 9 and 14. The pharmacokinetic parameters of ensitrelvir, dexamethasone, prednisolone, and midazolam were calculated based on their plasma concentration data with non-compartmental analysis. In safety assessments, the nature, frequency, and severity of treatment-emergent adverse events were evaluated and recorded.

RESULTS

The area under the concentration-time curve (AUC) ratio of dexamethasone on Day 5 was 3.47-fold compared with the corresponding values for dexamethasone alone on Day - 2 and the effect diminished over time after the last dose of ensitrelvir. No clinically meaningful effect was observed for prednisolone. The AUC ratio of midazolam was 6.77-fold with ensitrelvir 375/125 mg suggesting ensitrelvir at 375/125 mg strongly inhibits CYP3A similar to that at 750/250 mg. No new safety signals with ensitrelvir were reported during the study.

CONCLUSION

The inhibitory effect for CYP3A was confirmed after the last dose of ensitrelvir, and the effect diminished over time. In addition, ensitrelvir at 375/125 mg showed CYP3A inhibitory potential similar to that at 750/250 mg. These findings can be used as a clinical recommendation for prescribing ensitrelvir with regard to concomitant medications.

CLINICAL TRIAL REGISTRATION

Japan Registry of Clinical Trials identifier: jRCT2031210202.

Studies on the inhibitory effect of isavuconazole on flumatinib metabolism in vitro and in vivo

As the validated agent for the treatment of chronic myelogenous leukemia (CML), flumatinib is a novel oral tyrosine kinase inhibitor (TKI) with higher potency and selectivity for BCR-ABL1 kinase compared to imatinib. Many patients experience aspergillosis infection and they may start using isavuconazole, which is an inhibitor of CYP3A4. However, there is no study on their interaction in vitro and in vivo. In the present study, the concentrations of flumatinib and its major metabolite M1 were rapidly determined using an stable ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. The half-maximal inhibitory concentration (IC₅₀) was 6.66 μM in human liver microsomes (HLM), while 0.62 μM in rat liver microsomes (RLM) and 2.90 μM in recombinant human CYP3A4 (rCYP3A4). Furthermore, the mechanisms of inhibition of flumatinib in human liver microsomes, rat liver microsomes and rCYP3A4 by isavuconazole were mixed. Moreover, ketoconazole, posaconazole, and isavuconazole showed more potent inhibitory effects than itraconazole, fluconazole, and voriconazole on HLM-mediated flumatinib metabolism. In pharmacokinetic experiments of rats, it was observed that isavuconazole could greatly change the pharmacokinetic parameters of flumatinib, including AUC_(0-t), AUC_(0-∞), C_max and CLz/F, but had no effect on the metabolism of M1. According to the results of in vitro and in vivo studies, the metabolism of flumatinib was inhibited by isavuconazole, suggesting that isavuconazole may raise the plasma concentration of flumatinib. Thus, it is important to take special care of the interactions between flumatinib and isavuconazole in clinical applications.

Post-hoc analysis of the safety and efficacy of isavuconazole in older patients with invasive fungal disease from the VITAL and SECURE studies

Isavuconazole is a triazole with broad-spectrum antifungal activity. In this post-hoc analysis of two prospective clinical trials (VITAL and SECURE), the safety and efficacy of isavuconazole in patients aged ≥ 65 years with invasive fungal diseases were evaluated. Patients were divided into two subgroups (≥ 65 and < 65 years). Adverse events (AEs); all-cause mortality; and overall, clinical, mycological, and radiological response were assessed. A total of 155 patients ≥ 65 years were enrolled in both trials. Most patients reported AEs. In the isavuconazole arm of both studies, serious AEs (SAEs) were greater in patients ≥ 65 versus < 65 years: 76.7% versus 56.9% (VITAL); 61.9% versus 49.0% (SECURE). In SECURE, SAE rates were similar in the ≥ 65 years subgroup of both treatment arms (61.9% vs 58.1%), while in the < 65 years subgroup the SAE rate was lower in the isavuconazole arm (49.0% vs 57.4%). In VITAL, all-cause mortality through day 42 (30.0% vs 13.8%) was higher, and overall response at end of treatment (27.6% vs 46.8%) was lower in patients ≥ 65 years versus < 65 years. In SECURE, all-cause mortality was similar between both subgroups, and isavuconazole (20.6% vs 17.9%) and voriconazole (22.6% vs 19.4%) treatment arms. The overall response was lower in the ≥ 65 years than the < 65 years subgroup in the isavuconazole (23.7% vs 39.0%) and voriconazole (32.0% vs 37.5%) arms. The safety and efficacy of isavuconazole were better in patients < 65 versus ≥ 65 years, and the safety profile was more favorable than that of voriconazole in both subgroups.Clinicaltrials.gov identifier NCT00634049 and NCT00412893.

New Targeted Drugs for Acute Myeloid Leukemia and Antifungals: Pharmacokinetic Challenges and Opportunities

BACKGROUND

Acute myeloid leukemia (AML) is a life-threatening disease whose treatment is made difficult by a number of mutations or receptor overexpression in the proliferating cellular clones. Life expectancy of patients diagnosed with new, relapsed-refractory, or secondary AML has been improved by drugs targeted at such moieties. Regrettably, however, clinical use of new AML drugs is complicated by pharmacokinetic interactions with other drugs the patient is exposed to.

