EXHIBIT 1.1 CONVERTIBLE EXCHANGEABLE PREFERRED STOCK UNDERWRITING AGREEMENT

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Exhibit 1.1

900,000 Shares

Acusphere, Inc.

CONVERTIBLE EXCHANGEABLE PREFERRED STOCK

UNDERWRITING AGREEMENT

February 17, 2005

PIPER JAFFRAY & CO.
SG COWEN & CO., LLC
C.E. UNTERBERG, TOWBIN, LLC
    As Representatives of the
    several Underwriters named in Schedule I attached hereto (the "Representatives")
c/o Piper Jaffray & Co.
800 Nicollet Mall
Minneapolis, Minnesota 55402

Ladies and Gentlemen:

Acusphere, Inc., a Delaware corporation (the " Company "), proposes, subject to the terms and conditions contained herein, to issue and sell to the underwriters named in Schedule I annexed hereto (the " Underwriters "), for whom you are acting as representatives, an aggregate of 900,000 shares (the " Firm Shares ") of 6.5% Convertible Exchangeable Preferred Stock, $0.01 par value per share (the " Preferred Stock "), of the Company. To the extent there are no additional Underwriters listed on Schedule I other than each of you, the term Representatives as used herein shall mean you, as Underwriters, and the terms Representatives and Underwriters shall mean either the singular or plural as the context requires.

The Preferred Stock is, at the Company's option and subject to certain conditions, exchangeable for the Company's 6.5% convertible subordinated debentures (the " Debentures ") issuable pursuant to an indenture (the " Indenture ") between the Company and The Bank of New York, as trustee (the " Trustee "), to be dated as of the time of purchase (as defined below). The Preferred Stock is and the Debentures, when and if issued, will be, convertible into shares (the " Conversion Shares ") of the Company's common stock, par value $0.01 per share (the " Common Stock "). If the Shares or the Debentures are converted into Common Stock prior to March 1, 2009, the Company will make an additional payment (the " Make-Whole-Payment ") on the Shares or the Debentures, as the case may be, equal to the aggregate amount of dividends or interest, as the case may be, that would have accrued and become payable on the Shares or the Debentures, as the case may be, from the date of original issue of the Shares or the Debentures, as the case may be, through and including March 1, 2009, less any dividends already paid on the Shares or interest already paid on the Debentures, as the case may be. The Make-Whole Payment is payable by the Company, at the Company's option, in cash, in shares of Common Stock or a combination of cash and shares of Common Stock (the " Make-Whole Shares "). In addition, solely for the purpose of covering over-allotments, the Company proposes to grant to the Underwriters the option to purchase from the Company up to an additional 100,000 Shares (the " Additional Shares "). The Firm Shares and the Additional Shares are hereinafter collectively sometimes referred to as the " Shares ." The Shares, the Debentures, the Conversion Shares and the Make-Whole Shares are described in the Prospectus referred to below. This is to confirm the agreement among the Company and the Underwriters concerning the offering, issuance and sale of the Shares.

        1.     Sale and Purchase.     

        (a)   Upon the basis of the representations and warranties and subject to the terms and conditions herein set forth, the Company agrees to issue and sell to the respective Underwriters and each of the Underwriters, severally and not jointly, agrees to purchase from the Company the number of Firm

Shares set forth opposite the name of such Underwriter in Schedule I attached hereto, subject to adjustment in accordance with Section 9 hereof, in each case at a purchase price of $47.00 per Share. The Company is advised by you that the Underwriters intend initially to offer the Firm Shares upon the terms set forth in the Prospectus. You may from time to time increase or decrease the public offering price after the initial public offering to such extent as you may determine.

        (b)   In addition, the Company hereby grants to the several Underwriters the option to purchase, and upon the basis of the representations and warranties and subject to the terms and conditions herein set forth, the Underwriters shall have the right to purchase, severally and not jointly, from the Company, ratably in accordance with the number of Firm Shares to be purchased by each of them, all or a portion of the Additional Shares as may be necessary to cover over-allotments made in connection with the offering of the Firm Shares, at the same purchase price per share to be paid by the Underwriters to the Company for the Firm Shares, plus an additional amount equal to the cash dividend that would have accrued with regard to such Additional Shares pursuant to the Certificate of Designations (defined below) from and including the time of purchase (of the Firm Shares) through the date immediately preceding the applicable additional time of purchase (of such Additional Shares) had such Additional Shares been issued on the time of purchase (of the Firm Shares). This option may be exercised by Piper Jaffray on behalf of the several Underwriters at any time and from time to time on or before the thirtieth day following the date of the Prospectus, by written notice to the Company. Such notice shall set forth the aggregate number of Additional Shares as to which the option is being exercised and the date and time when the Additional Shares are to be delivered (any such date and time being herein referred to as an " additional time of purchase "); provided , however , that an additional time of purchase shall not be earlier than the time of purchase (as defined below) nor earlier than the second business day after the date on which the option shall have been exercised nor later than the tenth business day after the date on which the option shall have been exercised. The number of Additional Shares to be sold to each Underwriter shall be the number that bears the same proportion to the aggregate number of Additional Shares being purchased as the number of Firm Shares set forth opposite the name of such Underwriter on Schedule I hereto bears to the total number of Firm Shares (subject, in each case, to such adjustment as you may determine to eliminate fractional shares), subject to adjustment in accordance with Section 9 hereof.

