<PAGE>


                                                                  EXHIBIT 10.104





                            NEXELL THERAPEUTICS, INC.
                          RETENTION AND SEVERANCE PLAN
                            FOR SENIOR STAFF MEMBERS
                                       AND
                            SUMMARY PLAN DESCRIPTION




<PAGE>




                            NEXELL THERAPEUTICS, INC.
                          RETENTION AND SEVERANCE PLAN
                            FOR SENIOR STAFF MEMBERS
                          AND SUMMARY PLAN DESCRIPTION

Effective July 24, 2001, this document outlines the terms and conditions of the
Nexell Therapeutics, Inc. Retention and Severance Plan for Senior Staff Members
maintained by Nexell Therapeutics, Inc. to provide severance benefits and
certain bonus payments to eligible employees of the Company in anticipation of
their termination of employment. This document shall serve as both the plan
document and the summary plan description, as such terms are defined under the
Employee Retirement Income Security Act of 1974, as amended ("ERISA") and the
regulations issued thereunder. The Plan is intended to qualify as an employee
welfare benefit plan under ERISA, and it shall be interpreted and construed in a
manner consistent with such intention.

                                    ARTICLE I
                                   DEFINITIONS

The following capitalized words and phrases, when used in the text of the Plan
document, shall have the meanings set forth below. Words used in the Plan in the
singular shall include the plural and in the plural the singular and the gender
of words used shall be construed to include whichever gender may be appropriate
under any particular circumstances.

1.1      Annual Base Pay
         ---------------

         "Annual Base Pay" means the Participant's annual base salary or wages
         in effect on the date of the Participant's termination of employment
         with the Company, exclusive of overtime pay, incentive payments, bonus
         payments, commissions and other miscellaneous payments.

1.2      Board
         -----

         "Board" means the Board of Directors of the Company or any individual
         or committee appointed by the Board of Directors of the Company and
         vested with the authority to carry out the duties as allocated to the
         Board of Directors of the Company in the Plan or otherwise by the Board
         of Directors of the Company.

1.3      COBRA Contribution Benefit
         --------------------------

         "COBRA Contribution Benefit" means the benefit described in, and
         subject to the terms of, Section 2.2(b).

1.4      Code
         ----
         "Code" means the Internal Revenue Code of 1986, as amended.

<PAGE>


1.5      Company
         -------

         "Company" means Nexell Therapeutics, Inc., or any successor entity
         thereof.

1.6      Discretionary Bonus
         -------------------

         "Discretionary Bonus" means the benefit described in, and subject to
         the terms of, Section 5.

1.7      Employee
         --------

         "Employee" means a person who is classified by the Company as an
         employee and who is designated by the Company as a member of the
         Company's senior staff, but excluding the Chief Executive Officer of
         the Company.

1.8      Outplacement Benefit
         --------------------

         "Outplacement Benefit" means the benefit described in, and subject to
         the terms of, Section 2.2(c).

1.9      Participant
         -----------

         "Participant" means an Employee who is entitled to receive a Severance
         Benefit, a Retention Bonus, a Performance Bonus or a Discretionary
         Bonus.

1.10     Performance Bonus
         -----------------

         "Performance Bonus" means the benefit described in, and subject to the
         terms of, Section 4.

1.11     Performance Milestones
         ----------------------

         "Performance Milestones" means the criteria, as described in Section
         4.1(c), that must be satisfied in order for an otherwise eligible
         Employee to receive a Performance Bonus.

1.12     Plan
         ----

         "Plan" means the Nexell Therapeutics, Inc. Retention and Severance Plan
         for Senior Staff Members as set forth herein and as may be amended from
         time to time.

1.13     Retention Bonus
         ---------------

         "Retention Bonus" means the benefit described in, and subject to the
         terms of, Section 3.

<PAGE>



1.14     Severance Benefit
         -----------------

         "Severance Benefit" means the benefit described in, and subject to the
         terms of, Section 2.