SUMMARY

The most relevant drug-drug interactions (DDI) with clinical implications build on competition for or induction/inhibition of CYP3A4, which is a versatile metabolizer of a plethora of pharmacological agents. Here, we review DDI between AML drugs and the agents used to prevent or treat invasive fungal infections (IFI). The pathophysiology of AML, characterized by functionally defective white blood cells and neutropenic/immunosuppressive effects of concomitant induction chemotherapy, can in fact increase the risk of infectious complications, with IFI causing high rates of morbidity and mortality. Triazole antifungals, such as posaconazole, are strong inhibitors of CYP3A4 and may thus cause patient's overexposure to AML drugs that are metabolized by CYP3A4. We describe potential strategies to minimize the consequences of DDI between triazole antifungals and targeted therapies for AML and the role that collaboration between clinical pharmacologists, hematologists, and clinical or laboratory microbiologists may have in these settings.

KEY MESSAGES

Therapeutic drug monitoring and clinical pharmacology stewardship could represent two strategies that best express multidisciplinary collaboration for improving patient management.

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.

Isavuconazole for the Treatment of Invasive Mold Disease in Solid Organ Transplant Recipients: A Multicenter Study on Efficacy and Safety in Real-life Clinical Practice

BACKGROUND

Isavuconazole has theoretical advantages over other mold-active triazoles for the treatment of invasive aspergillosis and mucormycosis after solid organ transplantation (SOT). The available clinical experience, nevertheless, is scarce.

METHODS

We performed a retrospective study including all adult SOT recipients with proven or probable invasive mold disease (IMD) that received isavuconazole for ≥24 h as first-line or salvage therapy at 10 Spanish centers between September 2017 and November 2021. The primary efficacy outcome was clinical response (complete or partial resolution of attributable symptoms and findings) by weeks 6 and 12. Safety outcomes included the rates of treatment-emergent adverse events and premature isavuconazole discontinuation.

RESULTS

We included 81 SOT recipients that received isavuconazole for a median of 58.0 days because of invasive aspergillosis (n = 71) or mucormycosis (n = 10). Isavuconazole was used as first-line (72.8%) or salvage therapy due because of previous treatment-emergent toxicity (11.1%) or refractory IMD (7.4%). Combination therapy was common (37.0%), mainly with an echinocandin or liposomal amphotericin B. Clinical response by weeks 6 and 12 was achieved in 53.1% and 54.3% of patients, respectively, and was more likely when isavuconazole was administered as first-line single-agent therapy. At least 1 treatment-emergent adverse event occurred in 17.3% of patients, and 6.2% required premature discontinuation. Daily tacrolimus dose was reduced in two-thirds of patients by a median of 50.0%, although tacrolimus levels remained stable throughout the first month of therapy.

CONCLUSIONS

Isavuconazole is a safe therapeutic option for IMD in SOT recipients, with efficacy comparable to other patient groups.

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.

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.

Effect of posaconazole on the concentration of intravenous and oral cyclosporine in patients undergoing hematopoietic stem cell transplantation

PURPOSE

This study aimed to investigate the interactions between posaconazole (POS) and intravenously/orally administered cyclosporine A (CsA) in allogeneic hematopoietic stem cell transplant (HSCT) recipients.

METHODS

We included 118 allogeneic HSCT patients who received CsA and POS simultaneously between January 2017 and June 2020 in this study. The ratio of CsA blood concentration (ng/mL) to dosage (mg/day) (C/D) before and after POS initiation was compared.

RESULTS

After the initiation of POS, the level of CsA increased 1 to 2 times in 66% (78/118) of patients compared to those without POS. However, the CsA C/D ratio increased by more than threefold in 6% (7/118) of patients after POS initiation, with an increase of more than fourfold in two patients. The median C/D ratio of CsA increased from 0.89 to 1.23 (P < 0.001) and 0.78 to 1.22 (P < 0.001) after POS initiation when CsA was administered intravenously and orally, respectively. In patients who received POS at the time of transition from intravenous to oral CsA, the value increased from 1.01 to 1.38 (P = 0.001). The route of administration had no significant effect on the change in the CsA C/D ratio (P = 0.615). Additionally, we observed the time required for the C/D ratio to reach a plateau after POS initiation was similar on days 13, 8, and 15 under various scenarios.

CONCLUSION

POS treatment increased blood CsA levels. A large variability was found in the fold-change in the CsA C/D ratio. Therefore, CsA doses should be adjusted by closely monitoring the blood levels of CsA after POS initiation.

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.

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.

Acalabrutinib CYP3A mediated Drug-Drug Interactions: Clinical Evaluations and Physiologically-Based Pharmacokinetic Modeling to inform dose adjustment strategy

AIMS

Clinical drug interaction studies with itraconazole and rifampicin demonstrated acalabrutinib is a sensitive substrate of CYP3A. A PBPK model was developed based on the data of these studies. One of the active CYP3A metabolite ACP-5862 was identified but never studied in a drug interaction scenario. This study aims to evaluate both parent and metabolite exposure change with coadministration of moderate CYP3A inhibitors and its impact on safety and efficacy.

