Document:

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                               BIOPURE CORPORATION

                    2,500,000 Shares of Class A Common Stock

                             Underwriting Agreement

                                                                  March 13, 2000

J.P. Morgan Securities Inc.
Salomon Smith Barney Inc.
Adams, Harkness & Hill, Inc.
Robert W. Baird & Co. Incorporated
     As Representatives of the several Underwriters
     listed in Schedule I hereto
c/o J.P. Morgan Securities Inc.
60 Wall Street
New York, New York  10260

Ladies and Gentlemen:

         Biopure Corporation, a Delaware corporation (the "COMPANY"), proposes
to issue and sell to the several Underwriters listed in Schedule I hereto (the
"UNDERWRITERS"), for whom you are acting as representatives (the
"REPRESENTATIVES"), an aggregate of 2,500,000 shares of Class A Common Stock,
par value $0.01 per share, of the Company (the "UNDERWRITTEN SHARES") and, for
the sole purpose of covering over-allotments in connection with the sale of the
Underwritten Shares, at the option of the Underwriters, up to an additional
375,000 shares of Class A Common Stock of the Company (the "OPTION SHARES"). The
Underwritten Shares and the Option Shares are herein referred to as the
"SHARES." The shares of Class A Common Stock of the Company to be outstanding
after giving effect to the sale of the Shares are herein referred to as the
"CLASS A COMMON STOCK."

         The Company has prepared and filed with the Securities and Exchange
Commission (the "COMMISSION"), in accordance with the provisions of the
Securities Act of 1933, as amended, and the rules and regulations of the
Commission thereunder (collectively, the "SECURITIES ACT"), a registration
statement, including a prospectus, relating to the Shares. The registration
statement as amended at the time when it became or shall become effective,
including information (if any) deemed to be part of the registration statement
at the time of effectiveness pursuant to Rule 430A under the Securities Act, is
referred to in this Agreement as the "REGISTRATION STATEMENT," and the
prospectus in the form first used to confirm sales of Shares is referred to in
this Agreement as the "PROSPECTUS." If the Company has filed an abbreviated
registration statement pursuant to Rule 462(b) under the Securities Act (the
"RULE

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462 REGISTRATION STATEMENT"), then any reference herein to the term
"Registration Statement" shall be deemed to include such Rule 462 Registration
Statement.

         The Company hereby agrees with the Underwriters as follows:

         1. The Company agrees to issue and sell the Underwritten Shares to the
several Underwriters as hereinafter provided, and each Underwriter, upon the
basis of the representations and warranties herein contained, but subject to the
conditions hereinafter stated, agrees to purchase, severally and not jointly,
from the Company the respective number of Underwritten Shares set forth opposite
such Underwriter's name in Schedule I hereto at a purchase price per share (the
"PURCHASE PRICE") of $32.90.

         In addition, the Company agrees to issue and sell the Option Shares to
the several Underwriters as hereinafter provided, and the Underwriters on the
basis of the representations and warranties herein contained, but subject to the
conditions hereinafter stated, shall have the option to purchase, severally and
not jointly, from the Company up to an aggregate of 375,000 Option Shares at the
Purchase Price, for the sole purpose of covering over-allotments (if any) in the
sale of Underwritten Shares by the several Underwriters.

         If any Option Shares are to be purchased, the number of Option Shares
to be purchased by each Underwriter shall be the number of Option Shares which
bears the same ratio to the aggregate number of Option Shares being purchased as
the number of Underwritten Shares set forth opposite the name of such
Underwriter in Schedule I hereto (or such number increased as set forth in
Section 9 hereof) bears to the aggregate number of Underwritten Shares being
purchased from the Company by the several Underwriters, subject, however, to
such adjustments to eliminate any fractional Shares as the Representatives in
their sole discretion shall make.

         The Underwriters may exercise the option to purchase the Option Shares
at any time (but not more than once) on or before the thirtieth day following
the date of this Agreement, by written notice from the Representatives to the
Company. Such notice shall set forth the aggregate number of Option Shares as to
which the option is being exercised and the date and time when the Option Shares
are to be delivered and paid for, which may be the same date and time as the
Closing Date (as hereinafter defined) but shall not be earlier than the Closing
Date nor later than the tenth full Business Day (as hereinafter defined) after
the date of such notice (unless such time and date are postponed in accordance
with the provisions of Section 9 hereof). Any such notice shall be given at
least two Business Days prior to the date and time of delivery specified
therein.

         2. The Company understands that the Underwriters intend (i) to make a
public offering of the Shares as soon after (A) the Registration Statement has
become effective (if it has not already become effective) and (B) the parties
hereto have executed and de-

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livered this Agreement as in the judgment of the Representatives is advisable
and (ii) initially to offer the Shares upon the terms set forth in the
Prospectus.

         3. Payment for the Shares shall be made by wire transfer in immediately
available funds to the account specified by the Company to the Representatives,
in the case of the Underwritten Shares, on March 17, 2000, or at such other time
on the same or such other date, not later than the fifth Business Day
thereafter, as the Representatives and the Company may agree upon in writing or,
in the case of the Option Shares, on the date and time specified by the
Representatives in the written notice of the Underwriters' election to purchase
such Option Shares. The time and date of such payment for the Underwritten
Shares is referred to herein as the "CLOSING DATE" and the time and date for
such payment for the Option Shares, if other than the Closing Date, is herein
referred to as the "ADDITIONAL CLOSING DATE." As used herein, the term "BUSINESS
DAY" means any day other than a day on which banks are permitted or required to
be closed in New York City.

         Payment for the Shares to be purchased on the Closing Date or the
Additional Closing Date, as the case may be, shall be made against delivery to
the Representatives for the respective accounts of the several Underwriters of
the Shares to be purchased on such date registered in such names and in such
denominations as the Representatives shall request in writing not later than two
full Business Days prior to the Closing Date or the Additional Closing Date, as
the case may be, with any transfer taxes payable in connection with the transfer
to the Underwriters of the Shares duly paid by the Company. The certificates for
the Shares will be made available for inspection and packaging by the
Representatives at the office of J.P. Morgan Securities Inc. set forth above not
later than 1:00 P.M., New York City time, on the Business Day prior to the
Closing Date or the Additional Closing Date, as the case may be.

         4. The Company hereby represents and warrants to each of the several
Underwriters that:

         (a) no order preventing or suspending the use of any preliminary
     prospectus has been issued by the Commission, and each preliminary
     prospectus filed as part of the Registration Statement as originally filed
     or as part of any amendment thereto, or filed pursuant to Rule 424 under
     the Securities Act, complied when so filed in all material respects with
     the Securities Act, and did 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 the light of the circumstances
     under which they were made, not misleading; provided that this
     representation and warranty shall not apply to any statements or omissions
     made in reliance upon and in conformity with information relating to any
     Underwriter furnished to the Company in writing by such Underwriter through
     the Representatives expressly for use therein;

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         (b) no stop order suspending the effectiveness of the Registration
     Statement has been issued and no proceeding for that purpose has been
     instituted or, to the knowledge of the Company, threatened by the
     Commission; and the Registration Statement and Prospectus (as amended or
     supplemented if the Company shall have furnished any amendments or
     supplements thereto) comply, or will comply, as the case may be, in all
     material respects with the Securities Act and do not and will not, as of
     the applicable effective date as to the Registration Statement and any
     amendment thereto and as of the date of the Prospectus and any amendment or
     supplement thereto, contain any untrue statement of a material fact or omit
     to state any material fact required to be stated therein or necessary to
     make the statements therein not misleading, and the Prospectus, as amended
     or supplemented, if applicable, at the Closing Date or Additional Closing
     Date, as the case may be, will not contain any untrue statement of a
     material fact or omit to state a material fact necessary to make the
     statements therein, in the light of the circumstances under which they were
     made, not misleading; except that the foregoing representations and
     warranties shall not apply to statements or omissions in the Registration
     Statement or the Prospectus made in reliance upon and in conformity with
     information relating to any Underwriter furnished to the Company in writing
     by such Underwriter through the Representatives expressly for use therein;

         (c) the consolidated financial statements, and the related notes
     thereto, included in the Registration Statement and the Prospectus present
     fairly the consolidated financial position of the Company and its
     consolidated subsidiaries as of the dates indicated and the results of
     their operations and changes in their consolidated cash flows for the
     periods specified; said financial statements have been prepared in
     conformity with generally accepted accounting principles applied on a
     consistent basis, and the supporting schedules, if any, included in the
     Registration Statement present fairly the information required to be stated
     therein;

         (d) since the respective dates as of which information is given in the
     Registration Statement and the Prospectus, there has not been any change in
     the capital stock or long-term debt of the Company or any of its
     subsidiaries, or any material adverse change, or any development that could
     be reasonably expected to involve a prospective material adverse change, in
     or affecting the business, prospects, management, financial position,
     stockholders' equity or results of operations of the Company and its
     subsidiaries, taken as a whole (a "MATERIAL ADVERSE Change"), other than as
     set forth or contemplated in the Prospectus; and except as set forth or
     contemplated in the Prospectus neither the Company nor any of its
     subsidiaries has entered into any transaction or agreement (whether or not
     in the ordinary course of business) material to the Company and its
     subsidiaries taken as a whole;

