Alzheimer's also known as presenile dementia is a neurodegenerative disorder. This disorder is characterized by abnormalities in brain that affect neurons in specific region like hippocampus and neocortex. In 1907, Alois Alzheimer, described the first case of Alzheimer's, that now bear his name. It has been analyzed by researchers that out of total population approximately 7% of people older than 65 and 40% of people over the age 50 are affected by Alzheimer disease. According to statistical data about 5 million people in United States suffer from Dementia (memory loss). Increase in dementia is mainly because of two major reasons:

• Increased life expectancy

• Post world war baby boon

It has been believed that in next 25 years number of Alzheimer's patients will be doubled. Clinical symptoms of Alzheimer's include deposition of neurofibrillary tangles and senile plaque in neocortex and hippocampus region of brain. The affected brain regions by Alzhiemer contain senile plaque in which extracellular deposit of amyloid are surrounded by dystrophic axons as well as inflammatory cells like glia. Both sporadic and familial form of Alzheimer's patient show following symptoms:

• Memory abnormalities: include memory loss or weakness.

• Problem solving: due to loss of memory patients have problem in solving small problems like their own name, etc

• Language problem: Patient has difficulty in speaking words fluently.

• Change in behavior, judgment problem

• Psychotic symptoms include: hallucination and delusion.

Abnormalities of entorhinal cortex, hippocampus, and other circuit in the medial temporal cortex of brain to presumed to be critical factors in memory impairment of Alzheimer disease. The behavior and emotional disturbances that occur in some patient may reflect involvement of amygdale and thalamus region of brain. These two regions are very important as far as learning and memory is concerned.

At present few drugs have been developed to cure Alzheimer's disease. Alterations of levels of specific protein in the serum or cerebrospinal fluid such as amyloid peptides Tau has proved to be useful in the diagnosis of Alzheimer's disease. Present day therapies focus on treating associated symptoms like depression, agitation, sleep disorder, hallucinations and delusions. One of the principal targets is the basal forebrain cholinergic system, a region of brain that is severely damaged in Alzheimer disease. Several strategies have been developed to influence this cholinergic system. Many research group and biotech companies are working strategies to prevent and ameliorate Aβ deposition and/or to influence the role of inflammatory/immune mediated processes in the disease. Till yet only few biotechnology products have reached the market of United States. Only two compounds, cholinesterase inhibitor (tacrine) and Aricept (donepexil) have been approved for the treatment of Alzheimer diseases. These two compounds prevent the breakdown of acetylcholine, important neurotransmitter of brain.

Role of Biotechnology:-
Several biotech companies are working on the correct drug for treatment of Alzheimer. CX516, one type of Ampakines, have reached phase II of clinical trials. This drug was first discovered by cortex pharmaceuticals. Two new products discovered by biotech companies are as follows:

AN-1792: this vaccine is in development and has a potential to treat AD patients. The vaccine is developed by Élan and American home products corporation. This vaccine works by stopping the production senile plaques in the brain region like hippocampus and neocortex. It also helps in reducing the pre-existing plaques. This drug will take more time to work properly on human models and take good position in the United States market.

Phenserine: this is an acetyl cholinesterase inhibitor and is discovered by Axonyx. The phase I clinical trial of this drug showed that it inhibits the activity of acetyl cholinesterase activity.

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