Abstract
BACKGROUND/OBJECTIVES: Long-acting insulin glargine (iGlar) has been available as a biosimilar since 2014 in the UK. We reviewed previous prescribing to evaluate if the anticipated cost savings with biosimilars were realized with iGlar. METHODS: This study investigated prescribing patterns of long-acting iGlar (100 units/mL) in cartridges and pre-filled pens from 2020 to 2024 across primary care organizations in England, Northern Ireland, Scotland, and Wales. RESULTS: iGlar prescribing declined in all of the four nations. From 2020 to 2024, the total prescribed quantity of biosimilars persistently increased in all countries, reaching 24% in England, 5% in Northern Ireland, 24% in Scotland, and 11% in Wales, all in 2024. Consequently, the proportion of Lantus prescriptions (as quantity) decreased but continued to exceed that of all available iGlar products combined in all countries in all years analyzed. By 2024, Lantus was also priced lower than the most common biosimilar, Abasaglar, across all nations. CONCLUSIONS: The introduction of biosimilars does not automatically result in altered prescribing practices, though we show that the most commonly prescribed iGlar was also the least expensive product at the end of the analysis period. At launch and for several years after, biosimilars failed to gain strong utilization, despite cost advantages, highlighting the need for active switching policies and prescriber engagement.