Effectiveness of biosimilar adoption within a UK tertiary hospital; six-years follow up.

Health systems encourage switching from originators to biosimilars as biosimilars are more cost-effective. The speed and completeness of biosimilar adoption is a measure of efficiency. We describe the approach to biosimilar adoption at a single hospital and compare its efficiency against the English average. We additionally follow up patients who reverted to a previously used biologic, having switched to a biosimilar, to establish whether they benefitted from re-establishing prior treatment. The approach we describe resulted in a faster and more complete switch to biosimilars, which saved an additional £380,000 on drug costs in 2021/22. Of patients who reverted to their original biologic, 87% improved short-term, and a time on treatment analysis showed the benefit was retained long-term. Our approach to biosimilar adoption outperformed the English average and permits patients to revert to their original biosimilar post-switch if appropriate.