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                                                                    Exhibit 4.27
                                                May [15], 2005

PERSONAL AND CONFIDENTIAL

ADVENTRX Pharmaceuticals, Inc.
6725 Mesa Ridge Rd., Suite 100
San Diego, CA 92121


Dear Evan:

      This letter agreement (this "Agreement") will confirm the understanding
and agreement between CIBC World Markets Corp. ("CIBC World Markets") and
ADVENTRX Pharmaceuticals, Inc. (the "Company") as follows:

1.    ENGAGEMENT: The Company hereby engages CIBC World Markets as its lead
      private placement agent and book-runner in the private placement of one or
      more classes or series of securities of the Company to a limited number of
      sophisticated, accredited investors (the "Investors"). Such securities
      (the "Securities") may take the form of preferred or common stock of the
      Company or other equity-linked securities of the Company. Such placement
      shall be referred to as the "Transaction."

      The selection of each of the Investors from a list of potential Investors
      and the number of shares sold to each of such Investors shall be mutually
      agreed to by the Company and CIBC World Markets. The number and price of
      the Securities the Company shall ultimately agree to sell, pursuant to the
      Purchase Agreements (defined below), are entirely within the Company's
      discretion.

2.    CIBC WORLD MARKETS' ROLE: CIBC World Markets hereby accepts the engagement
      described herein and, in that connection, agrees to:

      (a)   assist in preparing a private placement memorandum or other similar
            or related documents (the "Placement Documents") describing the
            Company, the Securities and the Transaction;

      (b)   review with the Company a list of the Investors to whom the
            Placement Documents may be provided;

      (c)   assist in the preparation of other communications to be used in
            placing the Securities, whether in the form of letter, circular,
            notice or otherwise;

      (d)   assist and advise the Company with respect to the negotiation of the
            sale of the Securities to the Investors in the Transaction; and

      (e)   use reasonable efforts to form and manage a syndicate of private
            placements agents, which shall include CIBC World Markets and
            another agent or other agents (the "Additional Agents") chosen by
            the Company and agreed to by CIBC, subject to the approval of the
            appropriate committees at CIBC World Markets.

3.    DUE DILIGENCE: It is understood that CIBC World Markets' assistance in the
      Transaction will be subject to the satisfactory completion of such
      reasonable investigation and inquiry into the affairs of the Company as
      CIBC World Markets deems appropriate under the circumstances (such
      investigation hereinafter to be referred to as "Due Diligence") and the
      approval of CIBC World Markets' Commitment and Due Diligence Committees.
      CIBC World Markets shall have the right in its sole


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      discretion to terminate this Agreement if the outcome of the Due Diligence
      is not satisfactory to CIBC World Markets or if approval of the Commitment
      and Due Diligence Committees is not obtained ("Early Termination").

4.    TERM; EXCLUSIVITY: This engagement will commence on the date hereof and
      terminate on the earlier to occur of (i) Early Termination, (ii) the
      Closing (as defined below) or (iii) the date on which a party receives
      written notice from the other party of termination of this engagement.
      During CIBC World Markets' engagement hereunder: (i) the Company will not,
      and will not permit its representatives to, other than in coordination
      with CIBC World Markets, contact or solicit institutions, corporations or
      other entities as potential purchasers of the Securities and (ii) the
      Company will not pursue any equity or debt financing transaction which
      would be in lieu of a Transaction. Furthermore, the Company agrees that
      during CIBC World Markets' engagement hereunder, all inquiries, whether
      direct or indirect, from prospective Investors will be referred to CIBC
      World Markets and will be deemed to have been contacted by CIBC World
      Markets in connection with the Transaction. The Company may reject any
      potential Investor if in its discretion, the Company believes that the
      inclusion of such Investor in the Company would be incompatible with the
      best interests of the Company. The Company shall not be obligated to sell
      the Securities or to accept any offer thereof, and the terms of such
      Securities and the final decision to issue the same shall be subject to
      the discretionary approval of the Company. Notwithstanding the foregoing
      or anything else to the contrary in this Agreement, the Company shall not
      be prohibited from (a) contacting or corresponding with any of its
      warrantholders or optionholders with respect to the exercise of warrants
      or options to purchase shares of common stock of the Company ("Derivative
      Exercises") and (b) negotiating or entering into any transaction pursuant
      to which the Company may sell, license to or otherwise transfer or assign
      rights to any of its real or intangible properties to or agree to develop
      any products, technology or intellectual property for or with a third
      party (a "Strategic Transaction"). CIBC World Markets agrees that no
      Derivative Exercise and no Strategic Transaction shall be deemed a
      "Transaction" for purposes of this Agreement and no "Transaction Fee"
      shall be payable with respect to any Derivative Exercise or Strategic
      Transaction.

