Question to the Department of Health and Social Care:

To ask the Secretary of State for Health and Social Care, whether (a) his Department, (b) his Department's agencies and (c) his Department's advisory bodies have made comparative assessments of the efficacy of (i) natalizumab Tysabri and (ii) natalizumab Tyruko for the treatment of multiple sclerosis.

Tyruko and Tysabri are United Kingdom licensed medicines. Tyruko is a biosimilar to the originator Tysabri. A biosimilar is a biological medicinal product that contains a version of the active substance of an already authorised original biological medicinal product. The guiding principle of authorising a biosimilar is to establish similarity between the biosimilar, Tyruko, and the originator, Tysabri, based on a comprehensive comparability exercise, ensuring that the previously proven safety and efficacy of the originator also applies to the biosimilar. This is assessed by the Medicines and Healthcare products Regulatory Agency (MHRA) during the process of obtaining a marketing authorisation.

Following the introduction of Tyruko to the UK, the MHRA has investigated reports of increased disability associated with suspected allergic reactions, known as immunogenicity, following treatment with Tyruko, mainly in patients who were switched from Tysabri. The majority of these reports originated from a single National Health Service centre and only a few patients had residual symptoms after stopping Tyruko or transferring back to Tysabri. The assessment noted that more reassuring real world data has been described by other centres, which indicates some heterogeneity in the experience. The MHRA’s review was considered by the Commission on Human Medicine’s Neurology, Pain and Psychiatry Expert Advisory Group, which concluded that there was no corroborative evidence that allergic reactions are associated with progressive disability or any lack of efficacy for Tyruko when compared with Tysabri. The group recommended enhanced pharmacovigilance measures, including a specific follow up questionnaire, and that the marketing authorisation holder should review the risk of allergic reactions every four months or so and submit their data to the MHRA for monitoring, until greater experience with Tyruko is gained. The MHRA communicated the findings and outcomes of this review to clinicians at an NHS England webinar on 2 May 2025.