Enzo Biochem, in Report to Gene Therapy Society Annual Meeting, Announces Continued Expression of Anti-HIV Antisense RNA in Clinical Trial.

Business & Health Editors

SEATTLE--(BW HealthWire)--June 4, 2001

Favorable Data Now Reaching 21 Months

Enzo Biochem, Inc. (NYSE:ENZ), in a presentation at the annual meeting of the American Society of Gene Therapy here, reported the continued expression of anti-HIV antisense RNA in T4 cells in the follow-up phase of the Company's clinical trial. The data showed that these cells continued to express the antisense RNA for as long as 21 months to date.

The results demonstrated long-term survival and functioning of antisense RNA in white blood cells and in CD4+ cells (T4 cells), and is highly encouraging, the Company said.

"We are pleased that our gene delivery agent, the BioStealthTM vector, and our gene transfer procedure have led to such long-term success in our gene therapy program," said Dean L. Engelhardt, Ph.D., Enzo's Executive Vice President.

In his report to the meeting, Dr.Engelhardt discussed the impact of Enzo's technical innovations in moving it's HIV product, HGTV43, towards the treatment of infected individuals. First, using a novel protein (HTLV2 envelope) on the outside of the transduction vector, Enzo scientists found that they were able to achieve both efficient and rapid transfer of the anti-HIV antisense genes into the blood stem cells. Furthermore, after removing all extraneous genes from the BioStealth(TM) vector, Enzo scientists found that the transduced cells containing the anti-HIV antisense RNA continued to persist. Finally, recognizing that often transgenes or chimeric genes are turned off within the body, Enzo embedded its antisense genes into a gene that is continually "turned on" and functioning ("housekeeping" gene). With the use of this "housekeeping" gene, long-term functioning of the anti-HIV antisense genes in the clinical trial subjects was achieved.

Dr. Engelhardt commented, "This achievement resulted from our harnessing of the natural mechanisms of cellular activity rather than imposing new or different processes. These data encourage us to pursue Enzo's goal of transducing cells that will be engineered for life."

Based on these results, the Company is proceeding to initiate a Phase 2 trial as well as expanding the current Phase 1 trial.

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. The Company's proprietary labeling and detection products for gene sequencing and genetic analysis with approximately 200 patents worldwide are sold to the life science market throughout the world. The Company's therapeutic division is conducting clinical trials for HIV-1-infected patients and for patients infected with hepatitis B and hepatitis C viruses, and suffering from hepatitis C- associated hepatocellular carcinoma (liver cancer). Other therapeutic applications of Enzo's proprietary technology are directed towards cholesterol management and the treatment of inflammatory bowel disease, including Crohn's disease and ulcerative colitis. The Company also holds a patent covering a method and materials for correcting point mutations or small insertions or deletions of genetic material that would allow for editing and correcting certain abnormalities in genes.

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. The Company disclaims any obligations to update any forward-looking statement as a result of developments occurring after the date of this press release.