METHOD

In an open label, randomized, 2-period study, we investigated the effect of coadministration of fluconazole or isavuconazole on the pharmacokinetics of acalabrutinib. BTK receptor occupancy and safety was compared between different treatments. Experimental data was compared to PBPK simulation results.

RESULT

Least square means of Acalabrutinib Cmax and AUC increased 1.37(1.14-1.64)and 1.60(1.45-1.77)-fold in the presence of isavuconazole and 1.48(1.10-1.98) and 2.16(1.94-2.40) fold in the presence of fluconazole, respectively. For ACP-5862, these values are 0.72(0.63-0.82) and 0.91(0.86-0.97) fold for isavuconazole and 0.65(0.49-0.87) and 0.95(0.91-0.99) fold for fluconazole coadministration. The PBPK model was able to recover acalabrutinib and ACP-5862 PK profiles in the study. BTK receptor occupancy change was minimal in the presence of isavuconazole. There were no deaths, SAEs, or subject discontinuation due to AEs in this study. Mild (Grade 1) AEs were the only AEs reported during the study, by 17% of the study population.

CONCLUSION

Our results demonstrated the impact of fluconazole and isavuconazole on the pharmacokinetics of acalabrutinib and ACP-5862 and suggests no dose adjustment is needed for concomitant administration with moderate CYP3A inhibitors. Current PBPK model can be used to propose dose adjustment for drug interactions via CYP3A.

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.

Population Pharmacokinetics and Pharmacodynamic Target Attainment of Isavuconazole against Aspergillus fumigatus and Aspergillus flavus in Adult Patients with Invasive Fungal Diseases: Should Therapeutic Drug Monitoring for Isavuconazole Be Considered as Mandatory as for the Other Mold-Active Azoles?

Isavuconazole is a newer broad-spectrum triazole approved for the treatment of invasive fungal disease. The objective of this study was to conduct a population pharmacokinetic and pharmacodynamic analysis of isavuconazole in a retrospective cohort of hospitalized patients. A nonlinear mixed-effect approach with Monte Carlo simulations was conducted to assess the probability of target attainment (PTA) of an area under the concentration–time curve (AUC_{24 h})/minimum inhibitory concentration (MIC) ratio of 33.4 (defined as efficacy threshold against A. fumigatus and A. flavus) associated with a maintenance dose (MD) of 100, 200 and 300 mg daily after loading. The cumulative fraction of response (CFR) against the EUCAST MIC distributions of A. fumigatus and A. flavus was calculated as well. The proportion of trough concentrations (C_trough) exceeding a defined threshold of toxicity (>5.13 mg/L) was estimated. A total of 50 patients, with a median age of 61.5 years, provided 199 plasma isavuconazole concentrations. Invasive pulmonary aspergillosis was the prevalent type of infection and accounted for 80% (40/50) of cases. No clinical covariates were retained by the model. With the standard MD of 200 mg daily, CFRs were always ≥90% during the first two months of treatment. The risk of C_trough < 1.0 mg/L was around 1%, and that of C_trough > 5.13 mg/L was 27.7 and 39.2% at 28 and 60 days, respectively, due to isavuconazole accumulation over time. Our findings suggest that TDM for isavuconazole should not be considered as mandatory as for the other mold-active azoles voriconazole and posaconazole.

The Overview on the Pharmacokinetic and Pharmacodynamic Interactions of Triazoles

Second generation triazoles are widely used as first-line drugs for the treatment of invasive fungal infections, including aspergillosis and candidiasis. This class, along with itraconazole, voriconazole, posaconazole, and isavuconazole, is characterized by a broad range of activity, however, individual drugs vary considerably in safety, tolerability, pharmacokinetics profiles, and interactions with concomitant medications. The interaction may be encountered on the absorption, distribution, metabolism, and elimination (ADME) step. All triazoles as inhibitors or substrates of CYP isoenzymes can often interact with many drugs, which may result in the change of the activity of the drug and cause serious side effects. Drugs of this class should be used with caution with other agents, and an understanding of their pharmacokinetic profile, safety, and drug-drug interaction profiles is important to provide effective antifungal therapy. The manuscript reviews significant drug interactions of azoles with other medications, as well as with food. The PubMed and Google Scholar bases were searched to collect the literature data. The interactions with anticonvulsants, antibiotics, statins, kinase inhibitors, proton pump inhibitors, non-nucleoside reverse transcriptase inhibitors, opioid analgesics, benzodiazepines, cardiac glycosides, nonsteroidal anti-inflammatory drugs, immunosuppressants, antipsychotics, corticosteroids, biguanides, and anticoagulants are presented. We also paid attention to possible interactions with drugs during experimental therapies for the treatment of COVID-19.

Perpetrator Characteristics of Azole Antifungal Drugs on Three Oral Factor Xa Inhibitors Administered as a Microdosed Cocktail

Background

Factor Xa inhibitors (FXaIs) are increasingly used without having sufficient drug–drug interaction data. Using a microdosed cocktail methodology could support filling the knowledge gap quickly.

Methods

In a randomised crossover trial, we investigated the drug–drug interactions between six oral azole antifungals and a microdosed FXaI cocktail containing 25 µg rivaroxaban, 25 µg apixaban, and 50 µg edoxaban. Additionally, different enzyme activities were also monitored using a microdosed cocktail approach. The six different azole antifungals were administered in therapeutic doses over a 24 h period, while the microdosed cocktails were administered 1 h after administration of the azole antifungals.

