Clinical & Trials
Pharmacogenomics(PGx)
In one line
The study of how genetic variation affects an individual's response to drugs, used to guide dosing, drug selection, and companion diagnostic development.
Definition
Pharmacogenomics (PGx) is the study of how variation in genes, particularly those encoding drug-metabolizing enzymes, transporters, and drug targets, affects an individual patient's efficacy or risk of adverse reaction to a medication. FDA maintains a publicly available Table of Pharmacogenetic Associations that summarizes gene-drug pairs with evidence supporting an association between a genetic variant and altered drug metabolism, response, or risk of an adverse reaction, categorized by the strength of supporting scientific evidence. The Clinical Pharmacogenetics Implementation Consortium (CPIC) publishes peer-reviewed, evidence-graded clinical practice guidelines that translate PGx test results, such as CYP2C19 or CYP2D6 genotype, into actionable prescribing recommendations for specific drugs. PGx testing intersects directly with companion diagnostics when a test result is used to identify patients likely to benefit from, or be harmed by, a specific therapy named in the drug's labeling.
Why it matters
PGx is increasingly incorporated into drug labeling sections on dosage and administration, warnings, and clinical pharmacology, and FDA's Table of Pharmacogenetic Associations is distinct from, but complementary to, the FDA list of cleared or approved companion diagnostic devices. Laboratories offering PGx panels as laboratory-developed tests have historically operated under CLIA rather than FDA device clearance, a distinction under active regulatory discussion following FDA's LDT final rule and subsequent legal developments.
Common pitfalls
- •Assuming inclusion of a gene-drug pair in FDA's PGx table means the interaction is described in the approved drug label; the table includes associations with varying levels of evidence, some not yet reflected in labeling.
- •Treating a laboratory-developed PGx panel as equivalent in regulatory status to an FDA-cleared or approved companion diagnostic when it has not gone through the same premarket review.
- •Applying CPIC dosing guidance without confirming it matches the specific drug label and patient population under FDA's current labeling for that product.
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