OBJECTIVES: To estimate the 5-year budget and clinical impact of introducing isavuconazole – a triazole antifungal agent indicated in Europe for the treatment of invasive aspergillosis (IA) and for the treatment of mucormycosis when amphotericin B is inappropriate – to treat adult patients with possible IA in the United Kingdom (UK), when pathogen information is not available at treatment initiation.

METHODS: A budget impact model was developed to estimate the difference in overall spending (including costs of drugs, laboratory analysis, hospitalisation and management of adverse events (AEs)) and clinical outcomes (including mortality and AEs) following the introduction of isavuconazole to the UK National Health Service over 5 years. The model assumed that use of isavuconazole for the treatment of patients with possible IA would increase from 0% (current scenario) to 23.1% over 5 years at the expense of current standard care, voriconazole.

RESULTS: Over 5 years, in a population of 3,439 patients with possible IA, the model estimated that, compared with the current scenario, increased use of isavuconazole would increase total spending by 2.1%, reaching £98,701,886 in total (£28,699 per patient). This corresponds to an average 2.1% annual increase in overall spending. Spending on drugs was predicted to increase by 7.6%; however, cost offsets were achieved through reductions in hospitalisations (0.04%), AE-management (6.8%) and laboratory analysis requirements (6.6%). Additionally, increased use of isavuconazole reduced the number of deaths and AEs by 2.1% and 12.2%, respectively, compared with the current scenario.

CONCLUSIONS: The model projected that the introduction of isavuconazole to the UK healthcare system would lead to a small increase in total spending for the treatment of patients with possible IA over 5 years. However, it would have a favourable impact on clinical outcomes by reducing the number of potential deaths and AEs compared to treatment with voriconazole, which lacks mucormycosis activity.