The aim of this study is to evaluate safety, and tolerability of insulin LY3209590 following a single dose given to children with type 2 diabetes mellitus (T2DM). This will be the first study to evaluate LY3209590 in pediatric patients with T2DM.

Screening:

All participants will be screened up to 28 days prior to dosing.

Treatment and Assessment Period:

On Day 1, participants will receive a single 100-Unit subcutaneous dose of LY3209590 at the clinical research unit.

Follow up research visits will be performed on Days 3, 5, 7, 15, 29, 43, and 65. Blood sampling and safety assessments will be performed at each in clinic visit. Before each study visit, subjects will need to fast for at least 8 hours.

A follow-up telephone call will be performed on approximately Day 72. The total time for participation is the study is about 100 days.

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). In Part A, an exploratory part, adults (ages 18-35) will be treated with either high dose frexalimab, or placebo (inactive study drug). In Part B, adolescents and young adults (ages 12-21) will be treated with 3 dose levels of frexalimab or placebo.