        2.     Payment and Delivery.     

        (a)   Payment of the purchase price for the Firm Shares shall be made to the Company by Federal Funds wire transfer against delivery of the certificates for the Firm Shares to you through the facilities of The Depository Trust Company (" DTC ") for the respective accounts of the Underwriters. Such payment and delivery shall be made at 10:00 A.M., New York City time, on February 24, 2005 (unless another time shall be agreed to by you and the Company or unless postponed in accordance with the provisions of Section 9 hereof). The time at which such payment and delivery are to be made is hereinafter sometimes called "the time of purchase." Electronic transfer of the Firm Shares shall be made to you at the time of purchase in such names and in such denominations as you shall specify.

        (b)   Payment of the purchase price for the Additional Shares shall be made at an "additional time of purchase" in the same manner and at the same office as the payment for the Firm Shares. Electronic transfer of the Additional Shares shall be made to you at such additional time of purchase in such names and in such denominations as you shall specify.

        (c)    Deliveries of the documents described in Section 5 hereof with respect to the purchase of the Shares shall be made at the offices of Goodwin Procter LLP, 53 State Street, Boston, Massachusetts., at 10:00 A.M., New York City time, at the time of purchase of the Firm Shares or the additional time of purchase of the Additional Shares, as the case may be. All actions taken at the time of purchase shall be deemed to have occurred simultaneously and all actions taken at an additional time of purchase shall be deemed to have occurred simultaneously.

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        3.     Representations and Warranties of the Company.     

        (a)   The Company represents and warrants to, and agrees with, the several Underwriters as of the date hereof, as of the time of purchase and as of each additional time of purchase, as follows:

        (1)   The Company has prepared and filed in conformity with the requirements of the Securities Act of 1933, as amended (the " Act "), and the published rules and regulations thereunder (the " Rules and Regulations ") adopted by the Securities and Exchange Commission (the " Commission ") a Registration Statement (as hereinafter defined) on Form S-3, as amended (No. 333-121618), relating to the Shares and the offering thereof from time to time in accordance with Rule 415 of the Rules and Regulations, and such amendments thereof as may have been required. The Registration Statement includes a prospectus dated January 7, 2005 (the " Base Prospectus ") and a preliminary prospectus supplement dated February 17, 2005 (the " Preliminary Prospectus Supplement "). The Company has filed the Base Prospectus and the Preliminary Prospectus Supplement with the Commission and has filed with, or transmitted for filing to, or shall promptly hereafter file with or transmit for filing to the Commission, a prospectus supplement relating to the Shares in accordance with Rule 424(b) under the Act (the " Final Prospectus Supplement "). The term "Registration Statement" as used in this Agreement means the initial registration statement (including all exhibits, financial schedules and all documents and information deemed to be a part of the Registration Statement (through incorporation by reference or otherwise)), as amended, at the time and on the date it became effective (the " Effective Date "), including the information (if any) contained in the form of final prospectus filed with the Commission pursuant to Rule 424(b) of the Rules and deemed to be part thereof at the time of effectiveness pursuant to Rule 430A of the Rules. The term " Prospectus " as used in this Agreement means the Base Prospectus together with the Preliminary Prospectus Supplement and Final Prospectus Supplement. As used herein, the terms "Base Prospectus," "Prospectus," "Registration Statement," "Preliminary Prospectus Supplement" and "Final Prospectus Supplement" shall include any documents incorporated by reference therein and any reference to any amendment or supplement to the Registration Statement or the Prospectus shall be deemed to refer to and include any document filed under the Exchange Act after the date of the Base Prospectus by the Company with the Commission, that are deemed to be incorporated by reference in the Prospectus.

