Tolerability of isavuconazole after posaconazole toxicity in leukaemia patients

BACKGROUND: Posaconazole (PCZ) is widely used for prophylaxis or treatment of invasive fungal infections (IFIs) in leukaemia patients. However, issues with PCZ tolerability can result in treatment interruption. Isavuconazole (ISA) has a similar broad spectrum of activity to PCZ; however, real-world data regarding the tolerability of ISA after PCZ toxicity are lacking. OBJECTIVES: To describe the tolerability of ISA after PCZ toxicity in leukaemia patients. PATIENTS/METHODS: We retrospectively assessed tolerability of ISA after PCZ toxicity in adult leukaemia patients (March 2015 to November 2017). We included all patients who received ≥7 days of ISA within 48 hours of PCZ discontinuation. Laboratory markers for liver toxicity were collected at three time points: prior to PCZ, at switch to ISA and after ISA therapy. RESULTS: We identified 23 such patients. Increased liver function tests (LFTs) were noted in 20 patients on PCZ, while three patients had Grade 3/4 QTc prolongation. No patient discontinued subsequent ISA due to toxicity. Grade 3/4 elevations in LFTs were decreased after changing to ISA (30% after PCZ vs 5% after ISA). No patient had significant QTc prolongation after switching to ISA. CONCLUSIONS: Isavuconazole was well-tolerated in patients discontinuing PCZ due to toxicity, with no patient discontinuing ISA due to toxicity.