Economic evaluation of azoles as primary prophylaxis for the prevention of invasive fungal infections in Spanish patients undergoing allogeneic haematopoietic stem cell transplant

Antifungal Prophylaxis After Lung Transplantation: Where Are We Now?

BACKGROUND

Lung transplantation is an important treatment option for various end-stage lung diseases. However, survival remains limited due to graft rejection and infections. Despite that fungal infections are frequent and carry a bad prognosis, there is currently no consensus on efficacy, optimal drug, route, or duration of antifungal prophylaxis. This narrative review summarizes current strategies for antifungal prophylaxis after lung transplantation.

METHODS

English language articles in Embase, Pubmed, UptoDate, and bibliographies were used to assess the efficacy and safety of available antifungal agents for prophylaxis in adult lung transplant recipients.

RESULTS

Overall, there are limited high-quality data. Universal prophylaxis is more widely used and may be preferable over targeted prophylaxis. Both formulations of inhaled amphotericin B and systemic azoles are effective at reducing fungal infection rates, yet with their own specific advantages and disadvantages. The benefit of combination regimens has yet to be proven. Considering the post-transplant timing of the onset of fungal infections, postoperative prophylaxis during the first postoperative months seems indicated for most patients.

CONCLUSIONS

Based on existing literature, universal antifungal prophylaxis with inhaled amphotericin B and systemic voriconazole for at least 3-6 mo after lung transplantation may be advisable, with a slight preference for amphotericin B because of its better safety profile.

Experience of a Strategy Including CYP2C19 Preemptive Genotyping Followed by Therapeutic Drug Monitoring of Voriconazole in Patients Undergoing Allogenic Hematopoietic Stem Cell Transplantation

Many factors have been described to contribute to voriconazole (VCZ) interpatient variability in plasma concentrations, especially CYP2C19 genetic variability. In 2014, Hicks et al. presented data describing the correlation between VCZ plasma concentrations and CYP2C19 diplotypes in immunocompromised pediatric patients and utilized pharmacokinetic modeling to extrapolate a more suitable VCZ dose for each CYP2C19 diplotype. In 2017, in our hospital, a clinical protocol was developed for individualization of VCZ in immunocompromised patients based on preemptive genotyping of CYP2C19 and dosing proposed by Hicks et al., Clinical Pharmacogenetics Implementation Consortium (CPIC) clinical guidelines, and routine therapeutic drug monitoring (TDM). We made a retrospective review of a cohort of 28 immunocompromised pediatric patients receiving VCZ according to our protocol. CYP2C19 gene molecular analysis was preemptively performed using PharmArray^®. Plasma trough concentrations were measured by immunoassay analysis until target concentrations (1–5.5 μg/ml) were reached. Sixteen patients (57.14%) achieved VCZ trough target concentrations in the first measure after the initial dose based on PGx. This figure is similar to estimations made by Hicks et al. in their simulation (60%). Subdividing by phenotype, our genotyping and TDM-combined strategy allow us to achieve target concentrations during treatment/prophylaxis in 90% of the CYP2C19 Normal Metabolizers (NM)/Intermediate Metabolizers (IM) and 100% of the Rapid Metabolizers (RM) and Ultrarapid Metabolizers (UM) of our cohort. We recommended modifications of the initial dose in 29% (n = 8) of the patients. In RM ≥12 years old, an increase of the initial dose resulted in 50% of these patients achieving target concentrations in the first measure after initial dose adjustment based only on PGx information. Our experience highlights the need to improve VCZ dose predictions in children and the potential of preemptive genotyping and TDM to this aim. We are conducting a multicenter, randomized clinical trial in patients with risk of aspergillosis in order to evaluate the effectiveness and efficiency of VCZ individualization: VORIGENIPHARM (EudraCT: 2019-000376-41).

