Two patients participating in a clinical trial studying a cell therapy as a new treatment for type 1 diabetes have died following the administration of modified stem cells. Although the pharmaceutical company claims that none of the deaths are related to the therapy, they have chosen to pause the program.

One of the deceased is Brian Shelton, the first person to be cured of type 1 diabetes after being treated with this therapy and who had begun to produce his own insulin six months after being treated with VX-880.

Vertex Pharmaceuticals’ drug, VX-880, has proven very successful in eliminating the need for insulin administration in a small group of patients. The therapy is based on obtaining islands of cells derived from stem cells (known as stem cells) and placing them in the patient’s liver along with immunosuppressants, the same drugs that a person would receive if undergoing an organ transplant.

As Professor Douglas A. Melton, co-director of the Harvard Stem Cell Institute, states, “in the second procedure, the same cells are placed in a device, a kind of tea bag. In this case, immunosuppressants are not required, since the cells are protected within the device and cannot be rejected by the immune system.”

Furthermore, with this regenerative therapy the ability to create transplantable insulin-producing cells eliminates the need to depend on organ donors.

The study involved 14 patients with type 1 diabetes and by the end of 2023, three of them, including the late Brian Shelton, managed to avoid insulin injections 180 days after the transplant.

The Vertex company has not provided any information about the other participant who died, and while the study is on hold, no new patients will be able to start VX-880 therapy. However, the trial continues with the rest of the participants, who will continue the treatment. According to Vertex, VX-880 is well tolerated by patients and has no serious side effects.

Another similar case

We recently reported another similar case at the Bioethics Observatory, that of a patient who voluntarily participated in a gene editing trial against LDL cholesterol. On this occasion, the volunteers participating in the study had high levels of LDL cholesterol. They received an injection of VERVE-101 to deactivate the aforementioned gene.

Subjects initially had their LDL reduced by up to 55% after 28 days. Prior to the experiment, their plasma level was twice the usual level.

Six months after the injection, participants who received a high dose of VERVE 101 still had lower LDL levels, however, they suffered from chills, fever and headaches, flu-like symptoms, accompanied by an increase transient in liver enzyme levels. Most seriously, one of the 10 patients died of a heart attack five weeks later, while a second participant suffered a heart attack one day after the injection.

Bioethical assessment

Progress in regenerative therapies with stem cells opens up a promising horizon for curing diseases for which this possibility did not exist until now. The successful results of other types of therapies, those that modify genes responsible for certain pathologies, such as the treatment for sickle cell anemia, further broaden the therapeutic possibilities for hitherto incurable diseases. But some bioethical difficulties must be appropriately evaluated given the extension of these treatments.

In the case of regenerative therapies with stem cells, the use of embryonic stem cells, which use embryos left over from in vitro fertilization processes, that must be destroyed to obtain their pluripotent cells, should be avoided. However, the use of the patient’s own genetically modified cells avoids the destruction of embryos and improves the patient’s tolerance to treatment.

On the other hand, the risks involved in these processes should be properly assessed. The deaths recorded in some patients recruited in clinical trials for the treatment of dyslipidemia and diabetes make it necessary to adopt prudent positions until the cause of these deaths is clarified and their relationship with the administration of the drugs used can be ruled out.

Finally, both the monitoring of the patient’s evolution in the longer term and the necessary cost reduction seem to be necessary conditions for the definitive validation of these novel and promising therapeutic options.

Julio Tudela and Cristina Castillo

Bioethics Observatory – Institute of Life Sciences

Catholic University of Valencia


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