Scientists from Maryland’s Johns Hopkins University, in conjunction with Danish researchers, have developed a drug using a Mediterranean weed that can target tumor cells and destroy them.

The extraordinary drug travels undetected through the bloodstream until it encounters a tumor cell, where it is activated by specific proteins. It destroys the tumor cells, neighboring cancer cells, and the blood vessels that act as their supply, but spares healthy cells and blood vessels.

The drug, called G202, was tested on mice and the study was led by Samuel Denmeade, MD, professor of oncology, urology, pharmacology and molecular sciences at Johns Hopkins University. Over the course of 30 days, the human prostate tumors grown in mice were reduced by an average of 50 percent. In comparison tests with the chemotherapy drug docetaxel, G202 reduced eight of nine tumors by more than 50 percent over the course of 21 days. Docetaxel reduced only one of the nine tumors in the same amount of time.

G202 also provided the same results for human models of bladder, kidney, and breast cancers.

So far, Johns Hopkins University, the University of Wisconsin, and the University of Texas have treated 29 patients with advanced cancer with the drug in a Phase I trial. A planned Phase II of the trial will be testing liver and prostate cancers.

G202 is chemically derived from a plant native to the Mediterranean, called thapsia garganica. The plant grows a product called thapsigarnin, which has been known to be extremely poisonous. Arab traders called the plant the “death carrot” because of the swift death that would occur in camels if they ate it.

In order to avoid a similar fate in humans, the drug was modified to only be activated with a trigger. The trigger is a protein named prostate-specific membrane antigen (PSMA), which lines the cancer cells surrounding the prostate and other areas. G202 blocks cells’ receipt of the SERCA pump, a protein that maintains cells’ correct level of calcium.

Researchers, particularly Denmeade, do not believe that cells will develop immunity to the drug, because all cells need that protein to live.

The drug seems to have no recorded side effects so far.

The results of the study have been published in Science Translational Medicine.