Drug-drug interactions between triazole antifungal agents used to treat invasive aspergillosis and immunosuppressants metabolized by cytochrome P450 3A4

Invasive aspergillosis in solid organ transplant patients: diagnosis, prophylaxis, treatment, and assessment of response

BACKGROUND

Invasive aspergillosis (IA) is a rare complication in solid organ transplant (SOT) recipients. Although IA has significant implications on graft and patient survival, data on diagnosis and management of this infection in SOT recipients are still limited.

METHODS

Discussion of current practices and limitations in the diagnosis, prophylaxis, and treatment of IA and proposal of means of assessing treatment response in SOT recipients.

RESULTS

Liver, lung, heart or kidney transplant recipients have common as well as different risk factors to the development of IA, thus each category needs a separate evaluation. Diagnosis of IA in SOT recipients requires a high degree of awareness, because established diagnostic tools may not provide the same sensitivity and specificity observed in the neutropenic population. IA treatment relies primarily on mold-active triazoles, but potential interactions with immunosuppressants and other concomitant therapies need special attention.

CONCLUSIONS

Criteria to assess response have not been sufficiently evaluated in the SOT population and CT lesion dynamics, and serologic markers may be influenced by the underlying disease and type and severity of immunosuppression. There is a need for well-orchestrated efforts to study IA diagnosis and management in SOT recipients and to develop comprehensive guidelines for this population.

The novel fungal CYP51 inhibitor VT-1598 displays classic dose-dependent antifungal activity in murine models of invasive aspergillosis

Aspergillus spp. infections remain a global concern, with ∼30% attributable mortality of invasive aspergillosis (IA). VT-1598 is a novel fungal CYP51 inhibitor designed for exquisite selectivity versus human CYP enzymes to achieve a maximal therapeutic index and therefore maximal antifungal efficacy. Previously, its broad-spectrum in vitro antifungal activity was reported. We report here the pharmacokinetics (PK) and pharmacodynamics (PD) of VT-1598 in neutropenic mouse models of IA. The plasma area-under-the-curve (AUC) of VT-1598 increased nearly linearly between 5 and 40 mg/kg after 5 days of QD administration (155 and 1033 μg*h/ml, respectively), with a further increase with 40 mg/kg BID dosing (1354 μg*h/ml). When A. fumigatus isolates with in vitro susceptibilities of 0.25 and 1.0 μg/ml were used in a disseminated IA model, VT-1598 treatment produced no decrease in kidney fungal burden at QD 10 mg/kg, intermediate decreases at QD 20 mg/kg and maximum or near maximum decreases at 40 mg/kg QD and BID. The PK/PD relationships of AUCfree/MIC for 1-log killing for the two strains were 5.1 and 1.6 h, respectively, similar to values reported for approved CYP51 inhibitors. In a survival study where animals were observed for 12 days after the last treatment, survival was 100% at the doses tested (20 and 40 mg/kg QD), and fungal burden remained suppressed even though drug wash-out was complete. Similar dose-dependent reductions in lung fungal burden were observed in a pulmonary model of IA. These data strongly support further exploration of VT-1598 for the treatment of this lethal mold infection.

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.

Invasive fungal infection before and after liver transplantation

Invasive infections are a major complication before liver transplantation (LT) and in the early phase after surgery. There has been an increasing prevalence of invasive fungal disease (IFD), especially among the sickest patients with decompensated cirrhosis and acute-on-chronic liver failure, who suffer from a profound state of immune dysfunction and receive intensive care management. In such patients, who are listed for LT, development of an IFD often worsens hepatic and extra-hepatic organ dysfunction, requiring a careful evaluation before surgery. In the post-transplant setting, the burden of IFD has been reduced after the clinical advent of antifungal prophylaxis, even if several major issues still remain, such as duration, target population and drug type(s). Nevertheless, the development of IFD in the early phase after surgery significantly impairs graft and patient survival. This review outlines presentation, prophylactic and therapeutic strategies, and outcomes of IFD in LT candidates and recipients, providing specific considerations for clinical practice.

Posaconazole aggravates vincristine-related hypertension in children with acute lymphoblastic leukemia: a case report

Vincristine-related secondary hypertension is rare. This study reports two children who were treated with vincristine for acute lymphoblastic leukemia (ALL) and posaconazole for fungal infections who experienced vincristine-related secondary hypertension. Blood pressure normalized in both children after halting the drugs and providing antihypertensive treatment. Thus, posaconazole can interact with vincristine and induce secondary hypertension in children with ALL. As an adverse event, this interaction is a rare occurrence.

