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Over the past 20 years, there has been a growing recognition that the discovery of effective therapeutic agents involves designing compounds that possess appropriate “pharmaceutical” or “drug-like” properties in addition to high affinity for their biological targets. The pharmaceutical or drug-like properties include solubility, permeation across barriers such as the intestinal epithelium or blood-brain barrier, and metabolic and excretory clearance. Appropriate balance of these properties enables drug molecules to attain and maintain sufficient systemic and/or target concentrations to exert therapeutic effects through optimum absorption, distribution, metabolism, and excretion (ADME) processes. The ADME processes, in conjunction with the biological properties, define therapeutic profiles of drug molecules (Thakker, 2006). A drug that is poorly absorbed, rapidly metabolized, or rapidly excreted via the renal or hepatic route will not attain its full therapeutic potential. Such a drug will require higher doses to achieve sufficiently high systemic or target concentrations for efficacy, which may not be practical in some cases or may cause adverse effects in others. Thus, good pharmaceutical or drug-like properties are often defined as physicochemical properties of drug candidates that enable a drug candidate to navigate through the physical, biochemical, and physiological barriers posed by the ADME processes. The pharmaceutical properties of a drug candidate are optimized by de novo designing appropriate physicochemical attributes into the molecule or via formulation of the drug candidate with agents that can improve certain aspects of the physicochemical properties.