Tegoprubart: What Four Decades of T1D Taught Me About the Headlines

The “cure in five years” club is having a reunion

I joined the type-1-diabetes cure-is-five-years-away club in 1983, when I was three. I have been dues-paying ever since. Every few years a new candidate gets the spotlight — a new insulin, a new transplant protocol, a new smart pump, a new stem-cell line — and somewhere on the internet someone writes a headline that includes the word finally. Decades in, I have learned to read those headlines the way a fisherman reads a tide chart: carefully, and with a short list of specific questions.

So when the tegoprubart headlines started hitting my feeds — six islet-transplant recipients came off insulin, the first three are still off after more than a year — I did not post. I did not celebrate. I sent the paper to my endocrinologist and then I sat down to write this, because the nuance here is worth protecting.

Tegoprubart is not a cure. It is not an insulin replacement. It is not available to you or me outside a research setting. But it might be one of the more honest pieces of progress the field has produced in a decade, and the reason has nothing to do with the six people. It has to do with the immune system problem we have never solved.

What tegoprubart actually does

Tegoprubart is an investigational antibody that blocks a protein called CD40 ligand (CD40L). That protein is a key conductor in the orchestra the immune system plays whenever it decides to attack foreign tissue — including transplanted cells. Standard anti-rejection drugs tackle the whole orchestra. They work, but they leave recipients more vulnerable to infections and complications because they suppress the entire immune response.

The tegoprubart promise is surgical. By blocking just CD40L, the drug aims to quiet the specific conversation that tells the immune system to kill the transplanted islets — while leaving most of the rest of your immunity intact. That is the part that matters. If this works at scale, the cost of a cell transplant stops being “your immune system for life” and becomes something closer to “a manageable, targeted treatment”.

Developing the class has taken time. An earlier generation of anti-CD40L antibodies in the 1990s caused blood clots in clinical trials and was shelved. Tegoprubart is engineered to avoid that specific problem, which is why this trial is getting read with cautious optimism instead of the usual breathless coverage.

The Chicago trial, in careful words

The University of Chicago is running a phase 1/2 trial of tegoprubart in people with T1D who receive islet-cell transplants. Islets are tiny clusters of insulin-producing beta cells taken from a donor pancreas and placed into the liver of a person with T1D, where the cells take up residence and — if they survive — produce insulin again.

The trial is funded by Breakthrough T1D (formerly JDRF) with additional support from the Cure Alliance, and Eledon Pharmaceuticals, the company developing tegoprubart, has received investment from the T1D Fund.

What the early results actually show

Six participants who received islet transplants alongside tegoprubart have been producing their own insulin without needing exogenous injections. The first three treated have maintained that insulin independence for over a year.

I want to be honest about how I read those numbers, because encouraging and conclusive are not the same word:

• Six people is an extremely small sample. In a room that size I could count the T1Ds I was in a hospital ward with in 1983
• This is a phase 1/2 trial. The primary purpose is safety and dosing — not proof that the treatment works at scale
• Participants still received donor-pancreas islets, a procedure that comes with its own supply and surgical limits
• Long-term durability — 5, 10, 30 years — is completely unknown. I have lived with T1D since 1983. Twelve months of insulin independence is a beginning, not an ending

Why this still matters to me

Reading my own list above, it would be easy to come away thinking the story is “nothing to see, move along”. That is not the conclusion I reached. The thing this trial is quietly doing — that the headlines are not telling you — is solving the right problem for T1D cell therapy.

For 40 years the reason islet transplants have failed to scale is not the islets. It is the immune system. My body, and yours, will attack transplanted insulin-producing cells the same way it attacked the original ones. Every cell-therapy attempt has had to answer: how do you hide the new cells from the immune system long-term without destroying the rest of the immune system? Broad immunosuppression has never been a fair trade. Too much risk, too little durability.

A targeted CD40L block is the first serious attempt in my lifetime at a narrower answer. That is the news. Not the six people. The pathway.

Why this is not yet a cure

Even in the best-case scenario — bigger trials, safety holds up, the effect durable at five and ten years — several large barriers remain before “tegoprubart + islet transplant” becomes a treatment you or I can schedule.

