A Phase III Alzheimer's Drug Increase Levels of Beta Amyloid in the Brain - But Still Provides Benefits
Immunotherapy Targets Alzheimer's Tau Tangles |
More Doctors Diagnosing and Treating Mild Cognitive Impairment
Vienna, July 15, 2009 - New insights into how a Phase III Alzheimer's drug might work were among the advances in potential therapies targeting two abnormal brain proteins - beta amyloid and phosphorylated tau - that were reported today at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease (ICAD 2009) in Vienna.
Scientists also reported on how clinicians view and treat mild cognitive impairment (MCI), a research category used to define the state between normal aging and Alzheimer's, that is now being used widely in clinical practice.
"There are now more than 5 million people living with Alzheimer's disease in the United States. The cost of caring for people who now have Alzheimer's, and those who will get it in the next few years, will bankrupt the healthcare system and devastate Medicare and Medicaid," said Ralph Nixon, PhD, MD, vice chair of the Alzheimer's Association Medical & Scientific Advisory Council.
"But, as these studies and many hundreds more reported at ICAD 2009 show, there is hope. There are currently dozens of drugs in Phase II and III clinical trials for Alzheimer's. This, combined with advancements in diagnostic tools, has the potential to change the landscape of Alzheimer's in our lifetime. How fast we get there depends completely on the investment in research. We need more government and private dollars for Alzheimer's research now to capitalize on the progress we've made in the last decade," Nixon added.
Surprisingly, Dimebolin Increases Brain Beta Amyloid in Alzheimer's Mouse Models
Recent evidence suggests that dimebolin (Dimebon®, Medivation) may improve cognitive function in aged rodents and in people suffering from mild to moderate Alzheimer's, but how the drug produces these benefits remains unclear.
Samuel Gandy, MD, PhD, Mount Sinai Professor in Alzheimer's Disease Research; Professor of Neurology and Psychiatry; and Associate Director, Alzheimer's Disease Research Center at the Mount Sinai School of Medicine, New York, and colleagues John Cirrito PhD, and David M. Holtzman, MD, Professor and Chairman of the Department of Neurology at Washington University in St. Louis, MO, conducted a series of experiments in cells and in Alzheimer's mouse models to assess the effects of dimebolin on beta amyloid and other brain proteins known to be related to Alzheimer's disease.
Beta amyloid is a protein that is the main constituent of amyloid plaques found in the brains of people with Alzheimer's disease. It is widely considered a key player in the development and progression of Alzheimer's. The goal of anti-amyloid drugs that are currently in clinical trials is to reduce beta amyloid levels in the brain.
In a surprising result, the researchers at Washington University in St. Louis found that treatment with dimebolin caused an acute increase in brain beta amyloid levels in the animal models.
"This result is highly unexpected in what may prove to be a clinically beneficial Alzheimer's drug," Gandy said. "We need more research to further clarify how dimebolin affects beta amyloid levels in the brain."
"A number of ideas need to be pursued. It may turn out that the drug works by getting toxic amyloid out of brain nerve cells. Or, the effects of dimebolin on other brain systems may override its effect on increasing beta amyloid. Finally, the drug's beneficial actions might have nothing to do with amyloid, which, if true, indicates the existence of important therapeutic targets independent of beta amyloid," Gandy added.
The researchers note that so far they only studied acute systems, and it is conceivable that the chronic effect of dimebolin could be amyloid-lowering.
Immunotherapy Against Tau Tangles in Alzheimer's Mouse Models
Immunotherapy (treatment by inducing, enhancing, or suppressing an immune response) targeting beta amyloid is being researched widely by companies and academics as a therapeutic option for Alzheimer's disease. Earlier, late stage, anti-amyloid immunotherapy trials in people were complicated, and eventually stopped, when about six percent of participants developed brain inflammation. Current trials in this area are working in a variety of ways to eliminate this side effect.
