The Medicines and Healthcare Products Regulatory Agency (MHRA) approves trials in the UK.

A similar process is happening in the US with the Food and Drug Administration (FDA). 

Both organisations analyse the data from the trials. Sometimes, they can visit other countries and trial sites to examine all available data before deciding and granting the drug a license.

The answer is provided by Karen Faulkner,

Senior Research Physician  at Synexus Clinical Research Ltd