Efficacy and Safety of Isavuconazole

Isavuconazole (ISCZ) has demonstrated therapeutic efficacy for invasive fungal infections (IFIs); however, evidence supporting its prophylactic use remains limited. This study aimed to evaluate the real-world effectiveness and safety of ISCZ prophylaxis in patients with hematological malignancies at high risk for IFIs.

This retrospective study evaluated patients at high risk for IFI who received ISCZ as prophylaxis at our institution from June 2023 to June 2025. The primary outcome measure was the incidence of breakthrough IFI (bIFI) within 100 days after ISCZ initiation. The secondary outcome measures were the treatment continuation rate, mortality rate, adverse events, and changes in liver and kidney function.

Overall, 38 patients (median age, 67 years; median body weight, 54.1 kg) were evaluated. Most patients (97.4%) were treated in the hematology-oncology department. The median duration of ISCZ administration was 119 days. Treatment continuation/completion was achieved in 44.7% of the patients. No deaths attributable to IFI were observed during the study period. No breakthrough IFIs were identified within 100 days after ISCZ initiation, and no Grade ≥3 adverse events were definitively attributed to ISCZ.

In this cohort, no breakthrough IFIs occurred within 100 days after ISCZ prophylaxis initiation. Although Grade 3 or higher adverse events occurred, their causal relationship with ISCZ could not be definitively established in this retrospective study. These findings provide real-world data on ISCZ prophylaxis in patients at high risk for IFIs. Further validation in multicenter prospective studies is needed.