Scientists from CytoTherapeutics Inc. (NASDAQ:CTII) and theHoward Hughes Medical Institute at the University of Washington,Seattle, reported in the March issue of the Proceedings of the NationalAcademy of Sciences (PNAS) the successful implantation of a capsulecontaining a cell line engineered to deliver stable quantities of humannerve growth factor (hNGF) into the brains of rats. "This encapsulatedxenogeneic system may provide therapeutically effective amounts of anumber of neurotrophic factors, alone or in combination, to virtuallyany site within the body," the researchers concluded.In the rat study reported in PNAS, the capsule was found to workeffectively after six months. "The hNGF cells themselves produce freshgrowth factor. In addition, the capsules may be engineered to containseveral kinds of growth factor to treat multiple symptoms," said E.Edward Baetge, senior director of research. "By protecting thecholinergic neurons in the basal forebrain, we believe this method canprevent the further loss of cells that die as in Alzheimer's and otherneurodegenerative diseases."CytoTherapeutics of Providence, R.I., is a biopharmaceutical companythat develops implantable systems to deliver biologically active celland gene therapy products for central nervous system diseases andother chronic disorders.The company recently announced that it has signed an exclusiveagreement with South San Francisco, Calif.-based Genentech Inc. todevelop such products. CytoTherapeutics plans primate trials before itwill consider filing an investigation new drug application.Use of implantable capsules directly in the brain eliminates theproblem of overcoming the "blood-brain barrier," the method by whichthe brain protects itself from foreign agents. However, it also makes itdifficult for therapeutic agents to be administered systematically totreat central nervous system disorders.The capsule developed by CytoTherapeutics contains a cell line thatsecretes the human form of hNGF into the brain. The capsule is 5 mmin diameter and about as long as a grain of rice. It has a porousstructure that allows only the smallest molecules to pass through it intothe brain. The implant developed by the company allows onlymolecules with a 100,000 molecular weight to pass through.According to the company, a unique feature of its implant is that it usesan animal-derived cell that has been engineered to be able to secretehuman NGF. By using baby hamster kidney cells, the company haseliminated the need to rely on human tissue and can create a limitlesssupply in the laboratory, according to Elizabeth Razee, manager ofcorporate communications.Another feature of the capsule is that it is equipped with a silicone"tether" that allows it to be easily extracted from the brain cells whennecessary."We believe that this operation may ultimately be performed on anoutpatient basis," Razee said. "A similar capsule containing bovineadrenal chromaffin cells that we produced was administered to ninepatients being treated for acute pain in Switzerland and they weredischarged within 24 hours."
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