Demeter BioTechnologies, Ltd. Announces its Peptidyl MIM Significantly Reduces Prostate Cancer Tumors & Mortality in Animal Models.

DURHAM, N.C.--(BW HealthWire)--July 23, 1998--Demeter BioTechnologies, Ltd. (OTC BB: DBOT) announced that D2A21, its lead anti-cancer Peptidyl MIM(tm) (Membrane Interactive Molecule), was effective in reducing prostate cancer primary tumors and metastases in animal models of prostate cancer.

The experiments were conducted at the University of Pittsburgh Cancer Institute, under the direction of Dr. Robert Getzenberg. In experiments in the Dunning rat model of prostate cancer, animals were given MatLyLu prostate adenocarcinoma cells, a very aggressive prostate cancer cell line that produces large primary tumors as well as lung metastases. Without successful treatment, mortality usually occurs within 30 days. Rats treated with D2A21 achieved a 60% reduction in the growth of primary tumors and a significant reduction in the number of lung metastases. D2A21 was administered intravenously at a low dose, of just 0.179 mg. per injection, that was effective without causing toxicity to the animals. Importantly, the survival rate increased from 25% for controls to 75% for D2A21 treated animals. In separate experiments, D2A21 has proven effective against prostate cancer in animals when given either intraperitoneally or subcutaneously.

Dr. Getzenberg, Director of Research at the University's Prostate and Urologic Cancer Center, said, "Against a very aggressive tumor cell line, Peptidyl MIM(tm) D2A21 demonstrates significant anti-tumor efficacy and halts the proliferation of metastases. Also, this compound utilizes a mechanism different from classical chemotherapy agents, and thus, could be effective for patients whose chemotherapy has failed." Getzenberg added, "We are enthused by the results thus far, and look forward to completing all of the preclinical testing and moving this compound into the clinic."

Demeter is looking forward to initiating human clinical trials with D2A21 in 1999. Demeter has received over $1 million in research grants in support of its peptide cancer research from the Pacific West Cancer Fund of Seattle. The Company has also received collaborative support from the National Cancer Institute and Duke University Medical Center, in addition to the University of Pittsburgh Cancer Institute.

Dr. Jesse M. Jaynes, Vice President of Research for Demeter BioTechnologies, said: "These results are very exciting and we are very encouraged by the compound's activity against both primary tumors and metastases, a feature we believe important to novel drug candidates for prostate cancer. In addition, the ability of D2A21 to be efficacious at sites distant from the application site, and by various routes of administration, suggests that D2A21 may have properties much more beneficial than originally thought for these types of compounds.

"The general theory for mechanism of action of the Peptidyl MIMs(tm) has been that of initial membrane disruption with subsequent cell lysis and death. However, these data suggest that additional factors come into play in the in vivo situation. We are accumulating evidence which indicates that D2A21 has anti-angiogenic properties in addition to its lytic function. The anti-angiogenic property interferes with tumor blood supply, and reduces the growth rate for the primary tumor. Analysis of the structures of our peptides and those reported to inhibit angiogenesis indicate a commonality of certain parts of these molecules. If this proves out, I am optimistic that Demeter's D2A21 could become a very beneficial prostate cancer therapy."

Prostate cancer, the second leading cause of cancer deaths in US men, affects 9.7 million Americans. Over 200,000 new cases are diagnosed each year and more than 40,000 American men die with the disease annually. A significant number of patients relapse from initial treatment, and develop metastatic disease. There is no effective therapy available for metastatic prostate cancer in patients who have failed initial therapy.

Demeter BioTechnologies, Ltd. is a research company which designs and develops novel synthetic molecules for anti-cancer and anti-infective applications. Its unique peptide molecules have structures based on principles discovered in naturally occurring peptides, but have greater potency with reduced toxicity. The Company is currently working on applications for the treatment of cancer and the prevention and treatment of sexually transmitted diseases. The Company also designs and constructs genes for development of disease resistant and nutrition improved crops. The Company has already licensed a number of non-pharmaceutical applications to Mycogen Corporation. The Company is not associated with the Demeter Association.

This press release includes forward looking statements which reflect management's current views to the Company's scientific results, collaborative arrangements, product developments, and other future events and operations. There are considerable risks and challenges to be overcome before a product is commercially viable and regulatory approval obtained. Other companies may develop competing technologies and there is no assurance that the Company's patent position is adequate. Actual results may differ materially from these forward looking statements. The Company disclaims any intent or obligation to update these forward looking statements.

For more information, contact Richard D. Ekstrom, President, Demeter BioTechnologies, Ltd. at [phone] or Michael Derrick of Progressive Media Group, Inc. at [phone].

    CONTACT:  Demeter BioTechnologies Ltd.
               Richard D. Ekstrom, President, 919/682-7181
                 or
               Progressive Media Group Inc.
               Michael Derrick, 800/262-9798