Company Achieves Key Clinical Milestone with Initiation of Second Phase 2 Trial for ARC1779

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Mar 30, 2009 - Archemix Corp., a privately-held biotechnology company working to develop aptamer-based therapeutics, announced today that it has initiated a Phase 2a clinical trial of its novel anti-von Willebrand Factor (VWF) aptamer, ARC1779. The trial is designed to evaluate the safety and efficacy of ARC1779 as a potential first-in-class anti-platelet agent in patients with carotid artery disease undergoing a surgical procedure known as carotid endarterectomy, or CEA.

The recently initiated Phase 2a trial is a randomized, double-blind, placebo-controlled study to evaluate the efficacy, safety and tolerability of ARC1779 in approximately 100 CEA patients at multiple centers in North America and Europe. The primary objectives of the trial will be to measure the effectiveness of ARC1779 in reducing the number of small blood clots which form immediately following the operation and then flow to the brain, and to assess the bleeding risk of ARC1779 in this setting. Secondary objectives include evaluating the effect of ARC1779 administration on reducing the brain injury caused by the small blood clots formed immediately following the operation. The study will also assess the pharmacokinetic and pharmacodynamic profile of ARC1779.

“Current anti-platelet agents such as aspirin, even when used in combination with one another, fail to adequately protect patients from recurrent strokes. There is an unmet medical need for anti-platelet agents that can improve the success rate for stroke prevention,” commented Dr. Hugh Markus Professor of Neurology and Clinical Neuroscience at St. George's, University of London, the lead investigator in the Phase 2a trial. “Because of the unique biology of VWF, we believe that ARC1779 can locally inhibit clot formation and reduce stroke risk, while reducing the bleeding complications that are associated with existing anti-platelet agents.”

About CEA

Carotid endarterectomy is a surgical procedure which removes an unwanted build-up of inflammatory cells, cholesterol and cellular debris known as plaque from the inner lining of the major arteries in the neck which supply blood to the brain. These vessels, known as the carotid arteries, can become narrowed by plaque, causing a reduction in blood flow to the brain. Blood clots can form on the surface of the plaque. Plaque or clots can then break loose and travel to the brain, blocking the blood flow to the brain and potentially causing permanent brain damage, stroke or death, if a large enough area of the brain is affected. If a clot or plaque blocks only a tiny artery in the brain, it may cause a transient ischemic attack, or TIA, also known as a ministroke. For patients experiencing a minor stroke or a TIA, a surgeon may recommend the surgical procedure known as carotid endarterectomy to remove plaque in the carotid arteries and help prevent a stroke. According to the Agency for Healthcare Research and Quality, more than 114,000 carotid endarterectomy procedures were performed in the United States in 2006.

About ARC1779

Archemix's lead aptamer product candidate, ARC1779, is a PEGylated aptamer consisting of 40 nucleotides. ARC1779 is designed to inhibit the function of a protein called von Willebrand Factor, or VWF, which, when activated, is responsible for the adhesion, activation and aggregation of platelets by a mechanism distinct from those targeted by marketed anti-platelet therapies such as aspirin, clopidogrel and Gp IIb/IIIa inhibitors. In addition to the Phase 2a clinical trial in patients with CEA, Archemix is also conducting a Phase 2b clinical trial with ARC1779 in patients suffering from a group of rare, life-threatening blood disorders known as thrombotic microangiopathies, or TMA, a condition for which there is currently no specifically approved drug treatment. ARC1779 has received orphan designation for the treatment of TTP in both the United States and the European Union.

About Aptamers

Aptamers are synthetically-derived oligonucleotides, or short nucleic acid sequences, that bind to protein targets with high affinity and specificity and can be designed to have a specified duration of action. Aptamers represent an emerging class of potential therapeutic agents that Archemix believes may have broad application to treat a variety of human diseases.

About Archemix

Archemix is a biotechnology company focused on discovering, developing and commercializing aptamer therapeutics. Using Archemix's processes for discovering aptamers, which are protected by its broad patent portfolio, Archemix is developing aptamer product candidates for rare hematological diseases. In addition, Archemix has licensed its intellectual property to third parties to develop their own aptamer product candidates in other areas. Currently, Archemix's licensees are evaluating five different aptamer product candidates in human clinical trials; two in Phase 2 and three in Phase 1. Archemix has additional partnerships with several pharmaceutical and biotechnology companies, including GlaxoSmithKline, Merck Serono, Pfizer, Takeda, Eli Lilly and Isis Pharmaceuticals.