Creating the next cell therapies for diabetes

As new encapsulation devices go on trial for type 1 diabetes, Vertex’s Doug Melton polishes strategies for insulin-producing cells that guard themselves against immune attack.

Two cell therapy candidates for treating type 1 diabetes took visible steps forward last week. Vertex Pharmaceuticals received Food & Drug Administration approval for a clinical trial of its VX-264 therapy, while Sernova announced that two patients in an ongoing trial received transplanted pancreatic islet cells in an upgraded version of its Cell Pouch capsule.

Vertex’s ongoing VX-880 clinical study, which combines stem-cell-derived islet cells with immune-suppressing drugs, in 2021 “cured” one patient of type 1 diabetes for at least several months. This drew great attention as the first clinical proof that stem-cell-derived islet cells could do useful work.

The VX-264 therapy now given an FDA green light employs the same cells but packages them in a surgically implanted “channel array” device. A VX-264 trial is already underway in Canada. The company expects to recruit about 17 volunteers globally.

As far as I know, Vertex has not released details on this device but it is based on an approach that began in the startup Cystosolv, which was acquired by Semma Therapeutics, which then was bought by Vertex. (Above, images of the approach in one perhaps-still-relevant patent.)

Sernova’s therapy is implanted in three steps: The Cell Pouch is surgically inserted, followed by two rounds of islet cell implants. The company expects to release interim results for this second cohort of patients by year-end. Its treatment uses cadaveric donor cells; Sernova plans to move future candidates to stem-cell-derived cells.

Also last week, Doug Melton outlined his research towards the next generations of stem-cell-drived cells during an American Diabetes Association webinar.

Melton, who led the development of stem-cell-derived insulin-producing beta cells for more than 20 years at Harvard and is on leave at Vertex, focuses on two main challenges. First, gaining complete mastery over cell composition. Second, eliminating the need for systemic immune suppression.

His group is bringing large-scale genetic screening to the job. “We can knock out one gene at a time in the embryonic stem cell stage, and then look for genes which improve composition or provide immune protection,” Melton said. “We’ve identified pathways that I had never thought about as being important for beta cell formation.”

He believes that optimal cell therapies will include the right mix of various types of hormone-producing pancreatic islet cells, not just the insulin-producing beta cells. Similar amounts of alpha cells, which produce glucagon that counter-acts insulin, also seem good. Additionally, there may be a helpful much smaller role for the delta cells that generate somatostatin, which inhibits the release of insulin, glucagon and other hormones. Other cell types should be weeded out.

While much work remains ahead, “we’re on the path to having complete mastery over the final composition of the stem-cell-derived product,” Melton said. “Now, how do we deal with this annoying immune system?”

Here his goal is genetically modified islet cells that provide some immune evasion, if not complete immune tolerance. Melton acknowledged that immunologists roll their eyes when he mentions immune tolerance, the Holy Grail for such therapies, but insisted that it may be achievable.

Many labs have pursued many ways to modify cells that might aid in dodging immune attacks. The standard method to evaluate these strategies for type 1 is by injecting candidate islet cells into an immuno-compromised mouse that models the disease. (“There’s no way in which it reproduces what happens in a human type one diabetic,” Melton commented. “Nevertheless, it’s a start.”)

“There’s nothing novel about this approach,” he commented. “The novelty comes from figuring out what is the right combination.” In one early but encouraging achievement, published in a January Cell Reports Medicine paper, one combo (below) engineered by his Harvard group greatly improved mouse survival over nine weeks.

In a separate Vertex effort based on its acquisition of Viacyte last year, the giant biotech is already enrolling patients for a clinical trial of VCTX-211, a “hypoimmune” cell therapy Viacyte created with CRISPR Therapeutics.

May all of these efforts point toward a real cure.

“My dream would be that when a young child is diagnosed with type one diabetes, the endocrinologist says, I’m sorry for you and your family, but I have good news for you,” Melton said. “I have here in my freezer some cells which will control your blood sugars, and your body won’t reject them for a long time. I’m going to inject them into your belly. And good luck, get back to kindergarten!”

“That sounds like a dream, and it is sort of a dream,” Melton added. “But I don’t see any reason we shouldn’t aim for that.”

P.S. Decades of experimentation with encapsulated cell therapies have not been encouraging. But Sigilon Therapeutics, another contender, hopes to ask the FDA next year to approve a type 1 trial with its “Shielded Living Therapeutics” 1.5mm alginate spheres. Sigilon argues (below) that its capsules will guard islet cells better than any modification of the cells themselves.

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