         (e) the Company has been duly incorporated and is validly existing as a
     corporation in good standing under the laws of the State of Delaware, with
     power and

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     authority (corporate and other) to own its properties and conduct its
     business as described in the Prospectus, and has been duly qualified as a
     foreign corporation for the transaction of business and is in good standing
     under the laws of each other jurisdiction in which it owns or leases
     properties, or conducts any business, so as to require such qualification,
     other than where the failure to be so qualified or in good standing would
     not have a material adverse effect on the Company and its subsidiaries,
     taken as a whole;

         (f) each of the Company's U.S. subsidiaries has been duly incorporated
     and is validly existing as a corporation under the laws of its jurisdiction
     of incorporation, with power and authority (corporate and other) to own its
     properties and conduct its business as described in the Prospectus, and has
     been duly qualified as a foreign corporation for the transaction of
     business and is in good standing under the laws of each jurisdiction in
     which it owns or leases properties, or conducts any business, so as to
     require such qualification, other than where the failure to be so qualified
     or in good standing would not have a material adverse effect on the
     business, prospects, management, financial position, stockholders' equity
     or results of operations of the Company and its subsidiaries, taken as a
     whole (a "MATERIAL ADVERSE EFFECT"); and all the outstanding shares of
     capital stock of each subsidiary of the Company have been duly authorized
     and validly issued, are fully paid and non-assessable, and all of the
     outstanding shares of capital stock of each subsidiary of the Company owned
     by the Company are owned, directly or indirectly, free and clear of all
     liens, encumbrances, security interests and claims;

         (g) this Agreement has been duly authorized, executed and delivered by
     the Company;

         (h) the Company has an authorized capitalization as set forth in the
     Prospectus and such authorized capital stock conforms as to legal matters
     to the description thereof set forth in the Prospectus, and all of the
     outstanding shares of capital stock of the Company have been duly
     authorized and validly issued, are fully paid and non-assessable and except
     as described in the Prospectus are not subject to any pre-emptive rights;
     and, except as described in or expressly contemplated by the Prospectus,
     there are no outstanding rights (including, without limitation, pre-emptive
     rights), warrants or options to acquire, or instruments convertible into or
     exchangeable for, any shares of capital stock or other equity interest in
     the Company or any of its subsidiaries, or any contract, commitment,
     agreement, understanding or arrangement of any kind relating to the
     issuance of any capital stock of the Company or any such subsidiary, any
     such convertible or exchangeable securities or any such rights, warrants or
     options;

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         (i) the Shares to be issued and sold by the Company hereunder have been
     duly authorized and, when issued and delivered to and paid for by the
     Underwriters in accordance with the terms of this Agreement, will be duly
     issued and will be fully paid and non-assessable and will conform to the
     description thereof set forth in the Prospectus; and the issuance of the
     Shares is not subject to any preemptive or similar rights;

         (j) neither the Company nor any of its subsidiaries is, or with the
     giving of notice or lapse of time or both would be, in violation of or in
     default under its certificate of incorporation or by-laws or any indenture,
     mortgage, deed of trust, loan agreement or other agreement or instrument to
     which the Company or any of its subsidiaries is a party or by which it or
     any of them or any of their respective properties is bound, except for
     violations and defaults which would not, individually or in the aggregate,
     have a Material Adverse Effect; the issue and sale of the Shares and the
     performance by the Company of its obligations hereunder and the
     consummation of the transactions contemplated herein will not conflict with
     or result in a breach or violation of any of the terms or provisions of, or
     constitute a default under, any indenture, mortgage, deed of trust, loan
     agreement or other agreement or instrument to which the Company or any of
     its subsidiaries is a party or by which the Company or any of its
     subsidiaries is bound or to which any of the property or assets of the
     Company or any of its subsidiaries is subject, nor will any such action
     result in any violation of the provisions of the certificate of
     incorporation or by-laws of the Company or any applicable law or statute or
     any order, rule or regulation of any court or governmental agency or body
     having jurisdiction over the Company, its subsidiaries or any of their
     respective properties; and no consent, approval, authorization, order,
     license, registration or qualification of or with any such court or
     governmental agency or body is required for the issue and sale of the
     Shares or the consummation by the Company of the transactions contemplated
     herein, except such consents, approvals, authorizations, orders, licenses,
     registrations or qualifications as have been obtained or made under the
     Securities Act and as may be required under state securities or Blue Sky
     laws in connection with the purchase and distribution of the Shares by the
     Underwriters;

         (k) other than as set forth or contemplated in the Prospectus, there
     are no legal or governmental investigations, actions, suits or proceedings
     pending or, to the knowledge of the Company, threatened against or
     affecting the Company or any of its subsidiaries or any of their respective
     properties or to which the Company or any of its subsidiaries is or may be
     a party or to which any property of the Company or any of its subsidiaries
     is or may be subject which, if determined adversely to the Company or any
     of its subsidiaries, could, individually or in the aggregate, reasonably be
     expected to have, a Material Adverse Effect, and, to the knowledge of the
     Company, no such proceedings are threatened or contemplated by governmental
     authorities or threatened by others;

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         (l) there are no statutes, regulations, contracts or other documents or
     legal or governmental investigations, actions, suits or proceedings pending
     or, to the knowledge of the Company, threatened that are required to be
     described in the Registration Statement or Prospectus or to be filed as
     exhibits to the Registration Statement, as the case may be, that are not
     described or filed as required;

         (m) the Company and its subsidiaries have good and marketable title in
     fee simple to all items of real property and good and marketable title to
     all personal property owned by them, in each case free and clear of all
     liens, encumbrances and defects except such as are described or referred to
     in the Prospectus or such as do not materially affect the value of such
     property and do not interfere with the use made or proposed to be made of
     such property by the Company and its subsidiaries; and any real property
     and buildings held under lease by the Company and its subsidiaries are held
     by them under valid, existing and enforceable leases with such exceptions
     as are not material and do not interfere with the use made or proposed to
     be made of such property and buildings by the Company and its subsidiaries;

         (n) 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, which is required by the Securities Act to
     be described in the Registration Statement and the Prospectus which is not
     so described;

         (o)no person has the right to require the Company to register any
     securities for offering and sale under the Securities Act by reason of the
     filing of the Registration Statement with the Commission or the issue and
     sale of the Shares, except for rights which have been waived or obviated by
     decision of the Representatives;

         (p) the Company is not and, after giving effect to the offering and
     sale of the Shares, will not be an "investment company" or an entity
     "controlled" by an "investment company," as such terms are defined in the
     Investment Company Act of 1940, as amended (the "Investment Company Act");

         (q) the Company has complied with all provisions of Section 517.075,
     Florida Statutes (Chapter 92-198, Laws of Florida) relating to doing
     business with the Government of Cuba or with any person or affiliate
     located in Cuba;

         (r) Ernst & Young LLP, who have certified certain financial statements
     of the Company and its subsidiaries, are independent public accountants as
     required by the Securities Act;

         (s) the Company and its subsidiaries have filed all federal, state,
     local and foreign tax returns which have been required to be filed and have
     paid all taxes shown

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     thereon and all assessments received by them or any of them to the extent
     that such taxes have become due and are not being contested in good faith
     except where the failure to file or pay would not, individually or in the
     aggregate, have a Material Adverse Effect; and there is no tax deficiency
     which has been or might reasonably be expected to be asserted or threatened
     against the Company or any subsidiary except for such tax deficiencies as
     would not, individually or in the aggregate, be expected to have a Material
     Adverse Effect;

         (t) the Company has not taken nor will it take, directly or indirectly,
     any action designed to, or that might be reasonably expected to, cause or
     result in stabilization or manipulation of the price of the Class A Common
     Stock;

         (u) each of the Company and its subsidiaries owns, possesses or has
     obtained all licenses, permits, certificates, consents, orders, approvals
     and other authorizations from, and has made all declarations and filings
     with, all federal, state, local and other governmental authorities
     (including foreign regulatory agencies), all self-regulatory organizations
     and all courts and other tribunals, domestic or foreign, necessary to own
     or lease, as the case may be, and to operate its properties and to carry on
     its business as conducted as of the date hereof, except where the failure
     to own, possess, obtain or make would not, individually or in the
     aggregate, have a Material Adverse Effect, and neither the Company nor any
     such subsidiary has received any actual notice of any proceeding relating
     to revocation or modification of any such license, permit, certificate,
     consent, order, approval or other authorization, except as described in the
     Registration Statement and the Prospectus; each of the Company and its
     subsidiaries is in compliance with all laws and regulations relating to the
     conduct of its business as conducted as of the date hereof; and all of the
     descriptions in the Registration Statement and the Prospectus of the legal
     and governmental proceedings and procedures by or before the United States
     Food and Drug Administration (the "FDA") or any foreign, state or local
     governmental body exercising comparable authority are true and complete in
     all material respects;