      Either party may terminate this Agreement at any time. Upon any
      termination of this Agreement, the Company shall pay to CIBC World
      Markets, on behalf of the syndicate, all fees earned and reimburse CIBC
      World Markets for all reasonable expenses incurred, in accordance with
      Paragraphs 8 and 9 hereof, respectively. The Company agrees to pay CIBC
      World Markets any fees specified in Paragraph 8. Any obligation pursuant
      to this Paragraph 4 shall survive the termination of this Agreement.

      No offers or sales of any securities of the same or similar class as the
      Securities will be made by the Company or any affiliate during the
      six-month period after the completion of the offering of the Securities in
      each case except in compliance with the registration requirements of the
      Securities Act of 1933, as amended (the "Securities Act"), or an exemption
      therefrom.

5.    BEST EFFORTS: It is understood that CIBC World Markets' involvement in the
      Transaction is strictly on a best efforts basis and that the consummation
      of the Transaction will be subject to, among other things, market
      conditions.

6.    INFORMATION: The Company shall furnish, or cause to be furnished, to CIBC
      World Markets all information requested by CIBC World Markets that is
      reasonably necessary for the purpose of rendering services hereunder (all
      such information being the "Information"). In addition, the Company agrees
      to make available to CIBC World Markets upon request from time to time the
      officers, directors, accountants, counsel and other advisors of the
      Company. The Company recognizes and confirms that CIBC World Markets (a)
      will use and rely on the Information, including the Placement Documents,
      and on information available from generally recognized public sources in
      performing the services contemplated by this Agreement without having
      independently verified the


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      same; (b) does not assume responsibility for the accuracy or completeness
      of the Placement Documents or the Information and such other information;
      and (c) will not make an appraisal of any of the assets or liabilities of
      the Company.

      The Company represents and warrants to CIBC World Markets that: (i) all
      such Information, including the Placement Documents, any documents
      attached as exhibits thereto and/or incorporated by reference therein, and
      any communications prepared pursuant to paragraph 2(c) above will be true
      and accurate in all material respects and does not and will not contain
      any untrue statement of a material fact or omit to state a material fact
      necessary in order to make the statements made, in the light of the
      circumstances under which they were made, not misleading; and (ii) any
      projected financial information or other forward-looking information which
      the Company provides to CIBC World Markets will be made by the Company in
      good faith, based on management's best estimates then available and based
      on facts and assumptions which the Company believes to be reasonable. Upon
      reasonable request, the Company will meet with CIBC World Markets or its
      representatives to discuss all information relevant for disclosure in the
      Placement Documents and will cooperate in any investigation undertaken by
      CIBC World Markets thereof, including any document included or
      incorporated by reference therein. CIBC World Markets agrees that it shall
      not distribute any Information or Placement Documents to any potential
      Investor without the approval of the Company to distribute such
      Information or Placement Documents. The Company agrees that if any
      Information furnished by it to CIBC World Markets in connection with this
      Agreement shall, in whole or in part, become materially inaccurate,
      misleading or incomplete during the term of CIBC World Markets' engagement
      hereunder, the Company shall promptly so advise CIBC World Markets in
      writing and correct any such inaccuracy or omission.

7.    RESPONSIBILITIES, REPRESENTATIONS AND WARRANTIES:

      (a)   The sale of Securities to any Investor will be made pursuant to a
            purchase agreement ("Purchase Agreement") between the Company and
            such Investor in substantially the form attached hereto as Exhibit
            A. Prior to the signing of any Purchase Agreement, officers of the
            Company with responsibility for financial affairs will be available
            to answer inquiries from prospective investors.

