INSMED INC
S-1/A, EX-1.1, 2000-10-24
PHARMACEUTICAL PREPARATIONS
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                                                                     Exhibit 1.1
                                                                     -----------

                            Underwriting Agreement


                               October __, 2000

Robertson Stephens, Inc.
Banc of America Securities LLC
Prudential Securities Incorporated
As Representatives of the several Underwriters
c/o Robertson Stephens, Inc.
555 California Street, Suite 2600
San Francisco, CA  94104

Ladies and Gentlemen:

          Introductory.  Insmed Incorporated, a Virginia corporation (the
"Company"), proposes to issue and sell to the several underwriters named in
--------
Schedule A (the "Underwriters") an aggregate of 5,000,000 shares of its Common
----------       ------------
Stock, par value $.01 per share (the "Common Shares"); and the shareholders of
                                      -------------
the Company named in Schedule B and identified as principal selling shareholders
                     ----------
or other selling shareholders (the "Principal Selling Shareholders" and "Other
                                    ------------------------------       -----
Selling Shareholders" respectively and collectively, the "Selling Shareholders")
--------------------                                      --------------------
severally propose to sell to the Underwriters an aggregate of 1,000,000 Common
Shares.  The 5,000,000 Common Shares to be sold by the Company and the 1,000,000
shares of Common Shares to be sold by the Selling Shareholders are collectively
called the "Firm Shares".  In addition, the Selling Shareholders have severally
            -----------
granted to the Underwriters an option to purchase up to an additional 900,000
Common Shares, each Selling Shareholder selling up to the amount set forth
opposite such Selling Shareholder's name in Schedule B, all as provided in
                                            ----------
Section 2.  The additional 900,000 Common Shares to be sold by the Selling
Shareholders pursuant to such option are collectively called the "Option
                                                                  ------
Shares".  The Firm Shares and, if and to the extent such option is exercised,
------
the Option Shares are collectively called the "Shares".  Robertson Stephens,
                                               ------
Inc. ("Robertson Stephens"), Banc of America Securities LLC ("Bank of America")
       ------------------                                     ---------------
and Prudential Securities Incorporated ("Prudential") agreed to act as
                                         ----------
representatives of the several Underwriters (in such capacity, the
"Representatives") in connection with the offering and sale of the Shares.
----------------

          The Company has prepared and filed with the Securities and Exchange
Commission (the "Commission") a registration statement on Form S-1 (File No.
                 ----------
333-46552), which contains a form of prospectus, subject to completion, to be
used in connection with the public offering and sale of the Shares.  Each such
prospectus, subject to completion, used in connection with such public offering
is called a "preliminary prospectus".  Such registration statement, as amended,
             ----------------------
including the financial statements, exhibits and schedules thereto, in the form
in which it was declared effective by the Commission under the Securities Act of
1933 and the rules and regulations promulgated thereunder (collectively, the
"Securities Act"),
 --------------
<PAGE>

including any information deemed to be a part thereof at the time of
effectiveness pursuant to Rule 430A under the Securities Act, is called the
"Registration Statement". Any registration statement filed by the Company
 ----------------------
pursuant to Rule 462(b) under the Securities Act is called the "Rule 462(b)
                                                                -----------
Registration Statement", and from and after the date and time of filing of the
----------------------
Rule 462(b) Registration Statement the term "Registration Statement" shall
                                             ----------------------
include the Rule 462(b) Registration Statement.  Such prospectus, in the form
first used by the Underwriters to confirm sales of the Shares, is called the
"Prospectus".  All references in this Agreement to the Registration Statement,
-----------
the Rule 462(b) Registration Statement, a preliminary prospectus, the Prospectus
or any amendments or supplements to any of the foregoing, shall include any copy
thereof filed with the Commission pursuant to its Electronic Data Gathering,
Analysis and Retrieval System ("EDGAR").
                                -----

          The Company and each of the Selling Shareholders hereby confirm their
respective agreements with the Underwriters as follows:

     Section 1.  Representations and Warranties of the Company.

     A.   Representations and Warranties of the Company. The Company hereby
represents, warrants and covenants to each Underwriter as follows;

     (a)  Compliance with Registration Requirements.  The Registration Statement
and any Rule 462(b) Registration Statement have been declared effective by the
Commission under the Securities Act.  The Company has complied to the
Commission's satisfaction with all requests of the Commission for additional or
supplemental information.  No stop order suspending the effectiveness of the
Registration Statement or any Rule 462(b) Registration Statement is in effect
and no proceedings for such purpose have been instituted or are pending or, to
the best knowledge of the Company, are contemplated or threatened by the
Commission.

          Each preliminary prospectus and the Prospectus when filed complied in
all material respects with the Securities Act and, if filed by electronic
transmission pursuant to EDGAR (except as may be permitted by Regulation S-T
under the Securities Act), was identical in all material respects to the copy
thereof delivered to the Underwriters for use in connection with the offer and
sale of the Shares.  Each of the Registration Statement, any Rule 462(b)
Registration Statement and any post-effective amendment thereto, at the time it
became effective and at all subsequent times, complied and will comply in all
material respects with the Securities Act and did not and will 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.
Each preliminary prospectus, as of its date, and the Prospectus, as amended or
supplemented, as of its date and at all subsequent times through the 30th day
after the date hereof, did not and will 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.  The representations and warranties set forth in the two
immediately preceding sentences do not apply to statements in or omissions from
the Registration Statement, any Rule 462(b) Registration Statement, or any post-
effective amendment thereto, or the Prospectus, or any amendments or supplements
thereto, made in reliance upon and in conformity with information relating to
any Underwriter furnished to the Company in writing by the Representatives
expressly for use therein.  There are no contracts or other documents required
to be described

                                       2
<PAGE>

in the Prospectus or to be filed as exhibits to the Registration Statement which
have not been described or filed as required.

     (b)  Offering Materials Furnished to Underwriters.  The Company has
delivered to the Representatives three (3) complete conformed copies of the
Registration Statement and of each consent and certificate of experts filed as a
part thereof, and conformed copies of the Registration Statement (without
exhibits) and preliminary prospectuses and the Prospectus, as amended or
supplemented, in such quantities and at such places as the Representatives
reasonably requested for each of the Underwriters.

     (c)  Distribution of Offering Material By the Company.  The Company has not
distributed and will not distribute, prior to the later of the Second Closing
Date (as defined below) and the completion of the Underwriters' distribution of
the Shares, any offering material in connection with the offering and sale of
the Shares other than a preliminary prospectus, the Prospectus or the
Registration Statement.

     (d)  The Underwriting Agreement.  This Agreement has been duly authorized,
executed and delivered by, and is a valid and binding agreement of, the Company,
enforceable in accordance with its terms, except as rights to indemnification
and contribution hereunder may be limited by applicable law and except as the
enforcement hereof may be limited by bankruptcy, insolvency, reorganization,
moratorium or other similar laws relating to or affecting the rights and
remedies of creditors or by general equitable principles.

     (e)  Authorization of the Shares To Be Sold by the Company.  The Shares to
be purchased by the Underwriters from the Company have been duly authorized for
issuance and sale pursuant to this Agreement and, when issued and delivered by
the Company pursuant to this Agreement after payment by the Underwriters
pursuant to this Agreement, will be validly issued, fully paid and
nonassessable.

     (f)  Authorization of the Shares To Be Sold by the Selling Shareholders.
The Common Shares to be purchased by the Underwriters from the Selling
Shareholders, when issued, were validly issued, fully paid and nonassessable.

     (g)  No Applicable Registration or Other Similar Rights.  Other than as
described in the Prospectus, there are no persons with registration or other
similar rights to have any equity or debt securities registered for sale under
the Registration Statement or included in the offering contemplated by this
Agreement, other than the Selling Shareholders with respect to the Shares
included in the Registration Statement, and except for such rights as have been
duly waived.

     (h)  No Material Adverse Change.  Subsequent to the respective dates as of
which information is given in the Prospectus: (i) other than continuing
operating losses in such amounts and resulting from such factors as are
consistent with past practice, there has been no material adverse change, or any
development that could reasonably be expected to result in a material adverse
change, in the condition, financial or otherwise, or in the earnings, business,
operations or prospects, whether or not arising from transactions in the
ordinary course of business, of the Company and its subsidiaries, considered as
one entity (any such change or effect, where the context so requires, is called
a "Material Adverse Change" or a "Material Adverse Effect"); (ii) the Company
   -----------------------        -----------------------
and its subsidiaries, considered as one entity, have not incurred any material
liability or obligation, indirect, direct or contingent, not in the

                                       3
<PAGE>

ordinary course of business nor entered into any material transaction or
agreement not in the ordinary course of business; and (iii) there has been no
dividend or distribution of any kind declared, paid or made by the Company or,
except for dividends paid to the Company or other subsidiaries, any of its
subsidiaries on any class of capital stock or repurchase or redemption by the
Company or any of its subsidiaries of any class of capital stock.

     (i)  Independent Accountants.  Ernst & Young LLP, who have expressed their
opinion with respect to the financial statements (which term as used in this
Agreement includes the related notes thereto) filed with the Commission as a
part of the Registration Statement and included in the Prospectus, are
independent public or certified public accountants as required by the Securities
Act and the Securities Exchange Act of 1934, as amended, and the rules and
regulations promulgated thereunder (collectively, the "Exchange Act").
                                                       ------------

     (j)  Preparation of the Financial Statements.  The financial statements
filed with the Commission as a part of the Registration Statement and included
in the Prospectus present fairly the consolidated financial position of the
Company and its subsidiaries as of and at the dates indicated and the results of
their operations and cash flows for the periods specified.  Such financial
statements have been prepared in conformity with generally accepted accounting
principles as applied in the United States applied on a consistent basis
throughout the periods involved, except as may be expressly stated in the
related notes thereto.  No other financial statements or supporting schedules
are required to be included in the Registration Statement.  The financial data
set forth in the Prospectus under the captions "Summary--Summary Financial
                                                --------------------------
Data", "Selected Consolidated Financial Data" and "Capitalization" fairly
        ------------------------------------       --------------
present the information set forth therein on a basis consistent with that of the
audited financial statements contained in the Registration Statement.  The pro
forma condensed consolidated financial statements of the Company and its
subsidiaries and the related notes thereto included under the captions
"Unaudited Pro Forma Condensed Consolidated Statements of Operations" and "Notes
 -------------------------------------------------------------------------------
to the Unaudited Pro Forma Condensed Consolidated Statements of Operations"
--------------------------------------------------------------------------
present fairly the information contained therein, have been prepared in
accordance with the Commission's rules and guidelines with respect to pro forma
financial statements and have been properly presented in all material respects
on the bases described therein, and the assumptions used in the preparation
thereof are reasonable and the adjustments used therein are appropriate to give
effect to the transactions and circumstances referred to therein. No other pro
forma financial information is required to be included in the Registration
Statement pursuant to Regulation S-X promulgated by the Commission.

     (k)  Company's Accounting System.  The Company and each of its subsidiaries
maintain a system of accounting controls sufficient to provide reasonable
assurances that (i) transactions are executed in accordance with management's
general or specific authorization; (ii) transactions are recorded as necessary
to permit preparation of financial statements in conformity with generally
accepted accounting principles as applied in the United States and to maintain
accountability for assets; (iii) access to assets is permitted only in
accordance with management's general or specific authorization; and (iv) the
recorded accountability for assets is compared with existing assets at
reasonable intervals and appropriate action is taken with respect to any
differences.

     (l)  Subsidiaries of the Company.  The Company does not own or control,
directly or indirectly, any corporation, association or other entity other than
the subsidiaries listed in Exhibit 21.1 to the Registration Statement.

                                       4
<PAGE>

     (m)  Incorporation and Good Standing of the Company and its Subsidiaries.
Each of the Company and its subsidiaries has been duly organized and is validly
existing as a corporation or limited liability company, as the case may be, in
good standing under the laws of the jurisdiction in which it is organized with
full corporate power and authority to own its properties and conduct its
business as described in the prospectus, and is duly qualified to do business as
a foreign corporation and is in good standing under the laws of each
jurisdiction which requires such qualification, except where the failure to do
so would not have a Material Adverse Effect.

     (n)  Capitalization of the Subsidiaries.  All the outstanding shares of
capital stock of each subsidiary have been duly and validly authorized and
issued and are fully paid and nonassessable, and, except as otherwise set forth
in the Prospectus, all outstanding shares of capital stock of the subsidiaries
are owned by the Company either directly or through wholly owned subsidiaries
free and clear of any security interests, claims, liens or encumbrances.

     (o)  No Prohibition on Subsidiaries from Paying Dividends or Making Other
Distributions.  No subsidiary of the Company is currently prohibited, directly
or indirectly, from paying any dividends to the Company, from making any other
distribution on such subsidiary's capital stock, from repaying to the Company
any loans or advances to such subsidiary from the Company or from transferring
any of such subsidiary's property or assets to the Company or any other
subsidiary of the Company, except as described in or contemplated by the
Prospectus, and except for contracts and license agreements that can not be
assigned without the consent of other parties thereto.