         (v) there are no existing or, to the knowledge of the Company,
     threatened labor disputes with the employees of the Company or any of its
     subsidiaries which could reasonably be expected to have a Material Adverse
     Effect;

         (w) the Company and its subsidiaries (i) are in compliance with any and
     all applicable foreign, federal, state and local laws and regulations
     relating to the protection of human health and safety, the environment or
     hazardous or toxic substances or wastes, pollutants or contaminants
     ("ENVIRONMENTAL LAWS"), (ii) have received all permits, licenses or other
     approvals required of them under applicable Environmental Laws to conduct
     their respective businesses and (iii) are in compliance with all terms and
     conditions of any such permit, license or approval, except where such
     noncompli-

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     ance with Environmental Laws, failure to have received required permits,
     licenses or other approvals or failure to comply with the terms and
     conditions of such permits, licenses or approvals would not, individually
     or in the aggregate, have a Material Adverse Effect;

         (x) the Company has reasonably concluded that the costs and liabilities
     associated with the effect of Environmental Laws on the business,
     operations and properties of the Company and its subsidiaries (including,
     without limitation, any capital or operating expenditures required for
     clean-up, closure of properties or compliance with Environmental Laws or
     any permit, license or approval, any related constraints on operating
     activities and any potential liabilities to third parties) would not,
     individually or in the aggregate, have a Material Adverse Effect;

         (y) each employee benefit plan, within the meaning of Section 3(3) of
     the Employee Retirement Income Security Act of 1974, as amended ("ERISA"),
     that is maintained, administered or contributed to by the Company or any of
     its affiliates for employees or former employees of the Company and its
     affiliates has been maintained in compliance with its terms and the
     requirements of any applicable statutes, orders, rules and regulations,
     including but not limited to ERISA and the Internal Revenue Code of 1986,
     as amended (the "CODE"), except to the extent that the failure to so comply
     would not, individually or in the aggregate, have a Material Adverse
     Effect; to the knowledge of the Company, no prohibited transaction, within
     the meaning of Section 406 of ERISA or Section 4975 of the Code, has
     occurred with respect to any such plan excluding transactions effected
     pursuant to a statutory or administrative exemption; and for each such plan
     which is subject to the funding rules of Section 412 of the Code or Section
     302 of ERISA, no "accumulated funding deficiency" as defined in Section 412
     of the Code has been incurred, whether or not waived, and the fair market
     value of the assets of each such plan (excluding for these purposes accrued
     but unpaid contributions) exceeded the present value of all benefits
     accrued under such plan determined using reasonable actuarial assumptions;

         (z) the statistical and market-related data included in the
     Registration Statement and the Prospectus are based on or derived from
     sources which are believed by the Company to be reliable;

         (aa) to the knowledge of the Company, each of the Company and its
     subsidiaries owns, is licensed to use or otherwise possesses adequate
     rights to use the patents, patent rights, licenses, inventions, trademarks,
     service marks, trade names, copyrights and know-how, including trade
     secrets and other unpatented and/or unpatentable proprietary or
     confidential information, systems, processes or procedures (collectively,
     the "INTELLECTUAL PROPERTY"), reasonably necessary to carry on the business
     conducted by it, except to the extent that the failure to own, be licensed
     to use or otherwise pos-

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     sess adequate rights to use such Intellectual Property would not have a
     Material Adverse Effect; the Company has not received any notice of
     infringement of or conflict with, and the Company has no knowledge of any
     infringement of or conflict with, asserted rights of others with respect to
     its Intellectual Property which could reasonably be expected to result in a
     Material Adverse Effect; the discoveries, inventions, products or processes
     of the Company referred to in the Registration Statement and the Prospectus
     do not, to the knowledge of the Company, infringe or conflict with any
     right or patent of any third party, or any discovery, invention, product or
     process which is the subject of a patent application filed by any third
     party; except as described in the Prospectus, the Company is not obligated
     to pay a royalty, grant a license or provide other consideration to any
     third party in connection with its patents, patent rights, licenses,
     inventions, trademarks, service marks, trade names, copyrights and
     know-how; and no third party, including any academic or governmental
     organization, possesses rights to the Intellectual Property which, if
     exercised, could enable such third party to develop products competitive
     with those of the Company or its subsidiaries or could reasonably be
     expected to have a Material Adverse Effect;

         (bb) since the respective dates as of which information is given in the
     Registration Statement and the Prospectus, the studies, tests and
     preclinical and clinical trials conducted by or on behalf of the Company
     that are described in the Registration Statement and the Prospectus were
     and, if still pending, are being conducted in accordance with experimental
     protocols, procedures and controls pursuant to, where applicable, accepted
     professional scientific standards; the descriptions of the results of such
     studies, tests and trials contained in the Registration Statement and the
     Prospectus are accurate and complete in all material respects; and the
     Company has not received any notices or correspondence from the FDA or any
     foreign, state or local governmental body exercising comparable authority
     requiring the termination, suspension or material modification of any
     studies, tests or preclinical or clinical trials conducted by or on behalf
     of the Company which termination, suspension or material modification could
     reasonably be expected to have a Material Adverse Effect; and

         (cc) The Year 2000 Problem has not had, and the Company has no reason
     to believe, and does not believe, that the Year 2000 Problem will have, a
     Material Adverse Effect or result in any material loss or interference with
     the Company's business or operations. The "Year 2000 Problem" as used
     herein means any significant risk that computer hardware or software used
     in the receipt, transmission, processing, manipulation, storage, retrieval,
     retransmission or other utilization of data or in the operation of
     mechanical or electrical systems of any kind will not, in the case of dates
     or time periods occurring after December 31, 1999, function at least as
     effectively as in the case of dates or time periods occurring prior to
     January 1, 2000.

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         5. The Company covenants and agrees with each of the several
Underwriters as follows:

         (a) to use its best efforts to cause the Registration Statement to
     become effective at the earliest possible time (if it has not already
     become effective) and, if required, to file the final Prospectus with the
     Commission within the time periods specified by Rule 424(b) and Rule 430A
     under the Securities Act and to furnish copies of the Prospectus to the
     Underwriters in New York City prior to 10:00 a.m., New York City time, on
     the Business Day next succeeding the date of this Agreement in such
     quantities as the Representatives may reasonably request;

         (b) to deliver, at the expense of the Company, to the Representatives
     four signed copies of the Registration Statement (as originally filed) and
     each amendment thereto, in each case including exhibits, and to each other
     Underwriter a conformed copy of the Registration Statement (as originally
     filed) and each amendment thereto, in each case without exhibits, and,
     during the period mentioned in paragraph (e) below, to each of the
     Underwriters as many copies of the Prospectus (including all amendments and
     supplements thereto) as the Representatives may reasonably request;

         (c) before filing any amendment or supplement to the Registration
     Statement or the Prospectus, whether before or after the time the
     Registration Statement becomes effective, to furnish to the Representatives
     a copy of the proposed amendment or supplement for review and not to file
     any such proposed amendment or supplement to which the Representatives
     reasonably object;

         (d) to advise the Representatives promptly, and to confirm such advice
     in writing (i) when the Registration Statement has become effective, (ii)
     when any amendment to the Registration Statement has been filed or becomes
     effective, (iii) when any supplement to the Prospectus or any amended
     Prospectus has been filed and to furnish the Representatives with copies
     thereof, (iv) of any request by the Commission for any amendment to the
     Registration Statement or any amendment or supplement to the Prospectus or
     for any additional information, (v) of the issuance by the Commission of
     any stop order suspending the effectiveness of the Registration Statement
     or of any order preventing or suspending the use of any preliminary
     prospectus or the Prospectus or the initiation or threatening of any
     proceeding for that purpose, (vi) of the occurrence of any event, within
     the period referenced in paragraph (e) below, as a result of which the
     Prospectus as then amended or supplemented would include an untrue
     statement of a material fact or omit to state any material fact necessary
     in order to make the statements therein, in the light of the circumstances
     when the Prospectus is delivered to a purchaser, not misleading, and (vii)
     of the receipt by the Company of any notification with respect to any
     suspension of the qualification of the Shares for offer and sale in any
     jurisdiction or the initiation or threatening of any proceeding for

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     such purpose; and to use its best efforts to prevent the issuance of any
     such stop order, or of any order preventing or suspending the use of any
     preliminary prospectus or the Prospectus, or of any order suspending any
     such qualification of the Shares, or notification of any such order thereof
     and, if issued, to obtain as soon as possible the withdrawal thereof;

         (e) if, during such period of time after the first date of the public
     offering of the Shares as in the opinion of counsel for the Underwriters a
     prospectus relating to the Shares is required by law to be delivered in
     connection with sales by the Underwriters or any dealer, any event shall
     occur as a result of which it is necessary to amend or supplement the
     Prospectus in order to make the statements therein, in the light of the
     circumstances when the Prospectus is delivered to a purchaser, not
     misleading, or if it is necessary to amend or supplement the Prospectus to
     comply with law, forthwith to prepare and furnish upon request, at the
     expense of the Company, to the Underwriters and to the dealers (whose names
     and addresses the Representatives will furnish to the Company) to which
     Shares may have been sold by the Representatives on behalf of the
     Underwriters and to any other dealers, such amendments or supplements to
     the Prospectus as may be necessary so that the statements in the Prospectus
     as so amended or supplemented will not, in the light of the circumstances
     when the Prospectus is delivered to a purchaser, be misleading or so that
     the Prospectus will comply with law;

