A drug molecule "invented" by artificial intelligence (AI) will be used in human trials in a world first for machine learning in medicine.It was created by British start-up Exscientia and Japanese pharmaceutical firm Sumitomo Dainippon Pharma.The drug will be used to treat patients who have obsessive-compulsive disorder (OCD).Typically, drug development takes about five years to get to trial, but the AI drug took just 12 months.Exscienta chief executive Prof Andrew Hopkins described it as a "key milestone in drug discovery".