BBI Contributing Editor

NEW YORK – An impressive roster of 58 public and private companies involved in the development of tissue-engineered and stem cell-based products showcased their work to date and took a look into the future at Techvest LLC's (New York) second annual Tissue Repair, Replacement and Regeneration Conference, held here in November.

One of the first commercial applications investigated for tissue-engineering technology was for healing wounds. This sector was well-represented at the Techvest conference.

Organogenesis (Canton, Massachusetts) has pioneered the commercialization of a mass-produced product containing living human cells. Apligraf, its lead product, is a living skin substitute used for venous leg ulcers and diabetic foot ulcers. It is marketed by Novartis (Basel, Switzerland). Vitrix, a living dermal replacement, will soon enter pivotal trials. The company's pipeline includes a vascular graft coronary artery for bypass procedures and a liver assist device for providing temporary liver function.

Ortec International (New York) has completed clinical trials of its skin replacement dressing for use on donor sites in burn patients. The company expects to receive FDA market clearance for this product by the end of 2001. Ortec has also completed pilot studies on this product for the treatment of venous stasis and diabetic ulcers and is holding discussions with potential marketing partners. These products are based on Ortec's Composite Cultured Skin (CCS) platform technology that uses two layers of human-derived skin (dermal and epidermal) supported in a collagen matrix. Ortec is exploring the application of CCS for developing other tissue-engineered body parts such as tendons, ligaments, cartilage and blood vessels.

IsoTis (Bilthoven, the Netherlands) is marketing in Spain an autologous keratinocyte sheet for treating burns and a tissue-engineered cartilage. These products do not use a scaffold. The company is in the preclinical stage of development of biomimetic ceramic (calcium phosphate) products for the sustained release of therapeutic proteins. This program is in collaboration with Synthes Stratec (Oberdorf, Switzerland). Also under development, and licensed to Osteotech (Eatontown, New Jersey), is tissue engineered bone for use as fillers in maxillofacial and spinal surgery.

Reconstructive Technologies (Mountain View, California) is using its VeriSkin technology to grow autologous tissue outside the body in a bioreactor using a specimen of the patient's own skin. The company expects to enter clinical trials in 12 to 18 months. This approach contrasts with tissue-engineered artificial skin because it provides full-thickness skin and has all the structural elements of natural skin needed for a good cosmetic outcome. The company's In Vivo Cyclic tissue expansion technology uses cyclic mechanical force delivered by a computer-controlled bioreactor or tissue expander to stimulate cell proliferation and tissue growth either outside or within the body. Animal trials will soon begin. Reconstructive Technologies is collaborating with Inamed (Santa Barbara, California) for the use of this technology in breast reconstruction.

Also presenting at the conference were Advanced Tissue Sciences (La Jolla, California), Integra LifeSciences (Plainsboro, New Jersey) and LifeCell (Branchburg, New Jersey) were among other companies active in the development of tissue-engineered products for the wound healing sector.

Implants for surgery

Advanced Materials Design (New York) uses its proprietary polymerization technology to produce resorbable, tyrosine-based polymers that possess specified mechanical properties and mimic natural tissue. This family of polymers is being investigated for use in injectable and implantable products for sustained drug delivery (pain control), tissue generation and substitution. They are currently being evaluated by companies for use in cardiovascular (stents and vascular grafts) and orthopedic implants.

Orthovita (Malvern, Pennsylvania) is developing synthetic bone substitutes for treating spinal disorders and osteoporosis. The company uses nanoparticle technology, bioactive glass and calcium phosphate to produce its bone substitutes. Vitoss and Cortoss are synthetic cancellous bone for use as bone void fillers and bone grafts. Vitoss has a porous scaffold. It was recently launched in Europe. Orthovita has filed a 510(k) with the FDA for Vitoss and Cortoss, a two-part biocompatible cortical bone substitute formulated as an injectable paste. Rhakoss, a bioactive spinal implant, is being developed for use in patients with degenerative disk disease and for placement using minimally invasive surgery.

Isto Technologies (St. Louis, Missouri) is a newly formed company that is using proprietary technology for growing cartilage. Its initial products are a neocartilage allograft, an in vitro-produced articular cartilage for repair and replacement of injured or diseased joints, and a natural surgical adhesive (tissue transglutaminase) for use in implanting the allograft. The neocartilage is grown using chondrocytes isolated from knee cartilage obtained from pre-adolescent cadaver donors. It does not require a polymeric scaffold. The company will soon initiate a preclinical study in sheep.