         (f) to endeavor to qualify the Shares for offer and sale under the
     securities or Blue Sky laws of such jurisdictions as the Representatives
     shall reasonably request and to continue such qualification in effect so
     long as reasonably required for distribution of the Shares; provided that
     the Company shall not be required to file a general consent to service of
     process in any such jurisdiction;

         (g) to make generally available to its security holders and to the
     Representatives as soon as practicable an earnings statement covering a
     period of at least twelve months beginning with the first fiscal quarter of
     the Company occurring after the effective date of the Registration
     Statement, which shall satisfy the provisions of Section 11(a) of the
     Securities Act and Rule 158 of the Commission promulgated thereunder;

         (h) for three years from the date of the Prospectus, to furnish to the
     Representatives copies of all reports or other communications (financial or
     other) furnished to holders of the Shares, and copies of any reports and
     financial statements furnished to or filed with the Commission or any
     national securities exchange;

         (i) for a period of 90 days after the date of the Prospectus not to (i)
     offer, pledge, announce the intention to sell, sell, contract to sell, sell
     any option or contract

<PAGE>   13
                                      -13-

     to purchase, purchase any option or contract to sell, grant any option,
     right or warrant to purchase, or otherwise transfer or dispose of, directly
     or indirectly, any shares of Class A Common Stock or any securities of the
     Company which are substantially similar to the Class A Common Stock or any
     securities convertible into or exercisable or exchangeable for Class A
     Common Stock or (ii) enter into any swap, option, future, forward or other
     agreement that transfers, in whole or in part, any of the economic
     consequences of ownership of the Class A Common Stock or any securities of
     the Company which are substantially similar to the Class A Common Stock,
     including, but not limited to, any security convertible into or exercisable
     or exchangeable for Class A Common Stock, whether any such transaction
     described in clause (i) or (ii) above is to be settled by delivery of Class
     A Common Stock or such other securities, in cash or otherwise, without the
     prior written consent of J.P. Morgan Securities Inc., other than, in the
     case of either clause (i) or (ii), the Shares to be sold by the Company
     hereunder or Class A Common Stock or any securities of the Company
     substantially similar to the Class A Common Stock issued pursuant to (x)
     employee stock option and restricted stock plans existing on the date of
     the Prospectus, (y) an employment agreement with any person who is not
     currently an employee of the Company provided that any such person delivers
     to the Underwriters an executed lock-up agreement substantially in the form
     of Exhibit A hereto or (z) warrants to purchase Class A Common Stock
     existing on the date of the Prospectus);

         (j) to use its best efforts to list, subject to notice of issuance, the
     Shares on the Nasdaq National Market (the "NASDAQ NATIONAL MARKET");

         (k) to file with the Commission such reports as may be required by Rule
     463 under the Securities Act; and

         (l) whether or not the transactions contemplated herein are consummated
     or this Agreement is terminated, to pay or cause to be paid all costs and
     expenses incident to the performance of its obligations hereunder,
     including without limiting the generality of the foregoing, all costs and
     expenses (i) incident to the preparation, issuance, execution and delivery
     of the Shares, (ii) incident to the preparation, printing and filing under
     the Securities Act of the Registration Statement, the Prospectus and any
     preliminary prospectus (including in each case all exhibits, amendments and
     supplements thereto), (iii) incurred in connection with the registration or
     qualification of the Shares under the laws of such jurisdictions as the
     Representatives may designate (including fees of counsel for the
     Underwriters and its disbursements), (iv) in connection with the listing of
     the Shares on the Nasdaq National Market, (v) related to the filing with,
     and clearance of the offering by, the National Association of Securities
     Dealers, Inc., (vi) in connection with the furnishing to the Underwriters
     and dealers of copies of the Registration Statement and the Prospectus,
     including mailing and shipping, as herein provided, (vii) any expenses
     incurred by the Company in connection with a

<PAGE>   14
                                      -14-

     "road show" presentation to potential investors, (viii) the cost of
     preparing stock certificates and (ix) the cost and charges of any transfer
     agent and any registrar.

         6. The several obligations of the Underwriters hereunder to purchase
the Shares on the Closing Date or the Additional Closing Date, as the case may
be, are subject to the performance by the Company of its obligations hereunder
and to the following additional conditions:

         (a) the Registration Statement shall have become effective (or if a
     post-effective amendment is required to be filed under the Securities Act,
     such post-effective amendment shall have become effective) not later than
     5:00 P.M., New York City time, on the date hereof; and no stop order
     suspending the effectiveness of the Registration Statement or any
     post-effective amendment shall be in effect, and no proceedings for such
     purpose shall be pending before or threatened by the Commission; the
     Prospectus shall have been filed with the Commission pursuant to Rule
     424(b) within the applicable time period prescribed for such filing by the
     rules and regulations under the Securities Act and in accordance with
     Section 5(a) hereof; and all requests for additional information shall have
     been complied with to the satisfaction of the Representatives;

         (b) the representations and warranties of the Company contained herein
     are true and correct on and as of the Closing Date or the Additional
     Closing Date, as the case may be, as if made on and as of the Closing Date
     or the Additional Closing Date, as the case may be, and the Company shall
     have complied with all agreements and all conditions on its part to be
     performed or satisfied hereunder at or prior to the Closing Date or the
     Additional Closing Date, as the case may be;

         (c) subsequent to the execution and delivery of this Agreement and
     prior to the Closing Date or the Additional Closing Date, as the case may
     be, there shall not have occurred any downgrading, nor shall any notice
     have been given of (i) any downgrading, (ii) any intended or potential
     downgrading or (iii) any review or possible change that does not indicate
     an improvement, in the rating accorded any securities of or guaranteed by
     the Company by any "nationally recognized statistical rating organization,"
     as such term is defined for purposes of Rule 436(g)(2) under the Securities
     Act;

         (d) since the respective dates as of which information is given in the
     Prospectus there shall not have been any change in the capital stock or
     long-term debt of the Company or any of its subsidiaries or any Material
     Adverse Change otherwise than as set forth or contemplated in the
     Prospectus, the effect of which in the judgment of the Representatives
     makes it impracticable or inadvisable to proceed with the public offering
     or the delivery of the Shares on the Closing Date or the Additional Closing

<PAGE>   15
                                      -15-

     Date, as the case may be, on the terms and in the manner contemplated in
     the Prospectus; and neither the Company nor any of its subsidiaries has
     sustained since the date of the latest audited financial statements
     included in the Prospectus any material loss or interference with its
     business from fire, explosion, flood or other calamity, whether or not
     covered by insurance, or from any labor dispute or court or governmental
     action, order or decree, otherwise than as set forth or contemplated in the
     Prospectus;

          (e) the Representatives shall have received on and as of the Closing
     Date or the Additional Closing Date, as the case may be, a certificate of
     an executive officer of the Company, with specific knowledge about the
     Company's financial matters, reasonably satisfactory to the Representatives
     to the effect set forth in subsections (a) through (d) (with respect to the
     respective representations, warranties, agreements and conditions of the
     Company) of this Section 6;

          (f) LeBoeuf, Lamb, Greene & MacRae, L.L.P., counsel for the Company,
     shall have furnished to the Representatives their written opinion, dated
     the Closing Date or the Additional Closing Date, as the case may be, in
     form and substance satisfactory to the Representatives, to the effect that:

               (i) the Company has been duly incorporated and is validly
          existing as a corporation in good standing under the laws of the State
          of Delaware, with requisite corporate power to own its properties and
          conduct its business as described in the Prospectus;

               (ii) the Company has been duly qualified as a foreign corporation
          for the transaction of business and is in good standing under the laws
          of Massachusetts, New Hampshire and Pennsylvania;

               (iii) this Agreement has been duly authorized, executed and
          delivered by the Company;

               (iv) the authorized capital stock of the Company conforms as to
          legal matters to the description thereof contained in the Prospectus;

               (v) the shares of capital stock of the Company outstanding prior
          to the issuance of the Shares to be sold by the Company have been duly
          authorized and are validly issued, fully paid and non-assessable;

               (vi) the Shares to be issued and sold by the Company hereunder
          have been duly authorized and, when delivered to and paid for the
          Underwriters in accordance with the terms of this Agreement, will be
          validly issued, fully paid

<PAGE>   16
                                      -16-

          and non-assessable and except as described in the Prospectus the
          issuance of the Shares is not subject to any preemptive rights;

