ABSTRACT
Biomarkers comprise a broad array of laboratory-based, physiological, and
behavioral characteristics that are measured as indicators of normal biological
processes, as pathogenic processes, or as pharmacological responses to
therapeutic interventions [1]. With few exceptions, such as viral load, biomarkers
are endogenous substances. Depending on the stage of drug development,
biomarker measurements can provide important mechanistic, efficacy, or toxicity
information. For example, biomarker data can be used to discover and select a
lead compound, generate pharmacokinetic/pharmacodynamic (PK/PD) models
[2,3] that aid in clinical trial design and expedite drug development, serve as
surrogates for a clinical or mortality endpoint [4], and optimize drug therapy
based on genotypic or phenotypic factors [5]. Additionally, biomarker data can
be useful to define which patients to enroll in a drug study or to stratify patients
within a clinical protocol.
