Current therapies for Alzheimer's disease only treat the symptoms of the disease. We have previously developed a novel monoclonal antibody, 2B3, which binds to the β-secretase cleavage site in amyloid precursor protein (APP) and reduces the production of amyloid-β (Aβ) in human cell lines. To determine whether the antibody was likely to be effective in mouse models of amyloid pathology in vivo, we investigated whether 2B3 could also bind to APP in mouse primary cortical neurones. Primary cortical neurones were produced from E15.5-17.5 C57Bl/6 wild-type and transgenic APP/V717I (London mutation) embryos. The percentage of the neuronal population was determined by immunocytochemistry. Cells were treated with 10 μg/ml 2B3 or an irrelevant IgG for 48 h and Aβ40 levels determined by ELISA. The population of cells was found to contain over 75% neurones and 2B3 bound effectively to these cells. No differences in Aβ40 were detected between wild-type and transgenic cells. Importantly, 2B3 significantly inhibited the production of Aβ40 by 75.15±1.37% of the media control, whereas an irrelevant IgG only significantly reduced Aβ40 levels by 23.35±5.55% of the media control. The reduction in Aβ40 produced by 2B3 was significantly greater than that caused by the IgG. These data indicate that 2B3 binds to APP in mouse neurones and can inhibit Aβ40, similar to our previous findings. The antibody is probably therefore acting by steric hindrance of β-secretase and these data suggest that it will be effective in mice in vivo and could be an alternative potential therapy for Alzheimer's disease.