Protocol TN-25

The study is a two-arm, multicenter, double-blinded clinical trial testing sequential therapy with rituximab-pvvr followed by abatacept versus rituximab-pvvr alone in new onset T1D. The primary objective is to test whether the C-peptide response to a 2-hour mixed meal tolerance test, will be improved in participants with new onset T1D who are treated with Abatacept after Rituximab-pvvr compared to those treated with Rituximab-pvvr and placebo 24 months after enrollment.

This is a two-arm, double-blind, multicenter clinical trial testing sequential therapy with rituximab-pvvr followed by abatacept versus rituximab-pvvr alone in individuals with new onset T1D to determine whether rituximab-pvvr followed by abatacept results in an improvement in the AUC C-Peptide during a MMTT compared to Rituximab-pvvr alone at 24 months. Additional aims will compare the safety, tolerability in the two treatment arms as well as other

Clinical metabolic measures: exogenous insulin use, hemoglobin A1c, time in range from continuous glucose monitors, and severe hypoglycemia. Exploratory studies will assess changes in immune markers.

Inclusion Criteria:

1. Age ≥ 8 and ≤ 45 years old at time of signing informed consent.

2. Fulfill the ADA criteria for diagnosis of T1D within 100 days of randomization.

3. Must be willing to provide informed consent or assent with a parent or legal guardian providing informed consent if < 18 years of age.

4. Positive for at least one islet cell autoantibody; GAD65A, mIAA (if obtained within 10 days of the onset of insulin therapy), IA-2A, ICA, or ZnT8A

5. Must have stimulated C-peptide of ≥0. 2 pmol/mL measured during mixed-meal tolerance test (MMTT) conducted at least 21 days after the diagnosis of diabetes.

6. Enrollees must be willing to comply with intensive diabetes management.

7. Body weight must be ≥ 20. 0 kg for study agent administration.

8. Subjects who are CMV and/or EBV seronegative at screening must be CMV and/or EBV PCR negative and may not have had signs or symptoms of a CMV and/or EBV compatible illness prior to randomization.

9. Female participants with reproductive potential must have a negative pregnancy test at screening and be willing to avoid pregnancy for the duration of treatment and until 3 months after the last dose of Abatacept. Female participants with reproductive potential who are sexually active will be instructed to use a highly effective contraceptive method until one year after the last dose of rituximab-pvvr.

10. Male participants of reproductive age must use an adequate contraceptive method for

the duration of rituximab-pvvr treatment and 12 months following the last dose of

rituximab-pvvr.

1. The following additional inclusion criteria regarding vaccines must be met:

2. More than 4 weeks from immunization with a live viral vaccine

3. Be up to date on all recommended vaccinations based on age of subject*

4. Receive non-live influenza vaccination at least 2 weeks prior to randomization when vaccine for the current or upcoming flu season is available

5. Up to date, including eligible boosters as indicated for COVID-19 with an authorized non-live COVID-19 vaccination at least two weeks prior to randomization.

6. Willingness to forgo vaccines (other than killed influenza) during the 6 months after the rituximab-pvvr treatment period

7. Participants must be willing to practice public health prevention measures such as

social distancing, masking, and good hand hygiene, and/or receive therapeutics such as

monoclonal antibodies and antivirals as directed by the study and recommended by local

health authorities to prevent SARS-Cov-2 infection.

1. Willing to wear a continuous glucose monitoring device for a minimum of 10 days every

6 months * Adult subjects must be fully immunized. Pediatric subjects who have not

completed their primary vaccination schedule must receive all vaccinations allowable

per local public health immunization guidelines for their current age prior to study

drug delivery. Any remaining vaccinations should be given and continue per the

schedule at least 6 months after rituximab-pvvr is administered.

Exclusion Criteria:

1. One or more screening laboratory values as stated:

   1. Leukocytes