Document:

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                                 Exhibit 10.64

                            DISTRIBUTION AGREEMENT

  THIS DISTRIBUTION AGREEMENT is made as of this 28/th/ day of April, 2000
("Execution Date") by and between NEXELL THERAPEUTICS INC., a Delaware
corporation (the "Company") and TAKARA SHUZO CO., LTD. a Japanese corporation
("Distributor").

                                    RECITALS
                                    --------

  A.  Company owns or will own the rights to, and sells or will sell, the
Products.

  B.  Distributor desires to resell the Products in the Territory.

                              TERMS AND CONDITIONS
                              --------------------

  NOW, THEREFORE, in consideration of the mutual covenants and agreements
hereinafter set forth, the parties hereto hereby agree as follows:

      1.  Definitions.  For purposes of this Agreement, the following terms
          -----------
shall have the meanings as hereinafter set forth:

               (a)  Documentation.  The term "Documentation" shall mean the
                    -------------
then current written information provided by the Company for use by end-users
relating their use of the Products. Director's compensation, if any, will come
from the margin between the price it pays the Company for Products and the price
at which it sells those products. Distributor has no right to any compensation
from the Company.

               (b)  Marketing Strategy.  The execution plan that describes
                    ------------------
Distributor's capabilities to perform under the terms of the Agreement developed
by Distributor and approved by Company, as attached hereto as Exhibit A.

               (c)  Products.  The term "Products" shall mean the products
                    --------
owned and offered for sale by Company during the term of this Agreement,
including but not limited to those set forth on Exhibit B hereto.

               (d)  Territory.  The term "Territory" shall mean and include
                    ---------
Japan, Korea, Taiwan and China.

               (e)  Trademark.  The term "Trademark" shall mean and include the
                    ---------
trademarks listed on Exhibit C to the extent effective in any country in the
Territory.

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    2.  Grant of Rights.  During the term of this Agreement and subject to the
        ---------------
terms and conditions set forth herein,

          (a) Company hereby grants to Distributor the right to sell and
distribute the Products through any and all commercially proper means consistent
with the Marketing Strategy in the Territory.

          (b) Company hereby grants to Distributor the right to use the
Trademarks in connection with the marketing and sale of the Products in the
Territory.

          (c) Distributor shall not have the right to have the Products
manufactured for it by a third party.

          (d) At the request of Distributor, Company will modify the Company's
CELLEXTRA(TM) automated closed system platform for gene therapy, if and when
available, to the reasonable extent necessary for the incorporation of
Distributor's gene therapy products into the CELLEXTRA(TM) platform. Distributor
shall be responsible, and reimburse Company, for all costs and expenses incurred
by Company in connection with any such modification.

          (e) Company and Distributor are separate independent entities, and
Distributor has no authority to assume or create any obligations on behalf of
the Company without the prior written consent of the Company.

    3.  Translations for Local Market.  Subject to the Company's prior written
        -----------------------------
approval, Distributor shall make such language translations of the Documentation
and the labels provided by the Company with the Products as are appropriate or
necessary for the sale of Products in the Territory.  Distributor hereby assigns
any such translations to the Company and shall execute any documents to evidence
or perfect such assignment to the Company.  Distributor hereby appoints Company
as its attorney-in-fact to execute all documents necessary or appropriate to
effect the assignment described in this Section.

    4.  Term.  Unless earlier terminated as provided herein, the term of this
        ----
Agreement shall commence upon the Execution Date and shall continue in effect
until the date which is five (5) years from the Effective Date.  At the end of
such term, the parties may renew this Agreement upon such terms and conditions
as may be mutually agreed upon.

      Notwithstanding the foregoing, the parties shall have no rights or
obligations under Sections 2, 8 or 9 hereof until the 100th day following the
Execution Date, or such earlier time as the Company informs Distributor, upon 10
days prior written notice, that the parties have such rights and obligations as
of the time specified in the notice (the "Effective Date").

    5.  Orders.  Each order of Distributor shall be by written purchase order or
        ------
other means acceptable to the Company, provided, however, the terms and
conditions of this Agreement shall prevail over any such written order.  All
orders shall be subject to acceptance or rejection by the Company.

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    6.  Pricing and Payments.
        --------------------

      (a) The price of the Products sold to Distributor shall be equal to
Company's transfer price for the Products, which may change from time to time at
the Company's sole discretion, the current form of which is attached hereto as
Exhibit B.

      (b) Distributor shall pay to Company amounts owed on orders for Products
upon receipt of an invoice for such amounts in accordance with the terms of such
invoice.  Title to the goods shall remain with the Company until full payment
has been received.

      (c) Distributor shall pay to the Company $2,500,000 in cash on the
Effective Date in exchange for the rights granted to Distributor hereunder.
Distributor shall be entitled to deduct from such payment up to 10% as
withholding tax.

    7.   Shipment.  All Products shall be sold to Distributor ex works and
         --------
delivered directly to Distributor.  Delivery and shipments of orders may be in a
single delivery or in lots, in the Company's sole discretion.

          (a) Title, risk of loss and damage to all Products sold by the Company
to Distributor shall pass to Distributor upon delivery.

          (b) Notwithstanding the passage of title and risk of loss upon
shipment, the Company shall retain a security interest in the Products ordered
and purchased by Distributor hereunder until full payment shall have been made
by Distributor.  Distributor acknowledges that this paragraph constitutes a
security agreement, and shall execute any financing statement or other documents
requested by Company which may be necessary or appropriate to perfect the
Company's security interest in the Products hereunder.

