The Food and Drug Administration approved a new brain imaging drug for use in the diagnosis of Alzheimer’s disease, the second such drug to be approved for use in the United States. The approval expands options for those undergoing brain scan tests for dementia and reflects advances in the diagnosis of Alzheimer’s in recent years.
Still, the diagnosis of Alzheimer’s remains imperfect. Definitive diagnosis can only be made on examination of the brain after death. And even if Alzheimer’s is strongly suspected, treatment options remain limited.
The new drug, called Vizamyl, is a radioactive dye that is used along with brain scans to detect the presence of beta amyloid, the toxic protein that builds up in the brains of those with Alzheimer’s disease. It also goes by the name flutemetamol F 18.
Doctors typically assess Alzheimer’s by taking a thorough medical history, which may include interviews with family members and caregivers, and administering in-depth clinical tests that measure memory and thinking skills, personality changes and problems with reasoning and language. If Alzheimer’s is suspected, then patients may undergo a brain scan using Vizamyl or another drug called Amyvid (also known as florbetapir F 18), which was approved for use in 2012. Other drugs are also undergoing testing.
“Many Americans are evaluated every year to determine the cause of diminishing neurologic functions, such as memory and judgment, that raise the possibility of Alzheimer’s disease,” said Dr. Shaw Chen, of the FDA’s Center for Drug Evaluation and Research. “Imaging drugs like Vizamyl provide physicians with important tools to help evaluate patients for Alzheimer’s disease and dementia.”
Like Amyvid, Vizamyl, which is expected to be widely available in 2014, is given by injection. Once the drug enters the bloodstream, it can pass into the brain and attach to any beta amyloid plaques that may be present. Patients then undergo a PET scan, a specialized method of brain imaging that records how much of the radioactive dye has bound to beta amyloid in the brain, and where it is concentrated.
The drug was evaluated in two late-stage trials involving about 400 people. The most common adverse reactions, which occurred in less than 2 percent of patients, were flushing, high blood pressure, headache, nausea and dizziness. One patient had an allergic reaction, marked by flushing, shortness of breath and chest pressure within minutes of drug injection, and recovered with treatment.
Use of these brain imaging drugs does not prove that someone has Alzheimer’s, but they can suggest the diagnosis. If the PET scan indicates that little beta amyloid is present, a patient is less likely to have Alzheimer’s; another form of dementia may be causing memory loss. A high amount of beta amyloid, on the other hand, increases the likelihood that someone has Alzheimer’s, although many people who do not have dementia still have beta amyloid deposits in their brains.
Vizamyl is not indicated to predict the development of Alzheimer’s or to check how patients respond to treatment for the disease. But “the ability to detect or exclude the presence of beta amyloid plaques in the brain may help physicians make more accurate assessments of patients with suspected cognitive disorders, including Alzheimer’s disease," said Dr. William E. Klunk, Distinguished Professor of Psychiatry and Neurology at the University of Pittsburgh.
Source: Food and Drug Administration; GE Healthcare.