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Genetic variation in CYP3A43 explains racial difference in olanzapine clearance
K L Bigos1, R R Bies, B G Pollock
1Genes, Cognition, and Psychosis Program, National Institute of Mental Health, NIH, Bethesda, MD, USA.
Molecular Psychiatry
|April 27, 2011
Summary
A genetic variation in CYP3A43 significantly impacts olanzapine clearance, affecting drug efficacy and discontinuation. Blood level monitoring is recommended for personalized antipsychotic treatment.
Area of Science:
- Pharmacogenomics
- Clinical Pharmacology
- Genetics
Background:
- Olanzapine, a widely used antipsychotic, has high discontinuation rates due to inefficacy and adverse effects.
- Genetic factors are known to influence drug metabolism and response, but specific mechanisms for olanzapine variability remain incompletely understood.
Purpose of the Study:
- To identify genetic predictors of olanzapine clearance and clinical response.
- To investigate the role of cytochrome P450 3A43 (CYP3A43) genetic variation in olanzapine pharmacokinetics and treatment outcomes.
Main Methods:
- Analysis of a single nucleotide polymorphism (rs472660) in the CYP3A43 gene within the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) trial.
- Correlation of CYP3A43 genotype with olanzapine clearance, blood levels, and clinical response measures.
- Examination of the influence of race on olanzapine clearance before and after accounting for CYP3A43 genotype.
Main Results:
- The CYP3A43 polymorphism (rs472660) strongly predicted olanzapine clearance (P=5.9e(-7)).
- Individuals with the high clearance genotype (AA) had trough blood levels below the therapeutic range at standard doses.
- The A allele frequency was significantly higher in African Americans (67%) than Caucasians (14%), and CYP3A43 genotype, not race, predicted clearance.
- Higher olanzapine clearance was associated with increased symptom ratings and higher discontinuation rates due to inadequate response.
Conclusions:
- CYP3A43 genotype is a significant genetic determinant of olanzapine clearance and response.
- Race is not an independent predictor of olanzapine clearance when CYP3A43 genotype is considered.
- Therapeutic drug monitoring of olanzapine blood levels is advisable to optimize treatment efficacy and minimize discontinuation.
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