Tzield, also known as teplizumab, is not an insulin replacement and the FDA did not describe it as a cure. The agency said stage 3 type 1 diabetes is the symptomatic stage in which high blood sugar causes clinical disease and patients require insulin therapy to manage blood sugar. The new approval covers children and teenagers diagnosed within the previous six weeks.
The evidence comes from PROTECT, a randomized, double-blind, placebo-controlled trial. The FDA said the study enrolled 328 patients aged 8 to 17 with stage 3 type 1 diabetes, and that all participants still had some working beta cells when they entered the trial. Beta cells are the pancreatic cells that produce insulin.
Table: Tzield stage 3 approval at a glance
| Item | FDA or Sanofi description |
|---|---|
| Population | Children aged 8 to 17 recently diagnosed with stage 3 type 1 diabetes |
| Trial | PROTECT, randomized, double-blind and placebo-controlled |
| Size | 328 patients diagnosed within the previous six weeks |
| Treatment course | Daily IV treatment for 12 days, repeated after about six months |
| Main endpoint | C-peptide at 78 weeks, used as a measure of remaining insulin production |
| Safety warning | Boxed warning for serious life-threatening viral reactivation, including EBV and CMV |
Source: FDA and Sanofi, June 2026.
The FDA said patients receiving teplizumab had a smaller decline in beta-cell function at 78 weeks than patients receiving placebo, measured by C-peptide. C-peptide is a protein measured in blood that indicates how much insulin the body is still producing. Sanofi said PROTECT found a least-squares mean difference of 0.13 pmol/mL in C-peptide area under the curve compared with placebo, with a 95% confidence interval of 0.09 to 0.17 and p<0.001.
The clinical context is that preserving beta-cell function may help some patients after diagnosis, but it does not remove the need for standard diabetes care. Sanofi said all PROTECT participants received standard-of-care medicines as required. The FDA page says stage 3 patients require insulin therapy, so the new indication should be read as a disease-modifying add-on for selected patients, not a substitute for insulin.