Exhibit 10.1 — PURCHASE AGREEMENT

THIS PURCHASE AGREEMENT (“Agreement”) is made as of the 27th day of
February, 2006 by and among Avalon Pharmaceuticals, Inc., a Delaware corporation
(the “Company”), and the Investors set forth on the signature pages affixed
hereto (each an “Investor” and collectively the “Investors”).

Recitals

A. The Company and the Investors are executing and delivering this Agreement in
reliance upon the exemption from securities registration afforded by the
provisions of Regulation D (“Regulation D”), as promulgated by the U.S.
Securities and Exchange Commission (the “SEC”) under the Securities Act of 1933,
as amended; and

B. The Investors wish to purchase from the Company, and the Company wishes to
sell and issue to the Investors, upon the terms and conditions stated in this
Agreement, the number of shares (the “Shares”) of the Company’s Common Stock,
par value $0.01 per share (together with any securities into which such shares
may be reclassified, the “Common Stock”), determined in accordance with the
terms of this Agreement at a per share purchase price equal to $4.35 (the “Per
Share Purchase Price”); and

C. Contemporaneous with the sale of the Common Stock, the parties hereto will
execute and deliver a Registration Rights Agreement, in the form attached hereto
as Exhibit A (the “Registration Rights Agreement”), pursuant to which the
Company will agree to provide certain registration rights under the Securities
Act of 1933, as amended, and the rules and regulations promulgated thereunder,
and applicable state securities laws with respect to the Securities.

In consideration of the mutual promises made herein and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

1. Definitions. In addition to those terms defined above and elsewhere in this
Agreement, for the purposes of this Agreement, the following terms shall have
the meanings set forth below:

“Affiliate” means, with respect to any Person, any other Person which directly
or indirectly through one or more intermediaries Controls, is controlled by, or
is under common control with, such Person.

“Board” means the board of directors of the Company.

“Business Day” means a day, other than a Saturday or Sunday, on which banks in
New York City and San Francisco, California are open for the general transaction
of business.

“Company’s Knowledge” means the actual knowledge of the executive officers (as
defined in Rule 405 under the 1933 Act) of the Company, after due inquiry.

“Confidential Information” means trade secrets, confidential information and
know-how (including but not limited to ideas, formulae, compositions, processes,
procedures and techniques, research and development information, computer
program code, performance specifications, support documentation, drawings,
specifications, designs, business and marketing plans, and customer and supplier
lists and related information).

“Control” (including the terms “controlling”, “controlled by” or “under common
control with”) means the possession, direct or indirect, of the power to direct
or cause the direction of the management and policies of a Person, whether
through the ownership of voting securities, by contract or otherwise.

“Effective Date” means the date on which the initial Registration Statement is
declared effective by the SEC.

“Effectiveness Deadline” means the date on which the initial Registration
Statement is required to be declared effective by the SEC under the terms of the
Registration Rights Agreement.

“Independent Directors” means the directors of the Company who are “Independent
Directors,” as defined in The Nasdaq Stock Market’s Marketplace Rule 4200(a)(15)
as in effect on the date hereof.

“Intellectual Property” means all of the following: (i) patents, patent
applications, patent disclosures and inventions (whether or not patentable and
whether or not reduced to practice); (ii) trademarks, service marks, trade
dress, trade names, corporate names, logos, slogans and Internet domain names,
together with all goodwill associated with each of the foregoing;
(iii) copyrights and copyrightable works; (iv) registrations, applications and
renewals for any of the foregoing; and (v) proprietary computer software
(including but not limited to data, data bases and documentation).

“Material Adverse Effect” means a material adverse effect on (i) the assets,
liabilities, results of operations, condition (financial or otherwise),
business, or prospects of the Company, or (ii) the ability of the Company to
perform its obligations under the Transaction Documents.

“Nasdaq” means The Nasdaq Stock Market, Inc.

“Person” means an individual, corporation, partnership, limited liability
company, trust, business trust, association, joint stock company, joint venture,
sole proprietorship, unincorporated organization, governmental authority or any
other form of entity not specifically listed herein.

“Purchase Price” means the aggregate purchase price for the Shares to be
acquired by the Investors in accordance with the terms hereof.

“Registration Statement” has the meaning set forth in the Registration Rights
Agreement.

“SEC Filings” has the meaning set forth in Section 4.6.

“Securities” means the Shares.

“Subsidiary” of any Person means another Person, an amount of the voting
securities, other voting ownership or voting partnership interests of which is
sufficient to elect at least a majority of its Board of Directors or other
governing body (or, if there are no such voting interests, 50% or more of the
equity interests of which) is owned directly or indirectly by such first Person.

“Transaction Documents” means this Agreement and the Registration Rights
Agreement.

“1933 Act” means the Securities Act of 1933, as amended, or any successor
statute, and the rules and regulations promulgated thereunder.

“1934 Act” means the Securities Exchange Act of 1934, as amended, or any
successor statute, and the rules and regulations promulgated thereunder.

2. Purchase and Sale of the Shares. Subject to the terms and conditions of this
Agreement, on the Closing Date, each of the Investors shall severally, and not
jointly, purchase, and the Company shall sell and issue to the Investors, the
Shares in the respective amounts set forth opposite the Investors’ names on the
signature pages attached hereto in exchange for the Purchase Price, as specified
in Section 3 below.

3. Closing; Payment of Purchase Price. The closing (the “Closing”) of the
purchase and sale of the Shares shall take place on February 27, 2006 (the
“Closing Date”) at such time as the Company and the Investors shall mutually
agree. Upon confirmation that the other conditions to closing specified herein
have been satisfied or duly waived, on the Closing Date each Investor shall
cause a wire transfer in same day funds to be sent to the account of the Company
as instructed in writing by the Company, in an amount representing such
Investor’s pro rata portion of the Purchase Price as set forth on the signature
pages to this Agreement. Within five (5) Business Days after the Closing Date,
certificates evidencing the Shares shall be delivered by the Company to the
Investors. The Closing of the purchase and sale of the Shares shall take place
at the offices of Hogan & Hartson L.L.P., 111 South Calvert Street, Baltimore,
MD 21202 or at such other location and on such other date as the Company and the
Investors shall mutually agree.

4. Representations and Warranties of the Company. The Company hereby represents
and warrants to the Investors that, except as set forth in the schedules
delivered herewith (collectively, the “Disclosure Schedules”) or as disclosed in
the Company’s SEC Filings:

4. 1 Organization, Good Standing and Qualification. The Company is a corporation
duly organized, validly existing and in good standing under the laws of the
State of Delaware and has all requisite corporate power and authority to carry
on its business as now conducted and to own its properties. The Company is duly
qualified to do business as a foreign corporation and is in good standing in
each jurisdiction in which the conduct of its business or its ownership or
leasing of property makes such qualification or leasing necessary unless the
failure to so qualify has not had and would not reasonably be expected to have a
Material Adverse Effect. The Company has no Subsidiaries.

4.2 Authorization. The Company has full power and authority and has taken all
requisite action on the part of the Company, its officers, directors and
stockholders necessary for (i) the authorization, execution and delivery of the
Transaction Documents, (ii) the authorization of the performance of all
obligations of the Company hereunder and under the other Transaction Documents,
and (iii) the authorization, issuance (or reservation for issuance) and delivery
of the Securities. This Agreement constitutes, and the other Transaction
Documents will constitute when executed and delivered, the legal, valid and
binding obligations of the Company, enforceable against the Company in
accordance with their terms, subject to bankruptcy, insolvency, fraudulent
transfer, reorganization, moratorium and similar laws of general applicability,
relating to or affecting creditors’ rights generally.

4.3 Capitalization. Schedule 4.3 sets forth (a) the authorized capital stock of
the Company on the date hereof; (b) the number of shares of capital stock issued
and outstanding; (c) the number of shares of capital stock issuable pursuant to
the Company’s stock plans; and (d) the number of shares of capital stock
issuable and reserved for issuance pursuant to securities (other than the
Shares) exercisable for, or convertible into or exchangeable for any shares of
capital stock of the Company. All of the issued and outstanding shares of the
Company’s capital stock have been duly authorized and validly issued and are
fully paid, nonassessable and free of pre-emptive rights and were issued in full
compliance with applicable state and federal securities law and any rights of
third parties. No Person is entitled to pre-emptive or similar statutory or
contractual rights with respect to any securities of the Company. Except as
described on Schedule 4.3, there are no outstanding warrants, options,
convertible securities or other rights, agreements or arrangements of any
character under which the Company is or may be obligated to issue any equity
securities of any kind, and except as contemplated by this Agreement or in
connection with incentive compensation arrangements entered into by the Company
in the ordinary course of its business, the Company is not currently in
negotiations for the issuance of any equity securities of any kind. Except as
described on Schedule 4.3 and except for the Registration Rights Agreement,
there are no voting agreements, buy-sell agreements, option or right of first
purchase agreements or other agreements of any kind among the Company and any of
the securityholders of the Company relating to the securities of the Company
held by them. Except as described on Schedule 4.3 and except as provided in the
Registration Rights Agreement, no Person has the right to require the Company to
register any securities of the Company under the 1933 Act, whether on a demand
basis or in connection with the registration of securities of the Company for
its own account or for the account of any other Person.

The issuance and sale of the Securities hereunder will not obligate the Company
to issue shares of Common Stock or other securities to any other Person (other
than the Investors) and will not result in the adjustment of the exercise,
conversion, exchange or reset price of any outstanding security.

The Company does not have outstanding stockholder purchase rights or “poison
pill” or any similar arrangement in effect giving any Person the right to
purchase any equity interest in the Company upon the occurrence of certain
events.

4.4 Valid Issuance. The Shares have been duly and validly authorized and, when
issued and paid for pursuant to this Agreement, will be validly issued, fully
paid and nonassessable, and shall be free and clear of all encumbrances and
restrictions (other than those created by the Investors), except for
restrictions on transfer set forth in the Transaction Documents or imposed by
applicable securities laws.

4.5 Consents. Except as described on Schedule 4.5, the execution, delivery and
performance by the Company of the Transaction Documents and the offer, issuance
and sale of the Securities require no consent of, action by or in respect of, or
filing with, any Person, governmental body, agency, official or stockholders of
the Company other than filings that have been made pursuant to applicable state
securities laws and post-sale filings pursuant to applicable state and federal
securities laws which the Company undertakes to file within the applicable time
periods. Subject to the accuracy of the representations and warranties of each
Investor set forth in Section 5 hereof, the Company has taken all action
necessary to exempt (i) the issuance and sale of the Securities, and (ii) the
other transactions contemplated by the Transaction Documents from the provisions
of any stockholder rights plan or other “poison pill” arrangement, any
anti-takeover, business combination or control share law or statute binding on
the Company or to which the Company or any of its assets and properties may be
subject and any provision of the Company’s Certificate of Incorporation or
Bylaws that is or would reasonably be expected to become applicable to the
Investors as a result of the transactions contemplated hereby, including without
limitation, the issuance of the Securities and the ownership, disposition or
voting of the Securities by the Investors or the exercise of any right granted
to the Investors pursuant to this Agreement or the other Transaction Documents.

4.6 Delivery of SEC Filings; Business. The Company has made available to the
Investors through the EDGAR system, true and complete copies of the Company’s
most recent Quarterly Report on Form 10-Q for the quarter ended September 30,
2005 (the “10-Q”), Registration Statement on Form 8-A dated as of September 26,
2005 (“Form 8-A”), Registration Statement on Form S-1, including all amendments,
supplements and filings under Rule 424 thereof, dated May 3, 2005, as amended
(the “Form S-1”) and all other reports filed by the Company pursuant to the 1933
Act and 1934 Act since the initial filing of the Form S-1 and prior to the date
hereof (collectively, the “SEC Filings”). The SEC Filings are the only filings
required of the Company pursuant to the 1933 Act and 1934 Act for such period.
The Company is engaged in all material respects only in the business described
in the SEC Filings and the SEC Filings contain a complete and accurate
description in all material respects of the business of the Company.

4.7 Use of Proceeds. The net proceeds of the sale of the Shares hereunder shall
be used by the Company in accordance with the revised budget of the Company for
the calendar year 2006 adopted in accordance with Section 6.1(e), as such budget
may be amended or modified from time to time by the Board of Directors. Any net
proceeds remaining following use as provided in the prior sentence shall be used
by the Company for general corporate purposes.

4.8 No Material Adverse Change. Since September 30, 2005, except as identified
and described in the SEC Filings or as described on Schedule 4.8, there has not
been:

(i) any change in the consolidated assets, liabilities, financial condition or
operating results of the Company from that reflected in the financial statements
included in the Company’s Quarterly Report on Form 10-Q for the quarter ended
September 30, 2005, except for changes in the ordinary course of business which
have not had and would not reasonably be expected to have a Material Adverse
Effect, individually or in the aggregate;

(ii) any declaration or payment of any dividend, or any authorization or payment
of any distribution, on any of the capital stock of the Company, or any
redemption or repurchase of any securities of the Company;

(iii) any damage, destruction or loss, whether or not covered by insurance to
any assets or properties of the Company, in each case in excess of $25,000
individually or $50,000 in the aggregate;

(iv) any waiver, not in the ordinary course of business, by the Company of a
material right or of a material debt owed to it;

(v) any satisfaction or discharge of any lien, claim or encumbrance by the
Company, except in the ordinary course of business and which is not material to
the assets, properties, financial condition, operating results or business of
the Company (as such business is presently conducted);

(vi) (A) any change or amendment to the Company’s Certificate of Incorporation
or Bylaws, or (B) any material change to any material contract or arrangement
that requires the payment by any Person party thereto of at least $50,000 in the
aggregate in any fiscal year by which the Company is bound or to which any of
their respective assets or properties is subject, other than, in the case of
clause (B) above, any such change made in the ordinary course of business;

(vii) any material labor difficulties or labor union organizing activities with
respect to employees of the Company;

(viii) any material transaction entered into by the Company other than in the
ordinary course of business;

(ix) the loss of the services, termination or change of status of any key
employee, or material change in the composition or duties of the senior
management of the Company;

(x) the loss or threatened loss of any customer which has had or would
reasonably be expected to have a Material Adverse Effect; or

(xi) any other event or condition of any character that has had or would
reasonably be expected to have a Material Adverse Effect.

4.9 SEC Filings; S-3 Eligibility.

(a) At the time of filing thereof, the SEC Filings filed by the Company pursuant
to the 1934 Act complied as to form in all material respects with the
requirements of the 1934 Act and did not contain any untrue statement of a
material fact or omit to state any material fact necessary in order to make the
statements made therein, in the light of the circumstances under which they were
made, not misleading.