      (b)   The selling price of the Securities to be issued and sold by the
            Company pursuant to the Purchase Agreements will be specified in
            writing by CIBC World Markets on behalf of the Company to the
            prospective investors prior to the execution of the Purchase
            Agreements, subject to the Company's approval.

      (c)   Subsequent to the full execution of a Purchase Agreement, the
            Company shall perform its obligations under such Purchase Agreement.
            The Purchase Agreements will require the Company to file, promptly,
            and in any event within 45 days, after the closing of the sale of
            the Securities contemplated by the Purchase Agreements, (the
            "Closing") a registration statement with the Securities and Exchange
            Commission (the "SEC") for the resale from time to time of the
            Securities to be issued pursuant to such Purchase Agreements (the
            "Registration Statement"), and to use reasonable best efforts to
            have such registration statement declared effective by the SEC
            within 90 days of the Closing.

      (d)   The Company (i) represents and warrants that the representations and
            warranties contained in the Purchase Agreements will be true and
            correct in all respects on the date of such Purchase Agreements and
            on the Closing date and (ii) agrees that CIBC World Markets shall be
            entitled to rely on such representations and warranties as if they
            were made directly to CIBC World Markets.

      (e)   The Company agrees that the Company shall have sole responsibility
            for ensuring that the sale


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            of Securities contemplated by this Agreement shall be exempt from
            the registration requirements of the Securities Act, and will
            otherwise comply with the securities laws of any applicable country
            or other jurisdiction; provided, that CIBC World Markets shall have
            received the Company's advance approval, not to be unreasonably
            withheld, of all jurisdictions in which CIBC World Markets intends
            to offer or sell the Securities. The Company shall not take any
            action or permit to be taken any action on its behalf that would
            cause such sale of Securities to fail to (i) qualify for such an
            exemption, or (ii) otherwise comply with such securities laws. Each
            of Company and CIBC World Markets hereby represent, warrant and
            covenant to the other that the it has not, and agrees that it will
            not, directly or indirectly, engage in any form of general
            solicitation, general advertising or directed selling efforts in
            connection with the Transaction.

      (f)   At the Closing, the Company will cause its independent public
            accountants to address and deliver to the Company and CIBC World
            Markets a letter or letters (which letters are frequently referred
            to as "Comfort Letters") dated as of the Closing, which letter or
            letters shall be in the form reasonably satisfactory to CIBC World
            Markets.

      (g)   At the Closing, the Company will cause its counsel to address and
            deliver to the Company and CIBC World Markets an opinion reasonably
            satisfactory to CIBC World Markets dated as of the Closing, and
            substantially in the form attached hereto as Exhibit B with respect
            to such matters as are customarily opined to in transactions similar
            to the Transaction which CIBC World Markets and its counsel shall
            reasonably request, including an opinion that the offering and sale
            of the Securities are not required to be registered under the
            Securities Act. In rendering such opinion, such counsel may rely
            upon the representations and warranties of the purchasers contained
            in the Purchase Agreements and upon certificates from officers of
            the Company as to factual matters.

      (h)   The Company acknowledges that the Purchase Agreements will require
            the Company's counsel to deliver one or more opinions to the
            Investors. The Company agrees that CIBC World Markets shall be
            entitled to rely on any opinions delivered to the Investors in
            connection with the Transaction and resale of the Securities under
            the Registration Statement.

      (i)   For a period of ninety (90) days from the effective date of the
            Registration Statement, the Company will not, without the prior
            written consent of CIBC World Markets, sell, contract to sell or
            otherwise dispose of or issue any securities of the Company, except
            pursuant to previously issued options, any agreements providing for
            anti-dilution or other stock purchase or share issuance rights in
            existence on the date hereof, any employee benefit or similar plan
            of the Company in existence on the date hereof or duly adopted
            hereafter, or any technology license agreement, strategic alliance
            or joint venture in existence on the date hereof or which the
            Company may enter into hereafter.

