New UK Clinical Trials Regulations Introduce Automatic Approval for Certain Modifications

The new UK clinical trials regulations, approved by Parliament in April 2025, will take effect on 28 April 2026, introducing a faster process for approving certain substantial modifications. Eligible changes, known as Route B substantial modifications, will benefit from automatic approval by the MHRA within 14 days of validation.

Sponsors must first assess whether a proposed change is substantial, minor, or a modification of an important detail, using a risk-based approach. Substantial modifications are classified as Route A or Route B; the latter qualifies for automatic approval based solely on the nature of the modification. Sponsors must clearly document their justification.

If Route B changes affect quality documentation (such as IMP dossiers, GMP, or labelling), this must be indicated in the cover letter for MHRA review. A pilot phase will run from 1 October 2025 to 31 March 2026, before full implementation in April 2026.

20-10-2025