Ebola Drug Works Against West African Strain in Study of Monkeys
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Version 0 of 1. A study in monkeys offers the first evidence that a leading drug developed to fight Ebola works against the strain causing the current outbreak in West Africa. Six animals were infected with a very high dose of the virus and then, three days later, half were given the drug, TKM-Ebola-Makona, which was designed specifically to fight the West African strain. The monkeys that received the drug survived, but all three untreated monkeys died, researchers reported on Wednesday in the journal Nature. TKM-Ebola-Makona is already being tested in Ebola patients in Sierra Leone, but results are not yet available. An earlier version of the drug, created to treat a slightly different strain, was given to several Ebola patients in the United States, but it was impossible to tell whether it helped them because they also received other treatments at the same time. The drugs are given intravenously and can cause flulike symptoms, including headaches, chills and fever. They belong to a category called short interfering RNAs, or siRNAs, which work by blocking certain genes in the virus, impairing its ability to replicate. The design of these drugs varies depending on the genetic sequence of the virus. But viruses can mutate, and new strains can evolve. Researchers have wondered whether a drug made to treat one strain would also work against other strains of the same virus. “There has been concern that small changes in sequence can impact treatments,” said Thomas W. Geisbert, an Ebola expert at the University of Texas Medical Branch in Galveston and the senior author of the report. The original TKM-Ebola was created to fight the Kikwit strain, from an earlier outbreak. The new strain, Makona, is closely related but not identical. Lab tests show that the drug for Kikwit works against Makona, and vice versa, but Dr. Geisbert said, “The best results would probably be to use siRNAs specific for each strain.” The great advantage of the technology, Dr. Geisbert said, is that the drugs can quickly be retooled to keep up with changes in the virus. Dr. Geisbert was one of the main inventors of the siRNAs for Ebola and holds a patent on them but receives no royalties, he said. Other authors of the report included employees of Tekmira, the Canadian company that makes the drugs. An Ebola expert not involved in the study, Dr. Daniel Bausch, a senior consultant to the World Health Organization and an infectious-disease specialist at Tulane University, said, “They showed universal protection in a highly lethal model three days after infection, so that’s obviously good.” Because the epidemic in West Africa is waning, the study of TKM-Ebola-Makona in Sierra Leone may not enroll enough patients to determine whether the drug works in humans, Dr. Bausch said. He added, “Which, of course, is a good thing that we hope will continue.” |