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Revolutionising Medicine Through Personalised Treatment
Pharmacogenetics (PGx) is transforming the way we approach medicine. This innovative field explores how our genetic makeup influences the way we respond to medications, enabling more personalised treatments. PGx testing has been gaining traction over the past few decades, but where did it all begin, and how has it evolved into the precision tool it is today?
The Early Days: From HIV to Genotyping
The origins of pharmacogenetics can be traced back to the HIV epidemic. Early treatments, such as abacavir (Ziagen) and efavirenz (Sustiva), showed that while some patients experienced significant improvements, others saw little to no benefit or developed severe side effects. This prompted researchers to investigate whether genetic differences were responsible for these varying responses. In the case of abacavir, the discovery of the HLA-B*57:01 gene variant was key. Patients with this genetic variant were at a significantly higher risk of developing a hypersensitivity reaction to abacavir, leading to the inclusion of genetic testing before prescribing the drug.
Similarly, efavirenz metabolism is affected by variants in the CYP2B6 gene, which encodes an enzyme responsible for breaking down the drug. Patients with certain variants of CYP2B6 metabolise efavirenz more slowly, leading to higher drug concentrations and an increased risk of neuropsychiatric side effects. By identifying these genetic differences, doctors were able to tailor treatments to individual patients, thus avoiding potentially dangerous side effects and improving efficacy.
A similar pattern was observed during the COVID-19 pandemic, where some individuals responded well to vaccines, while others did not. Once again, genetic research played a critical role in understanding these differences, allowing scientists to refine their approach to immunisation and treatment.
Caffeine Metabolism: A Simple Story of PGx
One of the most relatable examples of pharmacogenetics is the way our bodies metabolise caffeine. The enzyme responsible for breaking down caffeine is coded by the CYP1A2 gene. Approximately 40% of the global population carries a variant of this gene that makes them slow metabolisers of caffeine, meaning the stimulant stays in their system longer. The other 60% are fast metabolisers, who can process caffeine more quickly, often meaning they can drink coffee later in the day without trouble.
This example is often used to illustrate the power of pharmacogenetics in a way that everyone can understand. Just as different people metabolise caffeine at different rates, the same principle applies to medications. Knowing someone’s genetic makeup allows doctors to predict how they might respond to a drug, which is key to personalised medicine.
Mental Health Medication: The Case of Antidepressants
While caffeine provides a straightforward example of pharmacogenetics, the field's real potential shines in more complex cases, such as mental health treatments. Take antidepressants, for instance. Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed for depression, but they don’t work equally well for everyone.
A gene frequently involved in the metabolism of SSRIs is CYP2C19. Some people carry a variant of this gene that makes them "poor metabolisers," meaning the drug stays in their system longer, potentially causing side effects or reducing efficacy. Others are "ultrarapid metabolisers," processing the drug too quickly for it to have the intended effect. Understanding a patient’s CYP2C19 genotype helps doctors adjust dosages or choose alternative medications, ensuring a better therapeutic outcome.
For example, sertraline (commonly known as Zoloft), a widely prescribed SSRI, is metabolised primarily by CYP2C19. Knowing a patient’s genetic profile can help predict whether they will have a typical response to the drug or if an adjustment is necessary to avoid either side effects or ineffectiveness.
ADHD Medication: The Role of Pharmacogenetics in Stimulants
Pharmacogenetics is also making strides in the treatment of attention deficit hyperactivity disorder (ADHD), particularly when it comes to stimulant medications such as methylphenidate (Ritalin) and amphetamine (Adderall). These medications are metabolised by enzymes in the cytochrome P450 system, including CYP2D6, which plays a key role in the metabolism of many psychostimulants.
Variants of CYP2D6 can result in patients being classified as poor, intermediate, extensive, or ultrarapid metabolisers of ADHD medications. Poor metabolisers may experience higher concentrations of the drug in their system, leading to increased side effects, such as irritability or difficulty sleeping, while ultrarapid metabolisers may break down the medication too quickly for it to be effective.
In particular, atomoxetine (Strattera), a non-stimulant ADHD medication, is metabolised by CYP2D6. Poor metabolisers of CYP2D6 tend to have higher blood levels of atomoxetine, which can increase the risk of side effects, while ultrarapid metabolisers may not receive sufficient therapeutic benefit. Knowing a patient’s CYP2D6 status can help doctors adjust doses or consider alternative treatments, optimising the efficacy of ADHD medications and minimising side effects.
The Present and Future of PGx Testing
Today, PGx testing is increasingly incorporated into drug development and clinical practice. When new drugs are introduced, many manufacturers now perform genetic testing on participants during early clinical trials to identify genetic markers associated with better or worse responses. This data allows them to include pharmacogenetic information on drug labels, guiding doctors in prescribing the right drug for the right patient.
In mental health, as well as in other fields such as pain management and cardiovascular care, PGx is poised to play a major role in personalising treatments. The FDA has already included PGx recommendations in the labelling of many medications, and this trend is only expected to grow.
While older drugs are less likely to have undergone such rigorous genetic scrutiny, researchers can still use what is known about the mechanisms of these drugs to infer how they might work for different genetic profiles. This means that even in cases where specific genetic testing wasn't done during a drug's development, doctors can still use PGx knowledge to predict outcomes.
Pharmacogenetics and You
Pharmacogenetics has come a long way since its origins in HIV treatment research, now influencing a broad range of fields, from vaccines to mental health treatments. The ability to predict how patients will respond to drugs, based on their genetic makeup, is revolutionising healthcare, ensuring that treatments are not just one-size-fits-all but tailored to each individual’s unique biology. As science advances, PGx testing will become an even more critical tool in the hands of clinicians, making personalised medicine the standard of care.
Ready to experience the benefits of personalised medicine? Visit our website to learn more, request a quote, or contact us today to see how our cutting-edge PGx testing can make a difference for you.