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Surgeons are master craftsmen. However, instead of working with metal, wood or plastic, they work with living tissues. Like carpenters, they use saws, chisels (knives) and drills to take things apart and fit pieces together. But they only have access to string (sutures) and nails (staples, pins, screws) to hold things in place. Furthermore, a surgeon's work is complicated by the biological healing response occurring when tissues are injured. This is one of the reasons why only a single sealant has been approved by the FDA for use inside the human body. As in everyday life, there are many surgical uses for glue where string and nails just don't work well. They may not be quick or easy enough to use; they may not be capable of staying in place; they may do more damage than desired; they and/or the tools to use them may not fit within the available work space; they may result in fluid or air leaks; or the "fit and finish" or healing response is just not satisfactory. Certain surgical adhesives and sealants that seek to avoid these limitations of conventional wound closure products, such as fibrin sealants and cyanoacrylate adhesives, have been developed and marketed outside the United States. However, it was not until May 1998 that the FDA approved Tisseel, a fibrin sealant, for use as an adjunct to control bleeding in surgeries involving cardiopulmonary bypass and the treatment of spleen injuries, and for closure of openings made in the colon. The Company believes that FDA approval is being sought for other fibrin sealant products. Although fibrin sealants have excellent hemostatic properties, they set slowly, have low strength, and lose their strength rapidly, which limits their use. Additionally, they are derived from human blood and may also contain animal-derived components. It was not until August 1998 that the FDA approved DermaBond™, a cyanoacrylate adhesive for topical application to close easily approximated surgical skin incisions and simple trauma-induced lacerations. Cyanoacrylate-based adhesives set fast and have high strength, but are toxic to certain tissues and form brittle plastics that do not resorb. These limitations restrict their use to bonding only the outer surfaces of skin together, and even then, not on joints or other locations requiring some degree of flexibility. A third category of tissue adhesives combines natural proteins such as collagen or albumin with aldehyde cross-linking agents in a non-resorbable matrix. Such products are marketed in Europe for very limited, life-threatening indications inside the body and have been recently reported to be under development in the U.S. However, a non- resorbable adhesive or sealant can only be used where the damaged tissues will not heal. Otherwise, a barrier to wound healing is unavoidably created. Additionally, the aldehyde cross-linking agents employed (i.e., glutaraldehyde, formaldehyde) are known to cause adverse tissue reactions. These surgical needs, and the limitations of the other types of products, set the stage for PPTI's product development focus. PPTI is seeking to develop surgical adhesives and sealants that combine the biocompatibility of fibrin glues (without the risks associated with use of blood-derived products) with the high strength and fast setting times of cyanoacrylates. Unique features include significant elasticity within the adhesive matrix (to move as tissues move) and the capability of tailoring the resorption rate of the adhesive matrix with the rate at which the wound heals. In September 1995, PPTI entered into a series of agreements with Ethicon, a subsidiary of Johnson & Johnson, regarding this program. Ethicon elected to terminate these agreements in December 1997. However, the Company has demonstrated both the adhesive performance and the biocompatibility of its product formulations in feasibility studies, including the resorption of the adhesive matrix in conjunction with the progression of wound healing. PPTI is committed to the commercial development of its adhesive and sealant technology, and is seeking to establish new strategic alliances with leaders in various surgical markets where the Company believes adhesive and sealant products will show superior performance to both conventional wound closure products and competing adhesive or sealant products. The product candidates the Company is seeking to develop are currently in feasibility testing. |
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The current market for wound care products is highly segmented, involving a variety of different approaches to wound care. Products currently marketed and being developed by third parties include fabric dressings (such as gauze), synthetic materials (such as polyurethane films) and biological materials (such as growth factors and living tissue skin graft substitutes). While the type of product used varies depending on the type of wound and extent of tissue damage, PPTI believes that a principal treatment goal in all instances is to stimulate wound healing while regenerating functional (as opposed to scar) tissue. The Company has developed protein polymers which it believes may be useful in the treatment of dermal wounds, particularly chronic wounds such as decubitous ulcers, where both reconstruction of the extracellular matrix (ECM) and re-establishment of its function are desired. These polymers, based on key ECM protein sequence blocks, are biocompatible, fully resorbable and have been processed into gels, sponges, films and fibrous sheets. The Company believes that such materials, if successfully developed, could improve the wound-healing process by providing physical support in situ for cell migration and tissue regeneration and as delivery systems for growth factors. Additionally, such materials may serve as scaffolds for the ex vivo production of living tissue substitutes. This program is in the early stages of research, which the Company has conducted, and continues to conduct, in collaboration with third parties. Such collaborations have primarily focused on the treatment of dermal wounds. |
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Oral delivery of drugs is the most preferred route of administration. However, for many drugs this is not possible and alternative drug delivery routes are required. Alternative routes include transdermal, mucosal, and by implantation or injection. For implantation or injection, it is often desirable to extend the availability of the drug in order to minimize the frequency of these invasive procedures. A few materials have been commercialized which act as depots for a drug when implanted or injected, releasing the drug over periods ranging from one month to several years. Other material and drug combinations are being developed by third parties. PPTI believes that the properties of these materials for such applications can be substantially improved upon, making available the use of depot systems for a wider range of drugs and applications. PPTI's soft tissue augmentation hydrogel technology, its surgical adhesive and sealant formulations, and its wound healing matrices all provide platforms for drug delivery applications, to serve as controlled release drug depots. The protein polymer materials the Company has developed exhibit exceptional biocompatibility, provide for control over rates of resorption, and are fabricated using aqueous solvent systems at ambient temperatures -- attributes which can be critical in maintaining the activity of the drug, particularly protein-based drugs emerging from the biotechnology industry. This program is in the early stages of research. For more information on drug delivery systems: Drug
Delivery Systems: Searching for Improved Bioavailability and a Higher
Therapeutic Index Researchers Advancing Biopolymer Systems as Vehicles for Delivering Drugs |