Results

Ketoconazole and posaconazole were the strongest perpetrators, showing similar increases as apixaban (area under the concentration–time curve ratio [AUCR] 1.64 and 1.62, respectively) and edoxaban (AUCR 2.08 and 2.1, respectively), whereas ketoconazole increased rivaroxaban 2.32-fold but only increased posaconazole 1.37-fold. All other azole antifungals showed less perpetrator effects on the FXaIs. Cytochrome P450 (CYP) 3A inhibition was confirmed using microdosed midazolam, with ketoconazole also the most potent perpetrator (8.42-fold).

Conclusion

Drug–drug interactions for three victim drugs of the same drug class (FXaIs) with different clearance mechanisms can be studied using a microdosed cocktail approach. Using members of the azole antifungal drug class as perpetrators, multiple interactions can be studied in one trial, and a more detailed insight into the underlying interaction mechanisms is possible.

Clinical Trial Registration

EudraCT number: 2017-004453-16.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01051-9.

Model-based comparative analysis of rifampicin and rifabutin drug-drug interaction profile

Rifamycins are widely used for treating mycobacterial and staphylococcal infections. Drug-drug interactions (DDI) caused by rifampicin (RIF) is a major issue. We used a model-based approach to predict the magnitude of DDI with RIF and rifabutin (RBT) for 217 cytochrome P450 (CYP) substrates. On average, DDI caused by low-dose RIF were twice more potent than those caused by RBT. Contrary to RIF, RBT appears unlikely to cause severe DDI, even with sensitive CYP substrates.

Comparative effects of fluconazole, posaconazole, and isavuconazole upon tacrolimus and cyclosporine serum concentrations

INTRODUCTION

Calcineurin inhibitors are commonly used in hematopoietic stem cell transplant (HSCT) patients to prevent graft versus host disease, but as CYP3A4 substrates they are frequently involved in drug-drug interactions. The purpose of this study is to characterize the effects of isavuconazole, fluconazole, and posaconazole on tacrolimus and cyclosporine serum concentrations and dose adjustments in allogeneic HSCT patients.

METHODS

This retrospective study included patients admitted to Oregon Health and Science University between April 2008 and December 2018 who underwent hematopoietic stem cell transplantation and received concomitant tacrolimus or cyclosporine and fluconazole, isavuconazole or posaconazole therapy. Data on patient characteristics, drug dosing, and serum drug concentrations were collected through chart review, and descriptive statistics were used to summarize the results.

RESULTS

A total of 139 patients were included in this study. We found fluconazole initiation leads to a 25% reduction in both tacrolimus and cyclosporine doses in order to maintain goal serum concentrations. Posaconazole and isavuconazole initiation requires tacrolimus dose reductions by 53% and 21%, respectively.

CONCLUSIONS

Based on our experience, FLC, POS, and ISA initiation may require CNI dose reductions and close monitoring of CNI levels to ensure levels remain within goal serum concentrations. Larger studies are needed to fully quantify the percentage in CNI dose reductions and characterize differences among these antifungals.

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.

In Vitro Activity of Novel Antifungal Olorofim against Filamentous Fungi and Comparison to Eight Other Antifungal Agents

Olorofim is a novel antifungal drug that belongs to the orotomide drug class which inhibits fungal dihydroorotate dehydrogenase (DHODH), thus halting pyrimidine biosynthesis and ultimately DNA synthesis, cell growth and division. It is being developed at a time when many invasive fungal infections exhibit antifungal resistance or have limited treatment options. The goal of this study was to evaluate the in vitro effectiveness of olorofim against a large collection of recently isolated, clinically relevant American mold isolates. In vitro antifungal activity was determined for 246 azole-susceptible Aspergillus fumigatus isolates, five A. fumigatus with TR₃₄/L98H-mediated resistance, 19 Rhizopus species isolates, 21 Fusarium species isolates, and one isolate each of six other species of molds. Olorofim minimum inhibitory concentrations (MICs) were compared to antifungal susceptibility testing profiles for amphotericin B, anidulafungin, caspofungin, isavuconazole, itraconazole, micafungin, posaconazole, and voriconazole. Olorofim MICs were significantly lower than those of the echinocandin and azole drug classes and amphotericin B. A. fumigatus wild type and resistant isolates shared the same MIC50 = 0.008 μg/mL. In non-Aspergillus susceptible isolates (MIC ≤ 2 μg/mL), the geometric mean (GM) MIC to olorofim was 0.54 μg/mL with a range of 0.015–2 μg/mL. Olorofim had no antifungal activity (MIC ≥ 2 μg/mL) against 10% of the collection (31 in 297), including some isolates from Rhizopus spp. and Fusarium spp. Olorofim showed promising activity against A. fumigatus and other molds regardless of acquired azole resistance.

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.

Choosing Antifungals for the Midostaurin-Treated Patient: Does CYP3A4 Outweigh Recommendations? A Brief Insight from Real Life

INTRODUCTION

Patients treated with midostaurin and chemotherapy are at risk of invasive fungal disease. Prophylactic posaconazole is recommended for these patients, but posaconazole strongly inhibits the CYP3A4 isozyme that metabolizes midostaurin. Posaconazole therefore introduces a risk of patient's overexposure to midostaurin.

