Eisai’s cancer drug Targretin clears Alzheimer’s plaques in mice

Eisai’s skin cancer drug Targretin (bexarotene) has been shown in studies to reverse the buildup of amyloid beta plaques in mice and improve their memory. Gary Landreth, senior author of the work, cautioned that while the results are exciting, the scientists must wait to see if the agent has similar benefits in humans with Alzheimer’s disease.

In the studies, the researchers gave more than 100 mice with Alzheimer-like symptoms oral doses of Targretin, which is currently approved to treat patients with skin lesions caused by persistent or recurrent cutaneous T-cell lymphoma or AIDS-related Kaposi’s sarcoma. Data showed that the RXR agonist “resulted in enhanced clearance of soluble” amyloid beta within hours, with levels dropping by 25 percent after six hours. Further, amyloid beta plaques were reduced by more than 50 percent in 72 hours.

The researchers noted that results also suggested that Targretin “stimulated the rapid reversal of cognitive, social, and olfactory deficits and improved neural circuit function,” with benefits lasting for up to three months. They added that the drug is thought to work by stimulating the production of apolipoprotein E, a protein that normally facilitates the clearance of amyloid beta.

In further work, Landreth plans to start a safety trial in a dozen patients in the next few weeks. The researchers said they hope to engineer a version of the drug that is more potent and works at a lower dose.