Immunosuppression: Which approach will come closer to cure?
Thus far, the requirement for lifelong immunosuppression has meant that any islet cell replacement approach, including with stem cell–derived islets, has been limited to use in people with type 1 diabetes who have hypoglycemic unawareness or severely unpredictable blood glucose levels.
Two broad approaches are simultaneously being explored to overcome the rejection problem: Encapsulation of the cells to protect them from the immune system, and genetic modification of the cells so that they don’t provoke the immune system in the first place.
In 2022, Vertex plans to file an investigational new drug application for an encapsulated islet cell program with the FDA.
Dr. Markmann believes the genetic modification approach is more promising. “I’m not a believer in encapsulation. I think the foreign body response is hard to overcome. I think the answer will ultimately be genetically modifying the [cell] lines. ... The cell could express something that would potentially turn off the lymphocytes or interfere with the lymphocytes trying to attack them.”
Moreover, he said, “you don’t have to get rid of immunosuppression completely. It’s all [a] risk-benefit [equation]. Even if you could get it down to a single less-toxic [immunosuppressive] agent that would be a huge step.”
Dr. Shapiro commented: “All efforts and eyes are laser-focused on developing cells or approaches that will allow transplantation of this kind of stem cell without any immunosuppression or with low-dose immunosuppression that could be regarded as being exceedingly low risk.”
“Then, and only then, I think we could offer this kind of treatment to children who are just diagnosed with diabetes or to [a bigger proportion of] patients with type 1 or type 2 diabetes. ... The science has to be done in a step-wise fashion,” he added.
Microencapsulation, Dr. Shapiro noted, “is a big challenge because the process of capturing the cells and putting them into a device is really injurious to their survival. ... That may or may not work.”
Dr. Shapiro and his Edmonton team are now embarking on a new trial with ViaCyte and CRISPR Therapeutics using gene-edited cells that contain two knock-in genes and two knock-out genes shown to be less immunogenic and anti-inflammatory in rodent models.
“They look to be promising. We’re going to start a first-in-human trial in the next few months with those cells to see if they really are able to withstand a transplant without the need for immunosuppression. That will be a very exciting trial in itself,” Dr. Shapiro said, noting that they expect to enroll the first patients in the next few months.
However, he cautioned, “first we have to make sure that the gene-edited product continues to function in patients in the way that the original product did, that the cells survive, and that the gene modifications are actually effective. ... Maybe other iterations will be needed.”
“I think, as we move forward, we will ultimately have a gene-edited stem cell–derived product that is immune evasive and will survive. So, I’m ... optimistic that this is not as long term as you might think, and it’s ... happening much more rapidly – at least in first-in-human trials to test safety and preliminary efficacy.”
Dr. Shapiro is a consultant for ViaCyte.
A version of this article first appeared on Medscape.com.