unclassified drug article 1,192 nonhuman 1,052 priority journal 827 controlled study 805 Animals 594 human 411 Humans 381 animal cell 341 metabolism 284 Article 264 protein expression 252 animal experiment 237 human cell 222 mouse 222 animal 217 Mice 196 enzyme activity 183 chemistry 177 animal tissue 162 protein function 155 in vitro study 154 rat 149 drug structure 148 male 147 female 146 Female 141 Male 139 drug synthesis 139 chemical structure 136