Bapineuzumab, an experimental drug for Alzheimer's disease patients drug has passed its Phase II trial and now moves on to a huge final phase three testing. If the drug proves successful, it could be on the market in four years, Wyeth and Elan, the makers of bapineuzumab said.

Bapineuzumab is designed to fight beta amyloid, a toxic protein that clumps together in the brains of Alzheimer's patients. The drug was seen to slow down the disease progression in early studies, conducted on 240 American subjects with early- to moderate-stage Alzheimer's disease.

The tests, including the MRI's measured functions including recall, language and the ability to manipulate objects and revealed that the patients showed less loss of brain volume over time compared with patients who received a placebo.

However, the bad news is that bapineuzumab doesn't work for everybody. Alzheimer patients that were diagnosed with a genetic variation called ApoE4 haven't presented any improvement in cognitive functions during treatment, eFlux Media reports.

The patients with this set of gene make up for 30 to 60 percent of all the Alzheimer diagnosed persons. Also, such people are the most likely ones to develop the disease. The drug could be the world's first drug to modify the course of Alzheimer's, the most common cause of dementia, rather than just relieving its symptoms.