As lipophilicity is also directly linked to the affinity of the drug to adipose , the Kp for adipose tissue is an appropriate parameter for the RRF-BP model in the gut. Therefore, we can conclude that, although it is not easy to interpret the function of kidney Kp in the RRF-BP model of the gut, the chemical properties selected in the gut were understandable. Clustering of The Tissues by The Parameters Needed for Predicting Kp Next, to understand the relationship between each tissue, we analyzed the parameters used in the top 10 RRF-BP models for each tissue with a lower RMSE. We present the sum of the total instances for each item listed in Table . Most of the explanatory variables were selected for different Kp prediction models except the predicted Kp value of the liver. For example, in the liver, in addition to the highly expressed transporters there is another feature that does not follow the drug-free theory . This indicates that its distribution into the liver has a completely different mechanism from that in the other tissues.