Therapeutic drug monitoring of posaconazole in patients with acute myeloid leukemia or myelodysplastic syndrome

A Prospective Study to Evaluate the Effect of Therapeutic Drug Monitoring-Based Posaconazole Prophylaxis on Invasive Fungal Infection Rate During Acute Myeloid Leukemia Induction Therapy

Invasive fungal infections (IFIs) are a significant cause of morbidity and mortality in de-novo acute myeloid leukemia patients receiving induction chemotherapy. Despite using posaconazole, a broad-spectrum antifungal, for IFI prophylaxis, the breakthrough IFI rate is high in the real-world setting. One of the reasons could be frequent suboptimal plasma posaconazole levels. In the present study, we evaluated if therapeutic drug monitoring (TDM) guided posaconazole prophylaxis can reduce the IFI rates in comparison to a historical cohort. We enrolled 90 patients, > / = 16 years of age, without baseline IFIs, planned for remission induction therapy. All patients were started on posaconazole suspension 200 mg TDS and the dose was increased in a stepwise manner if trough levels were found to be suboptimal (< 350 ng/ml for day 2 or < 700 ng/ml subsequently). The TDM based approach resulted in a significant decline in breakthrough IFI rates (18% versus 52%, P < 0.0001) A total of 69 patients (78%) required dose escalation. Thirty-one patients required change in antifungals due to either suboptimal levels, persistent fever, diarrhoea or vomiting. We could not demonstrate an exposure-response relationship but the difference in IFI rates in patients with a median posaconazole level > / = 700 ng/ml (0%) and < 700 ng/ml (21.6%) was clinically meaningful. Posaconazole levels were found to be significantly lower in patients on antacids and prokinetics. The incidence of posaconazole-related grade 3 toxicity was low (2.3%). Thus TDM-based dosing of posaconazole helps reduce breakthrough IFI rate and should be a part of posaconazole prophylaxis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-023-01709-3.

Posaconazole trough concentrations are not influenced by inflammation: A prospective study

During inflammation, several cytochrome P450 enzymes are downregulated. Recently it was shown that voriconazole metabolism is reduced during inflammation. Posaconazole, another triazole with broad-spectrum antifungal activity, is metabolised only to a limited extent by cytochrome P450 enzymes and to a wider extent by phase 2 enzyme systems. The aim of this study was to investigate posaconazole concentrations during inflammation. Patients aged ≥18 years receiving posaconazole prophylaxis or treatment for fungal infections were enrolled in a prospective observational study. Samples for posaconazole and C-reactive protein (CRP) concentrations were collected routinely for each patient. Longitudinal data analysis was performed to analyse the correlation between posaconazole serum trough concentrations and CRP values, corrected for potential factors that could influence the posaconazole concentration. Between August 2015 and June 2017, 64 patients were recruited to this study. Data for 55 patients (511 posaconazole samples) were included in the final analysis. The overall median posaconazole concentration was 1.8 mg/L [interquartile range (IQR) 1-2.9 mg/L, range 0.1-7.94 mg/L] and the overall median CRP concentration was 23.5 mg/L (IQR 5-75 mg/L, range 0-457 mg/L). Longitudinal data analysis showed that only the posaconazole daily dose (in mg/kg body weight) had a significant influence on posaconazole concentration after correction for other factors (P < 0.0001). Posaconazole concentrations were not influenced by CRP concentrations (P = 0.77). Posaconazole concentrations are not influenced by inflammation, reflected by CRP concentration. Therefore, more frequent therapeutic drug monitoring of posaconazole during inflammation or after an infection subsides is not necessary.

Posaconazole Therapeutic Drug Monitoring in a Regional Hospital Setting

BACKGROUND

Posaconazole therapeutic drug monitoring (TDM) is recommended to promote effective antifungal prophylaxis, but its utility has yet to be optimized. Breakthrough invasive fungal infections have been reported with serum concentrations <700 mcg/L, but there is little evidence to determine the optimal serum concentration for efficacy or concentrations associated with toxicity. Challenges for effective monitoring are greater in settings without posaconazole TDM facilities because of the long turnaround time before receipt of results.

METHODS

Thirty-eight TDM episodes were performed on 18 patients in a regional center in Australia during a 30-month period. Australian guidelines recommend a trough serum concentration of ≥700 mcg/L. The response to concentrations below the recommendation threshold (700 mcg/L), the final serum plasma concentration for each patient, and the appropriateness of TDM were evaluated.

