ANX Mast Therapeutics, Inc.

ADVENTRX Presents Results at 4th Annual International AIDS Society Conference SAN DIEGO, July 23 /PRNewswire-FirstCall/ -- ADVENTRX Pharmaceuticals Inc. (AMEX:ANX), a biopharmaceutical research and development company focused on commercializing proprietary product candidates for the treatment of cancer and infectious diseases, announced today that it presented results demonstrating synergistic HIV inhibitory activity of the Company's broad spectrum antiviral drug candidate, ANX-201, when combined with approved nucleoside and nucleotide reverse transcriptase inhibitors (N(t)RTI) in preclinical tests. The results were presented at the 4th Annual International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Sydney, Australia on July 23, 2007. The poster entitled "Synergistic Antiretroviral Activity of Pyrophosphate Analogue ANX-201 Paired with Nucleoside Reverse Transcriptase Inhibitors In Vitro" was presented by Shani Waninger, Ph.D., associate director for research and development for ADVENTRX. "These preclinical results suggest that ANX-201 and commonly prescribed N(t)RTIs represent a promising combination in multidrug antiretroviral therapy," said Evan M. Levine, ADVENTRX's chief executive officer. "Although ANX-201 and N(t)RTIs target the same viral enzyme, ANX-201 exerts antiviral activity by a unique mechanism and represents a novel class of reverse transcriptase inhibitor. These data suggest that ANX-201 in combination with N(t)RTIs has potential clinical advantages for HIV patients, including enhanced viral suppression and slowed progression of drug resistance. We are excited about these results and expect to initiate a clinical trial with ANX-201 as a component of multi-drug therapy for the treatment of HIV later this year." ANX-201 combined at fixed ratios with N(t)RTIs including zidovudine, tenofovir, abacavir, lamivudine, emtricitabine and stavudine resulted in synergistic to additive inhibition of HIV-1 in cultured human cells using standard in vitro assays. Furthermore, this synergistic activity suggests that the addition of ANX-201 to a drug regimen containing N(t)RTIs may have clinical advantages that include enhanced antiviral activity and the potential for reduced toxicity. A copy of the poster presentation is available for download from the "Resources" section of the Company's web site at http://www.adventrx.com/ under "Publications". About ANX-201 ANX-201 (thiophosphonoformic acid) is a pyrophosphate analog and member of a new class of reverse transcriptase inhibitor (RTI) for treatment of resistant HIV patients. ANX-201 has shown activity against HIV drug-resistant clinical isolates in preclinical studies. The resistance profile of ANX-201 is unique among approved RTIs and has been shown to resensitize NRTI-resistant virus. In preclinical studies, ANX-201 has shown broad-spectrum antiviral activity against HIV-1, HIV-2, human and avian influenza viruses, and herpes simplex viruses 1 and 2 (HSV-1 and HSV-2). ADVENTRX plans to initiate a Phase 1/2 clinical trial of ANX-201 as a component of multi-drug therapy for the treatment of HIV during 2007. About ADVENTRX Pharmaceuticals ADVENTRX Pharmaceuticals is a biopharmaceutical research and development company focused on commercializing proprietary product candidates for the treatment of cancer and infectious diseases. The Company seeks to improve the performance and safety of existing treatments by addressing significant problems such as drug metabolism, bioavailability, excessive toxicity and treatment resistance. More information can be found on the Company's web site at http://www.adventrx.com/. Forward Looking Statement ADVENTRX cautions you that statements included in this press release that are not a description of historical facts are forward-looking statements that involve risks and assumptions that, if they materialize or do not prove to be accurate, could cause ADVENTRX's results to differ materially from historical results or those expressed or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to: the validity of research results; the risk that preclinical results are not indicative of the success of subsequent clinical trials and that products will not perform as preclinical data suggests or as otherwise anticipated; unexpected adverse side effects or inadequate therapeutic efficacy of ANX-201 and other uncertainties inherent in the drug development process; the timing and success of clinical trials; difficulties or delays in developing, testing, manufacturing, and obtaining regulatory approval for ANX-201, including receiving necessary regulatory approvals for a Phase 1/2 clinical trial of ANX-201; the risk that ADVENTRX will be unable to raise sufficient capital to fund the projects necessary to meet its anticipated or stated goals and milestones, including funding the continued development of ANX-201 for the treatment of HIV or human or avian influenza; and other risks and uncertainties more fully described in ADVENTRX's press releases and public filings with the Securities and Exchange Commission. ADVENTRX's public filings with the Securities and Exchange Commission are available at http://www.sec.gov/. ADVENTRX does not intend to update any forward-looking statement, including as set forth in this press release, to reflect events or circumstances arising after the date on which it was made. DATASOURCE: ADVENTRX Pharmaceuticals Inc. CONTACT: Ioana C. Hone of ADVENTRX Pharmaceuticals, +1-858-552-0866 Web site: http://www.adventrx.com/

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