The disappointing failure in late-stage trials of Pfizer and Medivation's Dimebon last week is a major setback, but the plethora of other drugs in development are cause for optimism for Alzheimer’s sufferers.

That is the view of Ben Greener, lead healthcare analyst at Datamonitor, who says that the data which showed that Dimebon (latrepirdine) failed to achieve clinical benefit over placebo in one of its Phase III trials “came as a surprise to many of those that had been tracking the drug’s progress”. The drug had shown great promise in Phase II, and was “purported to be a future blockbuster”, he notes, but acknowledges that those results were limited by “a small sample size, involvement of just one geographical location (Russia) and the use of only one language to communicate disease severity”.

However, Mr Greener claims that one positive to come out of the failure is that “there will not be significant ramifications for other drugs in development for Alzheimer's”. Unlike Dimebon, the majority of other pipeline candidates are targeted towards “the hypothesised Alzheimer's etiology”, he says, noting that the focus “has shifted from neurotransmitter replacements to biological agents that affect beta-amyloid and tau protein, both hallmarks of the disease”.

The next “eagerly awaited compound” for which Phase III results will be announced is likely to be bapineuzumab, Johnson & Johnson/Pfizer’s humanised monoclonal antibody for beta-amyloid. However, Mr Greener says, “given the high attrition rate in the pipeline, expectations will be tempered”.

He states that there are just four drugs available to Alzheimer’s sufferers and they “only offer a modest symptomatic effect”. Indeed, excluding reformulations, no new drugs have been launched since Forest/Merz/Lundbeck’s Namenda (memantine) arrived in 2002. Since then, around 20 products have failed Phase III trials, Mr Greener said.

Given this, he concludes by saying that “the news about Dimebon may not be such a surprise after all”. However he insists the future looks bright as investment into Alzheimer's R&D “continues to grow exponentially and, ultimately, this is the best news for sufferers: it is only a matter of time before an effective therapy arrives”.