RESULTS

A total of 19 (50%) concentrations were recorded to be < 700 mcg/L. Of these 19 concentrations, the drug dose was increased on only 4 occasions. Eleven of 18 patients (61%) had initial concentrations <700 mcg/L, with only 3 (27%) among those achieving final concentration ≥ 700 mcg/L; 5 patients with initial concentrations <700 mcg/L did not have any further TDM testing. Nine of the 18 (50%) patients had a final concentration <700 mcg/L. Five of 7 (71%) patients with initial concentrations ≥700 mcg/L had further TDM with no reasoning documented.

CONCLUSIONS

The results demonstrate a lack of confidence and consistency in ordering, interpreting, and following up posaconazole concentrations. Therefore, the use of TDM should be carefully considered, especially in regional centers. Such settings should consider the practicalities of posaconazole TDM and try to improve the process to ensure consistency and optimization of patient care.

Evaluation of Posaconazole Pharmacokinetics in Adult Patients with Invasive Fungal Infection

Mortality and morbidity due to invasive fungal infections have increased over the years. Posaconazole is a second-generation triazole agent with an extended spectrum of activity, which shows a high interindividual variability in its plasma levels, rendering dosing in many patients inconsistent or inadequate. Hence, posaconazole therapeutic drug monitoring, which is easily available in clinical practice, may improve treatment success and safety. The aim of the study was to describe posaconazole pharmacokinetics, and to evaluate the utility of therapeutic drug monitoring for therapy and prophylaxis in a cohort of adult patients. A fully validated chromatographic method was used to quantify posaconazole concentration in plasma collected from adult patients at the end of the dosing interval. Associations between variables were tested using the Pearson test. The Mann-Whitney test was used to probe the influence of categorical variables on continuous ones. A high inter-individual variability was shown. Of the 172 enrolled patients, among those receiving the drug by the oral route (N = 170), gender significantly influenced drug exposure: males showed greater posaconazole concentration than females (p = 0.028). This study highlights the importance of therapeutic drug monitoring in those with invasive fungal infections and its significant clinical implications; moreover we propose, for the first time, the possible influence of gender on posaconazole exposure.

Subtherapeutic Posaconazole Exposure and Treatment Outcome in Patients With Invasive Fungal Disease

BACKGROUND

Posaconazole exposure seems to be subtherapeutic in some patients with invasive fungal disease. Due to the pharmacokinetic variability of posaconazole, therapeutic drug monitoring may help to optimize the efficacy of this antifungal drug.

METHODS

A retrospective study of patients treated with posaconazole from January 2008 to April 2014 and for whom posaconazole serum concentrations were available was conducted. Risk factors for underexposure of posaconazole were detected, and the relationship between posaconazole exposure and treatment outcome according to the European Organization for Research and Treatment of Cancer (EORTC) criteria was assessed.

RESULTS

Seventy patients met the inclusion criteria, 45 patients received posaconazole as treatment, and 25 patients received posaconazole as a prophylactic. Posaconazole serum trough concentrations were <1.25 mg/L in 44.4% of patients receiving treatment and <0.7 mg/L in 40.0% of patients receiving prophylactic posaconazole. Multiple linear regression analysis showed a significant, independent, and negative association of the posaconazole serum trough concentration with a lack of enteral nutrition (P < 0.001), vomiting (P = 0.035), the use of a proton pump inhibitor or H2-receptor antagonist (P < 0.001), a liquid diet (P = 0.002), concomitant chemotherapy (P = 0.004), and a posaconazole dose frequency of 2 times daily (P = 0.015). A higher posaconazole concentration was associated with a better treatment outcome [odds ratio = 22.22 (95% confidence interval, 3.40-145.33); P = 0.001].

CONCLUSIONS

Posaconazole exposure is insufficient in more than 40% of patients at risk of or with invasive fungal disease, and posaconazole exposure is positively correlated with a successful treatment outcome. Therapeutic drug monitoring of posaconazole can detect underexposure and can be helpful in treatment optimization.

Posaconazole Plasma Concentrations on Days Three to Five Predict Steady-State Levels

Low posaconazole plasma concentrations (PPCs) have been associated with breakthrough invasive fungal infections. We assessed the correlation between pre-steady-state PPCs (obtained between days 3 and 5) and PPCs obtained during steady state in 48 patients with underlying hematological malignancies receiving posaconazole oral-solution prophylaxis. Pre-steady-state PPCs correlated significantly with PPCs obtained at steady state (Spearman r = 0.754; P < 0.001). Receiver operating characteristic (ROC) curve analysis of pre-steady-state PPCs revealed an area under the curve (AUC) of 0.884 (95% confidence interval [CI], 0.790 to 0.977) for predicting satisfactory PPCs at steady state.

