Isavuconazole as prophylaxis and therapy for invasive fungal diseases: a real-life observational study

Isavuconazole is a relatively new antifungal agent indicated for the management of various invasive fungal diseases (IFDs), including invasive aspergillosis. Information on real-world experience with isavuconazole is scarce. This retrospective observational study aimed to describe the usage of isavuconazole in clinical practice with an in-depth evaluation of individual isavuconazole exposure. Patients treated with isavuconazole were evaluated based on retrospective data, including therapeutic drug monitoring (TDM) data and efficacy and safety data. Additionally, we calculated the individual isavuconazole exposure described by the average AUC24 over the first 7 days of treatment by means of non-linear mixed-effects modelling and compared this with the currently desired lower target AUC of 60 mg·h/L. Ninety-nine patients treated with isavuconazole were evaluated. In our real-life cohort, isavuconazole was often deployed off-label in patients with non-classical host factors and infections with non-Aspergillus and non-Mucorales species. Isavuconazole was most often chosen for its safety profile, even after prior triazole treatment with manifestations of toxicity. TDM and subsequent dosage adjustments were frequently performed. The individual average AUC24 over 7 days was above 60 mg·h/L in 29 out of 77 (37.7%) patients. This overview provides practical insights that can aid clinicians in the management of their patients with IFD. Our study shows that isavuconazole was used in a diverse patient population and was well tolerated overall. Individual isavuconazole exposure reflected by the average AUC24 over the first 7 days of treatment was generally low and variable. Dosage adjustments following TDM were frequently performed. Our experience shows that isavuconazole is a feasible alternative after prior azole treatment.