Acusphere's Hydrophobic Drug Delivery Systems (HDDS(TM)) Technology Receives Additional Validation; Partner and Patent Add to HDDS Momentum.

WATERTOWN, Mass. -- Acusphere, Inc. (NASDAQ:ACUS) today announced that it has signed a master research and development agreement with a major pharmaceutical company to reformulate one of that company's water insoluble compounds utilizing Acusphere's Hydrophobic Drug Delivery Systems (HDDS(TM)) technology. Acusphere also announced that it has been awarded an additional patent covering aspects of its HDDS technology, U.S. Patent No. 6,932,983, entitled "Porous Drug Matrices and Methods of Manufacture Thereof."

The partnership is a collaboration structured around a feasibility study to enhance the efficacy of a specific, existing hydrophobic anticancer agent. Success in this study could lead to the application of HDDS technology with this partner for other compounds. For competitive reasons, the two companies have agreed not to disclose the pharmaceutical company's name or the name of the specific drug being studied. During this feasibility study the partner is reimbursing Acusphere for its estimated costs. Upon completion of this feasibility study, both companies will assess how effectively the Acusphere HDDS technology improved the delivery of this drug and consider further options. Acusphere is currently in discussions with several pharmaceutical companies regarding potential opportunities that leverage the HDDS technology.

"The effective delivery of hydrophobic drugs remains both a significant challenge for the pharmaceutical industry and a focal point for Acusphere," commented Sherri C. Oberg, President and CEO of Acusphere. "Our HDDS technology has demonstrated it can significantly improve the dissolution rate of a variety of hydrophobic drugs. Those findings will now be used as we seek to improve the profile of an existing drug through this exciting collaboration."

Acusphere completed a human clinical study in 2004 with the Company's leading HDDS product candidate, AI-850. The primary goal of the study was to provide proof-of-concept that HDDS is capable of intravenously delivering hydrophobic drugs, in this case taxane therapy, without the need for co-solvents that are inconvenient to administer and may have undesirable side effects. This study, Acusphere believes, demonstrated significant potential benefits of the HDDS technology including no pre-medications, faster injections and cheaper and easier administration.

The new patent covers methods of delivering drugs to a patient using Acusphere's unique HDDS technology and brings to 20 the total number of patents on porous microparticle technology now held by Acusphere. Numerous routes of administration, including parenteral, mucosal, oral and topical, are described in this patent. Acusphere's HDDS approach is designed to enhance the rate of dissolution for pharmaceutically unstable formulations of drugs, particularly those having poor water solubility.

About HDDS Technology

Acusphere's HDDS technology has the potential to improve marketed formulations of hydrophobic (poorly soluble) drugs and to create novel formulations of hydrophobic therapeutics whose development may otherwise be discontinued due to the lack of an effective formulation. HDDS technology converts drugs with poor water solubility into stable, dry powder formulations. The drug compound is embedded in microparticles having a porous, water soluble, sponge-like matrix. When mixed with water, the matrix dissolves, wetting the drug and leaving a suspension of rapidly dissolving drug particles.

The versatility of HDDS technology allows for the creation of sterile microparticles that are appropriate for all routes of administration, including intravenous, subcutaneous, pulmonary, or oral administration using a scaled, high efficiency process. Acusphere's HDDS technology offers the potential to improve drug formulation by overcoming solubility issues, thereby offering patients safer and more effective drugs with greater convenience.

About Acusphere, Inc.

Acusphere (NASDAQ: ACUS) is a specialty pharmaceutical company that develops new drugs and improved formulations of existing drugs using its proprietary microparticle technology. Acusphere's three initial product candidates are designed to address large unmet clinical needs within cardiology, oncology and asthma. These product candidates were created using proprietary technology that enables Acusphere to control the porosity and size of nanoparticles and microparticles in a versatile manner that allows particles to be customized to address the delivery needs of a variety of drugs. Acusphere's lead product candidate, AI-700, is a cardiovascular drug in Phase 3 clinical development. AI-700 is designed to enable ultrasound to compete more effectively with nuclear stress testing, the leading procedure for detecting coronary heart disease. An estimated 9.5 million procedures are done each year in the U.S. to detect coronary heart disease, the leading cause of death in the United States. For more information about Acusphere visit the Company's web site at www.acusphere.com.

This Release contains forward-looking statements which are made pursuant to the safe harbor provisions of Section 21E of the Securities Exchange Act of 1934. Investors are cautioned that statements in this press release which are not strictly historical statements, including without limitation, statements regarding future results, commercial prospects or benefits from Acusphere's collaborations with other companies, future results, commercial prospects or benefits of AI-850 and the future results, commercial prospects or benefits of Acusphere's HDDS technology, constitute forward-looking statements which involve risks and uncertainties. Acusphere's actual results may differ materially from those anticipated in these forward-looking statements based upon a number of factors, including anticipated operating losses and existing capital obligations, uncertainties associated with research, development, testing and related regulatory approvals, including uncertainties regarding the ultimate outcome of Acusphere's Phase 3 clinical trials for AI-700 and uncertainties regarding the number of patients required to complete the Phase 3 clinical trials, uncertainties regarding the cost, timing and ultimate success of the build-out of Acusphere's commercial manufacturing facility, including qualifying such facility in accordance with applicable regulatory requirements, unproven markets, future capital needs and uncertainty of additional financing, competition, uncertainties associated with intellectual property, complex manufacturing, high quality requirements, lack of commercial manufacturing experience, dependence on third-party manufacturers, suppliers and collaborators, lack of sales and marketing experience, loss of key personnel, uncertainties associated with market acceptance and adequacy of reimbursement, technological change and government regulation, and other risks and challenges detailed in Acusphere's filings with the U.S. Securities and Exchange Commission, including Acusphere's Quarterly Report on Form 10-Q for the quarter ended September 30, 2005. Readers are cautioned not to place undue reliance on any forward-looking statements, which speak only as of the date of this Release. Acusphere undertakes no obligation to publicly release the results of any revisions to these forward-looking statements that may be made to reflect events or circumstances that occur after the date of this Release or to reflect the occurrence of unanticipated events.