Conference Coverage

Gum bacteria and Alzheimer’s: A hypothesis inches forward



– Scientists testing an unusual hypothesis about the pathogenesis of Alzheimer’s disease say that use of an experimental antimicrobial drug to target a common oral infection was associated with biomarker improvements in people with the disease.

At the Alzheimer’s Association International Conference, Michael Detke, MD, PhD, of Cortexyme in South San Francisco, Calif., presented findings from a small cohort (n = 9) of people with mild to moderate Alzheimer’s disease (AD).

Six patients, mean age 72, were randomized to 4 weeks’ treatment with an agent called COR388, which inhibits toxic proteases produced by Porphyromonas gingivalis, a bacterium that colonizes the mouth and gums and has been found in the brains and cerebrospinal fluid of people with AD more than in non-AD patients. Another three subjects were randomized to placebo.

At 28 days, the CSF levels of an Alzheimer’s-associated apolipoprotein E (ApoE) fragment and serum levels of RANTES, a chemokine associated with chronic inflammation, were reduced from baseline by about one-third in treated subjects, compared with placebo subjects (P less than .05).

“In AD, ApoE is known to be fragmented and the fragments are known to be neurotoxic,” Dr. Detke, the lead study author, said in an interview. “We hypothesized that these P. gingivalis proteases may be acting on ApoE cleavage – so if you bind the proteases you should reduce the fragments. We saw in this study that ApoE fragment was reduced by 30%, or back to about normal levels.”

It is difficult to eradicate P. gingivalis infection using conventional antibiotics. The experimental agent COR388 “does not kill the bacteria but rather neutralizes it by binding to the proteases it produces, making the bacteria benign,” Dr. Detke said.

While hypotheses involving infectious causes of Alzheimer’s remain on the periphery of dementia research, Dr. Detke and his colleagues will soon be able to test theirs in a more meaningful way. At the conference, Dr. Detke presented detailed plans for a phase 2/3, placebo-controlled, clinical trial of COR388 in 570 patients aged 55-80 with mild to moderate AD.

Patients in the study are currently being randomized to 48 weeks of treatment with one of two doses, or placebo, with cognitive and biomarker endpoints planned, including for amyloid-beta, tau, and serum, plasma, and CSF markers of neuroinflammation.

Dr. Detke is an employee of Cortexyme, as are another 8 of the study’s 11 authors.

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