CYP3A4 rs2740574: What Your Genotype Means
The rs2740574 variant is a well-studied genetic marker located in the promoter region of the CYP3A4 gene. It is widely recognized in scientific literature as the defining polymorphism for the CYP3A4*1B allele, which has been investigated for its potential influence on drug metabolism and disease risk.
What each genotype means
Normal enzyme activity
This genotype represents the most common form of the CYP3A4 promoter region. Research into the functional impact of this variant remains controversial, and environmental factors often play a larger role in enzyme activity than this specific genotype. You should discuss any concerns regarding medication metabolism with your clinician or pharmacist.
This is the most common genotype across all global populations.
CYP3A4*1B carrier
You carry one copy of the CYP3A4*1B allele, also known as the -392G variant. While some studies have investigated its association with drug metabolism and disease risk, the clinical significance remains debated and inconsistent across research findings. Please consult your healthcare provider or pharmacist regarding how your genetic profile might relate to your specific medications.
Carried by approximately 2-9% of individuals of European ancestry, with significantly higher frequencies observed in populations of African descent.
CYP3A4*1B homozygote
You carry two copies of the CYP3A4*1B allele. Some research has suggested an association between this genotype and an increased risk for certain cancers, such as prostate or ovarian cancer, though these findings are not universally confirmed. Because the functional impact on drug metabolism is still a subject of scientific debate, please discuss any medication-related questions with your clinician or pharmacist.
This genotype is rare in European populations but occurs at higher frequencies in individuals of African ancestry.
Understanding the rs2740574 Variant
The rs2740574 variant is a single nucleotide polymorphism (SNP) situated on chromosome 7 within the CYP3A4 gene. Specifically, it is a transition where an adenine (A) is replaced by a guanine (G) in the 5'-flanking region of the gene. Because this change occurs in the promoter region—the area responsible for controlling how much of a gene's product is made—researchers have long hypothesized that it could influence the expression levels of the CYP3A4 enzyme. In the scientific community, this specific variant is famously known as the defining marker for the CYP3A4*1B allele. While many genetic variants are rare, rs2740574 is considered common, though its frequency varies significantly depending on a person's ancestral background. It serves as a primary example of how non-coding genetic changes can become central subjects in pharmacogenomic studies.
The Role of the CYP3A4 Gene
The CYP3A4 gene provides instructions for creating the cytochrome P450 3A4 enzyme. This enzyme is a workhorse of the human body, responsible for metabolizing approximately one-third of all clinically used medications, as well as various endogenous substances like steroid hormones. Because it processes such a vast array of drugs—including those for blood pressure, cholesterol, and immune suppression—the activity level of this enzyme can significantly impact how a person responds to medical treatments. Variations in the CYP3A4 gene are of great interest to pharmacogenomics, the field that studies how genes affect drug response. While the enzyme's function is critical, it is important to note that the relationship between specific genetic variants and actual clinical drug metabolism is complex and often influenced by other environmental and genetic factors.
Research Associations and Evidence
Research into rs2740574 has explored its potential links to various health outcomes, including cancer risk and drug metabolism. Some studies have investigated whether the G allele is associated with an increased risk for certain conditions, such as prostate or ovarian cancer, due to the enzyme's role in hormone metabolism. However, the evidence regarding its functional impact on drug metabolism remains mixed. While some early studies suggested that the *1B allele might alter enzyme activity, other research has not consistently linked it to significant changes in how the body clears specific medications. Because of these conflicting findings, the clinical utility of testing for this specific SNP is currently limited. It is not typically used as a standalone diagnostic tool for medication dosing. Any questions regarding how your genetic profile might influence your response to a specific medication should always be discussed with your healthcare provider or a clinical pharmacist.
Population Frequency
The frequency of the rs2740574 variant differs markedly across global populations. It is found at much higher frequencies in individuals of African descent compared to those of European or East Asian ancestry. For instance, in some African-American populations, the G allele frequency has been reported to be quite high, whereas it is significantly less common in European populations and nearly absent in some East Asian groups. These differences highlight the importance of considering ancestral diversity when interpreting genetic data. Because the variant is common in some groups and rare in others, it serves as a reminder that genetic research must be inclusive to ensure that findings are applicable to all people. Understanding these population-level differences is a key component of modern genomic science.
What This Information Means for You
If you have received results regarding your rs2740574 genotype, it is important to view this information in the proper context. This SNP is a subject of ongoing scientific research rather than a definitive clinical diagnostic marker. Having a particular genotype does not mean you will experience a specific health outcome or a specific reaction to a medication. Many factors, including diet, lifestyle, other medications, and the rest of your genetic makeup, play a much larger role in your overall health and drug response. You cannot use this information to self-diagnose or make changes to your prescribed treatments. If you are concerned about how your genetics might affect your health or your response to a medication, the best course of action is to consult with a qualified clinician. They can help you interpret your results within the context of your full medical history and current clinical guidelines.
How common is this variant?
The rs2740574 variant is common, with allele frequencies ranging from nearly 0% in some East Asian populations to over 40% in African-American populations.
Frequently asked questions
Is rs2740574 used to determine drug dosage?
No, rs2740574 is not currently used in standard clinical practice to determine drug dosages. While it is a subject of pharmacogenomic research, it is not a primary marker in established clinical guidelines for medication management.
Does the G allele mean I have a higher risk of cancer?
Some research studies have explored associations between the G allele and certain cancers, but these findings are not definitive. Genetic risk is complex, and having a specific genotype does not guarantee a health outcome.
Should I get tested for CYP3A4 variants?
Genetic testing for CYP3A4 variants is generally not recommended for the general public. If you have concerns about how you respond to medications, speak with your doctor about whether clinical pharmacogenetic testing is appropriate for your specific situation.
What is the difference between rs2740574 and CYP3A4*1B?
They are essentially the same in this context; rs2740574 is the specific SNP identifier (rsID) used in databases, while CYP3A4*1B is the name of the star-allele defined by that specific genetic change.
Sources & further reading
Educational information only, last refreshed 10/5/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This variant is highly prevalent in populations of African and indigenous descent and is linked to increased rivaroxaban exposure and potential bleeding risk.
The CYP3A4*18 variant is significantly associated with the risk of anti-tuberculosis drug-induced hepatotoxicity, with effects modulated by pre-existing liver disease status.
Intronic CYP3A4 variant (CYP3A4*1G) associated with altered enzyme expression and clinical response to various medications including tacrolimus and statins.
CYP3A4 regulatory variant influencing transcription levels and downstream drug metabolism for various antineoplastics and immunosuppressants.
This variant defines the CYP3A4*20 allele, which is associated with a loss of function in the metabolism of various clinically important drugs.
The defining SNP for the CYP3A4*22 allele, which leads to significantly reduced metabolism of statins and immunosuppressants.