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November 12th, 2012
As regular readers know, I believe that the best prospects for a near-term practical cure for type 1 depend on islet encapsulation technology. And I see this approach winning more and more support. The latest evidence that support is growing for encapsulation is a new grant by the California Institute for Regenerative Medicine (CIRM) to ViaCyte, Inc. of San Diego for preclinical studies of its system for delivering, via encapsulation, human islets developed from stem cells.
ViaCyte’s primary mission is to develop technology for transforming human stem cells into islets. To deliver the cells to patients they currently use an encapsulation technology named Encaptra.
The CIRM grant to ViaCyte is its fourth. CIRM is a public agency, which has sold bonds to fund stem cell research. (I don’t think this is a good model for funding research, but that’s a story for another post.) According to CIRM, ViaCyte received:
- in 2009, a Disease Team grant (“Cell Therapy for Diabetes”) in the amount of $19,999,937;
- in 2008, a Tools & Technology grant (“Development of the [REDACTED] Cellular Encapsulation System for Delivery of human ED Cell-derived Pancreatic Islets and Progenitors”) in the amount of $827,072;
- in 2009, an Early Transition grant (“Methods for detection and elimination of residual human embryonic stem cells in a differentiated cell product”) in the amount of $5,405,397;
- and finally, in 2012, a Strategic Partnership grant (“Preclinical and clinical testing of a stem cell-based combination product for insulin-dependent diabetes”) in the amount of $10,075,070: the purpose is “an array of detailed work on the exact format to be tested in humans needs to be completed and submitted to the FDA on the way to clinical trials.”
The total of these four grants, $36,307,476, represents 81% of CIRM funding for diabetes research (about $44 million). That’s an impressive concentration on a single approach.
The Encaptra encapsulation system has a long and tortuous history. Its first incarnation was invented in the 1970s by scientists at Baxter, Inc. in Round Lake, Illinois. Baxter had designed and built this device for delivery of cell products from its genetic engineering division but this was not successful. A joint venture with TransCell was formed (called Neocrin) to develop the device for diabetes. While curative in rodents, it never worked in larger animals, and never worked in any animal when it used primary islets—that is, islets isolated from an adult pancreas. The Neocrin team did succeed in converting the encapsulating membrane to one that would permit survival of xenograft cells, but testing was stopped because the device stimulated excessive host overgrowth. Neocrin returned the device to Baxter, which spun the technology out to TheraCyte (founded to market the device)—which is why it is often called the TheraCyte device.
ViaCyte deemphasizes the encapsulation technology, focusing rather on the stem cells. Its website does not even show the device, but rather a micrograph of the cells inside. Although I have seen photographs of Encaptra at meetings, I cannot find one online. ViaCyte says, “Encaptra® drug delivery system is manufactured from FDA compliant implant grade materials and is being designed with the goal of eliminating the need for continuous immunosuppressant drugs. The Encaptra® drug delivery system is optimized for release of insulin in response to the recipient’s blood glucose and designed for subcutaneous implantation providing complete containment of the product cells with full retrieval capability.”
This meshes with conversations I have had with ViaCyte scientists at scientific meetings. My impression is that they retained the basic concept of the TheraCyte device but reengineered it with new materials and brought manufacturing up to FDA standards. The cells they make from embryonic stem cells (ESCs) achieve their final maturating in the device, and the islets remain alive for months. ViaCyte believes that past failures with the TheraCyte device resulted from overloading and consequent islet necrosis.
ViaCyte was able raise money from CIRM because they are chiefly engaged in product development with ESCs. We have heard informally from CIRM that they could not fund Islet Sheet research because we do not work with ESCs. This is shortsighted on CIRM’s part, I think, but I do understand that they need to remain focused on their mission as sold to the taxpayers of California. The Encaptra device and the Islet Sheet are in the same class of encapsulation devices: namely, macro-capsules. But the materials used are quite different, and the sharpest difference is our approach to the nutrient/insulin exchange interface with the diabetic host.
Perhaps some day ViaCyte may find the Islet Sheet to be a useful alternative. In any case, it’s encouraging to see more funding in this area: besides the $10 million CIRM granted to ViaCyte, in August the Diabetes Research Institute (DRI) in Miami received $4.6 million. We are starting to get promising results from our first large-mammal studies in pigs, and I expect that investment in the Islet Sheet by funding institutions will grow over the next year.