ABOUT PHARMACOGENOMICS

The antibiotic that doesn't work, the pain medication that's ineffective — not because the drugs are wrong, but because your genes are processing them at a different speed than the dose imagined.

Whole genome sequencing identifies your CYP450 metabolizer phenotype, enabling physicians to select and dose medications that will work safely and effectively for your unique genetic makeup.

CYP2D6
CYP2C19
CYP3A4

About this condition

Pharmacogenomics — Drug Response

The cytochrome P450 family of drug-metabolizing enzymes are responsible for metabolizing more than 75% of all approved medications. Three genes — CYP3A4, CYP2D6, and CYP2C19 — are particularly important: CYP3A4 metabolizes approximately 50% of all drugs on the market, while CYP2D6 and CYP2C19 together metabolize another ~40%. These enzymes catalyze oxidation reactions that activate or inactivate drugs for excretion. Genetic variation in these genes creates four metabolizer phenotypes: poor metabolizers (PM) with very low enzyme activity, intermediate metabolizers (IM) with reduced activity, normal/extensive metabolizers (NM/EM, the wild-type), and ultra-rapid metabolizers (UM) with increased enzyme activity due to gene duplication or other structural variants.

CYP2D6 has 962 identified variants catalogued in the PharmGKB database, with complex structural variations including gene deletions (producing PM phenotype), duplications and multi-duplications (producing UM phenotype), and hybrid genes (producing variable function). CYP2C19 has 753 variants, predominantly affecting splicing, translation, and amino acid substitutions. CYP3A4 has 609 known variants. Loss-of-function variants produce low-activity phenotypes; gene duplications produce ultra-rapid metabolizers. The metabolizer phenotypes have profound clinical consequences: poor metabolizers may accumulate toxic drug levels on standard doses, while ultra-rapid metabolizers may achieve subtherapeutic concentrations.

Metabolizer phenotype determines safe and effective drug dosing across dozens of medication classes. Codeine, a prodrug activated by CYP2D6, provides no analgesia in poor metabolizers — they cannot convert codeine to its active metabolite morphine. Tricyclic antidepressants and antipsychotics accumulate to toxic levels in CYP2D6 poor metabolizers. CYP2C19 poor metabolizers cannot adequately activate clopidogrel (Plavix), reducing its antiplatelet effect and increasing stent thrombosis risk. Clinical Pharmacogenetics Implementation Consortium (CPIC) publishes peer-reviewed dosing recommendations for >300 drug-gene pairs, guiding healthcare providers in optimizing medication selection and dosing.

Gene locus: CYP2D6 (22q13.2), CYP2C19 (10q23.33), CYP3A4 (7q22.1)

Standard panels test 10-30 'star alleles' per gene. They miss novel and rare variants, particularly in under-represented populations.

Standard panels miss rare variants and structural variations

Standard pharmacogenomics panels test only 10-30 'star alleles' (haplotypes) per gene — pre-defined combinations of common variants. This approach captures the most common variants in most populations but misses novel or rare variants, particularly in under-represented populations. CYP2D6 poses particular challenges: copy number variation (CNVs — deletions and duplications) cannot be reliably detected by standard sequencing alone; specialized copy number detection methods are required. A patient may carry rare novel variants not represented on a standard panel, producing incorrect metabolizer phenotype prediction. Whole genome sequencing with copy number analysis provides comprehensive variant detection, allowing phenotype calculation from all detected variants rather than only pre-defined haplotypes.

Your drug doses must match your genetic metabolism profile

CYP2D6 poor metabolizer phenotype: codeine provides no pain relief; tramadol is ineffective; some antipsychotics and antidepressants accumulate to toxic levels requiring dose reduction. CYP2C19 poor metabolizers: clopidogrel (Plavix) activation is impaired, reducing antiplatelet effect and increasing stent thrombosis risk post-PCI; alternative P2Y12 inhibitors (prasugrel, ticagrelor) are preferred. CYP3A4 ultra-rapid metabolizers may require higher doses of many substrates. Phenotype results documented in the medical record and integrated into EHRs guide future prescribing, preventing dosing errors that cause therapeutic failure or life-threatening toxicity.

The antibiotic that doesn't work, the pain medication that's ineffective — not because the drugs are wrong, but because your genes are processing them at a different speed than the dose imagined.

Pharmacogenomics — Drug Response

Standard panels test 10-30 'star alleles' per gene. They miss novel and rare variants, particularly in under-represented populations.

Standard panels miss rare variants and structural variations

Your drug doses must match your genetic metabolism profile

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