Amyvid is a radiopharmaceutical developed by the Eli Lilly Company to aid in the diagnosis of Alzheimer’s disease by causing previously invisible beta amyloid plaque deposits in the brain to show up in PET scans. The FDA has recently approved Amyvid for clinical use although its use remains somewhat controversial.
Dr. Alois Alzheimer’s discovery of the physical changes in the brain in the early 1900s has caused researchers to focus on the plaque deposits he found in autopsied brains of diseased patients. If the plaque causes the disease, discovering the plaque before a patient’s symptoms worsen could mean closing in on a cure.
Amyvid travels in the bloodstream to the brain, where it binds to amyloid plaques, and enables the plaques to be seen in a PET scan (Positron Emission Tomography). Having the ability to diagnose the disease without waiting for a postmortem would be a significant leap in the treatment and prevention of Alzheimer’s disease.
Diagnosis of Alzheimer’s is made through tests designed to measure cognitive functions. Other than observation of a patient’s behavior, there is no medical method or test available to prove the existence of Alzheimer’s disease. The autopsy of a patient’s brain will confirm the diagnosis, but gives little comfort to the patient’s family.
Making an early diagnosis of a disease which has unknown causes and no treatment is not necessarily cause for celebration. A patient may show signs of dementia due to a brain tumor, stroke, or other neurovascular disease. Using Amyvid to expose the presence of plaque deposits in the brain can potentially rule out these other diseases and put the blame on Alzheimer’s.
But if plaque deposits are found, it may or may not be due to Alzheimer’s since autopsies of some healthy brains have shown plaque deposits too. When a patient is experiencing memory loss, confusion, impairment of reasoning ability, along with plaque deposits in the brain, the diagnosis is Alzheimer’s.
Patients diagnosed with Alzheimer’s will not benefit from the knowledge that they have a progressive, chronic disease that will eat away at their brain until all memory including their own identity is lost. It is little comfort to provide an early diagnosis without an accompanying treatment plan.
Temporarily managing the symptoms with drugs like Pfizer’s Aricept may be an option, but curing the disease is the ultimate goal. Pharmaceutical companies have been trying to develop a treatment for Alzheimer ’s disease for many years. Experimental drugs have gone into clinical trials, some have failed, and some are still in process.
Pfizer and Eli Lilly currently have drugs in clinical trials that are designed to break up the beta amyloid protein, which is the substance that forms plaque. Bapineuzumab (Pfizer) and Solanezumab (Lilly) are drugs that bind with the beta amyloid protein, and cause it to break apart with eventual removal by the blood stream. If these drugs survive the clinical trials and gain approval by the FDA, the world will breathe a huge collective sigh of relief in the hope that a cure for Alzheimer’s is real.
Offering solutions for a disease when the cause is not known may seem like a backward approach. Defining a disease and describing the symptoms is normally followed by the development of tests for accurate diagnosis, and finally a course of treatment or cure. In the case of Alzheimer’s, cures have been developed without knowing the cause and diagnosis has not been possible until after death. Since healthy brains can also contain plaque deposits, the ability to see plaque deposits on a brain via a PET scan is not absolute proof of Alzheimer’s disease.
Perhaps not seeing plaque deposits is a more encouraging result of Amyvid.
Research has been done on the Apolipoprotein E (ApoE) gene found on chromosome 19 to determine the cause of the plaque deposits. This gene causes the production of a lipoprotein that aids in cholesterol transport in the bloodstream. Healthy brains are able to remove the resulting plaque deposits. Of the different types, or alleles of ApoE, ApoE4 has been found to be present in approximately 40 percent of Alzheimer’s patients. Whether this is a coincidence or not remains to be discovered. Further studies on the genetic connection are ongoing.
The fear of developing Alzheimer’s is very real in people who have relatives with the disease, or are nearing age 65 when incidence of Alzheimer’s disease rises. The FDA’s approval of Amyvid for clinical use is encouraging, but without a cure, diagnosis can only bring despair. Confirmation of what has already been experienced in symptoms of memory loss and confusion gives no comfort. Perhaps the most valuable use of Amyvid is in the confirmation of the absence of plaque on PET scans. At least this would confirm the absence of Alzheimer ’s disease.
Source: Drugsdb.com – The Internet Drug Information & Side Effects Database.