Justin Lowenthal, B.S., Sara Chandros Hull, Ph.D., and Steven D. Pearson, M.D.

Being on the cusp of a potential medical breakthrough for a serious disease can pose substantial ethical challenges. One current example arises from a recent study demonstrating — in a single mouse model in one laboratory — that the drug bexarotene is effective in treating Alzheimer’s disease (see article by LaFerla in this issue of the Journal, pages 570–572). Administration of bexarotene resulted in a greater-than-50% reduction of β-amyloid plaque at 72 hours and substantial reversal of neural, cognitive, social, and olfactory deficits, albeit with reduced effects as the mice aged.1 A single report of this kind of preliminary evidence will require confirmation before Alzheimer’s disease investigators even consider launching clinical trials in humans. But unlike many drugs under study for Alzheimer’s disease, bexarotene is not a novel experimental drug; it is already approved by the Food and Drug Administration (FDA) for treatment of a cutaneous form of non-Hodgkin’s lymphoma. Therefore, physicians could currently legally prescribe it for off-label indications.