OBJECTIVES: To determine 4-year total drug costs for patients with relapsing multiple sclerosis (RMS) starting treatment on oral disease modifying therapies (DMTs), cladribine tablets (CladT), fingolimod (FTY), teriflunomide (TER) or dimethyl fumarate (DMF), based on the persistency data from a large real-world study.

METHODS: An Excel model was designed to calculate total costs at each time point and accrued drug cost over four years for each oral treatment, with the perspective of a hospital in Lisbon. Only hospital drug acquisition costs were considered. Treatment costs at each month were derived by summing the cost of oral DMTs in patients persisting with the cost of ocrelizumab, the most common second-line DMT. Probability of patients persisting on each oral DMT was derived from time-to-switch data from GLIMPSE, a real-world study evaluating treatment effectiveness of these oral DMTs in RMS patients in MSBase registry. Persistence in year four was assumed from linear regression of available 3-year data, with alternative estimations used in sensitivity analysis.

RESULTS: Overall, the accrued treatment cost of TER remained lower than DMF which remained lower than FTY. The treatment cost accrued for CladT increases at slower rate over time and is higher than all oral DMTs until month 28. But it becomes lower than all DMTs, FTY at month 29, DMF at month 39 and TER at month 44. Total 4-year treatment costs are 42.948€ for CladT, 44.911€ for TER, 50.815€ for DMF and 64.154€ for FTY. Neither changes to estimated patient weight for CladT nor changes to estimation of staying on treatment in the 4^th year changes the ranking order by end of year 4.

CONCLUSIONS: While FTY, DMF and TER may have lower costs in short-term period, due to high persistency of CladT, over a longer term of 4 years, CladT has the lowest accrued treatment costs.