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.

Predictors of tacrolimus pharmacokinetic variability: current evidences and future perspectives

INTRODUCTION

In kidney transplantation, tacrolimus (TAC) is at the cornerstone of current immunosuppressive strategies. Though because of its narrow therapeutic index, it is critical to ensure that TAC levels are maintained within this sharp window through reactive adjustments. This would allow maximizing efficiency while limiting drug-associated toxicity. However, TAC high intra- and inter-patient pharmacokinetic (PK) variability makes it more laborious to accurately predict the appropriate dosage required for a given patient.

AREAS COVERED

This review summarizes the state-of-the-art knowledge regarding drug interactions, demographic and pharmacogenetics factors as predictors of TAC PK. We provide a scoring index for each association to grade its relevance and we present practical recommendations, when possible for clinical practice.

EXPERT OPINION

The management of TAC concentration in transplanted kidney patients is as critical as it is challenging. Recommendations based on rigorous scientific evidences are lacking as knowledge of potential predictors remains limited outside of DDIs. Awareness of these limitations should pave the way for studies looking at demographic and pharmacogenetic factors as well as gut microbiota composition in order to promote tailored treatment plans. Therapeutic approaches considering patients' clinical singularities may help allowing to maintain appropriate concentration of TAC.

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

INTRODUCTION

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

RESULTS

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

CONCLUSION

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

Tablets or oral suspension for posaconazole in lung transplant recipients? Consequences for trough concentrations of tacrolimus and everolimus

AIMS

A new formulation of posaconazole (PCZ), delayed-release tablets (PCZ-tab), increases PCZ bioavailability and plasma trough concentrations (C_min ) over those achieved with an oral suspension (PCZ-susp). PCZ is an inhibitor of cytochrome P450 3A4 and P-glycoprotein. We therefore investigated the impact of PCZ-tab treatment on blood C_min and doses of tacrolimus (TAC) and everolimus (EVR).

METHODS

Eighteen lung transplant patients receiving TAC (n = 13) or TAC + EVR (n = 5) between June 2015 and March 2016 were retrospectively included. Ten of these patients received both PCZ-tab and PCZ-susp (i.e. switched patients); the other 8 received only PCZ-tab. Plasma C_min of PCZ (n = 64), blood C_min of TAC (n = 299) and EVR (n = 80) were determined during routine therapeutic drug monitoring by liquid chromatography-tandem mass spectrometry.

RESULTS

PCZ C_min on PCZ-tab treatment (n = 48) was 2.5 times higher than that on PCZ-susp therapy (n = 16), for both PCZ patients (P < .0001) and for switched patients (P = .003). PCZ initiation, regardless of galenic form, increased TAC and EVR C_min adjusted for dose (D), 3-fold and 3.5-fold, respectively (P < .0001 for both). PCZ-tab treatment was associated with a higher TAC C_min /D (PCZ-tab vs PCZ-susp: 0.004 ± 0.004 L^-1 vs 0.009 ± 0.006 L^-1 , P < .0001) and lower TAC daily dose than PCZ-susp (PCZ-tab vs PCZ-susp: 1.08 ± 0.92 vs 2.32 ± 1.62 mg d^-1 , P < .0001). EVR C_min /D was higher and EVR dose tended to be lower on PCZ-tab than on PCZ-susp.

CONCLUSION

The greater PCZ exposure achieved during PCZ-tab treatment increased drug-drug interactions with TAC and EVR, resulting in greater exposure, potentially exposing patients to higher risks of adverse effects.

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.

Treatment of invasive fungal diseases in cancer patients-Revised 2019 Recommendations of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO)

BACKGROUND

Invasive fungal diseases remain a major cause of morbidity and mortality in cancer patients undergoing intensive cytotoxic therapy. The choice of the most appropriate antifungal treatment (AFT) depends on the fungal species suspected or identified, the patient's risk factors (eg length and depth of granulocytopenia) and the expected side effects.

OBJECTIVES

Since the last edition of recommendations for 'Treatment of invasive fungal infections in cancer patients' of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO) in 2013, treatment strategies were gradually moving away from solely empirical therapy of presumed or possible invasive fungal diseases (IFDs) towards pre-emptive therapy of probable IFD.