    8.   Duties of Distributor Relating to Distribution.  Distributor shall:
         ----------------------------------------------

          (a) Purchase from the appropriate affiliate of Baxter Healthcare
Corporation in the Territory all Products in Baxter's merchantable inventory,
which inventory should be inspected and confirmed by Distributor, as of the
Effective Date;

          (b) Use its best efforts to diligently and actively promote the
marketing and sales of the Products in accordance with the Marketing Strategy,
good business ethics and practices and in accordance with the terms and
conditions of this Agreement;

          (c) Make purchases of Products of at least $75,000, excluding returns,
freights, postage, duties and taxes, for each twelve-month period during the
term of this Agreement, commencing on the Effective Date ("Product Purchase
Target").  Distributor agrees that in the event it fails to meet the Product
Purchase Target, Distributor will pay Company an amount in cash equal to $75,000
less the purchases of Products actually made.  If this Agreement expires or
terminates on a date that does not complete a twelve-month period described
herein, the Product Purchase Target for such abbreviated period shall be reduced
pro rata from $75,000 in accordance with the relationship the abbreviated period
bears to a twelve-month period.

          (d) Dedicate to the distribution of Products a sales force of a size
and with expertise acceptable to Company, as described in the Market Strategy;

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          (e) Order and sell the following amounts of Products during the
following periods (each, a "Product Sales Target"):

              (i)  $1,500,000 of Products during the two full years commencing
on the Effective Date; and

              (ii) $1,725,000 of Products during each of the three full years
commencing on the second anniversary of the Effective Date;

          (f) Pay all of its own expenses and shall be responsible for all acts
of its employees, sales representatives and distributors;

          (g) Obtain and retain on behalf of Nexell any licenses or other
approvals required by the laws of the Territory to commercialize the Products in
connection with the transactions contemplated by this Agreement, including, but
not limited to, clinical trials required by product registration, product
registrations, reimbursement, adverse event reporting and other postmarking
surveillance, and making all certifications and keeping all the records required
to obtain or retain such licenses or approvals, subject to the specific
requirements of Section 16 hereof;

          (h) Maintain an inventory of the Products sufficient to adequately
serve the needs of its customers on a reasonably timely basis and, at a minimum,
such inventory shall include not less than the quantity of the Products
necessary to meet reasonably anticipated demands of its customers for a thirty
(30) day period;

          (i) Ensure that all Products are in compliance with any minimum shelf
life requirement mandated by local law and provide notice to the Company of any
minimum shelf life mandated by local law;

          (j) Maintain a dialog with the Company regarding customer
satisfaction, submit to Company Technical Support details of customer
complaints, and follow up and gather data to investigate and resolve customer
complaints;

          (k) Maintain a dialog with the Company regarding market problems and
opportunities and competitive information, and provide the Company with
information on any new regulatory requirements likely to impact sales of the
Products;

          (l) Provide product information supplied or approved by the Company,
along with advice and support, including technical support and after sales
service, to end users of the Products;

          (m) Establish specific operating procedures for inventory and
shipping of the Products, and contract document and change control procedures
for implementing and maintaining changes to procedures applicable to the
Products, as are acceptable to the Company;

          (n) Ship Products at all times in accordance with the Company's
validated shipping procedures or such alternate validated procedures as the
Company has approved in advance;

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          (o) Maintain lot-specific records of Product shipments by customer to
be available in the event of a market withdrawal, Product recall or other
required field action, and provide support and assistance in the event of a
market withdrawal, Product recall or other required field action;

          (p) Provide access to the Distributor's facilities and records
relating to Distributor's performance and compliance with its obligations under
this Agreement, on two week's notice for the Company and its representatives to
conduct a quality and compliance audit at least once during each twelve (12)
month period;

          (q) Conduct business in a manner that reflects favorably at all times
on the Products and the good name, goodwill and reputation of Company; avoid
deceptive, misleading or unethical practices that are, or might be, detrimental
to Company, the Products, dealers or the public, including, but not limited to,
disparagement of Company or the Products; make no false or misleading
representations with regard to Company or the Products; not publish or employ or
cooperate in the publication or employment of any misleading or deceptive
advertising material; make no representations, warranties or guarantees to
customers or to the trade with respect to the specifications, features or
capabilities of the Products that are inconsistent with the literature
distributed by Company, including all warranties and disclaimers contained in
such literature; and not sell the Products to any dealer or organization that
engages in illegal or deceptive trade practices;

          (r) Sell the Products with all packaging, warranties and disclaimers
intact as shipped from Company or as adapted pursuant to the terms of this
Agreement; and

          (s) Use reasonable efforts to protect Company's proprietary rights and
to cooperate without charge in Company's efforts to protect its proprietary
rights.

    9.  Duties of Distributor Relating to Service. Distributor further agrees to
provide service for Products in the Territory as required, without additional
compensation from the Company, on the following terms:

          (a) The service to be provided by the Distributor ("Service") shall
include in-warranty and out-of-warranty repair work requested by a customer in
the Territory with respect to one or more of the Products, such installation
work as may be required by the complex nature of the Products, preventive
maintenance work on the Products; provided that Service shall not include any
work for which the Company has not provided training pursuant to paragraph (e)
below, any work more detailed than repairing or replacing Products hardware
only, or any software or hospital network systems responsibilities other than
simple reloading of software on components of the Products and such other
responsibilities as may be agreed to in writing from time to time between the
Distributor and the Company.

          (b) The maximum response time shall be within seven working days for a
down machine.  The Company and the Distributor will cooperate in planning the
scope and timing of Service provided hereunder in order to minimize of eliminate
interference with the conduct of the Distributor's other business activities.
If such interference is unavoidable, the Distributor will apportion its
activities to the Service in a fair and reasonable manner.

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          (c) All Service will be provided at the site of the Product.

