∙ Patients are eligible to be included in this study only if all of the following criteria apply:

⁃ Must be capable of providing written, signed, and dated informed consent; and for patients who are minors, age-appropriate assent (performed according to local regulations) and parent/caregiver consent.

⁃ Males and females aged ≥12 and \<29 years old at the time of Screening.

⁃ Diagnosed with T1D (according to the American Diabetes Association \[ADA\] classification) ≤6 months at the time of Screening (V1A).

⁃ Possess the HLA DR3-DQ2 haplotype (all patients will be tested; prior genetic testing results will not be accepted).

⁃ Fasting C-peptide ≥0.12 nmol/L (≥0.36 ng/mL) on at least one occasion prior to randomization.

⁃ (US ONLY): Fasting C-peptide ≥0.12 - ≤1.5 nmol/L (≥0.36 - ≤4.5 ng/mL) on at least one occasion prior to randomization.

⁃ Possess detectable circulating GAD65 antibodies (lowest level of detection defined by the method used by the central laboratory).

⁃ Possess HbA1c levels between 35 to 80 mmol/mol (5.4 to 9.5%) on at least one occasion prior to randomization.

⁃ Be on a stable basal insulin dose for one month prior to inclusion with limited fluctuation of daily basal insulin requirement based on investigator's assessment. For example, if the average basal insulin dose/kg/24h over a 7-day period compared to the previous 7-day period does not vary more than approximately 20% and/or if the daily basal insulin dose does not vary more than 0.1 U/kg/24h, the dose can be considered stable. Individuals that are diagnosed with T1D according to the ADA classification but are not taking insulin are eligible to participate.

⁃ i. Females of childbearing potential (FOCBP) must agree to avoid pregnancy and have a negative pregnancy test performed at the required study visits.

∙ FOCBP must agree to use highly effective contraception, during treatment and, until 90 days after the last administration of study medication. Birth control methods, which may be considered as highly effective (e.g., a failure rate of less than 1% per year when used consistently and correctly) include:

• Combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation:

‣ Oral.

⁃ Intravaginal.

⁃ Transdermal.

• Progestogen-only hormonal contraception associated with inhibition of ovulation:

‣ Oral.

⁃ Injectable.

⁃ Implantable.

• Intrauterine device.

• Intrauterine hormone-releasing system.

• Bilateral tubal occlusion.

• Vasectomized partner (vasectomized partner is a highly effective birth control method provided that partner is the sole sexual partner of the FOCBP trial patient and that the vasectomized partner has received medical assessment of the surgical success).

• Sexual abstinence (sexual abstinence is considered a highly effective method only if defined as refraining from heterosexual intercourse during the entire period of risk associated with the study drugs. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the patient).

• 9\. ii. Male patients must agree to remain abstinent from heterosexual sex during treatment and for 90 days after treatment or, if sexually active, to use two effective methods of birth control (e.g., male uses a condom and female uses contraception) during and for 90 days after treatment. Acceptable male contraception is as follows:

• Condom (male).

• Abstinence from heterosexual intercourse.

• Vasectomy. The agreement to remain abstinent or use two effective methods of birth control will be clearly defined in the informed consent; the patient or legally authorized representatives (e.g., parents, caregivers, or legal guardians) must sign this specific section.