        (2)   The Company met, at the time it filed the Registration Statement with the Commission, and at all times from such date through the time of purchase and any additional time of purchase has met, the requirements for use of Form S-3 under the Act. On the Effective Date, the Registration Statement complied, and on the date of the Prospectus, the date any post-effective amendment to the Registration Statement becomes effective, the date any Prospectus Supplement or amendment to the Prospectus is filed with the Commission, the time of purchase and any additional time of purchase, the Registration Statement and the Prospectus will comply, in all material respects, with the requirements of the Act and the Rules and Regulations and the Exchange Act and the rules and regulations of the Commission thereunder. The Registration Statement did not, as of the Effective Date, contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and on the filing or first delivery of the Prospectus, the date hereof, the time of purchase and any additional time of purchase neither the Registration Statement nor the Prospectus, nor any amendment thereof or supplement thereto, contained or will contain any untrue statement of a material fact or omitted or will omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading. If applicable, when any related preliminary prospectus was first filed with the Commission (whether filed as part of the Registration Statement or any amendment thereto or pursuant to Rule 424(a) of the Rules and Regulations) and when any amendment thereof or

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supplement thereto was first filed with the Commission, such preliminary prospectus as amended or supplemented complied in all material respects with the applicable provisions of the Act and the Rules and Regulations and did not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading. Notwithstanding the foregoing, none of the representations and warranties in this Section 3(a)(2) shall apply to statements in, or omissions from, the Registration Statement or the Prospectus made in reliance upon, and in conformity with, information herein or otherwise furnished in writing by the Underwriters for use in the Registration Statement or the Prospectus. With respect to the preceding sentence, the Company acknowledges that the only information furnished in writing by the Underwriters for use in the Registration Statement, the Prospectus or any other marketing materials used or to be used in connection with the sale or distribution of the Shares are the statements contained in the first and second paragraphs and the last paragraph under the caption "Underwriting—Commissions and Fees" in the Prospectus Supplement.

        (3)   The Prospectus delivered to the Underwriters for use in connection with this offering was identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T. The Company has not distributed any offering material in connection with the offering and sale of the Shares, other than the Registration Statement, the Preliminary Prospectus and the Prospectus.

        (4)   The Registration Statement has been declared effective under the Act; no stop order of the Commission preventing or suspending the use of the Prospectus or the effectiveness of the Registration Statement has been issued and no proceedings for such purpose have been instituted or, to the Company's knowledge after due inquiry, are contemplated by the Commission. The documents incorporated by reference in the Registration Statement and the Prospectus, at the time they became effective or were filed with the Commission, as the case may be, complied in all material respects with the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder, and at the time they became effective or were filed with the Commission, as the case may be, none of such documents contained an untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, and any further documents so filed and incorporated by reference in the Registration Statement and the Prospectus, when such documents become effective or are filed with the Commission, as the case may be, will conform in all material respects to the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein, in light of the circumstances under which they are made, not misleading.

        (5)   The financial statements of the Company, together with the related notes thereto, included in the Registration Statement and Prospectus comply in all material respects with the requirements of the Act and fairly present the financial condition of the Company as of the dates indicated and the results of operations and changes in cash flows for the periods therein specified in conformity with generally accepted accounting principles in the United States consistently applied throughout the periods involved; and the supporting schedules included in the Registration Statement present fairly the information required to be stated therein and the other financial information included in the Registration Statement and the Prospectus has been derived from the accounting records of the Company and presents fairly the information shown thereby. No other financial statements or schedules are required to be included in the Registration Statement or Prospectus. Any disclosures contained in the Registration Statement or the Prospectus regarding "non-GAAP financial measures" (as such term is defined by the rules and regulations of the Commission) comply with Regulation G of the Exchange Act and Item 10 of Regulation S-K

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under the Act, to the extent applicable. Deloitte & Touche LLP, which has expressed its opinion with respect to the financial statements and schedules filed as a part of the Registration Statement and included in the Registration Statement and Prospectus, is an independent public accounting firm within the meaning of the Act and the Rules and Regulations and such accountants are not in violation of the auditor independence requirements of the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated in connection therewith (the " Sarbanes-Oxley Act "). Except as described in the Prospectus, there are no material off-balance sheet transactions, arrangements, obligations (including contingent obligations), or any other relationships with unconsolidated entities or other persons, that may have a material current or future effect on the Company's financial condition, changes in financial condition, results of operations, liquidity, capital expenditures, capital resources or significant components of revenue or expenses.

        (6)   Each of the Company and its subsidiaries has been duly organized and is validly existing as a corporation in good standing under the laws of its jurisdiction of incorporation. Each of the Company and its subsidiaries has full corporate power and authority to own its properties and conduct its business as currently being carried on and as described in the Registration Statement and Prospectus, and is duly qualified to do business as a foreign corporation in good standing in each jurisdiction in which it owns or leases real property or in which the conduct of its business makes such qualification necessary and in which the failure to so qualify might result in a material adverse change in the general affairs, condition (financial or otherwise), business, prospects, property, operations or results of operations of the Company and its subsidiaries, taken as a whole (" Material Adverse Change "). The Company is not a participant in any joint venture, partnership or similar arrangement.

