Dose Optimisation of Posaconazole and Therapeutic Drug Monitoring in Pediatric Patients

Real World Posaconazole Pharmacokinetic Data in Paediatric Stem Cell Transplant Recipients

Background: Invasive fungal disease is a significant cause of morbidity and mortality in allogeneic hematopoietic stem cell transplant (alloHSCT) recipients. Posaconazole, a broad-spectrum triazole, is widely used as prophylaxis. Methods: We conducted a monocentric, retrospective study to present real-world data on posaconazole trough levels in paediatric alloHSCT patients. The main objective was to determine the required daily dose of posaconazole in paediatric patients. We analysed factors influencing posaconazole levels, and the association between posaconazole levels and breakthrough fungal infection. Results: Among 102 allogeneic HSCT recipients, we measured posaconazole plasma concentrations in 548 blood samples. The required daily doses to reach a target range of 0.7-2.0 mg/L were 15.22 (suspension), 7.52 (tablet), and 7.84 mg/kg (intravenous). Patients aged < 13 years needed higher doses to achieve the target range. The presence of enteral symptoms during prophylaxis was associated with lower plasma concentrations (p < 0.001), while co-administration of proton pump inhibitors did not (p = 0.09). Eight breakthrough infections occurred; low levels of posaconazole (<0.7 mg/L) were observed in five out of eight cases. The Cox regression model showed that higher mean plasma concentrations decreased the hazard of breakthrough infections. Conclusions: The tablet and intravenous formulations of posaconazole outperformed the suspension in terms of predictability. Our analyses on breakthrough infections and posaconazole plasma levels suggest an exposure-response relationship.

Relationship between posaconazole concentrations and clinical outcomes in paediatric cancer and haematopoietic stem cell transplant recipients

BACKGROUND

Posaconazole is used to prevent and treat invasive fungal infections (IFIs) in immunocompromised children, including those undergoing cancer treatment or HSCT. Despite differences in pharmacokinetics and IFI epidemiology between children and adults, therapeutic targets established in adult studies are often applied to children.

OBJECTIVES

This systematic review evaluated the correlation between serum posaconazole concentrations and clinical outcomes of IFI prophylaxis and treatment in children with malignancies or HSCT recipients.

METHODS

Four databases (Cochrane, Embase, MEDLINE and PubMed) were searched for studies involving children (≤18 years old) receiving cancer treatment or HSCT that reported posaconazole serum concentrations and treatment outcomes. Animal studies, those primarily in adult (>18 years old) populations, non-malignant conditions (excluding HSCT), case reports, letters, editorials, conference abstracts and narrative reviews were excluded. Bias was assessed using the Newcastle-Ottawa scale.

RESULTS

Nineteen studies were included: 12 reported outcomes of posaconazole prophylaxis; two of treatment; and five of both. For prophylaxis, breakthrough IFIs occurred in 1%-12% of children. All but one occurred with serum concentrations of ≤0.7 mg/L. For treatment, no clear association was observed between a trough concentration of >1.0 mg/L and treatment efficacy, with poor outcomes reported for serum concentrations ranging between 0.2 and 4.8 mg/L. Overall, quality of evidence was poor (medium to high risk of bias for 18 papers, low risk for 1 paper) and there was variation in IFI definitions across studies.

CONCLUSIONS

This review supports current recommendations for posaconazole prophylaxis in paediatric oncology and HSCT recipients. The absence of a clear correlation found between serum trough concentrations and treatment efficacy highlights the need for further studies to determine optimal therapeutic targets for treatment.

Efficacy and Safety Assessment of Antifungal Prophylaxis with Posaconazole Using Therapeutic Drug Monitoring in Pediatric Patients with Oncohematological Disorders-A Single-Centre Study

INTRODUCTION

Posaconazole is recommended for prophylaxis in pediatric immunocompromised patients. Due to its variability in bioavailability and drug-to-drug interactions, EBMT recommends regimens based on therapeutic drug monitoring (TDM).

MATERIALS AND METHODS

In total, 171 oncohematological pediatric patients on posaconazole prophylaxis were included. Full pharmacokinetic posaconazole profiles were assessed in 51 children. The efficacy and safety of posaconazole was evaluated by measuring the drug concentration, with dose modification attempted in patients with suboptimal results. The influence of modifying factors on the posaconazole plasma concentration (PPC) was investigated.

RESULTS

An insufficient PPC was the main issue, but no significant increase in prophylaxis failure was reported. The modification of the dosage resulted in the optimization of PPC in 50% of patients. No significant correlation between age, gender, diagnosis or the posaconazole dosage and the PPC was found. HCT, total parenteral nutrition and diarrhea were associated with a lower PPC. Hypoalbuminemia was related to both higher and lower PPC. The concomitant administration of specified drugs significantly impacted the PPC.

