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Lithium for Alzheimer Prevention: What Are We Waiting for?

Lithium for Alzheimer Prevention: What Are We Waiting for?

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RESEARCH UPDATE

Imagine a drug company working on a pill to prevent progression to Alzheimer dementia for patients at high risk. Imagine that their animal studies show benefit in preventing neurodegeneration, reducing 2 of the major changes known to lead to Alz­heimer disease: tau protein phosphorylation and amyloid plaque formation. Imagine that their new drug had been shown to inhibit these 2 changes in humans, in a preliminary trial; and that so far, there were no known risks of their new medication, and no side effects in over 90% of patients.

Wouldn’t some patients and their families be interested in getting hold of this drug, even as formal clinical trials were getting underway?

That would surely be the case if the drug was already known to carry very low risk and unlikely to produce significant side effects. Because what else is there to do, when a patient and his or her family are facing likely decline into a progressive series of losses and stress—with no hope of reversing the process?

When such a drug was shown to have the desired effect in even a small sample of patients who already exhibited very early signs of the illness—to a greater extent than placebo—well, that would begin the stampede, would it not? The company would be besieged with requests that would likely soon turn into demands for humanitarian release of their new product, based on the extremely large number of adults at very high risk for Alzheimer disease in the next decade.

There would be calls for prudence: “This is just one trial; we need a replication.” That call would be drowned out by objections: “What else do you think we are going to do? If there’s even a 1% chance this could work, we’re ready to take it. Even if there was significant risk, we’d be ready to take it: why not? Why just wait for an inevitable decline?”

As you’ve surely gathered, there is indeed a randomized trial that shows lithium prevented cognitive worsening in patients with minimal cognitive impairment (MCI).1 The dose was roughly 1.5 mg of lithium carbonate per day: microdose lithium.1 Yet when one of my patients with MCI, who has been taking 300 mg/d of lithium for more than 5 years, was evaluated by a university dementia research program (he was debating whether to enter one of their clinical trials), they pooh-poohed the lithium. His blood level was 0.1 mEq/L. Not enough data to support this approach, they said—and they’re not alone in their opinion.2 I cannot understand this logic: what else have we got to offer? But new data may further tilt the balance.

The same Brazilian research group who performed the human trial has recently shown, in mice genetically engineered to have an equivalent of early Alzheimer disease (early development of amyloid plaques with attendant cerebrovascular, cognitive, and neuroinflammatory pathologies), that microdose lithium in their water supply prevented progression to disease to a dramatic extent.3 In addition to demonstrating that lithium attenuated the deleterious brain changes in the genetically engineered animals, they also found that the treated animals’ behavior was no different from that of “wild type” mice (ie, those not genetically altered).

This may strike you as backward: why the human study first, then the animal study? Answer: the group is working on demonstrating the value of lithium as a preventive agent in patients at risk for Alzheimer disease. Their first study in humans used low-dose lithium (blood levels of 0.25 to 0.5 mEq/L).4 Their follow-up human study used the microdose referenced above. They had to go back and show, in mice, that microdoses produced the same brain benefits seen in earlier mouse studies with larger doses.5

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