Hemispherx Announces Poly I:Poly C12U Increases the Control of HIV During Strategic Treatment Interruption in Chronically HIV Infected Patients.

Business Editors/Medical Writers

PRAGUE, Czech Republic--(BUSINESS WIRE)--March 18, 2002

Ampligen(R) Increases the Length of Time Before

Viral "Rebound" Occurs

At the 15th International Conference on Antiviral Research held today in Prague, representatives of Hemispherx Biopharma (AMEX:HEB) and Vanderbilt University, Nashville, TN, presented new clinical data on Ampligen(R), an experimental immunotherapeutic designed to maintain strong control over HIV multiplication in conjunction with "HAART".

"HAART" is the acronym for a powerful antiviral "cocktail" of multiple approved drugs used worldwide in the management of chronic HIV infection. HAART often drops the level of the AIDS virus in the blood to low or undetectable levels; however, the therapeutic benefits may be transitory and are often associated with potentially fatal drug toxicities.

Therapeutic (HAART) Holidays

To combat these serious medical issues, physicians worldwide have recently introduced the new concept of "drug holiday", also called strategic treatment interruption (STI)-a discontinuation of all parts of the complete HAART regimen. However, approximately 86% of chronically HIV infected patients will relapse quickly, usually within 3 weeks of commencing a holiday or "STI". In eight newly (or acutely) infected patients, researchers at Harvard University ("the Harvard cohort"), recently suggested that clinical/virological responses are much more durable if the immune system is less damaged and/or capable of being reactivated (Nature volume 407,p.523, 2000).

Hemispherx's RNA drug technology, a group of experimental-level immunotherapeutics including Ampligen(R), is inserted into the "drug holiday" time space under clinical protocols recently authorized by regulatory agencies in an effort to improve clinical/virological responses in chronic HIV infections.

The presentation was made by Professor William Mitchell, M.D., Ph.D., an internationally recognized researcher in AIDS who holds a professorship in Pathology at Vanderbilt University School of Medicine, Nashville, TN. He is also a member of the Board of Directors of Hemispherx. Dr. Mitchell received his M.D. degree from Vanderbilt University and his Ph.D. from Johns Hopkins University, Baltimore, Md. The clinical study is titled "A role of Ampligen(R)in STI: A multicenter, randomized, controlled study of Ampligen(R)potentiation of the HAART-free interval (AMP 720)" and was conducted in collaboration with Blick Medical Associates, Connecticut.

The primary Phase IIb clinical study endpoint is the mean (average) total time of the HAART-free intervals before rebound of plasma HIV-1 RNA (using the Roche Ultra Sensitive assay). The AMP 720 HIV infected population ("the study group") was designed to be similar to the referenced 8 patient Harvard Cohort in the following ways: a) HAART therapy was given for 9 months or more; b) immune cell level was generally satisfactory (CD4 level, equal/greater 400 per milliliter); and c) HIV RNA was less than 50 copies per milliliter of blood. Levels of HIV RNA less than 50 evidence strong control of the HIV/AIDS virus in that particular patient.

The notable difference in the two study groups was that the "Harvard cohort" were studied within weeks (or a few months) of initial infection, whereas the AMP- 720 "study group" had been infected with HIV/AIDS virus for several years. To date, 14 patients were randomized to receive either Ampligen or no Ampligen once their STI period was commenced. Six active clinical sites are enrolling patients in the Eastern United States, including principally in Stamford, CT and in California.

Clinical Study Outcomes

Two types of interim data analysis were performed, one with a control (non-Ampligen treated) group obtained from the scientific literature ("meta analysis") and a second with a concurrent control (non-Ampligen treated) group obtained from the identical participating medical institutions. In a "randomized" study such as the referenced clinical protocol, patients are randomly selected to either receive, or not receive, the study medication.

In the "meta analysis", no patients relapsed while on Ampligen within the first 30 days as compared to 86% of a control group of 21 patients, resulting in a statistically significant difference (p = 0.012).

In the second analysis utilizing a concurrent control group, there were also differences between the relative relapse rates. The median duration of the STI in the Ampligen group was greater than 18 weeks whereas a median duration of 7 weeks was observed in the concurrent control, non-Ampligen, group.

Safety Profile

With respect to the side effect/adverse event profile, the only serious adverse events were noted in the non-Ampligen treated control group and included the emergence of acute Hepatitis A infection. With respect to various safety parameters measuring liver, bone marrow and kidney function, no significant differences were noted between the study groups indicating that the addition of Ampligen did not trigger any measurable toxicity in these bodily organs, even in the presence of a history of long-term HAART administration, during the observation period.

Company Background

Hemispherx Biopharma, Inc., Philadelphia, PA, has devoted nearly three decades of exploring, understanding, and mastering the mechanism of ribonucleic acid (RNA) drug technology. The Company's longevity as a biomedical research and drug development institution, coupled with its record of enduring scientific achievement, is evidence of long-term commitment to these promising new classes of drugs for the chronically ill and to bring new therapeutic choices to the original global health care community. For more information, please visit the Company's website at http://www.hemispherx.net.

Information contained in this news release other than historical information, including the referenced HIV drug testing, should all be considered forward-looking and are subject to various risk factors and uncertainties. For instance, the strategies and operations of Hemispherx involve risks of competition, changing market conditions, changes in laws and regulations affecting these industries and numerous other factors discussed in this release and in the Company's filings with the Securities and Exchange Commission. Accordingly, actual results may differ materially from those in any forward looking statements. Additionally, all the referenced investigational drugs and associated technologies of the company are experimental in nature and as such are not designated safe and effective by a regulatory authority for general use and are legally available only through clinical trials with the referenced disorders. The forward-looking statements represent the Company's judgement as of the date of this release. The Company disclaims, however, any intent or obligation to update these forward-looking statements.