Tau tangles, the other major Alzheimer's brain pathology, are now also receiving attention as a target for immunotherapy. Also known as neurofibrillary tangles (NFTs), these lesions consist of an abnormal folded protein (phosphorylated tau), and research shows their accumulation in the brain is more closely associated with the progression of Alzheimer's symptoms than amyloid.
Building on previous studies using this approach (for example, Asuni et al. (2007)), Hanna Rosenmann, Ph.D., head of the Laboratory of Molecular Neurogenetics, Department of Neurology, Hadassah University Hospital, Ein Kerem, and an Investigator (Associate-Senior Lecturer) at the Hebrew University Hadassah School of Medicine, Jerusalem, Israel, and colleagues performed immunization studies against tau tangle pathology by immunizing NFT mice with a mixture of three phosphorylated-tau peptides (shortened versions of the full length tau protein that are phosphorylated like the NFTs). Previous experiments by this lab with non-phosphorylated full length tau caused brain inflammation in the animal models.
The researchers observed a robust decrease in the number of tau tangles in the brains of the mice immunized with the phosphorylated tau-peptides (~40%; p<0.001), and detected anti-phosphorylated-tau antibodies in mouse serum. They found no evidence or symptoms of brain inflammation in the immunized mice.
According to Rosenmann, the decrease in tau tangles observed by her team is in accord with previous findings by Asuni's group, though Asuni immunized with a different phosphorylated tau peptide and immunization protocol.
"We believe that these results point to the therapeutic potential of phosphorylated-tau-immunotherapy in Alzheimer's," Rosenmann said. "We devoted significant effort to address not only the anti-tangle effect but also safety of a phosphorylated-tau vaccine. This was done in order to identify early in the preclinical stage any potential hazard of this potential Alzheimer's therapy."
Neurologists Views MCI as a Useful Clinical Diagnosis - Practice Guidelines Are Needed
Mild cognitive impairment (MCI) is a category of cognitive status that is used in research to define the state between normal aging and Alzheimer's, and it is now entering clinical practice. Little is known about how it is being used by clinicians or how they view the benefits and limitations of MCI as a clinical category.
In MCI, a person has problems with memory, language, or another mental function severe enough to be noticeable to other people and to show up on tests, but not serious enough to interfere with their daily life. Because the problems do not interfere with daily activities, the person is not diagnosed with Alzheimer's or another dementia. The best-studied type of MCI involves a memory problem and is called "amnestic MCI."
Research has shown that people with MCI have an increased risk of developing Alzheimer's over the next few years, especially when their main problem is memory. However, not everyone diagnosed with MCI goes on to develop Alzheimer's. There is currently no treatment for MCI approved by the FDA. Numerous clinical trials are investigating treatments to delay or prevent Alzheimer's in MCI populations.
Scott Roberts, PhD, Assistant Professor of Health Behavior & Health Education at the University of Michigan's School of Public Health; Jason Karlawish, MD, Associate Professor of Medicine and Medical Ethics with tenure, Senior Fellow of the Center for Bioethics and the Leonard Davis Institute of Health Economics, and Associate Scholar at the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania; and colleagues sought to assess how neurologists are diagnosing and treating patients with mild cognitive symptoms and how they view MCI as a clinical diagnosis. They surveyed members of the American Academy of Neurology (AAN) who had indicated a clinical practice focus on aging/dementia or behavioral neurology in a recent AAN Member Census using mail, fax and the Internet.
420 clinicians (response rate=48%) completed the survey. 88% reported at least monthly encounters with patients experiencing mild cognitive symptoms. Most respondents recognize MCI as a clinical diagnosis (90%) and use its diagnostic code for billing purposes (70%). When seeing this population, most respondents report routinely making recommendations for monitoring and follow-up (88%), counseling patients on physical (78%) and mental exercise (75%), and communicating about risk of dementia (63%).
Most respondents (70%) prescribe cholinesterase inhibitors at least sometimes for this population, with memantine (39%) and "other" agents (e.g., vitamin E, gingko) prescribed less frequently. Cholinesterase inhibitors and memantine are FDA-approved drugs for Alzheimer's. Relatively few respondents routinely provide information on support services (27%) or a written summary of findings (15%).