               (vii) the statements in the Prospectus under "Management--The
          1998 Stock Option Plan," "Management--1999 Omnibus Securities and
          Incentive Plan" and "Description of Capital Stock," and in the
          Registration Statement in Items 14 and 15, insofar as such statements
          constitute a summary of the terms of the capital stock of the Company,
          legal matters, documents or proceedings referred to therein, fairly
          present the information called for with respect to such terms, legal
          matters, documents or proceedings;

               (viii) such counsel is of the opinion that the Registration
          Statement and the Prospectus and any amendments and supplements
          thereto (other than the financial statements and related schedules and
          financial, accounting and statistical data therein, as to which such
          counsel need express no opinion) comply as to form in all material
          respects with the requirements of the Securities Act and believes that
          (other than the financial statements and related schedules and
          financial, accounting and statistical data therein, as to which such
          counsel need express no belief) the Registration Statement and the
          Prospectus included therein at the time the Registration Statement
          became effective did not contain any 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 not misleading, and that the
          Prospectus, as amended or supplemented, if applicable, does not
          contain any untrue statement of a material fact or omit to state a
          material fact necessary in order to make the statements therein, in
          the light of the circumstances under which they were made, not
          misleading;

               (ix) the issue and sale of the Shares being delivered on the
          Closing Date or the Additional Closing Date, as the case may be, and
          the performance by the Company of its obligations hereunder and the
          consummation of the transactions contemplated herein will not conflict
          with or result in a breach or violation of any of the terms or
          provisions of, or constitute a default under, any indenture, mortgage,
          deed of trust, loan agreement or other agreement or instrument
          included as an exhibit to the Registration Statement to which the
          Company or any of its subsidiaries is a party or by which the Company
          or any of its subsidiaries is bound or to which any of the property or
          assets of the Company or any of its subsidiaries is subject, nor will
          any such action result in any violation of the provisions of the
          certificate of incorporation or by-laws of the Company or, assuming
          compliance with state securities laws, any applicable law or statute
          of the State of New York, any federal law of the United States or the
          General Corporation Law of the State of Delaware or any order,

<PAGE>   17
                                      -17-

          rule or regulation of any federal or State of New York court or
          governmental agency or body;

               (x) no consent, approval, authorization, order, license,
          registration or qualification of or with any court or governmental
          agency or body is required for the issue and sale of the Shares in the
          United States, except such consents, approvals, authorizations,
          orders, licenses, registrations or qualifications as have been
          obtained or made under the Securities Act and as may be required under
          state securities or Blue Sky laws in connection with the purchase and
          distribution of the Shares by the Underwriters; and

               (xi) the Company is not and, after giving effect to the offering
          and sale of the Shares, will not be an "investment company" or entity
          "controlled" by an "investment company," as such terms are defined in
          the Investment Company Act.

          In rendering such opinions, such counsel may rely (A) as to matters
     involving the application of laws other than the laws of the United States
     and the States of New York and Delaware, to the extent such counsel deems
     proper and to the extent specified in such opinion, if at all, upon an
     opinion or opinions (in form and substance reasonably satisfactory to the
     Underwriters' counsel) of other counsel reasonably acceptable to the
     Underwriters' counsel, familiar with the applicable laws and (B) as to
     matters of fact, to the extent such counsel deems proper, on certificates
     of responsible officers of the Company and certificates or other written
     statements of officials of jurisdictions having custody of documents
     respecting the corporate existence or good standing of the Company. The
     opinion of such counsel for the Company shall state that the opinion of any
     such other counsel upon which they relied is in form satisfactory to such
     counsel and, in such counsel's opinion, the Underwriters and they are
     justified in relying thereon. With respect to the matters to be covered in
     subparagraph (viii) above counsel may state their opinion and belief is
     based upon their participation in the preparation of the Registration
     Statement and the Prospectus and any amendment or supplement thereto and
     review and discussion of the contents thereof but is without independent
     check or verification except as specified.

          The opinion of LeBoeuf, Lamb, Greene & MacRae, L.L.P., described above
     shall be rendered to the Underwriters at the request of the Company and
     shall so state therein;

          (g) Jane Kober, Esq., general counsel for the Company, shall have
     furnished to the Representatives her written opinion, dated the Closing
     Date or the Additional Closing Date, as the case may be, in form and
     substance satisfactory to the Representatives, to the effect that:

<PAGE>   18
                                      -18-

               (i) each of the Company's U.S. subsidiaries has been duly
          incorporated and is validly existing as a corporation under the laws
          of its jurisdiction of incorporation with power and authority
          (corporate and other) to own its properties and conduct its business
          as described in the Prospectus and has been duly qualified as a
          foreign corporation for the transaction of business and is in good
          standing under the laws of each other jurisdiction in which it owns or
          leases properties, or conducts any business, so as to require such
          qualification, other than where the failure to be so qualified and in
          good standing would not have a Material Adverse Effect; and all of the
          outstanding shares of capital stock of each subsidiary have been duly
          and validly authorized and issued, are fully paid and non-assessable,
          and all of the outstanding shares of capital stock of each subsidiary
          of the Company owned by the Company are owned, directly or indirectly,
          free and clear of all liens, encumbrances, security interests and
          claims;

               (ii) other than as set forth or contemplated in the Prospectus,
          there are no legal or governmental investigations, actions, suits or
          proceedings pending or, to the knowledge of such counsel, threatened
          against or affecting the Company or any of its subsidiaries or any of
          their respective properties or to which the Company or any of its
          subsidiaries is or may be a party or to which any property of the
          Company or its subsidiaries is or may be the subject which, if
          determined adversely to the Company or any of its subsidiaries, could,
          individually or in the aggregate, reasonably be expected to have, a
          Material Adverse Effect; to the knowledge of such counsel, no such
          proceedings are threatened or contemplated by governmental authorities
          or threatened by others;

               (iii) there are no statutes, regulations, contracts or other
          documents or legal or governmental investigations, actions, suits or
          proceedings pending or, to the knowledge of such counsel, threatened
          that are required to be described in the Registration Statement or the
          Prospectus or to be filed as exhibits to the Registration Statement,
          as the case may be, that are not described or filed as required;

               (iv) such counsel believes that (other than the financial
          statements and related schedules and financial, accounting and
          statistical data therein, as to which such counsel need express no
          belief) the Registration Statement and the Prospectus included therein
          at the time the Registration Statement became effective did not
          contain any 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 not misleading, and that the Prospectus, as amended
          or supplemented, if applicable, does not contain any untrue statement
          of a material fact or omit to

<PAGE>   19
                                      -19-

          state a material fact necessary in order to make the statements
          therein, in the light of the circumstances under which they were made,
          not misleading;

               (v) neither the Company nor any of its subsidiaries is, or with
          the giving of notice or lapse of time or both would be, in violation
          of or in default under its certificate of incorporation or by-laws or
          any material indenture, mortgage, deed of trust, loan agreement or
          other material agreement or instrument known to such counsel to which
          the Company or any of its subsidiaries is a party or by which it or
          any of them or any of their respective properties is bound, except for
          violations and defaults which would not, individually or in the
          aggregate, have a Material Adverse Effect;

               (vi) each of the Company and its subsidiaries owns, possesses or
          has obtained all licenses, permits, certificates, consents, orders,
          approvals and other authorizations from, and has made all declarations
          and filings with, all federal, state, local and other governmental
          authorities (including foreign regulatory agencies), all
          self-regulatory organizations and all courts and other tribunals,
          domestic or foreign, necessary to own or lease, as the case may be,
          and to operate its properties and to carry on its business as
          conducted as of the date hereof except where the failure to own,
          possess, obtain or make would not, individually or in the aggregate,
          have a Material Adverse Effect, and neither the Company nor any such
          subsidiary has received any actual notice of any proceeding relating
          to revocation or modification of any such license, permit,
          certificate, consent, order, approval or other authorization, except
          as described in the Registration Statement and the Prospectus; and
          each of the Company and its subsidiaries is in compliance with all
          laws and regulations relating to the conduct of its business as
          conducted as of the date of the Prospectus;

               (vii) to the knowledge of such counsel, each of the Company and
          its subsidiaries owns, possesses or has the right to use the
          Intellectual Property employed by it in connection with the business
          conducted by it as of the date hereof;

               (viii) to the knowledge of such counsel, each of the Company and
          its subsidiaries is in compliance with all Environmental Laws, except,
          in each case, where noncompliance would not, individually or in the
          aggregate, have a Material Adverse Effect; there are no legal or
          governmental proceedings pending or, to the knowledge of such counsel,
          threatened against or affecting the Company or any of its subsidiaries
          under any Environmental Law which, individually or in the aggregate,
          could reasonably be expected to have a Material Adverse Effect; and

<PAGE>   20
                                      -20-

               (ix) to the knowledge of such counsel, the Company has not
          received any notices or correspondence from the FDA or any foreign,
          state or local governmental body exercising comparable authority
          requiring the termination, suspension or material modification of any
          studies, tests or preclinical or clinical trials conducted by or on
          behalf of the Company which termination, suspension or material
          modification could reasonably be expected to have a Material Adverse
          Effect.