Drug-drug interaction study of imatinib and voriconazole in vitro and in vivo

Background: In clinical practice, common problem polypharmacy could result in the increased risks of drug-drug interactions (DDIs). Co-administered imatinib (IMA) and voriconazole (VOR) as one treatment protocol in cancer patients with fungal infections are common.Purpose: The aim of the present study was to assess the potential DDIs associated with the concurrent use of IMA and VOR in rat liver microsomes (RLMs) and in rats.Methods and results: The concentration levels of IMA, VOR, and their metabolites N-desmethyl IMA (CGP74588) and N-oxide voriconazole (N-oxide VOR) were determined by ultra performance liquid chromatography-tandem mass spectrometry. In vitro study of RLMs, VOR inhibited the IMA metabolism with the half-maximal inhibitory concentration (IC₅₀) of 105.20 μM, while IC₅₀ for IMA against VOR was 61.30 μM. After co-administered IMA and VOR in rats, the C _max of IMA was increased significantly, while the AUC_0→t, AUC_0→∞, and C _max of CGP74588 were decreased significantly. In addition, similar results were also found that the main pharmacokinetic parameters (AUC_0→t, AUC_0→∞, MRT_0→∞, T _max, and C _max) of VOR were increased significantly, while the AUC_0→t, AUC_0→∞, and C _max of N-oxide VOR were decreased significantly. Incorporation of all the results indicated that both drugs had a inhibitory effect on each other's metabolism in vitro and in vivo.Conclusion: Thus, it is of great value to monitor the concomitant use of IMA and VOR in the clinic to reduce the risks of unexpected clinical outcomes.

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.

Cost-effectiveness analysis of voriconazole, fluconazole, and amphotericin B for invasive fungal infections following allogeneic hematopoietic stem cell transplantation in Mexico

Background

Patients receiving allogeneic hematopoietic stem cell transplantation (alloHSCT) are at high risk of invasive fungal infections (IFIs), which are associated with high mortality and economic burden. The cost-effectiveness of prophylaxis for the prevention of IFIs in alloHSCT recipients in Mexico has not yet been assessed.

Methods

This analysis modeled a hypothetical cohort of 1,000 patients to estimate costs and outcomes for patients receiving prophylaxis for IFIs following alloHSCT, from the perspective of institutional payers in Mexico. The main prophylaxis agents currently used in Mexican clinical practice are voriconazole, fluconazole, and amphotericin B (AmB). The model accounted for event rates of IFIs during each treatment, assuming IFI causality due to invasive aspergillosis, invasive candidiasis, or other IFIs, and that the outcome for patients during follow-up was IFI-related death, death from other causes, or survival. Clinical efficacies were obtained from published literature; costs were based on local sources. Cost-effectiveness was assessed using incremental cost-effectiveness ratios (ICERs). Univariate (assessing the impact of varying each model parameter) and probabilistic sensitivity analyses were performed.

Results

Voriconazole was associated with the lowest number of breakthrough IFIs, IFI-related deaths, and total number of deaths. Total costs were lower for fluconazole (Mexican pesos [MXN] 72,944; US $4,079) than voriconazole (MXN 101,413; US $5,671) or AmB (MXN 110,529; US $6,180). Voriconazole had better clinical outcomes and lower costs than AmB and could be considered cost-effective compared with fluconazole in line with the local ICER threshold. Drug costs, monitoring costs, and duration of prophylaxis were most sensitive to variation from univariate sensitivity analysis. Findings from the probabilistic sensitivity analysis were consistent with the base-case results.

Conclusion

Voriconazole had the most favorable clinical outcomes, but overall prophylaxis costs were higher than with fluconazole. Overall, based on local ICER thresholds (MXN 184,665; US $10,326), voriconazole was considered a cost-effective option for prophylaxis of IFI in Mexico.

Voriconazole for prophylaxis of invasive fungal infections after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Invasive fungal infections (IFIs) following allogeneic hematopoietic stem cell transplantation (alloHSCT) are associated with a high mortality, and accordingly most alloHSCT recipients receive prophylaxis with antifungal agents. Despite some improvement in outcomes of IFIs over time, they continue to represent substantial clinical risk, mortality, and financial burden. Areas covered: We review the main pathogens responsible for IFIs in recipients of alloHSCT, current treatment recommendations, and discuss clinical and economic considerations associated with voriconazole prophylaxis of IFIs in these patients. Expert commentary: The clinical efficacy of voriconazole appears to be at least equivalent to other antifungal treatments, and generally well tolerated. Overall, benefit-risk balance is favorable, and findings from cost-effectiveness analyses support the use of voriconazole prophylaxis of IFIs in recipients of alloHSCT.