Have you ever taken a painkiller that did absolutely nothing, while your friend swears by it? Or found that a medication left you foggy-headed, while others felt completely fine? It turns out, this may not be down to bad luck or overthinking –  it could be your DNA.

The emerging field of pharmacogenomics studies how our genetic make-up influences our individual responses to different drugs.

Since the sequencing of the human genome in the dawn of the 21st century, scientists have been unravelling the complex interplay between genes and drug responses. While conventional medicine often takes a one-size-fits-all approach, pharmacogenomics is challenging this view, asking: what if the key to a safer, more effective treatment lies within your unique genetic code? It suggests that many medicines work differently in different people depending on a handful of ‘pharmacogenes’.

“Conventional medicine often takes a one-size-fits-all approach”

Pharmacogenes primarily refer to genes involved in drug metabolism, transport, targets and the immune response. It has been shown, in some extreme examples, that just a single DNA variant can transform a drug from being highly effective to life-threatening. Warfarin is a common anticoagulant medication which reduces the formation of blood clots, decreasing the risk of stroke and thrombosis. Some individuals carry mutations which lower the body’s production of the enzyme which warfarin targets, meaning that a standard dose could inhibit it too strongly and thereby increase the risk of dangerous bleeding. Complicating matters further, warfarin is rendered inactive by certain enzymes. If an individual carries a mutation causing one of these enzymes to function improperly, their body breaks down the drug more slowly, causing potentially toxic build ups.

A landmark UK study involving over 600,000 patients found that 58% were prescribed drugs affected by pharmacogenes in just one year. In an analysis of 14 specific pharmacogenes using data from the UKBiobank, it was found that 24% of individuals have been prescribed a drug for which they are predicted to have an atypical response. This highlights pharmacogenomics as a pressing issue for public health.

“Your NHS app could suggest prescriptions personalised to your genetic make-up”

And it’s not just about safety. Precision medicine can also boost efficacy of drug action. Take setmelanotide (Imcivree), a drug recently approved to treat rare genetic forms of obesity. It only works in patients with loss-of-function variants in specific genes. In this case, prescribing based on genotype isn’t just helpful – it’s the difference between hope and futility.

One of the most fascinating frontiers lies in cancer treatment. Here, somatic mutations – those acquired throughout life rather than inherited – can be directly targeted by drugs. In many cases cancerous cells mutate in a way which confers resistance to anti-cancer therapies. Understanding the genetic profile of the cancer cells can help doctors to prescribe drugs which will show good efficacy against the patient’s unique tumour, demonstrating the power of personalised medicine approaches.

Pharmacogenomics is beginning to appear in the world of start-ups, with companies such as Geneticure developing patented DNA swab tests which recommend personalised treatment plans, for example to optimally lower blood pressure. Critics, however, caution that without clinical oversight this could lead to misuse of medications and that genetic screening often comes with patient compliance issues.

The direction of medicine is shifting from standard protocols to personalised care, guided by an understanding of patient genetics. Challenges, however, still remain, especially in ensuring diverse representation in genetic studies and improving data interpretation. There are often key genetic differences between distinct ethnic populations which will ultimately affect the translation of pharmacogenetics in different patient groups. It’s therefore important to ensure these subgroups are appropriately represented in clinical trials to maximise the application of pharmacogenetics in therapeutic contexts.

Moving forward, your genetic profile could be just as important as your medical history when it comes to choosing the right medication. Imagine a future where your NHS app could suggest ideal prescriptions personalised to your unique genetic make-up. As research continues to uncover how pharmacogenes shape drug interactions, it’s clear that this approach has the potential to transform healthcare.