          In rendering such opinions, such counsel may rely (A) as to matters
     involving the application of laws other than the laws of the United States
     and the States of New York and Delaware, to the extent such counsel deems
     proper and to the extent specified in such opinion, if at all, upon an
     opinion or opinions (in form and substance reasonably satisfactory to the
     Underwriters' counsel) of other counsel reasonably acceptable to the
     Underwriters' counsel, familiar with the applicable laws and (B) as to
     matters of fact, to the extent such counsel deems proper, on certificates
     of responsible officers of the Company and certificates or other written
     statements of officials of jurisdictions having custody of documents
     respecting the corporate existence or good standing of the Company. The
     opinion of such general counsel for the Company shall state that the
     opinion of any such other counsel upon which they relied is in form
     satisfactory to such counsel and, in such counsel's opinion, the
     Underwriters and they are justified in relying thereon. With respect to the
     matters to be covered in subparagraph (iv) above counsel may state their
     opinion and belief is based upon their participation in the preparation of
     the Registration Statement and the Prospectus and any amendment or
     supplement thereto and review and discussion of the contents thereof but is
     without independent check or verification except as specified.

          The opinion of Jane Kober, Esq., described above shall be rendered to
     the Underwriters at the request of the Company and shall so state therein;

          (h) Hamilton, Brook, Smith & Reynolds, P.C., patent counsel for the
     Company, shall have furnished to the Representatives their written opinion,
     dated the Closing Date or the Additional Closing Date, as the case may be,
     in form and substance satisfactory to the Representatives, to the effect
     that:

               (i) such counsel is of the opinion that the statements in the
          Registration Statement and the Prospectus included therein at the time
          the Registration Statement became effective set forth under "Risk
          Factors- If We Are Not Able to Protect Our Intellectual Property,
          Competition Could Force Us to Lower Our Prices, Which Might Reduce
          Profitability" and "Business--Intellectual Property," insofar as such
          statements concern patents, patent applications and patent rights, did
          not contain any 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 not misleading, and that the statements in the
          captions set forth above

<PAGE>   21
                                      -21-

          in the Prospectus, as amended or supplemented, if applicable, did not
          contain any untrue statement of a material fact or omit to state a
          material fact necessary in order to make the statements therein, in
          the light of the circumstances under which they were made, not
          misleading;

               (ii) to the knowledge of such counsel, each of the Company and
          its subsidiaries owns, is licensed to use or otherwise possesses
          adequate rights to use the patents and patent rights reasonably
          necessary to carry on the business conducted by it, except to the
          extent that the failure to own, be licensed to use or otherwise
          possess adequate rights to use such Intellectual Property would not
          have a Material Adverse Effect;

               (iii) to the knowledge of such counsel, the Company has not
          received any notice of infringement of or conflict with, and such
          counsel has no knowledge of any infringement of or conflict with,
          asserted rights of others with respect to its patents or patent rights
          which could reasonably be expected to result in a Material Adverse
          Effect;

               (iv) the discoveries, inventions, products or processes of the
          Company referred to in the Registration Statement and the Prospectus
          do not, to the knowledge of such counsel, infringe or conflict with
          any patents or patent rights of any third party, or any discovery,
          invention, product or process which is the subject of a patent
          application filed by any third party; and

               (v) to the knowledge of such counsel, no third party, including
          any academic or governmental organization, possesses rights to the
          Company's patents, patent applications or patent rights which, if
          exercised, could enable such third party to develop products
          competitive with those of the Company or its subsidiaries or could
          reasonably be expected to have a Material Adverse Effect.

          In rendering such opinions, such counsel may rely (A) as to matters
     involving the application of laws other than the laws of the United States
     and the State of Massachusetts, to the extent such counsel deems proper and
     to the extent specified in such opinion, if at all, upon an opinion or
     opinions (in form and substance reasonably satisfactory to the
     Underwriters' counsel) of other counsel reasonably acceptable to the
     Underwriters' counsel, familiar with the applicable laws and (B) as to
     matters of fact, to the extent such counsel deems proper, on certificates
     of responsible officers of the Company. The opinion of such patent counsel
     for the Company shall state that the opinion of any such other counsel upon
     which they relied is in form satisfactory to such counsel and, in such
     counsel's opinion, the Underwriters and they are justified in relying
     thereon.

<PAGE>   22
                                      -22-

          The opinion of Hamilton, Brook, Smith & Reynolds, P.C., described
     above shall be rendered to the Underwriters at the request of the Company
     and shall so state therein;

          (i) Hogan & Hartson L.L.P., regulatory counsel for the Company, shall
     have furnished to the Representatives their written opinion, dated the
     Closing Date or the Additional Closing Date, as the case may be, in form
     and substance satisfactory to the Representatives, to the effect that such
     counsel is of the opinion that the statements in the Registration Statement
     and the Prospectus included therein at the time the Registration Statement
     became effective set forth under "Risk Factors-- If We Fail to Obtain FDA
     Approval, We Cannot Market Hemopure in the United States," "-- We Cannot
     Expand Indications for Our Products Unless We Receive FDA Approval for each
     Proposed Indication," "-- Stringent, Ongoing Government Regulation and
     Inspection of Our Products Could Lead to Delays in the Manufacture,
     Marketing and Sale of Our Products," and "Business-- Government
     Regulation," insofar as such statements summarize applicable provisions of
     the Federal Food, Drug, and Cosmetic Act, as amended, Section 351 of the
     Public Health Services Act, as amended, and the regulations promulgated
     thereunder, are accurate summaries in all material respects of the
     provisions purported to be summarized under such captions in the
     Prospectus.

          The opinion of Hogan & Hartson L.L.P. described above shall be
     rendered to the Underwriters at the request of the Company and shall so
     state therein;

          (j) on the effective date of the Registration Statement and the
     effective date of the most recently filed post-effective amendment to the
     Registration Statement and also on the Closing Date or Additional Closing
     Date, as the case may be, Ernst & Young LLP shall have furnished to you
     letters, dated the respective dates of delivery thereof, in form and
     substance satisfactory to you, containing statements and information of the
     type customarily included in accountants' "comfort letters" to underwriters
     with respect to the financial statements and certain financial information
     contained in the Registration Statement and the Prospectus;

          (k) the Representatives shall have received on and as of the Closing
     Date or Additional Closing Date, as the case may be, an opinion of Cahill
     Gordon & Reindel, counsel to the Underwriters, with respect to the due
     authorization and valid issuance of the Shares, the Registration Statement,
     the Prospectus and other related matters as the Representatives may
     reasonably request, and such counsel shall have received such papers and
     information as they may reasonably request to enable them to pass upon such
     matters;

<PAGE>   23
                                      -23-

          (l) the Shares to be delivered on the Closing Date or Additional
     Closing Date, as the case may be, shall have been approved for listing on
     the Nasdaq National Market, subject to official notice of issuance;

          (m) on or prior to the Closing Date or Additional Closing Date, as the
     case may be, the Company shall have furnished to the Representatives such
     further certificates and documents as the Representatives shall reasonably
     request; and

          (n) the "lock-up" agreements, each substantially in the form of
     Exhibit A hereto, between you and certain stockholders of the Company
     previously specified by the Representatives relating to sales and certain
     other dispositions of shares of Class A Common Stock or certain other
     securities, delivered to you on or before the date hereof, shall be in full
     force and effect on the Closing Date or Additional Closing Date, as the
     case may be.

         7. The Company agrees to indemnify and hold harmless each Underwriter,
each affiliate of any Underwriter which assists such Underwriter in the
distribution of the Shares and each person, if any, who controls any Underwriter
within the meaning of either Section 15 of the Securities Act or Section 20 of
the Securities Exchange Act of 1934, as amended (the "EXCHANGE ACT"), from and
against any and all losses, claims, damages and liabilities (including, without
limitation, reasonable legal fees and other expenses incurred in connection with
any suit, action or proceeding or any claim asserted) caused by any untrue
statement or alleged untrue statement of a material fact contained in the
Registration Statement or the Prospectus (as amended or supplemented if the
Company shall have furnished any amendments or supplements thereto) or any
preliminary prospectus, or caused by any omission or alleged omission to state
therein a material fact required to be stated therein or necessary to make the
statements therein not misleading, except insofar as such losses, claims,
damages or liabilities are caused by any untrue statement or omission or alleged
untrue statement or omission made in reliance upon and in conformity with
information relating to any Underwriter furnished to the Company in writing by
such Underwriter through the Representatives expressly for use therein;
provided, however, that the foregoing indemnity with respect to any preliminary
prospectus shall not inure to the benefit of any Underwriter from whom the
person asserting any such losses, claims, damages or liabilities purchased
Shares, or any person controlling such Underwriter, if a copy of the Prospectus
(as then amended or supplemented if the Company shall have furnished any
amendments or supplements thereto) was not sent or given by or on behalf of such
Underwriter to such person, if required by laws to have been delivered, at or
prior to the written confirmation of the sale of the Shares to such person, and
if the Prospectus (as so amended or supplemented) would have cured the defect
giving rise to such losses, claims, damages or liabilities.