(b) Each registration statement and any amendment thereto filed by the Company
since January 1, 2005 pursuant to the 1933 Act and the rules and regulations
thereunder, as of the date such statement or amendment became effective,
complied as to form in all material respects with the 1933 Act and did not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary in order to make the statements
made therein not misleading; and each prospectus filed pursuant to Rule 424(b)
under the 1933 Act, as of its issue date and as of the closing of any sale of
securities pursuant thereto did not contain any untrue statement of a material
fact or omit to state any material fact required to be stated therein or
necessary in order to make the statements made therein, in the light of the
circumstances under which they were made, not misleading.

(c) The Company is eligible to use Form S-1 to register the Registrable
Securities (as such term is defined in the Registration Rights Agreement) for
sale by the Investors as contemplated by the Registration Rights Agreement. To
the Company’s Knowledge, no facts or circumstances currently exist or are
pending or threatened which would reasonably be expected to prevent the Company
from becoming eligible to use Form S-3 to register the Registrable Securities
for sale by the Investors on or after December 1, 2006.

4.10 No Conflict, Breach, Violation or Default. The execution, delivery and
performance of the Transaction Documents by the Company and the issuance and
sale of the Securities will not conflict with or result in a breach or violation
of any of the terms and provisions of, or constitute a default under (i) the
Company’s Certificate of Incorporation or the Company’s Bylaws, both as in
effect on the date hereof (true and complete copies of which have been made
available to the Investors through the EDGAR system), or (ii)(a) any statute,
rule, regulation or order of any governmental agency or body or any court,
domestic or foreign, having jurisdiction over the Company or any of its assets
or properties, or (b) any agreement or instrument to which the Company is a
party or by which the Company is bound or to which any of its assets or
properties is subject, except, in the case of clause (ii) above, for any
conflict, breach, violation or default that has not had or would not reasonably
be expected to have a Material Adverse Effect.

4.11 Tax Matters. The Company has timely prepared and filed all tax returns
required to have been filed by the Company with all appropriate governmental
agencies and timely paid all taxes shown thereon or otherwise owed by it, except
where the failure to make such payment or filing has not had or would not
reasonably be expected to have a Material Adverse Effect. The charges, accruals
and reserves on the books of the Company in respect of taxes for all fiscal
periods are adequate in all material respects, and there are no material unpaid
assessments against the Company for the assessment of any additional taxes,
penalties or interest for any fiscal period or audits by any federal, state or
local taxing authority except for any assessment which is not material to the
Company. All taxes and other assessments and levies that the Company is required
to withhold or to collect for payment have been duly withheld and collected and
paid to the proper governmental entity or third party when due, except for any
withholding, collection and payment that has not had or would not reasonably be
expected to have a Material Adverse Effect. There are no tax liens or claims
pending or, to the Company’s Knowledge, threatened against the Company or any of
its assets or property. There are no outstanding tax sharing agreements or other
such arrangements between the Company and any other corporation or entity.

4.12 Title to Properties. Except as disclosed in the SEC Filings, the Company
has good and marketable title to all real properties and all other properties
and assets owned by it, in each case free from liens, encumbrances and defects
that would materially affect the value thereof or materially interfere with the
use made thereof by them; and except as disclosed in the SEC Filings, the
Company holds any leased real or personal property under valid and enforceable
leases with no exceptions that would materially interfere with the use made
thereof by them.

4.13 Certificates, Authorities and Permits. The Company possess adequate
certificates, authorities or permits issued by appropriate governmental agencies
or bodies necessary to conduct the business now operated by it, except where the
failure to so possess has not had or would not reasonably be expected to have a
Material Adverse Effect, individually or in the aggregate, and the Company has
not received any written notice of proceedings relating to the revocation or
modification of any such certificate, authority or permit that, if determined
adversely to the Company, would reasonably be expected to have a Material
Adverse Effect, individually or in the aggregate.

4.14 Labor Matters.

(a) The Company is not a party to or bound by any collective bargaining
agreements or other agreements with labor organizations. The Company has not
violated in any material respect any laws, regulations, orders or contract
terms, affecting the collective bargaining rights of employees, labor
organizations or any laws, regulations or orders affecting employment
discrimination, equal opportunity employment, or employees’ health, safety,
welfare, wages and hours.

(b) (i) There are no labor disputes existing, or to the Company’s Knowledge,
threatened, involving strikes, slow-downs, work stoppages, job actions,
disputes, lockouts or any other disruptions of or by the Company’s employees,
(ii) there are no unfair labor practices or petitions for election pending or,
to the Company’s Knowledge, threatened before the National Labor Relations Board
or any other federal, state or local labor commission relating to the Company’s
employees, (iii) no demand for recognition or certification heretofore made by
any labor organization or group of employees is pending with respect to the
Company and (iv) to the Company’s Knowledge, the Company enjoys good labor and
employee relations with its employees and labor organizations.

(c) The Company is in compliance in all material respects with all applicable
laws respecting employment (including laws relating to classification of
employees and independent contractors) and employment practices, terms and
conditions of employment, wages and hours, and immigration and naturalization.
There are no claims pending against the Company before the Equal Employment
Opportunity Commission or any other administrative body or in any court
asserting any violation of Title VII of the Civil Rights Act of 1964, the Age
Discrimination Act of 1967, 42 U.S.C. §§ 1981 or 1983 or any other federal,
state or local Law, statute or ordinance barring discrimination in employment.

(d) Except as disclosed in the SEC Filings or as described on Schedule 4.14, the
Company is not a party to, or bound by, any employment or other contract or
agreement that contains any severance, termination pay or change of control
liability or obligation, including, without limitation, any “excess parachute
payment,” as defined in Section 2806(b) of the Internal Revenue Code.

(e) Except as specified in Schedule 4.14, to the Company’s Knowledge, each of
the Company’s employees is a Person who is either a United States citizen or a
permanent resident entitled to work in the United States. To the Company’s
Knowledge, the Company has no liability for the improper classification by the
Company of such employees as independent contractors or leased employees prior
to the Closing.

4.15 Intellectual Property. Except as described in Schedule 4.15:

(a) All Intellectual Property of the Company (whether owned by the Company or
licensed) and necessary for the conduct of its business is currently in
compliance with all legal requirements (including timely filings, proofs and
payments of fees) and, to the Company’s Knowledge, are valid and enforceable,
subject, in the case of any patent application, to any modification or other
action that may be taken by the Patent and Trademark Office. No Intellectual
Property of the Company which is necessary for the conduct of the Company’s
business as currently conducted has been or is now involved in any cancellation
or litigation, and, to the Company’s Knowledge, no such action is threatened. No
patent of the Company has been or is now involved in any interference, reissue,
re-examination or opposition proceeding.

(b) All of the licenses and sublicenses and consent, royalty or other agreements
concerning Intellectual Property which are necessary for the conduct of the
Company’s business as currently conducted to which the Company is a party or by
which any of its assets are bound (other than  generally commercially available,
non-custom, off-the-shelf software application programs having a retail
acquisition price of less than $50,000 per license) (collectively, “License
Agreements”) are valid and binding obligations of the Company and, to the
Company’s Knowledge, the other parties thereto, enforceable in accordance with
their terms, except to the extent that enforcement thereof may be limited by
bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or
other similar laws affecting the enforcement of creditors’ rights generally, and
there exists no event or condition which will result in a material violation or
breach of or constitute (with or without due notice or lapse of time or both) a
default by the Company under any such License Agreement.

(c) To the Company’s Knowledge, the Company owns or has the valid and
enforceable right to use all of the Intellectual Property that is necessary for
the conduct of the Company’s business as currently conducted and for the
ownership, maintenance and operation of the Company’s properties and assets,
free and clear of all liens, encumbrances, adverse claims or obligations to
license such owned Intellectual Property and Confidential Information known to
or created by the Company, other than licenses entered into in the ordinary
course of the Company’s business. To the Company’s Knowledge, the Company has a
valid and enforceable right to use all third party Confidential Information used
or held for use by the Company

(d) To the Company’s Knowledge, the conduct of the business as currently
conducted does not infringe or conflict with (collectively, “Infringe”) any
Intellectual Property rights of any third party, or violate any confidentiality
obligation owed by the Company to a third party. To the Company’s Knowledge, the
Intellectual Property and Confidential Information of the Company which are
necessary for the conduct of the Company’s business as currently conducted are
not being Infringed by any third party. There is no litigation or order pending
or outstanding or, to the Company’s Knowledge, threatened, that seeks to limit
or challenge the ownership, use, validity or enforceability of any Intellectual
Property or Confidential Information of the Company and the Company’s use of any
Intellectual Property or Confidential Information owned by a third party, and,
to the Company’s Knowledge, there is no valid basis for the same.

(e) The consummation of the transactions contemplated hereby and by the other
Transaction Documents will not result in the alteration, loss, impairment of or
restriction on the Company’s ownership or right to use any of the Intellectual
Property or Confidential Information which is necessary for the conduct of the
Company’s business as currently conducted.

(f) The Company has taken reasonable steps to protect the Company’s rights in
its Intellectual Property and Confidential Information. Each employee,
consultant and contractor who has had access to Confidential Information which
is necessary for the conduct of the Company’s business as currently conducted
has executed an agreement to maintain the confidentiality of such Confidential
Information and has executed appropriate agreements that are substantially
consistent with the Company’s standard forms thereof. Except under
confidentiality obligations, there has been no material disclosure of any of the
Company’s Confidential Information to any third party.

4.16 Environmental Matters. The Company (i) is not in violation of any statute,
rule, regulation, decision or order of any governmental agency or body or any
court, domestic or foreign, relating to the use, disposal or release of
hazardous or toxic substances or relating to the protection or restoration of
the environment or human exposure to hazardous or toxic substances
(collectively, “Environmental Laws”), (ii) does not own or operate any real
property contaminated with any substance that is subject to any Environmental
Laws, (iii) is not liable for any off-site disposal or contamination pursuant to
any Environmental Laws, or (iv) is not subject to any claim relating to any
Environmental Laws, in each case which violation, contamination, liability or
claim has had or would reasonably be expected to have a Material Adverse Effect,
individually or in the aggregate; and there is no pending or, to the Company’s
Knowledge, threatened investigation that might lead to such a claim.

4.17 Litigation. There are no pending actions, suits or proceedings against or
affecting the Company or any of its properties that have had or would reasonably
be expected to have a Material Adverse Effect, individually or in the aggregate;
and to the Company’s Knowledge, no such actions, suits or proceedings are
threatened or contemplated.

4.18 Financial Statements. The financial statements included in each SEC Filing
present fairly, in all material respects, the financial position of the Company
as of the dates shown and its results of operations and cash flows for the
periods shown, and such financial statements have been prepared in conformity
with United States generally accepted accounting principles applied on a
consistent basis (“GAAP”) (except as may be disclosed therein or in the notes
thereto, and, in the case of quarterly financial statements, as permitted by
Form 10-Q under the 1934 Act). Except as set forth in the financial statements
of the Company included in the SEC Filings filed prior to the date hereof, the
Company has not incurred any liabilities, contingent or otherwise, except those
incurred in the ordinary course of business, consistent (as to amount and
nature) with past practices since the date of such financial statements, none of
which, individually or in the aggregate, have had or would reasonably be
expected to have a Material Adverse Effect.

4.19 Insurance Coverage. The Company maintains in full force and effect
insurance coverage that is customary for comparably situated companies for the
business being conducted and properties owned or leased by the Company, and the
Company reasonably believes such insurance coverage to be adequate against all
liabilities, claims and risks against which it is customary for comparably
situated companies to insure.

4.20 Compliance with Nasdaq Continued Listing Requirements. The Company is in
compliance with applicable Nasdaq continued listing requirements. There are no
proceedings pending or, to the Company’s Knowledge, threatened against the
Company relating to the continued listing of the Common Stock on Nasdaq and the
Company has not received any notice of, nor to the Company’s Knowledge is there
any basis for, the delisting of the Common Stock from Nasdaq.

4.21 Brokers and Finders. No Person will have, as a result of the transactions
contemplated by the Transaction Documents, any valid right, interest or claim
against or upon the Company or an Investor for any commission, fee or other
compensation pursuant to any agreement, arrangement or understanding entered
into by or on behalf of the Company.

4.22 No Directed Selling Efforts or General Solicitation. Neither the Company
nor any Person acting on its behalf has conducted any general solicitation or
general advertising (as those terms are used in Regulation D) in connection with
the offer or sale of any of the Securities.

4.23 No Integrated Offering. Neither the Company nor any of its Affiliates, nor
any Person acting on its or their behalf has, directly or indirectly, made any
offers or sales of any Company security or solicited any offers to buy any
security, under circumstances that would adversely affect reliance by the
Company on Section 4(2) for the exemption from registration for the transactions
contemplated hereby or would require registration of the Securities under the
1933 Act.

4.24 Private Placement. The offer and sale of the Securities to the Investors as
contemplated hereby is exempt from the registration requirements of the 1933
Act.

4.25 Questionable Payments. Neither the Company nor, to the Company’s Knowledge,
any of its respective current or former stockholders, directors, officers,
employees, agents or other Persons acting on behalf of the Company, has on
behalf of the Company or in connection with its business: (a) used any corporate
funds for unlawful contributions, gifts, entertainment or other unlawful
expenses relating to political activity; (b) made any direct or indirect
unlawful payments to any governmental officials or employees from corporate
funds; (c) established or maintained any unlawful or unrecorded fund of
corporate monies or other assets; (d) made any false or fictitious entries on
the books and records of the Company; or (e) made any unlawful bribe, rebate,
payoff, influence payment, kickback or other unlawful payment of any nature.

4.26 Transactions with Affiliates. Except as disclosed in the SEC Filings or as
disclosed on Schedule 4.26, none of the officers or directors of the Company
and, to the Company’s Knowledge, none of the employees of the Company is
presently a party to any transaction with the Company (other than as holders of
stock options and/or warrants, and for services as employees, officers and
directors), including any contract, agreement or other arrangement providing for
the furnishing of services to or by, providing for rental of real or personal
property to or from, or otherwise requiring payments to or from any officer,
director or such employee or, to the Company’s Knowledge, any entity in which
any officer, director, or any such employee has a substantial interest or is an
officer, director, trustee or partner.

4.27 Internal Controls. The Company is in material compliance with the
provisions of the Sarbanes-Oxley Act of 2002 currently applicable to the
Company. The Company maintains a system of internal accounting controls
sufficient to provide reasonable assurance that (i) transactions are executed in
accordance with management’s general or specific authorizations,
(ii) transactions are recorded as necessary to permit preparation of financial
statements in conformity with GAAP and to maintain asset accountability,
(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 the existing assets at reasonable intervals and appropriate action
is taken with respect to any differences. The Company has established disclosure
controls and procedures (as defined in 1934 Act Rules 13a-14 and 15d-14) for the
Company and designed such disclosure controls and procedures to ensure that
material information relating to the Company is made known to the certifying
officers by others within the Company, particularly during the period in which
the Company’s most recently filed period report under the 1934 Act, as the case
may be, is being prepared. The Company’s certifying officers have evaluated the
effectiveness of the Company’s controls and procedures as of the end of the
period covered by the most recently filed periodic report under the 1934 Act
(such date, the “Evaluation Date”). The Company presented in its most recently
filed periodic report under the 1934 Act the conclusions of the certifying
officers about the effectiveness of the disclosure controls and procedures based
on their evaluations as of the Evaluation Date. Since the Evaluation Date, there
have been no significant changes in the Company’s internal controls (as such
term is defined in Item 308 of Regulation S-K) or, to the Company’s Knowledge,
in other factors that could significantly affect the Company’s internal
controls. The Company maintains and will continue to maintain a standard system
of accounting established and administered in accordance with GAAP and the
applicable requirements of the 1934 Act.

