American physician Richard Sacra, who contracted the disease in Liberia while caring for women in labor, has received an experimental drug called TKM-Ebola, made by Tekmira Pharmaceuticals Corp. TKM hasn't been approved yet, and the Food and Drug Administration has put its trial on a partial clinical hold while investigating side effects. But the agency allowed Sacra to receive it for compassionate use. TKM-Ebola prevents the Ebola virus from reproducing, Geisbert said. While it's too early to know if TKM-Ebola will work on more patients, Geisbert said he's encouraged the Sacra was able to take the drug safely. That's no small feat, he said. Experimental drugs with unknown effects are usually tested in healthy people. Sacra was acutely ill when he received the drug.