METHODS

Blood samples were obtained from 4 patients treated with midostaurin for newly diagnosed FLT3-mutAML. Patients had received a concomitant treatment with posaconazole, isavuconazole, or micafungin, respectively. All blood samples were drawn before daily dose administration of midostaurin.

RESULTS

Posaconazole caused a ≥8-fold increase of midostaurin plasma levels at through, which was accompanied by a decreased plasma exposure to O-demethylated or hydroxylated midostaurin metabolites. We also show that hematologists react to risk perception by replacing posaco-nazole with antifungals like micafungin or isavuconazole, which lack a strong inhibition of CYP3A4 and fail to modify midostaurin pharmacokinetics but are not formally recommended in these settings.

DISCUSSION

In real-life scenarios, concerns about CYP3A4 inhibition may outweigh compliance with recommendations. Large studies are needed to survey the risk:benefit of hematologist's decision to replace posaconazole with other antifungals.

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.

Drug-Drug Interaction Studies With Oral Contraceptives: Pharmacokinetic/Pharmacodynamic and Study Design Considerations

Oral contraceptives (OCs) are the most widely used form of birth control among women of childbearing potential. Knowledge of potential drug-drug interactions (DDIs) with OCs becomes imperative to provide information on the medication to women of childbearing potential and enable their inclusion in clinical trials, especially if the new molecular entity is a teratogen. Although a number of DDI guidance documents are available, they do not provide recommendations for the design and conduct of OC DDI studies. The evaluation of DDI potential of a new molecular entity and OCs is particularly challenging because of the availability of a wide variety of combinations of hormonal contraceptives, different doses of the ethinyl estradiol, and different metabolic profiles of the progestin component. The aim of this review is to comprehensively discuss factors to be considered such as pharmacokinetics (PK), pharmacodynamics (PD), choice of OC, and study population for the conduct of in vivo OC DDI studies. In this context, metabolic pathways of OCs, the effect of enzyme inhibitors and inducers, the role of sex hormone-binding globulin in the PK of progestins, current evidence on OC DDIs, and the interpretation of PD end points are reviewed. With the emergence of new tools like physiologically based PK modeling, the decision to conduct an in vivo study can be made with much more confidence. This review provides a comprehensive overview of various factors that need to be considered in designing OC DDI studies and recommends PK-based DDI studies with PK end points as adequate measures to establish clinical drug interaction and measurement of PD end points when there is basis for PD interaction.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

The role of antibiotic pharmacokinetic studies performed post-licensing

Post-licensing pharmacometric studies can provide a better understanding of the pharmacokinetic (PK) alterations in special patient populations and may lead to better clinical outcomes. Some patient populations exhibit markedly different pathophysiology to general ward patients or healthy individuals. This may be developmental (paediatric patients), a manifestation of an underlying disease pathology (patients with obesity or haematological malignancies) or due to medical interventions (critically ill patients receiving extracorporeal therapies). This paper outlines the factors that affect the PK of special patient populations and describes some novel methods of antimicrobial administration that may increase antimicrobial concentrations at the site of infection and improve treatment of severe infection.

Antifungal therapeutic drug monitoring: focus on drugs without a clear recommendation

BACKGROUND

The goal of therapeutic drug monitoring (TDM) is to determine the appropriate exposure of difficult-to-manage medications to optimize the clinical outcomes in patients in various clinical situations. Concerning antifungal treatment, and knowing that this procedure is expensive and time-consuming, TDM is particularly recommended for certain systemic antifungals: i.e., agents with a well-defined exposure-response relationship and unpredictable pharmacokinetic profile or narrow therapeutic index. Little evidence supports the routine use of TDM for polyenes (amphotericin B), echinocandins, fluconazole or new azoles such as isavuconazole, despite the fact that a better understanding of antifungal exposure may lead to a better response.

AIMS

The aim of this work is to review published pharmacokinetic/pharmacodynamic data on systemically administered antifungals, focusing on those for which monitoring is not routinely recommended by experts.

SOURCES

A MEDLINE search of the literature in English was performed introducing the following search terms: amphotericin B, fluconazole, itraconazole, voriconazole, posaconazole, triazoles, caspofungin, micafungin, anidulafungin, echinocandins, pharmacokinetics, pharmacodynamics, and therapeutic drug monitoring. Review articles and guidelines were also screened.

CONTENT

This review collects different pharmacokinetic/pharmacodynamic aspects of systemic antifungals and summarizes recent threshold values for clinical outcomes and adverse events. Although for polyenes, echinocandins, fluconazole and isavuconazole extensive clinical validation is still required for a clear threshold and a routine monitoring recommendation, particular points such as liposome structure or complex pathophysiological conditions affecting final exposure are discussed. For the rest, their better-defined exposure-response/toxicity relationships allow access to useful threshold values and to justify routine monitoring. Additionally, clinical data are needed to better define thresholds that can minimize the development of antifungal resistance.

IMPLICATIONS

General TDM for all systemic antifungals is not recommended; however, this approach may help to establish an adequate antifungal exposure for a favourable response, prevention of toxicity or development of resistance in special clinical circumstances.