1.15     Severance Payment
         -----------------

         "Severance Payment" means the benefit described in, and subject to the
         terms of, Section 2.2(a).

1.16     Weekly Base Pay
         ---------------

         "Weekly Base Pay" means the Participant's base salary or wages in
         effect on the date of the Participant's termination of employment with
         the Company, exclusive of overtime pay, incentive payments, bonus
         payments, commissions and other miscellaneous payments, appropriately
         converted to a weekly amount.

                                    SECTION 2
                               SEVERANCE BENEFITS

2.1      Eligibility. An Employee whose employment with the Company is
         -----------
         involuntarily terminated on or after July 24, 2001 but no later than
         June 15, 2002, other than for cause as defined below, shall be eligible
         to receive a Severance Benefit. Involuntary termination of employment,
         other than for cause, for purposes of the Plan includes but is not
         limited to job elimination or staff reductions. Notwithstanding the
         preceding sentence, an Employee whose employment termination is
         described in subsections (a), (b) and (c) of this Section 2.1 shall not
         be eligible to receive a Severance Benefit.

         (a)      Involuntary Termination for Cause. An Employee whose
                  ---------------------------------
                  employment with the Company is involuntarily terminated for
                  cause will not be eligible to receive a Severance Benefit.
                  Involuntary termination of employment for cause for purposes
                  of the Plan and as determined by the Company includes but is
                  not limited to unsatisfactory job performance, violation of
                  the Company's policies or other misconduct, as determined
                  within the sole and absolute discretion of the Board.

         (b)      Voluntary Termination.  As determined by the Company, an
                  ----------------------
                  Employee who voluntarily terminates employment with the
                  Company is not eligible to receive a Severance Benefit.

         (c)      Employment Continuation. As determined by the Company, an
                  -----------------------
                  Employee whose employment with the Company is involuntarily
                  terminated but who has received an offer of regular or
                  transitional employment from Baxter as of the date of such
                  termination of employment with the Company will not be
                  eligible to receive a Severance Benefit.

<PAGE>



2.2      Severance Benefit. An Employee entitled to receive a Severance Benefit
         ------------------
         under Section 2.1 shall receive the following benefits:

         (a)      Severance Payment. The Severance Payment shall be a lump sum
                  -----------------
                  payment equal to a multiple of the Employee's Weekly Base Pay.
                  The multiple shall not be less than two (2) or greater than
                  eight (8) and shall be determined in the sole discretion of
                  the Board based on the Employee's position at the time of his
                  or her termination of employment.

         (b)      COBRA Contribution Benefit. With respect to an Employee
                  ----------------------------
                  participating  in a group  health plan  sponsored by the
                  Company on the date of his or her termination of employment,
                  the COBRA  Contribution  Benefit shall be a lump sum payment
                  equal to the cost of the applicable  premium that the Employee
                  would have to pay for the first three months of continuation
                  of coverage under such group health plan sponsored by the
                  Company upon termination of employment if the Employee elected
                  continuation of coverage under Section 4980B(f) of the Code
                  with respect to the Employee and all dependents covered under
                  the group health plan on the date the Employee terminates
                  employment. With respect to an Employee who is not
                  participating in a group health plan sponsored by the Company
                  on the date of his or her termination of employment, the
                  COBRA Contribution Benefit shall be $500.00.

         (c)      Outplacement Benefit. The Company will provide professional
                  --------------------
                  outplacement services, as defined and selected by the Company,
                  for a period of up to three (3) months following the
                  Employee's termination of employment. An Employee entitled to
                  receive this Outplacement Benefit may elect to receive a lump
                  sum payment, calculated by the Company in its sole discretion,
                  in lieu of receiving the professional outplacement services.

         The Company shall make any lump sum payments which are part of the
         Severance Benefit to a Participant as soon as administratively
         practicable following the later of the Company's receipt of an executed
         separation release and acknowledgment, as described in Section 2.3, and
         the expiration of any waiting periods described in such separation
         release.

