This clinical trial tests a new medicine called **CNP-103** for people aged 12-35 who were recently diagnosed with Stage 3 Type 1 Diabetes (T1D), which means their body cannot produce enough insulin, a hormone that helps regulate blood sugar. The study is in **Phase 1b/2a**, meaning it's one of the first times this medicine is being tested on humans to check if it's safe and how well it works. It lasts about **393 days** and includes a **Screening Period** (28 days), a **Treatment Period** (90 days), and follow-ups called **Post-Dose Evaluations** (275 days). **Key Points:** - Participants must visit the clinic often and follow specific rules about medicines and health habits. - They must be on standard diabetes care, including insulin, and meet specific health criteria. - Participants are required to agree to birth control measures and cannot donate eggs. The trial excludes those with certain infections, vaccinations close to the start date, or other health complications. Participants must be committed to following the study's schedule and procedures. **Eligibility:** Participants must be willing to sign consent forms and meet specific health and lifestyle criteria.