Shutterstock.com
Testing patients for just three genes could help prevent three-quarters of avoidable side effects of certain medicines, study results have shown.
The study, published in PLoS Medicine on 27 March 2025, analysed more than 1.3 million adverse drug reaction (ADR) reports submitted to the Medicines and Healthcare products Regulatory Agency’s (MHRA) Yellow Card scheme.
The results showed that 115,789 ADR reports (9%) were associated with drugs for which side-effect risk could be modified using pharmacogenomics (PGx) information to guide prescribing.
Of the 115,789 ADR reports, 87,339 (75%) were associated with three genes that affect the way an individual processes medication: CYP2C19, CYP2D6 and SLCO1B1.
The type of medications that showed the highest volume of ADRs that could be prevented by personalising prescribing with genetic information were treatments for psychiatric disorders with 54,846 ADR reports (47%) and cardiovascular problems with 28,279 ADR reports (24%), respectively.
The study also found that patients who had ADRs that were able to be mitigated by PGx were more likely to be older males who experienced severe but non-fatal side effects.
Previous research has indicated that more than 99% of individuals have genetic variants which affect their response to certain drugs.
Study co-author Mark Caulfield, vice-principal for health at Queen Mary University of London (QMUL), said: “This is the largest analysis of the potential role of PGx in adverse reactions from a national spontaneous reporting system. It suggests that 9% of these reports may relate to our genetic make-up. This could be avoidable if we had measured the genetic make-up of the person before prescribing these medicines. It is time for the NHS to consider adopting pre-emptive testing for known genes that interact with medications.”
June Raine, chief executive of the MHRA, added: “This study shows how reports of suspected side effects to the Yellow Card scheme can help us better understand and prevent serious side effects, including those linked to genetic factors.
“This research also reinforces the importance of our pioneering Yellow Card Biobank with Genomics England, which will help us take a more personalised, proactive approach to patient safety and make medicines safer for everyone.”
Commenting on the study, David Wright, professor of health services research and head of the School of Healthcare at the University of Leicester, said: “This provides yet further evidence to support implementation of PGx testing into routine practice within the UK.
“Significant patient benefit can be derived from something which is now, due to advances in technology, relatively cheap and quick to implement. Whilst the NHS has the facilities for testing, policymakers seem slow to want to adopt it. This is a good example of using technology to improve patient care and reduce NHS costs in line with the government agenda. ADRs and therapeutic failure all increase workload, hospital admissions and represent preventable unnecessary use of resources.
“Given the pharmacist’s expertise in medicines, the use of PGx should become routine practice for the whole profession, thereby further locating us at the centre of patient care,” he added.
Osman Ali, chief pharmaceutical officer’s clinical fellow and PGx project lead at the Royal Pharmaceutical Society (RPS), said: “This important study highlights the potential of personalised medicines and the role of PGx testing in making prescribing safer, with fewer adverse effects and cost-effectively.
“All prescribers, including prescribing pharmacists will have a key role to play in supporting the integration of PGx testing into patient care, ensuring medicines are tailored to individual’s needs. This is why [the RPS is] working with the Pharmacogenomic and Medicines Optimisation Network of Excellence to develop a PGx prescribing competency resource for all prescribers.”
In February 2025, a survey conducted by QMUL found that almost 90% of people would agree to PGx testing to get the most effective medicine and reduce side effects. Respondents’ motivations for saying they would agree to a test included enhancing drug effectiveness (72%) and the reduction of ADR risk (63%).
Also in February 2025, the PROGRESS PGx trial, which initially ran in ten GP practices in the north west of England, began expanding across England.
The study — which began in June 2023 and is being led by the University of Manchester — is the first in the UK to introduce genetic testing before prescribing in primary care and will test the feasibility of rolling out PGx testing for patients taking statins, antidepressants and proton pump inhibitors.
Initial results from the early stage of the trial showed that 28% of participants received PGx recommendations that led to changes in their prescriptions.
