The purpose of this study is to measure change in glycemic control and insulin needs with Teplizumab compared with placebo. The intervention, either Teplizumab or placebo, will be administered by intravenous (IV) infusion, to participants recently diagnosed with stage 3 type 1 diabetes (T1D) aged 1 to 25 years.

Teplizumab, also known as Tzield, is currently approved for use in stage 2 type 1 diabetes, to delay the onset of stage 3 T1D in adults and children eight years and older. Teplizumab is the first and only disease modifying therapy in autoimmune T1D.

The goals of this research study are to find out how having COVID-19 recently affects blood sugar, inflammation, and insulin in people with type 1 and type 2 diabetes. We also want to see if COVID-19 changes blood vessel health or makes blood clot more easily. We will also look at how things like genes, lifestyle, and environment might affect these issues.

The goal of this Phase 2 study is to assess safety and efficacy of frexalimab to preserve -cell function in participants with newly diagnosed type 1 diabetes (T1D). We are currently enrolling ages 12-21.