2.3      Separation Release and Acknowledgment. The receipt of a Severance
         -------------------------------------
         Benefit described under this Section 2 is conditioned upon the
         following:

         (a)      the Participant's signing of a release deemed appropriate
                  by the Company in which the Participant releases and/or waives
                  any and all claims the Participant may have against the
                  Company;

         (b)      the release described in Section 2.3(a) becoming effective;
                  and

         (c)      any other requirements as determined solely by the Company
                  which are related to the Participant's termination of
                  employment with the Company.

         The Company has the sole and absolute discretion to determine the
         appropriateness of any release described in Section 2.3(a).

<PAGE>


                                    SECTION 3
                                 RETENTION BONUS

3.1      Eligibility. An Employee who is actively employed on September 14, 2001
         -----------
         and who either (i) continues to be employed by the Company through
         December 31, 2001 or (ii) involuntarily terminates employment, other
         than for cause as described in Section 2.1(a), with the Company prior
         to December 31, 2001, shall be eligible to receive the Retention Bonus.
         The Company shall determine whether the eligibility requirements
         described in this Section 3.1 have been met by an Employee.

3.2      Retention Bonus. An Employee entitled to receive a Retention Bonus
         ---------------
         under Section 3.1 shall receive a lump sum payment equal to twenty-five
         percent (25%) of the Employee's Annual Base Pay as soon as practicable
         following the earlier of (i) December 31, 2001, or (ii) his or her
         termination of employment.

                                    SECTION 4
                                PERFORMANCE BONUS

4.1      Eligibility.  An Employee shall be eligible to receive a Performance
         -----------
         Bonus if all of the following requirements are met:

         (a)      The Employee is actively employed on September 14, 2001;

         (b)      The Employee either (i) continues to be employed by the
                  Company through March 31, 2002 or (ii) (A) involuntarily
                  terminates employment, other than for cause as described in
                  Section 2.1(a), with the Company prior to March 31, 2002 and
                  (B) the Performance Milestones described in Section 4.1(c)
                  have all been met as of such date of termination of
                  employment.

         (c)      The following Performance Milestones are each met, as
                  determined in the sole discretion of the Board:

                  (1)      On or before September 30, 2001, the Company prepares
                           a comprehensive description of the Company's business
                           plans, including financial projections, for
                           development of cell-based therapeutic products;

                  (2)      On or before December 1, 2001, the Company completes
                           its transition duties related to the transfer of the
                           Toolbox distribution business, as described in the
                           August 2001 Agreements between the Company and
                           Baxter, and as mutually agreed between the parties;
                           and

                  (3)      On or prior to March 15, 2002, the Company presents
                           to the Board either a bona fide proposal to raise
                           five million dollars ($5,000,000) in equity
                           investment or a bona fide proposal to merge the
                           Company with another and such proposal is accepted by
                           the Board.


<PAGE>


         The Company shall determine whether the eligibility requirements
         described in this Section 4.1 have been met by an Employee.

4.2      Performance Bonus. An Employee entitled to receive a Performance Bonus
         -----------------
         under Section 4.1 shall receive a lump sum payment equal to twenty-five
         percent (25%) of the Employee's Annual Base Pay as soon as
         administratively practicable following the earlier of (i) March 31,
         2002 or (ii) his or her termination of employment.

                                    SECTION 5
                               DISCRETIONARY BONUS

5.1      Eligibility. An Employee who is designated by the Board as eligible for
         -----------
         a Discretionary Bonus shall be eligible to receive the Discretionary
         Bonus. The Board shall have the sole discretion to determine whether an
         Employee shall be designated as eligible to receive a Discretionary
         Bonus.

5.2      Discretionary Bonus. An Employee entitled to receive a Discretionary
         -------------------
         Bonus under Section 5.1 shall receive a lump sum payment equal to the
         amount designated by the Board, in its sole discretion.

