Pharmacogenomics

Assist. Prof. Dr.  Harith K. Buniya

 eps.harithkamil.buniya@uoanbar.edu.iq
The author's official website

      Pharmacogenomics (sometimes called pharmacogenetics) is a field of research that studies how a person’s genes affect how he or she responds to medications. Its long-term goal is to help doctors select the drugs and doses best suited for each person. It is part of the field of precision medicine, which aims to treat each patient individually. This field combines pharmacology (the science of drugs) and genomics (the study of genes and their functions) to develop effective, safe medications that can be prescribed based on a person’s genetic makeup.

     just as our genes determine our hair and eye color, they partly affect how our bodies respond to medicine. Genes are instructions, written in DNA, for building protein molecules. Different people can have different versions of the same gene. Each version has a slightly different DNA sequence. Some of these variants are common, and some are rare. And some affect health, such as those gene variants linked to certain diseases.

     Scientists know that certain proteins affect how drugs work. Pharmacogenomics looks at variations in genes for these proteins. Such proteins include liver enzymes that chemically change drugs. Sometimes chemical changes can make the drugs more—or less—active in the body. Even small differences in the genes for these liver enzymes can greatly impact a drug’s safety or effectiveness.

     Drug companies are also using pharmacogenomics to develop and market medicines for people with specific genetic profiles. By studying a drug only in people likely to benefit from it, drug companies might be able to speed up the drug’s development and maximize its therapeutic benefit. In addition, if scientists can identify genes that cause serious side effects, doctors could prescribe those drugs only to people who do not have those genes. This would allow some individuals to receive potentially lifesaving medicines that otherwise might be banned because they pose a risk for other people.

     Understanding pharmacogenomics would not be possible without sequencing the genomes of many people and comparing them, and then comparing their response to medicines. But we have also learned that a person's genome sequence is not everything when it comes to medication responses. The human body is a very complicated machine, and the instructions written in our DNA are just part of the process.

      There are some cases, as with the breast cancer treatment tamoxifen, where a small study showed that there might be a relationship between someone's response to the medicine and a variant in the CYP2D6 gene. However, this finding did not appear to be true in a larger study that involved many more people. That's why at this time, the U.S. Food and Drug Administration (FDA) labeling for tamoxifen does not recommend CYP2D6 pharmacogenomic testing, but the issue is still being reviewed as more research is conducted. One current use of pharmacogenomics involves people infected with the human immunodeficiency virus (HIV). Before prescribing the antiviral drug abacavir (Ziagen), doctors now routinely test HIV-infected patients for a genetic variant that makes them more likely to have a bad reaction to the drug.

    Currently, doctors prescribe drugs based mostly on factors such as a patient’s age, weight, sex, and liver and kidney function. For a few drugs, researchers have identified gene variants that affect how people respond. In these cases, doctors can select the best medication and dose for each patient.