Pfizer and Johnson & Johnson have presented disappointing results from the first of four trials of the eagerly-anticipated Alzheimer's disease drug bapineuzumab.

The drug giants have published top-line results from study 302, a Phase III trial looking at intravenous bapineuzumab in patients with mild-to-moderate AD who carry the ApoE4 (apolipoprotein E epsilon 4) genotype. Clinical efficacy was not demonstrated in ApoE4 carriers (ie two primary endpoints - change in cognitive and functional performance - were not met) and the companies have decided that participants who enrolled in a follow-on extension study will no longer receive doses of bapineuzumab, an antibody that targets beta-amyloid.

Steven Romano, head of the medicines development group at Pfizer, said that "while we are disappointed in the topline results of study 302, a more complete understanding of bapineuzumab and its potential utility in mild-to-moderate AD will be gained following the availability of additional data". This will include data from the soon-to-be available non-carrier study 301,”he added, noting that "we recognise that AD is very complex", but Pfizer and J&J "remain committed to advancing the science of the disease".

Data from both the studies have been accepted as a late-breaker and will be presented in September at the European Federation of Neurological Societies meeting in Stockholm.

In a research note, Tim Anderson at Sanford Bernstein said that Alzheimer’s drugs “could be the next Lipitors - in terms of their size - should they work,” but bapineuzumab and similar drugs have been viewed as “highly likely to fail and so far this assumption has been correct". He believes that the probability of success for investigative AD drugs stands at around 20%, adding that the initial bapineuzumab results "will naturally make investors more skeptical than they already are".