Experimental Drug Saves Monkeys Stricken With Ebola

Aug 29, 2014
Originally published on August 29, 2014 8:40 pm

Scientists are reporting strong evidence that the experimental Ebola drug ZMapp may be effective for treating victims of the devastating disease.

A study involving 18 rhesus macaque monkeys, published Friday in the journal Nature, found that the drug saved 100 percent of the animals even if they didn't receive the drug until five days after they had been infected. The study is the first to test ZMapp in a primate, which is considered a good model for how a drug might work in humans.

"I think it's significant and a very important step forward in the fight against the Ebola virus," Gary Kobinger of the Public Health Agency of Canada, who led the study, told reporters during a telephone briefing Friday.

Kobinger and others cautioned that it remains unclear how well the drug might work in humans, but the findings are encouraging. "I think it strongly supports that concept," said Kobinger, stressing that this was still "speculative."

Kobinger noted the animals that were saved in the study were days — perhaps even hours — away from dying when they received the drug, and had been exposed to higher levels of the virus.

"We could rescue animals who had advanced disease," he said. That suggests the drug might be able to save people up to 11 days after becoming infected, he said.

ZMapp is a combination of three types of proteins known as antibodies, which the immune system typically produces in response to an infection. In this case, the antibodies against Ebola were created in the laboratory and produced using genetically engineered tobacco plants.

The drug has already been used on a handful of victims of the current Ebola outbreak raging in West Africa, including two American missionaries who recovered. But doctors say it's unclear what role ZMapp may have played, if any. At least two other Ebola victims who received ZMapp, including a Spanish priest and a Liberian doctor, died.

But Mapp Biopharmaceutical Inc. of San Diego, which developed the drug, has said it has exhausted its inventory. It would take months to produce any significant new supplies. So it remains unclear how much of a role the drug could play in the current outbreak, even if it proves to be effective in humans.

Nonetheless, Kobinger and others say the results are significant in the fight against Ebola. Despite many years of trying, there currently are no drugs or vaccines that have been shown to be effective for preventing or treating Ebola.

"The development of ZMapp and its success in treating monkeys at an advanced stage of Ebola infection is a monumental achievement," wrote Thomas W. Geisbert of the University of Texas Medical Branch at Galveston in an article accompanying the study.

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Ebola continues to spread, with Senegal confirming its first case today. At the same time, scientists are reporting the first strong evidence that a drug may be effective for fighting the disease. It's known as ZMapp. As we hear from NPR's Rob Stein, it's been found to save infected monkeys.

ROB STEIN, BYLINE: Even though doctors have given ZMapp to a handful of victims of the current outbreak, the drug had never been tested in people or even in monkeys. That's why the new study is so important. It's the first time anyone's actually tried it on any animal that's a close relative to people.

GARY KOBINGER: It's a very important step forward in the fight against Ebola virus.

STEIN: That's Gary Kobinger of the Global Health Agency of Canada. He led the new study. The researchers infected 18 monkeys with the Ebola virus and injected the animals with ZMapp to see if the drug would save them. Every single monkey - a 100 percent - survived. And that's even though some of the animals didn't get the drug until five days after they were infected and were already sick.

KOBINGER: What's quite remarkable is that we could rescue some of the animals that had advanced disease. And what's advanced disease is the animal that is just a few days from the end - just a few hours.

STEIN: Now the question is whether ZMapp would work as well in people. The short answer? No one knows. But Kobinger and others say, this at least suggests it might.

KOBINGER: I think it strongly supports that concept.

STEIN: Two American missionaries who got ZMapp survived. But at least two other people who got ZMapp - a Spanish priest and a Liberian doctor - ended up dying anyway. So Thomas Geisbert of the University of Texas says, it's hard to know what to think from those cases.

THOMAS GEISBERT: I don't know that we can really draw any conclusions from that one way or the other.

STEIN: That's why Geisbert says, the new study is so important.

GEISBERT: I think the results are monumental in the sense that this study demonstrates the potential - the strong potential - that this would have utility in treating human cases in a situation that's realistic, where somebody starts to show symptoms.

STEIN: Even if it does work in people, the next problem is making sure it's safe. So scientists are racing to start another study that would give ZMapp to a small number of people to see. And then there's another big question - how to get more ZMapp, fast. The California company that makes the drug says, it gave away every dose it had. And Robin Robinson, a U.S. government official trying to figure out how to get more, says, it takes months to make small amounts.

ROBIN ROBINSON: This is a product in very early development, and they're just learning how to make this product at this time. So we're talking about tens of doses, as opposed to hundreds or thousands of doses.

STEIN: ZMapp's a cocktail of three kinds of proteins known as monoclonal antibodies. And right now, they're produced by genetically engineered tobacco plants. It's a slow process to grow the plants, genetically engineer them to make the antibodies and process the cocktail. But the government is trying to figure out if there's a way to speed all that up.

ROBINSON: We're moving as fast as we can break. That is, we can accelerate what would normally take a number of years into months. And we're not going to leave any stone unturned at this point.

STEIN: Officials are exploring whether they can enlist more companies with experience using tobacco plants as drug factories and even possibly make ZMapp using animal cells, which could be a lot faster. But Robinson stresses it's way too soon to know how quickly any of this might happen might happen. Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.