                                    SECTION 6
                              PAYMENTS AND FUNDING

6.1      Disbursement of Payments. With respect to amounts paid by the Company
         ------------------------
         to a Participant in accordance with Sections 2, 3, 4 and 5, the
         appropriate withholding taxes and any other monies, debts or financial
         obligations owed to the Company by the Participant will be deducted
         from all benefit payments.

6.2      Funding. The Plan is unfunded for purposes of ERISA and the Code. All
         -------
         benefits under the Plan shall be paid from the general assets of the
         Employer.

<PAGE>


                                    SECTION 7
                            ADMINISTRATION AND CLAIMS

7.1      Plan Administrator. The Board is the administrator of the Plan and has
         ------------------
         sole and absolute power and discretion to interpret and construe the
         terms and provisions of the Plan. Except as otherwise set forth in the
         Plan, such power and discretion shall include but not be limited to the
         authority to determine eligibility for participation in the Plan and
         the receipt of benefits under the Plan. All decisions of the Board are
         final, binding and conclusive. Except as provided herein, any
         delegation of the powers and authority of the Board must be made
         pursuant to a written document. The Board may be contacted at the
         following address and phone number:

                  Nexell Therapeutics, Inc.
                  9 Parker
                  Irvine, CA 92618-1605
                  949-470-9011

7.2      Claims for Benefits. Benefits will be paid to eligible Participants
         -------------------
         pursuant to Sections 2, 3, 4, 5 and 6. Any Participant who believes
         that he or she has not received a benefit to which he or she is
         entitled may file a claim with the Chief Executive Officer of the
         Company setting forth his or her claim. Upon receipt of a claim, the
         Chief Executive Officer shall advise the Claimant that a reply will be
         forthcoming within a reasonable period of time, but ordinarily not
         later than ninety days, and shall, in fact, deliver such reply within
         such period. However, the Chief Executive Officer may extend the reply
         period for an additional ninety days for reasonable cause. If the reply
         period will be extended, the Chief Executive Officer shall advise the
         Participant in writing during the initial 90-day period indicating the
         special circumstances requiring an extension and the date by which the
         Chief Executive Officer expects to render the benefit determination. If
         the claim is denied in whole or in part, the Chief Executive Officer
         will render a written opinion using language calculated to be
         understood by the Participant setting forth:

                           (a)      the specific reason or reasons for denial;

                           (b)      the specific references to pertinent Plan
                  provisions on which the denial is based;

                           (c)      a description of any additional material or
                  information  necessary for the  Participant to perfect the
                  claim and an explanation why such material or such information
                  is necessary;

                           (d)      appropriate information as to the steps to
                  be taken if the Participant wishes to submit the claim for
                  review, including a statement of the Participant's right to
                  bring a civil action under Section 502(a) of ERISA following
                  an adverse benefit determination on review; and

<PAGE>


                           (e)      the time limits for requesting a review
                  under Section 7.3.

         If the claim is approved, the Participant's benefits will be adjusted
         accordingly.

7.3      Appeal of Denials of Benefits. A Participant who receives notice of
         -----------------------------
         denial of benefits under Section 7.2 must appeal to the Board in
         writing within sixty (60) days after the receipt of the written notice.
         Such request must be addressed to the Board at the Company's then
         current address. The Participant or his or her duly authorized
         representative may submit written comments, documents, records or other
         information relating to the denied claim, which such information shall
         be considered in the review under Section 7.4 without regard to whether
         such information was submitted or considered in the initial benefit
         determination. The Participant or his or her duly authorized
         representative shall be provided, upon request and free of charge,
         reasonable access to, and copies of, all documents, records and other
         information which (i) was relied upon by the Chief Executive Officer in
         making his or her initial claims decision, (ii) was submitted,
         considered or generated in the course of the Chief Executive Officer
         making his or her initial claims decisions, without regard to whether
         such instrument was actually relied upon by the Chief Executive Officer
         in making his or her decision or (iii) demonstrates compliance by the
         Chief Executive Officer with his or her administrative processes and
         safeguards designed to ensure and to verify that benefit claims
         determinations are made in accordance with governing Plan documents and
         that, where appropriate, the Plan provisions have been applied
         consistently with respect to similarly situated claimants. If the
         Participant does not request a review of the Chief Executive Officer's
         determination within such 60-day period, he or she shall be barred and
         estopped from challenging such determination.