GenSci Regeneration Sciences (Toronto, Ontario, Canada) calls itself "The OrthoBiologics Company" because it uses biotechnology to develop products for musculoskeletal repair, reconstruction and regeneration. It markets two demineralized bone matrix implants for bone regeneration, DynaGraft, sold by Johnson & Johnson's DePuy-Acromed unit (Raynham, Massachusetts) for use in spinal surgery and OrthoBlast for non-spine orthopedic applications. DynaFill and DynaCan are moldable mineralized bone grafting materials. The company is developing several bone growth factors, including a patented anabolic peptide, transforming growth factor (TGF) and bone morphogenic proteins, for use in osteoinductive implants.

Collagenesis (Beverly, Massachusetts) uses its tissue matrix technology platform to transform tissue into a variety of forms for diverse medical implant applications. Its collagen-based products include Dermalogen, an injectable dermal matrix for tissue augmentation; Dermaplant, an acellular dermal allograft prepared from donor skin, for use as an implant in plastic and reconstructive surgery; and DuraDerm and Urogen, injectable dermal allografts for treating female incontinence, which are distributed by C.R. Bard (Murray Hill, New Jersey) and American Medical Systems (Minnetonka, Minnesota), respectively, and are used for bladder neck slings and for pelvic floor reconstruction.

Urologen, a collagen bulking agent for injection into the urinary sphincter to control incontinence, is in human trials. The company also is exploring drug delivery, periodontal, gastroenterologic, orthopedic and ophthalmologic applications of its technology.

Selective Genetics (San Diego, California) is using its proprietary Gene Activated Matrix (GAM) targeting technology for site-specific gene therapeutics for tissue repair and regeneration. This application of gene therapy has an advantage over the direct delivery of therapeutic proteins. By transfecting repair cells with the gene for a therapeutic protein, the protein can be produced throughout the entire healing process. The company is developing products for hard tissue repair and has corporate alliances with Biomet (Warsaw, Indiana) for applying gene therapeutics to treat orthopedic conditions, and with Spinal Concepts (Austin, Texas) for developing a spinal fusion product that combines a therapeutic GAM with interbody infusion devices. Also under development are products for soft tissue repair such as accelerated healing of chronic dermal wounds, revascularization of ischemic peripheral and cardiac tissues, nerve regeneration and organ regeneration.

Cell therapy's wide range of applications

Cell therapy has emerged in recent years as a promising method of treating a wide variety of diseases, including diabetes, neurodegenerative disorders (e.g., Parkinson's disease and Alzheimer's disease), liver disease, hormonal imbalances and cardiovascular disease. Cell therapy entails the implantation of live cells that secrete bioactive agents and serve as artificial organs.

The greatest obstacle to cell-based therapeutics is the destruction of the transplanted cells by the recipient's immune system, with the exception of autologous cell therapies as in hematopoietic cell transplantation during chemotherapy or radiation therapy. Immunosuppression is used to prevent transplant rejection, but it increases the risk of infection.

The genomic revolution has yielded discoveries of genes that control the growth and differentiation of stem cells. These genes will facilitate the development of cell culture systems needed to deliver the promise of cell-based gene and tissue therapies.

Clark Colton, PhD, professor of chemical engineering at Massachusetts Institute of Technology (Cambridge, Massachusetts), made the opening presentation at the Techvest conference on progress and problems in developing bioartificial organs. He noted that islet transplantation has been under investigation for 25 years, but with little notable success. However, the feasibility of using islet replacement to eliminate insulin dependence was established last summer by researchers in Edmonton, Alberta, Canada. They succeeded in restoring normal blood sugar levels for a year or more in diabetic patients by transplanting islets obtained from organ donors. Each transplant patient required two or more pancreases, but only 4,000 pancreases are available from donors annually. An estimated 40,000 Type 1 diabetics and 300,000 Type 2 diabetics have complications that are sufficiently severe enough to justify receipt of a transplant.

Many companies working on cell therapy products are developing treatments for insulin-dependent diabetics. Alginate, a natural polysaccharide derived from sea kelp, is the predominant encapsulating material. It is used to form microcapsules of porcine pancreatic islet cells by Islet Technology (North Oaks, Minnesota), VivoRx (Santa Monica, California), Neocrin (Irvine, California), Encelle (Raleigh, North Carolina), Encapsulife (Nashville, Tennessee) and Sertoli Technologies (Cranston, Rhode Island). Solgene Therapeutics (Westlake Village, California) uses sol-gel microbeads as the encapsulant.

Ixion Biotechnology (Alachua, Florida), a subsidiary of Q-Med AB (Uppsala, Sweden), is developing somatic cells for the treatment of diabetes. It uses islet-producing stem cells technology licensed from the University of Florida (Gainesville, Florida). Ixion aims to optimize the growth of functioning islet cells in vitro from islet-producing stem cells or islet progenitors in its quest to overcome the shortage of transplantable islets. The company also is developing a product composed of explanted islets which are obtained from organ donors and are encapsulated in non-animal stabilized hyaluronic acid gels.

