Encapsulated Pig Islet Cells For Diabetes Type 1 – A Trial

[Stephen C Schimpff]

Here is a follow-up to the post on islet cell xenotransplantation for type 1 diabetes mellitus. A group in New Zealand has been studying the use of islet cells derived from pigs which have not been genetically modified. The cells are encapsulated to protect them from immune cells. The company reports that they are self regulating (meaning that they will produce insulin as needed based on the body’s blood sugar levels) and efficient at secreting the insulin produced into the patient’s body. The investigators report on one patient that is now nearly 10 years since transplantation with persistent functioning islet cells. Dr John Baker and Living Cell Technologies are conducting the human trial after having tested their product in multiple animal models. The material below, taken from the US National Institutes of Health Clinical Trials web site [http://tinyurl.com/2fmcnp6 ], was prepared by the company and its investigators:

“Intraperitoneal islet transplantation has the potential to ameliorate type 1 diabetes mellitus and avert the long-term consequences of chronic diabetes which cannot be achieved by conventional insulin treatment.
As donor human islets are not available in sufficient numbers, porcine islets are the best alternative source as they are recognised as the most physiologically compatible xenogeneic insulin-producing cells. Although the use of pig-derived cells raises the risk of xenotic infections, this can be minimised by obtaining cells from designated pathogen-free (DPF) animals bred in isolation and monitored to be free of specified pathogens. The worldwide experience to date in more than 200 patients who have received transplants of pig tissue has not demonstrated evidence of transmitted xenotic infections.
As animal-derived tissues have to be protected from immune rejection when transplanted into humans, transplants are usually accompanied by immunosuppressive therapy. However, porcine islets are preferably transplanted without the use of immunosuppressive drugs which cause significant morbidity. To protect them from immune rejection, the islets can be encapsulated in alginate microcapsules which permit the inward passage of nutrients and glucose and the outward passage of insulin. Alginate-encapsulated porcine islets transplanted without immunosuppressive drugs have survived rejection for many months in animal studies, and have been retrieved from a diabetic patient over 9.5 years after intraperitoneal transplantation and shown to contain viable islets that stain positive for insulin.
DIABECELL® comprises neonatal porcine islets encapsulated in alginate microcapsules. DIABECELL® has been safely transplanted in healthy and diabetic mice, rats, rabbits, dogs and non-human primates. Following DIABECELL® transplants, the requirement for daily insulin was significantly reduced in diabetic rats and non-human primates.
The optimal dose and frequency of transplantation of the current DIABECELL® preparation for the treatment of type 1 diabetes in humans can only be determined in clinical trials. The intention of this phase I/IIa clinical trial is to obtain at least 52 weeks safety and preliminary efficacy data in type 1 diabetic patients following transplantation of a single low effective dose of DIABECELL® into the peritoneal cavity.”
The results of this study, still a few years off, will be of great interest to those whose diabetes is hard to control with standard insulin approaches.