CONCLUSIONS

TDM allows the identification of patients receiving non-optimal treatment and offers an opportunity to improve the efficacy and safety of the therapy. However, further research involving larger patient groups and longer observation periods are needed to determine the optimal dosing and target PPC in pediatric patients.

Therapeutic drug monitoring of posaconazole delayed-release tablets and injections in pediatric patients

This study aimed to investigate the dose and trough concentration (Cmin) of posaconazole delayed-release tablets and injections, and their correlation with efficacy and safety in pediatric patients. Patients younger than 18 years old received posaconazole delayed-release tablets or injections for prophylaxis or treatment of invasive fungal disease (IFD). Blood samples were collected to determine the plasma Cmins, and dose regimen adjustments were made if necessary. Clinical data were collected. A total of 210 Cmins of 113 pediatric patients were detected. The median Cmins were 1.0 and 1.3 mg/L for tablets and injections, respectively (P < 0.05). The median doses required to achieve the target Cmin were about 6.0 mg/kg of body weight/day, and no statistical difference was observed between different age groups, formulations, or indications (P > 0.05). Concomitant treatment of tacrolimus and diarrhea were found to affect Cmins of tablets, while age, gender, and BMI were found to be correlated with Cmins of injections. IFD breakthrough occurred in 9.2% of patients with a median Cmins of 0.74 mg/L for prophylaxis, and infection progression occurred in 43.2% of patients with a median Cmins of 0.97 mg/L for treatment, respectively. Transaminitis was the most common adverse event. Posaconazole delayed-release tablets and injections are safe for prophylaxis and treatment of IFD in pediatric patients. An empirical initial dose of 6.0 mg/kg of body weight/day is appropriate for prophylaxis, while a higher dose should be required for the treatment of IFD. It is necessary to adjust the dose regimen according to the results of therapeutic drug monitoring.This study is registered with chictr.gov.cn under identifier ChiCTR2300070008.

Posaconazole in paediatric malignancy and haematopoietic stem cell transplant: dosing to achieve therapeutic concentration

OBJECTIVES

Posaconazole is increasingly used for the treatment and prophylaxis of invasive fungal infections in immunocompromised children. We aimed to review evidence for paediatric posaconazole dosing regimens focusing on attainment of target concentrations and frequency of adverse effects.

METHODS

In May 2023, the Cochrane, Embase, MEDLINE and PubMed databases were searched for articles reporting posaconazole dosing in children with malignancy or post-haematopoietic stem cell transplantation. Studies reporting the attainment of target serum concentrations were included.

RESULTS

Overall, 24 studies were included. Eighteen studies of the oral suspension consistently reported poor attainment of target concentrations for prophylaxis (≥0.7 µg/mL, 12%-78%) despite high daily doses of 14-23 mg/kg/day (max. 1200 mg/day). Target attainment was significantly affected by gastric pH and food intake. Six studies of the delayed-release tablet (DRT) reported 58%-94% achieved concentrations ≥0.7 µg/mL, with the majority using lower doses of 4-12 mg/kg/day (max. 300 mg/day). Similarly, one study of powder for oral suspension found 67%-100% achieved target concentrations with a dose of 6 mg/kg/day (max. 300 mg/day). As expected, the IV formulation had high attainment of prophylaxis targets (81%-90%) with 6-10 mg/kg/day (max. 400 mg/day). All formulations were well tolerated, and no relationship between adverse effects and posaconazole concentrations was identified.

CONCLUSIONS

The required posaconazole dose in immunocompromised children varies depending on the formulation. The IV infusion had the highest attainment of therapeutic concentration followed by the DRT and powder for suspension. By contrast, the oral suspension had low attainment of target concentrations despite higher daily doses.

Dosing of IV posaconazole to treat critically ill patients with invasive pulmonary aspergillosis: a population pharmacokinetics modelling and simulation study

BACKGROUND

Posaconazole is used for the prophylaxis and treatment of invasive fungal infections in critically ill patients. Standard dosing was shown to result in adequate attainment of the prophylaxis Cmin target (0.7 mg/L) but not of the treatment Cmin target (1.0 mg/L).

OBJECTIVES

To provide an optimized posaconazole dosing regimen for IV treatment of patients with invasive pulmonary aspergillosis in the ICU.

METHODS

A population pharmacokinetics (popPK) model was developed using data from the POSA-FLU PK substudy (NCT03378479). Monte Carlo simulations were performed to assess treatment Cmin and AUC0-24 PTA. PTA ≥90% was deemed clinically acceptable. PopPK modelling and simulation were performed using NONMEM 7.5.

