Acusphere Announces Completion of Second Closing of $21.5 Million Private Financing.

WATERTOWN, Mass. -- Acusphere, Inc. (NASDAQ: ACUS) announced today that it has completed the second and final closing of a $21.5 million private placement of newly issued shares of common stock and the concurrent issuance of warrants for the purchase of additional shares of common stock to certain institutional and accredited investors. The second closing resulted in the issuance of 574,000 shares of common stock at a price of $6.25 per share and warrants to purchase up to 115,000 additional shares of common stock at an exercise price of $8.50 per share, resulting in aggregate gross proceeds to the Company of approximately $3.6 million. SG Cowen & Co., LLC served as exclusive placement agent for the financing and received a customary fee from the Company.

The shares of common stock and warrants sold in the private placement have not been registered under the Securities Act of 1933, as amended, or state securities laws and may not be offered or sold in the United States absent registration with the Securities and Exchange commission or an applicable exemption from the registration requirements. The shares and warrants were offered and sold only to institutional and accredited investors. The Company has agreed to file a registration statement with the Securities and Exchange Commission covering the resale of the shares of common stock issued in the private placement and the shares of common stock issued upon exercise of the warrants.

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 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 3 clinical development. AI-700 is designed to be used in a preferred alternative procedure to the estimated 9.5 million procedures 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, including statements regarding the Company's expectations regarding the filing of a registration statement covering the securities offered in the private placement. The Company's actual results may differ materially from those anticipated in these forward-looking statements based upon a number of factors, including risks related to the Securities and Exchange Commission declaring the registration statement effective on a timely basis 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 quarter ended June 30, 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.