     (p)  Capitalization and Other Capital Stock Matters. The authorized, issued
and outstanding capital stock of the Company is as set forth in the Prospectus
under the caption "Capitalization" (other than for subsequent issuances, if any,
                   --------------
pursuant to employee benefit plans described in the Prospectus or upon exercise
of outstanding options or warrants described in the Prospectus).  The Common
Shares (including the Shares) conform in all material respects to the
description thereof contained in the Prospectus.  All of the issued and
outstanding Common Shares have been duly authorized and validly issued, are
fully paid and nonassessable and have been issued in compliance with federal and
state securities laws.  None of the outstanding Common Shares were issued in
violation of any preemptive rights, rights of first refusal or other similar
rights to subscribe for or purchase securities of the Company.  There are no
authorized or outstanding options, warrants, preemptive rights, rights of first
refusal or other rights to purchase, or equity or debt securities convertible
into or exchangeable or exercisable for, any capital stock of the Company or any
of its subsidiaries other than those accurately described in the Prospectus.
The description of the Company's stock option, stock bonus and other stock plans
or arrangements, and the options or other rights granted thereunder, set forth
in the Prospectus accurately and fairly describes in all material respects the
information required to be shown with respect to such plans, arrangements,
options and rights.

     (q)  Stock Exchange Listing. The Shares are registered pursuant to 12(g) of
the Exchange Act and are listed on the Nasdaq National Market, and the Company
has taken no action designed to, or likely to have the effect of, terminating
the registration of the Common Shares under the Exchange Act or delisting the
Common Shares from the Nasdaq National Market, nor has the Company received any
notification that the Commission or the National Association of Securities
Dealers, LLC (the "NASD") is contemplating terminating such registration or
                   ----
listing.

                                       5
<PAGE>

     (r)  No Consents, Approvals or Authorizations Required.  No consent,
approval, authorization, filing with or order of any court or governmental
agency or regulatory body is required in connection with the transactions
contemplated herein, except such as have been obtained or made under the
Securities Act and such as may be required (i) under the blue sky laws of any
jurisdiction in connection with the purchase and distribution of the Shares by
the Underwriters in the manner contemplated here and in the Prospectus, (ii) by
the NASD and (iii) by the federal and provincial laws of Canada.

     (s)  Non-Contravention of Existing Instruments Agreements.  Neither the
issue and sale of the Shares nor the consummation of any other of the
transactions herein contemplated nor the fulfillment of the terms hereof will
conflict with, result in a breach or violation or imposition of any lien, charge
or encumbrance upon any property or assets of the Company or any of its
subsidiaries pursuant to, (i) the charter or by-laws of the Company or any of
its subsidiaries, (ii) the terms of any indenture, contract, lease, mortgage,
deed of trust, note agreement, loan agreement or other agreement, obligation,
condition, covenant or instrument to which the Company or any of its
subsidiaries is a party or bound or to which its or their property is subject or
(iii) any statute, law, rule, regulation, judgment, order or decree applicable
to the Company or any of its subsidiaries of any court, regulatory body,
administrative agency, governmental body, arbitrator or other authority having
jurisdiction over the Company or any of its subsidiaries or any of its or their
properties.

     (t)  No Defaults or Violations.  Neither the Company nor any of its
subsidiaries is in violation or default of (i) any provision of its charter or
by-laws, (ii) the terms of any indenture, contract, lease, mortgage, deed of
trust, note agreement, loan agreement or other agreement, obligation, condition,
covenant or instrument to which it is a party or bound or to which its property
is subject or (iii) any statute, law, rule, regulation, judgment, order or
decree of any court, regulatory body, administrative agency, governmental body,
arbitrator or other authority having jurisdiction over the Company or such
subsidiary or any of its properties, as applicable, except any such violation or
default which would not, singly or in the aggregate, result in a Material
Adverse Change except as otherwise disclosed in the Prospectus.

     (u)  No Actions, Suits or Proceedings. Except as otherwise disclosed in the
Prospectus, no action, suit or proceeding by or before any court or governmental
agency, authority or body or any arbitrator involving the Company or any of its
subsidiaries or its or their property is pending or, to the best knowledge of
the Company, threatened that (i) could reasonably be expected to have a Material
Adverse Effect on the performance of this Agreement or the consummation of any
of the transactions contemplated hereby or (ii) could reasonably be expected to
result in a Material Adverse Effect.

     (v)  All Necessary Permits, Etc. Except to the extent that failure to do so
would not have a Material Adverse Effect, the Company and each of its
subsidiaries possess such valid and current certificates, authorizations or
permits issued by the appropriate state, federal or foreign regulatory agencies
or bodies necessary to conduct their respective businesses, and neither the
Company nor any subsidiary has received any notice of proceedings relating to
the revocation or modification of, or non-compliance with, any such certificate,
authorization or permit which, singly or in the aggregate, if the subject of an
unfavorable decision, ruling or finding, could result in a Material Adverse
Change.

     (w)  Title to Properties.  Except as otherwise disclosed in the Prospectus,
the Company and each of its subsidiaries has good and marketable title to all
the properties and

                                       6
<PAGE>

assets reflected as owned in the financial statements referred to in Section
1(A)(i) above (or elsewhere in the Prospectus), in each case free and clear of
any security interests, mortgages, liens, encumbrances, equities, claims and
other defects, except such as do not materially and adversely affect the value
of such property and do not materially interfere with the use made or proposed
to be made of such property by the Company or such subsidiary. The real
property, improvements, equipment and personal property held under lease by the
Company or any subsidiary are held under valid and enforceable leases, with such
exceptions as are not material and do not materially interfere with the use made
or proposed to be made of such real property, improvements, equipment or
personal property by the Company or such subsidiary.

     (x)  Tax Law Compliance. The Company and its consolidated subsidiaries have
filed all necessary federal, state and foreign income and franchise tax returns
and have paid all taxes required to be paid by any of them and, if due and
payable, any related or similar assessment, fine or penalty levied against any
of them. The Company has made adequate charges, accruals and reserves in the
applicable financial statements referred to in Section 1(A)(i) above in respect
of all federal, state and foreign income and franchise taxes for all periods as
to which the tax liability of the Company or any of its subsidiaries has not
been finally determined. The Company is not aware of any tax deficiency that has
been or might be asserted or threatened against the Company that could result in
a Material Adverse Change.

     (y)  Intellectual Property Rights. Except as disclosed in the Prospectus or
as would not result in a Material Adverse Effect, each of the Company and its
subsidiaries owns or possesses or has licensed or received under agreements
adequate rights to use all patents, patent rights or licenses, inventions, trade
secrets, know-how, trademarks, service marks, trade names and copyrights which
are necessary to conduct its businesses as described in the Prospectus. Except
as disclosed in the Prospectus, the Company has not received any notice of, is
not aware of any facts that would form a reasonable basis for, and has no
knowledge of, any infringement of or conflict with asserted rights of the
Company by others with respect to any patent, patent rights, inventions, trade
secrets, know-how, trademarks, service marks, trade names or copyrights which,
singly or in the aggregate, if the subject of an unfavorable decision, ruling or
finding, in the reasonable belief of the Company's management, would have a
Material Adverse Effect. Except as disclosed in the Prospectus, the Company has
not received any notice of, and has no knowledge of, any infringement of or
conflict with asserted rights of others with respect to any patent, patent
rights, inventions, trade secrets, know-how, trademarks, service marks, trade
names or copyrights which, singly or in the aggregate, if the subject of an
unfavorable decision, ruling or finding, might, in the reasonable belief of the
Company's management, have a Material Adverse Effect. Except as disclosed in the
Prospectus, there is, to the best knowledge of the Company, no claim being made
against the Company regarding patents, patent rights or licenses, inventions,
collaborative research, trade secrets, know-how, trademarks, service marks,
trade names or copyrights. To the best knowledge of the Company and except as
disclosed in the Prospectus, the Company and its subsidiaries do not in the
conduct of their business as now or proposed to be conducted as described in the
Prospectus infringe or otherwise conflict with any intellectual property right
or patent of any third party, and except as disclosed in the Prospectus, neither
the Company nor any of its subsidiaries has actual knowledge of a third party
patent application that conflicts with the conduct of their business as now
conducted or as proposed to be conducted as described in the Prospectus, or
that, if issued as a patent, would be infringed by the Company or its
subsidiaries in the conduct of their business as now conducted or as proposed to
be conducted as described in the Prospectus, which conflict or infringement is
reasonably likely to result in a Material Adverse Effect.

     (z)  No Transfer Taxes or Other Fees.  There are no transfer taxes or other
similar fees or charges under Federal law or the laws of any state, or any
political subdivision thereof,

                                       7
<PAGE>

required to be paid in connection with the execution and delivery of this
Agreement or the issuance and sale by the Company of the Shares.

     (aa) Company Not an "Investment Company".  The Company has been advised of
                          ------------------
the rules and requirements under the Investment Company Act of 1940, as amended
(the "Investment Company Act").  The Company is not, and after receipt of
      ----------------------
payment for the Shares will not be, an "investment company" or an entity
                                        ------------------
"controlled" by an "investment company" within the meaning of the Investment
-----------         ------------------
Company Act and will conduct its business in a manner so that it will not become
subject to the Investment Company Act.

     (bb) Insurance.  The Company and its subsidiaries are insured by
recognized, financially sound and reputable institutions with policies in such
amounts and with such deductibles and covering such risks as are generally
deemed adequate and customary for their businesses including, but not limited
to, policies covering real and personal property owned or leased by the Company
and its subsidiaries against theft, damage, destruction, acts of vandalism and
earthquakes, general liability and Directors and Officers liability.  The
Company has no reason to believe that it or any subsidiary will not be able (i)
to renew its existing insurance coverage as and when such policies expire or
(ii) to obtain comparable coverage from similar institutions as may be necessary
or appropriate to conduct its business as now conducted and at a cost that would
not result in a Material Adverse Change.  Neither of the Company nor any
subsidiary has been denied any insurance coverage which it has sought or for
which it has applied.

     (cc) Labor Matters.  To the best of Company's knowledge, no labor
disturbance by the employees of the Company or any of its subsidiaries exists or
is imminent; and the Company is not aware of any existing or imminent labor
disturbance by the employees of any of its principal suppliers, including
without limitation contractors and third party manufacturers that might be
expected to result in a Material Adverse Change.

     (dd) No Price Stabilization or Manipulation.  The Company has not taken and
will not 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 Common Stock to facilitate the sale or resale of the Shares.

     (ee) Lock-Up Agreements.  Each executive officer and director of the
Company, each Selling Shareholder and each of the other shareholders listed on
Schedule C hereto has agreed to sign an agreement substantially in the form
----------
attached hereto as Exhibit A (the "Lock-up Agreements").  The Company has
                   ---------       ------------------
provided to counsel for the Underwriters a complete and accurate list of all 1%
or greater securityholders of the Company which are known to the Company and
such list includes the number and type of securities held by each such
securityholder.  The Company has provided to counsel for the Underwriters true,
accurate and complete copies of all of the Lock-up Agreements presently in
effect or effected hereby.  The Company hereby represents and warrants that it
will not release any of its officers, directors or other shareholders from any
Lock-up Agreements currently existing or hereafter effected without the prior
written consent of Robertson Stephens.

     (ff) Related Party Transactions.  There are no business relationships or
related-party transactions involving the Company or any subsidiary or any other
person required to be described in the Prospectus which have not been described
as required.

                                       8
<PAGE>

     (gg) No Unlawful Contributions or Other Payments.  Neither the Company nor
any of its subsidiaries nor, to the best of the Company's knowledge, any
employee or agent of the Company or any subsidiary, has made any contribution or
other payment to any official of, or candidate for, any federal, state or
foreign office in violation of any law or of the character required to be
disclosed in the Prospectus.

     (hh) Environmental Laws.  The Company (i) is in compliance with all rules,
laws and regulations relating to the use, treatment, storage and disposal of
toxic substances and protection of health or the environment ("Environmental
                                                               -------------
Laws") which are applicable to its business, except where the failure to comply
----
would not result in a Material Adverse Change, (ii) has received no notice from
any governmental authority or third party of an asserted claim under
Environmental Laws, which claim is required to be disclosed in the Registration
Statement and the Prospectus, (iii) is not currently aware that it will be
required to make future material capital expenditures to comply with
Environmental Laws and (iv) does not own, lease or occupy any property which has
been designated as a Superfund site pursuant to the Comprehensive Response,
Compensation, and Liability Act of 1980, as amended (42 U.S.C. (S) 9601, et
                                                                         --
seq.), or otherwise designated as a contaminated site under applicable state or
----
local law.

