US FDA Approves Genetic Test for Personalized Drug Safety Test

2005-08-29 - Washington, D.C. USA: The United States Food and Drug Administration (FDA) has cleared for marketing a new blood test that will help doctors make personalized drug treatment decisions for some patients.

The test, called the Invader UGT1A1 Molecular Assay, detects variations in a gene that affects how certain drugs are broken down and cleared by the body. Doctors can use this information to help determine the right drug dosage for individual patients, and minimize harmful drug reactions.

"This test represents the power of DNA-based testing to provide individualized medical care," said Daniel Schultz, MD, Director of FDA's Center for Devices and Radiological Health. "These technologies can significantly improve patient management and reduce the risk of ineffective or even harmful drug therapy by telling doctors how to individualize drug dosing."

The Invader assay joins a growing list of genetic tests used by physicians to personalize treatment decisions, including the Roche AmpliChip, used to individualize dosage of antidepressants, antipsychotics, beta-blockers, and some chemotherapy drugs, and TRUGENE HIV-1 Genotyping Kit, used to detect variations in the genome of the human immunodeficiency virus that make the virus resistant to some anti-retroviral drugs.

The Invader assay, manufactured by Third Wave Technologies, Inc., in Madison, Wisconsin, detects variations in a gene called UGT1A1 that produces the enzyme UDP-glucuronosyltransferase. This enzyme is active in the metabolism of certain drugs, such as irinotecan, a drug used in colorectal cancer treatment. Variations in the UGT1A1 gene can influence a patient's ability to break down irinotecan, which can lead to increased blood levels of the drug and a higher risk of side effects. For a patient with a particular UGT1A1 gene variation, a dose of irinotecan that is safe for another person might be too high for this patient, raising the risk of certain side effects. The Invader assay was studied in 66 patients who were receiving irinotecan therapy. The study showed that persons with one type of genetic variation have a five times greater risk of experiencing irinotecan toxicity.

"With the growing interest in individualizing drug therapy, FDA's approval of this assay provides physicians and patients with important information on the proper dosage of drugs metabolized and cleared from the body by the UGT1A1 pathway," said Lawrence Lesko, PhD, Director of FDA's Office of Clinical Pharmacology and Biopharmaceutics in the Center for Drug Evaluation and Research. "Information on the UGT1A1 genotype can be an integral part of drug labels and will guide health professionals on how to dose medications such as irinotecan." The Invader assay is intended to aid a physician in making individualized patient treatment decisions. It is not a substitute for a physician's judgment and clinical experience. Other important factors that may affect dosing should be considered, such as the patient's liver function (measured in part by the level of bilirubin, a breakdown product of hemoglobin), age, kidney function, and co-administered drugs.

Meanwhile, an intellectual property law specialist has suggested that the dawning personalized-medicine revolution will require companies to take new strategies when patenting drugs and diagnostics.

Edward R. Gates, a senior attorney in the biotechnology practice of Wolf, Greenfield & Sacks, P.C., a Boston intellectual property law firm, told the Drug Discovery Technology & Development World Congress: "There's going to be a huge opportunity to impact the industry through innovative intellectual-property strategies".

Spurred by the sequencing of the human genome, personal medicine posits that some drugs work for only some people because of genetic differences. For instance, only 30% of the population may have a genetic marker that makes a drug highly effective.

Developing new drugs, companies might be able to run a smaller trial by selecting only patients with the right makeup. This could lead to speedier FDA approval, slash costs and spell the end of the "blockbuster" model for drug development, Gates said.

Makers of existing drugs could benefit even more. Suppose it's learned that a popular drug helps just 60% of the population. The company could file a new patent, make a label change, and possibly win an extra 20 years of exclusivity, he pointed out.

Patents directed to personalized medicine inventions must be aimed at all the potential infringers, which include chipmakers, software users, pharmacists, diagnostic companies, clinical labs, drug manufacturers, reagent suppliers, distributors and more, he said.

Gates said that patenting a personalized drug may not be the primary strategy. "The best protection may be to patent the genetic chip that does the test".

International patent law poses complications. Even if a drug is intended for use in the U.S. only, offshoring could complicate matters. For instance, a company might have blood samples analyzed in India. Patent strategies must take this into account.

A potential problem is that case law in Europe precludes patenting some of the types of inventions based on personalized medicine that are patentable here in the US. But diagnostics are patentable there. Most pharmaceutical companies aren't involved in diagnostics, which are handled by separate companies. With personalized medicine, that will all change," Gates predicts. The personalized medicine revolution is in its infancy, and solving IP challenges will likely be a conundrum for some time. "Crafting solutions will take creativity, taking into account what the FDA requires, what label changes are permitted and who might benefit commercially from the invention," said Gates.

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