4.28 Disclosures.

(a) Neither the Company nor any Person acting on its behalf has provided the
Investors or their agents or counsel with any information that constitutes
material, non-public information, other than the existence of this Agreement and
the other Transaction Documents and the transactions contemplated hereby and
thereby.

(b) No representation or warranty of the Company contained in this Section 4, as
qualified by the Disclosure Schedules, contains any untrue statement of a
material fact or omits to state a material fact necessary in order to make the
statements contained herein not misleading in light of the circumstances under
which they were made.

4.29 Most Favored Nations. None of the Investors shall be entitled to any
rights, preferences or privileges under the Transaction Documents that are more
favorable to such Investor than the rights, preferences and privileges
applicable to any other Investor under the Transaction Documents, except as set
forth in Section 7.11 hereunder (such more favorable terms, the “More Favorable
Terms”).

5. Representations and Warranties of the Investors. Each of the Investors hereby
severally, and not jointly, represents and warrants to the Company that:

5.1 Organization and Existence. Such Investor is a validly existing corporation,
limited partnership or limited liability company and has all requisite
corporate, partnership or limited liability company power and authority to
invest in the Securities pursuant to this Agreement.

5.2 Authorization. The execution, delivery and performance by such Investor of
the Transaction Documents to which such Investor is a party have been duly
authorized, and this Agreement constitutes, and the other Transaction Documents
will constitute when executed and delivered, the valid and legally binding
obligations of such Investor, enforceable against such Investor in accordance
with their respective terms, subject to bankruptcy, insolvency, fraudulent
transfer, reorganization, moratorium and similar laws of general applicability,
relating to or affecting creditors’ rights generally.

5.3 Purchase Entirely for Own Account. The Securities to be received by such
Investor hereunder will be acquired for such Investor’s own account, not as
nominee or agent, and not with a view to the resale or distribution of any part
thereof in violation of the 1933 Act, and such Investor has no present intention
of selling, granting any participation in, or otherwise distributing the same in
violation of the 1933 Act without prejudice, however, to such Investor’s right
at all times to sell or otherwise dispose of all or any part of such Securities
in compliance with applicable federal and state securities laws. Nothing
contained herein shall be deemed a representation or warranty by such Investor
to hold the Securities for any period of time. Such Investor is not a
broker-dealer registered with the SEC under the 1934 Act or an entity engaged in
a business that would require it to be so registered.

5.4 Investment Experience. Such Investor acknowledges that it can bear the
economic risk and complete loss of its investment in the Securities and has such
knowledge and experience in financial or business matters that it is capable of
evaluating the merits and risks of the investment contemplated hereby.

5.5 Disclosure of Information. Such Investor has had an opportunity to receive
all information related to the Company requested by it and to ask questions of
and receive answers from the Company regarding the Company, its business and the
terms and conditions of the offering of the Securities. Such Investor
acknowledges receipt of copies of the SEC Filings. Neither such inquiries nor
any other due diligence investigation conducted by such Investor shall modify,
amend or affect such Investor’s right to rely on the Company’s representations
and warranties contained in this Agreement.

5.6 Restricted Securities. Such Investor understands that the Securities are
characterized as “restricted securities” under the U.S. federal securities laws
inasmuch as they are being acquired from the Company in a transaction not
involving a public offering and that under such laws and applicable regulations
such securities may be resold without registration under the 1933 Act only in
certain limited circumstances.

5.7 Legends. It is understood that, except as provided below, certificates
evidencing the Securities may bear the following or any similar legend:

(a) “The securities represented hereby may not be transferred unless (i) such
securities have been registered for sale pursuant to the Securities Act of 1933,
as amended, (ii) such securities may be sold pursuant to Rule 144(k), or
(iii) the Company has received an opinion of counsel reasonably satisfactory to
it that such transfer may lawfully be made without registration under the
Securities Act of 1933 or qualification under applicable state securities laws.”

(b) If required by the authorities of any state in connection with the issuance
of sale of the Securities, the legend required by such state authority.

5.8 Accredited Investor. Such Investor is an accredited investor as defined in
Rule 501(a) of Regulation D, as amended, under the 1933 Act.

5.9 No General Solicitation. Such Investor did not learn of the investment in
the Securities as a result of any public advertising or general solicitation.

5.10 Brokers and Finders. No Person will have, as a result of the transactions
contemplated by the Transaction Documents, any valid right, interest or claim
against or upon the Company or an Investor for any commission, fee or other
compensation pursuant to any agreement, arrangement or understanding entered
into by or on behalf of such Investor.

5.11 Prohibited Transactions. During the last thirty (30) days prior to the date
hereof, neither such Investor nor any Affiliate of such Investor which (x) had
knowledge of the transactions contemplated hereby, (y) has or shares discretion
relating to such Investor’s investments or trading or information concerning
such Investor’s investments, including in respect of the Securities, or (z) is
subject to such Investor’s review or input concerning such Affiliate’s
investments or trading (collectively, “Trading Affiliates”) has, directly or
indirectly, effected or agreed to effect any short sale, whether or not against
the box, established any “put equivalent position” (as defined in Rule 16a-1(h)
under the 1934 Act) with respect to the Common Stock, borrowed or pre-borrowed
any shares of Common Stock, granted any other right (including, without
limitation, any put or call option) with respect to the Common Stock or with
respect to any security that includes, relates to or derived any significant
part of its value from the Common Stock or otherwise sought to hedge its
position in the Securities (each, a “Prohibited Transaction”). Prior to the
earliest to occur of (i) the termination of this Agreement, (ii) the Effective
Date or (iii) the Effectiveness Deadline, such Investor shall not, and shall
cause its Trading Affiliates not to, (A) engage, directly or indirectly, in a
Prohibited Transaction, or (B) effect any sale, assignment, pledge,
hypothecation, put, call, transfer or other disposition of any Securities.

5.12 Ownership. Such Investor, together with its Affiliates and any other party
acting in concert therewith, will not, following its investment in the
Securities, beneficially own more than 19.9% of the outstanding shares of Common
Stock of the Company.

5.13 Independence. Each Investor acknowledges and agrees that it has acted
independently from all other Investors (other than those under common ownership
and control) and that each such Investor has conducted its own due diligence and
reviewed (or had the opportunity to review) the Transaction Documents with its
own independent counsel.  Each Investor has independently determined the merits
and risks associated with an investment on the basis set forth in the
Transaction Documents and without any agreements, understandings or arrangements
other than those expressly set forth in the Transaction Documents.          .

6. Conditions to Closing.

6.1 Conditions to the Investors’ Obligations. The obligation of each Investor to
purchase the Shares at the Closing is subject to the fulfillment to such
Investor’s satisfaction, on or prior to the Closing Date, of the following
conditions, any of which may be waived by such Investor (as to itself only):

(a) The representations and warranties made by the Company in Section 4 hereof
qualified as to materiality shall be true and correct at all times prior to and
on the Closing Date, except to the extent any such representation or warranty
expressly speaks as of an earlier date, in which case such representation or
warranty shall be true and correct as of such earlier date, and, the
representations and warranties made by the Company in Section 4 hereof not
qualified as to materiality shall be true and correct in all material respects
at all times prior to and on the Closing Date, except to the extent any such
representation or warranty expressly speaks as of an earlier date, in which case
such representation or warranty shall be true and correct in all material
respects as of such earlier date. The Company shall have performed in all
material respects all obligations and covenants herein required to be performed
by it on or prior to the Closing Date.

(b) The Company shall have obtained any and all consents, permits, approvals,
registrations and waivers (including, without limitation, approval in accordance
with applicable law and the applicable requirements of any stock exchange or
market on which the Common Stock is traded or quoted) necessary for consummation
of the purchase and sale of the Securities and the consummation of the other
transactions contemplated by the Transaction Documents, all of which shall be in
full force and effect; provided, however, that it shall not be a condition to
each Investor’s obligation to purchase the Shares at the Closing that the
Company obtain the waiver of any “piggyback” registration rights held by the
Company’s securityholders under written agreements entered into by the Company
prior to the date hereof.

(c) The Company shall have executed and delivered the Registration Rights
Agreement.

(d) The Company shall have taken all action necessary to effect the listing of
the Shares on the Nasdaq National Market upon official notice of issuance.

(e) The Board shall have adopted a revised budget for calendar year 2006 (the
“Approved Budget”), which Approved Budget shall provide that the net proceeds
from the sale of the Shares hereunder will be used to fund novel internal
discovery efforts and that any amendment or variance with respect to such aspect
of the Approved Budget shall require the prior approval of the Board of
Directors.

(f) [Intentionally Omitted]

(g) No judgment, writ, order, injunction, award or decree of or by any court, or
judge, justice or magistrate, including any bankruptcy court or judge, or any
order of or by any governmental authority, shall have been issued, and no action
or proceeding shall have been instituted by any governmental authority,
enjoining or preventing the consummation of the transactions contemplated hereby
or in the other Transaction Documents.

(h) The Company shall have delivered a Certificate, executed on behalf of the
Company by its Chief Executive Officer, dated as of the Closing Date, certifying
to the fulfillment of the conditions specified in subsections (a), (b), (d),
(e), (g) (which subsection (g) shall be qualified to the Company’s Knowledge)
and (k) of this Section 6.1.

(i) The Company shall have delivered a Certificate, executed on behalf of the
Company by its Secretary, dated as of the Closing Date, certifying the
resolutions adopted by the Board approving the transactions contemplated by this
Agreement and the other Transaction Documents and the issuance of the
Securities, certifying the current versions of the Certificate of Incorporation
and Bylaws of the Company and certifying as to the signatures and authority of
persons signing the Transaction Documents and related documents on behalf of the
Company.

(j) The Investors shall have received an opinion from Hogan & Hartson L.L.P.,
the Company’s outside counsel, dated as of the Closing Date, in form and
substance reasonably acceptable to the Investors and addressing such legal
matters as set forth on Exhibit B attached hereto.

(k) No stop order or suspension of trading shall have been imposed by Nasdaq,
the SEC or any other governmental or regulatory body with respect to public
trading in the Common Stock.

6.2 Conditions to Obligations of the Company. The Company’s obligation to sell
and issue the Shares at the Closing is subject to the fulfillment to the
satisfaction of the Company on or prior to the Closing Date of the following
conditions, any of which may be waived by the Company:

(a) The representations and warranties made by the Investors in Section 5
hereof, other than the representations and warranties contained in Sections 5.3,
5.4, 5.5, 5.6, 5.7, 5.8, 5.9 and 5.12 (the “Investment Representations”), shall
be true and correct in all material respects when made, and shall be true and
correct in all material respects as of the Closing Date with the same force and
effect as if they had been made on and as of said date. The Investment
Representations shall be true and correct in all respects when made, and shall
be true and correct in all respects on the Closing Date with the same force and
effect as if they had been made on and as of said date. The Investors shall have
performed in all material respects all obligations and covenants herein required
to be performed by them on or prior to the Closing Date.

(b) The Investors shall have executed and delivered the Registration Rights
Agreement.

(c) The Investors shall have delivered the Purchase Price to the Company in the
manner contemplated by Section 3.

(d) The Company shall have obtained any and all consents, permits, approvals,
registrations and waivers (including, without limitation, approval in accordance
with applicable law and the applicable requirements of any stock exchange or
market on which the Common Stock is traded or quoted) necessary or appropriate
for consummation of the purchase and sale of the Securities and the consummation
of the other transactions contemplated by the Transaction Documents, all of
which shall be in full force and effect; provided, however, that it shall not be
a condition to the Company’s obligation to sell and issue the Shares that the
Company obtain the waiver of any “piggyback” registration rights held by the
Company’s securityholders under written agreements entered into by the Company
prior to the date hereof.

(e) No judgment, writ, order, injunction, award or decree of or by any court, or
judge, justice or magistrate, including any bankruptcy court or judge, or any
order of or by any governmental authority, shall have been issued, and no action
or proceeding shall have been instituted by any governmental authority,
enjoining or preventing the consummation of the transactions contemplated hereby
or in the other Transaction Documents.

(f) The Company shall have received gross proceeds from the sale of the Shares
as contemplated hereby of $7,249,997.10.

6.3 Termination of Obligations to Effect Closing; Effects.

(a) The obligations of the Company, on the one hand, and the Investors, on the
other hand, to effect the Closing may be terminated as follows:

(i) Upon the mutual written consent of the Company and the Investors;

(ii) By the Company if any of the conditions set forth in Section 6.2 shall have
become incapable of fulfillment, and shall not have been waived by the Company;

(iii) By an Investor (with respect to itself only) if any of the conditions set
forth in Section 6.1 shall have become incapable of fulfillment, and shall not
have been waived by the Investor; or

(iv) By either the Company or any Investor (with respect to itself only) if the
Closing has not occurred on or prior to March 31, 2006;

provided, however, that, except in the case of clause (i) above, the party
seeking to terminate its obligation to effect the Closing shall not then be in
breach of any of its representations, warranties, covenants or agreements
contained in this Agreement or the other Transaction Documents if such breach
has resulted in the circumstances giving rise to such party’s seeking to
terminate its obligation to effect the Closing.

(b) In the event of termination by any Investor of its obligations to effect the
Closing pursuant to this Section 6.3 (such Investor, a “Terminating Investor”),
written notice thereof shall forthwith be given to the other Investors, and each
other Investor shall have the right (but not the obligation) to purchase at a
price per Share equal to the Per Share Purchase Price a pro rata portion of the
Terminating Investor’s allocated portion of the total number of Shares to be
acquired by all Investors under this Agreement (or such greater portion of the
Terminated Investor’s allocated portion of the Shares as otherwise agreed to
among each of the other Investors electing to purchase a portion of the
Terminated Investor’s allocated portion of the Shares). Nothing in this
Section 6.3 shall be deemed to release any party from any liability for any
breach by such party of the terms and provisions of this Agreement or the other
Transaction Documents or to impair the right of any party to compel specific
performance by any other party of its obligations under this Agreement or the
other Transaction Documents.