     (ii) ERISA Compliance.  The Company and its subsidiaries and any "employee
                                                                       --------
benefit plan" (as defined under the Employee Retirement Income Security Act of
------------
1974, as amended, and the regulations and published interpretations thereunder
(collectively, "ERISA")) established or maintained by the Company, its
                -----
subsidiaries or their "ERISA Affiliates" (as defined below) are in compliance in
                       ----------------
all material respects with ERISA.  "ERISA Affiliate" means, with respect to the
                                    ---------------
Company or a subsidiary, any member of any group of organizations described in
Sections 414(b),(c),(m) or (o) of the Internal Revenue Code of 1986, as amended,
and the regulations and published interpretations thereunder (the "Code") of
                                                                   ----
which the Company or such subsidiary is a member.  No "reportable event" (as
defined under ERISA) has occurred or is reasonably expected to occur with
respect to any "employee benefit plan" established or maintained by the Company,
its subsidiaries or any of their ERISA Affiliates.  No "employee benefit plan"
established or maintained by the Company, its subsidiaries or any of their ERISA
Affiliates, if such "employee benefit plan" were terminated, would have any
"amount of unfunded benefit liabilities" (as defined under ERISA).  Neither the
Company, its subsidiaries nor any of their ERISA Affiliates has incurred or
reasonably expects to incur any liability under (i) Title IV of ERISA with
respect to termination of, or withdrawal from, any "employee benefit plan" or
(ii) Sections 412, 4971, 4975 or 4980B of the Code.  Each "employee benefit
plan" established or maintained by the Company, its subsidiaries or any of their
ERISA Affiliates that is intended to be qualified under Section 401(a) of the
Code is so qualified and nothing has occurred, whether by action or failure to
act, which would cause the loss of such qualification.

Any certificate signed by an officer of the Company and delivered to the
Representatives or to counsel for the Underwriters shall be deemed to be a
representation and warranty by the Company to each Underwriter as to the matters
set forth therein.

     B.   Representations and Warranties of the Selling Shareholders. Each
Selling Shareholder, severally and not jointly, represents, warrants and
covenants to each Underwriter as follows:

                                       9
<PAGE>

     (a)  The Underwriting Agreement.  This Agreement has been duly authorized,
executed and delivered by or on behalf of such Selling Shareholder and is a
valid and binding agreement of such Selling Shareholder, enforceable in
accordance with its terms, except as rights to indemnification and contribution
hereunder may be limited by applicable law and except as the enforcement hereof
may be limited by bankruptcy, insolvency, reorganization, moratorium or other
similar laws relating to or affecting the rights and remedies of creditors or by
general equitable principles.

     (b)  The Power of Attorney and Custody Agreement. The Power of Attorney and
Custody Agreement signed by such Selling Shareholder and the Company, as
custodian (the "Custodian"), relating to the deposit of the Shares to be sold by
                ---------
such Selling Shareholder (the "Power of Attorney and Custody Agreement") and
                               ---------------------------------------
appointing certain individuals named therein as such Selling Shareholder's
attorneys-in-fact (each, an "Attorney-in-Fact") has been duly authorized,
                             ----------------
executed and delivered by such Selling Shareholder and is a valid and binding
agreement of such Selling Shareholder, enforceable in accordance with its terms,
except as rights to indemnification and contribution thereunder may be limited
by applicable law and except as the enforcement thereof may be limited by
bankruptcy, insolvency, reorganization, moratorium or other similar laws
relating to or affecting the rights and remedies of creditors or by general
equitable principles.  Each Selling Shareholder agrees that the Shares to be
sold by such Selling Shareholder on deposit with the Custodian are subject to
the interests of the Underwriters, that the arrangements made for such custody
are to that extent irrevocable, and that the obligations of such Selling
Shareholder hereunder shall not be terminated, except as provided in this
Agreement or in the Power of Attorney and Custody Agreement, by any act of the
Selling Shareholder, by operation of law, by death or incapacity of such Selling
Shareholder or by the occurrence of any other event.  If such Selling
Shareholder should die or become incapacitated, or if any other event should
occur, before the delivery of the Shares to be sold by such Selling Shareholder
hereunder, the documents evidencing the Shares to be sold by such Selling
Shareholder then on deposit with the Custodian shall be delivered by the
Custodian in accordance with the terms and conditions of this Agreement as if
such death, incapacity or other event had not occurred, regardless of whether or
not the Custodian shall have received notice thereof.

     (c)  Title to Shares to be Sold.  Such Selling Shareholder is the lawful
owner of the Shares to be sold by such Selling Shareholder hereunder and upon
sale and delivery of, and payment for, such Shares, as provided herein, the
Underwriters will acquire all of the rights of such Selling Shareholder in such
Shares, free of any adverse claim (as defined in Section 8-102 of the Uniform
Commercial Code).

     (d)  All Authorizations Obtained.  Such Selling Shareholder has, and on the
First Closing Date and the Second Closing Date (as defined below) will have,
good and valid title to all of the Company Shares which may be sold by such
Selling Shareholder pursuant to this Agreement on such date and the legal right
and power, and all authorizations and approvals required by law and under its
charter or by-laws, partnership agreement, trust agreement or other
organizational documents, as applicable, to enter into this Agreement and its
Custody Agreement and Power of Attorney, to sell, transfer and deliver all of
the Shares which may be sold by such Selling Shareholder pursuant to this
Agreement and to comply with its other obligations hereunder and thereunder.

     (e)  No Further Consents, Authorization or Approvals. No consent, approval,
authorization or order of any court or governmental agency or body is required
for the

                                       10
<PAGE>

consummation by such Selling Shareholder of the transactions contemplated
herein, except such as may have been obtained under the Securities Act and such
as may be required under the federal and provincial securities laws of Canada or
the blue sky laws or any jurisdiction in connection with the purchase and
distribution of the Shares by the Underwriters and such other approvals as have
been obtained.

     (f)  Non-Contravention.  Neither the sale of the Securities being sold by
such Selling Shareholder nor the consummation of any other of the transactions
herein contemplated by such Selling Shareholder or the fulfillment of the terms
hereof by such Selling Shareholder will conflict with, result in a breach or
violation of, or constitute a default under any law or the terms of any
indenture or other agreement or instrument to which such Selling Shareholder is
party or bound, any judgment, order or decree applicable to such Selling
Shareholder or any court or regulatory body, administrative agency, governmental
body or arbitrator having jurisdiction over such Selling Shareholder.

     (g)  No Registration or Other Similar Rights. Such Selling Shareholder does
not have any registration or other similar rights to have any equity or debt
securities registered for sale by the Company under the Registration Statement
or included in the offering contemplated by this Agreement, except for such
rights as are described in the Prospectus under "Shares Eligible for Future
Sale" and "Description of Capital Stock -- Registration Rights."

     (h)  No Preemptive, Co-sale or other Rights.  Such Selling Shareholder does
not have, or has waived prior to the date hereof, any preemptive right, co-sale
right or right of first refusal or other similar right to purchase any of the
Shares that are to be sold by the Company or any of the other Selling
Shareholders to the Underwriters pursuant to this Agreement; and such Selling
Shareholder does not own any warrants, options or similar rights to acquire, and
does not have any right or arrangement to acquire, any capital stock, right,
warrants, options or other securities from the Company, other than those
described in the Registration Statement and the Prospectus.

     (i)  Disclosure Made by Such Selling Shareholder in the Prospectus.  All
information furnished by or on behalf of such Selling Shareholder in writing
expressly for use in the Registration Statement and Prospectus is, and on the
First Closing Date and the Second Closing Date will be, true, correct, and
complete in all material respects, and does not, and on the First Closing Date
and the Second Closing Date will not, contain any untrue statement of a material
fact or omit to state any material fact necessary to make such information, in
light of the circumstances under which they were made, not misleading.  Such
Selling Shareholder confirms as accurate the number of shares of Company Shares
set forth opposite such Selling Shareholder's name in the Prospectus under the
caption "Principal and Selling Shareholders" (both prior to and after giving
effect to the sale of the Shares).

     (j)  No Price Stabilization or Manipulation.  Such Selling Shareholder has
not taken and will not 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 Common Stock to facilitate the sale or resale
of the Shares.

     (k)  No Transfer Taxes or Other Fees.  The Selling Shareholders shall pay
any transfer taxes or other similar fees or charges under Federal law or the
laws of any state, or

                                       11
<PAGE>

any political subdivision thereof, required to be paid in connection with the
execution and delivery of this Agreement or the sale by the Selling Shareholders
of the Shares.

     (l)  Distribution of Offering Materials by the Selling Shareholders.  The
Selling Shareholders have not distributed and will not distribute, prior to the
later of the Second Closing Date (as defined below) and the completion of the
Underwriters' distribution of the Shares, any offering material in connection
with the offering and sale of the Shares by such Selling Shareholder other than
a preliminary prospectus, the Prospectus or the Registration Statement.

     (m) Confirmation of Company Representations and Warranties. Without having
undertaken to determine independently the accuracy or completeness of either the
representations and warranties of the Company contained herein or the
information contained in the Registration Statement, such Principal Selling
Shareholder has no reason to believe that the representations and warranties of
the Company contained in Section 1(A) hereof are not true and correct, is
familiar with the Registration Statement and the Prospectus and has no knowledge
of any material fact, condition or information not disclosed in the Registration
Statement or the Prospectus which has had or may result in a Material Adverse
Change on the condition, financial or otherwise, or on the earnings, business,
operation or prospects, whether or not arising from transactions in the ordinary
course of business of the Company and its subsidiaries, considered as one
entity, and such Selling Shareholder is not prompted to sell the Shares to be
sold by such Selling Shareholder by any information concerning the Company which
is not set forth in the Registration Statement and the Prospectus.

          Any certificate signed by or on behalf of any Selling Shareholder and
delivered to the Representatives or to counsel for the Underwriters shall be
deemed to be a representation and warranty by such Selling Shareholder to each
Underwriter as to the matters covered thereby.

     Section 2.  Purchase, Sale and Delivery of the Shares.

     (a)  The Firm Shares.  Upon the terms herein set forth, (i) the Company
agrees to issue and sell to the several Underwriters an aggregate of 5,000,000
Firm Shares and (ii) the Selling Shareholders agree to sell to the several
Underwriters an aggregate of 1,000,000 Firm Shares, each Selling Shareholder
selling the number of Firm Shares set forth opposite such Selling Shareholder's
name on Schedule B.  On the basis of the representations, warranties and
        ----------
agreements herein contained, and upon the terms but subject to the conditions
herein set forth, the Underwriters agree, severally and not jointly, to purchase
from the Company and the Selling Shareholders the respective number of Firm
Shares set forth opposite their names on Schedule A.  The purchase price per
                                         ----------
Firm Share to be paid by the several Underwriters to the Company and the Selling
Shareholders shall be $[___] per share.

     (b)  The First Closing Date. Delivery of the Firm Shares to be purchased by
the Underwriters and payment therefor shall be made by the Company and the
Representatives at 9:00 A.M. Richmond, Virginia time, at the offices of Hunton &
Williams, Riverfront Plaza, 951 East Byrd Street, Richmond, Virginia 23219 (or
at such other place as may be agreed upon among the Representatives and the
Company), (i) on the third (3/rd/) full business day following the first day
that Shares are traded, (ii) if this Agreement is executed and delivered after
4:30 P.M., Richmond time, the fourth (4/th/) full business day following the day
that this Agreement is executed and delivered or (iii) at such other time and
date not later than seven

                                       12
<PAGE>

(7) full business days following the first day that Shares are traded as the
Representatives and the Company may determine (or at such time and date to which
payment and delivery shall have been postponed pursuant to Section 8 hereof),
such time and date of payment and delivery being herein called the "Closing
                                                                    -------
Date;" provided, however, that if the Company has not made available to the
----   ------------   --------  -------
Representatives copies of the Prospectus within the time provided in Section
2(g) and 3(e) hereof, the Representatives may, in their sole discretion,
postpone the Closing Date until no later that two (2) full business days
following delivery of copies of the Prospectus to the Representatives.

