Cell help for diabetes

Clinical trials designed to cure type 1 diabetes with insulin-producing cells derived from stem cells are slowly ramping up.

Our best hope for curing type 1 diabetes is transplants of insulin-producing pancreatic beta cells created from induced pluripotent stem cells (iPSCs). So how’s that quest going? Some recent highlights:

The lead player is Vertex, whose VX-880 clinical trial has produced encouraging preliminary results. The Boston biotech giant is enrolling a few more patients for this study and seeking FDA approval for another trial that would protect the transplanted cells not with the usual immunosuppression drugs but within a protective device whose design has never been published.

Vertex bought Viacyte, the first major player in cell therapy for diabetes and Vertex’s most likely competitor, in September. Viacyte had partnered with CRISPR Therapeutics on the first-ever trial with beta cells that had been genetically modified to minimize the need for immunosuppression. I haven’t seen any public update on the status of that trial, which had planned to recruit 40 volunteers.

In November, the FDA gave Sernova of London, Ontario a thumbs-up to recruit up to seven more patients for the type 1 trial of its Cell Pouch system. “The Cell Pouch is made of cylindrical chambers of polymers with removable plugs that are implanted against the abdominal muscle and become wrapped with blood vessels,” says the company. Surgeons then remove the plug and transplant islet cells (beta cells and their hormone-producing pancreatic neighbors). These cells will come from human cadavers, the default source until now. The latest trial recruits will be given an updated version of the Pouch. Sernova expects to release early clinical results for that cohort this year.

iPSC-derived pancreatic islet cells manufactured by Evotec in Hamburg, Germany, will replace the donor cells in Sernova’s next clinical trials. The two companies plan to seek regulatory approvals for this round in 2024.

Sernova also is working with the lab of Alice Tomei at the University of Miami on a way to shield transplanted islet cells against immune system attack with a “conformal coating” of hydrogels that encapsulates the cells. This procedure has an encouraging history of results with animal models.

With iPSC-derived cells now commercially available from Evotec and other suppliers, solving this immunosuppression puzzle seems to be the one remaining (huge) barrier to successful cell therapies for type 1 diabetes. It’s particularly tough in this illness because the immune system is already fully geared up to wipe out the patient’s own beta cells.

Startup firm iTolerance is taking another approach to protectively wrapping the transplanted cells, with a technique that performed well in a study of macaque monkeys over six months. The strategy is based on a protein called Fas that is expressed on the surface of T cells; those cells die if a Fas ligand (FasL) protein binds to the Fas protein.

The researchers whipped up a dual-protein combination of FasL and streptavidin, a protein that dampens T cell activation and proliferation. These protein combos were attached to microgel beads, then mixed with islet calls “and then transplanted to a bioengineered pouch formed by the omentum—a fold of fatty tissue that hangs from the stomach and covers the intestines.” (Yes, it’s hard to visualize the omentum; islet transplants traditionally have gone into the liver.)

This work was a joint project among investigators at Georgia Tech, the University of Missouri, Massachusetts General Hospital and other institutions. Camillo Ricordi of the University of Miami, a prominent pioneer in diabetes and cell therapy studies, is chief scientist for the Miami-based iTolerance.

Delivering FasL locally like this should work out better than genetically modifying islet cells to over-express the protein, which doesn’t always work out in immunosuppression experiments, the researchers suggested.

But other approaches to gene therapy for immunosuppression keep marching ahead. One group is targeting the A20 protein, which is “like a thermostat for the immune system; it can turn it down to a simmer, or ramp it up to be more aggressive,” according to Shane Grey at Sydney’s Garvan Institute of Medical Research.

Grey and colleagues have followed this track for many years, with promising early results for diabetes in mice, and in human and pig cells. “The genetically engineered cells seem to re-educate the immune system to accept the transplant as self,” Grey commented in a news release. “The transplant can tweak the whole immune system.” The Royal Adelaide Hospital in Adelaide, South Australia will kick off a trial with A20-enhanced islet cells in mid-2024.

Perhaps more dramatically, this month stem cell maestro Doug Melton and co-workers published research on a Swiss army knife approach to genetically modifying human islet cells to become “immune-tolerizing”. The scientists modified the cells to target human leukocyte antigens (keystones in activating T cells) and the PD-L1 immune checkpoint protein and to secrete three cytokines that help to recruit regulatory T cells to protect the transplanted islets. This seemed to work quite well in humanized versions of the standard mouse model for type 1 diabetes.

“Overall, our approach may eliminate the need for encapsulation or immunosuppression, a longstanding goal of the islet transplantation field,” the researchers wrote. Maybe it’s no coincidence that Melton announced plans to leave the Harvard Stem Cell Institute for Vertex last April, just about the time this paper was submitted.

About 8 million people worldwide live with type 1 diabetes, with half a million more diagnosed each year. So says the Type 1 Diabetes Index, which predicts this population will soar to more than 13 million people by 2040. (And maybe 10 times more people with type 2 diabetes will need insulin by then.) Let’s hope that actual cures will be widely available and affordable many years before that.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s