      (j)   Each director and executive officer of the Company and each
            stockholder of the Company listed on Exhibit C-1 shall, prior to the
            Closing, have delivered to CIBC World Markets his or her enforceable
            written lock-up agreement in the form attached hereto as Exhibit
            C-2.

      (k)   At the Closing, CIBC World Markets shall receive a certificate,
            addressed to it and dated the Closing date, of the chief executive
            or chief operating officer and the chief financial officer of the
            Company to the effect that: (i) the representations, warranties and
            agreements of the Company in the Purchase Agreement were true and
            correct when made and are true and correct as of the Closing date;
            (ii) the Company has performed all covenants and agreements and
            satisfied all conditions contained in the Purchase Agreement; (iii)
            they have carefully examined the Placement Documents and, in their
            opinion (A) the Placement Documents did not include any untrue
            statement of a material fact


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            and did not omit to state a material fact required to be stated
            therein or necessary to make the statements therein, in light of the
            circumstances under which they were made, not misleading, and (B) no
            event has occurred which should have been set forth in a supplement
            or otherwise required an amendment to the Placement Documents; and
            (iv) no stop order suspending the effectiveness of any registration
            statement of the Company has been issued and, to their knowledge, no
            proceedings for that purpose have been instituted or are pending
            under the Securities Act.

      (l)   The Company shall furnish or cause to be furnished to CIBC World
            Markets at Closing copies of such additional certificates, opinions
            and other documents as CIBC World Markets shall reasonably request.

      (m)   The Company agrees it will not consummate the sale of the Securities
            unless it delivers or causes to be delivered the terms described in
            paragraphs (f), (g), (j), (k) and (l) above to CIBC World Markets at
            the Closing.

8.    FEES: As compensation for the services to be rendered by CIBC World
      Markets hereunder, the Company will pay CIBC World Markets, at the Closing
      or any other closing of the sale of any securities during the term of this
      agreement other than pursuant to a Derivative Exercise or a Strategic
      Transaction, from the proceeds of the sale of the Securities, a
      transaction fee (the "Transaction Fee") equal to 7.0% of the gross
      proceeds raised from the sale of the Securities; provided, however, that
      CIBC World Markets shall pay 20% of the Transaction Fee to the Additional
      Agents (in accordance with standard syndicate settlement procedures)
      allocated amongst the Additional Agents pursuant to written instructions
      from the Company to CIBC World Markets, which allocation shall be
      determined at the discretion of the Company. Further, the Company will pay
      CIBC World Markets the Transaction Fee (a "Tail Fee"), if within twelve
      months after the termination of this Agreement, the Company reaches an
      agreement for the sale of the Securities to any Investors which CIBC World
      Markets previously solicited or sought to solicit (but were not permitted
      to do so due to the Company's rejection of such proposed Investors
      pursuant to Section 4 hereof) on its behalf, provided, however, that if
      Early Termination occurs or if the Closing shall not have occurred and the
      Company terminates this Agreement after December 31, 2005, then the
      Company shall have no obligation to pay CIBC World Markets a Tail Fee with
      respect to any sale of Securities after such termination. Upon the
      Company's request, at the termination of this Agreement, CIBC World
      Markets will supply the Company with a list of Investors which CIBC World
      Markets has solicited including any Investors which first contacted the
      Company or sought to solicit (but were not permitted to do so due to the
      Company's rejection of such proposed Investors pursuant to Section 4
      hereof) on its behalf. The Company's obligations hereunder shall survive
      the termination of this Agreement.

9.    EXPENSE REIMBURSEMENT: The Company agrees to reimburse CIBC World Markets
      for all of its reasonable out-of-pocket expenses in connection with the
      performance of its activities under the terms of this Agreement.
      Reasonable out-of-pocket expenses include, but are not limited to, costs
      such as printing, telephone, telex, courier service, direct computer
      expenses, accommodations and travel. The Company will reimburse CIBC World
      Markets for fees and expenses of legal counsel employed by and for CIBC
      World Markets, if any, in connection with this Agreement. All such fees,
      expenses and costs shall be payable at the earlier of termination of this
      Agreement or Closing. The parties' obligations under this paragraph shall
      survive the termination of this Agreement.