7.4      Review of Appeals. Within a reasonable period of time, ordinarily not
         -----------------
         later than sixty days, after the Board's receipt of a request for a
         review, it will review all appeals to reach a final decision as to
         whether the denial of benefits was justified. If special circumstances
         require that the sixty-day time period be extended, the Board will
         notify the Participant within the initial 60-day period indicating the
         special circumstances requiring an extension and the date by which the
         Board expects to render its decision on review, which shall be as soon
         as possible but not later than 120 days after receipt of the request
         for review. The Board has discretionary authority to determine
         eligibility for benefits and to interpret the terms of the Plan.
         Benefits under the Plan will be paid only if the Board decides in its
         discretion that the Participant is entitled to them. The decision of
         the Board shall be final and non-reviewable unless found to be
         arbitrary and capricious by a court of competent review. Such decision
         will be binding upon the Company and the Participant. If the Board
         makes an adverse benefit determination on review, the Board will render
         a written opinion using language calculated to be understood by the
         Participant setting forth:

                           (a)      the specific reason or reasons for denial;

                           (b)      the specific references to pertinent Plan
                  provisions on which the denial is based;

                           (c)      a statement that the Participant is entitled
                  to receive, upon request and free of charge, reasonable access
                  to, and copies of, all documents, records and


<PAGE>


                  other information which (i) was relied upon by the Board in
                  making its decision, (ii) was submitted, considered or
                  generated in the course of the Board making its decision,
                  without regard to whether such instrument was actually relied
                  upon by the Board in making its decision or (iii) demonstrates
                  compliance by the Board with its administrative processes and
                  safeguards designed to ensure and to verify that benefit
                  claims determinations are made in accordance with governing
                  Plan documents and that, where appropriate, the Plan
                  provisions have been applied consistently with respect to
                  similarly situated claimants.

                           (d)      a statement of the Participant's right to
                  bring civil action under Section 502(a) of ERISA following an
                  adverse benefit determination on review.

7.5      Indemnification of Administrator
         --------------------------------

         The Company agrees to indemnify and to defend to the fullest extent
         permitted by law any employee of the Company serving as the Plan
         Administrator or as a member of the Board designated as Plan
         Administrator (including any employee or former employee who formerly
         served as Plan Administrator or as a member of the Board) and any
         employee action on behalf of the Company as Plan Administrator against
         all liabilities, damages, costs and expenses (including attorney's fees
         and amounts paid in settlement of any claims approved by the Company)
         occasioned by any act or omission to act in connection with the Plan if
         such act or omission is taken in good faith and is neither criminal nor
         willful misconduct.

                                    SECTION 8
                               GENERAL PROVISIONS

8.1      No Guarantee of Employment or Other Benefits. Except for Employees
         --------------------------------------------
         subject to an employment agreement which states otherwise, employment
         with the Company is on an "at will" basis. This means that the
         employment relationship may be terminated at any time by either the
         Employee or the Company for any reason not expressly prohibited by law.
         Any representation to the contrary is invalid and unenforceable and
         should not be relied upon, unless set forth in a written contract of
         employment, signed on behalf of the Company by an authorized officer.
         Participation in this Plan and the receipt of benefits under this Plan
         shall not automatically be deemed employment for purposes of any other
         employee benefit plan including, without limitation, participation in
         (i) any other benefit plan such as medical, dental, disability or other
         welfare benefit plan, (ii) any retirement or 401(k) plan or (iii) any
         other type of benefit.

8.2      Amendment or Termination. The Company reserves the right to modify or
         ------------------------
         terminate the Plan at any time. The Company through the Board or any
         committee designated by the Board may amend the Plan pursuant to a
         formal resolution. If this is done, eligible Participants will be
         notified of any important changes.

