16. Urine drug screen at screening, pre-dose (Part A) or pre-inoculation (Part B) positive for any drug as listed in Section 9.2.4 unless there is an explanation acceptable to the medical Investigator (e.g. the subject has stated in advance that they consumed a prescription or over the counter product which contained the detected drug) and/or the subject has a negative urine drug screen on retest by the pathology laboratory.