Teplizumab for Prevention of Type 1 Diabetes In Relatives "At-Risk"

Inclusion Criteria: * Between ages of 8-45 years * Have a relative with type 1 diabetes * If first degree relative must be 8-45 years old (brother, sister, parent, offspring) * If second degree relative must be between 8-20 years old (niece, nephew, aunt, uncle, grandchild, cousin) * Abnormal glucose tolerance by OGTT confirmed with 7 weeks of baseline visit \[fasting blood glucose greater than 110mg/dL or and less than 126 mg/dL OR 2 hour glucose greater or equal to 140 mg/dL and less than 200 mg/dL OR 30, 60, or 90 minute value on OGTT greater than or equal to 200 mg/dL\] * Presence of at least two confirmed diabetes autoantibodies Exclusion Criteria: * type 1 diabetes previously diagnosed or detected at screening \[fasting glucose greater or equal to 126 mg/dL or 2 hour glucose greater or equal to 200 mg/dL\] * abnormalities in blood counts, liver enzymes, international normalised ratio (INR), * positive purified protein derivative (PPD) test * vaccination with live virus within 6 weeks of randomization * evidence of acute infection based on laboratory testing or clinical evidence * serological evidence of past current or past HIV , hepatitis B, or hepatitis C infection * Be currently pregnant or lactating * Prior treatment with study drug * Prior treatment with other monoclonal antibody in past one year