For example, of 100 drugs for which Investigational New Drug applications are submitted to FDA, about 70 percent will successfully complete Phase I and go on to Phase II; about 33 percent of the original 100 will complete Phase II and go to Phase III; and 25 to 30 of the original 100 will clear Phase III (and, on average, about 20 of the original 100 will ultimately be approved for marketing).