     (c)  The Option Shares; the Second Closing Date.  In addition, on the basis
of the representations, warranties and agreements herein contained, and upon the
terms but subject to the conditions herein set forth, the Selling Shareholders
hereby grant an option to the several Underwriters to purchase, severally and
not jointly, up to an aggregate of 900,000 Option Shares from the Selling
Shareholders at the purchase price per share to be paid by the Underwriters for
the Firm Shares.  The option granted hereunder is for use by the Underwriters
solely in covering any over-allotments in connection with the sale and
distribution of the Firm Shares.  The option granted hereunder may be exercised
at any time upon notice by the Representatives to the Company and the Selling
Shareholders, which notice may be given at any time within 30 days from the date
of this Agreement.  The time and date of delivery of the Option Shares, if
subsequent to the First Closing Date, is called the "Second Closing Date" and
                                                     -------------------
shall be determined by the Representatives and shall not be earlier than three
nor later than five full business days after delivery of such notice of
exercise.  If any Option Shares are to be purchased, (i) each Underwriter
agrees, severally and not jointly, to purchase the number of Option Shares
(subject to such adjustments to eliminate fractional shares as the
Representatives may determine) that bears the same proportion to the total
number of Option Shares to be purchased as the number of Firm Shares set forth
on Schedule A opposite the name of such Underwriter bears to the total number of
   ----------
Firm Shares and (ii) each Selling Shareholder agrees, severally and not jointly,
to sell the number of Option Shares set forth in Schedule B opposite the name of
                                                 ----------
such Selling Shareholder.  The Representatives may cancel the option at any time
prior to its expiration by giving written notice of such cancellation to the
Company and the Selling Shareholders.

     (d)  Public Offering of the Shares.  The Representatives hereby advise the
Company and the Selling Shareholders that the Underwriters intend to offer for
sale to the public, as described in the Prospectus, their respective portions of
the Shares as soon after this Agreement has been executed and the Registration
Statement has been declared effective as the Representatives, in their sole
judgment, have determined is advisable and practicable.

     (e)  Payment for the Shares.  Payment for the Shares to be sold by the
Company shall be made at the First Closing Date by wire transfer of immediately
available funds to the order of the Company.  Payment for the Shares to be sold
by the Selling Shareholders shall be made at the First Closing Date (and, if
applicable, at the Second Closing Date) by wire transfer of immediately
available funds to the order of the Custodian.

          It is understood that the Representatives have been authorized, for
their own account and the accounts of the several Underwriters, to accept
delivery of and receipt for, and make payment of the purchase price for, the
Firm Shares and any Option Shares the Underwriters have agreed to purchase.
Robertson Stephens, Inc., individually and not as the Representatives of the
Underwriters, may (but shall not be obligated to) make payment for any

                                       13
<PAGE>

Shares to be purchased by any Underwriter whose funds shall not have been
received by the Representatives by the First Closing Date or the Second Closing
Date, as the case may be, for the account of such Underwriter, but any such
payment shall not relieve such Underwriter from any of its obligations under
this Agreement.

          Each Selling Shareholder hereby agrees that (i) it will pay all stock
transfer taxes, stamp duties and other similar taxes, if any, payable upon the
sale or delivery of the Shares to be sold by such Selling Shareholder to the
several Underwriters, or otherwise in connection with the performance of such
Selling Shareholder's obligations hereunder and (ii) the Custodian is authorized
to deduct for such payment any such amounts from the proceeds to such Selling
Shareholder hereunder and to hold such amounts for the account of such Selling
Shareholder with the Custodian under the Custody Agreement.

     (f)  Delivery of the Shares. The Company and the Selling Shareholders shall
deliver, or cause to be delivered a credit representing the Firm Shares to an
account or accounts at The Depository Trust Company as designated by the
Representatives for the accounts of the Representatives and the several
Underwriters at the First Closing Date, against the irrevocable release of a
wire transfer of immediately available funds for the amount of the purchase
price therefor. The Company and the Selling Shareholders shall also deliver, or
cause to be delivered a credit representing the Option Shares to an account or
accounts at The Depository Trust Company as designated by the Representatives
for the accounts of the Representatives and the several Underwriters, at the
First Closing Date or the Second Closing Date, as the case may be, against the
irrevocable release of a wire transfer of immediately available funds for the
amount of the purchase price therefor. Time shall be of the essence, and
delivery at the time and place specified in this Agreement is a further
condition to the obligations of the Underwriters.

     (g)  Delivery of Prospectus to the Underwriters.  Not later than 12:00 noon
on the second business day following the date the Shares are released by the
Underwriters for sale to the public, the Company shall deliver or cause to be
delivered copies of the Prospectus in such quantities and at such places as the
Representatives shall request.

     Section 3.  Covenants of the Company and the Selling Shareholders.

     A.          Covenants of the Company.

          The Company further covenants and agrees with each Underwriter as
follows:

     (a)  Registration Statement Matters.  The Company will (i) use its best
efforts to cause the Registration Statement to become effective or, if the
procedure in Rule 430A of the Securities Act is followed, to prepare and timely
file with the Commission under Rule 424(b) under the Securities Act a Prospectus
in a form approved by the Representatives containing information previously
omitted at the time of effectiveness of the Registration Statement in reliance
on Rule 430A of the Securities Act and (ii) not file any amendment to the
Registration Statement or supplement to the Prospectus of which the
Representatives shall not previously have been advised and furnished with a copy
or to which the Representatives shall have reasonably objected in writing or
which is not in compliance with the Securities Act. If the Company elects to
rely on Rule 462(b) under the Securities Act, the Company shall file a Rule
462(b) Registration Statement with the Commission in compliance with Rule 462(b)
under the Securities Act prior to the time confirmations are sent or given, as
specified by

                                       14
<PAGE>

Rule 462(b)(2) under the Securities Act, and shall pay the applicable fees in
accordance with Rule 111 under the Securities Act.

     (b)  Securities Act Compliance. The Company will advise the Representatives
promptly (i) when the Registration Statement or any post-effective amendment
thereto shall have become effective, (ii) of receipt of any comments from the
Commission, (iii) of any request of the Commission for amendment of the
Registration Statement or for supplement to the Prospectus or for any additional
information and (iv) of the issuance by the Commission of any stop order
suspending the effectiveness of the Registration Statement or the use of the
Prospectus or of the institution of any proceedings for that purpose. The
Company will use its best efforts to prevent the issuance of any such stop order
preventing or suspending the use of the Prospectus and to obtain as soon as
possible the lifting thereof, if issued.

     (c)  Blue Sky Compliance.  The Company will cooperate with the
Representatives and counsel for the Underwriters in endeavoring to qualify the
Shares for sale under the securities laws of such jurisdictions (both national
and foreign) as the Representatives may reasonably have designated in writing
and will make such applications, file such documents, and furnish such
information as may be reasonably required for that purpose, provided the Company
shall not be required to qualify as a foreign corporation or to file a general
consent to service of process in any jurisdiction where it is not now so
qualified or required to file such a consent.  The Company will, from time to
time, prepare and file such statements, reports and other documents, as are or
may be required to continue such qualifications in effect for so long a period
as the Representatives may reasonably request for distribution of the Shares.

     (d)  Amendments and Supplements to the Prospectus and Other Securities Act
Matters.  The Company will comply with the Securities Act and the Exchange Act,
and the rules and regulations of the Commission thereunder, so as to permit the
completion of the distribution of the Shares as contemplated in this Agreement
and the Prospectus.  If during the period in which a prospectus is required by
law to be delivered by an Underwriter or dealer, any event shall occur as a
result of which, in the judgment of the Company or in the reasonable opinion of
the Representatives or counsel for the Underwriters, it becomes necessary to
amend or supplement the Prospectus in order to make the statements therein, in
the light of the circumstances existing at the time the Prospectus is delivered
to a purchaser, not misleading, or, if it is necessary at any time to amend or
supplement the Prospectus to comply with any law, the Company promptly will
prepare and file with the Commission, and furnish at its own expense to the
Underwriters and to dealers, an appropriate amendment to the Registration
Statement or supplement to the Prospectus so that the Prospectus as so amended
or supplemented will not, in the light of the circumstances when it is so
delivered, be misleading, or so that the Prospectus will comply with the law.

     (e)  Copies of any Amendments and Supplements to the Prospectus.  The
Company agrees to furnish the Representatives, without charge, during the period
beginning on the date hereof and ending on the later of the First Closing Date
or such date, as in the opinion of counsel for the Underwriters, the Prospectus
is no longer required by law to be delivered in connection with sales by an
Underwriter or dealer (the "Prospectus Delivery Period"), as many copies of the
                            --------------------------
Prospectus and any amendments and supplements thereto (including any documents
incorporated or deemed incorporated by reference therein) as the Representatives
may request.

                                       15
<PAGE>

     (f)  Insurance.  The Company shall (i) obtain Directors and Officers
liability insurance in the minimum amount of $10 million which shall apply to
the offering contemplated hereby and (ii) cause Robertson Stephens to be added
to such policy such that up to $500,000 of its expenses pursuant to section 7(a)
shall be paid directly by such insurer and (iii) shall cause Robertson Stephens
to be added as an additional insured to such policy in respect of the offering
contemplated hereby.

     (g)  Notice of Subsequent Events. If at any time during the ninety (90) day
period after the Registration Statement becomes effective, any rumor,
publication or event relating to or affecting the Company shall occur as a
result of which, in the Representatives' opinion, the market price of the
Company Shares has been or is likely to be materially affected (regardless of
whether such rumor, publication or event necessitates a supplement to or
amendment of the Prospectus), the Company will, after written notice from the
Representative advising the Company to the effect set forth above, forthwith
prepare, consult with the Representative concerning the substance of and
disseminate a press release or other public statement, reasonably satisfactory
to the Representative, responding to or commenting on such rumor, publication or
event.

     (h)  Use of Proceeds.  The Company shall apply the net proceeds from the
sale of the Shares sold by it in the manner described under the caption "Use of
                                                                         ------
Proceeds" in the Prospectus.
--------

     (i)  Transfer Agent. The Company shall engage and maintain, at its expense,
a registrar and transfer agent for the Company Shares.

     (j)  Earnings Statement.  As soon as practicable, the Company will make
generally available to its security holders and to the Representatives an
earnings statement (which need not be audited) covering the twelve-month period
ending December 31, 2001 that satisfies the provisions of Section 11(a) of the
Securities Act.

     (k)  Periodic Reporting Obligations.  During the Prospectus Delivery Period
the Company shall file, on a timely basis, with the Commission and the Nasdaq
National Market all reports and documents required to be filed under the
Exchange Act.

     (l)  Agreement Not to Offer or Sell Additional Securities. The Company
will, without the prior written consent of Robertson Stephens, not offer, sell
or contract to sell, or otherwise dispose of or enter into any transaction which
is designed to, or could be expected to, result in the disposition (whether by
actual disposition or effective economic disposition due to cash settlement or
otherwise by the Company or any affiliate of the Company or any person in
privity with the Company or any affiliate of the Company) directly or
indirectly, or announce the offering of, any other Common Shares or any
securities convertible into, or exchangeable for, Common Shares; provided,
                                                                 --------
however, that the Company may (i) issue and sell Common Shares pursuant to any
-------
director or employee stock option plan, stock purchase plan or other equity
compensation plan of the Company in effect at the date of the Prospectus and
described in the Prospectus so long as none of those shares may be transferred
and the Company shall enter stop transfer instructions with its transfer agent
and registrar against the transfer of any such Common Shares and (ii) the
Company may issue Common Shares issuable upon the conversion of securities or
the exercise of options or warrants outstanding at the date of the Prospectus
and described in the Prospectus.  These restrictions terminate after

                                       16
<PAGE>

the close of trading of the Shares on the 90/th/ day of (and including) the day
the Shares commenced trading on the Nasdaq National Market (the "Lock-Up
                                                                 -------
Period").
------

     (m)  Future Reports to the Representatives. During the period of five years
hereafter the Company will furnish or make available to the Representatives (i)
as soon as practicable after the end of each fiscal year, copies of the Annual
Report of the Company containing the balance sheet of the Company as of the
close of such fiscal year and statements of income, shareholders' equity and
cash flows for the year then ended and the opinion thereon of the Company's
independent public or certified public accountants; (ii) as soon as practicable
after the filing thereof, copies of each proxy statement, Annual Report on Form
10-K, Quarterly Report on Form 10-Q, Current Report on Form 8-K or other report
filed by the Company with the Commission, the NASD, The Nasdaq Stock Market,
Inc. or any securities exchange; and (iii) as soon as available, copies of any
report or communication of the Company mailed generally to holders of its
capital stock.

     (n)  Exchange Act Compliance. During the Prospectus Delivery Period, the
Company will file all documents required to be filed with the Commission
pursuant to Section 13, 14 or 15 of the Exchange Act in the manner and within
the time periods required by the Exchange Act.

     B.   Covenants of the Selling Shareholders. Each Selling Shareholder
further covenants and agrees with each Underwriter:

     (a)  Agreement Not to Offer or Sell Additional Securities.  Such Selling
Shareholder will not, during the Lock-Up Period (as defined in Exhibit A
                                                               ---------
hereto), make a disposition of Securities (as defined in Exhibit A hereto) now
                                                         ---------
owned or hereafter acquired directly by such person or with respect to which
such person has or hereafter acquires the power of disposition, otherwise than
as has been agreed to in writing pursuant to the Lock-Up Agreement by and
between the Representatives and each such Selling Shareholder.  Each agreement
and covenant made in each Lock-Up Agreement by each Selling Shareholder is
incorporated by reference herein.  Furthermore, such Selling Shareholder also
agrees and consents to the entry of stop transfer instructions with the
Company's transfer agent against the transfer of the Securities held by such
Selling Shareholder except in compliance with this restriction.

