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Pharmacogenomics

Pharmacogenomics (PGx), also sometimes called pharmacogenetics, is a relatively new area of research that looks at how a person’s genetic makeup influences how they react to medications according to the U.S. National Library of Medicine. It is a part of the field of precision medicine, which seeks to treat each patient individually, and combines pharmacology (the science of how drugs work) with genomics (the science of the human genome and its function) to develop effective, safe drugs and doses that will be tailored to a particular person’s genes.


Image is courtesy of sciencemag.org.


Factors Influencing Drug Response


The National Human Genome Research Institute states that many approved and widely available medications are “one size fits all,” but they do not function in the same way for everyone. It’s difficult to know who would benefit from a prescription, who won’t, and who will have negative side effects, which are called adverse drug reactions. In the United States, adverse drug reactions are a leading cause of hospitalizations and deaths. According to cancer.net, rugs work differently in different people due to several factors:


Many cancer drugs must be “turned on” in order to work. This process is called drug activation. Enzymes are proteins that help speed up the body’s chemical reactions, activating a drug so that it can perform its function. Enzyme variations are inherited, and they affect how quickly a drug transforms into its active form. For instance, some bodies take a long time to break down drugs.


To prevent the drug from being exposed to healthy tissues, drugs need to be “turned off”, which is known as drug deactivation. Some people have slower enzymes than others, thereby possibly experiencing more side effects from the drug.


Other than pharmacogenomics, factors including age and gender, the stage of cancer, lifestyle habits (such as smoking and alcohol consumption), certain diseases, and medications taken for other conditions may influence drug response.


Benefits of Pharmacogenomics


In a Journal of Clinical Medicine Research article on pharmacogenomics, there are many benefits that come with this area of research.


Better, safer drugs the first time


Every year, severe drug reactions result in more than 120,000 hospitalizations. Doctors would be able to analyze a patient’s genetic profile and prescribe the best possible drug treatment right from the start, rather than the standard trial-and-error process of matching patients with the right drugs. Pharmacogenomics not only has the potential to take the guesswork out of choosing the correct prescription, but it will also improve recovery time and safety by reducing the risk of adverse reactions.


Decrease in the overall cost of health care


Pharmacogenomics may improve healthcare costs. Reducing the number of adverse drug reactions, the number of failed drug trials, the time it takes to get a drug approved, the amount of time patients are on medication, the number of drugs patients must take to discover an effective therapy, the effects of a disease on the body (through early detection), and an increase in the spectrum of potential drug targets will contribute to a net decrease in the cost of health care.


Improvements in the drug discovery and approval process


Using genome targets, pharmaceutical companies may be able to find new drugs more quickly. If trials are designed for specific genetic population groups to have greater levels of success, the drug approval process would be improved. Clinical trials would be less expensive and risky if they only test people who are likely to react to a prescription.


Better vaccines


Vaccines made of genetic material, either DNA or RNA, provide all of the advantages of existing vaccines without complications. They will activate the immune system, but will not be able to infect people. They will also be low-cost, stable, easy to store, and capable of being engineered to carry several strains of a pathogen at once.


More powerful medicines


Pharmaceutical firms will be able to develop medicines based on the proteins, enzymes, and RNA molecules associated with genes and diseases, making drug development easier and allowing drug companies to create therapies that are more geared to specific diseases. This precision would optimize therapeutic benefits while minimizing damage to surrounding healthy cells as well.


Advanced screening for disease


Knowing one’s genetic code allows a person to make appropriate lifestyle and environmental changes at an early age in order to prevent or lessen the severity of a genetic disease. Similarly, knowing a person’s susceptibility to a particular disease offers careful monitoring, and medications may be introduced at the most appropriate stage to optimize their effectiveness.


More accurate methods of determining appropriate drug dosages


The current methods of basing dosages on weight and age will be substituted with dosages based on genetics, how long it takes to metabolize the medicine, and how well the body processes the drug, maximizing the therapy’s value while reducing the risk of overdosing.


Challenges


The following are some challenges in the development and practical use of pharmacogenomics, according to an article from the Journal of Clinical Medicine Research:

  • Expensive: It is costly, particularly if the expenses are not covered by insurance.

  • Limited access to testing: In certain places, access to some tests may be limited.

  • Limited drug alternatives: For the treatment of a specific condition, only one or two approved drugs may be available. Patients with gene variations that prevent them from taking these drugs could be left with no other alternatives for treatment.

  • Complexity of finding gene variations that affect drug response: Single nucleotide polymorphisms (SNPs) are sequence variations caused when a single nucleotide (A, T, C, or G) in the genome sequence is altered. Because SNPs occur every 100 to 300 bases along the human genome’s 3-billion-base length, millions of SNPs must be identified and analyzed to determine their role (if any) in drug response. Our limited knowledge of which genes are involved in each drug response further complicates the process. Given the large number of genes that are expected to affect responses, getting a big picture on the impact of gene variations is very time-consuming and complicated.

  • Privacy issues: Despite federal anti-discrimination laws, privacy concerns persist. Discrimination based on genetic information is prohibited by these laws.

  • Disincentives for drug companies to make multiple pharmacogenomic products: Many pharmaceutical companies have been successful with their “one size fit all” approach to drug production. Will these companies be able to develop new drugs that only benefit a small portion of the population, given that bringing a drug to market is very costly?


Current Research


Medline researchers are currently studying how inherited differences in genes impact the body’s response to drugs, along with the knowledge gained from the Human Genome Project. These genetic differences can be used to determine if a medication will be effective on a certain individual and help prevent adverse drug reactions. A person’s reaction to drugs is also affected by conditions such as clopidogrel resistance, warfarin resistance, warfarin sensitivity, malignant hyperthermia, Stevens-Johnson syndrome/toxic epidermal necrolysis, and thiopurine S-methyltransferase deficiency.



Article author: Tanya Kor

Article editors: Sherilyn Wen, Valerie Shirobokov