Pharmacogenetic Tests Lack Regulatory Oversight, Critics Say

Jacquelyn K Beals, PhD

April 03, 2008

April 3, 2008 — A critique from the Johns Hopkins University Genetics and Public Policy Center has identified problems with the current state of pharmacogenetic testing. The critique, published in the April 4 issue of Science, reports that many pharmacogenetic tests now available make misleading marketing claims or are sold direct to consumer (DTC), bypassing the "gatekeeper" function of a medical provider.

The authors warn that consumers' negative experiences with unregulated genetic testing could cause physicians and patients "to lose trust in the value of genetic testing to improve drug-prescribing decisions."

Genetic biomarkers are in the public eye, but only a few have been clinically proven to predict drug response. One of these, the breast cancer biomarker HER2, predicts tumor response to trastuzumab, and similar tests may be on the horizon. However, businesses offer genotyping related to the choice and dose of many medications — including antidepressants.

The Science article focuses on pharmacogenetic testing for the enzyme cytochrome P-450 (CYP450). CYP450 metabolizes, or is inhibited by, serotonin reuptake inhibitors (SSRIs), a class of antidepressant drugs including paroxetine (Paxil, GlaxoSmithKline), fluoxetine (Prozac, Eli Lilly & Co), fluvoxamine (Luvox, Solvay Pharmaceuticals Inc), and sertraline (Zoloft, Pfizer Inc). Variations in the structure of CYP450 are associated with higher or lower metabolic activity, leading a physician to prescribe a specific SSRI or to tailor the dose for a given patient.

In 2004, an evaluative group at the Centers for Disease Control and Prevention reviewed the data on CYP450. Although confirming the chemical interactions of SSRIs and CYP450, the study found "no evidence...that the results of CYP450 testing influenced SSRI choice or dose and improved patient outcomes."

Yet CYP450 genotyping services are available from 15 or more businesses, which differ in their claims regarding testing for specific antidepressants and the genes relevant for each SSRI. One real concern is that patients may request a certain medication or alter the dose of one they have been prescribed based on the results of tests that have not been validated.

Given the present situation, the authors advocate regulation in 3 areas:

  • The US Food and Drug Administration (FDA) should protect the public against tests without evidence of clinical benefit, by overseeing laboratory-developed tests that claim to detect genetic variants correlated with drug response. At present, the FDA regulates medical test kits but not laboratory-developed tests.

  • The Federal Trade Commission (FTC) should actively intervene to prevent misleading advertising claims for genetic testing. To date, the FTC has not taken steps against false claims made by genetic test providers.

  • Test providers, whether DTC or through medical facilities, should be required to submit information and supporting data about the use of the test to a public registry that is accessible to both physicians and patients.

Implementation of these safeguards will ensure that genetic tests are used and interpreted in ways that contribute to improved medical care and maintain public trust in genomic medicine, the authors conclude.

Science. 2008;320:53–54.

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