7. Covenants and Agreements of the Company and the Investors.

7.1 Authorized Common Stock. The Company has a sufficient number of authorized
and unissued shares of Common Stock (after taking into account shares reserved
for issuance under stock plans and for other purposes) to permit the issuance of
the Shares hereunder.

7.2 No Conflicting Agreements. The Company will not take any action, enter into
any agreement or make any commitment that would conflict or interfere in any
material respect with the Company’s obligations to the Investors under the
Transaction Documents.

7.3 Compliance with Laws. The Company will comply in all material respects with
all applicable laws, rules, regulations, orders and decrees of all governmental
authorities.

7.4 Listing of Underlying Shares and Related Matters. The Company has taken all
necessary action to cause the Shares to be listed on the Nasdaq National Market
no later than the Closing Date. Further, if the Company applies to have its
Common Stock or other securities traded on any other principal stock exchange or
market, it shall include in such application the Shares and will take such other
action as is necessary to cause such Common Stock to be so listed. The Company
will use commercially reasonable efforts to continue the listing and trading of
its Common Stock on Nasdaq and, in accordance, therewith, will use commercially
reasonable efforts to comply in all respects with the Company’s reporting,
filing and other obligations under the bylaws or rules of such market or
exchange, as applicable.

7.5 Termination of Covenants. The provisions of Sections 7.2 through 7.4 shall
terminate and be of no further force and effect on the date on which the
Company’s obligations under the Registration Rights Agreement to register or
maintain the effectiveness of any registration covering the Registrable
Securities (as such term is defined in the Registration Rights Agreement) shall
terminate.

7.6 Removal of Legends. Upon the earlier of (i) the sale of any Shares under a
registration statement, (ii) Rule 144(k) becoming available with respect to the
Shares, (iii) any sale pursuant to Rule 144 (assuming the transferor is not an
Affiliate of the Company) or (iv) such time as a legend is no longer required
under applicable requirements of the 1933 Act (including controlling judicial
interpretations and pronouncements issued by the SEC), the Company shall (A)
deliver to the transfer agent for the Common Stock (the “Transfer Agent”)
irrevocable instructions that the Transfer Agent shall reissue a certificate
representing shares of Common Stock without legends upon receipt by such
Transfer Agent of the legended certificates for such shares, together with
either (1) a customary representation by the Investor that all conditions
permitting the removal of the legends have been met, including that Rule 144(k)
applies to the shares of Common Stock represented thereby or that the shares
have been sold pursuant to Rule 144 or (2) in connection with any sale of Common
Stock by any Investor pursuant to the registration contemplated by the
Registration Rights Agreement, a statement by such Investor that it has sold the
shares of Common Stock represented thereby in accordance with the Plan of
Distribution contained in the Registration Statement, and (B) cause its counsel
to deliver to the Transfer Agent one or more blanket opinions to the effect that
the removal of such legends in such circumstances may be effected under the 1933
Act. From and after the earlier of such dates, upon an Investor’s written
request, the Company shall promptly cause certificates evidencing the Investor’s
Securities to be replaced with certificates which do not bear such restrictive
legends. When the Company is required to cause unlegended certificates to
replace previously issued legended certificates, if unlegended certificates are
not delivered to an Investor within five (5) Business Days of submission by that
Investor of legended certificate(s) to the Transfer Agent as provided above, the
Company shall be liable to the Investor for liquidated damages in an amount
equal to 1.5% of the aggregate purchase price of the Securities evidenced by
such certificate(s) for each thirty day period (pro rated for any portion of
such thirty day period) beyond such five (5) Business Days that the unlegended
certificates have not been so delivered.

7.7 Most Favored Nations. Subject to Section 7.10, each Investor shall receive
“most favorite nations status” with respect to the Transaction Documents,
meaning that if the Company takes any action contemplated by Section 4.29, the
terms of the Transaction Documents to which such Investor is a party
automatically shall be amended, without further action, so as to provide such
Investor the benefits of such More Favorable Terms.

7.8 Participation Right.

(a) From and after the Closing until the second anniversary of the Closing Date,
subject to the terms and conditions set forth below, in the event the Company
engages in a Qualified Financing, the Company shall offer to each Investor that
continues to then hold at least twenty-five percent of the Shares acquired by
such Investor hereunder (a “Qualified Investor”) the opportunity to purchase a
Pro Rata Portion of the New Securities offered pursuant thereto at the price per
share (or other per unit price) and on the other terms and conditions as offered
to the other investors in such Qualified Financing.

(b) In the event of a Qualified Financing, the Company shall provide each
Qualified Investor with at least three Business Days during which such Qualified
Investor may elect to purchase all or any portion of such Qualified Investor’s
Pro Rata Portion of the New Securities to be offered in the Qualified Financing
at the price and upon the other terms and conditions applicable to the other
investors in the Qualified Financing by delivering written notice of such
election to the Company within such election period; provided that if the
Company is issuing Common Stock together as a unit with any debt securities or
other equity securities, then any Qualified Investor who elects to purchase New
Securities pursuant to this Section 7.8 must purchase the same proportionate mix
of all of such securities.

(c) Each Qualified Investor’s “Pro Rata Portion” of New Securities shall be
determined as follows: the total number of New Securities, multiplied by a
fraction, (i) the numerator of which is the number of shares of Common Stock
then held by such Qualified Investor, and (ii) the denominator of which is the
number of shares of Common Stock of the Company then issued and outstanding on a
fully-diluted basis.

(d) As used herein, the term “Qualified Financing” means the offer and sale by
the Company of New Securities in a capital raising transaction for cash in a
transaction exempt from the registration requirements of Section 5 of the 1933
Act, other in connection with the following transactions:

(i) as financing for any business combination between the Company and any other
corporation or entity (or other acquisition of a company or a product or
business by the Company); or

(ii) as part of any consulting, licensing, partnering, equipment leasing, bank
financing or other strategic transaction.

(e) As used herein, the term “New Securities” means Common Stock and any
securities exercisable or exchangeable for or convertible into, directly or
indirectly, Common Stock; provided, however, that “New Securities” shall not
include:

(i) securities issued to employees, officers, directors and other service
providers of or to the Company, any of its Subsidiaries or other controlled
entities in accordance with the terms of any applicable incentive plan of the
Company, Subsidiary or other entity approved by the Board (or other supervising
body, as applicable);

(ii) securities issued in connection with the subdivision of Common Stock
(including any split), any combination of Common Stock (including any reverse
split) or any recapitalization, reorganization, reclassification or conversion
of the capital stock of the Company, any Subsidiary or other entity.

(f) Notwithstanding the foregoing, the Company shall have no obligation to offer
any Qualified Investor the opportunity to participate in any Qualified Financing
to the extent that:

(i) such Qualified Investor is not an “accredited investor” as such term is
defined under the 1933 Act at the time of such proposed Qualified Financing or
is not otherwise qualified to participate in the Qualified Financing under the
1933 Act or the applicable rules of the SEC; provided, that the Company shall
take reasonable steps to structure any Qualified Financing so as to permit
participation by a Qualified Investor so long as doing so would not prejudice
the Company’s ability to timely complete the Qualified Financing on terms deemed
to be in the Company’s best interests by the Board (for example, and not by
limitation, if the Qualified Financing is a Rule 144A offering under the 1933
Act and the Qualified Investor is not a “qualified institutional buyer” as
defined under Rule 144A, the Company would have no obligation to take steps to
structure the financing to permit participation by the Qualified Investor); or

(ii) the issuance of New Securities to such Qualified Investor would require the
Company to obtain the approval of the Company’s Stockholders under the rules of
the Nasdaq or any other stock exchange on which the Common Stock is then listed
for trading.

7.9 Use of Proceeds. The net proceeds from the sale of the Shares hereunder
shall be used to fund novel internal discovery efforts of the Company in
accordance with the Approved Budget and any amendment or variance with respect
to such aspect of the Approved Budget shall require the prior approval of the
Board of Directors. For the avoidance of doubt, the Investors agree that the
Approved Budget shall not restrict the Company’s use of its other assets,
including any cash on hand as of the Closing.

7.10 Right to Purchase. The Biotechnology Value Fund, L.P. and its affiliates
(“BVP”) shall have the right to purchase at least fifty (50%) percent of the
Shares offered to be issued by the Company hereunder or 9.99% of the Company’s
total outstanding shares of Common Stock (calculated on a post closing basis),
whichever is greater, provided that in no event shall BVP and any Persons acting
in concert with BVP own more than 19.9% of the outstanding shares of Common
Stock of the Company following BVP’s investment in the Securities.

8. Survival and Indemnification.

8.1 Survival. The representations, warranties, covenants and agreements
contained in this Agreement shall survive the Closing of the transactions
contemplated by this Agreement; provided, however, that any claim for Losses as
a result of a breach of a representation or warranty contained herein must be
must be made, if at all, within twenty-four (24) months of the Closing.

8.2 Indemnification. The Company agrees to indemnify and hold harmless each
Investor and its Affiliates and their respective directors, officers, employees,
attorneys and agents from and against, without duplication, (a) any and all
losses, claims, damages, liabilities and expenses (including without limitation
reasonable attorneys fees and disbursements and other expenses incurred in
connection with investigating, preparing or defending any action, claim or
proceeding, pending or threatened and the costs of enforcement thereof)
(collectively, “Losses”) to which such Person may become subject as a result of
any breach of representation, warranty, covenant or agreement made by or to be
performed on the part of the Company under the Transaction Documents.

8.3 Conduct of Indemnification Proceedings. Promptly after receipt by any Person
(the “Indemnified Person”) of notice of any demand, claim or circumstances which
would or might give rise to a claim or the commencement of any action,
proceeding or investigation in respect of which indemnity may be sought pursuant
to Section 8.2, such Indemnified Person shall promptly notify the Company in
writing and the Company shall assume the defense thereof, including the
employment of counsel reasonably satisfactory to such Indemnified Person, and
shall assume the payment of all fees and expenses; provided, however, that the
failure of any Indemnified Person so to notify the Company shall not relieve the
Company of its obligations hereunder except to the extent that the Company is
materially prejudiced by such failure to notify. In any such proceeding, any
Indemnified Person shall have the right to retain its own counsel, but the fees
and expenses of such counsel shall be at the expense of such Indemnified Person
unless: (i) the Company and the Indemnified Person shall have mutually agreed to
the retention of such counsel; or (ii) in the reasonable judgment of counsel to
such Indemnified Person representation of both parties by the same counsel would
be inappropriate due to actual or potential differing interests between them.
The Company 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 Company shall indemnify and hold harmless such Indemnified Person
from and against any loss or liability (to the extent stated above) by reason of
such settlement or judgment. Without the prior written consent of the
Indemnified Person, which consent shall not be unreasonably withheld, the
Company shall not effect any settlement of any pending or threatened proceeding
in respect of which any Indemnified Person is or could have been a party and
indemnity could have been sought hereunder by such Indemnified Party, unless
such settlement includes an unconditional release of such Indemnified Person
from all liability arising out of such proceeding.

9. Miscellaneous.

9.1 Successors and Assigns. This Agreement may not be assigned by a party hereto
without the prior written consent of the Company or the Investors, as
applicable, provided, however, that an Investor may assign its rights and
delegate its duties hereunder in whole or in part to an Affiliate or to a third
party acquiring some or all of its Securities in a private transaction without
the prior written consent of the Company or the other Investors, after notice
duly given by such Investor to the Company provided, that no such assignment or
obligation shall affect the obligations of such Investor hereunder. The
provisions of this Agreement shall inure to the benefit of and be binding upon
the respective permitted successors and assigns of the parties. Nothing in this
Agreement, express or implied, is intended to confer upon any party other than
the parties hereto or their respective successors and assigns any rights,
remedies, obligations, or liabilities under or by reason of this Agreement,
except as expressly provided in this Agreement (including in Section 9.6).

9.2 Counterparts; Faxes. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument. This Agreement may also
be executed via facsimile, which shall be deemed an original.

9.3 Titles and Subtitles. The titles and subtitles used in this Agreement are
used for convenience only and are not to be considered in construing or
interpreting this Agreement.

9.4 Notices. Unless otherwise provided, any notice required or permitted under
this Agreement shall be given in writing and shall be deemed effectively given
as hereinafter described (i) if given by personal delivery, then such notice
shall be deemed given upon such delivery, (ii) if given by telex or telecopier,
then such notice shall be deemed given upon receipt of confirmation of complete
transmittal, (iii) if given by mail, then such notice shall be deemed given upon
the earlier of (A) receipt of such notice by the recipient or (B) three days
after such notice is deposited in first class mail, postage prepaid, and (iv) if
given by an internationally recognized overnight air courier, then such notice
shall be deemed given one Business Day after delivery to such carrier. All
notices shall be addressed to the party to be notified at the address as
follows, or at such other address as such party may designate by ten days’
advance written notice to the other party:

If to the Company:

Avalon Pharmaceuticals, Inc.
20358 Seneca Meadows Parkway
Germantown, Maryland 20876
Attention: Kenneth C. Carter, Ph.D. President and CEO
Telephone: (301) 556-9900

With a copy to:

Hogan & Hartson L.L.P.
111 South Calvert Street, Suite 1600
Baltimore, Maryland 21202
Telephone: (410) 659-2790

If to any Investor:

to such Investor’s address(es) set forth on the signature pages hereto.

9.5 Expenses. The parties hereto shall pay their own costs and expenses in
connection herewith, except that the Company shall pay the reasonable and
documented fees and expenses of Jonathan D. Joseph, Esquire in connection with
the negotiation and execution of the Transaction Documents in an amount not to
exceed $15,000. Such expenses shall be paid not later than the Closing. The
Company shall reimburse the Investors upon demand for all reasonable and
documented out-of-pocket expenses incurred by the Investors, including without
limitation reimbursement of attorneys’ fees and disbursements, in connection
with any amendment, modification or waiver of this Agreement or the other
Transaction Documents. In the event that legal proceedings are commenced by any
party to this Agreement against another party to this Agreement in connection
with this Agreement or the other Transaction Documents, the party or parties
which do not prevail in such proceedings shall severally, but not jointly, pay
their pro rata share of the reasonable attorneys’ fees and other reasonable and
documented out-of-pocket costs and expenses incurred by the prevailing party in
such proceedings.

9.6 Amendments and Waivers. Any term of this Agreement may be amended and the
observance of any term of this Agreement may be waived (either generally or in a
particular instance and either retroactively or prospectively), only with the
written consent of the Company and the Investors. Any amendment or waiver
effected in accordance with this paragraph shall be binding upon each holder of
any Securities purchased under this Agreement at the time outstanding, each
future holder of all such Securities, and the Company.

