By Don Finley
San Antonio Express-News
March 1, 2012
Two off-the-shelf cancer drugs blocked the deadly Ebola virus from reproducing in the test tube — an early, promising advance in a disease and potential biological weapon with no approved treatments or vaccine, scientists report.
Testing of the drugs took place in the biosafety level-4 lab at Texas Biomedical Research Institute, in collaboration with government scientists and researchers in Houston and Atlanta.
The two leukemia drugs, nilotinib and imatinib, don’t attack the virus directly, but instead target the patient’s own infected cells, preventing the virus inside from reproducing and escaping.
“That’s a concept that’s been attractive for antiviral therapy, because if you can target a cellular protein that’s required for the virus, it makes it a little harder for the virus to mutate to develop resistance,” said Dr. Gary Nabel, director of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases, which led the study published today in Science Translational Medicine.
And while the drugs didn’t completely clear the virus, researchers say what they’ve learned from outbreaks of the disease in Africa show that those with low levels of the virus in their bodies often survive.
The hope would be that a short-term course of treatment with the drug might eliminate enough of the virus that the patient’s own immune system could eliminate the rest.
“Often in this disease if you can just shave a little bit of the viral load off of the infection, if you can just lower it tenfold even, that’s what’s going to give people a chance to survive it,” Nabel said. “That’s really what we’re aiming to do.”
Nabel cautioned the work is early but promising, and that the next step is to test it in animals. Because Ebola outbreaks in nature are so infrequent and unpredictable, it makes human testing almost impossible, researchers say.
Government rules will allow approval of vaccines and treatments in such cases if they demonstrate effectiveness in two animal models.
Ebola hemorrhagic fever, described by the World Health Organization as often fatal and one of the most virulent viral diseases on the planet, was named for a river in the Democratic Republic of the Congo, near the location it was first identified in 1976.
It causes illness in both people and nonhuman primates, and appears sporadically in a handful of African nations.
“It’s very random,” said Ricardo Carrion, a virologist at Texas Biomed and co-author of the study. “We’re still trying to identify the reservoir. We don’t even know what maintains it in nature.”