        (7)   Except as contemplated in the Prospectus, subsequent to the respective dates as of which information is given in the Registration Statement and the Prospectus, neither the Company nor any of its subsidiaries has incurred any material liabilities or obligations, direct or contingent, or entered into any material transactions, or declared or paid any dividends or made any distribution of any kind with respect to its capital stock; and there has not been any change in the capital stock of the Company or any of its subsidiaries, or any material adverse change in the general affairs, condition (financial or otherwise), business, prospects, property, operations or results of operations of the Company and its subsidiaries, taken as a whole (other than a change in the number of outstanding shares of Common Stock due to the issuance of shares upon the exercise of outstanding options or warrants), or any material change in the short-term or long-term debt, or any issuance of options, warrants, convertible securities or other rights to purchase the capital stock, of the Company, or any Material Adverse Change or any development involving a prospective Material Adverse Change.

        (8)   Except as set forth in the Prospectus, there is not pending or, to the knowledge of the Company, threatened or contemplated, any action, suit or proceeding to which the Company or any of its subsidiaries is a party or of which any property or assets of the Company is the subject before or by any court or governmental agency, authority or body, or any arbitrator, which, individually or in the aggregate, might result in any Material Adverse Change. There are no current or pending legal, governmental or regulatory actions, suits or proceedings that are required to be described in the Registrations Statement and Prospectus that have not been so described.

        (9)   There are no statutes, regulations, contracts or documents that are required to be described in the Registration Statement and Prospectus or be filed as exhibits to the Registration Statement by the Act or by the Rules and Regulations that have not been so described or filed.

        (10) The Certificate of Powers, Designations, Preferences, and Rights of the 6.5% Convertible Exchangeable Preferred Stock of the Company in the form described in and filed as an exhibit to

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the Registration Statement (the " Certificate of Designations "), has been heretofore duly authorized and approved in accordance with the Delaware General Corporation Law and shall become effective and shall be in full force and effect on or before the time of purchase and any additional time of purchase.

        (11) The Company has full power and authority to (a) enter into this Agreement and to consummate the transactions contemplated hereby and thereby, (b) authorize, execute, issue, and deliver the Shares as contemplated by this Agreement; (c) authorize, execute and deliver the Indenture and to perform its obligations thereunder; (d) authorize, execute, issue and deliver the Debentures in accordance with the terms of the Certificate of Designations and the Indenture; (e) authorize, execute issue, and deliver the Conversion Shares in accordance with the terms of the Certificate of Designations or the Indenture, as the case may be, and (f) authorize, execute, issue and deliver the Make-Whole Shares in accordance with the terms of the Certificate of Designations or the Indenture, as the case may be.

        (12) This Agreement has been duly authorized, executed and delivered by the Company, and constitute valid, legal and binding obligations of the Company, enforceable in accordance with their terms, except to the extent that rights to indemnity hereunder may be limited by federal or state securities laws and except as such enforceability may be limited by bankruptcy, insolvency, reorganization or similar laws affecting the rights of creditors generally and subject to general principles of equity.

        (13) The Company is not in breach or violation of or in default under (and no event has occurred which with notice, lapse of time or both would result in any breach or violation of, constitute a default under or give the holder of any indebtedness (or a person acting on such holder's behalf) the right to require the repurchase, redemption or repayment of all or a part of such indebtedness under) (x) its Amended and Restated Certificate of Incorporation or Amended and Restated Bylaws, or any indenture, mortgage, deed of trust, bank loan or credit agreement or other evidence of indebtedness or any license to which the Company or any of its subsidiaries is a party or by which the Company, any of its subsidiaries or any of their properties may be bound or affected, (y) any lease, contract or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which the Company, any of its subsidiaries or any of their properties may be bound or affected or (z) any federal, state, local or foreign law, regulation or rule or any decree, judgment or order applicable to the Company or any of its subsidiaries, except, in the case of clauses (y) and (z), for breaches, violations, defaults and events that would not, individually or in the aggregate, reasonably be expected to result in a Material Adverse Change; and the execution, delivery and performance of this Agreement, the Indenture and the Debentures, the issuance and sale of the Shares, the issuance of the Debentures in compliance with the Indenture, the issuance of the Conversion Shares and the issuance of the Make-Whole Shares in compliance with the Certificate of Designations or the Indenture, as the case may be, and the consummation of the transactions contemplated by this Agreement, the Certificate of Designations, the Indenture and the Debentures will not conflict with, result in any breach or violation of or constitute a default under (nor constitute any event which with notice, lapse of time or both would result in any breach or violation of or constitute a default under or give the holder of any indebtedness (or a person acting on such holder's behalf) the right to require the repurchase, redemption or repayment of all or a part of such indebtedness under) (I) the Company's Amended and Restated Certificate of Incorporation or Amended and Restated Bylaws, or any indenture, mortgage, deed of trust, bank loan or credit agreement or other evidence of indebtedness or any license to which the Company or any of its subsidiaries is a party or by which the Company, any of its subsidiaries or any of their properties may be bound or affected, (II) any lease, contract or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which the Company, any of its subsidiaries or any of their properties

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may be bound or affected or (III) any federal, state, local or foreign law, regulation or rule or any decree, judgment or order applicable to the Company or any of its subsidiaries, except, in the case of clause (II), for breaches, violations, defaults and events that would not, individually or in the aggregate, reasonably be expected to result in a Material Adverse Change.

