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FDA Approves First Treatment for Fabry Disease
The new product, called Fabrazyme (agalsidase beta), is a version of the human form of the natural enzyme produced by recombinant DNA technology. It is given intravenously. This replacement of the missing enzyme reduces a particular type of lipid (fat) accumulation in many types of cells, including blood vessels in the kidney and other organs. It is believed likely that this reduction of fat deposition will prevent the development of life-threatening organ damage and have a positive health effect on patients.
"This priority approval of an orphan drug illustrates FDA's commitment to approving innovative new therapies for patients with serious and life-threatening diseases quickly, based on response to treatment of biological markers likely to predict long-term clinical benefit." said FDA Commissioner Mark B. McClellan, M.D., Ph.D. "The orphan drugs program provides crucial incentives for innovators to develop new treatments for rare diseases. By approving this new biotechnology therapy under the 'accelerated approval' process, we are making this product available more quickly to patients who need it."
Fabrazyme was approved under an accelerated or early approval mechanism. This policy allows for expediting the approval of therapies that treat serious or life-threatening illnesses when studies of the products indicate early favorable outcomes that are likely to predict clinical benefit. The approval is based on "surrogate endpoints" - laboratory measurements or physical signs - for evidence of effectiveness. The surrogate endpoints are believed to be likely to predict benefit for the patient.
In this case, the manufacturer of Fabrazyme (Genzyme Corporation, Cambridge, Mass.) has performed biopsies looking at the cells lining the blood vessels within the kidney and other organs in patients with Fabry Disease. Many (but not all) of the cells examined have shown significant clearance of lipid deposits in patients treated with Fabrazyme.
"A key part of our accelerated approval process involves further study of the new treatment after approval, to confirm clinical benefit," said Dr. Jesse Goodman, Director of FDA's CBER. "In this case, FDA has worked closely with the product developer to make sure that, despite the relatively small number of patients with this disease, all reasonable steps will be pursued to make sure that we learn more about the product's clinical benefits and long-term safety once it is on the market."
One of the requirements of an accelerated approval is that the sponsor completes a postmarket study verifying that patients will benefit from the product. Genzyme has committed to continue conducting their ongoing randomized placebo-controlled trial to verify Fabrazyme's benefit to patients and by assessing the drug's effects on the progression of kidney and heart disease and the incidence of strokes.
In addition, Genzyme is taking further steps to assure the availability of information to determine long-term effects of treatment with Fabrazyme. Genzyme has set up a patient registry to follow the long-term progress of patients who have been treated to better understand Fabry disease and to evaluate the long-term effects of treatment. Enrollment in this registry is voluntary.
FDA and Genzyme are also discussing a variety of novel statistical approaches to analyze data and better assess the effectiveness of the treatment, to augment the data collected through the clinical trial. The potential approaches being evaluated include measures such as within-patient analyses of trends in creatinine levels (a measure of kidney function) on placebo and on Fabrazyme, and modeling utilizing historical information from matched patients.
"Effective studies after approval are essential for collecting valuable evidence on the clinical benefits and longer-term effects of products approved on an accelerated basis," said FDA Commissioner McClellan. "FDA intends to evaluate whether the continuation of the Fabrazyme clinical trial, potentially coupled with additional analyses of data from patients who many not complete the trial and of data from patients receiving long-term treatment, represents the most effective approach to acquiring important confirmatory evidence after approval."
In clinical studies of Fabrazyme, the main safety concern in patients receiving Fabrazyme was infusion reactions, some of which were severe. These include fever, chest tightness, blood pressure changes, abdominal pain and headache. Most patients also develop antibodies to the product and some patients who experience allergic reactions may need to be further evaluated. Because of the potential for these severe reactions, appropriate medical observation and support should be available when Fabrazyme is administered.
Orphan products are developed to treat rare diseases, or conditions that affect fewer than 200,000 people in the U.S such as Fabry Disease. Under the Orphan Drug Act, FDA provides modest grants to organizations to develop products to treat "orphan" diseases. The act provides a seven-year period of exclusive marketing to the first sponsor who obtains marketing approval for a designated orphan drug.