Safety of Isavuconazonium Sulfate in Pediatrics Patients With Hematologic Malignancies and Hematopoietic Cell Transplantation With Invasive Fungal Infections: A Real World Experience

An update on pharmacotherapy for fungal infections in allogeneic stem cell transplant recipients

INTRODUCTION

Invasive fungal diseases (IFD) constitute a major cause of morbidity and mortality in hematopoietic stem cell transplantation (HSCT) recipients.

AREAS COVERED

We describe epidemiology, causes and risk factors of IFD in allogeneic HSCT discussing prophylaxis and treatment in various HSCT phases. We present the most recent studies on this thematic area, including novel data on currently available antifungals, i.e. formulations, dosing, safety, efficacy and therapeutic drug monitoring. Finally, we present the most recent relevant recommendations published. Literature search included PubMed, Scopus and clinicaltrials.gov between January 2014-April 2024.

EXPERT OPINION

The antifungal agents employed for prophylaxis and therapy should be predicated on local epidemiology of IFD. Fluconazole prophylaxis remains a first-line choice before engraftment when the main pathogen is Candida spp. After engraftment prophylaxis should be with mold-active agents (i.e. triazoles). For candidiasis echinocandins are suggested as first-line treatment, whereas aspergillosis responds well to mold-active azoles and liposomal amphotericin B (L-AmB). For mucormycosis treatment of choice includes L-AmB and isavuconazole. Choice between fever-driven and diagnostics-driven strategies remains equivocal. Open research topics remain: 1) optimization of tools to ensure prompt and accurate IFD diagnosis to avoid unnecessary exposure to antifungals, drug interactions and cost; 2) refinement of treatment for resistant/refractory strains.

Characterization of the Use and Efficacy of Isavuconazonium Sulfate in a Pediatric Oncology and Stem Cell Transplant Population: A Single Institution Retrospective Review

Isavuconazonium sulfate (ISA) is a triazole antifungal approved for the treatment of invasive aspergillosis and mucormycosis in adults. This single-center, retrospective review of pediatric oncology and stem cell transplant patients receiving ISA for prophylaxis (n=20) or treatment (n=6) of invasive fungal disease (IFD) aims to characterize real-world clinical efficacy and toxicity of ISA in patients <18 years of age. Of 20 patients receiving ISA for prophylaxis, three patients had presumed breakthrough IFD (1 proven, 2 probable/possible). No adverse effects were attributed to ISA use or led to the discontinuation of therapy.

Isavuconazole use and TDM in real-world pediatric practice

Isavuconazole (ISA) is approved for treating invasive aspergillosis and mucormycosis in adults, but its use in children remains off-label. We report on the use of ISA in real-world pediatric practice with 15 patients receiving ISA for treatment of invasive fungal infections. Therapeutic drug monitoring (TDM) was performed in all patients, with 52/111 (46.8%) Ctrough determinations out of range, thus supporting the need for TDM in children, especially those receiving extracorporeal membrane oxygenation (ECMO).

Real-World Comparison of Isavuconazole and Voriconazole in Terms of the Need for Dosage Adjustments Guided by Clinical Pharmacological Advice During Primary Prophylaxis of Invasive Fungal Infections in Pediatric Patients with Hemato-Oncological Malignancies

BACKGROUND

Limited evidence concerning optimal azole dosing regimens currently exists for antifungal prophylaxis in hemato-oncological pediatric patients.

METHODS

Hemato-oncological children receiving intravenous or oral isavuconazole or voriconazole for primary antifungal prophylaxis at IRCCS Azienda Ospedaliero-Universitaria of Bologna during November 2020 to October 2021 and undergoing CPA programs based on real-time therapeutic drug monitoring (TDM) were retrospectively analyzed. CPAs for isavuconazole and voriconazole and the number of dosage adjustments were collected. Normalized trough concentrations [(C min )/dose/kg] were calculated for both drugs at each TDM assessment, and the coefficient of variation was determined. The efficacy and safety of the drugs were evaluated.

RESULTS

Sixteen hemato-oncological pediatric patients received azole prophylaxis (mean age and weight: 9.1 ± 4.9 years and 32.6 ± 16.0 kg; 6 isavuconazole and 10 voriconazole). Sixty and 89 CPAs were delivered as isavuconazole and voriconazole, respectively. Dosage adjustments were needed in 3.3% of cases for isavuconazole and 53.9% of cases for voriconazole ( P < 0.001). At first TDM, achievement of the desired target during standard dosing regimens was higher for isavuconazole (83.3%) than for voriconazole (10.0%; P = 0.008). Dispersion of normalized concentrations was higher for voriconazole (CV = 139.1% vs. CV = 79.4%). Elevation of ALT and aspartate aminotransferase levels between baseline and the third month was higher in patients receiving voriconazole (median, 28 vs. 90 U/L; P = 0.038, and 19 vs. 65.5 U/L; P = 0.002).

CONCLUSIONS

Our findings suggest that there is limited variability in isavuconazole exposure in hemato-oncological pediatric patients receiving azole prophylaxis , resulting in a low need for CPA-guided dosage adjustments.

Isavuconazole Treatment for Invasive Fungal Infections in Pediatric Patients

This work’s objective was to evaluate the safety of isavuconazole (ISA) as a treatment or prophylaxis for invasive fungal infections (IFIs) in immunocompromised children. IFI was reported as proven or probable according to international definitions. Therapeutic drug monitoring was performed using mass tandem spectrometry to quantify trough plasma concentrations. Targeted ISA levels were 2−4 mg/L, as reported in adult series. Nine patients received ISA as a curative treatment, and six received ISA as prophylaxis. IFIs were proven in four cases and probable in five. The median ISA trough plasma concentration in curative use was 3.19 mg/L [0.88;5.00], and it was 2.94 mg/L [2.77;3.29] in the prophylactic use. The median durations of treatment were 81 days [15;276] and 95 days [15;253], respectively. Three patients had elevated aspartate aminotransferase and alanine aminotransferase, and three patients had elevated creatinine serum. The IFI response was satisfactory in all cases at day 90. No side effects were reported. No patients developed an IFI. Our data underline the safety of an ISA 100 mg dosing regimen in children of <30 kg, which we recommend in this fragile population. We suggest that ISA plasma levels are monitored 10 days after ISA initiation and then every two weeks, alongside guided therapeutic drug monitoring (TDM) administration.