The Swiss drugmaker has more than doubled the size of a clinical trial of its experimental drug gantenerumab in patients who have yet to develop dementia, putting it in the vanguard of attempts to catch the disease in its early stages.

"The playing field has changed dramatically and gantenerumab is now the most advanced monoclonal antibody in early Alzheimer's and the next big news to read out in this space," Luca Santarelli, Roche's head of neuroscience, said in an interview.

A successful Alzheimer's treatment could reap multiple billions of dollars in annual sales. However, many experts believe that treatment would have to be delivered before patients show signs of dementia because brain damage may be irreversible after that point.

"We targeted this space four years ago and our trial started at the end of 2010, so we are way ahead," Santarelli said.

Results from the study in early, or prodromal, Alzheimer's patients who do not yet have dementia are expected in 2015. The decision to increase the number of patients to 770 from 360 has made it a pivotal, or final-stage Phase III, trial.

While the project is high-risk and the approach unproven, Roche is hopeful that it will see an effect because previous brain scan tests have shown that gantenerumab can reduce amyloid plaques in the brain, which are linked to Alzheimer's, more rapidly than other drugs.

If the results are very strong, Roche may be able to file for marketing approval based on a single trial, given the high medical need, though regulators normally require further tests.

Roche has three other drugs in clinical tests, including crenezumab, which has been chosen for a U.S. government-backed trial in a group of Colombians with a genetic mutation that leads to Alzheimer's in their forties.

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The failure of rival antibody drugs bapineuzumab, from Pfizer Inc, Johnson & Johnson and Elan Corp, and solanezumab, from Eli Lilly and Co, has dashed hopes for an immediate breakthrough against Alzheimer's.

Both drugs were tested in patients who already had dementia.

Details of the unsuccessful trials with bapineuzumab will be presented at a medical conference in Stockholm on Tuesday, while results with solanezumab - which showed interesting but inconclusive signs of improvement in patients with mild disease - will be set out at a meeting in Boston on October 8.

The tentative signs of an effect with solanezumab has prompted some industry analysts to suggest that it could be an option for patients with mild Alzheimer's or in the early stages of the disease. However, this would almost certainly require further trials, which would take about three years.

Santarelli said that a key strength of his team's approach with gantenerumab, which is partnered with Morphosys AG, was the decision to set rigorous selection criteria for patients, including diagnostic testing of spinal fluid.

The Roche study uses both cognitive testing and sampling of spinal fluid to ensure that all patients in the trial truly have pre-symptomatic Alzheimer's and not some other memory problem.

The decision to link treatment to a diagnostic test follows the highly successful pattern adopted by Roche in cancer medicine, where it is the world leader in terms of sales.

That makes it a somewhat onerous process for patients, who have to undergo a lumbar puncture, though Santarelli said that this had not discouraged patients who are aged 50 to 85 and have memory problems.

"I had some skepticism, but it turns out the mandatory lumbar puncture is not a major hurdle in recruiting patients," he said.

(Editing by David Goodman)

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