Donor dependency. Islet transplants still require cells from human donor pancreases, and one recipient usually needs islets from multiple donors. The supply is nowhere near the 8.75 million people living with T1D worldwide. This alone disqualifies the current version as a population-scale cure.

Stem-cell-derived islets are still maturing. The real, realistic prize is pairing tegoprubart with lab-grown beta cells from companies like Vertex Pharmaceuticals and Sernova. Those cells do not need a donor and can, in theory, be manufactured. But they still face their own hurdles around maturation, function, and the same immune problem tegoprubart is trying to solve.

Regulatory pathway is long. Even if every larger trial succeeds, regulators in each market — MHRA and NICE in the UK, FDA in the US, EMA in Europe — require years of review before approval. I am making no predictions about timing, because I have been wrong every year since 1988.

What I am actually changing today — nothing

Here is what a lifetime of experimental-therapy headlines has taught me, boringly: nothing about my Tuesday changes. My Dexcom still goes on my arm. My Omnipod still delivers basal. My care team still counts carbs with me at every appointment. I still read the trial papers. I do not change anything based on them.

If you are a newly diagnosed T1D reading this, please hear the same: tegoprubart is not a reason to delay learning to manage your diabetes. The foundations we already have — automated insulin delivery technology, exercise strategies, nutrition that works with a pancreas that doesn’t — are the actual management tools of 2026. Cell therapy is a parallel conversation, not a replacement.

The three reasons I am still paying attention

Despite everything I just said, I think tegoprubart is worth watching for reasons that are more structural than the headline numbers.

1. It validates a more targeted approach to immunosuppression. If CD40L blockade protects transplanted cells without the toxic broad-spectrum side effects, the door opens for safer cell-based therapies across the field — not just for T1D.

2. It keeps the pipeline moving. The biggest obstacle to a cell-based cure has always been immune attack. Every advance in narrowing the response brings the field closer to treatments that could meaningfully reduce insulin dependence. Even if tegoprubart itself does not become the final answer, the class it belongs to probably will.

3. It has applications beyond T1D. The same drug is being studied for kidney transplants and other indications. Broader success in other organs makes the investment in larger T1D trials easier to justify — and faster to run.

What I am watching for next

Research priorities that will tell me whether the early signal holds:

• How long do transplanted islet cells survive with tegoprubart protection at year 3, year 5, year 10?
• What are the long-term side effects of targeted CD40L blockade? (The 1990s version of this idea caused blood clots. The current version is supposed to be engineered around that. I want that proven, not asserted.)
• Can tegoprubart pair with stem-cell-derived beta cells rather than donor islets?
• What happens if participants stop taking the drug?

Breakthrough T1D is also funding a study exploring tegoprubart in people who have both T1D and chronic kidney disease — a population with particularly narrow treatment options. If the safety profile holds there, confidence in the broader approach grows.

Why this headline deserves a careful read

Tegoprubart is not a cure. It is not a replacement for insulin. It is not available outside clinical trials. It is, however, a careful early attempt to solve the actual hard problem in T1D cell therapy: how to hide new insulin-making cells from an immune system that already proved it will find them. That is why this headline deserves more attention than most — and a lot less excitement than it is getting.

After a lifetime in the cure-is-five-years-away club, here is what I have learned: the news that matters is not the one with the most urgent verb. It is the one that changes the mechanism.

— John Chitta

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This article builds on Breakthrough T1D’s own “behind the headlines” explainer on tegoprubart and a 2024 review of anti-CD40L antibodies in PubMed. My reading is a personal lived-experience take from four decades with type 1 diabetes since my 1983 diagnosis, not clinical advice. Before drawing conclusions from any early-phase trial — or changing a single thing about your own care — please talk to your endocrinologist and diabetes educator.

References

1. Tegoprubart: Behind the Headlines · Breakthrough T1D UK
2. Islet Transplantation in Type 1 Diabetes — state of the field · PubMed (2022)
3. Anti-CD40L Antibodies and the Renaissance of Costimulation Blockade · PubMed (2024)
4. Stem cell-derived islets for Type 1 Diabetes — progress and limits · Nature Reviews Endocrinology (2023)
5. JDRF / Breakthrough T1D — 2024 cell-therapy roadmap · Breakthrough T1D