     (b)  Delivery of Forms W-8 and W-9. To deliver to the Representatives prior
to the First Closing Date a properly completed and executed United States
Treasury Department Form W-8 (if the Selling Shareholder is a non-United States
person) or Form W-9 (if the Selling Shareholder is a United States Person).

     (c)  Notification of Untrue Statements, etc.  If, at any time prior to the
date on which the distribution of the Common Shares as contemplated herein and
in the Prospectus has been completed, as determined by the Representatives, (i)
such Principal Selling Shareholder has knowledge of the occurrence of any event
as a result of which the Prospectus or the Registration Statement, in each case
as then amended or supplemented, would include an untrue statement of a material
fact or omit to state any material fact necessary to make the statements
therein, in light of the circumstances under which they were made, not
misleading, such Principal Selling Shareholder will promptly notify the Company
and the Representatives and (ii) such Other Selling Shareholder has knowledge of
the occurrence of any event as a result of which the information furnished by or
on behalf of such Other Selling Shareholder in writing expressly for use in the
Registration Statement and Prospectus, in each case as then

                                       17
<PAGE>

amended or supplemented, includes an untrue statement of a material fact or
omits to state a material fact necessary to make the statements therein, in
light of the circumstances under which they were made, not misleading, such
Other Selling Shareholder will promptly notify the Company and the
Representatives.

     Section 4.  Conditions of the Obligations of the Underwriters. The
obligations of the several Underwriters to purchase and pay for the Shares as
provided herein on the First Closing Date and, with respect to the Option
Shares, the Second Closing Date, shall be subject to the accuracy of the
representations and warranties on the part of the Company and the Selling
Shareholders set forth in Sections 1(A) and 1(B) hereof as of the date hereof
and as of the First Closing Date as though then made and, with respect to the
Option Shares, as of the Second Closing Date as though then made, to the timely
performance by the Company and the Selling Shareholders of their respective
covenants and other obligations hereunder, and to each of the following
additional conditions:

     (a)  Compliance with Registration Requirements; No Stop Order; No Objection
from the National Association of Securities Dealers, LLC.  The Registration
Statement shall have become effective prior to the execution of this Agreement,
or at such later date as shall be consented to in writing by you; and no stop
order suspending the effectiveness thereof shall have been issued and no
proceedings for that purpose shall have been initiated or, to the knowledge of
the Company, any Selling Shareholder or any Underwriter, threatened by the
Commission, and any request of the Commission for additional information (to be
included in the Registration Statement or the Prospectus or any Incorporated
Document or otherwise) shall have been complied with to the satisfaction of
Underwriters' Counsel; and the NASD shall have raised no objection to the
fairness and reasonableness of the underwriting terms and arrangements.

     (b)  Corporate Proceedings.  All corporate proceedings and other legal
matters in connection with this Agreement, the form of Registration Statement
and the Prospectus, and the registration, authorization, issue, sale and
delivery of the Shares, shall have been reasonably satisfactory to Underwriters'
Counsel, and such counsel shall have been furnished with such papers and
information as they may reasonably have requested to enable them to pass upon
the matters referred to in this Section.

     (c)  No Material Adverse Change.  Subsequent to the execution and delivery
of this Agreement and prior to the First Closing Date, or the Second Closing
Date, as the case may be, other than continuing operating losses in such amounts
and resulting from such factors as are consistent with past practice, there
shall not have been any Material Adverse Change in the condition (financial or
otherwise), earnings, operations, business or business prospects of the Company
and its subsidiaries considered as one enterprise from that set forth in the
Registration Statement or Prospectus, which, in your sole judgment, is material
and adverse and that makes it, in your sole judgment, impracticable or
inadvisable to proceed with the public offering of the Shares as contemplated by
the Prospectus.

     (d)  Opinion of Counsel for the Company.  You shall have received on the
First Closing Date, or the Second Closing Date, as the case may be, an opinion
of Hunton & Williams, counsel for the Company, substantially in the form of
Exhibit B attached hereto, dated the First Closing Date, or the Second Closing
---------
Date, addressed to the Underwriters and with reproduced copies or signed
counterparts thereof for each of the Underwriters.

                                       18
<PAGE>

           Counsel rendering the opinion contained in Exhibit B may rely as to
                                                      ---------
questions of law not involving the laws of the United States or the Commonwealth
of Virginia upon opinions of local counsel, and as to questions of fact upon
representations or certificates of officers of the Company, the Selling
Shareholders or officers of the Selling Shareholders (when the Selling
Shareholder is not a natural person), and of government officials, in which case
their opinion is to state that they are so relying and that they have no
knowledge of any material misstatement or inaccuracy in any such opinion,
representation or certificate.  Copies of any opinion, representation or
certificate so relied upon shall be delivered to you, as Representatives of the
Underwriters, and to Underwriters' Counsel.

     (e)   Opinion of Intellectual Property Counsel for the Company.  You shall
have received on the First Closing Date, or the Second Closing Date, as the case
may be, an opinion of Foley & Lardner, intellectual property counsel for the
Company, substantially in the form of Exhibit C-1 attached hereto.
                                      -----------

     (e-1) Opinion of Intellectual Property Counsel for the Company.  You shall
have received on the First Closing Date, or the Second Closing Date, as the case
may be, an opinion of Sterne, Kessler, Goldstein & Fox, intellectual property
counsel for the Company, substantially in the form of Exhibit C-2 attached
                                                      -----------
hereto.

     (f)   Opinion of Counsel for the Underwriters.  You shall have received on
the First Closing Date or the Second Closing Date, as the case may be, an
opinion of Testa, Hurwitz & Thibeault, LLP, substantially in the form of Exhibit
                                                                         -------
D hereto.  The Company shall have furnished to such counsel such documents as
-
they may have requested for the purpose of enabling them to pass upon such
matters.

     (g)   Accountants' Comfort Letter.  You shall have received on the First
Closing Date and on the Second Closing Date, as the case may be, a letter from
Ernst & Young LLP addressed to the Underwriters, dated the First Closing Date or
the Second Closing Date, as the case may be, confirming that they are
independent certified public accountants with respect to the Company within the
meaning of the Securities Act and the applicable published Rules and Regulations
and based upon the procedures described in such letter delivered to you
concurrently with the execution of this Agreement (herein called the "Original
                                                                      --------
Letter"), but carried out to a date not more than four (4) business days prior
------
to the First Closing Date or the Second Closing Date, as the case may be, (i)
confirming, to the extent true, that the statements and conclusions set forth in
the Original Letter are accurate as of the First Closing Date or the Second
Closing Date, as the case may be, and (ii) setting forth any revisions and
additions to the statements and conclusions set forth in the Original Letter
which are necessary to reflect any changes in the facts described in the
Original Letter since the date of such letter, or to reflect the availability of
more recent financial statements, data or information.  The letter shall not
disclose any change in the condition (financial or otherwise), earnings,
operations, business or business prospects of the Company and its subsidiaries
considered as one enterprise from that set forth in the Registration Statement
or Prospectus, which, in your sole judgment, is material and adverse and that
makes it, in your sole judgment, impracticable or inadvisable to proceed with
the public offering of the Shares as contemplated by the Prospectus.  The
Original Letter from Ernst & Young LLP shall be addressed to or for the use of
the Underwriters in form and substance satisfactory to the Underwriters and
shall (i) represent, to the extent true, that they are independent certified
public accountants with respect to the Company within the meaning of the
Securities Act and the applicable published Rules and Regulations, (ii) set
forth their opinion with respect to their examination of the

                                       19
<PAGE>

condensed consolidated balance sheet of the Company as of December 31, 1999, the
consolidated balance sheet of Insmed Pharmaceuticals, Inc. as of December 31,
1999 and related consolidated statements of operations, shareholders' equity,
and cash flows for the twelve (12) months ended December 31, 1999, and the
consolidated balance sheet of Celtrix Pharmaceuticals, Inc. as of March 31, 2000
and the related consolidated statements of operations, shareholders' equity and
cash flows for the twelve months (12) ended March 31, 2000, (iii) state that
Ernst & Young LLP has performed the procedures set out in Statement on Auditing
Standards No. 71 ("SAS 71") for a review of interim financial information and
                   ------
providing the report of Ernst & Young LLP as described in SAS 71 on the
financial statements for each of the quarters in the two-quarter period ended
June 30, 2000 (the "Quarterly Financial Statements"), (iv) state that in the
                    ------------------------------
course of such review, nothing came to their attention that leads them to
believe that any material modifications need to be made to any of the Quarterly
Financial Statements in order for them to be in compliance with generally
accepted accounting principles consistently applied across the periods
presented, and address other matters agreed upon by Ernst & Young LLP and you.
In addition, you shall have received from Ernst & Young LLP a letter addressed
to the Company and made available to you for the use of the Underwriters stating
that their review of the Company's system of internal accounting controls, to
the extent they deemed necessary in establishing the scope of their examination
of the Company's consolidated financial statements as of December 31, 1999, did
not disclose any weaknesses in internal controls that they considered to be
material weaknesses.

     (h)   Officers' Certificate.  You shall have received on the First Closing
Date and the Second Closing Date, as the case may be, a certificate of the
Company, dated the First Closing Date or the Second Closing Date, as the case
may be, signed by the Chief Executive Officer and Chief Financial Officer of the
Company, to the effect that, and you shall be satisfied that:

     (i)   The representations and warranties of the Company in this Agreement
     are true and correct, as if made on and as of the First Closing Date or the
     Second Closing Date, as the case may be, and the Company has complied with
     all the agreements and satisfied all the conditions on its part to be
     performed or satisfied at or prior to the First Closing Date or the Second
     Closing Date, as the case may be;

     (ii)  No stop order suspending the effectiveness of the Registration
     Statement has been issued and no proceedings for that purpose have been
     instituted or are pending or threatened under the Securities Act;

     (iii) When the Registration Statement became effective and at all times
     subsequent thereto up to the delivery of such certificate, the Registration
     Statement and the Prospectus, and any amendments or supplements thereto
     contained all material information required to be included therein by the
     Securities Act or the Exchange Act and the applicable rules and regulations
     of the Commission thereunder, as the case may be, and in all material
     respects conformed to the requirements of the Securities Act or the
     Exchange Act and the applicable rules and regulations of the Commission
     thereunder, as the case may be, the Registration Statement and the
     Prospectus, and any amendments or supplements thereto, did not and does not
     include 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, since the effective date of the Registration
     Statement, there has occurred no event required to be set forth in an
     amended or supplemented Prospectus which has not been so set forth; and

                                       20
<PAGE>

     (iv) Subsequent to the respective dates as of which information is given
     in the Registration Statement and Prospectus, there has not been (a) other
     than continuing operating losses in such amounts and resulting from such
     factors as are consistent with past practice, any material adverse change
     in the condition (financial or otherwise), earnings, operations, business
     or business prospects of the Company and its subsidiaries considered as one
     enterprise, (b) any transaction that is material to the Company and its
     subsidiaries considered as one enterprise, except transactions entered into
     in the ordinary course of business, (c) any obligation, direct or
     contingent, that is material to the Company and its subsidiaries considered
     as one enterprise, incurred by the Company or its subsidiaries, except
     obligations incurred in the ordinary course of business, (d) any change in
     the capital stock or outstanding indebtedness of the Company or any of its
     subsidiaries that is material to the Company and its subsidiaries
     considered as one enterprise, (e) any dividend or distribution of any kind
     declared, paid or made on the capital stock of the Company or any of its
     subsidiaries, or (f) any loss or damage (whether or not insured) to the
     property of the Company or any of its subsidiaries which has been sustained
     or will have been sustained which has a material adverse effect on the
     condition (financial or otherwise), earnings, operations, business or
     business prospects of the Company and its subsidiaries considered as one
     enterprise.

     (i)  Lock-up Agreement from Certain Shareholders of the Company.  The
Company shall have obtained and delivered to you an agreement substantially in
the form of Exhibit A attached hereto from each officer and director of the
            ---------
Company, each Selling Shareholder and each of the shareholders listed on
Schedule C hereto.
----------

     (j)  Opinion of Counsel for the Selling Shareholders.  You shall have
received on the First Closing Date and the Second Closing Date, as the case may
be, an opinion of counsel for each Selling Shareholder, substantially in the
form of Exhibit E hereto.
        ---------

          In rendering such opinion, such counsel may rely as to questions of
fact upon representations or certificates of the Selling Shareholders or
officers of the Selling Shareholders (when the Selling Shareholder is not a
natural person), and of governmental officials, in which case their opinion is
to state that they are so relying and that they have no knowledge of any
material misstatement or inaccuracy of any material misstatement or inaccuracy
in any such representation or certificate so relied upon shall be delivered to
you, as Representatives of the Underwriters, and to Underwriters' Counsel.

