Posaconazole plasma concentrations in pediatric patients receiving antifungal prophylaxis during neutropenia

A Review of Population Pharmacokinetic Models of Posaconazole

Posaconazole is often used for the prophylaxis and treatment of invasive fungal infections (IFI). However, intra- and inter-individual differences and drug interactions affect the efficacy and safety of posaconazole. Precision dosing of posaconazole based on the population pharmacokinetic (PopPK) model may assist in making significant clinical decisions. This review aimed to comprehensively summarize the published PopPK models of posaconazole and analyze covariates that significantly influence posaconazole exposure. Articles published until May 2022 for PopPK analysis of posaconazole were searched in PubMed and EMBASE databases. Demographic characteristics, model characteristics, and results of PopPK analysis were extracted from the selected articles. In addition, the steady-state pharmacokinetic profiles of posaconazole were simulated at different covariate levels and dosing regimens. Out of the 13 studies included in our review, nine studies included adults, three included children, and one included both adults and children. All oral administration models were one-compartment models, and all intravenous administration models were two-compartment models. Body weight, proton pump inhibitors, and incidence of diarrhea were found to be important covariates. Clinically, the potential impact of factors such as patient physiopathologic characteristics and comorbid medications on posaconazole pharmacokinetics should be considered. Dose adjustment in combination with TDM or replacement with a tablet or intravenous formulation with higher exposure may be an effective way to ensure drug efficacy as well as to reduce fungal resistance. Meanwhile, published models require further external evaluation to examine extrapolation.

Dose Optimisation of Posaconazole and Therapeutic Drug Monitoring in Pediatric Patients

Experience in the clinical use of posaconazole (PCZ) in pediatric patients is limited, and no specific dose recommendations exist. This study aimed to investigate an appropriate dosing regimen, and assess the exposure-response relationships of PCZ in children. We reviewed the medical records of inpatients aged <18 years who subjected to PCZ concentrations monitoring. Clinical data, PCZ dosing and monitoring data were collected. A total of 375 PCZ trough concentrations (C _min) from 105 pediatric patients were included. For children receiving PCZ for prophylaxis, the median doses required to achieve the therapeutic range at the ages of <6, 6-12 and >12 years were 14.80, 14.52 and 12.90 mg/kg/day, respectively (p = 0.001); and for those receiving PCZ for treatment, the median doses were 23.50, 20.96 and 15.38 mg/kg/day, respectively (p = 0.001). Among children taking PCZ for prophylaxis, 12% developed a proven or probable breakthrough IFIs; the median PCZ concentrations were significantly lower than those children with successful treatment response (0.43 versus 1.20 μg mL^-1; p < 0.001). 79.2% patients taking PCZ for treatment had a positive clinical response, and the median PCZ concentrations were significantly higher than those children with disease progression (1.06 versus 0.53 μg mL^-1; p = 0.024). No association between C _min values and hepatotoxicity was observed. Factors such as age, CRP, ALT and co-administration with proton pump inhibitors exhibited significant effects on PCZ C _min. It is necessary to adjust the dosing regimens based on PCZ C _min to individualize antifungal therapy and provide guidelines for dose adjustment in children.

Antifungal Prophylaxis With Posaconazole in Immunocompromised Children Younger Than 13 Years

OBJECTIVE

Prophylaxis with posaconazole (PP) is effective in the prevention of invasive fungal infections in immunocompromised adult patients. However, evaluation of its effectiveness and safety in children is limited. The aim of the study was to describe the use of posaconazole as antifungal prophylaxis in children.

METHODS

We reviewed the medical records of immunocompromised patients younger than 13 years with hematologic diseases and post hematopoietic stem cell transplant (HSCT) who received antifungal PP at the Instituto Nacional de Salud del Niño San Borja (INSN-SB) in Lima, Peru, from January 2014 to December 2018.