RESULTS

Thirty-one patients with intensive PK sampling were included in the PK substudy, contributing 532 posaconazole plasma concentrations. The popPK of IV posaconazole was best described by a two-compartment model with linear elimination. Interindividual variability was estimated on clearance and volume of distribution in central and peripheral compartments. Posaconazole peripheral volume of distribution increased with bodyweight. An optimized loading regimen of 300 mg q12h and 300 mg q8h in the first two treatment days achieved acceptable PTA by Day 3 in patients <100 kg and ≥100 kg, respectively. A maintenance regimen of 400 mg q24h ensured ≥90% Cmin PTA, whereas the standard 300 mg q24h was sufficient to achieve the AUC0-24 target throughout 14 days, irrespective of bodyweight.

CONCLUSIONS

We have defined a convenient, optimized IV posaconazole dosing regimen that was predicted to attain the treatment target in critically ill patients with invasive aspergillosis.

Therapeutic drug monitoring of antifungal therapies: do we really need it and what are the best practices?

INTRODUCTION

Despite advancements, invasive fungal infections (IFI) still carry high mortality rates, often exceeding 30%. The challenges in diagnosis, coupled with limited effective antifungal options, make managing IFIs complex. Antifungal drugs are essential for IFI management, but their efficacy can be diminished by drug-drug interactions and pharmacokinetic variability. Therapeutic Drug Monitoring (TDM), especially in the context of triazole use, has emerged as a valuable strategy to optimize antifungal therapy.

AREAS COVERED

This review provides current evidence regarding the potential benefits of TDM in IFI management. It discusses how TDM can enhance treatment response, safety, and address altered pharmacokinetics in specific patient populations.

EXPERT OPINION

TDM plays a crucial role in achieving optimal therapeutic outcomes in IFI management, particularly for certain antifungal agents. Preclinical studies consistently show a link between therapeutic drug levels and antifungal efficacy. However, clinical research in mycology faces challenges due to patient heterogeneity and the diversity of fungal infections. TDM's potential advantages in guiding Echinocandin therapy for critically ill patients warrant further investigation. Additionally, for drugs like Posaconazole, assessing whether serum levels or alternative markers like saliva offer the best measure of efficacy is an intriguing question.

Population Pharmacokinetics of Posaconazole in Immune-Compromised Children and Assessment of Target Attainment in Invasive Fungal Disease

BACKGROUND AND OBJECTIVE

Posaconazole (PSZ) is a triazole antifungal for the management of invasive fungal disease (IFD) in adults and children. Although PSZ is available as an intravenous (IV) solution, oral suspension (OS) and delayed-release tablets (DRTs), OS is the preferred formulation for pediatric use because of potential safety concerns associated with an excipient in the IV formulation and difficulty in swallowing intact tablets by children. However, poor biopharmaceutical characteristics of the OS formulation leads to an unpredictable dose-exposure profile of PSZ in children, potentially risking therapeutic failure. The goal of this study was to characterize the population pharmacokinetics (PK) of PSZ in immunocompromised children and assess therapeutic target attainment.

METHODS

Serum concentrations of PSZ were collected retrospectively from records of hospitalized patients. A population PK analysis was performed in a nonlinear mixed-effects modeling framework with NONMEM (v7.4). The PK parameters were scaled to body weight, then potential covariate effects were assessed. The final PK model was used to evaluate recommended dosing schemes through simulation of target attainment (as a percentage of the population having steady-state trough concentrations above the recommended target) using Simulx (v2021R1).

RESULTS

Repeated measurement data of 202 serum concentrations of total PSZ were acquired from 47 immunocompromised patients between 1 and 21 years of age receiving PSZ either intravenously or orally, or both. A one-compartment PK model with first-order absorption and linear elimination best fit the data. The estimated absolute bioavailability (95% confidence interval) for suspension (Fs) was 16% (8-27%), which was significantly lower than the reported tablet bioavailability (Ft) [67%]. Fs was reduced by 62% and 75% upon concomitant administration with pantoprazole (PAN) and omeprazole (OME), respectively. Famotidine resulted in a reduction of Fs by only 22%. Both fixed dosing and weight-based adaptive dosing provided adequate target attainment when PAN or OME were not coadministered with the suspension.

CONCLUSIONS

The results of this study revealed that both fixed and weight-based adaptive dosing schemes can be appropriate for target attainment across all PSZ formulations, including suspension. Additionally, covariate analysis suggests that concomitant proton pump inhibitors should be contraindicated during PSZ suspension dosing.