Targeting Autoimmunity in Type 1 Diabetes with Teplizumab
For decades, treatment for type 1 diabetes has focused on replacing insulin after the immune system destroys the pancreas’s insulin-producing beta cells. While insulin remains lifesaving, it does not address the underlying autoimmune process that causes the disease.
In June 2026, the U.S. Food and Drug Administration (FDA) approved a new indication for teplizumab (Tzield) for children and adolescents ages 8 to 17 who have been recently diagnosed with Stage 3 Type 1 diabetes. The approval marks the first time a disease-modifying therapy has been approved for newly diagnosed Stage 3 disease, reflecting a growing shift toward treatments designed to slow autoimmune damage rather than simply manage its consequences.
Targeting the Autoimmune Process
Type 1 diabetes develops when the immune system mistakenly attacks the insulin-producing beta cells of the pancreas. Teplizumab is a humanized anti-CD3 monoclonal antibody that targets this autoimmune process, helping delay the decline of the body’s remaining insulin production after diagnosis.
Unlike therapies that require continuous immune suppression, teplizumab is administered in two 12-day treatment courses. Researchers believe it works by modifying immune activity involved in the autoimmune attack while helping preserve the body’s remaining beta-cell function. More broadly, this reflects an increasing focus in autoimmune research on restoring immune tolerance (the immune system’s ability to distinguish healthy tissue from harmful threats) rather than broadly suppressing immune function.
💡 Did You Know?
Type 1 diabetes develops in stages before symptoms appear.
- Stage 1: Diabetes-related autoantibodies are present, but blood sugar remains normal and there are no symptoms.
- Stage 2: Autoantibodies remain present, and blood sugar begins to rise, but symptoms have not yet developed.
- Stage 3: Symptoms develop because the immune system has destroyed enough insulin-producing beta cells that the body can no longer make sufficient insulin. Insulin therapy becomes necessary.
Why this matters: Teplizumab was first approved in 2022 to delay progression from Stage 2 to Stage 3 Type 1 diabetes. The new FDA approval expands its use to children and adolescents who have already reached Stage 3, helping delay the decline of their remaining insulin production after diagnosis.
Evidence from the PROTECT Trial
The approval was supported by results from the Phase 3 PROTECT clinical trial, which enrolled 328 children and adolescents within six weeks of a Stage 3 Type 1 diabetes diagnosis. Participants received two 12-day courses of teplizumab, administered 26 weeks apart, in addition to standard diabetes care.
After 78 weeks, participants receiving teplizumab maintained significantly greater insulin-producing capacity than those receiving placebo, as measured by stimulated C-peptide, a marker of the body’s natural insulin production.
Nearly 95% of treated participants maintained clinically meaningful C-peptide levels, compared with about 79% of those receiving placebo.
The study did not find statistically significant differences in several secondary clinical outcomes, including HbA1c, insulin dose, or time spent within the target glucose range. However, because preserving insulin production is considered reasonably likely to predict long-term clinical benefit, the FDA granted accelerated approval while additional studies continue.
Looking Ahead
Teplizumab is not a cure for Type 1 diabetes, and insulin therapy remains essential. However, this approval represents an important milestone in autoimmune medicine. It expands the role of disease-modifying therapy beyond delaying the onset of clinical disease and into preserving remaining pancreatic function after diagnosis.
As researchers continue to develop therapies that target the immune mechanisms driving autoimmune diseases, approaches like teplizumab may help shift treatment toward preserving healthy tissue and slowing disease progression rather than only replacing what has already been lost.
Citations
FDA Approves New Indication for Tzield (teplizumab) for Certain Pediatric Patients with Recently Diagnosed Stage 3 Type 1 Diabetes. Updated 06/15/2026. https://www.fda.gov/news-events/press-announcements/fda-approves-new-indication-tzield-teplizumab-certain-pediatric-patients-recently-diagnosed-stage-3
Lledó-Delgado, A., Preston-Hurlburt, P., Currie, S., Clark, P., Linsley, P. S., Long, S. A., Liu, C., Koroleva, G., Martins, A. J., Tsang, J. S., & Herold, K. C. (2024). Teplizumab induces persistent changes in the antigen-specific repertoire in individuals at risk for type 1 diabetes. The Journal of clinical investigation, 134(18), e177492. https://doi.org/10.1172/JCI177492
Ramos, E. L., Dayan, C. M., Chatenoud, L., Sumnik, Z., Simmons, K. M., Szypowska, A., Gitelman, S. E., Knecht, L. A., Niemoeller, E., Tian, W., Herold, K. C., & PROTECT Study Investigators (2023). Teplizumab and β-Cell Function in Newly Diagnosed Type 1 Diabetes. The New England journal of medicine, 389(23), 2151–2161. https://doi.org/10.1056/NEJMoa2308743