          (d) The Distributor's technical specialists will be the primary
interface with all customers purchasing the Products in the Territory for any
instrument issue.  The Distributor will provide monthly service reports to the
Company comparable to other service reports generated for the Distributor's
products.

          (e) For all mutually agreed upon types of Service for the Products,
the Distributor will obtain from the Company, and the Company will provide, at
no charge to Distributor, specialized training to technical instructors
designated by the Distributor on how to repair, refurbish, conduct preventive
maintenance and perform other Service on all Products; on all other matters and
skills needed or appropriate for the Distributor to fulfill its obligations
hereunder; and on how to train others in such matters and skills.  The
Distributor will assume full responsibility for ensuring that the Distributor's
field service engineers are trained and kept up to date on any changes to the
Products either by conducting training sessions or by sending out service
bulletins.  The training provided by the Company shall be at the Company's
California facility or other mutually agreeable location.  The Company will
provide at no charge to the Distributor all mutually agreed Products and parts
in sufficient quantities as required or appropriate with respect to training by
the Company pursuant to this paragraph (e).  All equipment and training aids
furnished by the Company for training will remain the property of the Company
and will be returned to the Company upon termination of this Agreement,
regardless of other claims or disputes, shipping charges billable to the
Company, ordinary wear and tear and damage by fire or casualty excepted.  The
Company agrees that the Distributor may freely reproduce any such papers,
procedures, recommended parts lists, complete parts lists, books, manuals,
workbooks, videos and all training, instruction and presentation aids, unless
such items as are designated by the Company as confidential, which shall be
reproduced  for the Distributor's internal use only.  The Distributor shall be
responsible for the cost of any Products, parts, equipment, training aids and
other items provided by the Company hereunder that are lost or destroyed while
in the possession or control of the Distributor or one of its employees.  In
such instances the training will be provided free, but the accommodation and
travel costs of attending such a meeting shall be born by the Distributor.

          (f) The Company will provide, at no charge, to the Distributor for
each technician providing Service hereunder, a complete service manual for each
Product including operations procedures, theory of operation, installation
procedures, schematic diagrams, adjustment and calibration procedures, trouble
shooting guides, parts diagrams and complete part lists.  The Company will
periodically update each service manual to incorporate service bulletins and
other updated information.  A review loop will be defined that will outline the
review responsibilities related to these documents for both the Distributor and
the Company.

          (g) The Company will provide, at no charge, to the Distributor for
each representative providing Service hereunder, any test equipment and tools
which are not necessary in providing test or repair work on other instruments
which the Distributor tests or repairs, but are necessary for the proper test,
repair or preventive maintenance of a Product.  The Company shall not be
required hereunder to replace or repair without cost any such test equipment or
tools which are lost, stolen or damaged while in the Distributor's possession or
under its control.

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          (h) The terms of Product warranties shall be as specified by the
Company, provided, however, that the Distributor's responsibilities to the
Company with respect to Product warranties on Products manufactured or supplied
by the Distributor shall not be altered or amended by any Product warranties so
furnished by the Company to such customers.  The Distributor will provide a
complete warranty on the Distributor's standard terms and conditions for spare
parts for at least one year from the date of installation of the service part
into a Product for a customer.  The Company will supply to Distributor at no
charge all such repair parts required by the Distributor in connection with its
warranty obligations during such one-year warranty periods.

          (i) The Distributor will be responsible for negotiating and setting
the terms of service contracts with customers purchasing the Products, within
the limits of guidelines set or approved by the Company.

          (j) The Distributor and the Company shall work together to generate
all service bulletins, service notes and service aids for each Product.  The
Distributor's service group will distribute service bulletins, service notes and
service aids for each Product through its normal distribution process.

          (k) Distributor agrees that all spare parts will be packaged and
labeled to comply with all laws and regulations in the Territory including,
without limitation, laws and regulations concerning hazardous materials.

          (l) The parties agree that changes, upgrade, retrofits, exchanges,
recalls and similar events with respect to any Product in the Territory are part
of the scope of this Agreement.  The Company agrees to advise the Distributor of
each such matter and provide the Distributor full particulars and information
with such advice.  The Company agrees to provide the Distributor, at no charge,
reasonable quantities of each Product and all changes or modifications thereto,
as necessary.

          (m) The Distributor agrees that it will, at the Company's request and
expense, return to the Company such parts and components for any Product which
the Distributor acquires from customers in the course of providing Service
hereunder; provided, however, that no such return shall be required of any item
which is potentially hazardous.

    10. Exclusivity.  During the term of this Agreement, Company agrees that it
        -----------
will not enter into a contract with any third party for the sale or distribution
of the Products in the Territory.  During the term of this Agreement,
Distributor agrees that it will not enter into a contract with any third party
for the sale or distribution of products that compete with the Products in the
Territory.

    11. Sublicense Rights. Distributor may sublicense its rights under this
        -----------------
Agreement to third parties only with the prior written approval of the Company,
which approval shall not be unreasonably withheld.

    12. Termination of Agreement.
        ------------------------

         (a)  Notice of Termination.  Distributor may terminate this Agreement
              ---------------------
for any reason upon 90 days prior written notice to the Company.

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          (b) Termination For Cause.  Company, in its sole discretion, may
              ---------------------
terminate this Agreement at any time prior to the expiration of its stated term
in the event that:

                 i)   Distributor fails to meet the Product Purchase Target; or

                ii)   Distributor defaults in any payment due to Company and
     such default continues unremedied for a period of ten (10) days after
     written notice by Company to Distributor identifying the nature of the
     default; or

                iii)  Distributor fails to perform any other obligation,
     warranty, duty or responsibility or is in default with respect to any term
     or condition undertaken by Distributor under this Agreement or under the
     Co-Development Agreement between Company and Distributor of even date
     herewith, other than the payment of money, and such failure or default
     continues unremedied for a period of fifteen (15) days after written notice
     by Company to Distributor identifying the nature of the default; or

                iv)   Distributor is merged, consolidated, sells all or
     substantially all of its assets, or implements or suffers any substantial
     change in control.

