Alzheimer's disease research

As of June 2012 there were more than 330 clinical trials under way to understand and treat Alzheimer's disease. 30 of these studies were human phase three trials, the last step before U.S. Food and Drug Administration approval and marketing.

There are different approaches. One approach is to reduce Amyloid beta, for example with bapineuzumab, an antibody in phase III studies for patients in mild to moderate stage; semagacestat, a γ-secretase inhibitor, MPC-7869; and acc-001 or CAD106, vaccines against amyloid beta. Other approaches are neuroprotective agents, like AL-108 (phase II completed); or metal-protein interaction attenuation, as is the case of PBT2 (phase II completed). Yet another approach is to use general cognitive enhances, as may be the case for memantine, a pharmaceutical approved in the United States and European Union to treat moderate-to-severe AD. Finally, there are basic investigations on the origin and mechanisms of Alzheimer's disease.

Treatments in clinical development
Multiple potential treatments for Alzheimer's disease are currently under investigation, including several compounds being studied in phase 3 clinical trials. The most important clinical research is focused on potentially treating the underlying disease pathology, for which reduction of amyloid beta is a common target of compounds under investigation.

Immunotherapy to amyloid beta
Immunotherapy or vaccination for Alzheimer's stimulates the immune system to attack beta-amyloid. One approach is active immunization, which would stimulate a permanent immune response. The vaccine AN-1792 showed promise in mouse and early human trials, but in a 2002 Phase II trial, 6% of subjects (18 of 300) developed serious brain inflammation resembling meningoencephalitis, and the trial was stopped. In long-term followups, 20% of subjects had developed high levels of antibodies to beta-amyloid. While placebo-patients and non-antibody responders worsened, these antibody-responders showed a degree of stability in cognitive levels as assessed by the neuropsychological test battery (although not by other measures), and had lower levels of the protein tau in their cerebrospinal fluid. These results may suggest reduced disease activity in the antibody-responder group. Autopsies found that immunization resulted in clearance of amyloid plaques, but did not prevent progressive neurodegeneration. Vaccination:

A Phase IIA study of ACC-001, a modified version of AN-1792, is now recruiting subjects.

One Aβ vaccine was found to be effective against inclusion body myositis in mouse models.

Passive immunotherapy
Also derived from the AN-1792 immunotherapy program, there is an infused antibody approach termed a passive vaccine in that it does not invoke the immune system and would require regular infusions to maintain the artificial antibody levels. Micro-cerebral hemorrhages may be a threat to this process.

The most advanced such candidate is known as bapineuzumab or aab-001, and this antibody is designed as essentially identical to the natural antibody triggered by the earlier AN-1792 vaccine. The aab-001 antibody is in Phase 3 clinical trials for both Apolipoprotein E4 gene carriers, and Apolipoprotein E4 gene non-carriers.

Gamma secretase inhibition
Gamma secretase is a protein complex thought to be a fundamental building block in the development of the amyloid beta peptide. A gamma secretase inhibitor known as LY451039 is in Phase 3 trials.

Gamma secretase modulation
Tarenflurbil (MPC-7869, formerly R-flubiprofen) is a gamma secretase modulator sometimes called a selective amyloid beta 42 lowering agent. It is believed to reduce the production of the toxic amyloid beta in favor of shorter forms of the peptide. Negative results were announced regarding tarenflurbil in July 2008 and further development was canceled.

Metal-protein interaction attenuation
PBT2 is an 8-hydroxy quinoline that removes copper and zinc from cerebrospinal fluid, which are held to be necessary catalysts for amyloid beta aggregation. This drug has been in a Phase II trial for early Alzheimers and which has reported preliminarily promising, but not detailed, results.

Statins
Simvastatin, a statin, stimulates brain vascular endothelial cells to create a beta-amyloid ejector. The use of this statin may have a causal relationship to decreased development of the disease.

Metabolic correction
This approach is based on the prominent aspect of Alzheimer's disease, which is common for many other neurodegenerative diseases: energy deficit. It has first been noted for the case of insulin insufficiency in the brain of Alzheimer's patients. Because of that Alzheimer's disease has been called "Type 3 diabetes" and the insulin modification therapies are currently in pharmaceutical's pipelines.

Other pharmaceuticals
Several other pharmaceuticals are under investigation to treat Alzheimer's disease.

Allopregnanolone
Allopregnanolone has been identified as a potential drug agent. Levels of neurosteroids such as allopregnanolone decline in the brain in old age and AD. Allopregnanolone has been shown to aid the neurogenesis that reverses cognitive deficits in a mouse model of AD.

