Another CAMH clinical trial demonstrates the clinical benefits of pharmacogenetics for severe depression

Ruslan Dorfman, PhD, MBA8 août 2022

Pharmacogenetics (PGx) assesses how each person metabolizes medications based on their DNA. For example, different people given the same dosage of an antidepressant may have quite different levels of the drug in their blood - some may not respond until the drug is given at high doses, while others experience debilitating side effects even at the standard dose.

Multiple clinical trials have shown that patients with depression and anxiety recover faster when their treatment is matched to the person's DNA. Such an approach shortens the time to find effective treatment and optimal dose, thereby reducing time to recovery and helping patients avoid common medication-induced side effects and ineffective drugs.

A new clinical trial conducted at CAMH followed 276 patients for 52 weeks. Some received standard of care treatment (i.e. without a genetic test), while others received two types of pharmacogenetic tests. As in a previous large-scale trial that followed thousands of patients, symptoms improved much faster in a subset of patients for whom treatment was changed to a drug that was a better match to their DNA.

This smaller study showed statistically significant improvement because patients were followed for a longer time compared to other pharmacogenetic studies that did not produce positive findings within an 8-week follow-up. PGx testing is not a magic bullet that can instantly cure depression – it is a clinical tool to guide treatment, which takes time to change the disease trajectory. An earlier clinical trial in Toronto pharmacies demonstrated substantially faster patient recovery from anxiety and depression over 28 weeks in the Pillcheck PGx-guided treatment group.

All clinical trials confirmed that patients on "mismatched" medications experience side effects or fail to respond to treatment. Such mismatch can be discovered only with PGx testing. Therapeutic drug monitoring of drug levels in the blood is more complicated and limited to patients with severe mental health conditions. Meta-analyses of clinical trials show that pharmacogenetics can increase remission rates by 50% for major depression compared to treatment as usual.

DNA samples for PGx testing can be easily collected at a patient's home, pharmacy or medical clinic. Test results accompanied by a clinical pharmacist review help to resolve drug-drug and drug-supplement interactions and help family physicians to select better treatment options.

While reimbursement for PGx testing by public payers is pending, many private insurance plans already cover the cost of testing as part of extended health benefits. This latest CAMH PGx study adds to the growing evidence that PGx is highly effective in managing depression and should be considered by health policy decision-makers to support health system-wide implementation.