9.7 Publicity. Except as set forth below, no public release or announcement
concerning the transactions contemplated hereby shall be issued by the Company
or the Investors without the prior consent of the Company (in the case of a
release or announcement by the Investors) or the Investors (in the case of a
release or announcement by the Company) (which consents shall not be
unreasonably withheld), except as such release or announcement may be required
by law or the applicable rules or regulations of any securities exchange or
securities market, in which case the Company or the Investors, as the case may
be, shall allow the Investors or the Company, as applicable, to the extent
reasonably practicable in the circumstances, reasonable time to comment on such
release or announcement in advance of such issuance. By 8:30 a.m. (New York City
time) on the trading day immediately following the date hereof, the Company
shall issue a press release disclosing the execution and delivery of this
Agreement. No later than the fourth Business Day following the date hereof, the
Company will file a Current Report on Form 8-K attaching the press release
described in the foregoing sentence. By 8:30 a.m. (New York City time) on the
trading day immediately following the Closing Date, the Company shall issue a
press release disclosing the consummation of the transactions contemplated by
this Agreement. No later than the fourth Business Day following the Closing
Date, the Company will file a Current Report on Form 8-K attaching the press
release described in the foregoing sentence. In addition, the Company will make
such other filings and notices in the manner and time required by the SEC or
Nasdaq. Notwithstanding the foregoing, the Company shall not publicly disclose
the name of any Investor, or include the name of any Investor in any filing with
the SEC (other than such Forms 8-K, the Registration Statement and any exhibits
to filings made in respect of this transaction in accordance with periodic
filing requirements under the 1934 Act) or any regulatory agency or Nasdaq,
without the prior written consent of such Investor, except to the extent such
disclosure is required by law or trading market regulations.

9.8 Severability. Any provision of this Agreement that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof but shall be interpreted as if it were written so as
to be enforceable to the maximum extent permitted by applicable law, and any
such prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction. To the extent
permitted by applicable law, the parties hereby waive any provision of law which
renders any provision hereof prohibited or unenforceable in any respect.

9.9 Entire Agreement. This Agreement, including the Exhibits and the Disclosure
Schedules, and the other Transaction Documents constitute the entire agreement
among the parties hereof with respect to the subject matter hereof and thereof
and supersede all prior agreements and understandings, both oral and written,
between the parties with respect to the subject matter hereof and thereof
(including that certain Term Sheet, dated as of February 3, 2006, by and between
the Company and Biotechnology Value Fund, L.P.).

9.10 Further Assurances. The parties shall execute and deliver all such further
instruments and documents and take all such other actions as may reasonably be
required to carry out the transactions contemplated hereby and to evidence the
fulfillment of the agreements herein contained.

9.11 Governing Law; Consent to Jurisdiction; Waiver of Jury Trial. This
Agreement shall be governed by, and construed in accordance with, the internal
laws of the State of New York without regard to the choice of law principles
thereof. Each of the parties hereto irrevocably submits to the exclusive
jurisdiction of the courts of the State of New York located in New York County
and the United States District Court for the Southern District of New York for
the purpose of any suit, action, proceeding or judgment relating to or arising
out of this Agreement and the transactions contemplated hereby. Service of
process in connection with any such suit, action or proceeding may be served on
each party hereto anywhere in the world by the same methods as are specified for
the giving of notices under this Agreement. Each of the parties hereto
irrevocably consents to the jurisdiction of any such court in any such suit,
action or proceeding and to the laying of venue in such court. Each party hereto
irrevocably waives any objection to the laying of venue of any such suit, action
or proceeding brought in such courts and irrevocably waives any claim that any
such suit, action or proceeding brought in any such court has been brought in an
inconvenient forum. EACH OF THE PARTIES HERETO WAIVES ANY RIGHT TO REQUEST A
TRIAL BY JURY IN ANY LITIGATION WITH RESPECT TO THIS AGREEMENT AND REPRESENTS
THAT COUNSEL HAS BEEN CONSULTED SPECIFICALLY AS TO THIS WAIVER.

9.12 Independent Nature of Investors’ Obligations and Rights. The obligations of
each Investor under any Transaction Document are several and not joint with the
obligations of any other Investor, and no Investor shall be responsible in any
way for the performance of the obligations of any other Investor under any
Transaction Document. The decision of each Investor to purchase Securities
pursuant to the Transaction Documents has been made by such Investor
independently of any other Investor. Nothing contained herein or in any
Transaction Document, and no action taken by any Investor pursuant thereto,
shall be deemed to constitute the Investors as a partnership, an association, a
joint venture or any other kind of entity, or create a presumption that the
Investors are in any way acting in concert or as a group with respect to such
obligations or the transactions contemplated by the Transaction Documents. Each
Investor acknowledges that no other Investor has acted as agent for such
Investor in connection with making its investment hereunder and that no Investor
will be acting as agent of such Investor in connection with monitoring its
investment in the Securities or enforcing its rights under the Transaction
Documents. Each Investor shall be entitled to independently protect and enforce
its rights, including, without limitation, the rights arising out of this
Agreement or out of the other Transaction Documents, and it shall not be
necessary for any other Investor to be joined as an additional party in any
proceeding for such purpose. The Company acknowledges that each of the Investors
has been provided with the same Transaction Documents for the purpose of closing
a transaction with multiple Investors and not because it was required or
requested to do so by any Investor.

[Signature pages follow]

1

IN WITNESS WHEREOF, the parties have executed this Agreement or caused their
duly authorized officers to execute this Agreement as of the date first above
written.

The Company:

AVALON PHARMACEUTICALS, INC.

By:/s/ Kenneth C. Carter, Ph.D.
Name: Kenneth C. Carter, Ph.D.
Title: President and Chief Executive Officer

2

The Investors:

BIOTECHNOLOGY VALUE FUND, L.P.

By: BVF Partners, L.P., its general partner
By: BVF Inc., its general partner

By:/s/ Mark N. Lampert
Name: Mark N. Lampert
Title: President

Aggregate Purchase Price: $818,996.25
Number of Shares: 188,275

Address for Notice:

One Sansome Street
39th Floor
San Francisco, CA 94104

with a copy to:

Jonathan D. Joseph, Esq.
P.O. Box 720037
San Francisco, CA 94172-0037

Facsimile: 415.643.5253

3

BIOTECHNOLOGY VALUE FUND II, L.P.

By: BVF Partners, L.P., its general partner
By: BVF Inc., its general partner

By:/s/ Mark N. Lampert
Name: Mark N. Lampert
Title: President

Aggregate Purchase Price: $563,381.55
Number of Shares: 129,513

Address for Notice:

One Sansome Street
39th Floor
San Francisco, CA 94104

with a copy to:

Jonathan D. Joseph, Esq.
P.O. Box 720037
San Francisco, CA 94172-0037
Facsimile: 415.643.5253

4

BVF INVESTMENTS, L.L.C.
By: BVF Partners, L.P., its manager

By: BVF Inc, its general partner

By:/s/ Mark N. Lampert
Name: Mark N. Lampert
Title: President

Aggregate Purchase Price: $238,406.10
Number of Shares: 54,806

Address for Notice:

One Sansome Street
39th Floor
San Francisco, CA 94104

with a copy to:

Jonathan D. Joseph, Esq.
P.O. Box 720037
San Francisco, CA 94172-0037
Facsimile: 415.643.5253

5

INVESTMENT 10, L.L.C.
By: BVF Partners, L.P., its attorney-in-fact

By: BVF Inc., its general partner

By:/s/ Mark N. Lampert
Name: Mark N. Lampert
Title: President

Aggregate Purchase Price: $2,149,213.20
Number of Shares: 494,072

Address for Notice:

One Sansome Street
39th Floor
San Francisco, CA 94104

with a copy to:

Jonathan D. Joseph, Esq.
P.O. Box 720037
San Francisco, CA 94172-0037
Facsimile: 415.643.5253

6

XMARK JV INVESTMENT PARTNERS, LLC

By:/s/ Mitchell D. Kaye
Name: Mitchell D. Kaye
Title: Chief Investment Officer

Aggregate Purchase Price: $1,000,500
Number of Shares: 230,000

Address for Notice:

XMARK FUNDS
301 Tresser Blvd., Suite 1320
Stamford, CT 06901

with a copy to:

     
     
     
Facsimile: 203-653-2501

7

XMARK OPPORTUNITY FUND, L.P.

By:/s/ Mitchell D. Kaye
Name: Mitchell D. Kaye
Title: Chief Investment Officer

Aggregate Purchase Price: $500,250
Number of Shares: 115,000

Address for Notice:

XMARK FUNDS
301 Tresser Blvd., Suite 1320
Stamford, CT 06901

with a copy to:

     
     
     
Facsimile: 203-653-2501

8

XMARK OPPORTUNITY FUND, LTD.

By:/s/ Mitchell D. Kaye
Name: Mitchell D. Kaye
Title: Chief Investment Officer

Aggregate Purchase Price: $500,250
Number of Shares: 115,000

Address for Notice:

XMARK FUNDS
301 Tresser Blvd., Suite 1320
Stamford, CT 06901

with a copy to:

     
     
     
Facsimile: 203-653-2501

9

FORT MASON MASTER, LP

By:/s/ Dan German
Name: Dan German
Title: Managing Member

Aggregate Purchase Price: $1,388,928.90
Number of Shares: 319,294

Address for Notice:

456 Montgomery Street
22nd Floor
San Francisco, CA 94104

with a copy to:

N/A
Facsimile:      

10

FORT MASON PARTNERS, LP

By:/s/ Dan German
Name: Dan German
Title: Managing Member

Aggregate Purchase Price: $90,071.10
Number of Shares: 20,706

Address for Notice:

456 Montgomery Street
22nd Floor
San Francisco, CA 94104

with a copy to:

N/A
Facsimile:      

11

SCHEDULE 4.3

CAPITALIZATION

                      Authorized Stock   # Shares    Common stock
    60,000,000      Preferred Stock
           Series A
    422,500      Series B
    2,873,003      Undesignated
    2,000,000      Total Authorized Preferred *
    5,295,503   Total shares of common stock reserved for issuance pursuant to
the Company’s stock plans
    2,600,000   Outstanding Stock
         
        Total Outstanding Common Stock
    8,417,202    
        Options and Warrants
         
        Total shares of Common Stock issuable upon exercise of currently
outstanding options
    1,547,330    
        Total shares of Common Stock issuable upon exercise of currently
outstanding warrants
    394,141    
       

• Represents the cancellation of shares of preferred stock converted to common
stock in the Company’s initial public offering.

      Registration Rights    
Agreement
  The Company is a party to a Registration
Rights Agreement with certain of its
stockholders dated October 26, 2001 that
provides such stockholders with certain
“demand” and “piggyback” registration rights
as set forth in the Agreement.
 
   
Compugen Warrant
  The terms of the warrant issued by the
Company to Compugen, dated March 23, 2003,
provides the holder with certain “piggyback”
registration rights and with weighted-average
anti-dilution protection in certain
circumstances as set forth in the warrant.
 
   
Alexandria Real Estate
Warrant
 
The terms of the warrant issued by the
company to Alexandria Real Estate, dated
August 11, 2000, provides the holder with
certain “piggyback” registration rights and
with weighted-average anti-dilution
protection in certain circumstances as set
forth in the warrant.
 
   

12

SCHEDULE 4.5

WAIVERS AND CONSENTS

The execution and delivery by the Company of the Agreement and the performance
of the transactions contemplated therein requires the waiver by WR Hambrecht+Co,
LLC (“Hambrecht”) of the lock-up provisions set forth in the Underwriting
Agreement, dated September 28, 2005, between the Company and Hambrecht, Legg
Mason Wood Walker Incorporated and Susquehanna Financial Group, LLLP, as
representatives of the several underwriters named therein, which waiver has been
obtained by the Company.

13

SCHEDULE 4.8

MATERIAL ADVERSE CHANGES

(ix) the loss of services, termination or change of status of any key employee,
or material change in the composition or duties of the senior management of the
Company

      Staszek Pikul,     Director of Medicinal Chemistry   Resigned, effective
January 6, 2006 Paul Young     Vice President of Research   Change of status to
Vice President     of Technology, effective January 30,     2006
Gary Lessing
CFO
Glen Farmer
Controller
 
Promoted to Executive Vice
President, effective December 1,
2005 and continues as CFO

Rescinded resignation submitted
December 16, 2006. Has served
continuously as Controller since
May 9, 2005, when he began
employment at Avalon
 
   
Stephen Horrigan
  Promoted to Acting Vice President of
Research, effective January 30, 2006
 
   

14

SCHEDULE 4.14

LABOR MATTERS

    Subsection (d) Severance agreements

Daniel Soppet, Director of Lead Development has an employment agreement dated
April 21, 2005 that provides for six months severance on the following terms if
termination is without cause:

  •   Immediate vesting of half of any shares granted under the Company’s stock
option plan.

  •   Outplacement services.

  •   Company shall pay health insurance for six months.

    Subsection (e) Immigration Status of Employees

All employees have current I-9 documentation

The following three employees have H1-B visas and are in current status: *

* The asterisk denotes that confidential portions of this exhibit have been
omitted in reliance on Rule 24b-2 of the Securities Exchange Act of 1934. The
confidential portions have been submitted separately to the Securities and
Exchange Commission.

15

SCHEDULE 4.15

INTELLECTUAL PROPERTY

The Company has abandoned the following patents within the last six months,
which related either to compounds no longer actively pursued by the Company or
patents on single genes that were potential drug or antibody screening targets
but were not core assets.

          2005-2006 Patent Application Abandonments Application   Due Date  
Status
PCT-193 GEN 44794
  10/15/05   Abandoned
 
       
PCT-191 GEN 3782
  12/17/05   Abandoned
 
       
PCT-192 Compound Classifiers
  12/17/05   Abandoned except US
 
       
PCT-199 T520(20)
  01/23/06   Abandoned
 
       
PCT-200 LC2
  01/28/06   Abandoned
 
       
PCT-201 LC1-1
  02/03/06   Abandoned
 
       
PCT-198 LC1-3
  02/15/06   Abandoned except US

The Company does not seek formal opinions of counsel as to the validity of, or
freedom to operate under, its intellectual property, but has relied on its own
due diligence, which we believe to be standard practice in the industry.

16

SCHEDULE 4.26

TRANSACTIONS WITH AFFILIATES

The Company has continued its consulting relationships with Dr. Kurman and
Mr. Lorimier. In the period between September 29, 2005 and February 23, 2006,
the Company has paid consulting fees to Dr. Kurman in the amount of $6,450 and
to Mr. Lorimier in the amount of $30,000.

Dr. Kenneth C. Carter was elected to the Board of NeoDiagnostix, Inc. in
January 2006. NeoDiagnostix is a privately held company focusing on the
provision of proprietary cancer diagnostic tests on a fee for service basis.
Dr. Carter owns nine percent of the stock in NeoDiagnostix.

On December 1, 2005, the Company entered into an Equipment Rental Agreement with
NeoDiagnostix in which Avalon rented seven items of laboratory equipment to
NeoDiagnostix for a six month term. Dr. Carter advised the Board of his Board
membership, his stock ownership and the equipment rental agreement and the Board
approved.