Angiotensin receptor blockers
A retrospective analysis of five million patient records with the US Department of Veterans Affairs system found that different types of commonly used anti-hypertensive medications had very different AD outcomes. Those patients taking angiotensin receptor blockers (ARBs) were 35—40% less likely to develop AD than those using other anti-hypertensives.

Antibiotic therapy
Only one clinical trial is being done (at McMaster University) to investigate the efficacy of antibiotic therapy. The authors of the study indicated that it was effective in delaying the progress of the disease: "In conclusion, a 3-month course of doxycycline and rifampin reduced cognitive worsening at 6 months of follow-up in patients with mild to moderate AD." A re-examination of the same data using: "...AUC analysis of the pooled index showed significant treatment effect over the 12-month period".

Several studies using minocycline and doxycycline, in an animal model of Alzheimer's Disease, have indicated that minocycline and doxycycline  exerts a protective effect in preventing neuron death and slowing the onset of the disease.

Antiviral therapy
The possibility that AD could be treated with antiviral medication is suggested by a study showing colocation of herpes simplex virus with amyloid plaques.

Cannabinoids
The endocannabinoid system may have a role in AD. For instance, THC, one of the active ingredients in marijuana, has been show to reduce amyloid beta plaque formation through inhibition of acetylcholinesterase (AChE).

Dimebon
Also in July 2008 results were announced of a study in which an antihistamine that was formerly available in Russia, Dimebon, was given to a group of AD patients. The group receiving Dimebon improved somewhat over the 6 months of the study (and this continued for the next six months), whereas those on placebo deteriorated. Unfortunately the consecutive phase-III trial failed to show significant positive effects in the primary and secondary endpoints. The sponsors acknowledged in March 2010 that initial results of the phase III trial showed that while the drug had been well tolerated, its outcomes did not significantly differ from the placebo control.

Etanercept
A 2006 pilot study showed small but significant improvements in various cognitive rating scales in patients with Alzheimer's disease after treatment with etanercept, a Tumor necrosis factor-alpha receptor fusion protein, which binds to tumor necrosis factor-alpha, and decreases its role in inflammation of nervous tissue. Etanercept was administered by perispinal infusion to 15 AD patients which resulted in sustained improvement in cognitive function; however it is not clear if this was temporary or not. A small trial consisting of 50 patients has commenced. A 12 person replication study is being run by Griffith University, Australia. A study published in 2008 of etanercept, administered to a single AD patient via perispinal infusion, showed rapid (within 10 minutes) and significant improvement in Alzheimer's symptoms that lasted until the end of the study, which involved weekly injections.

Insulin sensitizers
Recent studies suggest an association between insulin resistance and AD (fat cell sensitivity to insulin can decline with aging): In clinical trials, a certain insulin sensitizer called "rosiglitazone" improved cognition in a subset of AD patients; in vitro, beneficial effects of Rosiglitazone on primary cortical rat neurons have been demonstrated

Methylthioninium chloride
In July 2008, researchers announced positive results from methylthioninium chloride (MTC), (trade name: Rember) a drug that dissolved Tau polymers. Phase II results indicate that it is the first therapy that has success in modifying the course of disease in mild to moderate AD.

Sigma receptors
Originally considered an enigmatic protein, the sigma-1 receptor has been identified as a unique ligand-regulated molecular chaperone in the endoplasmic reticulum of cells. This discovery led to the review of many proposed roles of this receptor in many neurological diseases including Alzheimer's.

Translocator protein
A 2013 study showed that translocator protein can prevent and partially treat Alzheimer's disease in mice.

Non-Imaging biomarkers
Recent studies have shown that people with AD had decreased glutamate (Glu) as well as decreased Glu/creatine (Cr), Glu/myo-inositol (mI), Glu/N-acetylaspartate (NAA), and NAA/Cr ratios compared to normal people. Both decreased NAA/Cr and decreased hippocampal glutamate may be an early indicator of AD.

Early research using a small cohort of Alzheimer's disease patients may have identified autoantibody markers for AD. The applicability of these markers is unknown.

A small human study in 2011 found that monitoring blood dehydroepiandrosterone (DHEA) variations in response to an oxidative stress could be a useful proxy test: the subjects with MCI did not have a DHEA variation, while the healthy controls did.

A 2013 study on 202 people at the Saarland University in Germany found 12 microRNAs in the blood were 93% accurate in diagnosing Alzheimer's disease.