Acusphere, Inc. Commences Pivotal Phase of AI-700 Phase 3 Clinical Program.

Business Editors/Health/Medical Writers

WATERTOWN, Mass.--(BUSINESS WIRE)--Dec. 18, 2003

Acusphere, Inc. (NASDAQ: ACUS), today reported that it has commenced the pivotal phase of its Phase 3 clinical program for AI-700, an ultrasound contrast agent designed for detecting coronary artery disease. The pivotal trials consist of two concurrent international trials, both of which have now been initiated. The start of the pivotal Phase 3 trials is on schedule with the Company's plan and follows the successful completion, at selected sites, of the pilot phase of the clinical program.

Acusphere also reported that it has initiated over half the projected number of clinical sites in the pilot phase of the AI-700 Phase 3 program. The Company's current clinical efforts are focused on training new sites in the US and Europe in the pilot study. When training is complete at a pilot site, that site can move on to the pivotal phase. Over the next several months, the Company will be initiating sites in both the pilot study and the pivotal studies. During the first half of 2004, the Company anticipates initiating all of the pivotal sites necessary to meet its enrollment plan for the Phase 3 program.

"We are very pleased to be initiating our Phase 3 pivotal trials for our lead product candidate, AI-700, on schedule," said Sherri C. Oberg, President and CEO of Acusphere. "We are now working diligently to ensure that the pilot sites are enrolling so that we can quickly move these sites through the pilot phase and into the pivotal phase."

"AI-700 perfusion echocardiography has the potential to be a cost-effective and convenient alternative to nuclear perfusion imaging," said Michael H. Picard, M.D., F.A.C.C., Director of Clinical Echocardiography at Massachusetts General Hospital and medical advisor to Acusphere. "AI-700 is easy to use and echocardiographers in the clinical trials can be trained to use it after imaging only a few patients. Based on data from previous clinical trials, ultrasound enhanced with AI-700 was able to image myocardial perfusion and obtain information that appears comparable to nuclear imaging. Acusphere's Phase 3 program is designed with the appropriate comparative standards to determine the value of AI-700 perfusion echocardiography relative to nuclear perfusion imaging. These standards are coronary angiography, nuclear perfusion imaging, and patient outcome."

Ultrasound is the only frequently used imaging technique without a commercially significant imaging agent. Acusphere has designed AI-700 to work with ultrasound for assessment of myocardial perfusion (blood flow in the heart muscle), a sensitive marker of coronary artery disease. In 2002, an estimated 9.5 million procedures were performed in the U.S. to screen patients with suspected coronary artery disease, primarily using nuclear imaging. AI-700 is being developed as a cost-effective and convenient alternative to nuclear imaging.

About Acusphere, Inc.

Acusphere is a specialty pharmaceutical company that develops new drugs and improved formulations of existing drugs using its proprietary microparticle technology. Drugs being developed by Acusphere are intended to offer significant benefits such as improved safety and efficacy, increased patient compliance, greater ease of use, expanded indications or reduced cost. Acusphere's three initial product candidates are in clinical development and 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 size and porosity of microparticles in a versatile manner that allows microparticles to be customized to address the delivery needs of a variety of drugs. They each were created using porous microparticles that are smaller than red blood cells. Acusphere's lead product candidate, AI-700, is a cardiovascular drug in Phase 3 clinical development for the detection of coronary artery 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, including statements regarding the timing of clinical site training and patient enrollment in the AI-700 Phase III clinical program and the potential utility of and commercial prospects for AI-700. 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, unproven markets, future capital needs and uncertainty of additional financing, competition, uncertainties associated with intellectual property, complex manufacturing, high quality requirements for clinical trial materials, dependence on third-party manufacturers, suppliers and collaborators, loss of key personnel, uncertainties associated with market acceptance and adequacy of reimbursement, technological change, government regulation, and other risks and challenges detailed in the Company's filings with the U.S. Securities and Exchange Commission, including its most recent Quarterly Report on Form 10-Q. 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.