METHODS

The guideline was prepared by German clinical experts for infections in cancer patients in a stepwise consensus process. MEDLINE was systematically searched for English-language publications from January 1975 up to September 2019 using the key terms such as 'invasive fungal infection' and/or 'invasive fungal disease' and at least one of the following: antifungal agents, cancer, haematological malignancy, antifungal therapy, neutropenia, granulocytopenia, mycoses, aspergillosis, candidosis and mucormycosis.

RESULTS

AFT of IFDs in cancer patients may include not only antifungal agents but also non-pharmacologic treatment. In addition, the armamentarium of antifungals for treatment of IFDs has been broadened (eg licensing of isavuconazole). Additional antifungals are currently under investigation or in clinical trials.

CONCLUSIONS

Here, updated recommendations for the treatment of proven or probable IFDs are given. All recommendations including the levels of evidence are summarised in tables to give the reader rapid access to key information.

Administration and Dosing of Systemic Antifungal Agents in Pediatric Patients

Neonates and immunosuppressed/immunocompromised pediatric patients are at high risk of invasive fungal diseases. Appropriate antifungal selection and optimized dosing are imperative to the successful prevention and treatment of these life-threatening infections. Conventional amphotericin B was the mainstay of antifungal therapy for many decades, but dose-limiting nephrotoxicity and infusion-related adverse events impeded its use. Despite the development of several new antifungal classes and agents in the past 20 years, and their now routine use in at-risk pediatric populations, data to guide the optimal dosing of antifungals in children are limited. This paper reviews the spectra of activity for approved antifungal agents and summarizes the current literature specific to pediatric patients regarding pharmacokinetic/pharmacodynamic data, dosing, and therapeutic drug monitoring.

Tacrolimus blood concentration increase depends on administration route when combined with voriconazole in pediatric stem cell transplant recipients

BACKGROUND

Understanding of TAC pharmacokinetics is required to avoid both overdosing and underdosing. VRCZ is known to increase the TAC blood concentration by inhibiting CYP3A4; however, detailed, practical information on pediatric cases is still scarce. Herein, we investigated the association between the TAC blood concentration and dosage focusing on the administration route and concomitant use of VRCZ in children.

METHODS

In total, 38 children who received TAC during stem cell transplantation at our hospital between January 2013 and April 2018 were included. The ratio of the TAC blood concentration (ng/mL) to dosage (mg/kg/day) (C/D) was calculated at the last continuous intravenous infusion (C/Div) and after switching to oral administration (C/Dpo).

RESULTS

Patients with VRCZ (n = 14) showed a higher C/D regardless of administration route (median C/Div: with VRCZ/without VRCZ = 832/643, median C/Dpo: with VRCZ/without VRCZ = 339/45). Additionally, the (C/Div)/(C/Dpo) was about one-fourth in cases with VRCZ; the median (C/Div)/(C/Dpo) was 3.3 for cases with VRCZ and 13.5 for cases without VRCZ. Interestingly, the increase in the TAC blood concentration due to VRCZ was higher when TAC was administered orally, especially in adolescent patients.

CONCLUSIONS

To obtain an optimal TAC blood concentration, dose adjustment based on multiple factors, such as administration route, concomitant use of VRCZ, and age, is required.

A phase 1/1b study of PUR1900, an inhaled formulation of itraconazole, in healthy volunteers and asthmatics to study safety, tolerability and pharmacokinetics

AIMS

Oral itraconazole has variable pharmacokinetics and risks of adverse events associated with high plasma exposure. An inhalation formulation of itraconazole (PUR1900) is being developed to treat allergic bronchopulmonary aspergillosis, an allergic inflammatory disease occurring in asthmatics and patients with cystic fibrosis.

METHODS

A 3-part, open-label Phase 1 study was conducted to evaluate safety, tolerability and pharmacokinetics of PUR1900. Healthy volunteers (n = 5-6/cohort) received either single (Part 1) or multiple (Part 2) ascending doses of PUR1900 for up to 14 days. In Part 3 stable, adult asthmatics received a single dose of 20 mg PUR1900 or 200 mg of oral Sporanox (itraconazole oral solution) in a 2-period randomized cross-over design. Itraconazole plasma and sputum concentrations were evaluated.

RESULTS

None of the adverse events considered as at least possibly related to study treatment were moderate or severe, and none were classed as serious. The most common was the infrequent occurrence of mild cough. Itraconazole plasma exposure increased with increasing doses of PUR1900. After 14 days, PUR1900 resulted in plasma exposure (area under the concentration-time curve up to 24 h) 106- to 400-fold lower across doses tested (10-35 mg) than steady-state exposure reported for oral Sporanox 200 mg. In asthmatics, PUR1900 geometric mean maximum sputum concentrations were 70-fold higher and geometric mean plasma concentrations were 66-fold lower than with oral Sporanox.

