Using powerful new drug-screening technologies, researchers are identifying dozens, perhaps hundreds of possible targets for drugs aimed at preventing, treating, or slowing the progression of Alzheimer's disease (AD). Many of these compounds appear to work in animals with Alzheimer's-type dementia -- good news for little furry creatures.
But for the estimated 25 million people worldwide with Alzheimer's disease and other forms of dementia and the millions more who care for them, the news about drugs for Alzheimer's disease -- after the first blush of enthusiasm has faded -- has ranged from mildly promising to disheartening.
The symptoms of Alzheimer's disease often come on gradually. They then typically progress over several years to the point of causing major impairment.
Alzheimer's can be divided into mild, moderate, or severe stages. Each stage has a separate set of symptoms. But symptoms can vary from person to person. And the length of each stage can also vary.
Perhaps it's a measure of how difficult the problem is that one of the biggest headlines from the 9th International Conference on Alzheimer's Disease and Related Disorders in Philadelphia came from a clinical trial of the drug Aricept. The drug appears to delay the onset of Alzheimer's disease in people with mild cognitive impairment by six to perhaps 18 months, according to researcher Ronald Petersen, MD, PhD, from the Mayo Clinic in Rochester, Minn. Mild cognitive impairment appears to set the stage for the development of Alzheimer's dementia.
There is no cure for Alzheimer's disease. The drugs used to treat the disease work to slow the progression of symptoms. Aricept works by preventing the breakdown of acetylcholine, a chemical used by the brain for memory and thinking. But studies have shown that the benefits of this treatment are short lived; by 18 months, patients who received Aricept had the same rate of progression to Alzheimer's disease as those who received a placebo.
Aricept is one many drugs used to treat Alzheimer's disease. It and medications such as Reminyl and Exelon are called cholinesterase inhibitors. In various studies, these drugs have shown small to modest improvements in memory and thinking skills in people with AD.
In April 2005, Reminyl's label was changed to include information about the deaths of 13 elderly patients who were taking the drug during a study. The deaths were due to various causes, including heart attack and stroke.
Another group of drugs, called NMDA receptor antagonists, have also shown minor improvements in mental function among patients with moderate to severe AD. These drugs work by controlling the levels of another chemical that is involved in processing and retrieving information.
Namenda is the only drug in this class approved for the treatment of moderate to severe AD. A recently published study showed that Namenda combined with Aricept allowed people with moderate to severe Alzheimer's disease to perform better in daily activities such as grooming, being left alone, and using the toilet. People receiving the drug combination also had a reduction in behavioral disturbances such as agitation and psychiatric symptoms that are among the most common causes of nursing-home placements among patients with AD. Studies presented at the current meeting also suggest that the drug is safe and effective at improving mental abilities and daily functioning.