This is the one case I know of in which the placebo performed better than the drug for Alzheimer's disease.
06 Jun 2014
On June 4, AFFiRiS AG offered a smattering of results from its Phase 2 clinical trial of AD02, an active vaccine for Alzheimer’s disease derived from the company’s proprietary method of making synthetic antigens based on the Aβ peptide. At a press conference in Vienna, company scientists reported that among older people with early Alzheimer’s, a placebo group fared better than any other. Patients in this group reportedly had less cognitive decline over the course of 18 months, correlating with less hippocampal shrinkage. This group had been injected not with any Aβ-based antigen, but only with what the company calls an immunomodulator that was part of the AD02 formulation. Company scientists then renamed this placebo formulation AD04, and said they planned to explore options for clinical development. The therapeutic that was the object of the trial, AD02, did not work.
The placebo contained a compound (keyhole limpet hemocyanin) which is an antibody against tyrosine nitration which is a major aspect of Alzheimer's disease (tyrosine nitration reduces the synthesis of acetylcholine which is needed for short-term memory, prevents the clearance of amyloid and hyperphosphorylated tau, reduces blood flow in the brain, and prevents the regeneration of neurons). The drug also contained this compound so maybe there was a problem with the mechanism of action of the drug itself.
The chances that the placebo in the pbt2 trial contained a useful compound seems unlikely as you would expect it to positively affect a large number of participants. However, separate from the placebo, the outliers may have been doing something (moderate exercise?) or been using some external antioxidant (either through diet or supplements--for instance, polyphenols also inhibit tyrosine nitration) that reduced brain atrophy and amyloid levels. It may be critically helpful to figure out exactly what that was.
PBT Price at posting:
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