CONCLUSION

PUR1900 was safe and well-tolerated under the study conditions. Compared to oral dosing, PUR1900 achieved higher lung and lower plasma exposure. The pharmacokinetic profile of PUR1900 suggests the potential to improve upon the efficacy and safety profile observed with oral itraconazole.

Choosing the Right Antifungal Agent in ICU Patients

Fungi are responsible for around 20% of microbiologically documented infections in intensive care units (ICU). In the last decade, the incidence of invasive fungal infections (IFI), including candidemia, has increased steadily because of increased numbers of both immunocompromised and ICU patients. To improve the outcomes of patients with IFI, intensivists need to be aware of the inherent challenges. This narrative review summarizes the features of routinely used treatments directed against IFI in non-neutropenic ICU patients, which include three classes of antifungals: polyenes, azoles, and echinocandins. ICU patients’ pathophysiological changes are responsible for deep changes in the pharmacokinetics of antifungals. Moreover, drug interactions affect the response to antifungal treatments. Consequently, appropriate antifungal dosage is a challenge under these special conditions. Dosages should be based on renal and liver function, and serum concentrations should be monitored. This review summarizes recent guidelines, focusing on bedside management.

Drug interactions between tacrolimus and clotrimazole troche: a data mining approach followed by a pharmacokinetic study

PURPOSE

This study investigated the effects of clotrimazole troche on the risk of transplant rejection and the pharmacokinetics of tacrolimus.

METHODS

The data mining approach was used to investigate whether the use of clotrimazole increased the risk of transplant rejection in patients receiving tacrolimus therapy. Patient data were acquired from the US Food and Drug Administration's Adverse Event Reporting System (FAERS) from the first quarter of 2004 to the end of 2017. Next, we retrospectively investigated the effect of clotrimazole troche on tacrolimus pharmacokinetics in seven patients who underwent heart transplantation between March and December 2017.

RESULTS

The FAERS subset data indicated a significant association between transplant rejection and tacrolimus with clotrimazole [reporting odds ratio 1.92, 95% two-sided confidence interval (95% CI) 1.43-2.58, information component 0.81, 95% CI 0.40-1.23]. The pharmacokinetic study demonstrated a significant correlation between trough concentration (C₀) and area under the concentration-time curve of tacrolimus after discontinuation of clotrimazole (R² = 0.60, P < 0.05) but not before its discontinuation. Furthermore, the median clearance/bioavailability of tacrolimus after discontinuation of clotrimazole was 2.2-fold greater than that before its discontinuation (0.27 vs. 0.59 L/h/kg, P < 0.05). The median C₀ decreased from 10.7 ng/mL on the day after discontinuation of clotrimazole to 6.5 ng/mL at 1 day and 5.3 ng/mL at 2 days after its discontinuation.

CONCLUSION

Immediate dose adjustments of tacrolimus may be beneficial to avoid transplant rejection when clotrimazole troche is added or discontinued.

Novel insights into the complex pharmacokinetics of voriconazole: a review of its metabolism

Voriconazole, a second-generation triazole frequently used for the prophylaxis and treatment of invasive fungal infections, undergoes complex metabolism mainly involving various (polymorphic) cytochrome P450 enzymes in humans. Although high inter- and intraindividual variability in voriconazole pharmacokinetics have been observed and the therapeutic range for this compound is relatively narrow, the metabolism of voriconazole has not been fully elucidated yet. The available literature data investigating the multiple different pathways and metabolites are extremely unbalanced and thus the absolute or relative contribution of the different pathways and enzymes involved in the metabolism of voriconazole remains uncertain. Furthermore, other factors such as nonlinear pharmacokinetics caused by auto-inhibition or -induction and polymorphisms of the metabolizing enzymes hinder safe and effective voriconazole dosing in clinical practice and have not yet been studied sufficiently. This review aimed at amalgamating the available literature on the pharmacokinetics of voriconazole in vitro and in vivo, with a special focus on metabolism in adults and children, in order to congregate an overall landscape of the current body of knowledge and identify knowledge gaps, opening the way towards further research in order to foster the understanding, towards better therapeutic dosing decisions.

