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New Cell-Based Therapy Drives Progress Toward Diabetes Treatment, Prevention

Peter Cook and Martina Hunt

Sept. 15, 2023 – Using new gene-editing techniques, researchers in Seattle Children’s Research Institute’s Center for Immunity and Immunotherapies (CIIT) have created a novel cell-based therapy with the potential to transform the treatment and/or prevention of Type I diabetes, as well as other autoimmune, allergic and autoinflammatory diseases.

Type 1 diabetes — the kind usually seen in children, teens and young adults — is caused by an autoimmune reaction in which the body mistakenly attacks itself. Over time, this reaction destroys the pancreatic cells (islet cells) that make insulin. Insulin helps blood sugar enter the cells to supply energy. Without insulin, blood sugar can’t get into cells and builds up in the bloodstream. High blood sugar is damaging to the body and causes many of the symptoms and complications of diabetes.

Regulatory T cells (Tregs) and effector cells keep a healthy immune system in balance. Effector cells promote beneficial immune activation and inflammation, and Tregs suppress potentially disease-causing immune activation and promote tissue repair. In autoimmune, alloimmune and inflammatory diseases, this balance is disrupted when the activity or number of Tregs is not sufficient to keep disease-inducing immune effectors in check. Treg therapies aim to restore this balance by providing an external source of healthy Tregs engineered for optimal activity.

The lab team of CIIT Director Dr. David Rawlings and colleagues have made major advances in engineered regulatory T cells (EngTreg) to treat autoimmune diseases, including Type 1 diabetes. Two papers describing these pioneering achievements were recently published in the journal Molecular Therapy. The first, by lead author Peter Cook, a senior scientist in the Rawlings Lab, involved creating a novel designer protein that strengthens EngTregs’ therapeutic ability. The second paper, by first author Martina Hunt, a research scientist in the Rawlings Lab, describes a single-step, multi-engineering strategy to efficiently manufacture this highly specialized therapeutic cell product.

These developments build on a series of EngTreg innovations by the Rawlings team. They previously described a novel gene-editing strategy to generate EngTregs from CD4 T cells and then created an islet-specific EngTreg that used a lentivirus to deliver a T-cell receptor (TCR) that targeted the cells to the pancreas and blocked diabetes onset in a mouse model.

A major, previously unsolved hurdle in Treg therapies is that Tregs are entirely dependent on IL-2, a protein that functions as a chemical messenger and keeps them alive. However, Tregs cannot make their own IL-2 so they must rely on other cells making it and must compete for it. Rawlings and colleagues invented a platform called a chemically inducible signaling complex (CISC) to promote Tregs’ survival and expansion. The CISC system gives an IL-2 signal specifically to the EngTregs so they preferentially survive, which improves their therapeutic potential. Without IL-2, the majority of Tregs were rapidly lost in previous clinical trials when they were transferred into patients.

Cook’s paper describes designing the CISC system so that it’s triggerable with very low levels of an immune-suppressive drug, rapamycin. The clinically approved drug is given in such a small dose that it does not suppress the immune system but is sufficient to bring the engineered proteins together to turn on the IL-2 signal.

“CISC is the real backbone for all of this work,” said Rawlings, who is also a professor in the departments of Pediatrics and Immunology at the University of Washington School of Medicine. “There is nothing equivalent to the IL-2 CISC in any previous T-cell product. It's the major distinguishing feature of our platform and is likely to make it much more effective clinically.

“Our method only turns on the IL-2 signal in our engineered therapeutic cells, so it's a cell-intrinsic way of giving IL-2 support. There are millions of dollars being spent by pharmaceutical companies trying to engineer IL-2 to make it specific to T regulatory cells. But none of those applications are specific enough because they turn on other cells that can cause or exaggerate disease. We get around that challenge by specifically giving our therapeutic cells an extra boost,” he said.

The second publication details a first-of-its-kind gene editing strategy by the Rawlings team that simultaneously achieves three goals: It generates EngTreg cells, it makes these cells specifically able to recognize a self-protein in the pancreas with the help of a TCR, and the cells express CISC, allowing for more than 95% purification and improved stability and survivability. This work provides a robust strategy to specifically enrich for editing of two different genes at the same time.

“An EngTreg needs two things to do its job, and our dual-editing approach gives it both of those things,” Rawlings said. “One is the ability to get this unique IL-2 signal to survive and expand, and the other is the T-cell receptor specific to the autoimmune disease that we’re treating — in this case, diabetes.”

The manufacturing system produces highly purified regulatory cells that, when given to a patient, are expected to reliably go to the pancreas and survive.

Based on earlier work from the Rawlings Lab, the researchers knew that antigen-specific EngTregs are highly effective in turning off attacking cells that cause islet damage once they reach the pancreas. Rawlings believes islet-specific EngTreg expressing CISC will be even more effective, and he predicts they will benefit patients with newly diagnosed Type I diabetes, as well as children with only the very early features of disease who have not yet developed abnormal blood sugar levels. Someday, this cell therapy may be used to prevent and eliminate diabetes in at-risk children.

Gene editing to generate cell-based therapies is a new and rapidly developing field of medicine. While disrupting genes is relatively straightforward, adding new cell functions by gene editing is much more technically complex.

“For Peter and Martina, this was a three-year process of fiddling around until we got this working right,” Rawlings said. “It wasn’t an easy engineering feat. We had to try a lot of different versions to get the laboratory ‘Legos’ in the right place so that when we did the editing, it worked.”

Together, these findings detail a strategy for generating a potentially revolutionary cell-based therapy for Type I diabetes as well as other autoimmune, allergic or autoinflammatory diseases, such as lupus and multiple sclerosis.

The research team is partnered with biotechnology start-up GentiBio, a Seattle Children’s Research Institute spin-out, of which Rawlings is a scientific co-founder. He said GentiBio is moving rapidly toward a clinical trial using these antigen-specific EngTregs for treatment of Type I diabetes. For the trial, GentiBio will take T cells from a Type I diabetes patient and use gene editing to convert the cells into immunosuppressive cells designed to shut down the autoimmune process behind diabetes when they’re transferred back into the patient.

Though this is currently designed as an individual therapy, Rawlings envisions a day when such therapies are mass-produced.

“As the field moves to making off-the-shelf T-cell therapies, this approach with CISC will be very important to give those cells a longer lifespan in the allogeneic [cells come from a different person than the one who receives the cells] setting,” he said. “It's not restricted to be used only in the individual therapeutic.”

For the first paper, Children’s contributing authors include Andrea Repele, Travis Drow, Annaiz Grimm, Noelle Dahl and Karen Sommer, all of the Rawlings Lab, and Dr. Andrew Scharenberg. Former lab members Su Jung Yang, Samuel West, Li-Jie Wang, Chester Jacobs and Ahmad Boukhris also contributed to the work.

Children’s contributing authors for the second paper include Cook and Boukhris, as well as collaborators at Benaroya Research Institute (BRI), including Dr. Jane Buckner, BRI president. BRI tested the functionality of the cells and provided the TCR for the research.

Both research projects were supported by grants from The Leona M. and Harry B. Helmsley Charitable Trust, GentiBio, the Seattle Children's Research Institute Program for Cell and Gene Therapy, the Children’s Guild Association Endowed Chair in Pediatric Immunology and the Hansen Investigator in Pediatric Innovation Endowment.

— Colleen Steelquist