Lancet: PiB PET assesses potential treatment for Alzheimer's disease

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An article published online March.1 in Lancet Neurology suggests 11C-PiB PET imaging is useful in assessing drugs for Alzheimer's disease and has shown that a new investigational drug, bapineuzumab (Elan Pharmaceuticals and Wyeth Research), reduces beta-amyloid deposits in the brain in patients who have mild-to-moderate Alzheimer's disease.

The radiotracer 11C-PiB, binds to beta-amyloid plaques which is about two times greater in areas of the cerebral cortex in patients with Alzheimer's disease compared to healthy controls.

In this phase 2 study, Juha Rinne, MD, PhD, professor, Turku PET Centre, University of Turku and Turku University Hospital,  Finland and colleagues investigated whether bapineuzumab could reduce amyloid-? load measured using 11C-PiB PET imaging in cortical areas in patients with Alzheimer's disease.

28 patients with mild-to-moderate Alzheimer's disease were randomly assigned in the study to receive one of three doses of bapineuzumab (0.5, 1.0, 2.0 mg/kg) or placebo by intravenous infusion every 13 weeks for up to six infusions. 11C-PiB PET scans were done at the start of the study and at weeks 20, 45, and 78, according to Rinne and colleagues.

The authors estimated that bapineuzumab treatment was associated with about a 25 percent reduction in beta-amyloid load over 78 weeks compared with placebo. The difference in 11C-PiB retention between the bapineuzumab and placebo groups was similar for each of the three doses, and the treatment difference increased over time, suggesting that greater differences in 11C-PiB retention might be possible with extended treatment. Bapineuzumab treatment was generally well tolerated and adverse events were mild to moderate, Rinne and colleagues noted.

In an accompanying comment, Sam Gandy, MD, PhD, Mount Sinai professor of Alzheimer's disease research, Mount Sinai School of Medicine, New York City, says that these findings: "report something of a breakthrough by demonstrating the feasibility of eventually testing the so-called amyloid hypothesis of sporadic Alzheimer's disease in vivo." He points out that although it is too early to say that we have effective disease-modifying drugs, these new data about bapineuzumab "[m]ove us closer to the goal of understanding, treating, and eventually preventing major neurodegenerative diseases such as Alzheimer's disease."

"This technique offers the opportunity to test more directly the beta-amyloid hypothesis by confirming the ability of a particular drug to reduce or prevent beta-amyloid accumulation and to assess the effect this has on clinical outcomes," concluded Rinne and colleagues.