     (k)  Selling Shareholders' Certificate.  On each of the First Closing Date
and the Second Closing Date, as the case may be, the Representatives shall have
received a written certificate executed by each Selling Shareholder or its
Attorney-in-Fact, dated as of such Closing Date, to the effect that:

     (i)  the representations, warranties and covenants of such Selling
     Shareholder set forth in Section 1(B) of this Agreement are true and
     correct with the same force and effect as though expressly made by such
     Selling Shareholder on and as of such Closing Date; and

     (ii) such Selling Shareholder has complied with all the agreements and
     satisfied all the conditions on its part to be performed or satisfied at or
     prior to such Closing Date.

                                       21
<PAGE>

     (l) Selling Shareholders' Documents.  At least three (3) business days
prior to the date hereof, the Company and the Selling Shareholders shall have
furnished for review by the Representatives copies of the Powers of Attorney and
Custody Agreement executed by each of the Selling Shareholders and such further
information, certificates and documents as the Representatives may reasonably
request.

     (m) Stock Exchange Listing.  The Shares shall have been approved for
listing on the Nasdaq National Market, subject only to official notice of
issuance.

     (n) Compliance with Prospectus Delivery Requirements.  The Company shall
have complied with the provisions of Sections 2(g) and 3(e) hereof with respect
to the furnishing of Prospectuses.

     (o) Additional Documents.  On or before each of the First Closing Date and
the Second Closing Date, as the case may be, the Representatives and counsel for
the Underwriters shall have received such information, documents and opinions as
they may reasonably require for the purposes of enabling them to pass upon the
issuance and sale of the Shares as contemplated herein, or in order to evidence
the accuracy of any of the representations and warranties, or the satisfaction
of any of the conditions or agreements, herein contained.

         If any condition specified in this Section 4 is not satisfied when and
as required to be satisfied, this Agreement may be terminated by the
Representatives by notice to the Company and the Selling Shareholders at any
time on or prior to the First Closing Date and, with respect to the Option
Shares, at any time prior to the Second Closing Date, which termination shall be
without liability on the part of any party to any other party, except that
Section 5 (Payment of Expenses), Section 6 (Reimbursement of Underwriters'
Expenses), Section 7 (Indemnification and Contribution) and Section 10
(Representations and Indemnities to Survive Delivery) shall at all times be
effective and shall survive such termination.

     Section 5. Payment of Expenses. The Company agrees to pay all costs, fees
and expenses incurred in connection with the performance of its obligations
hereunder and in connection with the transactions contemplated hereby, including
without limitation (i) all expenses incident to the issuance and delivery of the
Common Shares (including all printing and engraving costs), (ii) all reasonable
fees and expenses of the registrar and transfer agent of the Common Stock, (iii)
all necessary issue, transfer and other stamp taxes in connection with the
issuance and sale of the Shares to the Underwriters, (iv) all fees and expenses
of the Company's counsel, independent public or certified public accountants and
other advisors, (v) all reasonable costs and expenses incurred in connection
with the preparation, printing, filing, shipping and distribution of the
Registration Statement (including financial statements, exhibits, schedules,
consents and certificates of experts), each preliminary prospectus and the
Prospectus, and all amendments and supplements thereto, and this Agreement, (vi)
all filing fees, attorneys' fees and expenses incurred by the Company or the
Underwriters in connection with qualifying or registering (or obtaining
exemptions from the qualification or registration of) all or any part of the
Shares for offer and sale under the state securities or blue sky laws or the
provincial securities laws of Canada or any other country, and, if requested by
the Representatives, preparing and printing a "Blue Sky Survey", an
"International Blue Sky Survey" or other memorandum, and any supplements
thereto, advising the Underwriters of such qualifications, registrations and
exemptions, (vii) the filing fees incident to, and the reasonable fees and
expenses of counsel for the Underwriters in connection with, the NASD

                                       22
<PAGE>

review and approval of the Underwriters' participation in the offering and
distribution of the Common Shares (viii) the fees and expenses associated with
listing the Common Shares on the Nasdaq National Market, (ix) all costs and
expenses incident to the travel and accommodation of the Company's employees on
the "roadshow", and (x) all other fees, costs and expenses referred to in Item
13 of Part II of the Registration Statement. Except as provided in this Section
5, Section 6, and Section 7 hereof, the Underwriters shall pay their own
expenses, including the fees and disbursements of their counsel.

          The Selling Shareholders further agree with each Underwriter to pay
(directly or by reimbursement) all fees and expenses incident to the performance
of their obligations under this Agreement which are not otherwise specifically
provided for herein, including but not limited to (i) fees and expenses of
counsel and other advisors for such Selling Shareholders, (ii) fees and expenses
of the Custodian and (iii) expenses and taxes incident to the sale and delivery
of the Common Shares to be sold by such Selling Shareholders to the Underwriters
hereunder (which taxes, if any, may be deducted by the Custodian under the
provisions of Section 2 of this Agreement).

          This Section 5 shall not affect or modify any separate, valid
agreement relating to the allocation of payment of expenses between the Company,
on the one hand, and the Selling Shareholders, on the other hand.

     Section 6.  Reimbursement of Underwriters' Expenses. If this Agreement is
terminated by the Representatives pursuant to Section 4, Section 8, Section 9 or
Section 15, or if the sale to the Underwriters of the Shares on the First
Closing Date is not consummated because of any refusal, inability or failure on
the part of the Company or the Selling Shareholders to perform any agreement
herein or to comply with any provision hereof, the Company agrees to reimburse
the Representatives and the other Underwriters (or such Underwriters as have
terminated this Agreement with respect to themselves), severally, upon demand
for all out-of-pocket expenses that shall have been reasonably incurred by the
Representatives and the Underwriters in connection with the proposed purchase
and the offering and sale of the Shares, including but not limited to fees and
disbursements of counsel, printing expenses, travel and accommodation expenses,
postage, facsimile and telephone charges.

     Section 7.  Indemnification and Contribution.

     (a)  Indemnification of the Underwriters.

     (1)  The Company agrees to indemnify and hold harmless each Underwriter,
its officers and employees, and each person, if any, who controls any
Underwriter within the meaning of the Securities Act and the Exchange Act
against any loss, claim, damage, liability or expense, as incurred, to which
such Underwriter or such controlling person may become subject, under the
Securities Act, the Exchange Act or other federal or state statutory law or
regulation, or at common law or otherwise (including in settlement of any
litigation, if such settlement is effected with the written consent of the
Company, which consent shall not be unreasonably withheld), insofar as such
loss, claim, damage, liability or expense (or actions in respect thereof as
contemplated below) arises out of or is based upon (i) any untrue statement or
alleged untrue statement of a material fact contained in the Registration
Statement, or any amendment thereto, including any information deemed to be a
part thereof pursuant to Rule 430A under the Securities Act, or the omission or
alleged omission therefrom of a

                                       23
<PAGE>

material fact required to be stated therein or necessary to make the statements
therein not misleading; or (ii) any untrue statement or alleged untrue statement
of a material fact contained in any preliminary prospectus or the Prospectus (or
any amendment or supplement thereto), or the omission or alleged omission
therefrom of a material fact necessary in order to make the statements therein,
in the light of the circumstances under which they were made, not misleading; or
(iii) in whole or in part, any inaccuracy in the representations and warranties
of the Company contained herein; or (iv) in whole or in part upon any failure of
the Company  to perform its obligations hereunder or under law; or (v) any
untrue statement or alleged untrue statement of any material fact contained in
any audio or visual materials provided by the Company or based upon written
information furnished by or on behalf of the Company including, without
limitation, slides, videos, films or tape recordings, used in connection with
the marketing of the Shares or (vi) any act or failure to act or any alleged act
or failure to act by any Underwriter in connection with, or relating in any
manner to, the Shares or the offering contemplated hereby, and which is included
as part of or referred to in any loss, claim, damage, liability or action
arising out of or based upon any matter covered by clause (i), (ii), (iii), (iv)
or (v) above, provided that the Company shall not be liable under this clause
(vi) to the extent that a court of competent jurisdiction shall have determined
by a final judgment that such loss, claim, damage, liability or action resulted
directly from any such acts or failures to act undertaken or omitted to be taken
by such Underwriter through its bad faith or willful misconduct; and to
reimburse each Underwriter and each such controlling person for any and all
expenses (including the fees and disbursements of counsel chosen by Robertson
Stephens) as such expenses are reasonably incurred by such Underwriter or such
controlling person in connection with investigating, defending, settling,
compromising or paying any such loss, claim, damage, liability, expense or
action; provided, however, that the foregoing indemnity agreement shall not
        --------  -------
apply to any loss, claim, damage, liability or expense to the extent, but only
to the extent, arising out of or based upon any untrue statement or alleged
untrue statement or omission or alleged omission made in reliance upon and in
conformity with written information furnished to the Company by the
Representatives expressly for use in the Registration Statement, any preliminary
prospectus or the Prospectus (or any amendment or supplement thereto); provided,
                                                                       --------
further, that with respect to any preliminary prospectus, the foregoing
-------
indemnity agreement shall not inure to the benefit of any Underwriter from whom
the person asserting any loss, claim, damage, liability or expense purchased
Shares, or any person controlling such Underwriter, if copies of the Prospectus
were timely delivered to the Underwriter pursuant to Section 2 and 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 law so to have been delivered,
and if the Prospectus (as so amended or supplemented) would have cured the
defect giving rise to such loss, claim, damage, liability or expense. The
indemnity agreement set forth in this Section 7(a) shall be in addition to any
liabilities that the Company may otherwise have.

     (2) Each of the Selling Shareholders, severally and not jointly, agrees to
indemnify and hold harmless each Underwriter, its officers and employees, and
each person, if any, who controls any Underwriter within the meaning of the
Securities Act and the Exchange Act against any loss, claim, damage, liability
or expense, as incurred, to which such Underwriter or such controlling person
may become subject, under the Securities Act, the Exchange Act or other federal
or state statutory law or regulation, or at common law or otherwise (including
in settlement of any litigation, if such settlement is effected with the written
consent of the Company, which consent shall not be unreasonably withheld),
insofar as such loss, claim, damage, liability or expense (or actions in respect
thereof as contemplated below) arises out of

                                       24
<PAGE>

or is based upon (i) any untrue statement or alleged untrue statement of a
material fact contained in the Registration Statement, or any amendment thereto,
including any information deemed to be a part thereof pursuant to Rule 430A
under the Securities Act, or the omission or alleged omission therefrom of a
material fact required to be stated therein or necessary to make the statements
therein not misleading; or (ii) any untrue statement or alleged untrue statement
of a material fact contained in any preliminary prospectus or the Prospectus (or
any amendment or supplement thereto), or the omission or alleged omission
therefrom of a material fact necessary in order to make the statements therein,
in the light of the circumstances under which they were made, not misleading, in
the case of subparagraphs (i) and (ii) of this Section 7(a)(2) to the extent,
but only to the extent, that such untrue statement or alleged untrue statement
or omission or alleged omission was made in reliance upon and in conformity with
written information furnished to the Company or such Underwriter by such Selling
Shareholder directly or through such Selling Shareholder's representatives,
specifically for inclusion in the Registration Statement, any preliminary
Prospectus or the Prospectus (or any amendment or supplement thereto); or (iii)
in whole or in part, any inaccuracy in the representations and warranties of the
Selling Shareholders contained herein; or (iv) in whole or in part, any failure
of the Selling Shareholders to perform their respective obligations hereunder or
under law; or (v) any act or failure to act or any alleged act or failure to act
by any Underwriter in connection with, or relating in any manner to, the Shares
or the offering contemplated hereby, and which is included as part of or
referred to in any loss, claim, damage, liability or action arising out of or
based upon any matter covered by clause (i), (ii), (iii) or (iv) above, provided
that the Selling Shareholders shall not be liable under this clause (v) to the
extent that a court of competent jurisdiction shall have determined by a final
judgment that such loss, claim, damage, liability or action resulted directly
from any such acts or failures to act undertaken or omitted to be taken by such
Underwriter through its bad faith or willful misconduct; and to reimburse each
Underwriter and each such controlling person for any and all expenses (including
the fees and disbursements of counsel chosen by Robertson Stephens) as such
expenses are reasonably incurred by such Underwriter or such controlling person
in connection with investigating, defending, settling, compromising or paying
any such loss, claim, damage, liability, expense or action; provided, however,
                                                            --------  -------
that the foregoing indemnity agreement shall not apply to any loss, claim,
damage, liability or expense to the extent, but only to the extent, arising out
of or based upon any untrue statement or alleged untrue statement or omission or
alleged omission made in reliance upon and in conformity with written
information furnished to the Selling Shareholders by the Representatives
expressly for use in the Registration Statement, any preliminary prospectus or
the Prospectus (or any amendment or supplement thereto); and provided, further,
                                                             --------  -------
that with respect to any preliminary prospectus, the foregoing indemnity
agreement shall not inure to the benefit of any Underwriter from whom the person
asserting any loss, claim, damage, liability or expense purchased Shares, or any
person controlling such Underwriter, if copies of the Prospectus were timely
delivered to the Underwriter pursuant to Section 2 and 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 law so to have been delivered and if
the Prospectus (as so amended or supplemented) would have cured the defect
giving rise to such loss, claim, damage, liability or expense. The indemnity
agreement set forth in this Section 7(a) shall be in addition to any liabilities
that the Selling Shareholders may otherwise have; and provided, further, that
                                                      --------  -------
the liability of each Selling Shareholder under the foregoing indemnity
agreement shall be limited to an amount equal to the initial public offering
price of the Shares sold by such Selling Shareholder, less the underwriting
discount, as set forth on the front cover page of the Prospectus.