                In the event Distributor fails to meet any Product Sales Target
     specified in Section 8(e)(i) or (ii), the Company shall have the right to
     change the distribution right granted to Distributor under this Agreement
     to a non-exclusive right.

          (c) Automatic Termination.  This Agreement terminates automatically,
              ---------------------
with no further act of action of either party, if a receiver is appointed for
Distributor or its property, Distributor makes an assignment for the benefit of
its creditors, any proceedings are commenced by, for or against Distributor
under any bankruptcy, insolvency or debtor's relief law or Distributor is
liquidated or dissolved.

          (d) Effect of Termination.  Upon termination of this Agreement and for
              ---------------------
a period of one (1) year after the date of termination, Distributor shall make
available, upon reasonable prior notice, to Company for inspection and copying
all books and records of Distributor that pertain to Distributor's performance
of and compliance with its obligations, warranties and representations under
this Agreement.  Unless the parties otherwise agree in writing, upon termination
of this Agreement, Distributor shall (i) deliver to the Company or any new
distributor designated by the Company within 30 days all inventory, other assets
of the Company and copies of the records in Distributor's possession related to
the Products, for which Company shall pay to Distributor the purchase price
Distributor originally paid pursuant to Section 6(a) for the Products included
in such inventory, and (ii) take all steps necessary, in accordance with the
Company's instructions and in a timely manner, to transfer all regulatory
permits, licenses and approvals for the Products to the Company or its designee
effective with the date of termination.

          (e) No Compensation For Termination. Distributor acknowledges that
              -------------------------------
prices for the Products have been established at a level to compensate
Distributor for the costs of making the translations and to develop and exploit
the market with respect to the Products.  Upon the expiration or other
termination of this Agreement, Distributor shall not be entitled to any
termination compensation, consequential damages, indemnity or other payment for
goodwill, lost profits, costs of re-establishment or replacement of the business
or any other expenses or rights relating to the Products or to termination of
this Agreement or the expectations of one or both of

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the parties that this Agreement (or the relationships created hereby) may be
renewed and/or extended. Distributor expressly acknowledges any rights to any
compensation for the termination of this Agreement afforded by law or custom,
and to the extent permissible under applicable law, is hereby expressly and
completely waived. Distributor acknowledges and agrees that (i) Distributor has
no expectation, and has received no assurances, that its business relationship
with Company will continue beyond the stated term of this Agreement or its
earlier termination in accordance with this Agreement, that any investment by
Distributor in the promotion of the Products will be recovered or recouped, or
that Distributor shall obtain any anticipated amount of profits by virtue of
this Agreement; and (ii) Distributor shall not have or acquire by virtue of this
Agreement or otherwise any vested, proprietary or other right in the promotion
of the Products or in any goodwill created by its efforts hereunder.

          THE PARTIES ACKNOWLEDGE THAT THIS SECTION HAS BEEN INCLUDED AS A
MATERIAL INDUCEMENT FOR COMPANY TO ENTER INTO THIS AGREEMENT AND THAT COMPANY
WOULD NOT HAVE ENTERED INTO THIS AGREEMENT BUT FOR THE LIMITATIONS OF LIABILITY
AS SET FORTH HEREIN.

    13. Trademarks and Intellectual Property Rights.
        -------------------------------------------

          (a) Distributor acknowledges that the Company owns the Trademarks, and
Distributor agrees that it shall not at any time during or after this Agreement
assert or claim any interest in or do anything that may adversely affect the
validity or enforceability of any Trademark.  Distributor agrees not to attach
any additional trademarks, logos or trade designations to the Products except as
may be expressly approved by the Company. Notwithstanding the foregoing,
Distributor shall be entitled to indicate in all written material pertaining to
the Products that the same are distributed by Distributor.

          (b) Upon expiration or termination of this Agreement, Distributor
shall forthwith cease all display, advertising and use of the Trademarks and
shall not thereafter use, advertise or display any name, mark or logo which is,
or any part of which is, similar to or confusing with any such designation
theretofore associated with the Products.

          (c) Distributor agrees to inform the Company in writing immediately
upon becoming aware of any infringement or threatened infringement of any
Trademark, patent, name or logo owned or used by the Company.

          (d) Company shall use all reasonable efforts, at its cost, to bring
any infringement or threatened infringement referred to in paragraph (c) above
to an end, whether by commencing and prosecuting legal proceedings or otherwise,
and shall have the sole right to control any demand or action in respect of any
such infringement or threatened infringement.  Distributor agrees to cooperate
with Company by doing all acts and things that the Company may reasonably
require in respect of any infringement or threatened infringement.

    14. Warranties.  Subject to the conditions hereinafter stated, the Company
        ----------
warrants that the Products meet, in all material respects, the specifications of
the Products as the same may be changed by the Company from time to time.

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          (a) This warranty extends only to Distributor and Distributor's remedy
for a breach of this warranty is limited, at the discretion of the Company, to
the refund of the purchase price for, or the repair or replacement of, any non-
conforming Products.

          (b) The Company shall, at its option and expense, refund the purchase
price for, or repair or replace, a defective Product, provided that Distributor
(i) notifies the Company of any such defect within thirty (30) days from the
date of actual receipt of the Products by Distributor and (ii) promptly returns
such defective Product to the Company.