Respondents endorsed several benefits of making a clinical diagnosis of MCI:
Labeling the problem is helpful (91%)
Involving the patient in planning for the future (87%)
Motivating the patient's risk reduction activities (85%)
Helping the family with financial planning (72%)
Prescribing medications useful for treating MCI (65%)
Some respondents noted potential drawbacks of MCI as a clinical diagnosis, including:
It is too difficult to diagnose accurately or reliably (23%)
It is usually better described as early AD (21%)
A diagnosis can cause unnecessary worry (20%)
"Our results show that neurologists regularly see and treat people with MCI, despite the fact that the medications they are prescribing are not FDA-approved for this particular diagnostic category," Roberts said. "Clinicians vary greatly in the education and support they provide or recommend for people with MCI, suggesting that there is a need for practice guidelines in this area. Millions of people can be classified as having MCI, and these numbers are expected to rise in coming years. It is important to establish professional consensus about appropriate care for this population."
According to Roberts, the AAN is currently engaged in an evidence-based medicine review of the literature to develop a new practice parameter for MCI.
About ICAD 2009
The 2009 Alzheimer's Association International Conference on Alzheimer's Disease (ICAD 2009) brings together more than 5,000 researchers from 60 countries to share groundbreaking research and information on the cause, diagnosis, treatment and prevention of Alzheimer's disease and related disorders. As a part of the Association's research program, ICAD 2009 serves as a catalyst for generating new knowledge about dementia and fostering a vital, collegial research community. ICAD 2009 will be held in Vienna, Austria at Messe Wien Exhibition and Congress Center from July 11-16.
About the Alzheimer's Association
The Alzheimer's Association is the leading voluntary health organization in Alzheimer care, support and research. Our mission is to eliminate Alzheimer's disease through the advancement of research, to provide and enhance care and support for all affected, and to reduce the risk of dementia through the promotion of brain health. Our vision is a world without Alzheimer's. For more information, visit www.alz.org.
Sam Gandy, et al -- Dimebon®, A Clinically Promising Drug For Alzheimer Disease, Regulates Amyloid-Beta Metabolism In Cultured Cells, In Isolated Nerve Terminals, And In The Interstitial Fluid Of The Living Rodent Brain (Funders: Cure Alzheimer's Fund, National Institute on Aging)
Moran Boimel, et al -- Immunotherapy Targeting Pathologically Phosphorylated Tau In A Tauopathy Mouse Model (Funder: Agnes Ginges Fund)
Scott Roberts, et al -- Clinical Practices Regarding Mild Cognitive Impairment (MCI) Among Neurology Service Providers (Funder: Alzheimer's Association)
Presentation #: S4-04-06; Speaking Time: 7/15/2009, 11:45 - 12:00 PM
Dimebon®, A Clinically Promising Drug For Alzheimer Disease, Regulates Amyloid-Beta Metabolism In Cultured Cells, In Isolated Nerve Terminals, And In The Interstitial Fluid Of The Living Rodent Brain
Sam Gandy1,2, John Cirrito*3, John Steele*1, Soong Ho Kim*1, Gopal Thinakaran4, David Westaway5, Paul Fraser6, Peter St George Hyslop6, Mary Sano1,2, Ilya Bezprozvanny7, Michelle E. Ehrlich1, David M. Holtzman3
1Mount Sinai School of Medicine, New York, NY, USA; 2James J Peters VA Medical Center, Bronx, NY, USA; 3Washington University, St Louis, MO, USA; 4University of Chicago, Chicago, IL, USA; 5University of Alberta, Edmonton, AB, Canada; 6University of Toronto, Toronto, ON, Canada; 7University of Texas Southwestern, Dallas, TX, USA.
Disclosure Block: S. Gandy, Forest; Wyeth, Elan, Amicus, Diagenic, Epix.
