ZMapp

In the absence of official confirmation about how the two American patients with Ebola are being treated, rumor and speculation filled the void.

First were the reports that the blood serum of a teenage Ebola survivor may have saved Dr. Kent Brantly and Nancy Writebol, who contacted the deadly disease in Liberia while working with the Christian aid organization Samaritan's Purse. The latest  news centers around an experimental "secret serum" called ZMapp. Already, CNN's Dr. Sanjay Gupta has proclaimed that the medicine "appears to have worked."

Sadly, Dr. Gupta seems to be over-promising. Here's why.

Treating Ebola with the blood of a survivor

The science behind the first alleged treatment — using the blood serum of a survivor to cure those who are suffering — is the subject of controversy in the Ebola research community, said Dr. Thomas Geisbert, a professor or microbiology and immunology at the University of Texas Medical Branch.

"Back in 1995 during the large outbreak of Ebola Zaire virus in the Democratic Republic of the Congo, there were reports that convalescent serum was used from people who survived Ebola to treat people who were infected," he said.

A small case series report about the treatment involving eight patients was published in the Journal of Infectious Diseases. Only one of the eight people died, a fatality rate much lower than the then-outbreak, which killed some 80 percent of those infected.

Unfortunately, however, the serum theory was not confirmed by later studies. "When we tested that hypothesis in a lab, and took convalescent blood from animals who survived and gave it to Ebola-infected animals, they all died," said Dr. Geisbert. "There was the belief that most of those patients treated were in the process of recovering anyway."

The "secret serum"

Yesterday, the "secret serum" called ZMapp emerged as the primary treatment of the Americans. This is an antibody therapy developed by several stakeholders — Mapp Biopharmaceutical, Inc. and LeafBio in San Diego, Defyrus Inc. from Toronto, the U.S. government and the Public Health Agency of Canada — to treat Ebola. It's made up of a cocktail of monoclonal antibodies, which are just lab-produced molecules that mimic the body's immune response.

To create these molecules, scientists gave mice Ebola proteins and watched the animals' immune systems respond. After identifying the antibodies that fought off the disease in mice, they created almost identical antibodies from plants for use in humans. The idea is that, when given to Ebola-infected people, the drug will boost their immune system so that they too can eliminate the virus.

But this drug has never undergone testing in people, only monkeys. The data on the efficacy of ZMapp in monkeys has never even been published.

Studies on similar drugs are not entirely confidence inducing, either. In this study, two of the four monkeys given monoclonal antibodies 48 hours after exposure to Ebola survived. In this second study, the animals had a 43 percent survival rate when given the drug cocktail after the onset of symptoms. So even though the treatment of monoclonal antibodies decreased the mortality rate — if given close to exposure of the illness —  scientists haven't moved past these tiny animal studies to testing in actual people.

Mapp Biopharmaceuticals is also just one of some 25 labs in seven countries working on these antibody cocktails for Ebola, and none of them have entered a phase one trial in humans, according to the journal Science. For this reason Dr. Martin Hirsch, a Harvard virologist, told Vox, "It’s too premature to say that the patients being treated miraculously improved."

That doesn't mean ZMapp isn't a promising therapy, however. It just means the American Ebola victims are effectively undergoing a science experiment. Even if they survive, it wasn't necessarily the drug that saved their lives. Over 20 percent of people who get this type of Ebola survive. To know whether the drug truly works, it needs to be properly tested in clinical trials. And doing that will require funding drug companies and governments may not want to invest.

Why ZMapp?

According to the US National Institute of Allergy and Infectious Diseases, Samaritan's Purse contacted CDC officials working in Liberia. They asked about the status of several experimental Ebola treatments that they had identified for possible use in the infected American missionaries.

"CDC officials referred them to an NIH scientist who was on the ground in West Africa assisting with outbreak response efforts and broadly familiar with the various experimental treatment candidates," said an NIH spokesperson. "The scientist was able to informally answer some questions and referred them to appropriate company contacts to pursue their interest in obtaining experimental product."

Right now, Samaritan's Purse will not confirm why ZMapp ended up being the chosen treatment.