Beyond the need for evidence that a drug works, Food and Drug Administration (FDA) and other regulatory bodies around the world need to see that a compound will be safe to give to patients in a clinical setting. Among other chemistry, manufacturing, and biology standards, key components of a successful investigational new drug (IND) or equivalent application include a sound pharmacokinetic (PK) profile encompassing absorption, distribution, metabolism, and excretion, drug transporter activity, and pharmacokinetic-based drug-drug interaction (DDI) potential.