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Related Concept Videos

Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase01:11

Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase

Genetic polymorphisms in drug targets have emerged as critical determinants of interindividual variability in drug response and toxicity. Pharmacogenomic investigations increasingly focus on identifying these variations to personalize and optimize therapeutic interventions. A drug target may be a receptor, enzyme, or signaling protein involved in pharmacologic responses or disease-related pathways. While early pharmacogenetic studies focused primarily on drug metabolism, current research...
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu01:29

Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu

Genetic variations significantly influence drug response through pharmacokinetics, receptor interactions, and biologic milieu modifications. Pharmacokinetic alterations impact drug metabolism and clearance, affecting efficacy and toxicity. Variants in drug-metabolizing enzymes, such as CYP2C9 and CYP2C19, alter drug activation and elimination. For example, CYP2C9 loss-of-function variants require lower warfarin doses to prevent excessive bleeding, while CYP2C19 variants reduce clopidogrel...
Pharmacogenomics: Identification of New Drug Targets01:29

Pharmacogenomics: Identification of New Drug Targets

Advances in genomics have profoundly influenced drug discovery by increasing both the speed and accuracy of pharmaceutical development. Pharmacogenomics, which examines how genetic variation influences drug response, facilitates the identification of novel therapeutic targets and enables patient stratification for personalized treatment. These strategies contribute to improved drug efficacy, minimized adverse effects, and more efficient clinical trial design.Mapping genetic differences...
Therapeutic Drug Monitoring: Affecting Factors01:29

Therapeutic Drug Monitoring: Affecting Factors

Therapeutic Drug Monitoring (TDM) is the clinical practice of measuring specific drug levels in a patient's blood or body tissues to manage and optimize therapy. TDM is crucial for drugs with narrow therapeutic windows, like warfarin and phenytoin, where incorrect doses can lead to treatment failure or severe side effects. This monitoring ensures the dosage administered is within a safe and effective range. The factors affecting therapeutic drug monitoring include:Patient-Specific Factors:a.
Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase01:27

Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase

Phase II biotransformation reactions are essential for detoxifying and eliminating xenobiotics, including many pharmaceutical compounds. These reactions typically involve conjugation, the covalent attachment of polar endogenous groups such as glucuronic acid, sulfate, methyl, or acetyl moieties to functional groups introduced during Phase I metabolism. The resulting conjugates are more water-soluble, enabling efficient renal or biliary excretion.The major classes of Phase II enzymes include...
Pharmacogenetics of Drug Metabolism: Overview01:27

Pharmacogenetics of Drug Metabolism: Overview

Genetic polymorphism in drug metabolism is crucial to the inter-individual variability observed in drug responses. Drug metabolism primarily involves the chemical modification of drugs and other xenobiotics to enhance their elimination by increasing their polarity. Two main classes of enzymes mediate this biotransformation process: Phase I enzymes, primarily cytochrome P450s, catalyze oxidation and reduction reactions, while other enzymes, such as esterases, mediate hydrolysis, and Phase II...

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Related Experiment Video

Updated: Jun 21, 2026

Looking for Driver Pathways of Acquired Resistance to Targeted Therapy: Drug Resistant Subclone Generation and Sensitivity Restoring by Gene Knock-down
08:59

Looking for Driver Pathways of Acquired Resistance to Targeted Therapy: Drug Resistant Subclone Generation and Sensitivity Restoring by Gene Knock-down

Published on: December 11, 2017

Genotype-guided tamoxifen therapy: time to pause for reflection?

Timothy L Lash1, Ernst A Lien, Henrik Toft Sørensen

  • 1Department of Epidemiology, Boston University School of Public Health, Boston, MA 02118, USA. tlash@bu.edu

The Lancet. Oncology
|August 4, 2009
PubMed
Summary

Tamoxifen therapy for early breast cancer may not be affected by CYP2D6 gene variants. Current evidence suggests tamoxifen efficacy is maintained regardless of genetic variations, making CYP2D6 genotyping premature for treatment decisions.

Related Experiment Videos

Last Updated: Jun 21, 2026

Looking for Driver Pathways of Acquired Resistance to Targeted Therapy: Drug Resistant Subclone Generation and Sensitivity Restoring by Gene Knock-down
08:59

Looking for Driver Pathways of Acquired Resistance to Targeted Therapy: Drug Resistant Subclone Generation and Sensitivity Restoring by Gene Knock-down

Published on: December 11, 2017

Area of Science:

  • Pharmacogenomics
  • Oncology
  • Drug Metabolism

Background:

  • Tamoxifen is a key adjuvant therapy for estrogen-receptor-positive early breast cancer.
  • CYP2D6 genotype has been proposed as a predictor of tamoxifen response due to its role in metabolizing the drug.
  • Some studies suggest reduced tamoxifen efficacy in patients with non-functional CYP2D6 alleles.

Purpose of the Study:

  • To evaluate the association between CYP2D6 genotype and tamoxifen response in breast cancer patients.
  • To critically assess the evidence supporting CYP2D6 genotyping for predicting tamoxifen resistance.
  • To determine if CYP2D6 genotype influences breast cancer recurrence risk in patients treated with tamoxifen.

Main Methods:

  • Systematic review and critical analysis of existing epidemiological studies on CYP2D6 genotype and breast cancer recurrence.
  • Examination of dose-setting studies and clinical outcome data related to tamoxifen metabolism.
  • Assessment of in vitro receptor binding models for tamoxifen metabolites.

Main Results:

  • Evidence suggests tamoxifen and its metabolites achieve therapeutic concentrations irrespective of CYP2D6 inhibition.
  • Epidemiological studies show highly heterogeneous results regarding the association between CYP2D6 genotype and breast cancer recurrence.
  • No single study or subset of studies demonstrates superior reliability in predicting tamoxifen response based on CYP2D6 genotype.

Conclusions:

  • The association between CYP2D6 genotype and tamoxifen response in breast cancer is not definitively established.
  • The heterogeneity and limitations of current studies do not support routine CYP2D6 genotyping for guiding tamoxifen therapy.
  • Current evidence suggests that recommendations for CYP2D6 genotyping are premature and may not accurately predict tamoxifen efficacy or recurrence risk.