        (14) no approval, authorization, consent or order of or filing with any federal, state, local or foreign governmental or regulatory commission, board, body, authority or agency, or of or with the National Association of Securities Dealers Automated Quotation National Market System (" NASDAQ "), or approval of the stockholders of the Company, is required in connection with the execution, delivery and performance of this Agreement, the Indenture, the issuance and sale of the Shares, the issuance of the Conversion Shares, the issuance of the Debentures, the issuance of the Make-Whole Shares, or the consummation by the Company of the transactions contemplated by this Agreement, the Certificate of Designations, the Indenture and the Debentures, other than the registration of the Shares, the Conversion Shares, the Make-Whole Shares and the Debentures under the Act, the authorization for quotation of the Conversion Shares and Make-Whole Shares on or with the NASDAQ, qualification of the Indenture under the Trust Indenture Act, filing with and acceptance by the Delaware Secretary of State of the Certificate of Designations, each of which has been effected (except for the filing with and acceptance by the Delaware Secretary of State of the Certificate of Designations, which shall occur prior to the time of purchase), any filing for review of the offering of the Shares by the National Association of Securities Dealers, Inc. (the " NASD "), and any necessary qualification under the securities or blue sky laws of the various jurisdictions in which the Shares are being offered by the Underwriters or under the rules and regulations of the NASD.

        (15) At February 14, 2005, the authorized capital stock of the Company consists of 98,500,000 shares of Common Stock and 5,000,000 shares of preferred stock, $0.01 par value per share. After giving effect to the transactions contemplated by this Agreement, on the date hereof:

        a.     The issued and outstanding capital stock of the Company will consist of 17,812,862 shares of Common Stock and 900,000 shares of Convertible Exchangeable Preferred Stock.

        b.     The Company will have (x) 2,666,719 shares of Common Stock reserved for issuance upon the exercise of outstanding options granted under the Company's 1994 Stock Plan and 2003 Stock Option and Incentive Plan, (the " Option Plans ") and (y) 1,317,574 shares of Common Stock reserved for issuance upon the exercise of outstanding warrants.

        c.     The Company will have 975,842 shares of Common Stock available for future grant under the Option Plans.

        d.     The Company will have 229,374 shares of Common Stock reserved for future purchase by employees of the Company under the Company's 2003 Employee Stock Purchase Plan.

Since February 14, 2005, the Company has not issued or entered into any commitment to issue subscriptions, options, warrants, convertible or exchangeable securities or other contracts or rights to purchase any shares of the capital stock of the Company or any of its subsidiaries (other than pursuant to the exercise of stock options and warrants to purchase Common Stock outstanding on February 14, 2005, pursuant to the Option Plans and pursuant to the Company's 2003 Employee Stock Purchase Plan).

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        (16) With the exception of the foregoing in Section 3(a)(15), there are no outstanding subscriptions, options, warrants, convertible or exchangeable securities or other contracts or other rights in existence granted to or by the Company or any of its subsidiaries to purchase any shares of the capital stock of the Company or any of its subsidiaries and there are no commitments, plans or arrangements to issue any shares of the capital stock of the Company or any of its subsidiaries or any subscriptions, options, warrants, convertible or exchangeable securities or other contracts or other rights to purchase any shares of the capital stock of the Company or any of its subsidiaries.

        (17) All of the issued and outstanding shares of capital stock of the Company are duly authorized and validly issued, fully paid and nonassessable, have been issued in compliance with all federal and state securities laws, the issuance thereof was free of statutory and contractual preemptive rights, resale rights, rights of first refusal and similar rights, and the holders thereof are not subject to personal liability by reason of being such holders.

        (18) All of the issued and outstanding shares of capital stock of each of the Company's subsidiaries are duly authorized and validly issued, fully paid and nonassessable, have been issued in compliance with all federal and state securities laws, the issuance thereof was free of statutory and contractual preemptive rights, resale rights, rights of first refusal and similar rights, and the holders thereof are not subject to personal liability by reason of being such holders. Except as otherwise described in the Registration Statement and Prospectus and except for any directors' qualifying shares, the Company owns of record and beneficially, free and clear of any security interests, claims, liens, proxies, equities or other encumbrances, all of the issued and outstanding shares of capital stock of each of the Company's subsidiaries.

