The experimental drug used to treat two American aid workers who have been infected with the Ebola virus has never been tested on humans before and was only identified earlier this year as part of an ongoing research program backed by the U.S. government and military.
Dr. Kent Brantly and Nancy Writebol have each received doses of the drug, known as ZMapp, aimed at boosting the immune system's efforts to fight off Ebola and is made from antibodies produced by lab animals exposed to parts of the virus.
The Associated Press reported that Writebol, 59, had received two doses of the drug while being treated in Liberia. She was en route to the United States for further treatment early Tuesday. Bruce Johnson, the president of SIM USA, the Charlotte, North Carolina-based group that Writebold works for in Africa, said that she was walking with assistance and had regained their appetite.
Johnson told the Associated Press that he was hesitant to credit the drug for Writebold's improvement, saying "Ebola is a tricky virus and one day you can be up and the next day down. One day is not indicative of the outcome, [but] we're grateful this medicine was available."
Brantly, 33, who arrived at Emory University Hospital in Atlanta for further treatment Saturday, also was said to be improving. Besides the experimental ZMapp dose he got in Liberia, Brantly also received a unit of blood from a 14-year-old boy, an Ebola survivor, who had been under his care. That seems to be aimed at giving Brantly antibodies the boy may have made to the virus.
There is no vaccine or specific treatment for Ebola. Those who have survived the virus in the past have done so on their own.
In a statement, drug maker Mapp Biopharmaceutical Inc. of San Diegosaid it was working with LeafBio of San Diego, Defyrus Inc. of Toronto, the U.S. government and the Public Health Agency of Canada on development of the drug, which was identified as a possible treatment in January.
The drug is made in tobacco plants at Kentucky BioProcessing, a subsidiary of Reynolds American Inc., in Owensboro, Kentucky, said spokesman David Howard. The plant "serves like a photocopier," and the drug is extracted from the plant, he said.
Kentucky BioProcessing complied with a request from Emory and the international relief group Samaritan's Purse to provide a limited amount of ZMapp to Emory, he said. Brantly works for the aid group.
The Kentucky company is working "to increase production of ZMapp but that process is going to take several months," Howard said. The drug has been tested in animals and testing in humans is expected to begin later this year.
The international relief group Samaritan's Purse initiated the events that led to the two workers getting ZMapp, according to a statement Monday by the National Institute of Allergy and Infectious Diseases, part of the U.S. National Institutes of Health. The Boone, North Carolina-based group contacted U.S. Centers for Disease Control and Prevention officials in Liberia to discuss various experimental treatments and were referred to an NIH scientist in Liberia familiar with those treatments.
The scientist answered some questions and referred them to the companies but was not officially representing the NIH and had no "official role in procuring, transporting, approving, or administering the experimental products," the statement says.
The U.S. Food and Drug Administration must grant permission to use experimental treatments in the United States, but the FDA does not have authority over the use of such a drug in other countries, and the aid workers were first treated in Liberia. An FDA spokeswoman said she could not confirm or deny FDA granting access to any experimental therapy for the aid workers while in the U.S.
The Defense Department has long had a hand in researching infectious diseases, including Ebola. During much of the Cold War period this served two purposes: to keep abreast of diseases that could limit the effectiveness of troops deployed abroad and to be prepared if biological agents were used as weapons.
The U.S. military has no biological weapons program but continues to do research related to infectious diseases as a means of staying current on potential threats to the health of troops. It may also contribute medical expertise as part of interagency efforts in places like Africa where new infectious disease threats arise.
The hospital in Atlanta treating the aid workers has one of the nation's most sophisticated infectious disease units. Patients are sealed off from anyone not in protective gear. Ebola is only spread through direct contact with an infected person's blood or other bodily fluids, not through the air.
On Monday, the World Health Organization said the death toll had increased from 729 to 887 deaths in Guinea, Sierra Leone, Liberia and Nigeria, and that more than 1,600 people have been infected.
In a worrisome development, the Nigerian Health Minister said a doctor who had helped treat Patrick Sawyer, the Liberian-American man who died July 25 days after arriving in Nigeria, has been confirmed to have the deadly disease. Tests are pending for three other people who also treated Sawyer and are showing symptoms.
The Associated Press contributed to this report.