17

Exhibit A

Form of Registration Rights Agreement

18

REGISTRATION RIGHTS AGREEMENT

This Registration Rights Agreement (the “Agreement”) is made and entered into as
of this 27th day of February, 2006 by and among Avalon Pharmaceuticals, Inc., a
Delaware corporation (the “Company”), and the “Investors” executing this
Agreement and named in that certain Purchase Agreement by and among the Company
and the Investors dated the date hereof (the “Purchase Agreement”).

The parties hereby agree as follows:

1. Certain Definitions.

As used in this Agreement, the following terms shall have the following
meanings:

“Affiliate” means, with respect to any person, any other person which directly
or indirectly controls, is controlled by, or is under common control with, such
person.

“Business Day” means a day, other than a Saturday or Sunday, on which banks in
New York City and San Francisco, California are open for the general transaction
of business.

“Common Stock” shall mean the Company’s common stock, par value $0.01 per share,
and any securities into which such shares may hereinafter be reclassified.

“Investors” shall mean the Investors identified in the Purchase Agreement and
any Affiliate or permitted transferee of any Investor who is a subsequent holder
of any Registrable Securities.

“Prospectus” shall mean the prospectus included in any Registration Statement,
as amended or supplemented by any prospectus supplement, with respect to the
terms of the offering of any portion of the Registrable Securities covered by
such Registration Statement and by all other amendments and supplements to the
prospectus, including post-effective amendments and all material incorporated by
reference in such prospectus.

“Register,” “registered” and “registration” refer to a registration made by
preparing and filing a Registration Statement or similar document in compliance
with the 1933 Act (as defined below), and the declaration or ordering of
effectiveness of such Registration Statement or document.

“Registrable Securities” shall mean (i) the Shares, and (ii) any other
securities issued or issuable with respect to or in exchange for Registrable
Securities; provided, that, a security shall cease to be a Registrable Security
upon (A) sale pursuant to a Registration Statement or Rule 144 under the 1933
Act, or (B) such security becoming eligible for sale by the Investors pursuant
to Rule 144(k).

“Registration Statement” shall mean any registration statement of the Company
filed under the 1933 Act that covers the resale of any of the Registrable
Securities pursuant to the provisions of this Agreement (including each of the
Registration Statements referred to in Section 2), amendments and supplements to
such Registration Statement(s), including post-effective amendments, all
exhibits and all material filed and incorporated by reference in such
Registration Statement.

“Required Investors” mean the Investors holding a majority of the Registrable
Securities.

“Rule 401”, “Rule 415”, “Rule 416”, “Rule 429” and “Rule 461” mean Rule 401,
Rule 415, Rule 416, Rule 429 and Rule 461, respectively, each as promulgated by
the SEC pursuant to the 1933 Act, as such Rule may be amended from time to time,
or any similar rule or regulation hereafter adopted by the SEC having
substantially the same effect as such Rule.

“SEC” means the U.S. Securities and Exchange Commission.”

“Shares” means the shares of Common Stock issued pursuant to the Purchase
Agreement.

“1933 Act” means the Securities Act of 1933, as amended, and the rules and
regulations promulgated thereunder.

“1934 Act” means the Securities Exchange Act of 1934, as amended, and the rules
and regulations promulgated thereunder.

2. Registration.

(a) Registration Statements.

(i) Promptly following the closing of the purchase and sale of the securities
contemplated by the Purchase Agreement (the “Closing Date”) but no later than
five (5) Business Days after the filing of the Company’s Annual Report on Form
10-K for the year ended December 31, 2005 (the “S-1 Filing Deadline”), the
Company shall prepare and file with the SEC a “shelf” registration statement
covering all Registrable Securities for a secondary or resale offering to be
made on a continuous basis pursuant to Rule 415. Such registration statement
shall be on Form S-1 (the “S-1 Registration Statement”) and shall include the
plan of distribution attached hereto as Exhibit A. Such S-1 Registration
Statement also shall cover, to the extent allowable under the 1933 Act and the
rules promulgated thereunder (including Rule 416), such indeterminate number of
additional shares of Common Stock resulting from stock splits, stock dividends
or similar transactions with respect to the Registrable Securities. Such S-1
Registration Statement shall not include any shares of Common Stock or other
securities for the account of any other holder without the prior written consent
of the Required Investors, except for shares of Common Stock held by the
Company’s stockholders having “piggyback” registration rights expressly set
forth in registration rights agreements entered into by the Company prior to the
date hereof. A copy of the initial filing of the Registration Statement (and
each pre-effective amendment thereto) shall be provided to the Investors and
their counsel prior to filing. If the S-1 Registration Statement covering the
Registrable Securities is not filed with the SEC on or prior to the S-1 Filing
Deadline, the Company will make pro rata payments to each Investor, as
liquidated damages and not as a penalty, in an amount equal to 1.5% of the
aggregate amount invested by such Investor for each 30-day period or pro rata
for any portion thereof following the Filing Deadline for which the S-1
Registration Statement is filed with respect to the Registrable Securities. Such
payments shall constitute the Investors’ exclusive monetary remedy for such
events, but shall not affect the right of the Investors to seek injunctive
relief. Payments to be made pursuant to this Section 2(a)(i) shall be due and
payable immediately upon demand in immediately available cash funds. The parties
agree that the liquidated damages provided for in this Section 2(a)(i) represent
a reasonable estimate on the part of the parties, as of the date of this
Agreement, of the amount of damages that may be incurred by the Investors if the
S-1 Registration Statement is not filed by the S-1 Filing Deadline.

(ii) Filing of, or Conversion to, Registration Statement on Form S-3. Within
fifteen (15) calendar days after the Company shall be eligible to file a
registration statement under the 1933 Act to register on Form S-3 the
Registrable Securities for resale but no later than December 15, 2006 (the “S-3
Filing Deadline”), the Company shall prepare and file with the SEC a “shelf”
registration statement covering all the Registrable Securities for a secondary
or resale offering to be made on a continuous basis pursuant to Rule 415. Such
registration statement (in any of the following cases referred to as the “S-3
Registration Statement”) shall be (A) on Form S-3 (if, and only if, the Company
is permitted under the 1933 Act and the rules promulgated thereunder to file a
registration statement on Form S-3), (B) a pre-effective amendment to the S-1
Registration Statement if the S-1 Registration Statement has not previously been
declared effective by the SEC, or (C) a post-effective amendment to the S-1
Registration Statement on Form S-3 if (and only if) the S-1 Registration
Statement has previously been declared effective by the SEC and the Company is
then permitted under the 1933 Act and the rules promulgated thereunder
(including Rule 401) to file a post-effective amendment to such S-1 Registration
Statement on Form S-3. Such S-3 Registration Statement also shall cover, to the
extent allowable under the 1933 Act and the rules promulgated thereunder
(including Rule 416), such indeterminate number of additional shares of Common
Stock resulting from stock splits, stock dividends or similar transactions with
respect to the Registrable Securities. Such S-3 Registration Statement shall not
include any shares of Common Stock or other securities for the account of any
other holder without the prior written consent of the Required Investors, except
for shares of Common Stock held by the Company’s stockholders having “piggyback”
registration rights expressly set forth in registration rights agreements
entered into by the Company prior to the date hereof. The initial filing of the
S-3 Registration Statement shall be provided to the Investors and their counsel
prior to its filing. If the S-3 Registration Statement is a new registration
statement covering the Registrable Securities filed with the SEC pursuant to
Clause (A) of the second sentence of this Section 2(a)(ii) and the Company is
not permitted pursuant to Rule 429 to use the prospectus included in the S-3
Registration Statement as a combined prospectus for the offering covered by the
S-1 Registration Statement, the Company shall use commercially reasonable
efforts to remove from registration by means of a post-effective amendment to
the S-1 Registration Statement any of the Registrable Securities registered
under the S-1 Registration Statement that remain unsold at the time the S-3
Registration Statement is declared effective by the SEC and cause such
post-effective amendment to be declared effective by the SEC no earlier than
concurrently with the effectiveness of the S-3 Registration Statement. If the
S-3 Registration Statement is not filed with the SEC by the S-3 Filing Deadline
(unless the Company is not then eligible to make a filing on Form S-3), the
Company will make pro rata payments to each Investor, as liquidated damages and
not as a penalty, in an amount equal to 1.5% of the aggregate amount invested by
such Investor for each 30-day period or pro rata for any portion thereof
following the date by which such Registration Statement should have been filed
for which no S-3 Registration Statement is filed with respect to the Registrable
Securities. Such payments shall constitute the Investors’ exclusive monetary
remedy for such events, but shall not affect the right of the Investors to seek
injunctive relief. Payments to be made pursuant to this Section 2(a)(ii) shall
be due and payable immediately upon demand in immediately available cash funds.
The parties agree that the liquidated damages provided for in this
Section 2(a)(ii) represent a reasonable estimate on the part of the parties, as
of the date of this Agreement, of the amount of damages that may be incurred by
the Investors if the S-3 Registration Statement is not filed by the S-3 Filing
Deadline.

(b) Expenses. The Company will pay all expenses associated with each
registration, including filing and printing fees, the Company’s counsel and
accounting fees and expenses, costs associated with clearing the Registrable
Securities for sale under applicable state securities laws, listing fees,
reasonable out-of-pocket fees and expenses of one counsel to the Investors
(which fees and expenses shall not exceed $15,000 in the aggregate) and the
Investors’ reasonable out-of-pocket expenses in connection with the
registration, but excluding discounts, commissions, fees of underwriters,
selling brokers, dealer managers or similar securities industry professionals
with respect to the Registrable Securities being sold.

(c) Effectiveness.

(i) The Company shall use commercially reasonable efforts to have the
Registration Statement(s) declared effective as soon as practicable (including
filing with the SEC a request for acceleration of its effectiveness in
accordance with Rule 461 within five (5) Business Days of the date that the
Company is notified (orally or in writing, whichever is earlier) by the staff of
the SEC that a Registration Statement will not be reviewed, or not be subject to
further review). The Company shall notify the Investors by facsimile or e-mail
as promptly as practicable, and in any event, within twenty-four (24) hours,
after any Registration Statement is declared effective and shall simultaneously
provide the Investors with copies of any related Prospectus to be used in
connection with the sale or other disposition of the securities covered thereby.
If (A) the S-1 Registration Statement or the S-3 Registration Statement is not
declared effective by the SEC prior to five (5) Business Days after the staff of
the SEC shall have informed the Company (orally or in writing, whichever is
earlier) that such Registration Statement will not be reviewed by the staff of
the SEC or not be subject to further review, or (B) after a Registration
Statement has been declared effective by the SEC, sales cannot be made pursuant
to such Registration Statement for any reason (including without limitation by
reason of a stop order, or the Company’s failure to update the Registration
Statement), but excluding the inability of any Investor to sell the Registrable
Securities covered thereby due to market conditions and except as excused
pursuant to Section 2(c)(ii) below, then the Company will make pro rata payments
to each Investor, as liquidated damages and not as a penalty, in an amount equal
to 1.5% of the aggregate amount invested by such Investor for each 30- day
period or pro rata for any portion thereof following the date by which such
Registration Statement should have been effective (the “Blackout Period”). Such
payments shall constitute the Investors’ exclusive monetary remedy for such
events, but shall not affect the right of the Investors to seek injunctive
relief. The amounts payable as liquidated damages pursuant to this paragraph
shall be paid monthly within three (3) Business Days of the last day of each
month following the commencement of the Blackout Period until the termination of
the Blackout Period. Such payments shall be made to each Investor in cash. The
parties agree that the liquidated damages provided for in this Section 2(c)(i)
represent a reasonable estimate on the part of the parties, as of the date of
this Agreement, of the amount of damages that may be incurred by the Investors
if the S-1 Registration Statement is not declared effective as hereinabove
provided or if the S-3 Registration Statement is not declared effective by the
applicable S-3 Filing Deadline. For purposes of the obligations of the Company
under this Agreement, except in the case of any Investors who elect in writing
not to have its Registrable Securities included in the Registration Statement,
no Registration Statement shall be considered “effective” with respect to any
Registrable Securities unless such Registration Statement lists the Investors of
such Registrable Securities as “Selling Stockholders” and includes such other
information as is required to be disclosed with respect to such Investors to
permit them to sell their Registrable Securities pursuant to such Registration
Statement.

(ii) For not more than thirty (30) consecutive days or for a total of not more
than sixty (60) days in any twelve (12) month period, the Company may delay the
disclosure of material non-public information concerning the Company, by
suspending the use of any Prospectus included in any registration contemplated
by this Section or by delaying any post-effective amendment to the Form S-1
Registration Statement (if the Form S-3 Registration Statement has not yet
become effective), if such disclosure at the time is not, in the good faith
opinion of the Company, in the best interests of the Company (an “Allowed
Delay”); provided, that the Company shall promptly (a) notify the Investors in
writing of the existence of (but in no event, without the prior written consent
of an Investor, shall the Company disclose to such Investor any of the facts or
circumstances regarding)an Allowed Delay, (b) advise the Investors in writing to
cease all sales under the Registration Statement until the end of the Allowed
Delay and (c) use commercially reasonable efforts to terminate an Allowed Delay
as promptly as practicable.

