Fig. 1. (A) Higher TPSA values are observed in clinical drugs employing non-oral routes of administration. (B) There is a clear positive correlation between MW and TPSA for clinical drugs. (C) A positive correlation also exists for clinical drugs between the number of HBAs and TPSA. (D) A linear regression model of TPSA with HBA and molecular weight as variables for clinical drugs. The linear fit is slightly improved relative to the model presented in (A). However, the p value of HBA being >0.05 suggests that the contribution of the HBA variable is not statistically significant.