Teplizumab in New-Onset Type 1 Diabetes

This is a study that investigates whether an IV medication (teplizumab) will slow or halt the progression of type 1 diabetes in children and adolescents (ages 8 - 17 years). Eligible participants will be randomly assigned to receive either the study medication or an inactive substance called a placebo. All participants will receive two courses of IV infusions, six months apart from each other. During each treatment course, participants will come to CHOP for daily teplizumab or placebo infusions for 12 days. Study participation, including treatments and follow-up visits, lasts for 1.5 years.