Allopregnanolone is an experimental treatment for Alzheimer’s disease that is being developed by Roberta Diaz Brinton, PhD, of the University of Arizona, the University of Southern California, and the National Institute on Aging. Allopregnanolone is a neurosteroid that may help generate new brain cells.

How allopregnanolone works

The exact cause of Alzheimer’s disease is unknown, but the disease leads to the death of brain cells and decreased connectivity between them. It is believed that this may be due to the accumulation of certain proteins in the brain. One of these proteins is beta-amyloid, which forms clumps called plaques.

Allopregnanolone is formed naturally in the brain when the hormone progesterone is broken down. Both women and men produce progesterone and allopregnanolone. A study has shown that Alzheimer’s patients have lower levels of allopregnanolone in their brains compared to people with healthy brains.

In mice, allopregnanolone has been shown to increase the generation of new brain cells from neural stem cells, reduce the formation of beta-amyloid plaques, and improve cognitive function. It is hoped that allopregnanolone can also help reverse the effects of Alzheimer’s.

Allopregnanolone in clinical trials

A small Phase 1 clinical trial (NCT02221622) is evaluating the safety and tolerability of allopregnanolone in mild cognitive impairment and early Alzheimer’s disease. The primary goal of the study is to determine the maximum tolerated dose of allopregnanolone. Participants will receive one of three doses of allopregnanolone or a placebo. Vital signs, adverse events, and brain MRI will be followed over 16 weeks. The trial is still recruiting participants in California.

Brinton is preparing to start a larger, Phase 2 clinical trial with the support of the Alzheimer’s Drug Discovery Foundation (ADDF).


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