Acusphere Announces Publication in ''Pharmaceutical Research'' on Hydrophobic Drug Delivery System.

WATERTOWN, Mass. -- Acusphere, Inc. (NASDAQ: ACUS), a specialty pharmaceutical company, today announced that a research paper on one of the company's key proprietary technologies, Hydrophobic Drug Delivery Systems (HDDS(TM)), has been published in "Pharmaceutical Research", Volume 22, Number 3, March 2005. The paper is entitled "Intravenous Hydrophobic Drug Delivery: A Porous Particle Formulation of Paclitaxel (AI-850)" Intravenous formulation development of hydrophobic drugs, which are drugs that do not dissolve well in water, is a particularly challenging area of drug delivery.

The intravenous applications of Acusphere's HDDS discussed in this publication demonstrate that: 1) HDDS can produce high concentrations of drug in a small volume formulation, 2) HDDS enables the drug to dissolve rapidly, and 3) in animals, the HDDS-formulated drug moves more quickly from the blood to the tissue without any change in the tissue concentration or elimination half-life when compared to the commercially-available intravenous formulation of the same drug. Small injection volume, high concentration formulations are potentially important in large patient populations, such as heart failure and renal failure patients, as well as pediatric and especially neonatal patients, who cannot tolerate high volumes of fluids. Small volume, high concentration formulations may also be important for the quick and efficient delivery of high dose drugs. In addition, many drugs have certain toxicities related to circulating blood levels. An intravenous HDDS formulation which moves quickly out of the blood and into the tissue may improve the safety profile of these drugs. This paper focuses on intravenous formulations of HDDS, which has also been developed for other routes of administration including oral.

""Pharmaceutical Research" is one of the most respected pharmaceutical journals and we are very pleased to have our HDDS technology recognized by such a prestigious scientific journal," commented Sherri C. Oberg, President and C.E.O. "We are interested in collaborating with pharmaceutical companies that need intravenous formulations of their hydrophobic drugs because we believe HDDS has unique capabilities that are important for parenteral applications. In particular, HDDS can create low volume, high concentration formulations that are critical for certain patient populations and important for the efficient delivery of high dose drugs. In addition, we believe HDDS has the potential to improve the safety profile of certain intravenously-delivered hydrophobic drugs."

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 for which it has clinical data are designed to address unmet clinical needs within cardiology, oncology and asthma. 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 10.7 million procedures are performed each year in the U.S. to detect coronary heart disease, the leading cause of death in the United States. Acusphere's product candidates have been created using proprietary technology that enables Acusphere to control the porosity and size of nanoparticles and microparticles in a versatile manner that enables particles to be customized to address the delivery needs of a variety of drugs. For more information about Acusphere visit the Company's web site at www.acusphere.com.

Forward-looking Statements

This Release contains forward-looking statements, including statements regarding clinical advantages of AI-850 and HDDS and potential partnering opportunities. The Company's actual results may differ materially from those anticipated in these forward-looking statements based upon a number of factors, including anticipated operating losses, 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, unproven markets, future capital needs and uncertainty of additional financing, competition, uncertainties associated with intellectual property, complex manufacturing, high quality requirements, dependence on third-party manufacturers, suppliers and collaborators, loss of key personnel, lack of sales and marketing experience, uncertainties associated with market acceptance and adequacy of reimbursement, technological change and government regulation, and other risks and challenges detailed in the Company's filings with the U.S. Securities and Exchange Commission, including the Company's Annual Report on Form 10-K for the year ended December 31, 2004. Readers are cautioned not to place undue reliance on any forward-looking statements, which speak only as of the date of this Release. The Company 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.