        (19) The Shares have been duly and validly authorized and, when issued and delivered against payment therefor as provided in this Agreement, will be duly and validly issued, fully paid and non-assessable and free of statutory and contractual preemptive rights, resale rights, rights of first refusal and similar rights, and the holders thereof will not be subject to personal liability by reason of being such holders. The capital stock of the Company, including the Shares, the Conversion Shares and the Make-Whole Shares, conforms in all material respects to the descriptions thereof contained in the Registration Statement and the Prospectus, and the certificates for the Shares and the Common Stock are in due and proper form.

        (20) The Conversion Shares have been duly authorized and reserved for issuance upon conversion of the Shares or the Debentures, as the case may be, and if and when issued in accordance with the Certificate of Designations or the Indenture, as the case may be, will be duly and validly issued, fully paid and nonassessable and free of statutory and contractual preemptive rights, resale rights, rights of first refusal and similar rights, and the holders thereof will not be subject to personal liability by reason of being such holders.

        (21) Upon payment of any Make-Whole Payment in shares of Common Stock pursuant to the terms of the Certificate of Designations or the Indenture, as the case may be, the Make-Whole Shares will be duly authorized and validly issued, fully paid and nonassessable and free of statutory and contractual preemptive rights, resale rights, rights of first refusal and similar rights, and the holders thereof will not be subject to personal liability by reason of being such holders.

        (22) The Debentures are in the form contemplated by the Indenture, have been duly authorized by the Company for issuance pursuant to the terms of the Indenture and, when executed by the Company and authenticated by the Trustee in the manner provided in the Indenture, will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms, except as the enforcement thereof may be limited by bankruptcy, insolvency, reorganization, moratorium or other similar laws relating to or affecting enforcement of the rights and remedies of creditors or by general equitable principles.

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        (23) Except as otherwise stated in the Registration Statement and Prospectus, there are no preemptive rights or other rights to subscribe for or to purchase, or any restriction upon the voting or transfer of, any shares of the Company's capital stock pursuant to the Company's charter, by-laws or any agreement or other instrument to which the Company is a party or by which the Company is bound. Neither the filing of the Registration Statement nor the offering or sale of the Shares as contemplated by this Agreement gives rise to any rights for or relating to the registration of any shares of capital stock or other securities of the Company.

        (24) The Indenture has been duly and validly authorized by the Company, and assuming due authorization, execution and delivery of the Indenture by the Trustee, constitute a legally valid and binding agreement of the Company, enforceable against the Company in accordance with its terms, except as the enforcement thereof may be limited by bankruptcy, insolvency, reorganization, moratorium or other similar laws relating to or affecting enforcement of the rights and remedies of creditors or by general equitable principles: the Indenture (x) has been duly qualified under the Trust Indenture Act of 1939, as amended (the " Trust Indenture Act ") and (y) complies as to form with the requirements of the Trust Indenture Act; no event has occurred nor has any circumstance arisen which, had the Debentures been issued on the date hereof, would constitute an Event of Default (as such term is defined in the Indenture).

        (25) Since September 30, 2004, the business and operations of the Company have been conducted in the ordinary course consistent with past practice, and, except as specifically disclosed in the SEC Documents, there has not been:

        a.     any declaration, setting aside or payment of any dividend or other distribution of the assets of the Company with respect to any shares of capital stock of the Company or any repurchase, redemption or other acquisition by the Company or any subsidiary of the Company of any outstanding shares of the Company's capital stock;

        b.     any damage, destruction or loss, whether or not covered by insurance, except for such occurrences, individually and collectively, that have not had, and would not reasonably be expected to result in, a Material Adverse Change;

        c.     any waiver by the Company of a valuable right or of a material debt owed to it, except for such waivers, individually and collectively, that have not had, and would not reasonably be expected to result in, a Material Adverse Change;

        d.     the incurrence of any liability or obligation, direct or contingent, for borrowed money, other than trade payable financing incurred in the ordinary course of business consistent with past practice;

        e.     any change by the Company in its accounting principles, methods or practices or in the manner in which it keeps its accounting books and records, except any such change required by a change in GAAP or by the Commission; or

        f.      any other event or condition of any character, except for such events and conditions that have not resulted, and would not reasonably be expected to result, either individually or collectively, in a Material Adverse Change.

        (26) The Company and each of its subsidiaries possesses all material licenses, certificates, permits and other authorizations issued by, and has made all declarations and filings with, the appropriate federal, state, local or foreign governmental or regulatory authorities that are necessary for the ownership or lease of its properties or the conduct of its business; except as described in the Prospectus, the Company has not received notice of any revocation or modification of any such license, certificate, permit or authorization and has no reason to believe that any such license, certificate, permit or authorization will not be renewed in the ordinary

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course; and the Company is in compliance in all material respects with all applicable federal, state, local and foreign laws, regulations, orders and decrees.

