OBJECTIVES: To estimate the cost-effectiveness of isavuconazole – a triazole antifungal agent indicated in Europe for the treatment of invasive aspergillosis (IA) and of mucormycosis in patients for whom amphotericin B is inappropriate – compared with current standard care, voriconazole, for the treatment of adult patients with possible IA in the United Kingdom (UK), when pathogen information is not available at treatment initiation.

METHODS: A decision tree model reflecting the real-world treatment of patients with possible IA was developed from the perspective of the UK National Health Service. The model estimated the incremental costs (including costs of drugs, laboratory analysis, hospitalisation and management of adverse events) and clinical outcomes (including life-years and quality-adjusted life-years (QALYs)) of isavuconazole compared with voriconazole. To extrapolate to a lifetime horizon, the model considered expected survival based on patients’ underlying condition. The model assumed that 7.8% of patients with possible IA at treatment initiation actually had mucormycosis, and during treatment differential diagnostic information became available for 50% of all patients. The robustness of results was assessed by conducting deterministic and probabilistic sensitivity analyses.

RESULTS: Compared with voriconazole, treatment of possible IA patients with isavuconazole was associated with 0.48 more life-years and 0.39 more QALYs per patient and an additional cost of £3,228. This resulted in incremental cost-effectiveness ratios of £6,758 per life-year gained and £8,242 per QALY gained. Results were most sensitive to mortality of IA patients and treatment durations. Over 10,000 simulations, the likelihood of isavuconazole being cost-effective at a willingness-to-pay threshold of £30,000 per QALY was estimated to be 69.8%.

CONCLUSIONS: A cost per QALY result below the UK’s commonly used willingness-to-pay threshold suggests that use of isavuconazole for the treatment of patients with possible IA can be considered a cost-effective allocation of healthcare resources compared with voriconazole.