Ascending Dose Study of the Safety and Tolerability of REGN727(SAR236553) in Healthy Volunteers

This study will test the safety and tolerability (how the body reacts to the drug) of REGN727 compared with placebo (an inactive substance that contains no medicine) in healthy subjects. The study drug and placebo will be administered by intravenous (I.V) infusion at one clinic visit. There will be 14 clinic visits, which will include 4 overnight stays. Subjects will be monitored by the study staff for side effects and the body's response to the study drug. Vital signs(blood pressure, temperature, breathing and heart rate) will be checked, and blood and urine samples will be collected at some or all visits.