Background: Recent evidence indicates that the retired Russian antihistamine Dimebon® (dimebolin) improves cognitive function in aged rodents and in humans suffering from mild to moderate Alzheimer disease (AD). A recent screen against a set of biochemical targets indicated that Dimebon® inhibits alpha-adrenergic receptors (alpha-1A, alpha-1B, alpha-1D, alpha-2A), histamine H1 and H2 receptors, and serotonin 5-HT 2c, 5-HT 5A, and 5-HT 6 receptors with high affinity (Wu et al., Molec Neurodeg, 2008, 3: 15doi:10.1186/1750-1326-3-15). Dimebon® has also been shown to modulate Ca2+ flux, apoptosis, and mitochondrial stability.
Objective: Given the clinical benefit, and given the known modulation of A-beta metabolism by neurotransmitters and by mitochondrial function, we assessed the ability of Dimebon® to modulate levels of APP metabolites including A-beta in a series of in vitro and in vivo experimental systems.
Methods: Under control conditions or following Dimebon® treatment, we measured A-beta levels in either: (1) the conditioned media of SweAPP-overexpressing cultured N2a mouse neuroblastoma cells; (2) the releasate from isolated nerve terminals from TgCRND8 mice overexpressing Swe/Indiana APP, or (3) the interstitial fluid (ISF) of the brains of freely moving Tg2576 SweAPP-overexpressing transgenic mice.
Conclusion: Acute treatment with Dimebon® increased A-beta levels in the releasate from TgCRND8 nerve terminals and in the ISF of freely moving Tg2576 transgenic mice. In media conditioned by SweAPP N2a cells overnight in the presence of drug, Dimebon® either had no effect on A-beta or lowered A-beta. Since questions have been raised regarding the nature of Dimebon® preparations, we performed these studies using Dimebon® from two independent vendors; both gave similar results. Elevation of A-beta release from isolated nerve terminals and elevation of ISF A-beta levels are unexpected phenomena to associate with a clinically beneficial AD drug. Further study is required to elucidate the molecular mechanism underlying the acute regulation of A-beta metabolism by Dimebon®. Chronic Dimebon® exposure also merits study. Dimebon® may be a useful chemical probe for advancing our understanding of the role of A-beta in AD and for identifying unexplored druggable mechanisms in the molecular pathogenesis of AD. (Supported by Cure Alzheimer's Fund and National Institute on Aging.)
These authors contributed equally.
Presentation #S4-04-08; Speaking Time: 7/15/2009 12:15 - 12:30 PM)
Immunotherapy Targeting Pathologically Phosphorylated Tau In A Tauopathy Mouse Model
Moran Boimel1, Nikolaos Grigoriadis2, Athanasios Lourbopoulos2, Ester Haber1, Oded Abramsky1, Hanna Rosenmann1
1Hadassah Hebrew University Medical Center, Jerusalem, Israel; 2AHEPA University Hospital, Thessaloniki, Greece.
Contact e-mail: email@example.com
Disclosure Block: H. Rosenmann, None.
Background: It has now become clear that amyloid immunization, while displaying clearance of amyloid, not only caused neuroinflammation, but did not improve cognitive impairment (and did not reduce the neurofibrillary-tangles (NFTs)). As NFTs are the best correlate with dementia, targeting the NFT pathology seems to be a preferential goal. As an aggregated protein, tau in the NFTs - seems to be a candidate for immunotherapy. Yet, the encephalitogenicity of full-length tau recently reported by us (Arch eurol, 2006) demands to selectively target pathological tau and address both, efficacy and safety.
Objective: Here we set up to specifically target pathologically phosphorylated (P)-tau conformers by immunizing NFT-mice with NFT-related P-tau peptides, using an immunization protocol aimed to predispose a proinflammatory milieu in CNS, similarly to what we used when the neurotoxicity of tau rotein was detected (i.e., the use of complete-Freund's-adjuvant (CFA) with pertussis-toxin (PT)).
Methods: We immunized NFT-mice with a mixture of three tau-peptides phosphorylated at five residues characteristic of NFT-pathology with CFA and PT. Clinical, immunological and pathological evaluations were performed.
