Background: The Orphan Regulation ((EC) No 141/2000) has successfully redirected private and public investment towards previously neglected areas through incentives, regulatory obligations and rewards. However, the growth in
the number of licensed orphan medicinal products (OMPs) has led to concerns about increased costs. The aims were to investigate the trend in the costs of OMPs to the National Health Service in Wales, to attribute costs of medicines
within and outside periods of marketing exclusivity, and estimate the contribution of individual medicines to the overall costs of OMPs.

Methods: Expenditure on OMPs in Wales was analysed between the 2014/15 and 2019/20 financial years using data on prescriptions dispensed in primary care, secondary care, and specialised commissioned services. OMP spend was
calculated as a proportion of total medicines expenditure, whether it was incurred during, or outside the marketing exclusivity period (MEP), and by therapeutic area and medicine.

Results: Overall spend on OMPs and all medicines increased from £32 m to £82 m, and from £1,030 m to £1,198 m, respectively, with the proportion of spend on OMPs more than doubling from 3.1% to 6.9% per annum. Average year-on-year growth in the costs of OMPs was 21%, compared to 2% for other medicines. Costs following MEP expiry contributed significantly to overall OMP costs, increasing from £8 m to £30 m, corresponding to an increase from 24%
to 37%. Treatments for ‘malignant disease and immunosuppression’, ‘nutrition and blood’ and the ‘respiratory system’ accounted for 90% of all OMP spend. Half of total OMP annual expenditure was on just 4 medicines in 2014/15,
increasing to 8 in 2019/20.

Conclusions: Both the number of OMPs and the amount spent on OMPs in Wales has increased over time, possibly as a consequence of favourable licensing conditions, permissive health technology assessment policies and dedicated
funding.