Chapter 9: Pharmacogenomics (PGx): CPIC Guidelines & Drug-Gene Pairs
Chapter 9: Pharmacogenomics (PGx): CPIC Guidelines & Drug-Gene Pairs
Adverse drug reactions (ADRs) are among the leading causes of morbidity in clinical medicine. Pharmacogenomics (PGx) studies how inherited genetic variations in drug-metabolizing enzymes, drug transporters, and pharmacological targets alter drug efficacy and toxicity.
Metabolizer Phenotype Classifications
- Poor Metabolizer (PM): Markedly reduced or absent enzyme activity. Standard drug doses lead to toxic accumulation or lack of activation for prodrugs.
- Intermediate Metabolizer (IM): Reduced activity.
- Normal Metabolizer (NM): Wild-type standard metabolic rate.
- Ultrarapid Metabolizer (UM): Gene duplication or promoter hyper-induction causing rapid drug clearance or rapid prodrug overdose.
1. High-Impact CPIC Drug-Gene Clinical Pairs
# Canonical Clinical Pharmacogenomics Guidelines:
# -------------------------------------------------------------------------------------------------
# Gene Drug Mechanism / Indication Clinical PGx Consequence
# -------------------------------------------------------------------------------------------------
# CYP2C19 Clopidogrel Antiplatelet prodrug PMs fail to activate prodrug (high stent thrombosis)
# CYP2D6 Codeine / Tramadol Opioid prodrug (morphine conversion) UMs suffer fatal respiratory depression
# TPMT/NUDT15 6-Mercaptopurine Acute lymphoblastic leukemia PMs suffer fatal myelosuppression (reduce dose 90%)
# DPYD 5-Fluorouracil Colorectal chemotherapy Deficient patients suffer severe neutropenia/death
# VKORC1 Warfarin Anticoagulant dosing Hypersensitive variants require reduced dosing
# HLA-B*57:01 Abacavir HIV Antiretroviral Severe, potentially fatal hypersensitivity reaction
# -------------------------------------------------------------------------------------------------2. Star-Allele Calling with PyPGx
# Calling star-alleles and metabolizer phenotypes from patient VCF
pypgx run-ngs-pipeline \\
--gene CYP2D6 \\
--vcf patient_targeted.vcf.gz \\
--assembly GRCh38 \\
--out-dir ./pgx_results/
# Example output:
# Diplotype: *1/*4 (Intermediate Metabolizer) -> Recommendation: Consider alternative analgesic.