Zonagen's ERxin Data for the Treatment of Severe Erectile Dysfunction Presented At International Congress of Andrology in Montreal.

Health/Medical Writers

THE WOODLANDS, Texas--(BW HealthWire)--June 20, 2001

Zonagen, Inc. (Nasdaq:ZONA)(PCX:ZNG) announced today that the results from a Phase II study of the Company's combination penile injection product ERxin(TM) is being presented at the 3rd International Congress of Andrology in Montreal, Canada. Dr. Rosaria Tapia of Mexico City, principal investigator in the study, will present the data.

The study was designed to compare the efficacy and safety of four different combination intracavernosal injection therapies in patients who failed to respond to an injection of Caverject(R). A total of 40 patients with severe erectile dysfunction were enrolled at three sites in Mexico.

The study recruited men who were unsuccessful achieving an erection after an in-office injection of 1.0 ml Caverject(R) containing 20 micrograms of alprostadil. Patients that failed to respond to this maximum approved dose of Caverject(R) returned to the office for four subsequent visits spaced by at least one week. During those subsequent visits patients received one half of the maximum dose of one of four formulations.

The ERxin(TM) formulations tested included two concentrations of a bimix of phentolamine and prostaglandin and two formulations of a trimix containing phentolamine, papavarine and prostaglandin. All the formulations included Zonagen's proprietary buffer system, which has been shown to increase the response to vasoactive agents in the relaxation of penile smooth muscle. The buffer itself does not produce erections (data from earlier studies).

Erections sufficient for vaginal penetration in patients were achieved in 43% of the test subjects for the lowest dose bimix as compared to 51% for the highest dose trimix. Although there were numerical differences in response rates between the four formulations, there were no statistical differences. The great majority of adverse events were mild in severity for all treatments. The incidence of penile pain showed a clear alprostadil dose-response relationship. In an earlier study in men who failed Viagra(R) therapy, 82% of patients were able to achieve an erection deemed suitable for intercourse after receiving an injection of ERxin(TM).

Dr. Tapia noted, "Patients with severe erectile dysfunction who do not respond to 20 micrograms Caverject(R) can be helped with intracavernosal injections of a bimix or trimix formulation. Addition of papavarine to the ERxin(TM) formulation does not add significantly in terms of achieving an adequate erectile response."

Joseph S. Podolski, President and CEO of Zonagen, said, "We are pleased with the results of the ERxin(TM) study. Our data supports the potential of a cost-effective two-component combination therapy for the treatment of severe erectile dysfunction. From Vasomax(R) for the treatment of mild to moderate impotency and the second generation oral therapy Bimexes(TM), to ERxin(TM) for the treatment of severe cases, Zonagen is investigating potential products to effectively treat nearly the entire range of erectile dysfunction." He then added, "Before the product can be approved, a complete battery of clinical studies must be performed and submitted to the FDA. We must also bear in mind that the product contains phentolamine, the active ingredient in Vasomax(R). Vasomax(R) is currently on partial clinical hold in the U.S. due to brown fat findings in a preclinical rat study. We hope to resolve the FDA's concerns regarding the brown fat findings during the next 12 months."

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 such as the potential uses of ERxin(TM) and Bimexes(TM) in humans and potential approval of phentolamine for use in the United States, 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 propriety 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, 2000, as filed with the Securities and Exchange Commission.