ESCMID-ECMM guideline: diagnosis and management of invasive aspergillosis in neonates and children

SCOPE

Presenting symptoms, distributions and patterns of diseases and vulnerability to invasive aspergillosis (IA) are similar between children and adults. However, differences exist in the epidemiology and underlying conditions, the usefulness of newer diagnostic tools, the pharmacology of antifungal agents and in the evidence from interventional phase 3 clinical trials. Therefore, the European Society for Clinical Microbiology and Infectious Diseases (ESCMID) and the European Confederation of Medical Mycology (ECMM) have developed a paediatric-specific guideline for the diagnosis and management of IA in neonates and children.

METHODS

Review and discussion of the scientific literature and grading of the available quality of evidence was performed by the paediatric subgroup of the ESCMID-ECMM-European Respiratory Society (ERS) Aspergillus disease guideline working group, which was assigned the mandate for the development of neonatal- and paediatric-specific recommendations.

QUESTIONS

Questions addressed by the guideline included the epidemiology of IA in neonates and children; which paediatric patients may benefit from antifungal prophylaxis; how to diagnose IA in neonates and children; which antifungal agents are available for use in neonates and children; which antifungal agents are suitable for prophylaxis and treatment of IA in neonates and children; what is the role of therapeutic drug monitoring of azole antifungals; and which management strategies are suitable to be used in paediatric patients. This guideline provides recommendations for the diagnosis, prevention and treatment of IA in the paediatric population, including neonates. The aim of this guideline is to facilitate optimal management of neonates and children at risk for or diagnosed with IA.

Pulmonary infectious complications after hematopoietic stem cell transplantation: a practical guide to clinicians

PURPOSE OF REVIEW

The current review highlights the most relevant articles on lung infections following hematopoietic stem cell transplantation (HCT) published over the last year. Between 30 and 50% of HCT recipients will develop pulmonary infiltrates. These pulmonary complications may be infectious (caused by virus, bacteria, fungi, or protozoa) or noninfectious (e.g., fluid overload, heart failure, transfusion reactions like transfusion associated lung injury and transfusion-associated circulatory overload, drug reactions, engraftment syndrome, idiopathic pneumonia syndrome, diffuse alveolar hemorrhage, cryptogenic organizing pneumonia, and bronchiolitis obliterans syndrome).

RECENT FINDINGS

New data on the yield of bronchoscopy and bronchoalveolar lavage (BAL), the prevalence and clinical manifestations of respiratory viruses and the usefulness of molecular techniques for diagnosis have been published. In addition, guidelines or meta-analyses on the management of neutropenic fever, serological diagnosis of fungal infections and diagnosis and management of Pneumocystis and aspergillosis have been published.

SUMMARY

Respiratory viruses are important pathogens after HCT. PCR in the BAL is becoming the diagnostic modality of choice for a variety of infections. The best approach for the empirical management of pulmonary infiltrates following HCT remains to be defined.

Interactions between anti-infective agents and immunosuppressants-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation provide an update on potential drug-drug interactions between anti-infectives and immunosuppressants, which are most notable with calcineurin and mTOR inhibitors. Drug-drug interactions may occur through pharmacokinetic mechanisms leading to altered drug concentrations of either the anti-infective or immunosuppressive drug, or by pharmacodynamic interactions increasing or decreasing the efficacy or toxicity of the medications. Many of the significant pharmacokinetic interactions occur through inhibition or induction of the cytochrome 3A4 system by anti-infective agents leading to increased or decreased immunosuppressive agent levels, respectively. The membrane transporter P-glycoprotein is also often involved in drug interactions. Since the last iteration of these guidelines, multiple new hepatitis C virus direct-acting antivirals have become available for use in SOT recipients. Of these agents, some are substrates of cytochrome and drug transporter systems, while others inhibit these systems and may affect immunosuppressive agents. Due to the high risk for drug-drug interactions in the solid organ transplant population, practitioners must be aware of potential interactions and be vigilant in monitoring and adjusting drug dosing when appropriate.

