As the first approved oral kinase inhibitor, tofacitinib is effective and well-tolerated, but more expensive than conventional treatments for uncontrolled rheumatoid arthritis. Public formulary listing typically exerts a positive impact on the uptake of new drugs. We aimed to assess the budgetary impact of introducing tofacitinib into the Hospital Authority Drug Formulary as a fully subsidised drug in Hong Kong.
We applied a population-based budget impact model to trace the number of eligible patients receiving biologics or tofacitinib treatment, then estimated the 5-year healthcare expenditure on rheumatoid arthritis treatments, with or without tofacitinib (2017-2021). We used linear regression to estimate the number of target patients and compound annual growth rate to estimate market share. Competing treatments included abatacept, adalimumab, certolizumab pegol, etanercept, golimumab, infliximab, and tofacitinib. Retail price was used for drug costs, valued in Hong Kong dollars (HK$) in 2017 and discounted at 4% per year.
The annual treatment cost of tofacitinib was HK$74 214 per patient, and the costs of biologics ranged from HK$64 350 to HK$115 700. Without tofacitinib, the annual government health expenditures for rheumatoid arthritis treatment were estimated to increase from HK$147.9 million (2017) to HK$190.6 million (2021). The introduction of tofacitinib to the formulary would reduce healthcare expenditures by 17.3% to 20.3% per year, with cumulative savings of HK$192.8 million; this change was estimated to provide consistent savings (HK$66.4 million to HK$196.8 million) in all tested scenarios.
Introduction of tofacitinib to the formulary will provide 5-year savings, given the current drug price and patient volume.