Every time a new study about islet cell transplants makes headlines, I see the same reaction:

“Wait… I thought this was the cure?”

It’s an understandable question. When researchers announce that someone with type 1 diabetes has stopped taking insulin after receiving transplanted islet cells, it certainly sounds like they’ve discovered something brand new.

But here’s the thing:

We already know islet cell transplants work.

In fact, researchers have known that for more than 25 years.

What’s changing today isn’t whether transplanted beta cells can make insulin. We’ve already proven they can. The real challenge—the one companies like Eledon, Sana Biotechnology, Vertex, Sernova, and NewCellX are all trying to solve—is figuring out how to make those transplanted cells survive for decades instead of just a few years.

That difference matters. And understanding it completely changes how you read today’s “cure” headlines.

Nearly 1,500 Americans Have Already Received Islet Cell Transplants

One of the biggest misconceptions about today’s cure research is that islet transplantation is new.

It isn’t.

According to the Collaborative Islet Transplant Registry (CITR), 1,477 people in the United States received donor islet cell transplants between 1999 and 2023. Those transplants were performed at 40 different transplant centers and required nearly 3,000 separate islet infusions using pancreases from more than 3,400 deceased organ donors.

That’s an incredible amount of experience.

When I first started learning about islet transplantation, I honestly had no idea this many procedures had already been performed. Most people with type 1 diabetes don’t.

Instead, every new company tends to make it sound like they’re proving, for the very first time, that transplanted beta cells can replace insulin.

They’re not.

We’ve already answered that question.

The exciting part is that today’s researchers are trying to solve the problems that kept those earlier transplants from becoming a treatment for everyone.

The Cells Work. Keeping Them Alive Is the Hard Part.

If you transplant healthy insulin-producing beta cells into a person with type 1 diabetes, something remarkable happens.

Those cells start making insulin. Blood sugars improve. Some people become completely insulin-independent.

We’ve known this for years.

The problem is that, for most people, those transplanted cells gradually stop working well enough to replace insulin forever. That’s why I think the current wave of research is so exciting. Companies aren’t trying to prove that islet transplants work.

They’re trying to make them last.

Why Don’t They Last?

There isn’t one simple answer.

• Some transplanted cells die almost immediately after the procedure because they lose part of their blood supply.
• Some don’t survive the stress of being isolated from the donor pancreas.
• Some are damaged by inflammation.

And, of course, there’s the immune system.

Remember, people with type 1 diabetes don’t just have an immune system that recognizes donor tissue as foreign. They also have an autoimmune disease that specifically targets insulin-producing beta cells.

That means transplanted cells face two different enemies.

1. First, the body may reject them because they came from another person.
2. Second, the autoimmune attack that destroyed the original beta cells may start attacking the new ones, too.

Traditional immunosuppressive medications help protect transplanted cells, but they also come with significant risks and side effects. Some drugs may even place additional stress on the beta cells they’re supposed to protect.

This is exactly why so many different companies are approaching the problem from different angles.

• Eledon is studying a different type of immunosuppression.
• Sana Biotechnology is gene-editing cells so the immune system may not recognize them.
• Sernova is developing protective cell pouches.
• Vertex and NewCellX are working to manufacture unlimited supplies of insulin-producing cells.

They’re all trying to solve different pieces of the same puzzle.

Most People Needed Cells From More Than One Donor

Another lesson from the last 25 years is that donor pancreases simply aren’t enough.

The 1,477 transplant recipients in the U.S. received nearly 3,000 islet infusions.

That means many people needed cells from two or even three different donor pancreases before they had enough functioning beta cells to stop taking insulin.

Think about that for a minute: One successful transplant often required multiple organ donors. Now imagine trying to offer that treatment to the millions of people living with type 1 diabetes around the world.

It simply isn’t possible. That’s why stem-cell-derived islets are so important. If researchers can reliably grow insulin-producing cells in a laboratory, the supply problem changes completely.

Instead of waiting for donor organs, scientists could potentially manufacture as many cells as needed. But even then, we’re back to the same question: How do you keep them alive?

Even if the Islet Act passes, this does not increase the number of people who can benefit from islet cell transplants. It simply makes it easier for researchers and surgeons to use the limited number of islets available for transplants.

Insulin Independence Isn’t the Only Measure of Success

One thing I found especially interesting about the transplant registry is how researchers define success.

Most of us hear “cure” and immediately think, “No more insulin.” That’s certainly the dream.

But transplant specialists have long recognized that even partial islet function can dramatically improve someone’s life.

Many transplant recipients eventually return to taking insulin, but they continue producing measurable C-peptide. Their glucose levels become more stable. Their insulin doses are lower. And perhaps most importantly, severe hypoglycemia often becomes dramatically less common.

• Before transplantation, more than 80% of recipients had experienced severe hypoglycemia.
• Within the first year after transplant, that number dropped to about 2%.

That statistic honestly blew me away.

Even when the transplant doesn’t last forever, having a functioning group of beta cells—even a relatively small one—can provide a tremendous amount of protection. That’s an outcome worth celebrating.

But Durability Is Everything

Here’s the reality that doesn’t make headlines.

• About 40 to 60 percent of recipients are insulin-independent one year after transplantation.
• Five years later, that number drops to roughly 25 percent.

That doesn’t mean the transplant “failed.” It means the cells gradually stopped producing enough insulin to completely replace injections or pump therapy. This is why I get nervous when I see headlines celebrating someone who’s been insulin-free for six months or even a year.

I’m genuinely excited for those participants. But the most important question isn’t whether they’re off insulin today.

It’s whether those transplanted cells are still working five years from now. Or ten. Or twenty.

That’s what a real cure requires.

Today’s Research Is Building on Decades of Success

I think one of the biggest misconceptions in the diabetes community is that every new company is starting from scratch. They’re not.

The nearly 1,500 islet transplants already performed in the United States have taught researchers an incredible amount.

• They know transplanted beta cells can produce insulin.
• They know some people can become insulin-independent.
• They know severe hypoglycemia can almost disappear.
• They know what tends to predict better outcomes.

And they know exactly where the biggest problems still exist. That’s why today’s studies are so exciting. They’re not asking whether transplanted beta cells work. They’re asking how to keep them working.

What kind of “cure” do you want?

It’s important to understand that Eledon’s research, which led to 12 people going off daily insulin therapy, is still just research. It’s not a cure. They don’t know how long tegoprubart will continue to protect the cells, and they don’t know the long-term effects of tegoprubart either.

Just like the other 1500 people who’ve become insulin independent thanks to islet transplants, we need more time.