2 November 2011. Pfizer Inc. has halted development of ponezumab, a passive immunotherapy targeting the C-terminal end of amyloid-β (Aβ). “Based on recent data from the ongoing studies, Pfizer has decided not to initiate further development of ponezumab in mild to moderate Alzheimer’s disease at this point in time,” MacKay Jimeson, a company spokesman told ARF via e-mail. Jimeson, or other Pfizer scientists, declined to explain what prompted the company to halt development. Pfizer completed several Phase 1 trials and did not report any serious side effects. A Phase 2 trial begun in 2008 was slated for completion last August but data from that trial have not been released. A later Phase 2 trial is also expected to be finished this year. “After completing the data analysis of the studies, Pfizer will present the findings at an appropriate scientific meeting,” wrote Jimeson.
Ponezumab is a humanized mouse monoclonal antibody that does not seem to penetrate the brain efficiently. At a meeting in Uppsala last May, Brendon Binneman, from Pfizer, suggested that the antibody works as a peripheral sink, mopping up Aβ in the circulation and aiding clearance from the brain (see ARF related news story). In that respect, it might function similarly to the Eli Lilly antibody solanezumab, which is in Phase 3 development (see ARF related news story). In other regards, however, such as IgG class, and which forms of Aβ the antibody primarily recognizes, the two antibodies apparently differ.
Ponezumab/PF-04360365 was initially developed as RN1219 by Rinat Neuroscience, a California biotechnology company. Pfizer acquired Rinat for a reported several hundred million dollars in 2006 (see New York Times story), in part to develop this therapeutic antibody.—Tom Fagan.