The new era of pharmacogenetic testing for precision healthcare

Pharmacogenetic (PGx) testing uses people’s unique DNA profiles to predict how they will respond to specific drugs, raising exciting possibilities for precision medicine and improved patient care. While PGx testing has often been overlooked in the past, it has grown in availability and utilization in recent years.

Yesterday’s plenary session, titled “Implementation of PGx-based Testing in Precision Health: Do You Have Your DNA-passport?” featured Ron H.N. van Schaik, PhD, FADLM, EuSpLM, a dedicated advocate for the value of pharmacogenetic testing.

He started with an informative overview of PGx testing and its applications, citing examples of CYP2D6 genotyping, which is being used to rule out patient non-compliance, predict sub-therapeutic drug concentrations using standard doses, and explain adverse drug reactions. Giving historical context, van Schaik noted that, starting nearly 20 years ago, package inserts for some drugs included pharmacogenetic information and testing recommendations. Today, there are more than 300 different drugs on the market that include PGx information, with well over one-third of these having specific requirements for PGx testing.

As van Schaik explained, this rapidly growing list of PGx-influenced drugs span a broad range of treatments in psychiatry, pain management, cardiology, and oncology, resulting in an increased need for PGx testing. In addition, multiple clinical trials have demonstrated improved outcomes in patients receiving “DNA-guided” dosing, a prospective approach where genotypic information is used to determine the initial drug selection or dosing instead of relying on the traditional trial and error method.

For example, a CYP2C19 genotype-guided approach to clopidrogrel dosing yielded non-inferior performance for thrombosis prevention and fewer severe bleeding events compared to ticagrelor, the more expensive alternative.

PGx testing will continue to grow due to a shift in the field from single-gene tests for a specific drug toward large genetic panels that provide comprehensive PGx data about drugs a patient is currently receiving or may receive in the future, van Schaik said. He is a proponent for a one-time “DNA passport,” which refers to a PGx report or ID card that patients can share with their providers and pharmacists to ensure all available PGx information is considered for dosing decisions.

Refining the list of genes and alleles with sufficient evidence to be actionable requires collaboration within and among professional organizations nationally and internationally. Efforts in this area are increasing, and there has been improved synchronization among various guidelines or recommendations, such as those from the Clinical Pharmacogenetics Implementation Consortium (CPIC) and the Dutch Pharmacogenetics Working Group (DPWG). Currently, more than 60 drugs have evidence-based dosing guidelines per genotype available.

In conclusion, van Schaik emphasized his excitement about how DNA passports could revolutionize patient care. Instead of subjecting patients to frustrating, lengthy, and harmful trial and error periods, clinicians can make more informed drug choices from the beginning. This will not only improve patient satisfaction and outcomes, but also promises to improve safety and decrease healthcare costs.

When reflecting on the value of pharmacogenetics, van Schaik encouraged attendees to ask themselves a critical question: “Did I make sure that my patient can handle the drug I’m prescribing?”