The Influence of Proinflammatory Cytokines on Voriconazole Trough Concentration in Patients With Different Forms of Hematologic Disorders

Even though multiple factors are involved in the high fluctuation of voriconazole (VCZ) plasma concentration, little is known regarding the influence of proinflammatory cytokines on VCZ concentration. The aim of this study was to investigate the influence of proinflammatory cytokines, namely, interleukin (IL)-1β, IL-6, IL-18, interferon-γ, tumor necrosis factor-α, and transforming growth factor (TGF)-β1 on VCZ trough concentration (VCZ-C_min ) in Chinese patients with different forms of hematologic disorders. A total of 250 plasma samples from 113 patients were analyzed for VCZ-C_min and proinflammatory cytokines using a validated liquid chromatography-tandem mass spectrometry and enzyme-linked immunosorbent assay methods, respectively. Patient demographics and clinical characteristics were obtained from hospital records. VCZ-C_min was significantly correlated with IL-18 in acute myeloid leukemia (r = 0.456; P ˂ .0001), acute lymphoblastic leukemia (r = 0.317; P = .019), and chronic myeloid leukemia (r = 0.737; P = .004) while VCZ-C_min and TGF-β1 were correlated (r = 0.436; P ˂ .001) in acute myeloid leukemia patients only. VCZ-C_min at different concentration range showed significant inhibitory effect of IL-6. A backward multiple linear regression model revealed patient age (coefficient [β] = 0.025; P = .04), gamma-glutamyl transferase (β = 0.003; P = .023), IL-6 (β = -0.001; P = .024), proton pump inhibitor coadministration (β = 1.518; P = .002), and cytochrome P450 (CYP) 2C19 polymorphism as predictors of VCZ-C_min ; however, these factors explained only 29% of VCZ-C_min variation. In conclusion, IL-18 and TGF-β1 have correlation with VCZ-C_min in Chinese patients with leukemia. Apparently, VCZ may have an inhibitory effect on IL-6 levels. Furthermore, patient age, gamma-glutamyl transferase, IL-6, PPI coadministration, and cytochrome P450 2C19 polymormorphism partially predicted the VCZ-C_min . Therapeutic drug monitoring of VCZ in Chinese patients is highly encouraged.

The impact of azole antifungal drugs on imatinib metabolism in human liver microsomes

1. Imatinib is widely used for the treatment of hematologic malignancies. It is common that imatinib is clinically co-prescribed with azole antifungal agents since these patients are more prone to invasive antifungal infection. The present study was to investigate the effects of azole antifungal drugs, including ketoconazole, fluconazole, voriconazole, itraconazole and posaconazole on imatinib metabolism. 2. The main metabolites, 1-OH midazolam and N-desmethyl imatinib, were determined in the absence and in the presence of various levels of ketoconazole, fluconazole, voriconazole, itraconazole and posaconazole. The relevant assay was also performed to screen mechanism-based inhibitors (MBI). 3.   The inhibition ability of 1-OH midazolam formation from midazolam based on IC₅₀ values was ketoconazole (0.09 µM)>itraconazole (0.31 µM)> posaconazole (0.68 µM)>voriconazole (2.10 µM) > fluconazole (8.90 µM). Similarly, the rank order of inhibitory effects on formation of N-desmethyl imatinib from imatinib was ketoconazole (4.58 µM)>itraconazole (17.45 µM)> posaconazole (31.02 µM)> voriconazole (367.9 µM) >fluconazole (1.11 mM). Posaconazole and itraconazole displayed evidence of MBI. Additionally, imatinib was also shown as a MBI of CYP3A with IC₅₀ value of 5.40 µM against the midazolam. 4. The significant difference in IC₅₀ values of midazolam and imatinib inhibited by azole antifungal agents was observed. The role of CYP2C8 in imatinib metabolism and imatinib autoinhibits CYP3A activity may explain this difference. Our findings suggest that the azole antifungal agents might have limited impacts on imatinib exposure by CYP3A activity.

[Invasive aspergillosis in solid organ transplantation]

Solid organ transplant (SOT) recipients have a high risk for developing invasive fungal infections (IFI). Treatment is difficult due to the interaction between the antifungal and immunosuppressant drugs, as well as the risk of hepatotoxicity and kidney failure associated with voriconazole and amphotericinB, respectively. Isavuconazole is a new antifungal triazole agent with excellent oral bioavailability, predictable and linear pharmacokinetics, good tolerance and low adverse effects. It has been approved for the treatment of invasive aspergillosis and mucormycosis. A review is presented of the reported experience in the use of isavuconazole in SOT. According to the published studies, isavuconazole has a significantly lower risk of interaction with tacrolimus, and is less hepatotoxic than voriconazole. Nevertheless, there is a significant variability between patients, and between each type of SOT. Isavuconazole reduces the side effects associated with the treatment of IFI in SOT. It would be of great interest the implementation of future clinical trials with isavuconazole for the treatment and/or prophylaxis of IFI in these patients.