<PAGE>


8.3      Assignment of Benefits. A Participant's right to benefits under the
         ----------------------
         Plan cannot be sold or assigned and such benefits are not subject to
         garnishment or attachment until they are actually paid.

                                    SECTION 9
                                ERISA PROVISIONS

9.1      Plan Sponsor.  The Company is the sponsor of the Plan for purposes of
         ------------
         ERISA, and its name and address are as follows:

                  Nexell Therapeutics, Inc.
                  9 Parker
                  Irvine, CA 92618-1605

9.2      Agent for Service of Legal Process. The name and address of the
         ----------------------------------
         designated agent for service of legal process under the Plan is:

                  Nexell Therapeutics, Inc.
                  General Counsel
                  9 Parker
                  Irvine, CA 92618-1605

9.3      Fiscal Year of the Plan. The fiscal year of the Plan begins on January
         -----------------------
         1 and ends on December 31 of each calendar year. The first year of the
         Plan shall be a short plan year beginning on July 24, 2001 and ending
         on December 31, 2001.

9.4      Employer I.D. Number. The Company's employer identification number for
         --------------------
         federal income tax purposes is 52-2059352.

9.5      Plan Number. The three-digit number assigned to the Plan for
         -----------
         identification purposes is 501.
                                    ---

9.6      Type of Plan and Plan Administration. This Plan is a severance pay plan
         ------------------------------------
         which is a welfare benefit plan under ERISA. Benefits are
         self-administered.

9.7      Governing Laws. This Plan shall be construed, governed and administered
         --------------
         in accordance with the laws of the State of California to the extent
         such laws are not preempted by ERISA or the Code.

9.8      Statement of ERISA Rights. Participants in the Plan are entitled to
         -------------------------
         certain rights and protections under ERISA. ERISA provides that all
         Plan Participants are entitled to:

         Receive Information About Your Plan and Benefits

              Examine, without charge, at the Plan Administrator's office and at
              other specified locations, such as worksites and union halls, all
              documents governing the Plan,

<PAGE>

              including insurance contracts and collective bargaining
              agreements, and a copy of the latest annual report agreements, and
              a copy of the latest annual report (Form 5500 Series) filed by the
              Plan with the U.S. Department of Labor and available at the Public
              Disclosure Room of the Pension and Welfare Benefit Administration.

              Obtain, upon written request to the Plan Administrator, copies of
              documents governing the operation of the Plan, including insurance
              contracts and collective bargaining agreements, and copies of the
              latest annual report (Form 5500 Series) and updated summary plan
              description. The Plan Administrator may make a reasonable charge
              for the copies.

         Prudent Actions by Plan Fiduciaries

              In addition to creating rights for Plan Participants, ERISA
              imposes duties upon the people who are responsible for the
              operation of the Plan. The people who operate the Plan, called
              "fiduciaries" of the Plan, have a duty to do so prudently and in
              the interest of all Plan Participants and beneficiaries. No one,
              including the Company or any other person, may fire any
              Participant or otherwise discriminate against any Participant in
              any way to prevent him or her from obtaining benefits or
              exercising his or her rights under ERISA.

         Enforce Your Rights

              If a Participant's claim for benefits is denied or ignored, in
              whole or in part, the Participant has a right to know why this was
              done, to obtain copies of documents relating to the decision
              without charge, and to appeal any denial, all within certain time
              schedules. Under ERISA, there are steps a Participant can take to
              enforce the above rights. For instance, if a Participant requests
              a copy of Plan documents or the latest annual report from the Plan
              and does not receive them within thirty (30) days, he or she may
              file suit in a federal court. In such a case, the court may
              require the Company to provide the materials and pay the
              Participant up to $110 a day until he or she receives the
              materials, unless the materials were not sent because of reasons
              beyond the control of the Company. If a Participant has a claim
              for benefits which is denied or ignored, in whole or in part, he
              or she may file suit in a federal court. If it should happen that
              Plan fiduciaries misuse the Plan's money, or if a Participant is
              discriminated against for asserting his or her rights, he or she
              may seek assistance from the U.S. Department of Labor, or he or
              she may file suit in a federal court. The court will decide who
              should pay court costs and legal fees. If the Participant is
              successful, the court may order the person he or she has sued to
              pay these costs and fees. If the Participant loses, the court may
              order him or her to pay these costs and fees if, for example, it
              finds that the Participant's claim is frivolous.