    THE EXPRESS WARRANTIES SET FORTH HEREIN ARE IN LIEU OF ALL OTHER WARRANTIES,
WHETHER EXPRESS OR IMPLIED, INCLUDING (WITHOUT LIMITATION) ALL IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR USE.

    The refund or repair or replacement, in the manner and for the period of
time provided above, shall constitute the Company's sole liability and
Distributor's exclusive remedy for failure of the Company to meet its warranty
obligations, whether claims of Distributor are based in contract, in tort or
otherwise.

   15.  Indemnity.
        ---------

    (a) The Company shall indemnify and hold Distributor harmless from any and
all damages, losses, expenses or costs (including reasonable attorneys' fees and
expenses) or death or injury to a person arising from a breach by Company of its
warranties under Section 14, unless due to the negligence or other fault of the
Distributor, its affiliates or their representatives.

    (b) The Distributor shall indemnify and hold the Company harmless from any
and all damages, losses, expenses or costs (including reasonable attorneys' fees
and expenses) arising from the negligence or other fault of the Distributor, its
affiliates or their representatives in the performance of their duties under
this Agreement.

    (c) The Company shall indemnify and hold Distributor harmless from any and
all damages, losses, expenses or costs (including reasonable attorneys' fees and
expenses) arising from any claim by a third party of infringement of such third
party's intellectual property by a Product.

    (d) The foregoing indemnities are continuing obligations of the parties
separate and independent of their other obligations under this Agreement and
will survive termination of this Agreement.

   16.  Taxes and Duties.  Distributor shall have the sole responsibility to pay
        ----------------
all import duties and fees, taxes and other charges levied by Government
authorities in the Territory upon or in connection with any transaction covered
by this Agreement, including without limitation taxes on sales, use,
transactions or inventory, and value-added taxes.

   17.  Permits and Licenses.  Distributor shall have sole responsibility to
        --------------------
obtain all permits, licenses and approvals from Government authorities necessary
to import and sell the Products in the Territory or to return any of the
Products to the Company.  Company shall be the owner of all such permits,
licenses and approvals, and Distributor shall be Company's authorized
representative for such purpose.  In the event applicable law does not permit
Company to be named as the owner of

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any such permit, license or approval, Distributor may be named as the owner for
the benefit of the Company; provided that, upon termination of this Agreement,
Distributor will take all necessary steps to transfer ownership to the Company
or its designee in accordance with the Company's instructions and in a timely
manner.

    Distributor shall also have the sole responsibility to comply with any
requirement to file this Agreement with any Government authority in the
Territory or to obtain the approval of any Government authority in the Territory
for this Agreement.  If any Government authority in the Territory invalidates
any portion of this Agreement, the Company shall have the option to terminate
this Agreement immediately by written notice to Distributor.

  18.   Compliance with Laws.  Distributor acknowledges that, as a company
        --------------------
engaged in the marketing and distribution of U.S. origin goods and services,
certain U.S. laws and regulations apply to some of its activities on behalf of
the Company.

    (a) The Distributor agrees to inform itself concerning the requirements of
such U.S. laws and regulations, including the Export Administration Act (as and
when in force), Export Administration Regulations (including the Antiboycott
Regulations), Securities Exchange Act and other securities laws, Foreign Corrupt
Practices Act and sanctions regulations administered by the U.S. Treasury's
Office of Foreign Assets Control, to ensure its continuing compliance with such
U.S. laws and regulations as they may apply to the Company and Distributor.

    (b) In particular, without limiting the foregoing, the Distributor
acknowledges that U.S. law at the date of execution of this Agreement continues
to prohibit the re-export to North Korea of virtually all U.S. origin goods
unless a license has been issued by the U.S. government authorizing such re-
export.  The Distributor agrees to obtain such U.S. Government licenses as may
be required for the sale or distribution of the Products, and the Distributor
agrees not to offer or give anything of value to any foreign government official
in violation of any applicable law for the purpose of obtaining or retaining
business.

    (c) Distributor likewise agrees to inform itself concerning and to comply
with the applicable laws and regulations of the countries where it distributes
the Products.  Distributor shall advise the Company of any change in any law or
regulation applicable in the Territory which may be relevant to the Products.

      19. Force Majeure.  The Company shall use all commercially reasonable
          -------------
efforts to fill orders promptly and to meet requested dates of shipment.  The
Company shall not be liable for delays or failure in delivery or manufacture due
to causes beyond its reasonable control, such as acts of God, acts of
Distributor, acts of civil or military authorities, fires, strikes, floods,
wars, riots and other causes of a similar nature.

      20. Disputes and Arbitration.  The parties hereto are convinced that a
          ------------------------
large part of contract litigation is caused by a failure to reduce the essential
terms and conditions to writing and that much of the remainder is caused by
weaknesses or various kinds in written contracts. Thus, they have endeavored to
use every care and caution in the preparation of this Agreement. Nevertheless, a
relationship of this character may pose new problems from time to time requiring
subsequent resolution. Therefore, it is the aim and intention of the parties, in
their mutual interests, to provide a practical and dignified means for friendly
adjustment of any differences in the

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interpretation of this Agreement or the settlement of any disputes that may
arise hereunder between the parties.

          (a) Each party agrees to bring all such matters to the attention of
the other prior to instituting any arbitration as provided herein.  This shall
be done without prejudicing their harmonious relationship and operations
hereunder, and the offices of either party and their facilities shall be
available at all times for the prompt and effective adjustment of all such
differences under friendly and courteous circumstances.

