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New drug shows early promise in small Alzheimer's trial

A drug called PBT2, developed by Australian company Prana Biotechnology, appears to improve cognitive abilities in patients with early-stage Alzheimer's disease.  Researchers report in Lancet Neurology, that it was also successful in reducing protein buildup associated with the debilitating neurodegenerative illness, which plagues up to 4.5 million Americans.

Craig Ritchie, a neuroscientist at Imperial College London and Prana consultant, says that the success of the recent 12-week trial (which had 78 participants) -- must be replicated in a larger longer-term trial before the company would consider seeking approval to sell it as an Alzheimer's therapy. "Our hope is that we might be able to see treatments that can substantially improve the lives of people with Alzheimer's disease within the next five or so years," he said in a statement.

Patients in the trial took two rounds of exams to assess their cognitive abilities—one at the beginning of the treatment cycle and one after 12 weeks. The tests probed so-called executive function, organizational abilities, planning and reasoning.  Among them: how many words that fit into a certain category volunteers could fire off and how quickly they could connect related circles filled with letters or numbers on a sheet of paper.

Patients who received 250 mg of PBT2 were able to come up with three more words on the category test then they did before their treatment. Participants who received placeboes, on the other hand, performed worse on average after the 12-week period was up than they did at the outset. The treated population also connected the trails between the circles nearly 50 seconds faster than they did before receiving PBT2. The untreated group also performed more poorly on this task at the end of the trial period.

In addition to improved executive function, the treated population showed a reduction in the protein amyloid beta in their spinal fluid—a proxy measure for what happens in the brain. Amyloid beta, with the help of metals, such as zinc and copper, forms clumps called plaques around neurons or nerve cells in the brain. These plaques disrupt the cell function and can lead to cell death. PBT2 works by decreasing the level of zinc and copper, which are elevated in an Alzheimer's brain. In patients treated with PBT2, amyloid beta levels fell by 13 percent relative to the placebo group.

The researchers report no serious side effects as a result of the PBT2 treatment regimen. Norman Relkin, a neurologist at Weill Cornell Medical College in New York City, wrote in a Lancet Neurology editorial that PBT2 still needs to prove safe and effective in larger clinical trials. If it gets over that hurdle, the drug  would support a link between high levels of metals, such as zinc and copper, and Alzheimer's disease.

 

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