unclassified drug article 1,073 nonhuman 952 priority journal 745 controlled study 722 Animals 529 human 368 Humans 334 animal cell 309 Article 264 metabolism 255 animal experiment 221 protein expression 219 animal 197 mouse 195 human cell 192 enzyme activity 170 Mice 167 chemistry 162 animal tissue 151 in vitro study 144 drug structure 140 male 139 female 138 rat 137 drug synthesis 134 Male 130 protein function 128 Female 127 chemical structure 126