Using genomics to improve drug prescribing

Laura Blackburn

4 April 2022


A recent joint report from the Royal College of Physicians and the British Pharmacological Society has outlined guidance, barriers and opportunities around the use of pharmacogenomics – using genomics to understand why some patients respond differently to medicines.

Why pharmacogenomics?

There are a number of genetic variants that could affect a person’s response to prescribed drugs, and every person is likely to carry at least one of these variants. They can influence how drugs are absorbed, distributed, processed, used, broken down and removed by the body. The impact that this has on patients can vary. In some cases, a genetic variant might mean a drug doesn’t work as well, or not at all. In other cases, a patient might experience an adverse drug reaction (ADR); it has been estimated that ADRs affect 10-20% of hospital patients and cost the NHS £530 million annually.

Genetic testing to ensure that patients are given the most effective drug for their condition, including drugs that don’t cause them harm, could benefit both patients and the health system through improving the patient experience and potentially reducing healthcare costs.

Some pharmacogenomic testing is already available on the NHS, to understand if breast and colorectal cancer patients can be safely prescribed the chemotherapy drug 5-fluorouracil – in England, this test is available via the Genomic Medicine Service. An NHS England pharmacogenetics test evaluation working group reviews evidence for the potential inclusion of new pharmacogentic tests in the National Genomic Medicine Test Directory.

The new report identified a number of barriers towards wider adoption of pharmacogenomic tests, including making the most of research evidence, poor availability of tests, health professional education and engagement, and making pharmacogenomic information readily available, for example through electronic systems.

Moving towards a precision medicine future

The implementation of pharmacogenomics is complex, and will require approaches that reach across clinical disciplines and different levels of the health system. The review’s recommendations consider these broad themes, and make proposals for tackling some of the challenges identified.

It is recognised that clinical implementation of pharmacogenomics can occur in a range of settings, including primary and secondary care, as well as specialised centres. They recommend implementation strategies that reduce health inequalities, both within and between the four nations of the UK.

One issue that has an important role to play in maintaining equality of access to testing is through commissioning services in a coordinated way throughout the UK, rather than at a local level, which could create a postcode lottery. The review also recommends the development of service standards – for example in turnaround times, technology use, and reporting of results – to help ensure consistency of service delivery. 

Another group of recommendations focus on education, training and support of healthcare professionals. There are a number of ways that this could be achieved, from updating teaching programmes in different specialities to workforce planning and the development of pharmacogenomics ‘consult services’ comprised of a multidisciplinary team that takes into account guidelines and prescribing information and provide peer support to clinical colleagues. The review also notes that there are 18 clinical specialties where there are opportunities for exploring the use of pharmacogenomics, examples include hypersensitivity reactions in allergy medicine and asthma treatment optimisation in respiratory medicine. 

What to do about data?

A key theme is the delivery of genetic testing and particularly the ongoing storage and accessibility of genomic information. The review highlights many important points that we need to think about in terms of ensuring that the health system makes best use of the results of pharmacogenomic testing. There are a number of different ways in which tests can be delivered – on a case-by-case basis or at a particular timepoint in a person’s lifespan. Would the health system want to put a system in place where patients have separate pharmacogenomic tests every time they might need one? Or, would it be more appropriate for a patient to have a more comprehensive test covering all known gene-drug pairs, including those relevant to their current care, which would provide information to be stored on their medical record for potential future use? How might we store this information, and who would have access to it? For example, GPs and pharmacists can play an important role in supporting prescribing practice, and would help to ensure that patients are given the correct drug at the correct dose, based on their pharmacogenomic profile.

Putting pharmacogenetics into practice

This review is important and timely, coming at a time when clinical genomics services in all four UK nations are growing and working to embed genomic testing into routine clinical practice. The time is undoubtedly right to support the further use of pharmacogenomic testing in the NHS, as evidence builds and as health systems further develop the skills and experience to deliver genomic and precision medicine for patient benefit.

The recommendations in this review are a useful step towards the goal of embedding pharmacogenomics into the NHS and empowering healthcare professionals to use them in their routine clinical practice. They are also in line with those of the 2018 PHG Foundation Personalised medicine technology landscape report for NHS England, which emphasised the importance of supporting the health workforce to incorporate pharmacogenetic testing through training and clear clinical guidelines alongside services and infrastructure to underpin good evidence-based practice.

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