IMP Investigational Medicinal Product: an unlicensed new drug, or an existing drug tested outside its licence, or existing drugs tested against each other for their efficacy/safety. The MHRA provide an algorithm to establish whether a study is a CTIMP: see Resource 2 or the MHRA website (provided on p67) http://www.mhra.gov.uk/home/groups/l-unit1/documents/websiteresources/con009394.pdf