Zonagen Publishes Data On Company's New Vaccine Adjuvants.

Business Editors & Health/Medical Writers

THE WOODLANDS, Texas--(BUSINESS WIRE)--Nov. 30, 2000

Zonagen, Inc. (Nasdaq:ZONA)(PCX:ZNG) announced that data developed by Zonagen has been published in the November 2000 issue of Vaccine indicating the potential of the Company's vaccine adjuvant systems. Adjuvants are substances that enhance the ability of antigens to elicit an immune response and are essential components of many of the modern vaccines currently under development. The publication cites results from studies of the immune responses produced following vaccination of recombinant human beta-chorionic gonadotropin formulated with the Company's patented adjuvant system. Human beta-chorionic gonadotropin is a well-established immunocontraceptive antigen and a potential target for tumor immunotherapy. Zonagen currently has three issued patents covering its adjuvant technology.

The Company's adjuvants were originally developed as a means to overcome the inability of the Company's zona pellucida vaccine to elicit an effective contraceptive response. Zonagen's antigens target self-proteins and therefore tolerance to these agents represents a difficult hurdle to overcome. Zonagen's proprietary adjuvants, however, consistently and safely produce immune responses that yield the desired biological effect. A separate study published in the September 2000 issue of Journal of Reproduction and Fertility reported results of a primate trial wherein consistent contraceptive effects were observed in animals actively immunized against their own zona pellucida protein. The zona pellucida is an extracellular matrix protein that surrounds all mammalian eggs. Zonagen's proprietary adjuvant system enabled the responses observed.

Mitzi Martinez, DVM, Ph.D., Director of Immunology at Zonagen and named inventor on one of the Company's adjuvant related patents, noted, "When we first began this work it became readily apparent that a safe and efficacious adjuvant would be required if we were to achieve success in Zonagen's vaccine development programs. The results presented in this publication demonstrate this potential."

Mark Jenkins, Ph.D., Senior Research Scientist, Animal & Natural Resources Institute, USDA, Beltsville, MD, stated, "Adjuvants represent an important component of new vaccine development. The study of Seferian and Martinez published in this month's issue of Vaccine represents an important advance in realizing this goal." Dr. Susan Liddell, a post-doctoral scientist in Dr. Jenkins' laboratory, has used one of Zonagen's adjuvants in studies that demonstrated the successful prevention of vertical transfer of Neospora caninum in BALB/c mice by vaccination. The results of these studies were recently published in the Journal of Parasitology. Neosporosis is an important cause of abortion and neonatal morbidity in dairy cattle worldwide and a vaccine is sorely needed to prevent spread of this disease.

"We are pleased with the progress made by our scientific team at Zonagen," said Joseph Podolski, President and CEO of the Company. He added, "We believe our adjuvant systems can play a useful role in a variety of vaccine programs and we are actively seeking to outlicense them on a product by product basis."

Zonagen, Inc. is engaged in the development of pharmaceutical products for the reproductive system, including sexual dysfunction, vaccine adjuvants, products for fertility and female health as well as urological applications, specifically prostate cancer.

Any statements that are not historical facts contained in this release are forward-looking statements that involve risks and uncertainties, including but not limited to those relating to the uncertainties involving the Company's early stage of development, clinical trial results and FDA approval in the U.S. and approval of regulatory authorities in other jurisdictions, substantial dependence on one product, history of operating losses, future capital needs and uncertainty of additional funding, uncertainty of protection for patents and proprietary technology, litigation, governmental regulation, limited sales and marketing experience and dependence on collaborators, manufacturing uncertainties and reliance on third parties, competition and technology change, product liability and availability of insurance, and other risks identified in the Company's Annual Report on Form 10-K for the year ended December 31, 1999, as filed with the Securities and Exchange Commission.