Posaconazole: An Update of Its Clinical Use

Posaconazole (PCZ) is a relatively new addition to the azole antifungals. It has fungicidal activities against Aspergillus fumigatus, Blastomyces dermatitidis, selected Candida species, Crytopcoccus neoformans, and Trichosporon. PCZ also has fungistatic activities against Candida, Coccidioides, selected Fusarium spp., Histoplasma, Scedosporium and Zygomycetes. In addition, combining the drug with caspofungin or amphotericin B results in a synergistic interaction against A. fumigatus, C. glabrata and C. neoformans. The absorption of PCZ suspension is enhanced when given with food, nutritional supplements, and carbonated beverages. Oral administration of PCZ in divided doses also increases its bioavailability. PCZ has a large volume of distribution and is highly protein bound (>95%). The main elimination route of PCZ is fecal. PCZ is an inhibitor of the CYP3A4 enzyme; therefore, monitoring for drug-drug interactions is warranted with other CYP3A4 substrates/inhibitors/inducers. The most common adverse effects include headache, fatigue, nausea, vomiting and elevated hepatic enzymes. PCZ, with its unique antifungal activities, expands the azole class of antifungal agents. Because of its limit in formulation, PCZ oral suspension is recommended in immunocompromised patients with functional gastrointestinaltracts who fail conventional antifungal therapies or who are suspected to have a breakthrough fungal infection. However, a delayed-release tablet formulation and intravenous (IV) injection became available in 2014, expanding the use of PCZ in other patient populations, including individuals who are unable to take oral formulations.

Posaconazole plasma concentration in pediatric patients receiving antifungal prophylaxis after allogeneic hematopoietic stem cell transplantation

Posaconazole has been proven to be effective for antifungal prophylaxis in adults after hematopoietic stem cell transplantation (HSCT). Due to low gastrointestinal resorption of posaconazole suspension, bioavailability is impaired. Fatty food improves the uptake of posaconazole, but insufficient data on the pharmacokinetics of posaconazole in pediatric patients are available so far. The single-center analysis investigated 161 posaconazole serum concentrations in 27 pediatric patients after HSCT receiving 12 mg·kg BW(-1)·d(-1) posaconazole suspension depending on age, gender, and intestinal graft-versus-host (iGvHD) disease, and the influence of posaconazole on cyclosporine A plasma concentrations. To improve the uptake of posaconazole, one patient cohort received higher fat nutrition with the drug administration. A comparison of the regular nutrition and higher-fat nutrition groups revealed the following values: 31 (27.4%) versus 8 (16.7%) < 500 ng/ml; 12 (10.6%) versus 7 (14.6%) 500-700 ng/ml; 8 (7.1%) versus 6 (12.5%) 700-1000 ng/ml; 51 (45.1%) versus 21 (43.8%) 1000-2000 ng/ml; and 11 (9.7%) versus 6 (12.5%) > 2000 ng/ml. The mean posaconazole concentrations in patients with regular nutrition was 1123 ± 811 ng/ml and with higher-fat nutrition was 1191 ± 673 ng/ml. Posaconazole levels in patients with iGvHD were significantly lower (P = 0.0003) than in patients without GvHD. The majority of samples showed a sufficient posaconazole concentration above 700 ng/ml. Posaconazole levels were slightly higher in patients with higher-fat nutrition and significantly lower in patients with iGvHD. Cyclosporine A levels were not significantly higher during posaconazole administration.

Consensus guidelines for optimising antifungal drug delivery and monitoring to avoid toxicity and improve outcomes in patients with haematological malignancy, 2014

Antifungal agents may be associated with significant toxicity or drug interactions leading to sub-therapeutic antifungal drug concentrations and poorer clinical outcomes for patients with haematological malignancy. These risks may be minimised by clinical assessment, laboratory monitoring, avoidance of particular drug combinations and dose modification. Specific measures, such as the optimal timing of oral drug administration in relation to meals, use of pre-hydration and electrolyte supplementation may also be required. Therapeutic drug monitoring (TDM) of antifungal agents is warranted, especially where non-compliance, non-linear pharmacokinetics, inadequate absorption, a narrow therapeutic window, suspected drug interaction or unexpected toxicity are encountered. Recommended indications for voriconazole and posaconazole TDM in the clinical management of haematology patients are provided. With emerging knowledge regarding the impact of pharmacogenomics upon metabolism of azole agents (particularly voriconazole), potential applications of pharmacogenomic evaluation to clinical practice are proposed.