          (b) If the dispute cannot be resolved within twenty (20) days after
being brought to a party's attention as described in paragraph (a) above, the
parties shall refer the dispute to the respective officers designated below (or
their successors) for attempted resolution by good faith negotiations within
forty (40) days of the notice described in paragraph (a) above:

              For Nexell:  ______________________________

              For Takara:  ______________________________

          (c) In the event the officers are unable to resolve such disputes on
behalf of the parties within forty (40) days of the notice described in
paragraph (a) above, the parties hereby agree to submit any and all disputes
arising hereunder to binding arbitration under the commercial rules of the
American Arbitration Association in Los Angeles, California.

    21. Notices.  All written notices or other written communications required
        -------
under this Agreement shall be deemed properly given when provided to the parties
entitled thereto by personal delivery (including delivery by commercial services
such as messengers and air freight forwarders), by electronic means (such as by
electronic mail, telex or facsimile transmission) or by mail sent registered or
certified mail, postage prepaid at the following addresses (or to such other
address of a party designated in writing by such party to the others):

     Company:     Nexell Therapeutics Inc.
                  9 Parker
                  Irvine, California 92818
                  Attn: William Wong
                  Fax No. (949) 470-6645

     Distributor: Takara Shuzo Co. Ltd.
                  Seta 3-4-1, Otsu,
                  Shiga 520-2193
                  Attn: Ikunoshin Kato
                  Fax No. 077-543-9254

All notices given by electronic means shall be confirmed by delivering to the
party entitled thereto a copy of said notice by certified or registered mail,
postage prepaid, return receipt requested.  All written notices shall be deemed
delivered and properly received upon the earlier of five (5) days after mailing
the confirmation notice or upon actual receipt of the notice provided by
personal delivery or electronic means.

                                       12
<PAGE>

    22. Subject Headings.  The subject headings of the paragraphs of this
        ----------------
Agreement are included solely for purposes of convenience and reference only,
and shall not be deemed to explain, modify, limit, amplify or aid in the
meaning, construction or interpretation of any of the provisions of this
Agreement.

    23. Exhibits.  All exhibits, attached hereto and referred to herein, are an
        --------
integral part of this Agreement and are incorporated herein by reference hereby.

    24. Amendments.  Unless expressly permitted herein, no supplement,
        ----------
modification or amendment of any term, provision or condition of this Agreement
(including this Paragraph) shall be binding or enforceable unless evidenced in a
writing executed by the parties hereto.

    25. Entire Agreement and Waiver.  This Agreement contains the entire
        ---------------------------
agreement between the parties hereto and supersedes all prior and
contemporaneous agreements, arrangements, negotiations and understandings
between the parties hereto, relating to the subject matter hereof.  There are no
other agreements, understandings, statements, promises or inducements, oral or
otherwise, contrary to the terms of this Agreement.  No representations,
warranties, covenants or conditions, express or implied, whether by statute or
otherwise, other than as set forth herein, have been made by any party hereto.
No waiver of any term, provision, or condition of this Agreement, whether by
conduct or otherwise, in any one or more instances, shall be deemed to be, or
shall constitute, a waiver of any other provision hereof, whether or not
similar, nor shall such waiver constitute a continuing waiver, and no waiver
shall be binding unless executed in writing by the party making the waiver.

    26. No Assignment.  Neither this Agreement nor any of the rights or
        -------------
obligations hereunder shall be assignable by any party hereto without the
written consent of the other party first obtained (which consent shall not be
unreasonably withheld).  Notwithstanding the foregoing, either party, without
the consent of the other, may assign this Agreement to an affiliate of such
party.  However, if any assignee affiliate ceases to be an affiliate of the
assignor party, that event shall be deemed to be an assignment requiring the
consent of the other party.  Subject to the foregoing, this Agreement shall be
binding upon and shall inure to the benefit of the parties hereto and their
respective representatives, successors and permitted assigns.

    27. Counterparts.  This Agreement may be executed in one or more
        ------------
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

    28. Governing Law And Disputes.  This Agreement and the performance thereof
        --------------------------
shall be construed, interpreted, applied and governed in all respects in
accordance with the internal laws of the State of California (without regard to
the application of its conflicts of laws) and the 2000 ICC INCOTERMS.  The
parties expressly reject any application of the United Nations Convention on
Contracts for the International Sale of Goods.  Each party hereby submits to the
exclusive jurisdiction of the Superior Court of the State of California for the
County of Orange and the U.S. District Court for the Central District of
California.

    29. Confidentiality.  The parties hereto agree that the terms and conditions
        ---------------
of this Agreement are confidential and shall not be disclosed by any party
hereto, except as may be required by law, without the prior written consent of
the other party first obtained.

                                       13
<PAGE>

    30. Reformation/Severability.  If any provision of this Agreement is
        ------------------------
declared invalid by any tribunal, then such provision shall be deemed
automatically adjusted to the minimum extent necessary to conform to the
requirements for validity as declared at such time and, as so adjusted, shall be
deemed a provision of this Agreement as though originally included herein.  In
the event that the provision invalidated is of such a nature that it cannot be
so adjusted, the provision shall be deemed deleted from this Agreement as though
such provision had never been included herein.  In either case, the remaining
provisions of this Agreement shall remain in effect.

    31. Limitation of Liability.  IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR
        -----------------------
INCIDENTAL, CONSEQUENTIAL, SPECIAL OR INDIRECT DAMAGES ARISING OUT OF OR RELATED
TO THIS AGREEMENT, INCLUDING WITHOUT LIMITATION, LOST BUSINESS, PROFITS OR
DAMAGES ARISING FROM OR CONNECTED WITH LOST, DAMAGED OR ALTERED DATA OR LOSS OF
GOODWILL.

    32. Publicity.  All notices to third parties and all other publicity
        ---------
concerning the transactions contemplated hereby shall be jointly planned and
coordinated by the parties hereto and no party shall act unilaterally in this
regard with the prior written approval of the other.

