MHRA Updates Guidance on Modifying Clinical Trial Approvals: Introduction of Route A and B Processes

10th October 2025

MHRA Updates Guidance on Modifying Clinical Trial Approvals: Introduction of Route A and B Processes

Summary: The Medicines and Healthcare products Regulatory Agency (MHRA) has published updated guidance on modifying clinical trial approvals, effective from 28th April 2026. The new regulations introduce two categories for substantial modifications: Route A and Route B.

• Route A Substantial Modifications: These are modifications likely to have a significant impact on participant safety, rights, or data integrity. They require full assessment by both the licensing authority and the ethics committee.

• Route B Substantial Modifications: These modifications meet specific criteria and are eligible for automatic approval unless the licensing authority intervenes within 14 calendar days. They are subject to a risk-proportionate review and are designed to expedite the modification process.

To assist sponsors in determining the appropriate modification category, the MHRA has provided a decision tree and examples of modifications under each category. Additionally, a Route B substantial modification pilot is running from 1st October 2025 to 31st March 2026, allowing sponsors to receive responses within 14 days while familiarising themselves with the new criteria. 

Link: Clinical Trials for Medicines: Modifying a Clinical Trial Approval

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