How we treat invasive fungal diseases in patients with acute leukemia: the importance of an individualized approach

Invasive fungal diseases (IFDs) represent an important cause of treatment failure in adults with acute leukemia. Because of leukemia’s heterogeneity, the risk for IFDs is highly variable. We therefore apply a risk-adapted antifungal strategy with strong emphasis on pretreatment and day-15 posttreatment to allow earlier and more individualized interventions. We determine pretreatment risks for IFDs based on 4 factors: (1) host fitness for standard therapy (ie, fit, unfit, or frail); (2) leukemia resistance (high vs low probability of achieving complete remission [CR]); (3) anticipated treatment-related toxicity such as neutropenia, mucositis, and steroid-induced immunosuppression; and (4) patient exposure to opportunistic fungi. Accordingly, we stratify patients as high, intermediate, or low risk for IFDs and apply risk-adapted antifungal strategies, including primary or secondary prophylaxis and diagnostic-based preemptive or empiric therapy. Prevention of IFDs also relies on optimizing organ function, decreasing exposure to opportunistic fungi, and improving net state of immunosuppression with use of better-tolerated and investigational agents for unfit patients and those with adverse leukemia biology. Novel targeted and safe therapies that can achieve higher rates of sustained CR among patients with adverse genetics offer the best promise for reducing the burden of IFDs in these patients.

Treatment principles for the management of mold infections

Survival rates among immunocompromised patients with invasive mold infections have markedly improved over the last decade with earlier diagnosis and new antifungal treatment options. Yet, increasing antifungal resistance, breakthrough infections with intrinsically resistant fungi, and potentially life-threatening adverse effects and drug interactions are becoming more problematic, especially with prolonged therapy. Evidence-based recommendations for treating invasive aspergillosis and mucormycosis provide excellent guidance on the initial workup and treatment of these molds, but they cannot address all of the key management issues. Herein, we discuss 10 general treatment principles in the management of invasive mold disease in immunocompromised patients and discuss how these principles can be integrated to develop an effective, individualized treatment plan.

Impact of structured personal on-site patient education on low posaconazole plasma concentrations in patients with haematological malignancies

Low posaconazole plasma concentrations (PPCs) are associated with breakthrough invasive mould infections among patients with haematological malignancies. This study evaluated the influence of structured personal on-site patient education on low PPCs. The study was conducted from July 2012 to May 2013 at the Division of Hematology, Medical University Hospital of Graz (Graz, Austria). PPCs were measured in all patients with haematological malignancies receiving the drug prophylactically. Concentrations above the target of 0.5 mg/L were defined as satisfactory and those below this concentration as low. In patients with low PPCs, structured personal on-site education regarding the intake of posaconazole (e.g. intake with fatty/acid food, prevention of nausea and vomiting) was performed. In total, 258 steady-state PPCs were measured in 65 patients [median PPC 0.59 mg/L, interquartile range 0.25-0.92 mg/L; 141/258 (54.7%) satisfactory]. Diarrhoea was the strongest predictor of low PPCs in the multivariate analysis. Initial steady-state PPCs were sufficient in 29 patients and low in 36 patients. Of the 36 patients with low initial steady-state PPCs, 8 were either discharged or antifungal therapy was modified before a follow-up PPC was obtained; in the remaining 28 patients, personal on-site education was performed. In 12/28 patients (43%) the personal on-site education led to sufficient levels, whilst in 16 (57%) PPCs stayed below the target, although increasing from <0.2 mg/L to >0.3 mg/L in 6 of these patients. In conclusion, personal education appears to be a promising tool to increase low PPCs.

Factors influencing posaconazole plasmatic concentrations in patients presenting with acute myeloid leukemia

PURPOSE

The effectiveness of posaconazole (PSZ) prophylaxis on invasive fungal infections, in patients presenting with acute myeloid leukemia (AML), seems to be correlated to its blood plasma concentration. Our goal was to identify the risk factors for underdosing.

PATIENTS AND METHODS

We retrospectively reviewed the records of patients treated for AML treated with PSZ, during a 2-year period. Assays<500ng/mL were considered as under dosed.

RESULTS

Fifty-nine assays (43 patients) were performed during induction (n=22) or consolidation (n=37) chemotherapy. PSZ treatment was initiated within a median of 3 days before neutropenia with a first assay performed at 8 days (3-28). The median PSZ blood plasma concentration was 375ng/mL (<200-1900). Forty-one (69%) treatment were maintained until the end of neutropenia. One patient presented with candidemia, 9 with possible invasive aspergillosis, without any significant association with underdosing. The univariate analysis showed that co-administration of proton pump inhibitors (PPIs) (P=0.01) and cause of hospitalization (induction chemotherapy vs consolidation, P=0.008) were associated with underdosing, contrary to feeding difficulties (P=0.07) and digestive disorders (P=0.5). The multivariate analysis confirmed the impact of PPI use (P=0.01) and the cause of hospitalization (P=0.003).

CONCLUSION

This study highlights the major impact of PPI administration on PSZ blood plasma levels and stresses the risk of non-effective prophylaxis during induction treatment of AML.