As Ebola raged through West Africa last summer, an experimental drug was tried for the first time on two American aid workers in Liberia who were gravely ill with the virus. Both recovered, one of them rapidly. Though it could not be said for sure that the drug, ZMapp, was responsible, patients and doctors began clamoring for it. But there was enough to treat only a handful of patients. Federal officials vowed to produce more. Six months later, very little has been produced, diminishing the chances that the drug can be used to treat large numbers of patients in the current outbreak, which appears to be ebbing. Efforts to procure more of the drug have run into snags, according to federal officials, researchers and biotechnology executives. The DHHS asked for proposals to produce more of it to be submitted by November, but so far, no contracts have been awarded. Thomas Geisbert, an Ebola expert at UTMB, said ZMapp and another drug also in short supply, called TKM-Ebola, were the most promising potential treatments for Ebola based on their effectiveness in treating monkeys. “Make more of them. We know they work,” he said. “If I were exposed to the virus, those are the two things I would want.”