Fewer side effects of medication through DNA testing

Patients whose drug treatment is matched to their DNA, suffer 30 percent fewer serious side effects. This is the result from a study published by a team of international researchers, including Vera Deneer, associate professor of clinical pharmacology at the Utrecht Institute of Pharmaceutical Sciences (UIPS) and her colleague Heshu Abdullah-Koolmees, in The Lancet. This is the first publication worldwide, to show that prescribing drugs based on a patient's DNA profile works in practice. The project was coordinated by the LUMC.

The effects of drugs on patients differ, because they have different genetic profiles. Variations in certain genes determine, for example, the enzyme activity and the rate at which the body converts the drug into other substances. Customized treatment therefore, means that the dosage of the drug, or the type of drug, is tailored entirely to the patient's genetic profile.

The study is an important first step toward prescribing tailored treatment, with fewer side effects for individual patients

The national, multidisciplinary pharmacogenetics working group "Dutch Pharmacogenetics Working group" (DPWG), which Vera Deneer chairs, develops so-called pharmacogenetics recommendations. For example, on drug dosages for patients with a specific genetic profile. Vera Deneer: "In the study, doctors and pharmacists took these recommendations into account when prescribing drugs and performing medication monitoring. In doing so, we were able to examine the effect of the advice. The results showed that there were fewer serious side effects, just like we hoped."

Vera Deneer
Vera Deneer

The study

Nearly 7,000 patients in seven European countries participated in the study. Currently, it is common practice within patient care to test patients for genetic variations in a single gene before or shortly after starting treatment with a specific drug. In the study, however, a comprehensive genetic profile that tested for twelve genes and approximately fifty genetic variations was established. Before the study began, physicians, pharmacists and others were trained in the field of pharmacogenetics. Patients within oncology, cardiology, psychiatry, as well as family medicine, were tested at the initiation of one of nearly forty drugs.

Doctors, pharmacists and patients received the results and recommendations via a pass that could be scanned, or via the electronic healthcare system. This way, they knew which dosage or drug best suited the patient's genetic profile. Up to twelve weeks after initiation, a nurse specialist contacted the patients to ask about their side effects. This tailored treatment was compared with standard treatment, in which the genetic profile wasn’t mapped.


The study showed that it is possible in practice to map the genetic profile for multiple genes at the start of a drug treatment, and adjust treatment accordingly. Vera Deneer: "The study is an important first step toward prescribing tailored treatment, with fewer side effects for individual patients."

The research was conducted with funding from the European Commission within the Horizon 2020 program (no. 668353).