Pharmacogenomics study shows link between testing and better health outcomes

Pharmacogenomics is a relatively new branch of genetic testing that examines the impact a person’s genetic makeup might have on the way they metabolize drugs. Such testing is usually done in an effort to get patients on the right drugs sooner, hopefully eliminating the side effects that lead to non-compliance with prescribed therapies.

The study of pharmacogenomics has garnered a fair bit of attention in benefits circles over the last couple of years, says Ned Pojskic, leader of pharmacy and health provider relations with Green Shield Canada (GSC), with the discussion evolving of late, as more plan sponsors become interested in the possible value pharmacogenomics could bring to private pension plans.

Very little unbiased evidence

An effort to study this value, however, is not without its challenges.

To date, experts say there is very little unbiased evidence about the impact a pharmacongenomics test might have on patient outcomes. Pojskic says the link between genetic mutuations and the response or metabolization of drugs is well-established. The question, he adds, is whether knowing a patient’s genetic predisposition will actually matter when it comes to health outcomes.

Despite claims, often claims made by those who’ve confused pharmacogenomics with other branches of genetic testing (not to be confused with newborn congenital testing, disease diagnosis, or predictive testing, pharmacogenomics is specifically focused on the relationship between drug metabolization and a person’s genetic makeup), Pojskic says the notion that pharmacogenomics will save plans money, is probably premature.

“I think a lot has been made by folks who, quite frankly, in the Canadian space, have hyped up pharmacogenomics without really understanding it,” he told those gathered for the virtual Canadian Pension and Benefits Institute Forum 2020 conference. “They are not backed by evidence.” He adds that a lot of the pharmacogenomics-related trials being conducted today are often eight weeks long – not long enough to actually see the impact drugs and drug screening might have on a patient with depression, for example.

Filling in the knowledge gaps

To fill in the knowledge gaps, Green Shield Canada and HBM+, studied 213 Toronto-area patients for six months – a long trial design, comparatively speaking. In the study, all patients were assigned to either a control group where patients received standard care from their pharmacists and physicians, and a treatment group, where the physicians and pharmacists were also guided by the results of the patient’s pharmacogenomic test results.

Not only were the results “absolutely fascinating” they have also garnered international interest and attention: Patients who were tested and who received therapy that was optimized based on their pharmacogenomics test results did far better in the long run than those who did not have access to their pharmacogenomics test results.

“The question we were trying to answer was if clinicians are provided access to pharmacogenomic test results during routine clinical care, would patient outcomes improve?” - Ned Pojskic

When a patient is tested, they can be found to be a poor metabolizer of a certain drug, a normal metabolizer or an ultra-rapid metabolizer of the medicines they are being prescribed. (Being a rapid metabolizer of one drug does not mean the patient will rapidly metabolize all drugs.) Pojskic says there are over 200 different medicines – many depression drugs and cholesterol-lowering drugs among them – which have a genetic component to them.

Without genetic testing, choosing the right depression medication, for example, can simply be a case of trying different drugs until patients and physicians settle on something that works. “You are constantly cycling through, and the patient is often fatigued by the process, fatigued by the side-effects, losing patience in the process and losing confidence” they will get better, he says. “The question we were trying to answer was if clinicians are provided access to pharmacogenomic test results during routine clinical care, would patient outcomes improve?”

Between one and eight per cent of patients are poor metabolizers

“We do know that between one and eight per cent of patients are poor metabolizers (meaning their bodies do not process or clear drugs from their systems as effectively, often leading to adverse side effects). Somewhere between one and two per cent are ultra-rapid metabolizers. These are the patients we ultimately want to find.”

The study found, over six months, that patients in the control group did improve, as you might expect. “These patients are being treated by drugs. They are being treated by the pharmacist who is taking good care of them, and they are being treated by their physician. Naturally, you do expect them to improve,” Pojskic says. Almost immediately, however, less than a month into the trial, the intervention group started to do better than the control group. By month six, Pojskic says that difference was pronounced.

Using psychiatric instruments including the Patient Health Questionnaire, the Generalized Anxiety Disorder Scale, and the Sheehan Disability Scale to measure patient outcomes, the study revealed that those in the pharmacogenomics-guided group reported significantly greater improvements over the six-month period. Patients being treated for depression showed a 36 per cent improvement over their baseline scores in the pharmacogenomics-guided group, and an 18 per cent improvement in the control group. “Similarly, the outcomes for anxiety and disability were around two times greater in the pharmacogenomics-related group compared with the control group,” GSC wrote in a statement releasing the findings.

Despite the study’s success, Pojskic says study of pharmacogenomics is still in its infancy in a lot of respects. “How a patient responds to a particular drug is complex,” he says. “Pharmacogenomics is not a silver bullet.”