CAMBRIDGE, Mass.
June 8, 2007

Archemix Corp., a biotechnology company focused on discovering and developing aptamers, announced the successful completion of a Phase 1 study of its novel aptamer therapeutic, ARC1779. ARC1779 is designed to selectively block the activation, adhesion and aggregation of platelets by inhibiting the binding of von Willebrand Factor (vWF) to the GPIb receptor on platelets. Activated vWF is scientifically recognized as the first stage of arterial thrombus formation and plays a significant role in the development of harmful blood clots. Archemix plans to develop ARC1779 as an anti-thrombotic drug for use in angioplasty and in a rare blood disorder that is mediated by vWF known as thrombotic thrombocytopenic purpura, or TTP.

Archemix plans to present a complete data set from this Phase 1 clinical trial within a peer-reviewed forum in 2007.

Based on the proof-of-mechanism data from this Phase 1 study, Archemix plans to commence a Phase 2 study of ARC1779 to evaluate the safety and efficacy of ARC1779 in acute coronary syndrome patients during the fourth quarter of 2007. Additionally, Archemix plans to initiate a Phase 1b study of ARC1779 in patients suffering from TTP in the fourth quarter of 2007. Approximately 3,000 new cases of TTP are diagnosed per year in the United States, but currently there is no approved drug therapy for the disease.

"We are very pleased to demonstrate ARC1779 can inhibit vWF activation and platelet function, which are both widely recognized as playing critical roles in clot formation which can critically impede blood flow to the heart," said Jim Gilbert, M.D., Chief Medical Officer, Archemix. "In Phase 2, we hope to show that using ARC1779 during angioplasty may improve myocardial perfusion by reducing blood clots in the coronary microcirculation while also providing effective anti-thrombotic treatment at the primary site of arterial blockage."

"We are developing a pipeline of aptamer therapeutics with a proprietary focus in acute cardiovascular and hematological diseases," commented Errol De Souza, Ph.D., President and Chief Executive Officer, Archemix. "The advancement of ARC1779 into Phase 2 will be a key milestone in the development of our broad product portfolio."

About Aptamers
Aptamers are single-stranded nucleic acids that form well-defined three dimensional shapes, allowing them to bind target molecules in a manner that is conceptually similar to antibodies. Aptamers combine the optimal characteristics of small molecules and antibodies, including high specificity and affinity, chemical stability, low immunogenicity and the ability to target protein-protein interactions. In contrast to monoclonal antibodies, aptamers are chemically synthesized rather than biologically expressed.

About Archemix
Archemix Corp. is a privately-held biopharmaceutical company developing aptamers as a class of directed therapeutics for the prevention and treatment of human disease. The company is leveraging its proprietary drug discovery technology to fuel the growth of its development portfolio, which is primarily focused on acute cardiovascular and hematology diseases and cancer. Archemix's broad product pipeline, being developed both by the company as well as its licensees, includes multiple investigational compounds at various stages of development several of which are moving into advanced clinical trials. Archemix's lead proprietary product, ARC1779, a selective platelet inhibitor, is anticipated to start Phase IIa clinical trials before the end of 2007. Archemix' leadership position in intellectual property, technology and expertise relating to aptamers has enabled it to form numerous collaborations with biotechnology and pharmaceutical collaborators, including Merck Serono, Pfizer Inc., Elan Pharma, Nuvelo, Inc., Antisoma plc., and Regado Biosciences. For more information, please visit www.archemix.com.