Help could be on the way for cancers previously deemed untreatable: an experimental drug targets not only tumors but also how they spread through the body.

Donald McDonald of the University of California at San Francisco and his colleagues found that when the cancer fighting drug Cabozantinib, or Cabo, was given to cancerous mice, the rodents lived to see the end of the 20-week experiment period, whereas none of those that received a placebo did.

Cabo first chokes off a tumor’s blood supply by blocking a molecule on the surface of its blood vessels, called vascular endothelial growth factor receptor (VEGFR). At the same time, it blocks a second receptor called c-MET that would otherwise allow cancer cells spread to new tissue in the body.

Since cancers starved of blood may become more aggressive and likely to spread, McDonald’s research could mean existing drugs used to cut off a tumor’s blood supply might be complemented by giving patients a drug that blocks the c-MET receptor as well.

But even without the drug combination, Cabo alone is having great success in human trials. In one such experiment, after over 100 men with prostate cancer that had spread to their bones completed a three month course of Cabo, 82 of the men saw the cancerous lumps on their bones either shrink or completely disappear, while tumors grew in only three of the study participants.

“It was a stunning effect,” says Dana Aftab of Exelixis, the company in South San Francisco, CA that is developing Cabo. Still, the company’s chief medical officer, Gisela Schwab, was quick to tell New Scientist, “[People] are not cured, but their disease is being controlled.”

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