Hemispherx requests FDA time extension for Ampligen NDA data resubmission

Hemispherx Biopharma, Inc. (NYSE Amex:HEB) (the "Company" or "Hemispherx"), announced that the Company has requested an extension of time in which to resubmit data to its NDA for Ampligen®, an experimental therapeutic, to treat CFS. This request is made in view of Hemispherx actively continuing to evaluate new information concerning the potential viral etiology of CFS, as that information may profoundly affect the design, conduct, and interpretation of clinical trial(s) (including those already conducted), as well as any supportive laboratory studies responsive to the Complete Response Letter (CRL). For this reason, the Company has requested, under 21 C.F.R. 314.110(c)(1), an extension of up to 12 months of the time for response to the queries and issues raised in the CRL.

Two independent groups have provided substantial evidence of a novel retrovirus family in the blood of patients with CFS. The first research group with its lead author from the Whittemore Peterson Institute described an infectious retrovirus (XMRV) in 67% of CSF patients (Lombardi, et al. Science.2009;326:585-589). The second consisting of a consortium of scientists at the FDA (Division of Cellular and Gene Therapies and Division of Human Tissues), NIH, and Harvard University reported that 86% of individuals suffering from CFS have gene sequences in cellular elements of the blood closely related to XMRV (Lo, et al. PNAS. 2010 107:15874-15879). Hemispherx has recently made complementary observations on the preserved blood specimens from hundreds of subjects who participated in the Company's Phase III pivotal trial in CFS (termed "AMP-516"). A significant fraction of the study population has evidence of exposure to this novel retrovirus.

Although the role of XMRV in the pathogenesis of human disease is unknown, its prevalence in CFS suggests a contributory role. Since XMRV can infect both B and T lymphocytes, it is possible that the pathogenesis of XMRV may involve significant effects on immune responses with parallels to the human retroviral pathogens, HIV and HTLVI/II, as well as MLV in murine models. Hence, it is of great public health interest to provide an in-depth analysis of our sample inventory in collaboration with epidemiological and virological experts around the country.

The Company also filed with the FDA a Prospective Study Protocol Plan (titled "Analysis of XMRV Markers from the Serum Samples for All Evaluable Subjects of the Clinical Study AMP-516"), which formalizes the Company's ongoing analysis of potential interrelationships between XMRV, CFS symptomatology and potential therapeutic intervention with poly I: poly C12U (Ampligen®).

In conjunction with this ongoing analysis of the Company's AMP-516 study, which is an integral part of NDA 22-151, Hemispherx is also initiating a widened enrollment of the open label AMP 511 study to increase the number of observations relating to potential interrelationships of XMRV, CFS symptoms and poly I: poly C12U (Ampligen®).

Hemispherx has already presented its initial observations at the 1^st International Workshop on XMRV held at NIH on September 7-8, 2010. These observations suggest a heightened therapeutic response to Ampligen® in CFS patients with a history of XMRV exposure. The Company believes continuing with this type of analysis would be helpful in responding to the CRL as well as in pursuing the mission to offer potential novel treatments to CFS sufferers.