[Current therapeutic options in invasive mycosis and potential therapeutic role of isavuconazole]

The treatment of invasive fungal infections has deeply evolved in recent years with the inclusion of new antifungals to the therapeutic treatment arsenal. A new azole, isavuconazole, has been recently approved. This review focuses on the role of isavuconazole for treating the most important invasive fungal infections: invasive candidiasis, aspergillosis, mucormicosis, infections caused by other filamentous fungi and those caused by dimorphic fungi.

Population pharmacokinetics of voriconazole and CYP2C19 polymorphisms for optimizing dosing regimens in renal transplant recipients

AIMS

The aims of the present study were to characterize the pharmacokinetics of voriconazole in renal transplant recipients and to identify factors significantly affecting pharmacokinetic parameters. We also aimed to explore the optimal dosing regimens for patients who developed invasive fungal infections.

METHODS

A total of 105 patients (342 concentrations) were included prospectively in a population pharmacokinetic analysis. Nonlinear mixed-effects models were developed using Phoenix NLME software. Dosing simulations were performed based on the final model.

RESULTS

A one-compartment model with first-order absorption and elimination was used to characterize voriconazole pharmacokinetics. Population estimates of clearance, volume of distribution and oral bioavailability were 2.88 l·h-1 , 169.3 l and 58%, respectively. The allele frequencies of cytochrome P450 gene (CYP) 2C19*2, *3 and *17 variants were 29.2%, 5.2% and 0.5%, respectively. CYP2C19 genotype had a significant effect on the clearance. Voriconazole trough concentrations in poor metabolizers were significantly higher than in intermediate metabolizers and extensive metabolizers alike. The volume of distribution increased with increased body weight. The oral bioavailability was substantially lower within 1 month after transplantation but increased with postoperative time. Dosing simulations indicated that during the early postoperative period, poor metabolizers could be treated with 150 mg intravenously or 250 mg orally twice daily; intermediate metabolizers with 200 mg intravenously or 350 mg orally twice daily; and extensive metabolizers with 300 mg intravenously twice daily.

CONCLUSIONS

Using a combination of CYP2C19 genotype and postoperative time to determine the initial voriconazole dosing regimens followed by therapeutic drug monitoring could help to advance individualized treatment in renal transplantation patients with invasive fungal infections.

Clinical Pharmacokinetics and Drug-Drug Interaction Potential for Coadministered SCY-078, an Oral Fungicidal Glucan Synthase Inhibitor, and Tacrolimus

SCY-078 is an orally bioavailable triterpenoid glucan synthase inhibitor in clinical development as an intravenous and oral treatment of fungal infections caused by Candida and Aspergillus species. This was a sequential, single-center, open-label phase 1 study to assess the drug-drug interaction potential between SCY-078 and tacrolimus during concomitant administration in healthy subjects. In cohort 1, period 1, subjects received a single oral dose of tacrolimus 2 mg in the fasted state. In period 2 after a ≥15 day washout, subjects received a single loading dose of SCY-078 1250 mg on day 1 followed by maintenance doses of SCY-780 750 mg on days 2 through 8. On day 3 of period 2, subjects also received a single dose of tacrolimus 2 mg concurrent with SCY-078. In cohort 2, subjects received a loading dose of SCY-078 1250 mg on day 1 followed by maintenance doses of SCY-780 750 mg on days 2 and 3. Pharmacokinetic (PK) parameters were compared to assess both the impact of steady-state SCY-078 on tacrolimus and the impact of tacrolimus on the PK of steady-state SCY-078. The concurrent coadministration of tacrolimus and SCY-078 had no effect on the maximum blood levels of tacrolimus, as evidenced by no change in maximum concentration of drug in blood plasma and a 1.4-fold increase in total area under the plasma drug concentration-time curve. The concurrent coadministration of tacrolimus and SCY-078 resulted in a weaker interaction than typically observed with the azole class of antifungals. The current data indicate that an initial dose adjustment for tacrolimus may not be warranted when combined with SCY-078, as the modest increase in exposure is less than the therapeutic window, although tacrolimus monitoring, as with addition of any new medication, is recommended. These results support the coadministration of SCY-078 and tacrolimus.