Antifungal prophylaxis and novel drugs in acute myeloid leukemia: the midostaurin and posaconazole dilemma

With the advent of new targeted drugs in hematology and oncology patient prognosis is improved. Combination with antifungal prophylaxis challenges clinicians due to pharmacological profiles prone to drug–drug interactions (DDI). Midostaurin is a novel agent for FLT3-TKD/-ITD^mut-acute myeloid leukemia (AML) and metabolized via cytochrome P450 3A4 (CYP3A4). Posaconazole is a standard of care antifungal agent used for prophylaxis during induction treatment of AML and a strong CYP3A4 inhibitor. Concomitant administration of both drugs leads to elevated midostaurin exposure. Both drugs improve overall survival at low numbers needed to treat. The impact of CYP3A4-related DDI remains to be determined. Severe adverse events have been observed; however, it remains unclear if they can be directly linked to DDI. The lack of prospective clinical studies assessing incidence of invasive fungal infections and clinical impact of DDI contributes to neglecting live-saving antifungal prophylaxis. Management strategies to combine both drugs have been proposed, but evidence on which approach to use is scarce. In this review, we discuss several approaches in the specific clinical setting of concomitant administration of midostaurin and posaconazole and give examples from everyday clinical practice. Therapeutic drug monitoring will become increasingly important to individualize and personalize antineoplastic concomitant and antifungal treatment in the context of DDI. Pharmaceutical companies addressing the issue in clinical trials may take a pioneer role in this field. Other recently developed and approved drugs for the treatment of AML likely inhere potential of DDI marking a foreseeable issue in future treatment of this life-threatening disease.

Proposal of a Safe and Effective Study Design for CYP3A-Mediated Drug-Drug Interactions

Numerous drug-drug interaction (DDI) trials have to be conducted in healthy volunteers based on current regulatory guidelines. Because the worst-case scenario of strong cytochrome P450 (CYP) inhibitors has to be tested, the results and their validity have to be balanced with the risk to volunteer safety. The use of ketoconazole in clinical DDI studies has been discouraged by regulatory agencies due to an alleged risk of liver injury. In order to reduce the risk to healthy volunteers, we carried out a study with single-day exposure to each of 6 perpetrator azole fungistatic drugs. They were evaluated regarding their CYP3A inhibition using microdosed midazolam and a limited sampling strategy. Ratios of areas under the concentration-time curves ranged from 1.93 with isavuconazole to 8.42 with ketoconazole. The highest number of adverse events occurred with voriconazole, followed by ketoconazole; 2 dropouts occurred due to adverse events following itraconazole administration. Literature data on adverse events of azole fungistatic drugs in DDI trials are rare and inconclusive. Only in recent years with the newer drugs are they more precise and reliable. It can be concluded that the duration of preexposure of perpetrator drugs can be reduced to 1 hour before administration of the victim drug. This still can be sufficient to achieve the scientific objectives of the trial with the lowest possible risk.

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.

Altered Pharmacokinetics and Dosing of Liposomal Amphotericin B and Isavuconazole during Extracorporeal Membrane Oxygenation

Drug pharmacokinetics may be significantly altered in patients receiving extracorporeal membrane oxygenation (ECMO). Ensuring the optimized effective dosing of antimicrobials on ECMO remains a challenge. To date, limited data are available regarding the optimal use of amphotericin and triazoles during ECMO. We report a case of altered pharmacokinetics, insufficient liposomal amphotericin B and isavuconazole levels, and the need for escalated doses during ECMO in a patient with severe acute respiratory distress syndrome secondary to pulmonary blastomycosis. A 2-fold increase in the standard total daily dose of both drugs was necessary to overcome low serum concentrations thought to be secondary to drug loss from ECMO circuit sequestration. These findings have important implications for optimizing antimicrobial therapy in patients receiving ECMO to maximize therapeutic efficacy. The use of therapeutic drug monitoring for patients receiving antimicrobial therapy with concurrent ECMO may facilitate appropriate drug dosing to achieve adequate serum concentrations and optimize favorable patient outcomes. Further studies exploring antimicrobial pharmacokinetics during ECMO are needed to inform dosing recommendations in critically ill patients.

Structural Perspectives of the CYP3A Family and Their Small Molecule Modulators in Drug Metabolism

Cytochrome P450 enzymes function to catalyze a wide range of reactions, many of which are critically important for drug response. Members of the human cytochrome P450 3A (CYP3A) family are particularly important in drug clearance, and they collectively metabolize more than half of all currently prescribed medications. The ability of these enzymes to bind a large and structurally diverse set of compounds increases the chances of their modulating or facilitating drug metabolism in unfavorable ways. Emerging evidence suggests that individual enzymes in the CYP3A family play discrete and important roles in catalysis and disease progression. Here we review the similarities and differences among CYP3A enzymes with regard to substrate recognition, metabolism, modulation by small molecules, and biological consequence, highlighting some of those with clinical significance. We also present structural perspectives to further characterize the basis of these comparisons.

Antifungal drugs: What brings the future?

