Schematic illustration of the study protocol. Twenty patients, divided in five dose subgroups (18.0 to 39.6 μg/kg of BW), were treated with seven intravenous bolus injections of SDZ MRL 953 at the indicated time points. One of four patients was randomized to receive double-blind vehicle control instead of SDZ MRL 953. Three days after the last injection of SDZ MRL 953 or vehicle control, each patient was challenged with an intravenous bolus injection of endotoxin (2 ng/kg of BW). Patients were monitored closely for toxic effects of the drugs, and serial blood samples were drawn for hematologic changes and systemic cytokine release, as described in the Materials and Methods.