Isavuconazole: Case Report and Pharmacokinetic Considerations

Area of Science:

• Mycology
• Pharmacology
• Hematology

Background:

• Invasive fungal disease (IFD) poses significant risks for immunocompromised patients.
• Voriconazole (VCZ) and posaconazole (PCZ) are common antifungals but have drug-drug interactions and pharmacokinetic variability.
• Isavuconazole (IVZ) is a newer antifungal with promising pharmacokinetic properties, but real-world data on its use and therapeutic drug monitoring (TDM) is limited.

Observation:

• A patient with acute lymphoblastic leukemia (ALL) developed probable invasive aspergillosis (IA) during chemotherapy.
• Initial treatment with VCZ led to severe hepatic toxicity due to high plasma levels.
• Switching to IVZ resulted in stable drug concentrations despite concurrent chemotherapy, but hepatic toxicity recurred.
• Hepatic toxicity resolved upon chemotherapy cessation, independent of IVZ levels, suggesting it was not directly related to IVZ plasma concentration.

Findings:

• Isavuconazole (IVZ) plasma concentrations remained stable throughout treatment in an ALL patient receiving concomitant chemotherapy.
• IVZ pharmacokinetics were unaffected by concurrent administration of multiple other medications.
• Hepatic toxicity observed during IVZ treatment was not correlated with IVZ plasma concentrations.

Implications:

• Isavuconazole (IVZ) may offer a safer alternative to older azoles in immunocompromised patients undergoing complex therapies.
• The findings suggest that TDM for IVZ might not be routinely required in clinical settings, simplifying treatment protocols.
• Further real-world studies are warranted to confirm the safety and efficacy of IVZ and its TDM requirements across diverse patient populations.