    33. Language/Currency.  The governing language to be used for purposes of
        -----------------
the interpretation and meaning of this Agreement shall be English and all
references to dollars ($) shall be to U.S. Dollars.

    IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed and delivered by persons duly authorized as of the date first set forth
above.

Company:  NEXELL THERAPEUTICS INC.

/s/ L. William McIntosh
-----------------------
By:
Name: L. William McIntosh
Title: President and Chief Operating Officer

Distributor:  TAKARA SHUZO CO., LTD.

/s/ Ikumoshin Kato
------------------
By:
Name: Ikumoshin Kato, Ph.D.
Title: President, Biomedical Group

                                       14<PAGE>

                                 Exhibit 10.65

                           CO-DEVELOPMENT AGREEMENT

  This CO-DEVELOPMENT AGREEMENT is entered into as of April 28, 2000 (the
"Effective Date") by and between NEXELL THERAPEUTICS INC. ("Nexell"), a Delaware
corporation, and TAKARA SHUZO CO., LTD. ("Takara"), a Japanese corporation.

                                   RECITALS
                                   --------

  A.  Nexell has developed a certain cell culture container and other technology
for use in the field of ex vivo cell therapy.

  B.  Takara has developed a product, known as RetroNectin, for use in the field
of retrovirus mediated gene transfer.

  C.  Nexell and Takara desire to engage in co-development efforts in accordance
with the terms and conditions set forth in this Agreement for the purpose of
developing a product in the field of ex-vivo genetic transduction combining
Nexell's technology and Takara's product.

                             TERMS AND CONDITIONS
                             --------------------

  NOW, THEREFORE, in consideration of the mutual covenants and agreements
hereinafter set forth, the parties hereto hereby agree as follows:

  1.  Definitions.
      -----------

      1.1 "Co-Development Inventions" shall mean all discoveries, inventions,
methods, ideas and the like, whether or not patentable, first conceived or
reduced to practice in the course of performance of the Research.

      1.2 "Co-Development Know-How" shall mean all techniques, data and
materials arising from or in connection with the performance of the Research,
including without limitation all inventions, practices, methods, knowledge,
know-how, skill, experience, test data, analytic and quality control data,
patent and legal data or descriptions.

      1.3 "Co-Development Patents" shall mean any and all patents and patent
applications, including extensions, registrations, confirmations, reissues,
continuations, continuations-in-part, divisionals, reexaminations or renewals,
based upon or resulting from Co-Development Inventions or Co-Development Know-
How.

      1.4 "Field" shall mean the field of enhancement of ex vivo genetic
transduction using RetroNectin on a solid surface.

      1.5 "Product" shall mean any drug or device in the Field that includes Co-
Development Inventions or Co-Development Know-How.

                                       1
<PAGE>

      1.6 "Research" shall mean the research and development of a pre-packaged
combination product for ex-vivo genetic transduction using Nexell technology and
Takara's product, as described more fully in the Research and Development Plan
attached as Exhibit A hereto.

  2.  Scope of Co-Development.
      -----------------------

      2.1 Research.  The purpose of the Research is to conduct research in
          --------
accordance with the Research and Development Plan to identify potential Products
for commercialization by the parties.  During the term of this Agreement, each
party shall use its commercially reasonable and diligent efforts to perform its
obligations under the Research and Development Plan.  Notwithstanding the
foregoing, neither party makes any representations or warranties regarding its
ability to achieve, nor shall it be bound hereby to accomplish, any particular
research objective or results or to develop any Products.

      2.2 Nexell Contributions.  Nexell shall contribute to the Research such
          --------------------
number of cell culture containers as may be needed for performance of the
Research in accordance with the Research and Development Plan.

      2.3 Takara Contributions.  Promptly following the Effective Date, and at
          --------------------
such times thereafter as requested by Nexell, Takara shall cause to be
transferred to Nexell vials of RetroNectin in reasonable quantities as may be
needed for performance of the Research in accordance with the Research and
Development Plan.

      2.4 Review of Research and Development Plan. Prior to the last business
          ---------------------------------------
day of each six-month period following the Effective Date, the parties shall in
good faith jointly review the Research and Development Plan. On the last
business day of each six-month period following the Effective Date, the parties
shall make such adjustments to the Research and Development Plan as they may in
good faith deem necessary based on the progress of the Research at such time.
Such adjustments shall be made in a writing signed by both parties and
incorporated by reference into this Agreement.

  3.  Research and Development Costs.  All direct and indirect costs incurred in
      ------------------------------
connection with performance of the Research, other than the costs described in
paragraph 3.1 above, shall be shared equally by Nexell and Takara.  Either of
the parties shall promptly reimburse the other party for one-half of all such
costs upon written request by Nexell therefor.  The parties currently estimate
that such costs will be approximately $60,000.  In the event such costs exceed
$60,000, the parties shall negotiate in good faith the conditions of
reimbursement for such excess costs.

  4.  Intellectual Property.
      ---------------------

      4.1 Joint Ownership.  Nexell and Takara shall be joint owners of all Co-
          ---------------
Development Inventions and Co-Development Know-How, with ownership rights under
any Co-Development Patents as fully entitled by law.  Each party shall provide
to the other any invention disclosure submitted in the normal course to the
disclosing party's patent counsel and disclosing a Co-Development Invention.
Such invention disclosures shall be provided to the other party promptly after
submission and in no event later than fifteen (15) days after the disclosure was
submitted to patent counsel.

