In December 2024, a 42-year-old Swedish man received 17 injections of genetically altered pancreatic cells into his left arm as part of the first human test of a novel treatment for type 1 diabetes. The goal was to deliver insulin-producing cells that are invisible to the immune system, potentially sparing patients from having to also take drugs that suppress the immune response. The first paper describing results from that trial, out in August 2025 in The New England Journal of Medicine, reveals the injected cells remained alive for at least three (3) months, started to release insulin, and escaped destruction by the patient’s immune system.
That is great news, say researchers unconnected to the study. “It’s a major breakthrough, and it’s remarkable. They should be congratulated,” says Bernhard Hering, a Transplant Physician and Immunologist at the University of Minnesota Twin Cities. However, he and other scientists emphasize that it will take results from more patients — and with longer follow-up — to validate the approach.
In type 1 diabetes, the immune system destroys most or all of the pancreas’ beta cells, which produce insulin to help regulate blood sugar. Since the 1920s, people with the condition have used insulin injections to compensate. However, some patients find it difficult to precisely control their blood sugar, even with modern high-tech glucose monitors, automatic insulin pumps, and long-acting versions of the hormone. An option for these people is islet transplantation, which involves infusions of beta cells from a deceased donor. The treatment, which has been available in many countries for the past two (2) decades, however, was not approved in the United States until 2023, allows some patients to forgo insulin injections. However, recipients have to take immunosuppressive drugs for the rest of their lives, and the supply of donated beta cells is low. As a result, the procedure is rarely performed.
To avoid the need for immune suppression, researchers at Sana Biotechnology used the CRISPR genome editor to eliminate proteins on the surface of donated beta cells, called HLA-I and HLA-II, that can prompt immune rejection. Because cells without HLA-I or HLA-II also appear suspicious to the immune system, Sana researchers further engineered the beta cells to produce more of a protein known as CD47 that signals to immune cells to prevent these attacks.
Following successful tests of the approach in rodents and a monkey, endocrinologist Per-Ola Carlsson of Uppsala University and colleagues injected about 80 million of these HLA-stripped, CD47-enhanced cells into the forearm muscle of the Swedish patient, who has had type 1 diabetes since 1987.
Three (3) months after transplantation, a dual positron emission tomography and MRI scan revealed the cells were still ensconced in the patient’s arm muscle. Tests for a marker of insulin production indicated they were manufacturing the hormone. To determine whether the beta cells were eluding the immune system, the researchers isolated and studied immune cells from the patient’s blood. These cells immediately pounced on genetically unaltered donor beta cells but left genetically engineered beta cells alone. And the patient did not make antibodies against the engineered cells, another sign that his immune system was giving them a pass.
The man still has diabetes and has to take insulin to maintain his blood sugar. “We transplanted 7% of a curing dose” of the cells, Carlsson says. However, the patient also did not require immune-suppressing drugs. The side effects of the procedure, which included numbness at the injection site, were minor, Carlsson says. “To my mind, this is a huge success.”
Sana has released data for an additional three (3) months that suggest the transplanted cells continue to function and escape immune attacks; however, those results have not been vetted by independent scientists. Carlsson and colleagues will continue to monitor the patient for 15 years, as required by EU regulations. He remains the only person to have received the treatment.
The company is now pursuing a slightly different strategy that involves genetically engineering beta cells grown in culture from stem cells, which are easier to obtain in large numbers than donated beta cells, Carlsson says. Other research groups have already reported positive results for stem cell–based transplantation approaches. In June 2025, Boston-based Vertex Pharmaceuticals announced its experimental therapy had allowed 83% of patients in a clinical trial to stop using insulin injections. However, they required immunosuppressants.
The most impressive result from the study “is the ability of the cells to evade immune destruction. That is the brass ring” for treatments like this, says Pediatric Endocrinologist Taylor Triolo of the University of Colorado School of Medicine, who also was not connected to the work. She and Hering agree that researchers need to fill in more details, such as whether the cells can produce substantial amounts of insulin, whether they connect to blood vessels that can sustain them for the long term, and whether the immune system still attacks some of the transplanted cells. However, Triolo says, “We’ve been talking about cell therapy [in diabetes] for many years, and it’s exciting to see the field make some significant leaps forward.”
REFERENCE: Science; 04 AUG 2025; Mitch Leslie