                                       25
<PAGE>

     (b) Indemnification of the Company, its Directors, Officers and Selling
Shareholders.  Each Underwriter agrees, severally and not jointly, to indemnify
and hold harmless the Company, each of its directors, each of its officers who
signed the Registration Statement, the Selling Shareholders and each person, if
any, who controls the Company or any Selling Shareholder within the meaning of
the Securities Act or the Exchange Act, against any loss, claim, damage,
liability or expense, as incurred, to which the Company, or any such director,
officer, Selling Shareholder or controlling person may become subject, under the
Securities Act, the Exchange Act, or other federal or state statutory law or
regulation, or at common law or otherwise (including in settlement of any
litigation, if such settlement is effected with the written consent of such
Underwriter), insofar as such loss, claim, damage, liability or expense (or
actions in respect thereof as contemplated below) arises out of or is based upon
any untrue or alleged untrue statement of a material fact contained in the
Registration Statement, any preliminary prospectus or the Prospectus (or any
amendment or supplement thereto), or arises out of or is based upon the omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading, in each case
to the extent, but only to the extent, that such untrue statement or alleged
untrue statement or omission or alleged omission was made in the Registration
Statement, any preliminary prospectus, the Prospectus (or any amendment or
supplement thereto), in reliance upon and in conformity with written information
furnished to the Company and the Selling Shareholders by the Representatives
expressly for use therein; and to reimburse the Company, or any such director,
officer, Selling Shareholder or controlling person for any legal and other
expense reasonably incurred by the Company, or any such director, officer,
Selling Shareholder or controlling person in connection with investigating,
defending, settling, compromising or paying any such loss, claim, damage,
liability, expense or action. The indemnity agreement set forth in this Section
7(b) shall be in addition to any liabilities that each Underwriter may otherwise
have.

     (c) Information Provided by the Underwriters.  The Company and each of the
Selling Shareholders, and each person, if any, who controls the Company within
the meaning of the Securities Act or the Exchange Act, hereby acknowledges that
the only information that the Underwriters have furnished to the Company
expressly for use in the Registration Statement, any preliminary prospectus or
the Prospectus (or any amendment or supplement thereto) are the statements set
forth in the table in the first paragraph, the last paragraph and the paragraphs
identified by "--Syndicate Short Sales," "-- Stabilization" and "-- Passive
Market Making" under the caption "Underwriting" in the Prospectus; and the
                                  ------------
Underwriters confirm that such statements are correct.

     (d) Notifications and Other Indemnification Procedures.  Promptly after
receipt by an indemnified party under this Section 7 of notice of the
commencement of any action, such indemnified party will, if a claim in respect
thereof is to be made against an indemnifying party under this Section 7, notify
the indemnifying party in writing of the commencement thereof, but the omission
so to notify the indemnifying party will not relieve it from any liability which
it may have to any indemnified party for contribution or otherwise than under
the indemnity agreement contained in this Section 7 or to the extent it is not
prejudiced as a proximate result of such failure.  In case any such action is
brought against any indemnified party and such indemnified party seeks or
intends to seek indemnity from an indemnifying party, the indemnifying party
will be entitled to participate in, and, to the extent that it shall elect,
jointly with all other indemnifying parties similarly notified, by written
notice delivered to the indemnified party promptly after receiving the aforesaid
notice from such indemnified party, to assume the defense thereof with counsel
reasonably satisfactory to such indemnified party;

                                       26
<PAGE>

provided, however, if the defendants in any such action include both the
--------  -------
indemnified party and the indemnifying party and the indemnified party shall
have reasonably concluded that a conflict may arise between the positions of the
indemnifying party and the indemnified party in conducting the defense of any
such action or that there may be legal defenses available to it and/or other
indemnified parties which are different from or additional to those available to
the indemnifying party, the indemnified party or parties shall have the right to
select separate counsel to assume such legal defenses and to otherwise
participate in the defense of such action on behalf of such indemnified party or
parties. Upon receipt of notice from the indemnifying party to such indemnified
party of such indemnifying party's election so to assume the defense of such
action and approval by the indemnified party of counsel, the indemnifying party
will not be liable to such indemnified party under this Section 7 for any legal
or other expenses subsequently incurred by such indemnified party in connection
with the defense thereof unless (i) the indemnified party shall have employed
separate counsel in accordance with the proviso to the next preceding sentence
(it being understood, however, that the indemnifying party shall not be liable
for the expenses of more than one separate counsel (together with local
counsel), approved by the indemnifying party (Robertson Stephens in the case of
Section 7(b) and Section 8), representing the indemnified parties who are
parties to such action), (ii) the indemnifying party shall not have employed
counsel satisfactory to the indemnified party to represent the indemnified party
within a reasonable time after notice of commencement of the action, or (iii)
the indemnifying party has authorized the employment of counsel for the
indemnified party at the expense of the indemnifying party, in each of which
cases the fees and expenses of counsel shall be at the expense of the
indemnifying party.

     (e) Settlements.  The indemnifying party under this Section 7 shall not be
liable for any settlement of any proceeding effected without its written
consent, which consent shall not be unreasonably withheld, but if settled with
such consent or if there be a final judgment for the plaintiff, the indemnifying
party agrees to indemnify the indemnified party against any loss, claim, damage,
liability or expense by reason of such settlement or judgment.  Notwithstanding
the foregoing sentence, if at any time an indemnified party shall have requested
an indemnifying party to reimburse the indemnified party for fees and expenses
of counsel as contemplated by Section 7(d) hereof, the indemnifying party 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 60 days
after receipt by such indemnifying party of the aforesaid request and (ii) such
indemnifying party shall not have reimbursed the indemnified party in accordance
with such request prior to the date of such settlement.  No indemnifying party
shall, without the prior written consent of the indemnified party, effect any
settlement, compromise or consent to the entry of judgment in any pending or
threatened action, suit or proceeding in respect of which any indemnified party
is or could have been a party and indemnity was or could have been sought
hereunder by such indemnified party, unless such settlement, compromise or
consent includes (i) an unconditional release of such indemnified party from all
liability on claims that are the subject matter of such action, suit or
proceeding and (ii) does not include a statement as to or an admission of fault,
culpability or a failure to act by or on behalf of any indemnified party.

     (f) Contribution.  If the indemnification provided for in this Section 7 is
applicable by its terms but unavailable to or insufficient to hold harmless an
indemnified party under Section 7(a) or (b) above in respect of any losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
then each indemnifying party shall contribute to the aggregate amount paid or
payable by such indemnified party in such proportion as is appropriate to

                                       27
<PAGE>

reflect the relative benefits received by such party on the one hand and the
Underwriters on the other from the offering of the Shares. If, however, the
allocation provided by the immediately preceding sentence is not permitted by
applicable law then each indemnifying party shall contribute to such amount paid
or payable by such indemnified party in such proportion as is appropriate to
reflect not only such relative benefits but also the relative fault of the such
party on the one hand and the Underwriters on the other in connection with the
statements or omissions which resulted in such losses, claims, damages or
liabilities, (or actions or proceedings in respect thereof), as well as any
other relevant equitable considerations. The relative benefits received by the
Company or the Selling Shareholder, as applicable, on the one hand, and the
Underwriters on the other, shall be deemed to be in the same proportion as the
total net proceeds (before deducting expenses) received by the Company or the
Selling Shareholder, as applicable, from the sale of the Shares sold by it in
the offering bears to the total underwriting discounts and commissions received
by the Underwriters in connection with the sale of such Shares, in each case as
described in the Prospectus. The relative fault 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 and the Selling Shareholders on
the one hand or the Underwriters on the other and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission.

          The Company, each Selling Shareholder and the Underwriters agree that
it would not be just and equitable if contributions pursuant to this Section
7(f) were determined by pro rata allocation (even if the Underwriters were
treated as one entity for such purpose) or by any other method of allocation
which does not take account of the equitable considerations referred to above in
this Section 7(f).  The amount paid or payable by an indemnified party as a
result of the losses, claims, damages or liabilities (or actions or proceedings
in respect thereof) referred to above in this Section 7(f) shall be deemed to
include any legal or other expenses reasonably incurred by such indemnified
party in connection with investigating or defending any such action or claim.
Notwithstanding the provisions of this subsection (f), (i) no Underwriter shall
be required to contribute any amount in excess of the underwriting discounts and
commissions applicable to the Shares purchased by such Underwriter and (ii) 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 in this Section 7(f) to contribute are several in proportion to
their respective underwriting obligations and not joint.

     (g) Timing of Any Payments of Indemnification.  Any losses, claims,
damages, liabilities or expenses for which an indemnified party is entitled to
indemnification or contribution under this Section 7 shall be paid by the
indemnifying party to the indemnified party as such losses, claims, damages,
liabilities or expenses are incurred, but in all cases, no later than forty-five
(45) days of invoice to the indemnifying party.

     (h) Survival.  The indemnity and contribution agreements contained in this
Section 7 and the representation and warranties set forth in this Agreement
shall remain operative and in full force and effect, regardless of (i) any
investigation made by or on behalf of any Underwriter or any person controlling
any Underwriter, the Company, its directors or officers, any Selling Shareholder
or any persons controlling the Company, (ii) acceptance of any Shares and
payment therefor hereunder, and (iii) any termination of this Agreement.  A
successor to any Underwriter, or to the Company, its directors or officers, any
Selling

                                       28
<PAGE>

Shareholder or any person controlling the Company, shall be entitled to the
benefits of the indemnity, contribution and reimbursement agreements contained
in this Section 7.

     (i) Acknowledgements of Parties.  The parties to this Agreement hereby
acknowledge that they are sophisticated business persons who were represented by
counsel during the negotiations regarding the provisions hereof including,
without limitation, the provisions of this Section 7, and are fully informed
regarding said provisions.  They further acknowledge that the provisions of this
Section 7 fairly allocate the risks in light of the ability of the parties to
investigate the Company and its business in order to assure that adequate
disclosure is made in the Registration Statement and Prospectus as required by
the Securities Act and the Exchange Act.

     Section 8.  Default of One or More of the Several Underwriters. If, on the
First Closing Date or the Second Closing Date, as the case may be, any one or
more of the several Underwriters shall fail or refuse to purchase Shares that it
or they have agreed to purchase hereunder on such date, and the aggregate number
of Common Shares which such defaulting Underwriter or Underwriters agreed but
failed or refused to purchase does not exceed 10% of the aggregate number of the
Shares to be purchased on such date, the other Underwriters shall be obligated,
severally, in the proportions that the number of Firm Common Shares set forth
opposite their respective names on Schedule A bears to the aggregate number of
                                   ----------
Firm Shares set forth opposite the names of all such non-defaulting
Underwriters, or in such other proportions as may be specified by the
Representatives with the consent of the non-defaulting Underwriters, to purchase
the Shares which such defaulting Underwriter or Underwriters agreed but failed
or refused to purchase on such date. If, on the First Closing Date or the Second
Closing Date, as the case may be, any one or more of the Underwriters shall fail
or refuse to purchase Shares and the aggregate number of Shares with respect to
which such default occurs exceeds 10% 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 48 hours after
such default, this Agreement shall terminate without liability of any party to
any other party except that the provisions of Section 5, Section 6 and Section 7
shall at all times be effective and shall survive such termination. In any such
case either the Representatives or the Company shall have the right to postpone
the First Closing Date or the Second Closing Date, as the case may be, but in no
event for longer than seven days in order that the required changes, if any, to
the Registration Statement and the Prospectus or any other documents or
arrangements may be effected.

          As used in this Agreement, the term "Underwriter" shall be deemed to
                                               -----------
include any person substituted for a defaulting Underwriter under this Section
8.  Any action taken under this Section 8 shall not relieve any defaulting
Underwriter from liability in respect of any default of such Underwriter under
this Agreement.

