| Progenitor's Stem Cell Technology Granted U.S. Patent 
 MENLO PARK, Calif.--(BW HealthWire)--April 28, 1998--Progenitor, Inc. (Nasdaq: PGEN - news, PGENW - news)
 today announced that the United States Patent and Trademark Office has issued a patent (US Patent No. 5,744,347) relating
 to isolation, culture and compositions of stem cells capable of developing into blood, immune or blood vessel cells.
 
 These stem cells may have potential therapeutic uses in bone marrow transplantation, as vascular grafts and coatings, and as
 cell-based gene therapy vectors for blood and immune disorders. The stem cells also may be used in experimental systems for
 the discovery of novel growth factors that promote blood cell development (hematopoiesis) or blood vessel formation
 (angiogenesis), for treatment of cancer or cardiovascular disease.
 
 ''This technology provides clear examples of the broad therapeutic potential of developmental biology,'' said H. Ralph
 Snodgrass, Ph.D., Vice President, Research and Chief Scientific Officer. ''We're currently focusing on these cells as a source
 of novel hematopoietic factors. Progenitor is using proprietary methods to analyze gene expression in small samples of
 differentiating yolk sac stem cells to isolate regulatory genes active at discrete stages of development. Identification of the
 factors that trigger differentiation into specific types of mature blood and immune cells may provide new leads for support
 therapies in bone marrow transplantation and cancer, and treatments for anemias and other blood disorders.''
 
 Researchers at Progenitor have devised methods for isolating this unique class of stem cells from the yolk sac, a tissue that
 appears very briefly accompanying the early development of mammals. The yolk sac is both the starting point for the circulatory
 system, and the source of blood and immune cell precursors that eventually migrate to the bone marrow to form the
 hematopoietic system of the mature animal. Progenitor captures yolk sac stem cells at a critical transient stage, when the yolk
 sac exhibits hematopoietic and angiogenic potential, but the cells have not yet acquired the immunological features of mature
 cells that lead to rejection or graft-versus-host disease when transplanted.
 
 Progenitor has demonstrated that yolk sac stem cells can be grown in long-term culture and maintained in an undifferentiated
 state. The cells can be induced to differentiate into blood and immune cells upon addition of certain growth factors. Under
 certain culture conditions, the cells also can be induced to form tubular structures with characteristics of rudimentary capillaries.
 The cultured stem cells also serve as a source for the discovery and functional characterization of novel hematopoietic and
 angiogenic growth factors.
 
 Thomas E. Wagner, Ph.D., of the Edison Biotechnology Institute of Ohio University (Athens, OH), and Progenitor's scientific
 founder, is a co-inventor of the patented technology. Ohio University, which owns the patent, has granted Progenitor an
 exclusive worldwide license to the technology. Progenitor also has exclusive worldwide rights to an earlier US Patent issued to
 Dr. Wagner and colleagues (No. 5,032,407), for methods of using yolk sac stem cells for the transfer and tissue-specific
 expression of therapeutic genes.
 
 Progenitor discovers and develops genomic leads and targets for new pharmaceuticals using a unique technology platform that
 combines developmental biology and disease genetics to identify, characterize and utilize key genes responsible for health or
 disease. Progenitor's genomic discoveries provide multiple product opportunities which the company pursues through a
 combination of partnerships, licenses and retained rights for internal product development programs.
 
 Except for the descriptions of historical facts contained herein, this news release contains forward-looking statements that
 involve risks and uncertainties as detailed from time to time in Progenitor's SEC filings under the Securities and Exchange Act
 of 1934, including the early stage of development of Progenitor's technology; need for additional funds; patent, regulatory and
 competitive risks; dependence on third parties; product liability; and other risks.
 
 Contact:
 
 Progenitor, Inc.
 Lawrence K. Cohen, 650/614-7003
 H. Ralph Snodgrass, 650/614-7058
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