The firms say that the study did not attain statistical significance in the overall study population. However, post-hoc analyses did show statistically significant and clinically meaningful benefits in important subgroups.

"The preliminary analyses of the Phase 2 study are a continued validation of the amyloid approach to Alzheimer's disease and an important milestone in our companies' ongoing commitment to bring new treatment options to patients," saidKelly Martin, President and CEO of Elan."These results clinically support our decision to move into Phase 3 last year."

"We are encouraged by these findings. We remain driven by science and focused on patients as we work to bring this treatment to those who desperately need new options," said Bernard Poussot, President and CEO, Wyeth. "We recognize there is a great deal of hard work left as we move from this phase of learning towards confirming the potential of bapineuzumab."

Elan and Wyeth plan to continue all four studies in the previously disclosed in the bapineuzumab Phase 3 clinical program and will review and discuss these data with regulatory authorities and leading medical experts.