         Each Underwriter agrees, severally and not jointly, to indemnify and
hold harmless the Company, its directors, its officers who sign the Registration
Statement and each

<PAGE>   24
                                      -24-

person who controls the Company within the meaning of Section 15 of the
Securities Act or Section 20 of the Exchange Act to the same extent as the
foregoing indemnity from the Company to each Underwriter, but only with
reference to information relating to such Underwriter furnished to the Company
in writing by such Underwriter through the Representatives expressly for use in
the Registration Statement, the Prospectus, any amendment or supplement thereto,
or any preliminary prospectus.

         If any suit, action, proceeding (including any governmental or
regulatory investigation), claim or demand shall be brought or asserted against
any person in respect of which indemnity may be sought pursuant to either of the
two preceding paragraphs, such person (the "INDEMNIFIED PERSON") shall promptly
notify the person against whom such indemnity may be sought (the "INDEMNIFYING
PERSON") in writing, and the Indemnifying Person, upon request of the
Indemnified Person, shall retain counsel reasonably satisfactory to the
Indemnified Person to represent the Indemnified Person and any others the
Indemnifying Person may designate in such proceeding and shall pay the fees and
expenses of such counsel related to such proceeding. In any such proceeding, any
Indemnified Person shall have the right to retain its own counsel, but the fees
and expenses of such counsel shall be at the expense of such Indemnified Person
unless (i) the Indemnifying Person and the Indemnified Person shall have
mutually agreed to the contrary, (ii) the Indemnifying Person has failed within
a reasonable time to retain counsel reasonably satisfactory to the Indemnified
Person or (iii) the named parties in any such proceeding (including any
impleaded parties) include both the Indemnifying Person and the Indemnified
Person and representation of both parties by the same counsel would be
inappropriate due to actual or potential differing interests between them. It is
understood that the Indemnifying Person shall not, in connection with any
proceeding or related proceeding in the same jurisdiction, be liable for the
fees and expenses of more than one separate firm (in addition to one local
counsel in any single jurisdiction) for all Indemnified Persons, and that all
such fees and expenses shall be reimbursed as they are incurred. Any such
separate firm for the Underwriters, each affiliate of any Underwriter which
assists such Underwriter in the distribution of the Shares and such control
persons of Underwriters shall be designated in writing by J.P. Morgan Securities
Inc. and any such separate firm for the Company, its directors, its officers who
sign the Registration Statement and such control persons of the Company shall be
designated in writing by the Company. The Indemnifying Person shall not be
liable for any settlement of any proceeding effected without its written
consent, but if settled with such consent or if there be a final judgment for
the plaintiff, the Indemnifying Person agrees to indemnify any Indemnified
Person from and against any loss or liability by reason of such settlement or
judgment. Notwithstanding the foregoing sentence, if at any time an Indemnified
Person shall have requested an Indemnifying Person to reimburse the Indemnified
Person for reasonable fees and expenses of counsel as contemplated by the second
and third sentences of this paragraph, the Indemnifying Person agrees that it
shall be liable for any settlement of any proceeding effected without its
written consent if (i) such settlement is entered into more than 45 days after
receipt by such Indemnifying Person of the aforesaid request and (ii) such
Indemnifying Person shall not have reimbursed the Indemnified Person in

<PAGE>   25
                                      -25-

accordance with such request prior to the date of such settlement. No
Indemnifying Person shall, without the prior written consent of the Indemnified
Person, effect any settlement of any pending or threatened proceeding in respect
of which any Indemnified Person is or could have been a party and indemnity
could have been sought hereunder by such Indemnified Person, unless such
settlement includes an unconditional release of such Indemnified Person from all
liability on claims that are the subject matter of such proceeding.

         If the indemnification provided for in the first or second paragraph of
this Section 7 is unavailable to an Indemnified Person or insufficient in
respect of any losses, claims, damages or liabilities referred to therein, then
each Indemnifying Person under such paragraph, in lieu of indemnifying such
Indemnified Person thereunder, shall contribute to the amount paid or payable by
such Indemnified Person as a result of such losses, claims, damages or
liabilities (i) in such proportion as is appropriate to reflect the relative
benefits received by the Company on the one hand and the Underwriters on the
other hand from the offering of the Shares or (ii) if the allocation provided by
clause (i) above is not permitted by applicable law, in such proportion as is
appropriate to reflect not only the relative benefits referred to in clause (i)
above but also the relative fault of the Company on the one hand and the
Underwriters on the other hand in connection with the statements or omissions
that resulted in such losses, claims, damages or liabilities, as well as any
other relevant equitable considerations. The relative benefits received by the
Company on the one hand and the Underwriters on the other hand shall be deemed
to be in the same respective proportions as the net proceeds from the offering
(before deducting expenses) received by the Company and the total underwriting
discounts and the commissions received by the Underwriters, in each case as set
forth in the table on the cover of the Prospectus, bear to the aggregate public
offering price of the Shares. The relative fault of the Company on the one hand
and the Underwriters on the other hand shall be determined by reference to,
among other things, whether the untrue or alleged untrue statement of a material
fact or the omission or alleged omission to state a material fact relates to
information supplied by the Company or by the Underwriters and the parties'
relative intent, knowledge, access to information and opportunity to correct or
prevent such statement or omission.

         The Company and the Underwriters agree that it would not be just and
equitable if contribution pursuant to this Section 7 were determined by pro rata
allocation (even if the Underwriters were treated as one entity for such
purposes) or by any other method of allocation that does not take account of the
equitable considerations referred to in the immediately preceding paragraph. The
amount paid or payable by an Indemnified Person as a result of the losses,
claims, damages and liabilities referred to in the immediately preceding
paragraph shall be deemed to include, subject to the limitations set forth
above, any reasonable legal or other expenses incurred by such Indemnified
Person in connection with investigating or defending any such action or claim.
Notwithstanding the provisions of this Section 7, in no event shall an
Underwriter be required to contribute any amount in excess of the amount by
which the total price at which the Shares underwritten by it and distributed to
the public were offered

<PAGE>   26
                                      -26-

to the public exceeds the amount of any damages that such Underwriter has
otherwise been required to pay by reason of such untrue or alleged untrue
statement or omission or alleged omission. No person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. The Underwriters' obligations to contribute
pursuant to this Section 7 are several in proportion to the respective number of
Shares set forth opposite their names in Schedule I hereto, and not joint.

         The remedies provided for in this Section 7 are not exclusive and shall
not limit any rights or remedies which may otherwise be available to any
indemnified party at law or in equity.

         The indemnity and contribution agreements contained in this Section 7
and the representations and warranties of the Company set forth in this
Agreement shall remain operative and in full force and effect regardless of (i)
any termination of this Agreement, (ii) any investigation made by or on behalf
of any Underwriter or any person controlling any Underwriter or by or on behalf
of the Company, its officers or directors or any other person controlling the
Company and (iii) acceptance of and payment for any of the Shares.

         8. Notwithstanding anything herein contained, this Agreement (or the
obligations of the several Underwriters with respect to the Option Shares) may
be terminated in the absolute discretion of the Representatives, by notice given
to the Company, if after the execution and delivery of this Agreement and prior
to the Closing Date (or, in the case of the Option Shares, prior to the
Additional Closing Date) (i) trading generally shall have been suspended or
materially limited on or by, as the case may be, any of the New York Stock
Exchange or the American Stock Exchange or the National Association of
Securities Dealers, Inc., (ii) trading of any securities of or guaranteed by the
Company shall have been suspended on any exchange or in any over-the-counter
market, (iii) a general moratorium on commercial banking activities in New York
shall have been declared by either Federal or New York State authorities or (iv)
there shall have occurred any outbreak or escalation of hostilities or any
change in financial markets or any calamity or crisis that, in the judgment of
the Representatives, is material and adverse and which, in the judgment of the
Representatives, makes it impracticable to market the Shares being delivered at
the Closing Date or the Additional Closing Date, as the case may be, on the
terms and in the manner contemplated in the Prospectus.

         9. This Agreement shall become effective upon the later of (x)
execution and delivery hereof by the parties hereto and (y) release of
notification of the effectiveness of the Registration Statement by the
Commission.

