ADME (absorption, distribution, metabolism and excretion) deficiency is one of the major causes of failure during drug development. In vitro screening of potential lead compounds and drug candidates in the early discovery phase has been employed as a more cost-effective approach to identify compounds that have unfavorable ADME characteristics. Many compounds with promising pharmacological characteristics never become drugs because they have poor solubility, quickly degrade in biological fluids and tissues or rapidly metabolized in the liver. All these liabilities ultimately result in low oral bioavailability.