The high burden and growing prevalence of invasive fungal infections (IFIs), the toxicity and interactions associated with current antifungal drugs, as well as the increasing resistance, ask for the development of new antifungal drugs, preferably with a novel mode of action. Also, the availability of oral or once-weekly alternatives would enable ambulatory treatment resulting in an improved patient's comfort and therapy adherence. However, only one new azole and two new posaconazole-formulations were marketed over the last decade. This review focuses on the antifungal drugs in the pipeline undergoing clinical evaluation. First, the newest azole, isavuconazole, with its improved safety profile and reduction in DDIs, will be discussed. Moreover, there are two glucan synthase inhibitors (GSIs) in the antifungal pipeline: rezafungin (CD101), a long-acting echinocandin with an improved stability that enables once weekly administration, and SCY-078, an orally available GSI with efficacy against azole- and echinocandin resistant isolates. A new oral formulation of amphotericin B will also be presented. Moreover, the first representative of a new antifungal class, the orotomides, with a broad spectrum and no cross-resistance with current antifungal classes, will be discussed. Finally, an overview of other antifungals that are still in earlier clinical development phases, is provided.

Invasive pulmonary aspergillosis and pulmonary tuberculosis in a patient treated with infliximab for Crohn's disease

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Pulmonary TB together with invasive pulmonary aspergillosis due to infliximab therapy has been occasionally described.

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Other than tuberculosis reactivation, TNF-α antagonists may be associated with other opportunistic infections such as invasive aspergillosis.

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Interactions among rifamycins, antifungal and antiarrhythmic drugs are complex and may require the choice of second line therapies.

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Isavuconazole may have a better interaction profile with amiodarone and antitubercular therapy than voriconazole.

We report a case of concurrent development of active pulmonary tuberculosis and invasive pulmonary aspergillosis (IPA) in a patient who received therapy with infliximab for Crohn’s disease. He has been treated with antitubercular therapy and liposomal amphotericin B for 8 weeks. His clinical course was complicated by paroxysmal atrial fibrillation requiring maintenance therapy with amiodarone, respiratory failure due both to pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamases (ESBL)-producing Klebsiella pneumoniae and pleural effusion requiring chest drainage. At discharge, a maintenance regimen based on the administration of isavuconazole 200 mg daily, moxifloxacin 400 mg daily and isoniazid 300 mg daily was chosen to avoid multiple drug-drug interaction between rifamycins, antifungal triazole agents and antiarrhythmic drugs. At 3 months of follow-up his clinical conditions were dramatically improved, high resolution chest tomography (HRCT) showed reduction of parenchymal lesions and no changes both in sinus rhythm and QTc interval were noticed. Besides the complexity and the peculiarity of the clinical scenario, this case underlines the risk of invasive fungal infections linked to the administration of TNF-α antagonists in gastroenterological setting and the importance of accurate evaluation of drug-drug interactions when choosing the antimicrobial therapies.

Isavuconazole Kinetic Exploration for Clinical Practice

BACKGROUND

Isavuconazole is a new antifungal prodrug for the treatment of invasive aspergillosis and mucormycosis. As no clear pharmacokinetic-pharmacodynamic relationship has been established for patients, therapeutic drug monitoring is not currently required. However, as isavuconazole is a new drug, clinicians are sometimes sceptical about the exposure achieved in their patients and seek pharmacokinetic exploration. A minimal response consists of determining that the patient's pharmacokinetic profile agrees with profiles reported by Desai et al. using concentrations from the SECURE study.

METHODS

Based on one concentration and Desai et al.'s population-pharmacokinetic model, it is possible to estimate a patient's most likely pharmacokinetic profile. If a patient's pharmacokinetic profile is close to the profiles reported by Desai et al., therapeutic drug monitoring is not required. In contrast, when the pharmacokinetic profile differs from the Desai et al. profiles, isavuconazole concentration monitoring and pharmacokinetic profile modeling are the only methods for obtaining information on a patient's exposure and the efficacy of isavuconazole.

RESULTS

Four patients presented with surprising pharmacokinetic profiles, unexplained by drug interactions or cytochrome P450 3A4/5 polymorphisms. For two of them, a drug dosage adjustment was proposed and applied by clinicians, together with a check for a new pharmacokinetic profile a few days later.

CONCLUSIONS

Collecting one blood sample just before the first maintenance dose to make an early estimation of the patient's most likely pharmacokinetic profile is one method of identifying patients with outlier pharmacokinetic behavior.

Validation of an Isavuconazole High-Performance Liquid Chromatography Assay in Plasma for Routine Therapeutic Drug Monitoring Applications

BACKGROUND

Isavuconazole is a triazole antifungal agent for treatment of invasive aspergillosis and mucormycosis. At present, it is unclear whether a therapeutic drug monitoring (TDM) of isavuconazole would be necessary. The aim of the investigation was to validate a high-performance liquid chromatography (HPLC) assay for routine applications.

METHODS

An HPLC assay for routine determination of isavuconazole in plasma has been adapted and validated. The assay used the reagents and HPLC column provided by the ChromSystems HPLC Kit for TDM of itraconazole, posaconazole, and voriconazole. Isocratic flow rate was set at 1.0 mL/min. Detection was performed using a fluorescence detector with excitation wavelength set at 261 nm and emission wavelength set at 366 nm.