        (27) The Company and each of its subsidiaries has good and marketable title to all property (whether real or personal) described in the Registration Statement and Prospectus as being owned by it, in each case free and clear of all liens, claims, security interests, other encumbrances or defects except such as are described in the Registration Statement and the Prospectus. The property held under lease by the Company and each of its subsidiaries is held by it under valid, subsisting and enforceable leases with only such exceptions with respect to any particular lease as do not interfere in any material respect with the conduct of the business of the Company or its subsidiaries.

        (28) The information contained in the Registration Statement and the Prospectus concerning the issued patents and pending patent applications, owned by or licensed to the Company and its subsidiaries is accurate in all material respects. The Company and its subsidiaries own or possess rights from all necessary third parties (the " Licensors ") to use any patents, trademarks, trade names, service marks, service names, copyrights, confidential and proprietary information, including trade secrets, know-how, inventions and technology, whether patented or not, proprietary computer software and other intellectual property rights (collectively, the "Intellectual Property") necessary to conduct the respective businesses of the Company and its subsidiaries in the manner in which they have been and are contemplated to be conducted, as described in the Prospectus, and without any conflict with the rights of others, except as described in the Prospectus and except for such conflicts that, if determined adversely to the Company or its subsidiaries, would not, singly or in the aggregate, be reasonably expected to result in a Material Adverse Change. Except as described in the Prospectus, neither the Company nor any of its subsidiaries has knowledge that, or has received any notice from any other person alleging that, the businesses of the Company and its subsidiaries in the manner in which they have been and are contemplated to be conducted, as described in the Prospectus, conflict with the Intellectual Property rights of others, except for such conflicts that, if determined adversely to the Company or the Subsidiaries, would not have, singly or in the aggregate, be reasonably expected to result in a Material Adverse Change.

        (29) All patent applications owned by or licensed to the Company or any of its subsidiaries that are material to the conduct of the respective businesses of the Company and its subsidiaries in the manner in which they have been and are contemplated to be conducted have been duly and properly filed or caused to be filed with the United States Patent and Trademark Office (" PTO ") and, in some cases, applicable foreign and international patent authorities, and assignments for all patents and patent applications owned by or licensed to the Company or any of its subsidiaries that are material to the conduct of the respective businesses of the Company and its subsidiaries in the manner in which they have been and are contemplated to be conducted (collectively, the " Patent Rights ") have been properly executed and recorded for each named inventor. To the knowledge of the Company, all printed publications and patent references material to the patentability of the inventions claimed in the Patent Rights have been disclosed to those patent offices so requiring. To the knowledge of the Company, each of the Company and its subsidiaries, their assignors or the Licensors, as applicable, has met its duty of candor and good faith to the PTO for the Patent Rights. To the knowledge of the Company, no material misrepresentation has been made to any patent office in connection with the Patent Rights. Neither the Company nor any of its subsidiaries is aware of any facts material to a determination of patentability regarding the Patent Rights not disclosed to the PTO or other applicable patent office. Neither the Company nor any of its subsidiaries is aware of any facts not disclosed to the PTO or other applicable patent office that would preclude the patentability, validity or enforceability of any patent or patent application in the Patent Rights. The Company has no knowledge of any facts that would

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preclude the Company, its subsidiaries or the Licensors, as applicable, from having clear title to the patents and patent applications in the Patent Rights. To the knowledge of the Company, the patents in the Patent Rights are valid and enforceable, and have not been adjudged invalid or unenforceable in whole or in part.

        (30) To the knowledge of the Company, no third party is engaging in any activity that infringes, misappropriates or otherwise violates the Intellectual Property owned by or licensed to the Company or its subsidiaries, except as described in the Prospectus and except for such activities that, singly or in the aggregate, would not be reasonably expected to result in a Material Adverse Change.

        (31) With respect to each material agreement governing all rights in and to any Intellectual Property licensed by or licensed to the Company or any of its subsidiaries: (i) such agreement is valid and binding and in full force and effect; (ii) neither the Company nor any of its subsidiaries has received any notice of termination or cancellation under such agreement, received any notice of breach or default under such agreement, which breach has not been cured, or granted to any third party any rights, adverse or otherwise, under such agreement that would constitute a material breach of such agreement; and (iii) none of the Company, its subsidiaries or, to the knowledge of the Company, any other party to such agreement, is in breach or default thereof in any material respect, and no event has occurred that, with notice or lapse of time, would constitute such a material breach or default or permit termination, modification or acceleration under such agreement.

        (32) The Company and each of its subsidiaries have timely filed all federal, state, local and foreign income and franchise tax returns required to be filed and is not in default in the payment of any taxes which were payable pursuant to said returns or any assessments with respect thereto, other than any which the Company or any of its subsidiaries is contesting in good faith. There is no pending dispute with any taxing authority relating to any of such returns and the Company has no knowledge of any proposed liability for any tax to be imposed upon the properties or assets of the Company or any of its subsidiaries for which there is not an adequate reserve reflected in the Company's financial statements included in the Registration Statement.

