Protein Polymer Presents Data on Tissue Engineering, Surgical Adhesives and Protein Polymer Hydrogels

    SAN DIEGO, April 27, 1998 -- Protein Polymer Technologies, Inc. (Nasdaq: PPTI), presented on Saturday data on the comparative performance of the Company's surgical adhesives and sealants, and on the mechanical properties of its Silk-Elastin hydrogels being developed as tissue augmentation agents in the treatment of female stress urinary incontinence and for cosmetic and reconstructive medical procedures.  Previously, the Company presented results from a study of tissue engineered wound healing matrices. All three presentations were made at scientific sessions of the 24th Annual Meeting of the Society for Biomaterials in San Diego, CA.
    Joseph Cappello, Ph.D., Vice President of Research and Development, presented test results from a comparative study of the bond strengths of different types of surgical adhesives and sealants.  In this study, PPTI's adhesive was found to be stronger than fibrin sealants and cyanoacrylate adhesives as well as creating more flexible and extensible bonds, all conditions important to successful wound closure and healing.  PPTI's adhesives are engineered to chemically cross-link to the body's tissue, enabling the creation of bonds between tissue layers that are superior in both strength and flexibility to other sealant and adhesive products.  PPTI's engineered adhesives are being developed to replace or augment the use of sutures and staples in a variety of surgical wound closure applications.
    Dr. Cappello, in a presentation last Thursday entitled "Protein Polymer Porous Scaffolds for Tissue Engineering," discussed the results of in vivo animal implant studies in which PPTI's resorbable porous sponges were found to increase the rate of wound healing.  As reported, the results were due to the ability of the sponges to provide more uniform surface area for new granulation tissue to infiltrate, causing the cellular re-epithelialization of the sponge, and thus leading to the deposition of new collagen within the sponge's pores.  In these studies, PPTI's sponges demonstrated excellent biocompatibility and persisted longer during the wound healing process, as compared to collagen sponges.  PPTI's sponges are expected to be used as scaffolds for the regeneration of tissues.
    Stephen Kennedy, Ph.D., a Senior Research Scientist at PPTI, Saturday presented the results of a series of studies on the mechanical properties of hydrogels from Silk-Elastin protein block copolymers.  PPTI's injectable hydrogel technology relies on the ability of these unique polymers to be injectable as a liquid at room temperature, and then to irreversibly form a gel at body temperature.  By controlling both the structure of the protein blocks and conditions involved in product formulation, Dr. Kennedy hypothesized that the rate of gel formation, the strength of the gels, and the rate or degree of resorption can be predicted and controlled.  These hydrogels are being developed as bulking agents for cosmetic, reconstructive and urological applications.  PPTI anticipates obtaining FDA's approval of an IDE to begin pilot clinicals for urological indications before the end of 1998, and clinical testing of the cosmetic/reconstructive indications to begin in early 1999.
    Protein Polymer Technologies, Inc., a San Diego-based biotechnology company, has a technology platform that allows the creation of a number of different classes of biocompatible polymers that enable cell growth, promote the regeneration of tissue, bond to synthetic surfaces, and are resorbed by tissue at controlled rates.  PPTI's lead programs include a new generation of surgical adhesives and sealants to replace or augment the use of sutures and staples, and unique hydrogels that can be injected as liquids, but form pliable, irreversible gel structures once body temperature is reached.
    This press release may contain forward-looking statements that are based on management's expectations. Actual results could differ materially from those expressed here; further, the Company is not obligated to comment specifically on those differences.  Risks associated with the Company's activities include raising adequate capital to continue operations, scientific and product development uncertainties, competitive products and approaches, continuing collaborative partnership interest and funding, regulatory testing and approvals, and manufacturing scale-up.  The reader is encouraged to refer to the Company's 1996 Annual Report and 10-KSB, and recent filings with the Securities and Exchange Commission, copies of which are available from the Company, to further ascertain the risks associated with the above statements.