Genomics 101: What is personalised medicine?

In this series, ‘Genomics 101’, we go back to basics and explore some of the most important topics in genomics. In this blog, we explain the term personalised medicine, and how it is transforming our healthcare.

First things first, what is personalised medicine?

Personalised medicine is about finding the right dose of the right medicine for each individual patient. It is the opposite approach to one size fits all.

Personalised medicine involves tailoring treatments to each individual person, based on what is likely to give them the best possible outcome with the least possible side effects.

As well as finding the right treatment, personalised medicine is also about improving the accuracy of diagnoses, predicting the likelihood that someone might develop a condition, and preventing it from getting worse.

How can we predict the best treatment?

Great question! This depends on various different factors, including the specific condition we are looking at.

A patient’s medical history can tell us how they have reacted to other medications, which can help to inform our future choices.

For example, some patients have problems with a type of medication called ‘anti-inflammatories,’ and other patients don’t. If we give anti-inflammatories to someone who has not responded well to them in the past, we are likely to get the same problems all over again.

Another way we can predict the best treatment is using genetic markers. These are specific sequences of DNA with a known location in the genome.

Using genetic markers in personalised medicine

When genetic markers and genes are next to each other in the genome, they tend to be inherited together.

This means that genetic markers can tell us information about a person’s genes and which genetic changes they have, including ones that might be affecting their health.

By analysing genetic markers alongside other clinical data, scientists can find patterns or variation in how people respond to medicines.

Therefore, we can predict which treatments an individual is likely to respond well to, according to the genetic markers they have.

Is personalised medicine changing cancer care?

More traditional approaches to treating cancer usually centre around the organ which the cancer first originated in. For example, approaches to ovarian cancer would be different than approaches to pancreatic cancer, because they both arise in different organs.

However, as we learn more about the genetic changes that cause cancer, cancer treatments are more frequently based on the genetic change that drives the cancer, instead of the specific organ.

We now know that some medications which were only being used to treat specific cancers are actually useful across several cancers that are driven by the same genetic mutation.

And what about genetic conditions?

For many common genetic conditions, we have a good understanding of which genetic changes might cause people to have bad responses to certain drugs.

We call these responses ‘adverse drug reactions’, and you can learn more about them in our previous podcast ‘Can genomic testing prevent adverse drug reactions?’.

By using genetic testing, we can predict who will get these adverse drug reactions and use treatment approaches to avoid them.

Similarly, we also know about genetic changes that can influence how people’s bodies process or ‘metabolise’ different drugs, which helps us to decide which dose to give.

So, how far away is personalised medicine from routine clinical care?

Personalised medicine is already being used in clinical care, though it is only used as the standard procedure in a small number of settings.

For example, DPYD testing is a widely used test which predicts someone’s response to a group of chemotherapy agents called ‘fluoropyrimidines’.

Some people have very low levels of an enzyme called ‘DPD’, and these people are likely to have very serious, life-threatening reactions to fluoropyrimidine chemotherapy agents.

DPYD tests have proven very successful in identifying patients with low DPD enzyme, and preventing adverse drug reactions.

What is the future of personalised medicine?

The goal of personalised medicine is to achieve the best outcome for patients by moving away from ‘one size fits all’ and towards tailoring treatments for specific individuals.

Pre-emptive testing is a large part of this, which means testing people in advance of them needing medications.

This means that when they see a doctor about a particular condition, the doctor already has the patient’s genetic information and can know if a medication is safe for them, as well as the best dose to give.