        (33) The Common Stock of the Company is registered and listed on the NASDAQ under the ticker symbol "ACUS." The Company has not received any notice that it is not in compliance with the listing or maintenance requirements of the NASDAQ. The Company is, and has no reason to believe that it will not in the foreseeable future continue to be (except as a result of minimum trading price requirements), in compliance with all such listing and maintenance requirements. The Company has discussed the terms of the Preferred Stock with representatives of the NASDAQ has not been informed that the issuance and sale of the Shares under this will contravene the rules and regulations of the NASDAQ. There are no affiliations with the NASD among the Company's officers or directors. A Registration Statement relating to the Common Stock on Form 8-A or other applicable form under the Exchange Act has become effective.

        (34) Other than the subsidiaries of the Company listed in Exhibit 21 to the Registration Statement, the Company, directly or indirectly, owns no capital stock or other equity or ownership or proprietary interest in any corporation, partnership, association, trust or other entity.

        (35) The Company maintains a system of internal accounting controls sufficient to provide reasonable assurances that (w) transactions are executed in accordance with management's general or specific authorization; (x) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles in the United States and to maintain accountability for assets; (y) access to assets is permitted only in accordance with management's general or specific authorization; and (z) the recorded accountability for assets is compared with existing assets at reasonable intervals and appropriate

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action is taken with respect to any differences. Since the date of the most recent evaluation of such, there has been no change in internal control over financial reporting, including any corrective actions with regard to significant deficiencies and material weaknesses.

        (36) The Chief Executive Officer and the Chief Financial Officer of the Company have signed, and the Company has furnished to the Commission, all certifications required by Sections 302 and 906 of the Sarbanes-Oxley Act. Such certifications contain no qualifications or exceptions to the matters certified therein other than such qualifications or exceptions as are part of the standard form of certification promulgated by the Commission, and have not been modified or withdrawn; and neither the Company nor any of its officers has received notice from any governmental entity questioning or challenging the accuracy, completeness, form or manner of filing or submission of such certifications. The Company is otherwise in compliance in all material respects with all applicable effective provisions of the Sarbanes-Oxley Act and the rules and regulations issued thereunder by the Commission.

        (37) The Company's board of directors has validly appointed an audit committee whose composition satisfies the requirements of Rule 4350(d)(2) of the Rules of the NASD (the " NASD Rules ") and the Company's board of directors and/or the audit committee has adopted a charter that satisfies the requirements of Rule 4350(d)(1) of the NASD Rules. Neither the Company's board of directors nor the audit committee has been informed, nor is any director of the Company aware, of (x) any significant deficiencies in the design or operation of the Company's internal controls that could adversely affect the Company's ability to record, process, summarize and report financial data or any material weakness in the Company's internal controls; or (y) any fraud, whether or not material, that involves management or other employees of the Company who have a significant role in the Company's internal controls.

        (38) No relationship, direct or indirect, exists between or among the Company or any of its subsidiaries on the one hand, and the directors, officers, stockholders, customers or suppliers of the Company or any of its subsidiaries on the other hand, that is required to be described in the Prospectus that is not so described. Neither the Company nor or any of its subsidiaries has, directly or indirectly, extended or maintained credit, or arranged for the extension of credit, or renewed an extension of credit, in the form of a personal loan to or for any of its directors or executive officers in violation of applicable laws, including Section 402 of the Sarbanes-Oxley Act.

        (39) Except as described in the Prospectus and the Registration Statement, each of the Company and its subsidiaries: (u) is and at all times has been in material compliance with all statutes, rules, regulations, or guidances applicable to the ownership, testing, development, manufacture, packaging, processing, use, distribution, marketing, labeling, promotion, sale, offer for sale, storage, import, export or disposal of any product manufactured or distributed by the Company (" Applicable Laws "); (v) has not received any FDA Form 483, notice of adverse finding, warning letter, untitled letter or other correspondence or notice from the U.S. Food and Drug Administration or any other federal, state or foreign governmental authority having authority over the Company (" Governmental Authority ") alleging or asserting material noncompliance with any Applicable Laws or any licenses, certificates, approvals, clearances, authorizations, permits and supplements or amendments thereto required by any such Applicable Laws ("Authorizations"); (w) possesses all Authorizations and such Authorizations are valid and in full force and effect and are not in material violation of any term of any such Authorizations; (x) has not received notice of any claim, action, suit, proceeding, hearing, enforcement, investigation, arbitration or other action from any Governmental Authority or third party alleging that any product, operation or activity is in violation of any Applicable Laws or Authorizations and have no knowledge that any such Governmental Authority or third party is considering any such claim, litigation, arbitration, action, suit, investigation or proceeding; (y) has not received notice that any Governmental Authority has ta