Two multicenter controlled clinical trials of genetically engineered monoclonal antibodies directed against endotoxin, a potent mediator of inflammation in the gram-negative sepsis syndrome, were recently reported in the medical literature. One of these antiendotoxin antibodies was derived from a murine (mouse) source, and the other antibody was derived mainly from a human source (nebacumab [negative bacteria human monoclonal antibody]). This article reviews recent literature concerning the use of these agents in the treatment of gram-negative sepsis syndrome. It also projects economic assessment data regarding the use of nebacumab in the United States.