May 23, 2013

FDA Continues Approvals of Companion Diagnostics for Pharmacogenetic Cancer Treatment

The regulation of genetic tests is uneven, with the FDA exercising enforcement discretion of this field within its general authority to regulate medical devices. To date, the FDA requires approval of genetic testing kits, considered to be in vitro diagnostics (IVD). The FDA has paid specific attention to one subset of genetic test kits, known as companion diagnostics. The FDA describes companion diagnostics: 
A companion diagnostic device can be in vitro diagnostic device or an imaging tool that provides information that is essential for the safe and effective use of a corresponding therapeutic product. The use of an IVD companion diagnostic device with a particular therapeutic product is stipulated in the instructions for use in the labeling of both the diagnostic device and the corresponding therapeutic product, as well as in the labeling of any generic equivalents and biosimilar equivalents of the therapeutic product.
Companion diagnostics illustrate the use of pharmacogenetics to refine pharmaceutical treatment of cancers or other illnesses. The FDA has just approved a new companion diagnostic test for use in the treatment of non small cell lung cancer, the cobas EGFR Mutation Test that refines the optimal use for Tarceva, a biotech drug approved by the FDA in 2004 (a monoclonal antibody). This approval scenario illustrates how the optimal treatment profile for an already approved drug is being refined by subsequent genetic research, where new understandings of the relationship between particular genes and the specific cancers is allowing for more refinement in treatment decisions. The FDA published a guidance document for the approval of companion diagnostics in 2011: 
An IVD companion diagnostic device could be essential for the safe and effective use of a corresponding therapeutic product to identify patients who are most likely to benefit from a particular therapeutic product; identify patients likely to be at increased risk for serious adverse reactions as a result of treatment with a particular therapeutic product; or monitor response to treatment for the purpose of adjusting treatment (e.g., schedule, dose, discontinuation) to achieve improved safety or effectiveness. 
The FDA also recognizes a scenario of co-development between a drug manufacturer and a test developer, such that both products are approved simultaneously, as illustrated by the FDA's co-approval of Xalkori and the Vysis ALK Break Apart FISH Probe Kit in 2011. The list of approved companion diagnostics continues to grow. As a general matter, the FDA regulates genetic tests sold as kits to laboratories or consumers. In the general genetic testing market, however, most genetic tests are offered as laboratory-derived tests (LDTs), available as services, rather than products. The FDA does not regulate LDTs, although it has stated that some LDTs are considered medical devices, subject to its oversight. However, despite issuing a statement of intention for possible oversight in 2010, the FDA to date has not taken on LDTs in general, or even the genetic LDTs. Laboratories providing LDTs are regulated under the Clinical Laboratory Improvement Amendments (CLIA), administered by the Centers for Medicare and Medicaid Services (CMS), which requires that laboratories meet specified standards, and that individual tests are scientifically accurate, but which does not evaluate the clinical validity or clinical utility of LDTs. Calls for the FDA to increase its involvement in the regulation of LDTs have come from many sources, including the Secretary's Advisory Committee for Genetics, Health and Society in 2008. More recently, the American College of Medical Genetics published a risk-classification framework for the regulation of LDT genetic tests, calling for FDA pre-market approval of high-risk LDTs, where "the consequence of an incorrect result or interpretation could lead to serious mortality or morbidity."

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