The biotech company Pluristem Therapeutics, formerly known as Pluristem Life Systems, has been granted patent # 7,534,609 for a method of expanding undifferentiated hemopoietic stem cells.
Pluristem Therapeutics specializes in the development and commercialization of allogeneic (in which the donor and the recipient are not the same person) cellular therapy products derived from the human placenta for the treatment of severe ischemic autoimmune disorders such as multiple sclerosis, peripheral artery disease, ischemic stroke, inflammatory bowel disease including Crohn’s disease, and others. The company’s proprietary technology includes a 3D bioreactor, PluriX, which simulates the microenvironment of bone marrow substrates for the large-scale culturing and three-dimensional expansion of stromal cells without the need for supplemental growth factors or other exogenous materials. The cells generated by PluriX, known as "PLX" (PLacental eXpanded) cells, not only possess "immune privileged" properties but also immunomodulatory properties as well, and are expandable in vitro without exhibiting phenotypic or karyotypic changes. This new patent, however, was awarded to Pluristem for an invention involving methods and materials by which undifferentiated hemopoietic stem cells may be expanded in a novel type of bioreactor which is separate and distinct from the PluriX.
Pluristem Therapeutics is focused on the development and commercialization of off-the-shelf allogeneic cell-based therapies for the treatment of chronic degenerative ischemic and autoimmune disorders. As described on their website, Pluristem specializes in adherent stromal cells (ASCs) that are derived from the human placenta and which "are multipotent adult stem cells that have strong anti-inflammatory properties and can regenerate and repair damaged tissue." ASCs have already been shown to differentiate into nerve, bone, muscle, fat, tendon, ligament, cartilage and bone marrow stroma. Additionally, since they have low immunogenicity, ASCs do not require HLA (human leukocyte antigen) matching and are not at risk of being rejected by the patient’s immune system. After the ASCs are harvested from placental tissue, the cells are then expanded three-dimensionally into the PLX cells via the company’s proprietary PluriX 3D bioreactor, in which the cells are able to excrete their own cytokines and other immune modulators without the need for risky supplemental growth factors nor other exogenous materials. As adult stem cells that are derived from the human placenta, which is an extremely rich source of non-embryonic stem cells, ASCs are also ethically non-controversial in addition to being highly potent adult stem cells.
As stated on Pluristem’s website, "The Company has made a strategic decision to work only with adult stem cells since the practical use of embryonic stem cells is severely restricted by various religious, ethical and legal considerations."
In a manner which is similar to that by which the PluriX bioreactor three-dimensionally expands ASCs into PLX cells, the new invention allows undifferentiated hemopoietic cells to be expanded three-dimensionally upon stromal feeder cells, without undergoing differentiation. At least theoretically, such a bioreactor could be adapted to any type of cell, and a reviewer of the patent in StemCellPatents.com suggested the applicability of the bioreactor to the expansion of embryonic and iPS cells.
In separate though related news stories, earlier this year Pluristem received approval to begin clinical trials for the treatment of critical limb ischemia with its proprietary adult stem cell product PLX-PAD, an allogeneic placental-derived stromal cell product. In May of 2009, Pluristem also announced the selection of a major clinical site in North Carolina for the PLX-PAD Phase I clinical trial, which will be conducted at Duke University Medical Center. According to Zami Aberman, president and CEO of Pluristem, "We are very pleased to be working with Duke University Medical Center on the Phase I clinical trial using our PLX cells and believe that being involved with such a prestigious, reputable institution emphasizes the important therapeutic future for our mesenchymal-like stem cells."
According to Duke University cardiologist Dr. Robert Mitchell, the principal investigator for the PLX-PAD trial, "We look forward to collaborating with Pluristem in studying this interesting potential approach to dealing with limb ischemia. This is an oftentimes devastating disease and beginning the process of understanding the action of these cells in a Phase I clinical trial is an important step forward."
In the U.S. alone, it has been estimated that as many as 12 million people suffer from critical limb ischemia (CLI), an advanced form of peripheral artery disease (PAD) that is associated with high rates of morbidity and mortality, often resulting in amputation and frequent hospitalization. Although standard medical therapies are currently ineffective in treating CLI, the market value for an effective CLI therapy has been projected to be over $1 billion. For the first time, cell-based therapies such as Pluristem’s PLX-PAD offer a potentially safe and effective treatment of a life-threatening medical condition which previously has been incurable.
In addition to its cell-based therapy for CLI, Pluristem is currently developing other adult stem cell products for the treatment of other degenerative, malignant and autoimmune disorders. The company’s first product, PLX-BMT, was directed at improving the engraftment of hematopoietic stem cells derived from umbilical cord blood as an alternative to bone marrow transplantation.
Although the company’s most recent patent, for a method of expanding undifferentiated hemopoietic stem cells, was awarded on May 19, 2009, the patent application was originally filed on April 11, 2005, at which time the company was known as Pluristem Life Systems. On November 26 of 2007, however, corresponding to a reverse stock split and the designation of a new ticker symbol, the company also announced the official change of its name to Pluristem Therapeutics.
(Please see the related news article on this website, entitled, "Pluristem to Begin Adult Stem Cell Clinical Trials for Critical Limb Ischemia", dated January 13, 2009).