Acusphere Completes Phase 1 Study of AI-850, A Porous Nanoparticle Formulation of Paclitaxel.

Business Editors/Health/Medical Writers

WATERTOWN, Mass.--(BUSINESS WIRE)--June 7, 2004

Acusphere, Inc. (NASDAQ: ACUS), a specialty pharmaceutical company that develops drug products using its porous microparticle technology, announced today that it has completed a Phase 1 human safety study of its AI-850 product. AI-850 is a Cremophor(R)-free formulation of paclitaxel, the active ingredient in Taxol(R), a product used to treat a variety of solid tumors. Results from this trial will be presented today at the American Society of Clinical Oncology ("ASCO") Annual Meeting in New Orleans.

The primary goal of the AI-850 clinical program was to provide a human proof-of-concept that Acusphere's Hydrophobic Drug Delivery System ("HDDS(TM)") is capable of intravenously delivering hydrophobic drugs without the need for co-solvents that are inconvenient to administer and are associated with undesirable side effects. The primary objective of this trial was to determine the maximum tolerated dose ("MTD") of AI-850. In the dose escalation study, 22 patients with solid tumors (taxane naive patients and patients who previously had received taxane therapy) were treated with AI-850 doses of 36-250 mg/m2 every three weeks in cohorts of 3-6 patients. AI-850 was administered without standard taxane pre-medications. Infusions of AI-850 were delivered in less than 30 minutes at all doses, which is significantly shorter that the three-hour infusion typically required by Taxol. The MTD of AI-850 for patients with extensive prior taxane therapy was 205 mg/m2, which is higher than the Taxol dose of 175 mg/m2 typically used to treat taxane naive patients with metastatic breast cancer.

"We are pleased to have achieved both the objective for the clinical program and for this trial," commented Sherri C. Oberg, President and CEO of Acusphere. "These human proof-of-concept data should help us in our discussions with potential partners that are considering creating or reformulating intravenous formulations of hydrophobic drugs as well as with potential partners who may continue the development of AI-850."

These human data suggest that AI-850 may have significant advantages over Taxol: no pre-medications, faster injections and cheaper and easier administration. Other Cremophor-free formulations of paclitaxel in clinical development may also have some of these advantages relative to Taxol but they incorporate human serum albumin or chemically modified natural products as the carrier matrix. Products containing blood derived substances like albumin are not readily accepted in many countries throughout the world, including most European and Asian countries, because of concerns about the potential transmission of viruses that cause diseases like mad cow disease. Taxol revenues generated outside the United States were about 95% of total revenues in 2003. AI-850 consists of paclitaxel nanoparticles in a porous, hydrophilic matrix, composed primarily of a sugar that has been proven to be innocuous in other injectable drugs.

Dr. David Tuck, Assistant Professor of Pathology, Yale University School of Medicine, Associate Director of the Yale Cancer Center and the Medical Monitor for the Acusphere clinical trial, noted "of the 22 patients with solid tumors enrolled in the study, two patients have received 8 cycles of AI-850 and one demonstrated a partial response (PR) of her disease to AI-850 treatment. We are pleased that the HDDS formulation has allowed us to treat patients with relatively high doses of paclitaxel, without the need and expense of pre-medications and prolonged infusion times."

Acusphere estimates that hydrophobic drugs generated $120 billion in worldwide revenues in 2002. The Company has patents which relate to porous microparticle or nanoparticle compositions of over 150 hydrophobic drugs in a wide variety of therapeutic areas, including steroids, anti-fungals, chemotherapeutics, non-steroidal anti-inflammatories, and calcium channel blockers. The creation of porous microparticle or nanoparticle compositions of these drugs can potentially improve the safety and/or the efficacy of these drugs by improving or controlling how rapidly and fully they dissolve.

About Acusphere, Inc.

Acusphere 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 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 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 III clinical development. AI-700 is designed to be a preferred alternative to the estimated 9.5 million procedures done each year in the U.S. to detect 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.

"Acusphere" and "HDDS" are registered trademarks of Acusphere, Inc.

"Taxol" is a registered trademark of Bristol Myers-Squibb Company.

"Cremophor EL" is a registered trademark of BASF Corporation.

This Release contains forward-looking statements, including statements regarding the safety, efficacy and commercial prospects of AI-850 and Acusphere's ability to develop AI-850 and other improved formulations of hydrophobic drugs generally and to enter into commercial partnerships in the development of these drugs. 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, 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 the Company's filings with the U.S. Securities and Exchange Commission, including the Company's Quarterly Report on Form 10-Q for the period ending March 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.

NOTE TO EDITORS: In the term "mg/m2", the 2 should be superscripted.