3. Company Obligations. The Company will use commercially reasonable efforts to
effect the registration of the Registrable Securities in accordance with the
terms hereof, and pursuant thereto the Company will, as expeditiously as
possible (but subject to Section 2(c)(ii)):

(a) use commercially reasonable efforts to cause such Registration Statement to
become effective and (subject to the provisions of Section 2(a)(ii) regarding
removal from registration by means of a post-effective amendment to the S-1
Registration Statement any of the Registrable Securities registered under the
S-1 Registration Statement that remain unsold at the time the S-3 Registration
Statement is declared effective), to remain continuously effective for a period
that will terminate upon the earlier of (i) the date on which all Registrable
Securities covered by such Registration Statement as amended from time to time,
have been sold, and (ii) the date on which all Registrable Securities covered by
such Registration Statement may be sold pursuant to Rule 144(k) (the
“Effectiveness Period”) and advise the Investors in writing when the
Effectiveness Period has expired;

(b) prepare and file with the SEC such amendments and post-effective amendments
to the Registration Statement and the Prospectus as may be necessary to keep the
Registration Statement effective for the Effectiveness Period and to comply with
the provisions of the 1933 Act and the 1934 Act with respect to the distribution
of all of the Registrable Securities covered thereby;

(c) use commercially reasonable efforts to (i) prevent the issuance of any stop
order or other suspension of effectiveness and, (ii) if such order is issued,
obtain the withdrawal of any such order at the earliest possible moment;

(d) prior to any public offering of Registrable Securities, use commercially
reasonable efforts to register or qualify or cooperate with the Investors and
their counsel in connection with the registration or qualification of such
Registrable Securities for offer and sale under the securities or blue sky laws
of such jurisdictions requested by the Investors and do any and all other
commercially reasonable acts or things necessary or advisable to enable the
distribution in such jurisdictions of the Registrable Securities covered by the
Registration Statement; provided, however, that the Company shall not be
required in connection therewith or as a condition thereto to (i) qualify to do
business in any jurisdiction where it would not otherwise be required to qualify
but for this Section 3(d), (ii) subject itself to general taxation in any
jurisdiction where it would not otherwise be so subject but for this
Section 3(d), or (iii) file a general consent to service of process in any such
jurisdiction;

(e) use commercially reasonable efforts to cause all Registrable Securities
covered by a Registration Statement to be listed on each securities exchange,
interdealer quotation system or other market on which similar securities issued
by the Company are then listed;

(f) promptly notify the Investors, at any time when a Prospectus relating to
Registrable Securities is required to be delivered under the 1933 Act (including
during any period when the Company is in compliance with Rule 172), upon
discovery that, or upon the happening of any event as a result of which, the
Prospectus included in a Registration Statement, as then in effect, includes an
untrue statement of a material fact or omits to state any material fact required
to be stated therein or necessary to make the statements therein not misleading
in light of the circumstances then existing, and at the request of any such
holder, promptly prepare, file with the SEC pursuant to Rule 172 and furnish to
such holder a supplement to or an amendment of such Prospectus as may be
necessary so that such Prospectus shall not include an untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein not misleading in light of the
circumstances then existing; and

(g) otherwise use commercially reasonable efforts to comply with all applicable
rules and regulations of the SEC under the 1933 Act and the 1934 Act, including
Rule 172, notify the Investors promptly if the Company no longer satisfies the
conditions of Rule 172 and take such other actions as may be reasonably
necessary to facilitate the registration of the Registrable Securities
hereunder; and make available to its security holders, as soon as reasonably
practicable, but not later than the Availability Date (as defined below), an
earnings statement covering a period of at least twelve (12) months, beginning
after the effective date of each Registration Statement, which earnings
statement shall satisfy the provisions of Section 11(a) of the 1933 Act,
including Rule 158 promulgated thereunder (for the purpose of this Section 3(g),
“Availability Date” means the 45th day following the end of the fourth fiscal
quarter that includes the effective date of such Registration Statement, except
that, if such fourth fiscal quarter is the last quarter of the Company’s fiscal
year, “Availability Date” means the 90th day after the end of such fourth fiscal
quarter).

(h) With a view to making available to the Investors the benefits of Rule 144
(or its successor rule) and any other rule or regulation of the SEC that may at
any time permit the Investors to sell shares of Common Stock to the public
without registration, the Company covenants and agrees to: (i) make and keep
public information available, as those terms are understood and defined in
Rule 144, until the earlier of (A) six months after such date as all of the
Registrable Securities may be resold pursuant to Rule 144(k) or any other rule
of similar effect or (B) such date as all of the Registrable Securities shall
have been resold; (ii) file with the SEC in a timely manner all reports and
other documents required of the Company under the 1934 Act; and (iii) furnish to
each Investor upon request, as long as such Investor owns any Registrable
Securities, (A) a written statement by the Company that it has complied with the
reporting requirements of the 1934 Act, and (B) such other information as may be
reasonably requested in order to avail such Investor of any rule or regulation
of the SEC that permits the selling of any such Registrable Securities without
registration.

(i) With a view to satisfying its obligations under Section 2(a)(ii), the
Company:

(i) represents and warrants that (A) since November 14, 2005 through the date of
this Agreement, it has filed with the SEC in a timely manner all reports and
other documents required of the Company under the 1934 Act (other than a report
that is required solely pursuant to Item 1.01, 1.02, 2.03, 2.04, 2.05, 2.06,
4.02(a), 6.01, 6.03 or 6.05 of SEC Form 8-K) and (B) neither the Company nor any
of its consolidated or unconsolidated subsidiaries have, since the end of the
last fiscal year for which certified financial statements of the Company and its
consolidated subsidiaries were included in a report filed pursuant to Section
13(a) or 15(d) of the 1934 Act through the date of this Agreement: (1) failed to
pay any dividend or sinking fund installment on preferred stock; or
(2) defaulted (x) on any installment or installments on indebtedness for
borrowed money, or (y) on any rental on one or more long term leases, which
defaults in the aggregate are material to the financial position of the Company
and its consolidated and unconsolidated subsidiaries, taken as a whole.

(ii) covenants and agrees that (A) from the date of this Agreement through the
effective date of S-3 Registration Statement, it will file with the SEC in a
timely manner all reports and other documents required of the Company under the
1934 Act (other than a report that is required solely pursuant to Item 1.01,
1.02, 2.03, 2.04, 2.05, 2.06, 4.02(a), 6.01, 6.03 or 6.05 of SEC Form 8-K) and
(B) neither the Company nor any of its consolidated or unconsolidated
subsidiaries will, from the end of the last fiscal year for which certified
financial statements of the Company and its consolidated subsidiaries are
included in a report filed pursuant to Section 13(a) or 15(d) of the 1934 Act
through the effective date of the S-3 Registration Statement: (1) fail to pay
any dividend or sinking fund installment on preferred stock; or (2) default
(x) on any installment or installments on indebtedness for borrowed money, or
(y) on any rental on one or more long term leases, which default in the
aggregate will be material to the financial position of the Company and its
consolidated and unconsolidated subsidiaries, taken as a whole.

4. Due Diligence Review; Information. Upon reasonable prior notice, the Company
shall make available, during normal business hours, for inspection and review by
the Investors, advisors to and representatives of the Investors (who may or may
not be affiliated with the Investors and who are reasonably acceptable to the
Company), all financial and other records, all SEC Filings (as defined in the
Purchase Agreement) and other filings with the SEC, and all other corporate
documents and properties of the Company as may be reasonably necessary for the
purpose of such review, and cause the Company’s officers, directors and
employees, within a reasonable time period, to supply all such information
reasonably requested by the Investors or any such representative, advisor or
underwriter in connection with such Registration Statement (including, without
limitation, in response to all questions and other inquiries reasonably made or
submitted by any of them), prior to and from time to time after the filing and
effectiveness of the Registration Statement for the sole purpose of enabling the
Investors and such representatives, advisors and underwriters and their
respective accountants and attorneys to conduct initial and ongoing due
diligence with respect to the Company and the accuracy of such Registration
Statement.

The Company shall not disclose material nonpublic information to the Investors,
or to advisors to or representatives of the Investors, unless prior to
disclosure of such information the Company identifies such information as being
material nonpublic information and provides the Investors, such advisors and
representatives with the opportunity to accept or refuse to accept such material
nonpublic information for review and any Investor wishing to obtain such
information enters into an appropriate confidentiality agreement with the
Company with respect thereto.

5. Obligations of the Investors.

(a) Each Investor shall promptly furnish in writing to the Company such
information regarding itself, the Registrable Securities held by it and the
intended method of disposition of the Registrable Securities held by it, as
shall be reasonably required to effect the registration of such Registrable
Securities and shall execute such documents in connection with such registration
as the Company may reasonably request. At least seven (7) Business Days prior to
the first anticipated filing date of any Registration Statement, the Company
shall notify each Investor of the information the Company requires from such
Investor if such Investor elects to have any of the Registrable Securities
included in the Registration Statement. An Investor shall provide such
information to the Company at least three (3) Business Days prior to the first
anticipated filing date of such Registration Statement if such Investor elects
to have any of the Registrable Securities included in the Registration
Statement.

(b) Each Investor, by its acceptance of the Registrable Securities agrees to
cooperate with the Company as reasonably requested by the Company in connection
with the preparation and filing of a Registration Statement hereunder, unless
such Investor has notified the Company in writing of its election to exclude all
of its Registrable Securities from such Registration Statement.

(c) Each Investor agrees that, upon receipt of any notice from the Company of
either (i) the commencement of an Allowed Delay pursuant to Section 2(c)(ii) or
(ii) the happening of an event pursuant to Section 3(f) hereof, such Investor
will immediately discontinue disposition of Registrable Securities pursuant to
the Registration Statement covering such Registrable Securities, until the
Investor is advised by the Company that a supplemented or amended prospectus has
been filed with the SEC and until any related post-effective amendment is
declared effective and, if so directed by the Company, the Investor shall
deliver to the Company or destroy (and deliver to the Company a certificate of
destruction) all copies in the Investor’s possession of the Prospectus covering
the Registrable Securities current at the time of receipt of such notice.

6. Indemnification.

(a) Indemnification by the Company. The Company will indemnify and hold harmless
each Investor and its officers, directors, members, employees, attorneys and
agents, successors and assigns, and each other person, if any, who controls such
Investor within the meaning of the 1933 Act, against any losses, claims, damages
or liabilities, joint or several, to which they may become subject under the
1933 Act or otherwise, insofar as such losses, claims, damages or liabilities
(or actions in respect thereof) arise out of or are based upon: (i) any untrue
statement or alleged untrue statement of any material fact contained in any
Registration Statement, any preliminary prospectus or final prospectus contained
therein, or any amendment or supplement thereof; (ii) any blue sky application
or other document executed by the Company specifically for that purpose or based
upon written information furnished by the Company filed in any state or other
jurisdiction in order to qualify any or all of the Registrable Securities under
the securities laws thereof (any such application, document or information
herein called a “Blue Sky Application”); (iii) 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; (iv) any violation by the Company or
its agents of any rule or regulation promulgated under the 1933 Act applicable
to the Company or its agents and relating to action or inaction required of the
Company in connection with such registration; or (v) any failure to register or
qualify the Registrable Securities included in any such Registration in any
state where the Company or its agents has affirmatively undertaken or agreed in
writing that the Company will undertake such registration or qualification on an
Investor’s behalf and will reimburse such Investor, and each such officer,
director or member and each such controlling person for any legal or other
expenses reasonably incurred by them in connection with investigating or
defending any such loss, claim, damage, liability or action; provided, however,
that the Company will not be liable in any such case if and to the extent that
any such loss, claim, damage or liability arises out of or is based upon an
untrue statement or alleged untrue statement or omission or alleged omission so
made in conformity with information furnished by such Investor or any such
controlling person in writing specifically for use in such Registration
Statement or Prospectus.

(b) Indemnification by the Investors. Each Investor agrees, severally but not
jointly, to indemnify and hold harmless, to the fullest extent permitted by law,
the Company, its directors, officers, employees, stockholders and each person
who controls the Company (within the meaning of the 1933 Act) against any
losses, claims, damages, liabilities and expense (including reasonable attorney
fees) resulting from any untrue statement of a material fact or any omission of
a material fact required to be stated in the Registration Statement or
Prospectus or preliminary prospectus or amendment or supplement thereto or
necessary to make the statements therein not misleading, to the extent, but only
to the extent that such untrue statement or omission is contained in any
information furnished in writing by such Investor to the Company specifically
for inclusion in such Registration Statement or Prospectus or amendment or
supplement thereto. In no event shall the liability of an Investor be greater in
amount than the dollar amount of the proceeds (net of all expense paid by such
Investor in connection with any claim relating to this Section 6 and the amount
of any damages such Investor has otherwise been required to pay by reason of
such untrue statement or omission) received by such Investor upon the sale of
the Registrable Securities included in the Registration Statement giving rise to
such indemnification obligation.

(c) Conduct of Indemnification Proceedings. Any person entitled to
indemnification hereunder shall (i) give prompt notice to the indemnifying party
of any claim with respect to which it seeks indemnification and (ii) permit such
indemnifying party to assume the defense of such claim with counsel reasonably
satisfactory to the indemnified party; provided that any person entitled to
indemnification hereunder shall have the right to employ separate counsel and to
participate in the defense of such claim, but the fees and expenses of such
counsel shall be at the expense of such person unless (a) the indemnifying party
has agreed to pay such fees or expenses, or (b) the indemnifying party shall
have failed to assume the defense of such claim and employ counsel reasonably
satisfactory to such person or (c) in the reasonable judgment of any such
person, based upon written advice of its counsel, a conflict of interest exists
between such person and the indemnifying party with respect to such claims (in
which case, if the person notifies the indemnifying party in writing that such
person elects to employ separate counsel at the expense of the indemnifying
party, the indemnifying party shall not have the right to assume the defense of
such claim on behalf of such person); and provided, further, that the failure of
any indemnified party to give notice as provided herein shall not relieve the
indemnifying party of its obligations hereunder, except to the extent that such
failure to give notice shall materially adversely affect the indemnifying party
in the defense of any such claim or litigation. It is understood that the
indemnifying party shall not, in connection with any proceeding in the same
jurisdiction, be liable for fees or expenses of more than one separate firm of
attorneys at any time for all such indemnified parties. No indemnifying party
will, except with the consent of the indemnified party, consent to entry of any
judgment or enter into any settlement that does not include as an unconditional
term thereof the giving by the claimant or plaintiff to such indemnified party
of a release from all liability in respect of such claim or litigation.

(d) Contribution. If for any reason the indemnification provided for in the
preceding paragraphs (a) and (b) is unavailable to an indemnified party or
insufficient to hold it harmless, other than as expressly specified therein,
then the indemnifying party shall contribute to the amount paid or payable by
the indemnified party as a result of such loss, claim, damage or liability in
such proportion as is appropriate to reflect the relative fault of the
indemnified party and the indemnifying party, as well as any other relevant
equitable considerations. No person guilty of fraudulent misrepresentation
within the meaning of Section 11(f) of the 1933 Act shall be entitled to
contribution from any person not guilty of such fraudulent misrepresentation. In
no event shall the contribution obligation of a holder of Registrable Securities
be greater in amount than the dollar amount of the proceeds (net of all expenses
paid by such holder in connection with any claim relating to this Section 6 and
the amount of any damages such holder has otherwise been required to pay by
reason of such untrue or alleged untrue statement or omission or alleged
omission) received by it upon the sale of the Registrable Securities giving rise
to such contribution obligation.

7. Miscellaneous.

(a) Amendments and Waivers. This Agreement may be amended, modified or waived
only by a writing signed by the Company and the Required Investors; provided
that if any such amendment, modification or waiver would adversely affect in any
material respect any Investor or group of Investors who have comparable rights
under this Agreement disproportionately to the other Investors having such
comparable rights, such amendment, modification, or waiver shall also require
the written consent of the Investor(s) so adversely affected.

(b) Notices. All notices and other communications provided for or permitted
hereunder shall be made as set forth in Section 9.4 of the Purchase Agreement.

(c) Assignments and Transfers by Investors. The provisions of this Agreement
shall be binding upon and inure to the benefit of the Investors and their
respective successors and assigns. An Investor may transfer or assign, in whole
or from time to time in part, to one or more persons its rights hereunder in
connection with the transfer of Registrable Securities by such Investor to such
person, provided that (i) such Investor complies with all laws applicable
thereto and provides written notice of assignment to the Company promptly after
such assignment is effected and (ii) the transferee agrees in writing to be
bound by this Agreement as if it were a party hereto.