         If on the Closing Date or the Additional Closing Date, as the case may
be, any one or more of the Underwriters shall fail or refuse to purchase Shares
which it or they have agreed to purchase hereunder on such date, and the
aggregate number of Shares which such

<PAGE>   27
                                      -27-

defaulting Underwriter or Underwriters agreed but failed or refused to purchase
is not more than one-tenth of the aggregate number of Shares to be purchased on
such date, the other Underwriters shall be obligated severally, in the
proportions that the number of Shares set forth opposite their respective names
in Schedule I bears to the aggregate number of Underwritten Shares set forth
opposite the names of all such non-defaulting Underwriters, or in such other
proportions as the Representatives may specify, to purchase the Shares which
such defaulting Underwriter or Underwriters agreed but failed or refused to
purchase on such date; provided that in no event shall the number of Shares that
any Underwriter has agreed to purchase pursuant to Section 1 be increased
pursuant to this Section 9 by an amount in excess of one-ninth of such number of
Shares without the written consent of such Underwriter. If on the Closing Date
or the Additional Closing Date, as the case may be, any Underwriter or
Underwriters shall fail or refuse to purchase Shares which it or they have
agreed to purchase hereunder on such date, and the aggregate number of Shares
with respect to which such default occurs is more than one-tenth of the
aggregate number of Shares to be purchased on such date, and arrangements
satisfactory to the Representatives and the Company for the purchase of such
Shares are not made within 36 hours after such default, this Agreement (or the
obligations of the several Underwriters to purchase the Option Shares, as the
case may be) shall terminate without liability on the part of any non-defaulting
Underwriter or the Company. In the case of either the first sentence or the
second sentence of this paragraph, either you or the Company shall have the
right to postpone the Closing Date (or, in the case of the Option Shares, the
Additional Closing Date), but in no event for longer than seven days, in order
that the required changes, if any, in the Registration Statement and in the
Prospectus or in any other documents or arrangements may be effected. Any action
taken under this paragraph shall not relieve any defaulting Underwriter from
liability in respect of any default of such Underwriter under this Agreement.

         10. If this Agreement shall be terminated by the Underwriters, or any
of them, because of any failure or refusal on the part of the Company to comply
with the terms or to fulfill any of the conditions of this Agreement, or if for
any reason the Company shall be unable to perform its obligations under this
Agreement or any condition of the Underwriters' obligations cannot be fulfilled,
the Company agrees to reimburse the Underwriters or such Underwriters as have so
terminated this Agreement with respect to themselves, severally, for all
out-of-pocket expenses (including the reasonable fees and expenses of its
counsel) reasonably incurred by the Underwriter in connection with this
Agreement or the offering contemplated herein.

         11. This Agreement shall inure to the benefit of and be binding upon
the Company, the Underwriters, each affiliate of any Underwriter which assists
such Underwriter in the distribution of the Shares, any controlling persons
referred to herein and their respective successors and assigns. Nothing
expressed or mentioned in this Agreement is intended or shall be construed to
give any other person, firm or corporation any legal or equitable right, remedy
or claim under or in respect of this Agreement or any provision herein
contained. No pur-

<PAGE>   28
                                      -28-

chaser of Shares from any Underwriter shall be deemed to be a successor by
reason merely of such purchase.

         12. Any action by the Underwriters hereunder may be taken by J.P.
Morgan Securities Inc. alone on behalf of the Underwriters, and any such action
taken by J.P. Morgan Securities Inc. alone shall be binding upon the
Underwriters. All notices and other communications hereunder shall be in writing
and shall be deemed to have been duly given if mailed or transmitted by any
standard form of telecommunication. Notices to the Underwriters shall be given
to the Representatives, c/o J.P. Morgan Securities Inc., 60 Wall Street, New
York, New York 10260 (telefax: 212-648-5705), Attention: Syndicate Department,
with a copy to Cahill Gordon & Reindel, 80 Pine Street, New York, New York 10005
(telefax: 212-269-5420), Attention: Gerald S. Tanenbaum, Esq. Notices to the
Company shall be given to it at its offices at 11 Hurley Street, Cambridge,
Massachusetts 02141 (telefax: 617-234-6507), Attention: Jane Kober, Esq., with a
copy to LeBoeuf, Lamb, Greene & MacRae, L.L.P., 125 West 55th Street, New York,
New York 10019 (telefax: 212-424-8500), Attention: Lars Bang-Jensen, Esq.

         13. This Agreement may be signed in counterparts, each of which shall
be an original and all of which together shall constitute one and the same
instrument.

         14. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE
WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT GIVING EFFECT TO THE CONFLICTS
OF LAWS PROVISIONS THEREOF.

<PAGE>   29
                                      -29-

         If the foregoing is in accordance with your understanding, please sign
and return four counterparts hereof.

                                        Very truly yours,

                                        BIOPURE CORPORATION

                                        By:
                                           ------------------------------------
                                           Name:  Jane Kober
                                           Title: Senior Vice President, General
                                                  Counsel and Secretary

<PAGE>   30
                                      -30-

Accepted: March 13, 2000

J.P. MORGAN SECURITIES INC.
SALOMON SMITH BARNEY INC.
ADAMS, HARKNESS & HILL, INC.
ROBERT W. BAIRD & CO. INCORPORATED
     Acting severally on behalf
     of themselves and the
     several Underwriters listed
     in Schedule I hereto.

By:  J.P. MORGAN SECURITIES INC.
     Acting on behalf of itself and the
     several Underwriters listed in
     Schedule I hereto.

By:
   ---------------------------
   Name:  Michael J. Tiedemann
   Title: Vice President

<PAGE>   31

                                   SCHEDULE I

                                                           NUMBER OF SHARES TO
UNDERWRITER                                                    BE PURCHASED

J.P. Morgan Securities Inc..............................         900,000
Salomon Smith Barney Inc.                                        900,000
Adams, Harkness & Hill, Inc.............................         216,000
Robert W. Baird & Co. Incorporated......................         384,000
KBC Securities NV.......................................          50,000
Dain Rauscher Wessels...................................          25,000
Jackson Securities Incorporated.........................          25,000
                                                               ---------
                  Total.................................       2,500,000
                                                               =========<PAGE>   1
                                                                     EXHIBIT 4.3

                 AMENDMENT NO. 1 TO INVESTORS' RIGHTS AGREEMENT

     This AMENDMENT NO. 1 TO THE INVESTORS' RIGHTS AGREEMENT (this "Amendment
No. 1") is being entered into as of May 23, 2000 between McDATA Corporation, a
Delaware corporation (the "Company"), McDATA Holdings Corporation, a Delaware
corporation ("McDATA Holdings"), John F. McDonnell and William Wood (McDATA
Holdings, Mr. McDonnell and Mr. Wood are collectively referred to herein as the
"Investors," and each is individually referred to herein as an "Investor").

     WHEREAS, each of the Company, EMC Corporation, a Massachusetts corporation
("EMC"), and the Investors is a party to the Investors' Rights Agreement,
entered into as of October 1, 1997 (the "Investors' Rights Agreement"); and

     WHEREAS, Section 8.6 of the Investors' Rights Agreement provides that the
Investors' Rights Agreement may be amended only with the written consent of the
Company and a majority in interest of the Investors; and

     WHEREAS, the Company and each Investor has determined that it would be
desirable to amend the Investors' Rights Agreement in the manner set forth in
this Amendment No. 1;

     NOW THEREFORE, in consideration of the premises and the mutual agreements
set forth herein and in the Investors' Rights Agreement, the parties hereto
hereby agree as follows:

     1. Exhibit A to the Investors' Rights Agreement is hereby amended and
replaced in its entirety by Exhibit A hereto.

     2. The term "Agreement" in the Investors' Rights Agreement shall mean the
Investors' Rights Agreement as amended by this Amendment No. 1.

     3. This Amendment No. 1 is effective as of the date first set forth above.
All of the terms and provi-

                                       1
<PAGE>   2

sions of the Investors' Rights Agreement not amended hereby shall remain in full
force and effect and shall be otherwise unaffected hereby.

     4. This Amendment No. 1 shall be governed by and construed under the laws
of the State of Delaware applicable to contacts made and performed entirely
within the State of Delaware without giving effect to the principles of
conflicts of law thereof. This Amendment No. 1 may be executed in two or more
counterparts, each of which shall for all purposes be deemed to be an original,
and all of such counterparts shall together constitute one and the same
instrument.

                                       2

<PAGE>   3

     IN WITNESS WHEREOF, this Amendment No. 1 to the Investors' Rights
Agreement is executed under seal as of the date first set forth above.

                                            COMPANY:

                                            MCDATA CORPORATION

                                            By:  /s/ DEE J. PERRY
                                               ---------------------------------
                                               Name:  Dee J. Perry
                                               Title: Chief Financial Officer
                                                      and Vice President of
                                                      Finance and Administration

                                            INVESTORS:

                                            MCDATA HOLDINGS CORPORATION

                                            By:  /s/ PAUL T. DACIER
                                               ---------------------------------
                                               Name:  Paul T. Dacier
                                               Title:

                                                 /s/ JOHN F. MCDONNELL
                                               ---------------------------------
                                               John F. McDonnell

                                                 /s/ WILLIAM WOOD
                                               ---------------------------------
                                               William Wood

                                       3

<PAGE>   4

                                    EXHIBIT A

                                  INVESTOR LIST

CLASS A COMMON STOCK INVESTOR:

McDATA Holdings Corporation                     with a copy to:
c/o EMC Corporation                             McDATA Corporation
171 South Street                                310 Interlocken Parkway
Hopkinton, MA  01748                            Broomfield, CO 80021
Attn:  General Counsel                          Attn:  President

CLASS B COMMON STOCK INVESTOR:

John F. McDonnell
c/o McDATA Corporation
310 Interlocken Parkway
Broomfield, CO  80021

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