Enzo Biochem Reports Long Term Retention of Antisense RNA in Phase I Study of HIV-1 Infected Subjects; Updated Report to International AIDS Conference Calls Results ``Significant''.

TORONTO -- Reporting here at the 16th International AIDS Conference, Enzo Biochem, Inc. (NYSE:ENZ) described the results of long term follow-up studies of its StealthVector(R) HGTV43(TM) gene medicine as "significant" and "perhaps unique." HIV-1 infected subjects treated with the proprietary retrovirus-based vector showed long term presence of the engineered CD34+ stem cells as well as a long term presence of engineered CD4+ immune cells in circulation. The Phase I clinical trial took place at the University of California San Francisco.

There were no treatment-related adverse events during the study, nor any evidence of leukemia seen by standard hematology, the report said.

Antisense RNA was present in all five subjects available at twelve months post treatment. At the 48th month four subjects were available and antisense RNA was present in three of the four. "At month 60, antisense RNA was present in one of the three previously positive subjects," the report stated. "In addition, anti-HIV-1 antisense RNA was found in CD34+ bone marrow cells in all subjects tested."

"These results are a significant, perhaps unique, example of the survival of engineered CD34+ stem cells in nonablated adult human subjects. That these engineered cells have produced progeny CD4+ immune cells is evidenced by the presence of antisense RNA in these cells in circulation," the researchers declared.

Enzo Biochem is currently sponsoring a Phase I/II study at the University of California San Francisco to continue the clinical evaluation of the Company's StealthVector(R) HGTV43(TM) gene construct for HIV-1 infection. The vector will be used to transfer three antisense genes into blood stem cells. These genes are designed to interfere with the growth of the HIV-1 virus. The protocol has been modified to increase the proportion of engineered stem cells that engraft in the patient's bone marrow, thus increasing the progeny CD4+ cells in circulation.

The engineered CD34+ stem cells containing the antisense genes are expected to replicate and differentiate within the body of the HIV-1 infected individual to produce CD4+ T-cells, the main target of infection by HIV-1. The novel aspect of the continuing study is to increase the percentage of CD4+ cells that contain the anti-HIV-1 antisense genes with a protocol designed to partially reduce the patient's blood stem cells before infusion of the engineered cells. The trial is intended to determine whether this procedure will create a supply of HIV-1 resistant CD4+ cells large enough to materially defer the disease progression of these HIV-1 infected individuals.

The regulatory approval process leading up to the Phase I/II study included a comprehensive review of the clinical protocol and safety features of the vector conducted by the Committee on Human Research at the University of California San Francisco, U.S. Food and Drug Administration and the Recombinant DNA Advisory Committee of the National Institutes of Health. In addition, all manufacturing protocols were optimized and subject management and extensive cell preparation protocols were established.

Today's updated Phase I study report further demonstrates the safety of the procedure and shows that the engineered stem cells were able to survive long term in vivo and to produce CD4+ cell progeny containing functioning antisense genes. Although there was no increase in the CD4+ cell count or reduction in the viral load, the level of engineered cells has remained approximately constant over a number of years, supporting the conclusion that stable engraftment of anti-HIV-1 antisense RNA-producing blood stem cells occurred and the antisense genes continued to function.

About Enzo

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 are sold to the life sciences market throughout the world. The Company's therapeutic division is in various stages of clinical evaluation of its proprietary gene medicine for HIV-1 infection and its proprietary immune regulation medicines for hepatitis, uveitis, Crohn's disease, and for NASH and its associated metabolic syndrome. Pre-clinical research is being conducted on several candidate compounds aimed at producing new mineral and organic bone, including technology that could provide therapy for osteoporosis and fractures, among other applications. 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. The Company owns or licenses over 200 patents worldwide. For more information visit our website www.enzo.com.

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. 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.