Osiris Therapeutics (Baltimore, Maryland) has proprietary technology for isolating, purifying and growing human mesenchymal stem cells (hMSCs), the progenitor cells that give rise to connective tissues including bone marrow stroma, bone, cartilage, ligament, tendon, muscle and fat. Initial efforts are focused on Allogen, hMSCs for the regeneration of bone marrow stroma which is in Phase II clinical trials, and OsteoCel, hMSCs for the regeneration of bone for both orthopedic and dental defects which is in a Phase I trial. Osiris also is conducting preclinical studies on the use of hMSCs for joint repair (Chondrogen), and for cardiac tissue regeneration after myocardial infarction (CardioCel), and for the delivery of replacement enzymes for inherited diseases such as Fabry's disease (Fabrogen).

Cell Sciences (Melbourne, Australia) has licensed technology from the Centre for Genome Research at Edinburgh University (Edinburgh, Scotland), the world's largest embryonic stem cell research institute. Embryonic stem cells retain the ability to form all cell types found in the body. Cell Sciences has established a high-throughput embryonic stem cell-based screening platform to identify key stem cell growth factors needed to deliver a range of embryonic cells for somatic stem cell-based gene and tissue therapies. The company has strategic alliances with Aventis (Strasbourg, France), Genentech (South San Francisco, California), Glaxo Wellcome (London), SmithKline Beecham (Greenford, England), BioTansplant (Charlestown, Massachusetts) and CuraGen (New Haven, Connecticut).

Cellular therapy for liver failure

More than 80,000 patients are hospitalized annually with acute liver failure. However, there are only about 4,500 donor livers available annually in the U.S. and more than 16,000 patients on the liver transplant waiting list.

Circe Biomedical (Lexington, Massachusetts) is conducting Phase II/III trials of its extracorporeal HeptaAssist liver support system for patients suffering from acute liver failure. The patient's plasma is circulated through a cartridge containing hollow fiber membranes that are surrounded by porcine hepatocytes.

Incara Pharmaceuticals (Research Triangle Park, North Carolina) is using human liver precursor cells (a mixture of hepatic stem cells and their early progeny) for the treatment of liver diseases. These are a subpopulation of cells in the liver that can differentiate into a variety of daughter cells that provide liver function. Incara plans to enter clinical trials this year to study the injection of human hepatic precursor cells as a treatment for children with life-threatening inherited genetic diseases and adults with chronic liver failure.

Nephros Therapeutics (Scotch Plains, New Jersey) is growing human renal stem cell isolates in monolayers on hollow fibers. These cells are incorporated into a proprietary Renal IVD (IntraVascular Delivery) system for replacing the kidney's hemodynamic hormonal and cell regulatory functions. This approach is believed to significantly reduce the cost of renal replacement therapy for acute and chronic renal failure patients and to prevent the downward spiral into multi-organ failure. Nephros' products are based on technologies licensed from the University of Michigan (Ann Arbor, Michigan).

Cellular therapy for neurological disorders

Layton Bioscience (Sunnyvale, California) is using LBS-neurons, human neuronal cells, for the treatment of neurological disorders caused by trauma or disease. The technology was licensed from the University of Pennsylvania (Philadelphia, Pennsylvania). A Phase IIa safety and feasibility study has been completed using LBS-neurons on stroke patients. Preclinical trials are being conducted on LBS-neurons for use in treating spinal cord injury, motor neuron disease and diseases of the eye. LBS-neurons can also be used as a platform for delivering genes to the central nervous system (CNS). One application that Layton Bioscience is investigating, under a Small Business Innovative Research grant from the National Institutes of Health (Bethesda, Maryland), is for the use of LBS-DA neurons to replace the brain's dopaminergic cells in Parkinson's disease patients. The company also has licensed and is developing neural stem cell technology from Children's Hospital (Boston, Massachusetts) for use against brain tumors.

Proneuron Biotechnologies (Rechovot, Israel) is developing cell therapies for treating a variety of disorders, based on research from the Weizmann Institute of Science on mechanisms in the dialogue between the CNS and immune system. Proneuron's strategy is to modulate the Immune Privilege mechanism to treat a range of acute and chronic neurological, ophthalmic and immune-related disorders. Its lead product is autologous activated macrophages, which is in Phase I clinical trials as a therapy for spinal cord injury. The company plans to submit an investigational new drug application this year for its neuroprotective T-cell therapy for protection against the spread of damage caused by the release of toxic substances from injured CNS tissue. The company plans to market its cell therapies by establishing Proneuron Cell Centers near medical centers.