10.   INDEMNITY: In addition to the fees and reimbursement of expenses provided
      for above, the parties agree to the indemnification and contribution
      provisions set forth as Annex A hereto, which are incorporated herein by
      reference as if fully set forth below. The parties' obligations under this
      paragraph shall survive the termination of this Agreement.

11.   GOVERNING LAWS: This Agreement will be governed by and construed in
      accordance with the laws of the State of New York applicable to agreements
      made and to be fully performed therein. The


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      Company irrevocably submits to the jurisdiction of any court of the State
      of New York located in the City and County of New York or in the United
      States District Court for the Southern District of New York for the
      purpose of any suit, action or other proceeding arising out of this
      Agreement or our engagement hereunder.

      Each of the Company and CIBC World Markets hereby waives any right it may
      have to a trial by jury in respect of any claim brought by or on behalf of
      either party based upon, arising out of or in connection with this
      Agreement, our engagement hereunder or the transactions contemplated
      hereby.

12.   RIGHT OF FIRST REFUSAL: In consideration for CIBC World Markets' agreement
      to act as lead placement agent in connection with the Transaction, the
      Company hereby grants CIBC World Markets a right of first refusal to serve
      as the Company's exclusive financial advisor and investment banker if in
      connection with any M&A and/or other financial transaction (other than
      customary commercial bank lending) the Company shall determine, in its
      sole discretion, to engage a financial advisor or investment banker to
      provide services in connection with such transaction. Such right of first
      refusal shall expire 12 months after the Closing. In the event the Company
      advises CIBC World Markets that it desires to engage a financial advisor
      or an investment banker in connection with any M&A and/or other financial
      transaction (other than customary commercial bank lending), the Company
      and CIBC World Markets will negotiate in good faith the terms of CIBC
      World Markets' engagement in a separate agreement, which agreement would
      set forth, among other matters, compensation for CIBC World Markets based
      upon customary fees for the services provided. The Company's obligation
      under this Paragraph 12 shall become effective only if Closings shall
      occur pursuant to which the Company shall receive aggregate gross proceeds
      of at least $15,000,000 and shall survive the termination of this
      Agreement.

13.   CONFIDENTIALITY: Except as required by law, this Agreement and the
      services and advice to be provided by CIBC World Markets hereunder, shall
      not be disclosed to third parties without CIBC World Markets' prior
      written permission. Notwithstanding the foregoing, but subject to the
      reasonable approval of the Company, CIBC World Markets shall be permitted
      to advertise the services it provided in connection with the private
      placement subsequent to the consummation of the private placement. Such
      expense shall not be reimbursable under paragraph 9 hereof.

14.   NO BROKERS: The Company represents and warrants to CIBC World Markets that
      other than the Additional Agents there are no brokers, representatives or
      other persons which have an interest in compensation due to CIBC World
      Markets from any transaction contemplated herein or which would otherwise
      be due any fee, commission or remuneration upon consummation of any
      Transaction.

15.   AUTHORIZATION: The Company and CIBC World Markets represent and warrant
      that each has all requisite power and authority to enter into and carry
      out the terms and provisions of this Agreement and the execution, delivery
      and performance of this Agreement does not breach or conflict with any
      agreement, document or instrument to which it is a party or bound, and
      each such party, with respect only to itself, further represents and
      warrants that this Agreement has been duly and validly authorized,
      executed and delivered by and constitutes and will constitute legal, valid
      and binding obligations enforceable against itself in accordance with the
      terms hereof, except as the enforceability thereof may be limited by
      bankruptcy, insolvency, reorganization, moratorium or other similar laws
      affecting the enforcement of creditors' rights generally and by general
      equitable principles.

16.   ANTI-MONEY LAUNDERING: To help the United States government fight the
      funding of terrorism and money laundering activities, the federal law of
      the United States requires all financial institutions to obtain, verify
      and record information that identifies each person with whom they do
      business. This means we must ask you for certain identifying information,
      including a government-issued identification number (e.g., a U.S. taxpayer
      identification number) and such other information or documents that we
      consider appropriate to verify your identity, such as certified articles
      of


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      incorporation, a government-issued business license, a partnership
      agreement or a trust instrument.