     Section 9.  Termination of this Agreement. This Agreement may be terminated
by the Representatives by notice given to the Company and the Selling
Shareholders if (a) at any time after the execution and delivery of this
Agreement and prior to the First Closing Date (i) trading or quotation in any of
the Company's securities shall have been suspended or limited by the Commission
or by the Nasdaq Stock Market, or trading in securities generally on either the
Nasdaq Stock Market or the New York Stock Exchange shall have been suspended or
limited, or minimum or maximum prices shall have been generally established on
any of such stock exchanges by the Commission or the NASD; (ii) a general
banking moratorium shall have been declared by any of federal, New York,
Virginia or California authorities; (iii) there

                                       29
<PAGE>

shall have occurred any outbreak or escalation of national or international
hostilities or any crisis or calamity, or any change in the United States or
international financial markets, or any substantial change or development
involving a prospective change in United States' or international political,
financial or economic conditions, as in the judgment of the Representatives is
material and adverse and makes it impracticable or inadvisable to market the
Common Shares in the manner and on the terms contemplated in the Prospectus or
to enforce contracts for the sale of securities; (iv) in the judgment of the
Representatives there shall have occurred any Material Adverse Change; or (v)
the Company shall have sustained a loss by strike, fire, flood, earthquake,
accident or other calamity of such character as in the judgment of the
Representatives may interfere materially with the conduct of the business and
operations of the Company regardless of whether or not such loss shall have been
insured or (b) in the case of any of the events specified 9(a)(i)-(v), such
event singly or together with any other event, makes it, in your judgment,
impracticable or inadvisable to market the Common Shares in the manner and on
the terms contemplated in the Prospectus. Any termination pursuant to this
Section 9 shall be without liability on the part of (x) the Company or the
Selling Shareholders to any Underwriter, except that the Company and the Selling
Shareholders shall be obligated to reimburse the expenses of the Representatives
and the Underwriters pursuant to Sections 5 and 6 hereof, (y) any Underwriter to
the Company or any person controlling the Company or the Selling Shareholders,
or (z) of any party hereto to any other party except that the provisions of
Section 7 shall at all times be effective and shall survive such termination.

     Section 10.  Representations and Indemnities to Survive Delivery. The
respective indemnities, agreements, representations, warranties and other
statements of the Company or any person controlling the company, of its
officers, of the Selling Shareholders and of the several Underwriters set forth
in or made pursuant to this Agreement will remain in full force and effect,
regardless of any investigation made by or on behalf of any Underwriter or the
Company or any of its or their partners, officers or directors or any
controlling person, or the Selling Shareholders, as the case may be, and will
survive delivery of and payment for the Shares sold hereunder and any
termination of this Agreement.

     Section 11.  Notices. All communications hereunder shall be in writing and
shall be mailed, hand delivered or telecopied and confirmed to the parties
hereto as follows:

If to the Representatives:

     ROBERTSON STEPHENS, INC.
     555 California Street
     San Francisco, California 94104
     Facsimile: (415) 676-2675
     Attention: General Counsel

If to the Company:

     INSMED INCORPORATED
     800 E. Leigh Street
     Richmond, VA 23219
     Facsimile: (804) 827-0520
     Attention: Chief Financial Officer

with a copy to:

                                       30
<PAGE>

     Hunton & Williams
     Riverfront Plaza, East Tower
     951 East Byrd Street
     Richmond, VA 23219
     Facsimile: (804) 788-8218
     Attention: T. Justin Moore III, Esq.

If to the Selling Shareholders, to its address as
shown on Schedule B, with a copy to:

     INSMED INCORPORATED
     800 E. Leigh Street
     Richmond, VA 23219
     Facsimile: (804) 827-0520
     Attention: Chief Financial Officer

Any party hereto may change the address for receipt of communications by giving
written notice to the others.

     Section 12.  Successors. This Agreement will inure to the benefit of and be
binding upon the parties hereto, including any substitute Underwriters pursuant
to Section 8 hereof, and to the benefit of the employees, officers and directors
and controlling persons referred to in Section 7, and to their respective
successors, and personal representatives, and no other person will have any
right or obligation hereunder.  The term "successors" shall not include any
                                          ----------
purchaser of the Shares as such from any of the Underwriters merely by reason of
such purchase.

     Section 13.  Partial Unenforceability. The invalidity or unenforceability
of any Section, paragraph or provision of this Agreement shall not affect the
validity or enforceability of any other Section, paragraph or provision hereof.
If any Section, paragraph or provision of this Agreement is for any reason
determined to be invalid or unenforceable, there shall be deemed to be made such
minor changes (and only such minor changes) as are necessary to make it valid
and enforceable.

     Section 14.  Governing Law Provisions.

     (a) Governing Law.  This agreement shall be governed by and construed in
accordance with the internal laws of the state of New York applicable to
agreements made and to be performed in such state.

     (b) Consent to Jurisdiction.  Any legal suit, action or proceeding arising
out of or based upon this Agreement or the transactions contemplated hereby
("Related Proceedings") may be instituted in the federal courts of the United
  -------------------
States of America located in the City and County of San Francisco or the courts
of the State of California in each case located in the City and County of San
Francisco (collectively, the "Specified Courts"), and each party irrevocably
                              ----------------
submits to the personal jurisdiction (except for proceedings instituted in
regard to the enforcement of a judgment of any such court (a "Related
                                                              -------
Judgment"), as to which such jurisdiction is non-exclusive) of such courts in
any such suit, action or proceeding.  Service of any process, summons, notice or
document by mail to such party's address set forth above shall be effective
service of process for any suit, action or other proceeding brought in any

                                       31
<PAGE>

such court. The parties irrevocably and unconditionally waive any objection to
the laying of venue of any suit, action or other proceeding in the Specified
Courts and irrevocably and unconditionally waive and agree not to plead or claim
in any such court that any such suit, action or other proceeding brought in any
such court has been brought in an inconvenient forum. Each party not located in
the United States irrevocably appoints CT Corporation System, which currently
maintains a San Francisco office at 49 Stevenson Street, San Francisco,
California 94105, United States of America, as its agent to receive service of
process or other legal summons for purposes of any such suit, action or
proceeding that may be instituted in any state or federal court in the City and
County of San Francisco.

     Section 15.  Failure of One or More of the Selling Shareholders to Sell and
Deliver Common Shares. If one or more of the Selling Shareholders shall fail to
sell and deliver to the Underwriters the Shares to be sold and delivered by such
Selling Shareholders at the First Closing Date pursuant to this Agreement, then
the Underwriters may at their option, by written notice from the Representatives
to the Company and the Selling Shareholders, either (i) terminate this Agreement
without any liability on the part of any Underwriter or, except as provided in
Sections 5, 6, and 7 hereof, the Company or the Selling Shareholders, or (ii)
purchase the shares which the Company and other Selling Shareholders have agreed
to sell and deliver in accordance with the terms hereof. If one or more of the
Selling Shareholders shall fail to sell and deliver to the Underwriters the
Shares to be sold and delivered by such Selling Shareholders pursuant to this
Agreement at the First Closing Date or the Second Closing Date, then the
Underwriters shall have the right, by written notice from the Representatives to
the Company and the Selling Shareholders, to postpone the First Closing Date or
the Second Closing Date, as the case may be, but in no event for longer than
seven days in order that the required changes, if any, to the Registration
Statement and the Prospectus or any other documents or arrangements may be
effected.

     Section 16.  General Provisions. This Agreement constitutes the entire
agreement of the parties to this Agreement and supersedes all prior written or
oral and all contemporaneous oral agreements, understandings and negotiations
with respect to the subject matter hereof. This Agreement may be executed in two
or more counterparts, each one of which shall be an original, with the same
effect as if the signatures thereto and hereto were upon the same instrument.
This Agreement may not be amended or modified unless in writing by all of the
parties hereto, and no condition herein (express or implied) may be waived
unless waived in writing by each party whom the condition is meant to benefit.
Section headings herein are for the convenience of the parties only and shall
not affect the construction or interpretation of this Agreement.

        [The remainder of this page has been intentionally left blank.]

                                       32
<PAGE>

          If the foregoing is in accordance with your understanding of our
agreement, please sign and return to the Company and the Custodian the enclosed
copies hereof, whereupon this instrument, along with all counterparts hereof,
shall become a binding agreement in accordance with its terms.

                                  Very truly yours,

                                           INSMED INCORPORATED
                                        By:

                                           __________________________________
                                           Michael D. Baer
                                           Chief Financial Officer

                                        TICONDEROGA PARTNERS III, L.P.

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

                                        BIOTECHNOLOGY DEVELOPMENT FUND, L.P.

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

                                        BIOTECHNOLOGY DEVELOPMENT FUND III, L.P.

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

                                        VERON INTERNATIONAL LTD.

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

                      (Signatures Continued on Next Page)

                                       33
<PAGE>

                                        BOSTON UNIVERSITY NOMINEE PARTNERSHIP

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

                                        QUANTUM PARTNERS LDC

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

                                        GEOFFREY ALLAN

                                        By:_________________________________

                                           Name:____________________________

                                           Title:___________________________

          The foregoing Underwriting Agreement is hereby confirmed and accepted
by the Representatives as of the date first above written.

ROBERTSON STEPHENS, INC.
ROBERTSON STEPHENS INTERNATIONAL, LTD.
BANC OF AMERICA SECURITIES LLC
PRUDENTIAL SECURITIES INCORPORATED

On their behalf and on behalf of each of the several underwriters named in
Schedule A hereto.
----------

ROBERTSON STEPHENS, INC.
ROBERTSON STEPHENS INTERNATIONAL, LTD.
By:

      ____________________________
      Mitch Whiteford


                                       34
<PAGE>

                                   SCHEDULE A

<TABLE>
<CAPTION>
                   Underwriters                              Number of Firm Common
                   ------------                              Shares To be Purchased
                                                             ----------------------
<S>                                                         <C>
ROBERTSON STEPHENS, INC...................................           [___]
BANC OF AMERICA SECURITIES LLC............................           [___]
PRUDENTIAL SECURITIES INCORPORATED........................           [___]
[___].....................................................           [___]
[___].....................................................           [___]
                                                                ------------
     Total................................................        6,000,000
                                                                ============
</TABLE>

                                      S-A
<PAGE>

                                   SCHEDULE B

<TABLE>
<CAPTION>
                 Selling Shareholder                    Number of Firm Shares       Maximum Number of
                 -------------------                          to be Sold              Option Shares
                                                        ---------------------           to be Sold
                                                                                    -----------------
Principal Selling Shareholders
------------------------------
<S>                                                     <C>                         <C>
Biotechnology Development Fund, L.P.                               198,478                   188,032
570 High Street, Suite 201
Palo Alto, CA 94301
Attn:  Edgar G. Engleman

Biotechnology Development Fund III, L.P.                           110,094                   104,300
570 High Street, Suite 201
Palo Alto, CA 94301
Attn:  Edgar G. Engleman

Boston University Nominee Partnership                              107,183                   101,542
147 Bay State Road
Boston, MA 02215
Attn:  Kenneth G. Condon

Geoffrey Allan                                                      50,000                     -----
800 E. Leigh Street
Richmond, VA 23219

Other Selling Shareholders
--------------------------

Ticonderoga Partners III, L. P.                                    212,817                   201,616

20 William Street
Wellesley, MA 02481
Attn:  _______________

Veron International Ltd.                                           215,931                   204,566
Chinachem Golden Plaza
Top Floor
77, Mody Road
Tsim Sha Tsui East
Kowloon, Hong Kong
Attn:  _______________

Quantum Partners LDC                                               105,497                    99,944
Kaya Flaboyan 9
Willemstad, Curacao
Netherlands Antilles
Attn:  _______________
                                                               -----------                  --------
     Total:..........................                            1,000,000                   900,000
                                                               ===========                  ========
</TABLE>

                                      S-B
<PAGE>

                                   SCHEDULE C

          List of Shareholders Required to Execute Lock-Up Agreements


Name of Shareholder
-------------------

Geoffrey Allan
Michael D. Baer
Robert A. Falconer
Ronald D. Gunn
Kenneth G. Condon
Graham K. Crooke
Steinar J. Engelsen
Edgar G. Engleman
Ticonderoga Partners III, L.P.
Biotechnology Development Fund, L.P.
Biotechnology Development Fund III, L.P.
Veron International Ltd.
Boston University Nominee Partnership
Quantum Partners LDC
Elan International Services Ltd.
Vector Later-Stage Equity Fund II (QP), L.P.
Vector Later-Stage Equity Fund II, L.P.
Pequot International Fund, Inc.
Pequot Partners Fund, L.P.
Pequot Private Equity Fund, L.P
Pequot Offshore Private Equity Fund, Inc.
CLSP, L.P.
CLSP-SBS I, L.P.
CLSP-SBS II, L.P.

                                      S-C


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