Genes tested in pharmacogenetics
Genes serve as the instructions our bodies use to develop, grow and function throughout our life. In pharmacogenetics (PGx), genes are tested for their association with predicted medication response. Most genes analyzed in PGx testing provide instructions for enzymes. Enzymes are proteins in the body that help process medications by either activating them or breaking them down (metabolizing them). Genetic variations found in these genes can affect how quickly or slowly an individual processes a medication, influencing the medication’s effectiveness and potential side effects.
What is CYP3A5?
CYP3A5 is a gene that provides instructions to make the CYP3A5 enzyme, which is involved in the breakdown (metabolism) of medications within the body. This enzyme is mainly found in the liver and intestines, where certain medications are processed, affecting how well they work and how long they stay in the body.
PGx testing of CYP3A5
Genetic variation—the natural differences in DNA sequences between individuals—can affect how different people process the same medication. Because of specific genetic variation, the CYP3A5 enzyme may work differently from person to person.
The results of CYP3A5 PGx testing can predict how quickly or slowly your child is able to metabolize tacrolimus, which can help their health-care team choose or adjust their medication and dosage.
Medications affected by CYP3A5
Currently, there is one medication affected by genetic variation in CYP3A5. If your child’s enzyme is predicted to work slower or faster than most individuals, it may affect how this medication works:
- Tacrolimus, an immunosuppressant that helps prevent organ rejection after transplants
The medications listed above are referred to by their generic names. You may hear your child’s medication called by a different brand name. Generic medicines and brand-name medicines share the same active ingredient and offer the same performance, safety and effectiveness. This medication list is also subject to change with increasing research on the CYP3A5 enzyme.
CYP3A5 gene expression statuses
The results of a genetic test of CYP3A5 are sorted into expression statuses based on the predicted function of the enzyme:
- CYP3A5 expresser – the instructions for the enzyme are “turned on”, which means the CYP3A5 enzyme is being made in the body, breaking down medication faster than the average population.
- CYP3A5 non-expresser – the instructions for the enzyme are “turned off”, which means the CYP3A5 enzyme is not being made in the body. Without active CYP3A5 enzymes, the body breaks down medication at the expected rate.
These statuses are not an indicator of your child’s health—they simply predict whether your child might need a different dose of medication or a different medication entirely. In addition to PGx test results, your child’s health-care team will still consider medical history and other factors to ensure the best treatment for your child.
To learn more about drug metabolism, metabolizing enzymes and gene expression statuses, see Genetics basics for pharmacogenetics.
Why is my child’s PGx status important?
CYP3A5 is an enzyme that helps break down certain medications in the body. You can think of it like a drain in a pool that controls how quickly water flows out. The water represents medication.
- If the drain is slow, water builds up.
- If the drain is too fast, water runs out quickly.
Similarly, if your child’s CYP3A5 enzyme is faster than average at breaking down certain medication (expressed), the medication might leave the body before it can work properly.