CNP-103 for Recently Diagnosed Stage 3 Type 1 Diabetes

Inclusion Criteria: 1. Participants who are willing and able to provide Institutional Review Board (IRB) approved written informed consent and privacy language as per national regulations. 2. Men and non-pregnant, non-breast-feeding women ages 12-35 years inclusive. 3. Documented diagnosis of Stage 3 T1D within 180 days prior to study enrollment according to American Diabetes Association (ADA) criteria. 4. Participants must be on standard of care diabetes management including insulin therapy as a routine and also consisting of a nutrition plan, regular exercise, or other relevant specialty care as required on a patient-by-patient basis. 5. Participants with a peak stimulated C-peptide of \>0.2 nmol/L measured from a screening mixed meal tolerance test (MMTT). 6. Participants with an episode of diabetic ketoacidosis (DKA) must have a MMTT performed no sooner than 2 weeks after resolution of the DKA event to have a qualifying C-peptide reading. 7. Participants on systemic corticosteroids or any medication used to treat the symptoms of T1D (other than insulin) must undergo a washout period of at least two weeks prior to enrollment and must agree to use a non-steroid alternative throughout the trial, if necessary, for any disorder requiring corticosteroids. In addition, participants must be on a stable dose of any other medications, other than insulin, for a minimum of 1 month prior to enrollment and must agree not to increase their dose from the Screening Visit through the End of Study Visit unless reviewed and approved by the medical monitor and the principal investigator. 8. Female participants of non-childbearing potential (e.g., surgical sterilization, no menses for a year). 9. Women of childbearing potential (WOCBP) who have agreed not to become pregnant during the study, have a negative pregnancy test at Screening Visit, and agree to use 1 highly effective form of birth control starting at initial screening and continuing throughout the entire study to Day 365. 10. Female participants who agree to not breastfeed starting at initial Screening and throughout the entire study to Day 365. 11. Female participants who agree to not donate ova, including autologous, starting at initial Screening and throughout the entire study to Day 365. 12. Male participant and with a spouse or partner of childbearing potential, who themselves and their spouse or partner agree to practice an effective form of birth control as discussed with the study doctor or study staff starting at Screening and throughout the entire study to Day 365. 13. Participants must weigh \>35 kg at Screening for Cohort 1 (100 mg) and Cohort 2 (300 mg); participants must weigh \>50 kg at Screening for Cohort 3 (600 mg). 14. Body mass index (BMI): 1. Participants 12-17 years: BMI Z-Score within 5th and 95th percentile based on participant's age (e.g., Baylor College of Medicine Age-based Pediatric Growth Reference Charts: BMI Z-Score and Percentile Calculator) 2. Participants 18-35 years: 18.0-30.0 (not inclusive) Exclusion Criteria: 1. Participants unable to comply with prohibited medication outlined in the protocol. 2. Exclusion of additional immunomodulation will be at the discretion of the Medical Monitor and study site Investigator. 3. Participants with a history of tuberculosis or positive Quantiferon test. 4. Participants who received vaccinations in the following time frame: 1. Any live vaccine within 28 days prior to Screening. 2. Any subunit vaccine within 14 days prior to Screening. 3. Any COVID-19 vaccine series within 14 days prior to Screening. 4. Any other planned vaccine starting 14 days prior to Screening and through study Day 90 and 1 week after. (Note: The annual influenza vaccine is not an exclusion criterion.) 5. Known or suspected acute infection, including COVID-19 at the time of Screening or within 2 weeks prior to Screening. After confirmed recent COVID-19 infection, a minimum of 2 weeks of recovery post-acute infection is required. 6. Participants with Screening laboratory test results that are outside the normal limits and considered by the Investigator to be clinically significant. 7. Participants with positive test results for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibody, or human immunodeficiency virus (HIV) antigen/antibody as determined at Screening. 8. Participants with a history of or currently active immune disorders other than T1D (including autoimmune disease) unless the condition, after discussion with the Medical Monitor, has been deemed to be acceptable for the participant's participation in this study. 9. Participants with a clinical history of significant cardiovascular disease in the past 12 months. 10. Participants with a complication or medical history of malignant tumor, other than basal cell or squamous cell carcinomas of the skin. 11. Participants who, in the Investigator's opinion, will be unable to adhere to study visits and procedures. 12. Participants who have received investigational therapy other than CNP-103 within 28 days or 5 half-lives, whichever is longer, prior to Screening. 13. Participants with any known active condition which, in the Investigator's opinion, makes the participant unsuitable for study participation. 14. Known sensitivity to any components of CNP-103.