Results: Anti-P-tau Abs were detected in sera of tau-immunized mice. However, no neurological deficits were noted following P-tau-immunotherapy for at least 8 months. Reduced NFT-burden (~40%; p<0.001) was noticed in the brains and spinal cords of immunized animals relative to controls, as indicated by Gallyas-staining and with AT8- and AT180-immunohistochemistry This was accompanied with an increase (~20%; p=0.01) in microglial burden as indicated by lectin staining.
Conclusion: Our results show: 1. A decreased NFT-burden following P-tau-immunotherapy. This is in accord with Asuni et al. (2007) who used a similar approach of immunizing mice against NFTs, yet with a different P-tau immunogene and immunization protocol (without CFA+PT). 2. Presence of anti-P-tau Abs in the sera of immunized mice with no evidence of clinical deficits, indicating that these specific P-peptide-immunogens used by us are not encephalitogenic, in contrast to the encephalitogenicity of full-length tau, demonstrated by us previously. This anti-NFT effect induced by immunotherapy targeting pathologically phosphorylated tau, together with the lack of encephalitogenicity of these P-peptide-immunogens, points to the therapeutic anti-NFT potential of P-tau-immunotherapy.
Presentation #S4-04-04; Speaking Time: 7/15/2009, 11:15- 11:30 AM
Clinical Practices Regarding Mild Cognitive Impairment (MCI) Among Neurology Service Providers
Scott Roberts1, Wendy Uhlmann1, Ronald Petersen2, Jason Karlawish3, Robert C. Green4
1University of Michigan, Ann Arbor, MI, USA; 2Mayo Clinic, Rochester, MN, USA; 3University of Pennsylvania, Philadelphia, PA, USA; 4Boston University Schools of Medicine and Public Health, Boston, MA, USA.
Contact e-mail: firstname.lastname@example.org; Jason.Karlawish@uphs.upenn.edu
Disclosure Block: J. Karlawish, None.
Background: MCI is a research categorization that is entering clinical practice, but little is known about how it is being used.
Objective: To assess how neurologists are diagnosing and treating patients with mild cognitive symptoms and how they view MCI as a clinical diagnosis.
Methods: Members of the Geriatric and Behavioral Neurology sections of the American Academy of Neurology (AAN) were surveyed by the AAN Survey Department via mail and Internet.
Results: Four hundred twenty providers (response rate = 48%) completed the survey. 88% reported at least monthly encounters with patients experiencing mild cognitive symptoms. Most respondents recognize MCI as a clinical diagnosis (90%) and use its diagnostic code for billing purposes (70%). When seeing this population, most respondents report routinely making recommendations for monitoring and follow-up (88%), counseling patients on physical (78%) and mental exercise (75%), and communicating about risk of dementia (63%). Relatively few respondents routinely provide information on support services (27%) or a written summary of findings (15%). Most (70%) prescribe cholinesterase inhibitors at least sometimes for this population, with memantine (39%) and "other" agents (e.g., vitamin E, gingko) prescribed less frequently. Respondents endorsed several benefits of making a clinical diagnosis of MCI: 1) labeling the problem is helpful (91%); 2) involving the patient in planning for the future (87%); 3) motivating the patient's risk reduction activities (85%); 4) helping the family with financial planning (72%); and 5) prescribing medications useful for treating MCI (65%). Some respondents noted potential drawbacks of MCI as a clinical diagnosis, including 1) it is too difficult to diagnose accurately or reliably (23%); 2) it is usually better described as early AD (21%); and 3) a diagnosis can cause unnecessary worry (20%).
Conclusion: Patients with MCI are commonly seen by neurologists and prescribed various medications to address their symptoms. The MCI concept is generally viewed as a useful diagnostic category in clinical practice. Clinicians vary significantly in the education and support they provide or recommend for MCI patients, suggesting a need for practice guidelines in this area. Future research is needed to illuminate decision-making around MCI treatment. (Funding source: Alzheimer's Association)