RESULTS

Fifty-six courses of PP were identified in 47 patients with a median age of 7.5 years (IQR, 4-10), 51.6% (n = 24) of whom were female. The main underlying medical conditions were aplastic anemia (n = 19, 33.9%), acute lymphoblastic leukemia (n = 18, 32.1%), acute myeloid leukemia (n = 14, 25.0%), and 34.1% had undergone HSCT. The median dose of posaconazole was 13.62 mg/kg/day (IQR, 12.0-16.8), and the median duration of PP was 24 days (IQR, 16-82). Gastrointestinal symptoms included abdominal pain (17.9%), nausea (16.1%), diarrhea (7.1%), and vomiting (3.6%). Elevated alanine aminotransferase and aspartate aminotransferase levels were observed in 9/35 patients (25.7%) and 10/51 (19.6%) patients, respectively. Five cases of breakthrough fungal infection were identified (8.9%).

CONCLUSIONS

Patients younger than 13 years who received PP showed an increase in transaminase values, and the development of breakthrough fungal infections.

Antifungal Prophylaxis with Posaconazole versus Fluconazole in Children with Neutropenia Following Allogeneic Hematopoietic Stem Cell Transplantation: Single Center Experience

Background

Invasive fungal diseases (IFDs) are common and contribute to mortality in patients undergoing hematopoietic stem cell transplantation (HSCT). The relative efficacies of posaconazole (POS) and fluconazole (FLU) as primary antifungal prophylaxes are uncertain.

Methods

A retrospective study was performed on children treated with allogeneic HSCT who received POS or FLU during the early neutropenic period. The efficacies, safety, and tolerabilities of the prophylaxes were compared.

Results

Data on 78 HSCT recipients were analyzed. Most had thalassemia (58%). Pre-engraftment, POS and FLU were administered to 41 and 37 cases, respectively. There were no proven cases of IFD. However, 2 POS cases and 1 FLU case had probable IFDs. The IFD incidences of the POS (5%) and FLU (3%) groups demonstrated no statistical difference (p = 0.620). Of the 75 surviving cases receiving FLU post-engraftment (including 39 cases previously given POS), 3 had proven IFDs whereas 3 had probable IFDs (total, 6 [8%]) within 1 year post-HSCT. No cases discontinued the prophylaxes due to drug intolerance. The common adverse events with POS and FLU were not significantly different. Only 19% of the patients achieved the therapeutic POS level, with a starting dose of 4 mg/kg thrice daily.

Conclusion

POS and FLU demonstrate comparable levels of effectiveness, safety, and tolerability as IFD prophylaxes for neutropenic children treated with allogeneic HSCT. Determination of the optimum POS dose and duration requires larger studies.

Antifungal Triazole Posaconazole Targets an Early Stage of the Parechovirus A3 Life Cycle

Viruses in species Parechovirus A (Picornaviridae) are associated with a wide variety of clinical manifestations. Parechovirus A3 (PeV-A3) is known to cause sepsis-like illness, meningitis, and encephalitis in infants and young children. To date, no specific therapies are available to treat PeV-A3-infected children. We had previously identified two FDA-cleared antifungal drugs, itraconazole (ITC) and posaconazole (POS), with potent and specific antiviral activity against PeV-A3. Time-of-addition and synchronized infection assays revealed that POS targets an early stage of the PeV-A3 life cycle. POS exerts an antiviral effect, evidenced by a reduction in viral titer following the addition of POS to Vero-P cells before infection, coaddition of POS and PeV-A3 to Vero-P cells, incubation of POS and PeV-A3 prior to Vero-P infection, and at attachment. POS exerts less of an effect on virus entry. A PeV-A3 enzyme-linked immunosorbent assay inhibition experiment, using an anti-PeV-A3 monoclonal antibody, suggested that POS binds directly to the PeV-A3 capsid. POS-resistant PeV-A3 strains developed by serial passage in the presence of POS acquired substitutions in multiple regions of the genome, including the capsid. Reverse genetics confirmed substitutions in capsid proteins VP0, VP3, and VP1 and nonstructural proteins 2A and 3A. Single mutants VP0_K66R, VP0_A124T, VP3_N88S, VP1_Y224C, 2A_S78L, and 3A_T1I were 4-, 9-, 12-, 34-, 51-, and 119-fold more resistant to POS, respectively, than the susceptible prototype strain. Our studies demonstrate that POS may be a valuable tool in developing an antiviral therapy for PeV-A3.