17.   NO FIDUCIARY RELATIONSHIP; BENEFICIARIES: It is understood that CIBC World
      Markets is engaged hereunder solely to provide the services described
      above to the Company and that CIBC World Markets is not acting as an agent
      or a fiduciary of, and shall have no duties or liabilities to, the equity
      or debt holders of the Company or any third party in connection with its
      engagement hereunder, all of which are expressly waived. No one other than
      the Company is authorized to rely upon the engagement of CIBC World
      Markets hereunder or any statements, advice, opinions or conduct by CIBC
      World Markets. The Company acknowledges and agrees that CIBC World Markets
      has no authority to bind the Company. The Company further acknowledges and
      agrees that CIBC World Markets is not engaged hereunder to underwrite or
      purchase any securities or otherwise provide any financing.

18.   MISCELLANEOUS: This Agreement constitutes the entire understanding and
      agreement between the Company and CIBC World Markets with respect to the
      subject matter hereof and supersedes all prior understanding or agreements
      between the parties with respect thereto, whether oral or written, express
      or implied. Any amendments or modifications must be executed in writing by
      both parties. It is understood and agreed that CIBC World Markets'
      services hereunder will not include providing any tax advice or developing
      any tax strategies for the Company. This Agreement and all rights,
      liabilities and obligations hereunder shall be binding upon and inure to
      the benefit of each party's successors but may not be assigned without the
      prior written approval of the other party. This Agreement may be executed
      in any number of counterparts, each of which shall be deemed to be an
      original, but such counterparts shall, together, constitute only one
      instrument. The descriptive headings of the Paragraphs of this Agreement
      are inserted for convenience only, do not constitute a part of this
      Agreement and shall not affect in anyway the meaning or interpretation of
      this Agreement.

      If all the foregoing is acceptable to you, please so indicate by signing
in the space provided below and returning a signed copy of this letter to us for
our records.

      CIBC World Markets is delighted to accept this engagement and looks
forward to working with you. Please confirm that the foregoing correctly sets
forth our agreement by signing the enclosed duplicate of this letter in the
space provided and returning it, whereupon this letter shall constitute a
binding agreement as of the date first above written.

                                          Very truly yours,

                                          CIBC World Markets Corp.

                                          BY:
                                                ----------------------
                                                Michael Brinkman
                                                Managing Director

ACCEPTED AND AGREED TO
AS OF THE ABOVE DATE:

            ADVENTRX Pharmaceuticals, Inc.


BY:
            -------------------------------
            Evan M. Levine
            President & CEO


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                            ANNEX A: INDEMNIFICATION

The Company agrees to indemnify and hold harmless CIBC World Markets and its
affiliates and their respective present and former directors, officers,
employees, agents and controlling persons (each such person, including CIBC
World Markets, an "Indemnified Party") to the extent fully permitted by law from
and against any losses, claims, damages and liabilities, joint or several
(collectively, the "Damages"), to which such Indemnified Party may become
subject in connection with or otherwise relating to or arising from (i) any
transaction contemplated by this letter agreement or the engagement of or
performance of services by an Indemnified Party thereunder or (ii) an untrue
statement or an alleged untrue statement of a material fact or the omission or
alleged omission to state a material fact necessary in order to make a statement
not misleading in light of the circumstances under which it was made, and will
reimburse each Indemnified Party for all fees and expenses (including the
reasonable fees and expenses of counsel) (collectively, "Expenses") as incurred
in connection with investigating, preparing, pursuing or defending any
threatened or pending claim, action, proceeding or investigation (collectively,
the "Proceedings") arising therefrom, whether or not such Indemnified Party is a
formal party to such Proceeding, and in enforcing this letter agreement;
provided, that the Company will not be liable to any such Indemnified Party to
the extent that any Damages are found in a final judgment of a court of
competent jurisdiction (which judgment is not appealed or is not appealable) to
have resulted primarily from the gross negligence or willful misconduct of the
Indemnified Party seeking indemnification hereunder. The Company also agrees
that no Indemnified Party will have any liability (whether direct or indirect,
in contract, tort or otherwise) to the Company or any person asserting claims on
behalf of the Company arising out of or in connection with any transactions
contemplated by this letter agreement or the engagement of or performance of
services by any Indemnified Party thereunder except to the extent that any
Damages are found in a final judgment of a court of competent jurisdiction
(which judgment is not appealed or is not appealable) to have resulted primarily
from the gross negligence or willful misconduct of the Indemnified Party.

