Predictive approaches to increase absorption of compounds during lead optimisation

Introduction: Complex physicochemical and biological processes influence the oral absorption of a drug molecule. Consideration of these processes is an important activity during the optimisation of potential candidate molecules. Areas covered: The authors review the applications of physicochemical and structural requirements for intestinal absorption. Furthermore, they provide examples of how to aid the lead optimisation process through improvement of solubility and permeability. Expert opinion: The physicochemical requirements for absorption are solubility and permeability. Both are influenced by lipophilicity, but in the opposite way. The size of the molecule also affects both solubility and permeability. Several models can be used to estimate oral absorption from chemical structure or from measured physicochemical properties. Thus, logD–cMR model, the ‘golden triangle' model, Abraham solvation equations and absorption potential can be used as tools in the lead optimisation process. Measured values of s...