(d) Assignments and Transfers by the Company. This Agreement may not be assigned
by the Company (whether by operation of law or otherwise) without the prior
written consent of the Required Investors, provided, however, that the Company
may assign its rights and delegate its duties hereunder to any surviving or
successor corporation in connection with a merger or consolidation of the
Company with another corporation, or a sale, transfer or other disposition of
all or substantially all of the Company’s assets to another corporation, without
the prior written consent of the Required Investors, after notice duly given by
the Company to each Investor.

(e) Benefits of the Agreement. The terms and conditions of this Agreement shall
inure to the benefit of and be binding upon the respective permitted successors
and assigns of the parties. Nothing in this Agreement, express or implied, is
intended to confer upon any party other than the parties hereto or their
respective successors and assigns any rights, remedies, obligations, or
liabilities under or by reason of this Agreement, except as expressly provided
in this Agreement.

(f) Counterparts; Faxes. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument. This Agreement may also
be executed via facsimile, which shall be deemed an original.

(g) Titles and Subtitles. The titles and subtitles used in this Agreement are
used for convenience only and are not to be considered in construing or
interpreting this Agreement.

(h) Severability. Any provision of this Agreement that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof but shall be interpreted as if it were written so as
to be enforceable to the maximum extent permitted by applicable law, and any
such prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction. To the extent
permitted by applicable law, the parties hereby waive any provision of law which
renders any provisions hereof prohibited or unenforceable in any respect.

(i) Further Assurances. The parties shall execute and deliver all such further
instruments and documents and take all such other actions as may reasonably be
required to carry out the transactions contemplated hereby and to evidence the
fulfillment of the agreements herein contained.

(j) Entire Agreement. This Agreement is intended by the parties as a final
expression of their agreement and intended to be a complete and exclusive
statement of the agreement and understanding of the parties hereto in respect of
the subject matter contained herein. This Agreement supersedes all prior
agreements and understandings between the parties with respect to such subject
matter.

(k) Governing Law; Consent to Jurisdiction; Waiver of Jury Trial. This Agreement
shall be governed by, and construed in accordance with, the internal laws of the
State of New York without regard to the choice of law principles thereof. Each
of the parties hereto irrevocably submits to the exclusive jurisdiction of the
courts of the State of New York located in New York County and the United States
District Court for the Southern District of New York for the purpose of any
suit, action, proceeding or judgment relating to or arising out of this
Agreement and the transactions contemplated hereby. Service of process in
connection with any such suit, action or proceeding may be served on each party
hereto anywhere in the world by the same methods as are specified for the giving
of notices under this Agreement. Each of the parties hereto irrevocably consents
to the jurisdiction of any such court in any such suit, action or proceeding and
to the laying of venue in such court. Each party hereto irrevocably waives any
objection to the laying of venue of any such suit, action or proceeding brought
in such courts and irrevocably waives any claim that any such suit, action or
proceeding brought in any such court has been brought in an inconvenient forum.
EACH OF THE PARTIES HERETO WAIVES ANY RIGHT TO REQUEST A TRIAL BY JURY IN ANY
LITIGATION WITH RESPECT TO THIS AGREEMENT AND REPRESENTS THAT COUNSEL HAS BEEN
CONSULTED SPECIFICALLY AS TO THIS WAIVER.

(l) Obligations of Investors. The Company acknowledges that the obligations of
each Investor under this Agreement are several and not joint with the
obligations of any other Investor, and no Investor shall be responsible in any
way for the performance of the obligations of any other Investor under this
Agreement. The decision of each Investor to enter into to this Agreement has
been made by such Investor independently of any other Investor. The Company
further acknowledges that nothing contained in this Agreement, and no action
taken by any Investor pursuant hereto, shall be deemed to constitute the
Investors as a partnership, an association, a joint venture or any other kind of
entity, or create a presumption that the Investors are in any way acting in
concert or as a group with respect to such obligations or the transactions
contemplated hereby. Each Investor shall be entitled to independently protect
and enforce its rights, including without limitation, the rights arising out of
this Agreement, and it shall not be necessary for any other Investor to be
joined as an additional party in any proceeding for such purpose.

Each Investor has been represented by its own separate legal counsel in their
review and negotiation of this Agreement and with respect to the transactions
contemplated hereby. The Company has elected to provide all Investors with the
same terms and Agreement for the convenience of the Company and not because it
was required or requested to do so by the Investors. The Company acknowledges
that such procedure with respect to this Agreement in no way creates a
presumption that the Investors are in any way acting in concert or as a group
with respect to this Agreement or the transactions contemplated hereby or
thereby.

[Signature pages follow]

19

IN WITNESS WHEREOF, the parties have executed this Agreement or caused their
duly authorized officers to execute this Agreement as of the date first above
written.

         
The Company:
  AVALON PHARMACEUTICALS, INC.

 
  By:_________________________

 
  Name:Kenneth C. Carter

 
  Title:President and Chief Executive Officer

20

         
The Investors:
  BIOTECHNOLOGY VALUE FUND, L.P.

 
  By: BVF Partners, L.P., its general partner

 
  By: BVF Inc., its general partner

 
  By: _______________________

 
  Mark N. Lampert, President

21

         
 
  BIOTECHNOLOGY VALUE FUND II, L.P.

 
  By: BVF Partners, L.P., its general partner

 
  By: BVF Inc., its general partner

 
  By:_________________________

 
  Name: Mark N. Lampert

 
  Title: President

22

         
 
  BVF INVESTMENTS, L.L.C.

 
  By: BVF Partners, L.P., its manager

 
  By: BVF Inc, its general partner

 
  By:_________________________

 
  Name: Mark N. Lampert

 
  Title: President

23

         
 
  INVESTMENT 10, L.L.C.

 
  By: BVF Partners, L.P., its attorney-in-fact

 
  By: BVF Inc., its general partner

 
  By:_________________________

 
  Name: Mark N. Lampert

 
  Title: President

24

         
 
  XMARK JV INVESTMENT PARTNERS, LLC

 
  By:_________________________

 
  Name: _____________________

 
  Title: _____________________

25

         
 
  XMARK OPPORTUNITY FUND, L.P.

 
  By:_________________________

 
  Name: _____________________

 
  Title: _____________________

26

         
 
  XMARK OPPORTUNITY FUND, LTD.

 
  By:_________________________

 
  Name: _____________________

 
  Title: _____________________

27

         
 
  FORT MASON MASTER, LP

 
  By:_________________________

 
  Name: _____________________

 
  Title: _____________________

28

         
 
  FORT MASON PARTNERS, LP

By:     
Name:      
Title:      

29

Exhibit A

Plan of Distribution

The selling stockholders, which as used herein includes donees, pledgees,
transferees or other successors-in-interest selling shares of common stock or
interests in shares of common stock received after the date of this prospectus
from a selling stockholder as a gift, pledge, partnership distribution or other
transfer, may, from time to time, sell, transfer or otherwise dispose of any or
all of their shares of common stock or interests in shares of common stock on
any stock exchange, market or trading facility on which the shares are traded or
in private transactions. These dispositions may be at fixed prices, at
prevailing market prices at the time of sale, at prices related to the
prevailing market price, at varying prices determined at the time of sale, or at
negotiated prices.

The selling stockholders may use any one or more of the following methods when
disposing of shares or interests therein:

• ordinary brokerage transactions and transactions in which the broker-dealer
solicits purchasers;

• block trades in which the broker-dealer will attempt to sell the shares as
agent, but may position and resell a portion of the block as principal to
facilitate the transaction;

• purchases by a broker-dealer as principal and resale by the broker-dealer for
its account;

• an exchange distribution in accordance with the rules of the applicable
exchange;

• privately negotiated transactions;

• short sales effected after the date the registration statement of which this
Prospectus is a part is declared effective by the SEC;

• through the writing or settlement of options or other hedging transactions,
whether through an options exchange or otherwise;

• broker-dealers may agree with the selling stockholders to sell a specified
number of such shares at a stipulated price per share; and

• a combination of any such methods of sale.

The selling stockholders may, from time to time, pledge or grant a security
interest in some or all of the shares of common stock owned by them and, if they
default in the performance of their secured obligations, the pledgees or secured
parties may offer and sell the shares of common stock, from time to time, under
this prospectus, or under an amendment or supplement to this prospectus under
Rule 424(b)(3) or other applicable provision of the Securities Act amending the
list of selling stockholders to include the pledgee, transferee or other
successors in interest as selling stockholders under this prospectus. The
selling stockholders also may transfer the shares of common stock in other
circumstances, in which case the transferees, pledgees or other successors in
interest will be the selling beneficial owners for purposes of this prospectus.

In connection with the sale of our common stock or interests therein, the
selling stockholders may enter into hedging transactions with broker-dealers or
other financial institutions, which may in turn engage in short sales of the
common stock in the course of hedging the positions they assume. The selling
stockholders may also sell shares of our common stock short and deliver these
securities to close out their short positions, or loan or pledge the common
stock to broker-dealers that in turn may sell these securities. The selling
stockholders may also enter into option or other transactions with
broker-dealers or other financial institutions or the creation of one or more
derivative securities which require the delivery to such broker-dealer or other
financial institution of shares offered by this prospectus, which shares such
broker-dealer or other financial institution may resell pursuant to this
prospectus (as supplemented or amended to reflect such transaction).

The aggregate proceeds to the selling stockholders from the sale of the common
stock offered by them will be the purchase price of the common stock less
discounts or commissions, if any. Each of the selling stockholders reserves the
right to accept and, together with their agents from time to time, to reject, in
whole or in part, any proposed purchase of common stock to be made directly or
through agents. We will not receive any of the proceeds from this offering.

The selling stockholders also may resell all or a portion of the shares in open
market transactions in reliance upon Rule 144 under the Securities Act of 1933,
provided that they meet the criteria and conform to the requirements of that
rule.

The selling stockholders and any underwriters, broker-dealers or agents that
participate in the sale of the common stock or interests therein may be
“underwriters” within the meaning of Section 2(11) of the Securities Act. Any
discounts, commissions, concessions or profit they earn on any resale of the
shares may be underwriting discounts and commissions under the Securities Act.
Selling stockholders who are “underwriters” within the meaning of Section 2(11)
of the Securities Act will be subject to the prospectus delivery requirements of
the Securities Act.

To the extent required, the shares of our common stock to be sold, the names of
the selling stockholders, the respective purchase prices and public offering
prices, the names of any agents, dealer or underwriter, any applicable
commissions or discounts with respect to a particular offer will be set forth in
an accompanying prospectus supplement or, if appropriate, a post-effective
amendment to the registration statement that includes this prospectus.

In order to comply with the securities laws of some states, if applicable, the
common stock may be sold in these jurisdictions only through registered or
licensed brokers or dealers. In addition, in some states the common stock may
not be sold unless it has been registered or qualified for sale or an exemption
from registration or qualification requirements is available and is complied
with.

We have advised the selling stockholders that the anti-manipulation rules of
Regulation M under the Exchange Act may apply to sales of shares in the market
and to the activities of the selling stockholders and their affiliates. In
addition, we will make copies of this prospectus (as it may be supplemented or
amended from time to time) available to the selling stockholders for the purpose
of satisfying the prospectus delivery requirements of the Securities Act. The
selling stockholders may indemnify any broker-dealer that participates in
transactions involving the sale of the shares against certain liabilities,
including liabilities arising under the Securities Act.

We have agreed to indemnify the selling stockholders against liabilities,
including liabilities under the Securities Act and state securities laws,
relating to the registration of the shares offered by this prospectus.

We have agreed with the selling stockholders to keep the registration statement
of which this prospectus constitutes a part effective until the earlier of
(1) such time as all of the shares covered by this prospectus have been disposed
of pursuant to and in accordance with the registration statement or (2) the date
on which the shares may be sold pursuant to Rule 144(k) of the Securities Act.

30

Exhibit B

Form of Legal Opinion

Counsel’s opinion shall be to substantially the following effect:

(a) The Company is validly existing as a corporation and in good standing as of
the date of the certificate specified in paragraph 5 of Schedule 1 attached
hereto under the DGCL.

(b) The Company is qualified to do business and in good standing as of the date
of the certificate identified in paragraph 6 of Schedule 1 attached hereto under
the MGCL.

(c) The Company has the corporate power to execute, deliver and perform the
Purchase Agreement and the Registration Rights Agreement. The execution,
delivery and performance by the Company of the Purchase Agreement and the
Registration Rights Agreement have been duly authorized by all necessary
corporate action of the Company.

(d) The Purchase Agreement and the Registration Rights Agreement (i) have been
duly executed and delivered on behalf of the Company and (ii) each constitutes a
valid and binding obligation of the Company, enforceable against the Company in
accordance with its terms (except that no opinion is expressed herein on the
binding nature or enforceability of provisions thereof regarding indemnification
or contribution for liabilities under the Securities Act).

(e) The execution, delivery and performance on the date hereof by the Company of
the Purchase Agreement and the Registration Rights Agreement do not (i) violate
the DGCL or the Company’s Certificate of Incorporation or Bylaws, (ii) violate
any provision of Applicable Federal Law or Applicable State Law, or (iii) to our
knowledge, breach or constitute a default under any agreement or contract to
which the Company is a party filed as an exhibit to the Registration Statement
pursuant to Regulation S-K Item 6.01(b)(10) (each a “Material Agreement”)
(except we express no opinion as to financial covenants in such Material
Agreements).

(f) The Shares have been duly authorized, and upon issuance against payment
therefor in accordance with the provisions of the Purchase Agreement and the
resolutions of the Board of Directors of the Company, the Shares to be issued
and sold to the Investors as contemplated under the Purchase Agreement will be
validly issued, fully paid and non-assessable.

(g) To our knowledge, no individual or entity is entitled to any preemptive
right with respect to the issuance of the Shares pursuant to (i) the terms of
the Company’s Certificate of Incorporation or Bylaws, (ii) the provisions of the
DGCL, or (iii) any Material Agreement.

(h) No approval or consent of, or registration or filing with, any federal
agency or Maryland State government agency or the Office of the Secretary of
State of Delaware is required to be obtained or made by the Company under the
DGCL, the Securities Act or other Applicable Federal Law or Applicable State Law
in connection with the execution, delivery and performance on the date hereof by
the Company of the Purchase Agreement and the Registration Rights Agreement,
except for the filing of a Form D under the Securities Act and the filings,
registrations and orders contemplated under the Registration Rights Agreement.

(i) To the extent that the registration requirements of the Securities Act are
applicable thereto, the sale of the Shares to the Investors as contemplated
under the Purchase Agreement is exempt from registration or qualification under
the Securities Act.

31