RESULTS

The assay was linear between 0.15 and 10 mg/L with intraday and interday imprecision and accuracy <10% (<20% at lower limit of quantification). The method was applied to routine TDM of 7 patients after hematopoietic stem cell transplantation (n = 31 samples). In these patients, trough levels ranged from 0.45 to 3.06 mg/L (median 1.44 mg/L).

CONCLUSIONS

A robust and simple HPLC assay of isavuconazole in plasma for routine TDM applications is presented.

Systematic review and network meta-analysis of clinical outcomes associated with isavuconazole versus relevant comparators for patients with invasive aspergillosis

OBJECTIVES

Voriconazole, amphotericin B (AmB) formulations, and isavuconazole are all included in guideline recommendations for treatment of patients with invasive aspergillosis (IA) but the relative efficacy of isavuconazole versus AmB formulations has not been directly compared. We aimed to estimate the relative efficacy of isavuconazole compared with AmB deoxycholate (AmB-D), liposomal AmB (L-AmB), and voriconazole for the treatment of patients with proven/probable IA.

METHODS

Nine literature databases were screened for randomized controlled trials comparing treatments with any of voriconazole, AmB-D, L-AmB and isavuconazole for treatment of proven/probable IA. Articles meeting the criteria were included in a meta-analysis to determine the efficacy of AmB-D, L-AmB and voriconazole relative to isavuconazole based on all-cause mortality (ACM) and overall response using a fixed-effects model.

RESULTS

Four articles were identified that compared L-AmB with AmB-D (Study 1), standard-dose L-AmB (3-5 mg/kg/day) with high-dose L-AmB (10 mg/kg/day; Study 2), voriconazole with AmB-D (Study 3), and isavuconazole with voriconazole (Study 4). In the network meta-analysis, isavuconazole was statistically superior to AmB-D on both ACM (odds ratio [95% credible intervals] shown as natural log, 1.00 [0.26, 1.74]) and overall response (-1.39 [-2.21, -0.63]). Differences between isavuconazole, and standard-dose L-AmB, high-dose L-AmB and voriconazole were not statistically significant for either ACM (0.18 [-1.17, 1.53], 0.50 [-1.11, 2.13] and 0.32 [-0.19, 0.84], respectively) or overall response (-0.99 [-2.21, 0.29], -0.89 [-2.41, 0.65] and 0.06 [-0.43, 0.57], respectively).

CONCLUSIONS

This data suggests that the efficacy of isavuconazole for treatment of IA is superior to AmB-D and comparable with both L-AmB and voriconazole.

Pharmacokinetics of Intravenous Isavuconazole in Solid-Organ Transplant Recipients

Isavuconazole may be useful in treating and preventing fungal infections in solid-organ transplant (SOT) recipients due to its safety profile and activity against Aspergillus and some Mucorales Isavuconazole has favorable pharmacokinetics based on clinical trials in various patient populations, but data are limited in SOT recipients. We evaluated the steady-state pharmacokinetics of isavuconazole in 26 SOT recipients receiving the drug intravenously for prophylaxis. There was moderate interpatient variability in isavuconazole pharmacokinetic parameters (coefficients of variation of 51% for the area under the plasma concentration-versus-time curve [AUC] and 59% for the trough plasma concentration [C _trough]). AUC and steady-state C _trough were significantly lower in women, patients with a body mass index of ≥18.5 kg/m², and those receiving hemodialysis. Trough plasma concentrations were highly correlated with AUCs (R ² = 0.94) and can serve as a suitable measure of isavuconazole exposure in patients. In conclusion, moderate interpatient variability in isavuconazole exposure, the identification of factors associated with lower exposure, the recognition that C _trough is a surrogate marker for AUC, and the availability of a simple analytical method suggest that therapeutic drug monitoring (TDM) may be useful for guiding treatment in at least some SOT recipients. Future studies are needed to correlate isavuconazole exposure with patients' clinical outcomes and to determine the clinical role of TDM.

Drug–Drug Interaction Between Isavuconazole and Tacrolimus: Is Empiric Dose Adjustment Necessary?

A paucity of data currently exists regarding drug–drug interaction (DDI) with tacrolimus and isavuconazole coadministration. Current literature provides conflicting recommendations on whether an empiric tacrolimus dose reduction is necessary when coadministered with isavuconazole. A 47-year-old African American female with acute lymphoblastic leukemia underwent an allogenic stem cell transplant (alloSCT) and was subsequently placed on routine posttransplant therapy including tacrolimus for immunosuppression and posaconazole for antifungal prophylaxis. Tacrolimus was empirically dose reduced due to the expected DDI with posaconazole based on current recommendations. Due to a persistently prolonged QTc interval and need for mold coverage, antifungal prophylaxis was ultimately changed to isavuconazole at standard recommended dosing. Tacrolimus was empirically dose reduced by 40% based on limited available literature at the time; however, tacrolimus trough concentrations subsequently declined, requiring an increase in tacrolimus dose to maintain therapeutic trough concentrations. Adequate isavuconazole absorption was documented through pharmacokinetic and pharmacodynamic data by measuring an isavuconazole trough concentration and directly observing isavuconazole’s shortening effect on the QTc interval, respectively. Our experience in an alloSCT patient suggests that an empiric tacrolimus dose reduction is not required when isavuconazole is initiated, but close tacrolimus therapeutic drug monitoring should rather be performed to guide tacrolimus dosing.