 Dr Len McEwen, inventor of EPD, speculated that the reason for the failure might have been that the beta glucuronidase enzyme preparation was inadvertently heated or frozen during storage in the hospital pharmacy, as it is sensitive to the storage temperature and enzyme from the same manufactured batch had been used to treat a number of patients successfully.However, there is no evidence available after the event to test this theory as the remaining trial materials were destroyed immediately after the trial ended.While the efficacy of EPD is sometimes the subject of controversy among the medical community, the safety of EPD is demonstrated in one study under the control of an Investigational Review Board and reported by the American EPD Society.