Stage-2 T1D: The Decision That Did Not Used to Exist

What “Stage 2” actually means

The American Diabetes Association staging framework defines T1D in three stages, each describing the same underlying autoimmune process at a different point in its arc. Stage 1 is the immune system already attacking the insulin-producing cells, with autoantibodies present in the blood; the child has normal blood glucose and no symptoms. Stage 2 is the same process now showing up in the way the body handles a glucose challenge: still no clinical symptoms, but an oral glucose tolerance test (OGTT) shows dysglycaemia, and two or more autoantibodies are present. Stage 3 is the clinical T1D the family already recognises, with symptoms, the diagnosis, and the start of insulin therapy. The framework is now how international paediatric services route screening conversations.

The reason the staging matters is that progression from Stage 2 to Stage 3 is not a maybe but a when. The published natural history puts the median time to clinical T1D from a Stage 2 diagnosis at around two years on standard observation. Knowing that earlier changes nothing for the child clinically; their pancreas is already on the path it was on. What it changes is the family’s window to plan, the diabetes team’s window to support, and (in countries where it is licensed) the conversation about an immune-modifying medicine that can shift the timing.

The TN10 trial, in plain English

The pivotal trial that put teplizumab on the regulatory map was TrialNet TN10 (Herold 2019, NEJM). Seventy-six relatives of people with T1D, all Stage 2 (two or more autoantibodies plus a dysglycaemic OGTT), were randomised to a single fourteen-day course of intravenous teplizumab or placebo. The primary endpoint was time to clinical T1D as defined by the standard ADA criteria. Median time to T1D was 48.4 months in the teplizumab arm versus 24.4 months in the placebo arm (hazard ratio 0.41, 95% confidence interval 0.22 to 0.78, p=0.006). In plain English: the medicine roughly doubled the median time to clinical onset.

The extended follow-up (Sims 2021, Science Translational Medicine) on the same cohort with longer observation showed the gap holding open. Median time to T1D extended to 59.6 versus 27.1 months. At the longer follow-up window, fifty percent of the teplizumab-treated participants remained diabetes-free, against twenty-two percent of the placebo group. The Sims paper also added the first mechanistic correlate of clinical response (a specific exhausted-CD8 T-cell signature that tracked with how much benefit each individual got), which gave the field a way to start thinking about who responds best.

Teplizumab is licensed in the United States under the brand name Tzield, FDA-approved from age 8 for Stage 2 T1D since November 2022. In the United Kingdom and Europe, it is not yet licensed for this indication; access is currently through trial pathways and named-patient routes. The European regulatory conversation is active but unsettled.

What the medicine is actually doing, and what it is not

Teplizumab is a humanised monoclonal antibody against CD3, a marker on the surface of T cells. It is given as a single fourteen-day course of IV infusions. It does not cure T1D. It does not regenerate insulin-producing cells. What it appears to do is take the foot off the autoimmune accelerator for long enough that the pancreas keeps more of its insulin-producing capacity for longer, which translates into a longer window before clinical T1D arrives.

Side effects on the trial were what you would expect from a T-cell-modulating therapy. Lymphocyte counts dropped (median nadir on day 5, recovered by day 45 in all but one participant); a transient skin rash occurred in around a third; transient Epstein-Barr virus reactivation was seen in eight of sixteen EBV-seropositive teplizumab participants. These were reversible and managed; no participant developed a long-term immune complication during the trial follow-up period. Long-term safety in real-world Stage-2 populations is still being mapped through post-marketing surveillance.

The honest framing is that teplizumab is a treatment that buys time. The size of the gift varies (the Sims mechanistic correlate is the start of explaining why), and what the family does with the time is its own conversation. Some families value the time itself: an extra year before the school routine has to absorb pump and CGM and carbohydrate counting. Some value it because of what changes downstream: more time on the technology curve, more chance the next-generation Stage-3 pivotal lands before the child needs it. Both readings are reasonable. Neither is automatic.

How the family conversation actually happens

The path into a Stage-2 conversation almost always starts upstream, with antibody screening. In the United States the dominant pathway is TrialNet, which screens relatives of people with T1D for free; in the United Kingdom, the ELSA general-population study screens children aged 3 to 13 in collaboration with the diabetes charity sector; in Germany, the Fr1da study has run general-population screening at well-child visits since 2015. None of these pathways exist on every street corner; access depends on where the family lives and which research network the local paediatric diabetes service is connected to.

If a screen comes back positive for one antibody, the family is told the child is at higher risk than the general population but the timeline is uncertain; routine annual antibody and OGTT testing follows. If the screen returns two or more antibodies plus a dysglycaemic OGTT, that is Stage 2, and the conversation about teplizumab (where licensed) and about close monitoring (everywhere) opens up. Eligibility is assessed by a specialist paediatric diabetes service. Screening alone does not commit anyone to the medicine; the medicine is a separate conversation that the family enters or declines on its own terms.

What the family can take to the team

If a sibling, child, or close relative has been diagnosed with T1D and the family is wondering about screening, that question is now a real one and the team is ready for it. UK families can ask about ELSA, the Type 1 Diabetes Risk Test, or the local sibling autoantibody pathway; US families can ask their paediatric endocrinology service about TrialNet. If a screen has already returned at Stage 2, the next conversation is with a specialist paediatric diabetes service that has experience with the staging framework. In countries where teplizumab is licensed, ask whether your team has a referral pathway for Stage-2 evaluation; in countries where it is not yet licensed, ask whether named-patient or trial pathways are available locally.

The honest part of this conversation is that the evidence has moved faster than access has. Many family encounters about Stage 2 are with clinicians who are themselves still learning the framework. That is not a reason to delay the conversation; it is a reason to ask in writing, ask early, and ask again if the first answer is “not yet”. The team is set up to work through this with the family; the system rewards families who advocate.

References for this part