UCSD researchers find drugs that inhibit brain-eating amoeba

SAN DIEGO — UC San Diego researchers Thursday announced they have discovered several drugs that restrain the growth of an amoeba that causes a severe brain-eating disease.

Currently there are no treatments for primary amebic meningoencephalitis and it is almost universally fatal, illustrated by the deaths of 139 of 143 known patients from 1962 to 2017. However, researchers discovered a number of drugs, including some available to the public like the breast cancer drug tamoxifen and the antidepressant Prozac, curtailed the amoeba’s growth in a petri dish.

A team of researchers led by senior author and UCSD professor Dr. Larissa Podust published their report in the medical journal PLoS Pathogens.

“Even if a drug can inhibit or kill the amoeba in a dish, it will not work in a host animal if it does not make it into the brain,” Podust said. “That’s why we started with drugs known for their brain effects.”

Podust’s team targeted a series of enzymes on the amoeba’s outer membrane, one of which is similar to a human chemical receptor generally involved in neurological conditions like addiction, amnesia and depression. Researchers tested 13 drugs that restrict the enzymes and found all of them more effective than the current treatment for primary amebic meningoencephalitis recommended by the Centers for Disease Control and Prevention, miltefosine.

For example, the amount of miltefosine it took to hinder half the growth of the amoeba is nearly 10 times the amount of tamoxifen and double the amount of Prozac it took to achieve the same outcome.

“Drug repurposing is a relevant strategy for this infection because there is little economic incentive for the pharmaceutical industry to develop new drugs to treat these rare diseases,” said co-first author Dr. Anjan Debnath. “Already-approved drugs can also lessen the time and expense required to develop a drug from the laboratory to the clinic.”