Individuality and personalization are on the rise in most aspects of society. Why then do we group everyone together when it comes to medication? With broad-spectrum antibiotics proving to be less effective against bacterial infections than ever before, medicine is moving towards a more individual approach of treatment.

Personalized medicine tailors therapies to groups of individuals based on their predicted response or risk of a disease, which is dependent on their genome. Indeed, an individual’s risk of disease is contingent on both their genetic predisposition as well as environmental factors, and how these two may interact. Once an individual acquires a disease, these two factors continue to play a role in how that person may respond to the treatment. This idea of personalized medicine is not new, in fact it dates back to the 1960s. However recent advances in technology and diagnostic tools have allowed us to take the theory to reality.

This idea of personalized medicine is not new, in fact it dates back to the 1960s.

There is huge variation in the human genome. Genetic variation contributes to both an individual’s risk of getting a disease and also with how they may respond to the treatment. Each individual’s genome can therefore impact the way different individuals respond to or react to drugs. Personalized medicine is used for a number of reasons: to determine the optimal drug, and optimal drug dosage for subgroups of patients, or whether targeted treatment options are available for individuals.

This is seen in a variety of situations. For example, cystic fibrosis is caused by a mutation in a specific protein found in cell membranes. The genetic mutation impairs the function of that protein causing the symptoms like mucus accumulation and chronic pulmonary infections. However, different genetic mutations can lead to the same disease with varying severity. This discovery led to the development of drugs that target the specific gene that is affected. By knowing the genetic makeup of an individual with cystic fibrosis, we can therefore determine which medication will work most effectively and efficiently for that individual.

By knowing the genetic makeup of an individual with cystic fibrosis, we can therefore determine which medication will work most effectively and efficiently for that individual.

However, this concept can also be broadened to include the idea of withholding treatments. In prostate cancer for example, DNA biomarker tests can be used in order to determine whether treatments can be delayed, therefore sparing patients from the debilitating side effects of prostate cancer therapies. If the genes that normally cause aggressive forms of the cancer are not found, that can indicate that the cancer will remain stable for decades and so invasive treatments can be avoided.

Biological markers, or “biomarkers”, are a staple in the personalized medicine world. Biomarkers have been defined as “any substance or biological structure that can be measured in the human body and may influence, explain or predict the incidence or outcome of a disease”. It is a marker that can be objectively measured and can indicate normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic intervention.

Biomarkers are often used in order to test the susceptibility that someone has for cancer as well as how they may respond to various chemotherapies. In some cases, biomarkers can determine a specific mutation that has a targeted therapy associated with it. For example, certain aggressive breast cancers have a mutation in the HER-2 gene. Those with that mutation will have different treatments options available to them than a patient with breast cancer who does not have that mutation. Similarly, in melanoma, an aggressive cancer of the skin, the individual can have a mutation called BRAF, which is present in approximately half of those affected with the disease. There are therapies that target the specific BRAF mutation and can stop the cancer from growing. By testing for the mutation, we can therefore improve the outcomes of those patients.

Although cancer is one of the main focuses of personalized medicine, it expands beyond that.

Although cancer is one of the main focuses of personalized medicine, it expands beyond that. Statins are a common class of cardiovascular medications that are used to lower cholesterol. Four of five adults in Ireland have high cholesterol, and it is a main cause of heart related disease. Although statin treatments can be very effective, there are large variations to the response to statins, where nearly half of those who are prescribed the medication do not reach their cholesterol level goals. This is due to the variation in genes, bringing us to the same theme that because of variation in our genes, some individuals respond differently to the same medication. Not only is statin treatment not effective for everyone, but also in some cases these medications can cause muscle toxicity, which can be potentially life-threatening. Predictive screening may therefore be recommended for patients receiving statin treatments for high cholesterol.

Personalized medicine is the way of the future. But, it is not always so simple. Firstly, a large population sample is needed to determine different genetic variations within a population and how these correlate with disease outcomes as well as response to treatment. It is therefore difficult to find biomarkers that can be used for diagnostic and therapeutic purposes. Genome-wide association studies allow the genetic makeup of an individual to be cross-referenced with that of the human genome sequence. However, these studies don’t always give an accurate description of the individual’s genes and are therefore not always predictive. When more biomarkers are discovered and gene sequencing becomes more effective, personalized medicine will improve treatment efficacy and reduce toxicity and improve the lives of patients across diseases.