Drug repositioning evidence level Quality of scientific evidence
0 No evidence; includes in silico predictions without confirmation
1 In vitro studies with limited value for predicting in vivo/human situation
2 Animal studies with hypothetical relevance in humans
3 Incomplete studies in humans at the appropriate dose e.g. proof of concept; few cases from medical records; some clinical effects observed
4 Well-documented clinical end points observed for repositioned drug at doses within safety limits