Determine whether a drug hits the target and has impact on the biological pathway

Evaluate MOA

PK/PD correlations and determine dose and schedule

Determine biologically effective dose

Research test used during drug development

Exploratory biomarkers that may help stratify patient populations for late stage trials

Drug dose

Drug-drug interactions

Early assessment of toxicity

Identify patients most likely to respond, or are least likely to suffer an adverse event when treated with a drug

Complementary/Companion diagnostic test (eg, HER2/neu, anaplastic lymphoma kinase (ALK) translocation, PD-L1 IHC)

Stratify patients into study arms

Biomarker of efficacy and/or safety

Identify mechanisms driving acquired or innate drug resistance

Therapy escape mechanisms

Clonal evolution of tumor

Mutation analyses (eg, KRAS mutation for EGFR antibodies)

Predicts course of disease independent of any specific treatment modality

Patient stratification into study arms

Surrogate end points

Circulating tumor cells (Cell Search), Gene expression profiling (PAM50, Mammaprint)

Approved registrational end points

Standard of care diagnostic tests (eg, LDL, HbA1c, viral load, blood pressure)