If for any reason other than in accordance with this letter agreement, the
foregoing indemnity is unavailable to an Indemnified Party or insufficient to
hold an Indemnified Party harmless, then the Company will contribute to the
amount paid or payable by an Indemnified Party as a result of such Damages
(including all Expenses incurred) in such proportion as is appropriate to
reflect the relative benefits to the Company and/or its stockholders on the one
hand, and CIBC World Markets on the other hand, in connection with the matters
covered by this letter agreement or, if the foregoing allocation is not
permitted by applicable law, not only such relative benefits but also the
relative faults of such parties as well as any relevant equitable
considerations; provided, that the Company will not be liable to contribute to
the amount paid or payable by any such Indemnified Party to the extent that any
Damages are found in a final judgment of a court of competent jurisdiction
(which judgment is not appealed or is not appealable) to have resulted primarily
from the gross negligence or willful misconduct of the Indemnified Party seeking
contribution hereunder. The Company agrees that for purposes of this paragraph
the relative benefits to the Company and/or its stockholders and CIBC World
Markets in connection with the matters covered by this letter agreement will be
deemed to be in the same proportion that the total value paid or received or to
be paid or received by the Company and/or its stockholders in connection with
the Transactions contemplated by to this letter agreement, whether or not
consummated, bears to the fees paid to CIBC World Markets under this letter
agreement; provided, that in no event will the total contribution of all
Indemnified Parties to all such Damages exceed the amount of fees actually
received and retained by CIBC World Markets under this letter agreement
(excluding any amounts received by CIBC World Markets as reimbursement of
expenses). Relative fault shall be determined by reference to, among other
things, whether any untrue statement or omission or any conduct relates to
information provided by the Company or other conduct by the Company (or its
employees or other agents) on the one hand, or by CIBC World Markets, on the
other hand.

The Company agrees not to enter into any waiver, release or settlement of any
Proceeding (whether or not CIBC World Markets or any other Indemnified Party is
a formal party to such Proceeding) in respect of which indemnification may be
sought hereunder without the prior written consent of CIBC World Markets (which
consent will not be unreasonably withheld), unless such waiver, release or
settlement (i) includes an unconditional release of CIBC World Markets and each
Indemnified Party from all liability arising out of such Proceeding and (ii)
does not contain any factual or legal admission by or with respect to any
Indemnified Party or any adverse statement with respect to the character,
professionalism, expertise or reputation of any Indemnified Party or any action
or inaction of any Indemnified Party.

The indemnity, reimbursement and contribution obligations of the Company
hereunder will be in addition to any liability which the Company may have at
common law or otherwise to any Indemnified Party and will be binding upon and
inure to the benefit of any successors, assigns, heirs and personal
representatives of the Company or an Indemnified Party. The provisions of this
Annex will survive the modification or termination of this letter agreement.


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                                    EXHIBIT A
                           FORM OF PURCHASE AGREEMENT


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                                    EXHIBIT B
                              FORM OF LEGAL OPINION


                                       10
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                                   EXHIBIT C-1
                      PERSONS PROVIDING LOCK-UP AGREEMENTS

Evan Levine
M. Ross Johnson, Ph.D.
Carrie E. Carlander
Joan M. Robbins
Brian Culley
Cellia Habita
Michael M. Goldberg, M.D.
Mark J. Pykett, V.M.D., Ph.D.
Mark Bagnall, CPA


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                                   EXHIBIT C-2
                            FORM OF LOCK-UP AGREEMENT


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