WASHINGTON, Aug. 6 (Xinhua) -- As a "secret serum" called ZMapp emerged as the primary treatment of two American aid workers infected with Ebola in West Africa, experts warned that it is too early to tell if the treatment is effective.
International attention has turned to the experimental drug known as ZMapp, developed by San Diego-based Mapp Biopharmaceutical and manufactured by Owensboro-based Kentucky BioProcessing (KBP), because Nancy Writebol and Kent Brantly, who contracted the deadly disease while treating patients in Liberia, seemed to be improving after they were treated with the medication.
The U.S. manufacturer of the first alleged treatment confirmed on Wednesday it provided "a limited amount of ZMapp" to Emory University Hospital in Atlanta, where the two are being treated, after it received a request last week from the hospital and the Samaritan's Purse, a Christian aid organization Brantly worked for.
"KBP is working closely with Mapp Biopharmaceutical, various government agencies, and other parties to increase production of ZMapp," KBP spokesman David Howard told Xinhua. "But this process will take several months."
When asked about the company's current or targeted ZMapp production capacity, he said that information "would be proprietary."
If it becomes available, it was "premature" to send the experimental drug to West Africa, which has been hardest hit by the deadly outbreak, U.S. President Barack Obama said Wednesday.
"I think we've got to let the science guide us. And you know, I don't think all the information is in on whether this drug is helpful," Obama told a press conference at the close of a three- day summit with dozens of African leaders.
"I think it's premature for me to say that because I don't have enough information," he said. "I will continue to seek information about what we're learning with respect to these drugs going forward."
Mapp Biopharmaceutical said earlier that ZMapp, a mixture of three monoclonal antibodies, was first identified as a drug candidate in January and "has not yet been evaluated for safety in humans."
"As such, very little of the drug is currently available," the company said in a statement, adding they are working to "increase production as quickly as possible."
Some U.S. experts were also cautious, saying they were not sure if the two patients' recovery was due to the ZMapp treatment.
"It is impossible to tell whether the reported improvements in health are related to the use of ZMapp," Martin Hirsch, professor in the Department of Immunology and Infectious Diseases of the Harvard University, said.
"The merits and risks of ZMapp treatment can only be evaluated by carefully controlled clinical trials. Until these are done, no conclusions can be drawn about widespread production or use," he told Xinhua.
The U.S. Centers for Disease Control and Prevention (CDC) expressed similar opinions.
"Since the product is still in an experimental stage, it is too early to know whether ZMapp is effective," the CDC said in a statement. "It's important to note that the standard treatment for Ebola remains supportive therapy," including treating the Ebola patients for any complicating infections."
As to the question of African sufferers' access to the experimental treatment, the CDC reiterated that "the manufacturer reports that there is a very limited supply, so it cannot be purchased and is not available for general use."
The CDC said that several companies are developing new Ebola treatments, but all are in the early stages of development.
The Ebola virus can kill up to 90 percent of those who become infected, and the fatality rate in the current epidemic is about 60 percent.
The outbreak, by far the largest in the nearly 40-year history of the disease, has affected 1,711 and killed 932 people this year in four Western African countries -- Guinea, Liberia, Nigeria and Sierra Leone -- according to the World Health Organization.