Personalised medicine – these words have been thrown around a lot recently in the world of science. If you haven’t already heard about it, chances are you will soon. But how can you “personalise” medicine, and what does this mean for the future of healthcare?

Firstly, some definitions. Personalised medicine is “the tailoring of medical treatment to the individual characteristics of each patient”, according to the Personalized Medicine Coalition. The NHS explores it through the “4 Ps”:

• Prediction and prevention of disease
• Precise diagnosis
• Personalised interventions
• Increased Participation from patients

These highlight not only the importance of empowering patients and identifying people who are at a higher risk of getting ill early, but also tailoring the diagnosis and treatment pathway to work effectively for them. For the most part, using the same therapies for everyone works well enough; as humans, broadly speaking, we are all very similar to each other.

However, it is becoming more and more apparent that individuals with the same diseases can have slightly different presentations, and patients taking the same drugs can respond in different ways. Alongside well-established characteristics, such as ethnicity and biological sex, genetics is playing an ever-increasingly important role in understanding the more subtle differences between individuals, which will allow us to further develop the personalisation of diagnosis and treatment.

“Angelina Jolie brought the BRCA1 gene into the spotlight when she had a double mastectomy”

Cancer is a field in which personalised medicine has already made its mark, perhaps reflecting the fact that cancer is inherently linked with dysfunction at the DNA level. Screening for potentially cancerous gene variants can allow patients to make decisions about their health. Angelina Jolie brought the BRCA1 gene into the spotlight when she had a double mastectomy after discovering that she had an 87% chance of developing breast cancer, despite not having actually developed the disease at the time.

BRCA1 is a gene involved in repairing our DNA if mistakes come about when it is being copied, so having a variant that doesn’t work as effectively can result in other genes becoming faulty as they lack this protection. Genes that could be affected include those that control the rate at which cells divide, increasing the risk of cancer. In these cases, people who have a strong family history of cancer are offered testing under screening programmes to see if they carry genetic variants that put them at a higher risk of also being affected, allowing them to make informed choices before symptoms start to show.

Personalised medicine can also play a significant role after diagnosis too. For instance, breast cancers are tested to see if they express certain receptors for the hormones oestrogen or progesterone, as well as the receptor HER2. If they do, patients are offered specific treatment which can include drugs that act on these receptors and reduce their activation. Patients who don’t have any of these specific markers (called triple-negative breast cancer) are usually offered chemotherapy instead. The testing of tumour cells allows for specific treatment to be delivered, offering better outcomes for the patient.

Aside from diagnostics, the up-and-coming field of “pharmacogenomics” is also benefiting from personalised medicine. Patients’ genetic makeups can be analysed before they start specific drugs, to make sure they will work well for them and that they will react safely to them. Warfarin, a drug used to thin the blood, can accumulate in dangerously high levels in some people who have a variant in the system responsible for clearing it from the body.

If patients are tested before starting treatment, they could be offered tailored dosing regimens to keep the level of the drug in their body safe. Adverse drug reactions cost the NHS, and so the taxpayer, a lot of money due to hospital admissions, with estimates of around £1 billion a year. Furthermore, commonly prescribed drugs, such as antidepressants, may only work in up to 50% of patients, highlighting the immense advantages that testing people before they start medications would bring to both patients’ lives and the healthcare system as a whole.

“Treatment options could be made much more targeted, rather than following a one-size-fits-all approach, offering both better outcomes with reduced side effects”

The future of personalised medicine is vast. Screening programmes could be expanded to help identify and follow-up more people who are at a higher risk of developing certain conditions, even if they don’t have any symptoms at present. Treatment options could be made much more targeted, rather than following a one-size-fits-all approach, offering both better outcomes with reduced side effects. This could even involve gene therapy to cure disease and reduce the number of future follow-ups, an example of which is Zolgensma, the most expensive drug to have been prescribed on the NHS (with a manufacturer’s list price of £1.79 million for a single course of treatment, although the NHS is said to have negotiated a “substantial” discount). It is used to treat a form of Spinal Muscular Atrophy, an often-fatal genetic disease that gradually causes paralysis in infants, who often have a life expectancy of just two years. Treatment with Zolgensma requires a single one-off infusion, which provides a copy of a missing gene to nerves. In turn, infants have been able to start breathing on their own, crawling, and walking, which they were not able to do previously. In a similar way, more conditions could be treated in the future, offering massive improvements in life expectancy and quality of life for people across the globe.

These advances will undoubtedly raise questions, especially in the field of ethics, ranging from concerns around data privacy, equity in access to expensive technologies, and decisions around reporting variants that only marginally increase the risk of disease. However, regardless, the way we access healthcare and the way the healthcare system will look after us is set to vary significantly over the coming years. Personalised medicine has already started to change different aspects of healthcare and will continue to do so in the future. The question is, what will that change look like?