Savvy Psychopharmacology

Pharmacogenomics testing: What the FDA says

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Practice Points

Mr. R, age 30, is referred to you by his primary care physician, who diagnosed him with depression approximately 2 years ago. When he was first diagnosed, Mr. R was prescribed sertraline, 100 mg/d, which was effective. He maintained this response for approximately 1 year, but then the sertraline stopped working. During the last year, Mr. R received citalopram, 20 mg/d, and paroxetine, 20 mg/d. Neither medication was effective for his recurrent depressive symptoms and resulted in significant adverse effects.

Mr. R says that based on his primary care physician’s recommendation, he had undergone pharmacogenomics testing to help guide therapy. He presents the results to you, and you notice that he has the cytochrome P450 (CYP) 2C19 *2/*3 genotype and a CYP2D6*4/*5 genotype. Both are associated with a poor metabolism phenotype. Should you use these findings to determine which medication Mr. R should be treated with next?

While the field of pharmacogenomics is not new, within the last few years this science has begun to transition into clinical practice. A recent meta-analysis found support for using pharmacogenomics testing results in clinical practice.1 This study included more than 1,700 patients who took part in 5 controlled trials that randomized participants to either pharmacogenetics-guided or unguided (ie, standard) treatment. Each participant was assessed using the Hamilton Depression Rating Scale-17 (HDRS-17) a minimum of 3 times over a minimum of 8 weeks.1 While the exact inclusion and exclusion criteria for each trial differed, they all defined remission of depression as achieving an HDRS-17 score ≤7. Overall, the authors concluded that based on the random-effects pooled risk ratio, there was a significant association between pharmacogenetics-guided prescribing and remission (relative risk = 1.71, 95% confidence interval [CI], 1.17 to 2.48; P = .005). The results of this meta-analysis are controversial, however, because all 5 studies were industry-funded, and interpretation of the testing results was based on proprietary algorithms.

Experts in the field and professional societies, such as the International Society of Psychiatric Genetics (ISPG), have issued policy statements on genetic testing within psychiatry.2,3 While the ISPG did not necessarily endorse use of pharmacogenomics in practice, they recommended that clinicians follow good medical practice and stay current on changes to drug labeling and adverse event reports.3 The ISPG also noted that useful but not exhaustive lists of pharmacogenetic tests are maintained by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and the US FDA.3

Laboratory developed vs direct-to-consumer tests

In a previous Savvy Psychopharmacology article,4 we had discussed the role of CPIC, but not the role of the FDA. This issue is key because there is a lack of clarity regarding pharmacogenomics tests and whether they are considered Class II devices by the FDA, which would require their review and approval. Until recently, the FDA was fairly quiet regarding pharmacogenomics tests because most of these tests were considered laboratory developed tests, which were regulated under the Clinic Laboratory Improvements Amendments program. The critical distinction of a laboratory developed test is that it is developed and performed in a single laboratory and is offered to patients only when prescribed by a clinician. Due to this distinction, laboratory developed pharmacogenomics tests did not need FDA 510(k) clearance, which is a premarket submission common for medical devices.

Direct-to-consumer pharmacogenomics tests are different in that the FDA has classified these platforms as medical devices; however, they are reviewed by the FDA only if they are being used for moderate- to high-risk medical purposes, or if the results of the testing may have a higher impact on medical care. As part of its review, the FDA examines test accuracy and reliably measures to determine if the measurement is predictive of a certain state of health and supported by what the company claims about the test and how well it works. Additionally, the FDA examines the company-provided descriptive information to ensure that consumers can easily understand it without the help of a clinician.5

Conflicting FDA statements

Recently the FDA issued 2 statements—one a policy statement and the other a safety communication—about laboratory developed tests and direct-to-consumer tests. The statements appear to contradict themselves, despite focusing on using pharmacogenomics testing in practice.

Continue to: The FDA's first statement

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