         Assistance with Your Questions

              Any Participant who has questions about the Plan should contact
              the Company. Any Participant who has any questions about this
              statement or about his or her rights under ERISA, or needs
              assistance in obtaining documents from the Plan Administrator,
              should

<PAGE>


              contact the nearest Area Office of the Pension and Welfare
              Benefits Administration, U.S. Department of Labor, listed in the
              telephone directory or the Division of Technical Assistance and
              Inquiries, Pension and Welfare Benefits Administration, U.S.
              Department of Labor, 200 Constitution Avenue N.W., Washington,
              D.C. 20210. A Participant may also obtain certain publications
              about his or her rights and responsibilities under ERISA by
              calling the publications hotline of the Pension Welfare Benefits
              Administrator.

         IN WITNESS WHEREOF, Nexell Therapeutics, Inc. has caused this Plan to
be executed by a duly authorized officer as of this the 30th day of January,
2002.

                                        NEXELL THERAPEUTICS, INC.

                                        By:_____________________________________
                                           President and CEO


<PAGE>


                   AMENDMENT TO THE NEXELL THERAPEUTICS, INC.
              RETENTION AND SEVERANCE PLAN FOR SENIOR STAFF MEMBERS
                                       AND
                            SUMMARY PLAN DESCRIPTION

       WHEREAS, Nexell Therapeutics, Inc. ("Company") previously established the
Nexell Therapeutics, Inc. Retention and Severance Plan for Senior Staff Members
("Plan"); and

       WHEREAS, the Company reserved the right to amend the Plan; and

       WHEREAS, the Company desires to amend the Plan to extend certain dates
related to the performance bonus;

       NOW, THEREFORE, the Plan is amended as follows:


       1. The first sentence of Section 2.1 is deleted and replaced with the
          following:

              "An Employee whose employment with the Company is voluntarily
              terminated on or after July 24, 2001 but no later than June 30,
              2002, other than for cause as defined below, shall be eligible to
              receive a Severance Benefit."


       2. Section 4.1(b) is deleted and replaced with the following:

              (b)    The Employee either (i) continues to be employed by the
                     Company through June 30, 2002 or (ii) (A) involuntarily
                     terminates employment, other than for cause as described in
                     Section 2.1(a), with the Company prior to June 30, 2002 and
                     (B) the Performance Milestones described in Section 4.1(c)
                     have all been met as of such date of termination of
                     employment.


       3. Section 4.1(c)(3) is deleted and replaced with the following:

              (3)    On or prior to June 30, 2002, the Company presents to the
                     Board either a bona fide proposal to raise five million
                     dollars ($5,000,000) in equity investment or a bona fide
                     proposal to merge the Company with another company and such
                     proposal is accepted by the Board.


       4. Section 4.2 is deleted and replaced with the following:

              4.2    Performance Bonus. An Employee entitled to receive a
                     -----------------
                     Performance Bonus under Section 4.1 shall receive a lump
                     sum payment equal to twenty-five percent (25%) of the
                     Employee's Annual Base Pay as soon as administratively
                     practicable following the earlier of (i) June 30, 2002 or
                     (ii) his or her termination of employment.

<PAGE>

       IN WITNESS WHEREOF, the Company has caused this amendment to be executed
this                      day of                 , 2002.
     --------------------        ----------------

                                             NEXELL THERAPEUTICS, INC.


                                             By
                                               ---------------------------------

                                        2