Enzo Biochem Announces Results of Phase I Treatment for HBV Infection; Positive Report On Enzo's Proprietary Medicine EHT899 Presented At Meeting of Liver Experts.

Business/Medical Editors

DALLAS, Texas--(BUSINESS WIRE)--Oct. 31, 2000

Enzo Biochem, Inc., (NYSE: ENZ), reported today that 80% of the patients in a Phase I clinical trial of EHT899, the Company's medicine for treatment of hepatitis B virus, responded favorably as measured by a decrease in viral load, decrease in liver inflammation or reduction of elevated levels of liver enzymes.

"This is a highly encouraging report," said Dean L. Engelhardt, Ph.D., Executive Vice President of Enzo. "The percent of patients responding to this therapy is significantly greater than that achieved by other available treatments, and if our results hold up in expanded studies, now underway, then EHT899 would appear destined to become the treatment of choice for individuals with liver inflammation due to chronic infection with HBV."

Enzo previously reported commencement of a Phase II study of EHT899.

The report on the Phase I trial was presented at a meeting of the American Association for the Study of Liver Diseases by Yaron Ilan, M.D., the principal investigator in the trial. The trial was conducted at the Liver Unit of Hadassah University Medical Center in Jerusalem, Israel. The 15 trial subjects received an oral dose of EHT899 for a 20-week period, followed by an additional 20 week monitoring period to determine the safety and efficacy of this treatment.

The treatment was well tolerated in all 15 patients. Twelve patients responded favorably to the immune regulation treatment as measured by at least one of the following criteria--a decrease in viral load, a normalization of increased levels of liver enzymes or a decrease in inflammation seen on liver biopsy. Nine of the patients experienced significant decreases in viral load. Ten of the 15 patients showed complete normalization of liver enzymes.

All the patients showed a favorable augmentation in anti-HBV specific T-cell response, a marker of immunological regulation that is significant in that it demonstrates an induction or an enhancement of the immune response to HBV. The report observed that the regulation of the anti-HBV immune response by oral administration of EHT899 "alleviated significantly the immune-mediated liver injury, while augmenting the effective anti-viral immunity."

According to the latest figures published by the World Health Organization, some 2 billion people today are infected with hepatitis B, of whom an estimated 350 million are chronically infected and therefore at risk of death from liver disease. HBV accounts for 10% of chronic liver disease in the U.S. and for a major proportion of liver transplantations.

Earlier this year, as previously reported, Enzo received a matching grant totaling up to $1.4 million from the Israel-U.S. Binational Industrial Research and Development Foundation (BIRD) for expansion of Enzo's clinical trial of EHT899.

Other studies reported:

In other studies presented at the Conference here, Dr. Jennifer Brown, an Enzo scientific collaborator, reported favorable results using Enzo's proprietary immune regulation technology in animal studies to treat tupaia, a small prosimian primate, infected with human HBV. HBV infection results in a wide range of clinical manifestations ranging from benign carrier state to severe liver disease, which in the case of the tupaia was abrogated by oral administration of specific HBV proteins. These studies, in part, led to the development of EHT899, Enzo's therapy for liver inflammation caused by HBV infection. The preclinical animal studies were carried out at the Albert Einstein College of Medicine in New York City in collaboration with Enzo scientists.

In another paper, Dr. Brown reported that she had succeeded in transplanting primary human hepatocytes (liver cells) into mouse liver. These cells were shown to engraft within the mouse liver and to survive and function for a period of many months. In previous studies, Dr. Brown had reported the engraftment of cells from an HBV-associated liver cancer. After transplantation, these human cells, containing the HBV virus DNA, were shown to be capable of producing viral particles. "Both of these animal studies have the potential to lead to the development of a broad animal model system capable of supporting the growth of human hepatitis B virus and will enable us to examine a variety of therapeutic approaches for treating hepatitis," noted Dr. Engelhardt. This animal model system is the subject of a pending patent application by Enzo Biochem.

Enzo Biochem is engaged in the research, development and manufacture of innovative health care products based on molecular biology and genetic engineering techniques, and in providing diagnostic services to the medical community.

A conference call conducted by Enzo Biochem, Inc. management will take place on Tuesday October 31,2000 at 9 A.M. (ET) It can be accessed by dialing [phone] or over the Internet through Investor Broadcast Networks' Vcall website, located at www.vcall.com. To listen to the live call on the Internet, please go to the web site at least fifteen minutes early to register, download and install any necessary audio software. For those who cannot listen to the live broadcast, a replay will be available shortly after the call on the Internet.

Except for historical information, the matters discussed in this news release may be considered "forward-looking" statements within the meaning of Section 27A of the Securities Act of 1933, as amended and Section 21E of the Securities Exchange Act of 1934, as amended Such statements include declarations regarding the intent, belief or current expectations of the Company and its management. Prospective investors are cautioned that any such forward-looking statements are not guarantees of future performance and involve a number of risks and uncertainties that could materially affect actual results.