Pharmacogenomics (PGx)

Key facts

FDA labeling resource

Table of Pharmacogenomic Biomarkers in Drug Labeling

FDA association resource

Table of Pharmacogenetic Associations, three sections

Common genes

CYP2D6, CYP2C19, CYP2C9, DPYD, TPMT, HLA-B

Metabolizer phenotypes

Poor, intermediate, normal, rapid, ultrarapid

What is pharmacogenomics?

Pharmacogenomics links germline genetic variants to differences in drug response. Some variants change enzymes that break drugs down, raising or lowering drug levels in the blood. Others, such as certain HLA-B alleles, are associated with severe immune reactions to specific drugs.

Pharmacogenetics is often used interchangeably. Strictly, pharmacogenetics refers to single genes and pharmacogenomics to the genome as a whole, but the distinction is rarely enforced.

Most pharmacogenomic testing looks at germline variants. Tumor variants that predict response to cancer drugs are usually discussed as predictive biomarkers and companion diagnostics instead.

How pharmacogenomic information is used

Pharmacogenomic knowledge reaches practice through several channels:

• Drug labeling: FDA-approved labels mention biomarkers in sections from Boxed Warning to Clinical Pharmacology; the FDA table lists these by drug and gene.
• FDA Table of Pharmacogenetic Associations: separates associations that support therapeutic management recommendations from those showing a potential safety or response impact, or a pharmacokinetic effect only.
• Genotype to phenotype translation: star allele names, such as CYP2D6*4, describe gene haplotypes, and combinations of star alleles are mapped to metabolizer categories.
• Professional guidelines, such as those from the Clinical Pharmacogenetics Implementation Consortium (CPIC).

Why pharmacogenomics matters

Pharmacogenomic labeling can narrow or reshape a drug market. A contraindication or boxed warning tied to a genotype creates demand for testing before prescribing, and it can shift use toward alternative drugs.

For drug developers, pharmacogenomic variation affects dosing, trial design and safety signals, and FDA reviewers may ask about it. For pricing and market access analysts, the gene named in a label is a useful way to group drugs that share testing requirements and payer coverage questions.

Limitations of pharmacogenomic evidence

The strength of evidence varies widely between drug-gene pairs, and a label mention does not always mean testing is required. Allele frequencies also differ across ancestral populations, so findings from one population may not transfer directly to another.