C/CTwo copies of *3. The variant creates a splice site that should not be there, so the protein made from it is truncated and does not work. This is a CYP3A5 non-expresser, and it is the majority genotype in people of European and East Asian ancestry — which is why the standard tacrolimus starting dose is the one that suits this genotype. Nothing here needs adjusting.
C/TOne functional copy and one *3. Still an expresser — a single working copy is enough to produce the enzyme — and the same increased tacrolimus starting dose applies. The most common way to be an expresser in a population where *3 is frequent.
T/TTwo copies of *1, the functional allele. This is a CYP3A5 expresser: the enzyme is made and works. For tacrolimus after a transplant, an expresser typically needs about 1.5 to 2 times the standard starting dose to reach the same blood level, and CPIC recommends starting higher rather than discovering it through repeated low readings. This genotype is the majority in much of sub-Saharan Africa and uncommon in Europe.
This affects the dose needed, not the target. The blood level a transplant team aims for is the same whatever the genotype; what differs is how much drug it takes to get there. Dosing after a transplant is measured directly and adjusted by the team, and nothing in a raw data file should change a dose without them.
Clinical pharmacology and therapeutics · 2015 · PMID 25801146
Questions about rs776746
What is rs776746?
rs776746 is a single position in the genome, in or near the CYP3A5 gene. Published research associates it with cyp3a5 expression (*3 allele). A single variant does not decide an outcome — it shifts a probability, and for most common variants the shift is small.
What conditions is rs776746 linked to?
On MyGeneLog this position is linked to CYP3A5 Metaboliser Status. The research behind each link, and its sources, are set out on that condition page.
Does rs776746 affect how medicines work?
CYP3A5 carries pharmacogenomic findings for Tacrolimus. That is educational information, not a prescription or a dosing guide. Any decision to start, stop or change a medicine belongs with the clinician or pharmacist managing your treatment.
Does having rs776746 mean I will get this?
No. Common variants like this one move a probability slightly and, on their own, rarely decide anything about one person. Nothing on this page is a diagnosis, and health decisions should be made with a clinician who can see your whole picture.
Where does the information about rs776746 come from?
CPIC Guideline for CYP3A5 Genotype and Tacrolimus Dosing (Clin Pharmacol Ther 2015, PMID 25801146). Every variant on MyGeneLog comes from public primary sources and is published with its citation and the date it was checked.