Recent advances in understanding and managing infectious diseases in solid organ transplant recipients

Background: Undergoing solid organ transplantation (SOT) exposes the recipient to various infectious risks, including possible transmission of pathogen by the transplanted organ, post-surgical infections, reactivation of latent pathogens, or novel infections. Recent advances: In the last few years, the emergence of Zika virus has raised concerns in the transplant community. Few cases have been described in SOT patients, and these were associated mainly with moderate disease and favorable outcome; the notable exception is a recent case of fatal meningo-encephalopathy in a heart transplant recipient. Because of the advances in treating hepatitis C, several teams recently started to use organs from hepatitis C-positive donors. The worldwide increasing incidence of multidrug-resistant pathogens, as well as the increasing incidence of Clostridioidesdifficile infection, is of particular concern in SOT patients. In the field of mycology, the main recent therapeutic advance is the availability of isavuconazole for the treatment of invasive aspergillosis and mucormycosis. This drug has the advantage of minimal interaction with calcineurin inhibitors. Regarding the viral reactivations occurring after transplant, cytomegalovirus (CMV) infection is still a significant issue in SOT patients. The management of resistant CMV remains particularly difficult. The approval of letermovir, albeit in bone marrow transplantation, and the therapeutic trial of maribavir bring a ray of hope. Another advancement in management of post-transplant infections is the development of in vitro tests evaluating pathogen-specific immune response, such as immunodiagnostics for CMV and, more recently, tests for monitoring immunity against BK virus. Conclusion: The increasing number of organ transplantations, the use of newer immunosuppressive drugs, and high-risk donors continue to define the landscape of transplant infectious diseases in the current era.

Development of on-line monolith-based in-tube solid phase microextraction for the sensitive determination of triazoles in environmental waters

In this work, a convenient and sensitive method for the determination of triazoles in environmental waters was developed by on-line combining in-tube solid phase microextraction (IT-SPME) and high performance liquid chromatography with diode array detector (HPLC-DAD). To extract triazoles effectively, poly (4-vinyl pyridine-co-ethylene dimethacrylate) monolith was in-situ fabricated and utilized as the extraction phase of IT-SPME. A series of key extraction parameters including desorption solvent, sample volume, adsorption and desorption flow rate, pH value and ionic strength in sample matrix were optimized thoroughly. Under the most favorable conditions (volume of sample, 6.0 mL; adsorption flow rate, 0.2 mL/min; desorption solvent, 80.0 µL mixture of ACN/water (70/30, v/v); desorption flow rate, 50.0 µL/min; sample pH value, 8.0; ionic strength did not be adjusted), the developed monolith-based IT-SPME could extract target analytes effectively and expected analytical merits were achieved. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were in the ranges of 0.014-0.031 µg/L and 0.11-0.074 µg/L, respectively. Satisfactory method reproducibility was obtained by intra-day and inter-day precisions, with relative standard deviations (RSDs) lower than 10%. The optimized IT-SPME-HPLC-DAD method was then applied to detect triadimenol, triazolone and hexaconazole in water samples including lake, river and sewage waters. The spiked recoveries were 78.9-106% and the RSDs were in the range of 0.2-7.2%. The results well evidence that the proposed method is convenient, accurate, sensitive, practical and environmentally friendly for the determination of triazoles in environmental waters.

Issues in the management of invasive pulmonary aspergillosis in non-neutropenic patients in the intensive care unit: A role for isavuconazole

Background

Almost half of all cases of invasive aspergillosis (IA) occur in the intensive care unit (ICU), with mortality rates of 70–80% for probable or proven cases. IA has become a major concern among non-neutropenic patients in the ICU with chronic obstructive pulmonary disease (COPD) but although prompt, appropriate antifungal therapy is crucial, diagnosis in this situation is challenging. Criteria for a probable diagnosis in critically ill patients have been proposed to help to expedite therapy.

Methods

A case of probable invasive pulmonary aspergillosis (IPA) in a non-neutropenic patient admitted to the ICU was used to illustrate potential issues in the diagnostic work-up and management of patients in this setting.

Results

A non-neutropenic 69-year-old man with COPD receiving clomipramine was diagnosed in the ICU with probable invasive aspergillosis based on the presence of severe chronic obstructive pulmonary disease, suspected X-linked granulomatous disease, nodular infiltrates and galactogamman positivity on bronchoalveolar lavage (BAL) fluid. Voriconazole was unsuitable due to the patient's prolonged QT interval and risk of a drug–drug interaction with clomipramine. Isavuconazole was initiated and the patient's condition improved. The three-month course of isavuconazole treatment was well-tolerated and resulted in compete recovery of the patient.

Conclusions

Voriconazole is a standard first-line treatment for IA but intravenous therapy is associated with toxicity and the potential for drug–drug interactions. Isavuconazole is another first-line therapy which was effective and safe in the management of this critically ill non-neutropenic patient with baseline QT prolongation and potential drug–drug interactions with voriconazole.