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New Hope for Alzheimer's

Therapies, Vaccines Previewed in Madrid

By Mark Huffman
ConsumerAffairs.com

July 23, 2006
Human trials are set to begin next month on a drug that some researchers say could eventually lead to a cure for at least some forms of Alzheimer's disease. The drug, known as PBT2, stopped the disease in mice, according to Australian researchers.

The findings were among a number of encouraging research findings presented at the 10th International Conference on Alzheimer's Disease and Related Disorders in Madrid, Spain.

George Fink, director of the Mental Health Research Institute of Victoria, which developed the drug in partnership with Prana Biotechnology, said that if researchers can replicate in humans what occurred in mice, the discovery will be "of great, immense importance."

Fink said PBT2 works by attacking a build up of the protein amyloid, which is thought to cause the brain to "rust." Researchers conducting clinical tests on animals say the drug acts very quickly, with amyloid levels dropping by 60 per cent within 24 hours of a dose.

"PBT2 may facilitate the clearance of beta amyloid from the brain, or prevent its accumulation," said Ashley Bush, Fink's colleague at MHRI. "On the basis of the encouraging results so far, Prana is initiating a Phase II, double-blind, placebo-controlled trial of PBT2 in Alzheimer's patients who are early in the natural history of the disease."

Bush said that when used in mice, the drug:

• improved memory performance within five (5) days of oral dosing

• rapidly reduced the levels of soluble beta-amyloid ("Abeta") in the brain, and

• restored normal function to Abeta impaired synapses.

In studies using the Morris Water Maze Test, it was demonstrated that PBT2 could quickly and significantly improve spatial memory -- an important barometer of cognitive function -- in seven-month old transgenic amyloid mice, which are a model for Alzheimer's disease, Bush said. The Morris Water Maze Test involves remembering the location of a submerged platform, requiring the mouse to employ higher-level learning and spatial memory skills in order to successfully navigate the maze.

"This data is compelling and very exciting because it shows that PBT2 not only may facilitate the clearance of Abeta from the brain or prevent its production, but more importantly may improve cognition," Bush said. "On the basis of the multiple encouraging results achieved to date, demonstrating that PBT2 has a rapid and potent mechanism of action, Prana is initiating a Phase II, double-blind, placebo-controlled trial of PBT2 in Alzheimer's patients.

Prana Biotechnology said it received an independent report in May 2006 that PBT2 was safe and well tolerated in humans in 800 mg doses.

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Alzheimer's disease affects about 4.5 million Americans, gradually destroys a person's memory and ability to learn, reason, make judgments, communicate, and carry out daily activities, according to the Alzheimer's Association. The disease is eventually fatal.

While there have been false claims and hopes for a cure in the past, experts remain optimistic that a cure can be found.

"Outstanding progress has already been made in unraveling the mysteries of Alzheimer's disease," said the Alzheimer's Research Foundation. "New understandings about these processes have already provided critical information about how doctors might prevent, delay, stop or even reverse the nerve cell damage that leads to the devastating symptoms of Alzheimer's.

Other Therapies

Other advances presented at the Madrid conference included positive results from the first Alzheimer "patch" and the ongoing story of immunotherapy and the Alzheimer "vaccine," including a revamped version of an existing prostate cancer drug (leuprolide) and the first transdermal patch for Alzheimer's.

Many of these new therapeutic strategies focus on stopping the formation of abnormal beta amyloid protein and amyloid plaques in the brain, or removing them once they are already there. Scientists regard two abnormal microscopic structures called "plaques" and "tangles" as Alzheimer's disease hallmarks.

Amyloid plaques are clumps of protein that accumulate outside the brain's nerve cells. The "amyloid cascade" is considered by many scientists to be the most mature theory of the cause of Alzheimer's.

"Amyloid as a possible cause for Alzheimer's must be thoroughly tested," said William Thies, PhD, Alzheimer's Association vice president for Medical & Scientific Relations. "We need an answer to this question so that we can then sharpen our focus on attacking amyloid and creating better treatments, or change the focus to other areas if the theory is wrong."

"At the same time, we are very encouraged to see a diversity of approaches to treating Alzheimer's showing some level of success," said Howard Fillit, MD, executive director of the Institute for the Study of Aging, Inc. "These include drugs with new targets, new mechanisms of action, and new methods of delivery. We must pursue every available avenue. The urgency has never been higher."

Transdermal Patch

Transdermal patches offer new opportunities to ensure proper delivery of Alzheimer's drugs. Since Alzheimer's initially affects memory, reasoning and decision-making abilities, it can be a problem for people with the disease to take drugs on a regular schedule. As the disease advances, people may not know what drugs are for or even what they are.

With further advance of the disease, sometimes the ability to swallow is affected. Transdermal drug delivery has the potential to eliminate issues about forgetting to take the drug or to take it at the right time, and also ease challenges associated with getting the person with Alzheimer's to take or swallow a pill.

It also provides visual reassurance for the caregiver that the medication has been taken. At the same time, possible skin irritation and the presence of a new or unknown object on their body may be confusing or annoying to the person with Alzheimer's, so a skin patch may not work for everyone.

Bengt Winblad, MD, PhD, of the Karolinska Institutet, Huddinge, Sweden, and colleagues at UCLA and Novartis sought to compare the efficacy, safety and tolerability of a novel, once-daily rivastigmine patch with conventional, twice-daily capsules. Rivastigmine is an FDA-approved cholinesterase inhibitor for treatment of mild to moderate Alzheimer's disease.

The researchers found that the rivastigmine patch showed statistically significant benefits versus placebo on both of these measures and the ability to perform activities of daily living. The recommended target dose 10 cm2 patch showed similar efficacy to the highest doses of rivastigmine capsules with three times fewer reports of nausea (7.2 percent vs. 23.1 percent) and vomiting (6.2 percent vs. 17.0 percent), which are well-known side effects of cholinesterase inhibitors.

The 20 cm2 patch showed improved cognitive scores versus capsules and similar tolerability to capsules. Local skin tolerability was good. Abnormal redness of the skin was present at moderate or severe levels in only 7.6 percent and 6.2 percent of patients receiving 10 and 20 cm2 patches, respectively.

"The rivastigmine patch provides similar efficacy to the highest capsule doses, and both formulations were superior to placebo," Winblad said. "The smaller patch had three times fewer gastrointestinal side effects than the capsule. A transdermal patch may prove to be the best way to deliver rivastigmine to treat Alzheimer's."

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