                                       2
<PAGE>

     4.2  Patent Filings.  Nexell shall be responsible for the preparation,
          --------------
filing, prosecution and maintenance of Co-Development Patents in each country
agreed to by the parties.  The parties shall share equally the costs of
preparing, filing, prosecuting and maintaining the Co-Development Patents, and
Takara shall reimburse Nexell accordingly for all of such costs incurred by
Nexell on behalf of Takara prior to and following the Effective Date.  If either
party elects not to file or maintain a Co-Development Patent as provided herein,
such party shall give notice to the other party and, upon receipt of notice,
such other party shall have the right, but not the obligation, to file and
maintain such Co-Development Patent in its own name and at its own expense.  If
the other party elects to file and maintain the Co-Development Patent, then the
party deciding not to so file or maintain shall assign to such other party the
rights in the Co-Development Patent.

  5.  Commercialization and Marketing Rights.
      --------------------------------------

      5.1 As soon as practicable following the Effective Date, the parties shall
negotiate in good faith the terms of one or more agreements as are customary in
commercialization transactions, which agreements address the rights and
obligations of the parties to sell the Products for research purposes only
worldwide, including but not limited to the parties' rights and obligations with
respect to marketing, supply and trademark use.  Except as otherwise
specifically provided herein, this Agreement shall terminate upon execution of
such definitive documents.

          (a)  The agreements shall provide for assembling of Products by
Nexell, for the outer packaging of Products to be consistent in form with
Nexell's other products, and for the packaging of the RetroNectin product
included in the Products to be consistent in form with Takara's other products.

          (b)  The agreements shall include the following allocation of
marketing rights for the Products, with each party being entitled to retain for
itself all benefits from sales by it in the territory to which it has marketing
rights:

               (i) Takara shall have exclusive marketing rights in Japan, Korea,
Taiwan and China.

               (ii) Nexell shall have exclusive marketing rights in North
America and Australia.

               (iii)  Takara and Nexell shall have co-marketing rights in Europe
as follows: (a) Takara shall have exclusive marketing rights to the research
market (including universities and hospitals), and (b) Nexell shall have
exclusive marketing rights to customers that have previously purchased Isolex(R)
or CELLEXTRA products.

          (c)  The agreements shall provide that the parties will negotiate in
good faith the terms of one or more agreements as are customary in
commercialization transactions, which agreements address the rights and
obligations of the parties to sell the Products for profit worldwide, including
but not limited to the parties' rights and obligations with respect to
marketing, supply, regulatory approval and trademark use.

          (d)  The agreements shall provide for expiration (i) concurrently with
the expiration or termination of the Distribution Agreement between the parties
of even date herewith, or (ii) at

                                       3
<PAGE>

such earlier time as the parties enter into the agreements described in
paragraph (c) above.

     5.2   If the parties are unable to agree upon definitive agreements as
described in paragraph 5.1, the parties shall follow the dispute resolution
procedures of Section 10.2 hereof.

  6. Confidentiality.
     ---------------

     6.1 Except to the extent expressly authorized by this Agreement or
otherwise agreed to by the parties in writing, during the term of this Agreement
and five years thereafter, the receiving party shall keep confidential and shall
not publish or otherwise disclose or use for any purpose, other than as
expressly provided in this Agreement, any inventions, know-how or other
materials furnished to it by the other party pursuant to this Agreement or
developed or acquired in connection with the Research (collectively,
"Confidential Information").

     6.2 Confidential Information shall not include information that the
receiving party establishes:

      (a) was already known to the receiving party, other than under an
obligation of confidentiality, at the time of disclosure by the other party;

      (b) was generally available to the public or otherwise part of the public
domain at the time of its disclosure to the receiving party;

      (c) became generally available to the public or otherwise part of the
public domain after its disclosure and other than through any act or omission of
the receiving party in breach of this Agreement; or

      (d) was disclosed to the receiving party, other than under an obligation
of confidentiality, by a third party that had no obligation to the disclosing
party not to disclose such information to others.

     6.3 Either party may disclose Confidential Information to the extent such
disclosure is reasonably necessary in filing or prosecuting patent applications,
prosecuting or defending litigation or complying with applicable governmental
regulations, provided that a party making any such disclosure gives prompt
notice to the other party of such required disclosure and (except to the extent
inappropriate in the case of patent applications) will use its reasonable
efforts to secure confidential treatment of such Confidential Information
required to be disclosed and to minimize the extent of such disclosure.

     6.4 Upon expiration or termination of this Agreement, each party shall
return to the other party all Confidential Information obtained by it, as well
as all data and records containing Confidential Information.

  7. Publication.  Either party may publish or present the results of the
     -----------
Research subject to the prior review by the other party for patentability and
protection of Confidential Information.  Each party shall provide to the other
the opportunity to review any proposed abstract, manuscript or presentation that
covers the results of the Research by delivering a copy thereof to the other
party no less than forty-five (45) days before its intended submission for
publication or presentation.

                                       4
<PAGE>

The reviewing party shall have thirty (30) days from its receipt of any such
material in which to notify the submitting party in writing of any specific
concern, based upon either the need to seek patent protection or concern
regarding competitive disadvantage. In the absence of such a notice within the
thirty (30) day period, the publication or presentation shall be deemed approved
by the reviewing party. Each party also agrees to delete from any such proposed
presentation any Confidential Information of the other party upon its reasonably
request based upon the commercial value of the secrecy of such information.

  8. Representations and Warranties.
     ------------------------------

     8.1  No Conflicting Grants.  Neither party has granted, and will not grant
          ---------------------
during the term of this Agreement, any right to a third party relating to its
respective contributions to the Research that would conflict with the rights
granted to the other party under this Agreement.

     8.2  Limitation on Warranties. Nothing in this Agreement shall be construed
          ------------------------
as a representation or warranty by either party to the other that an
intellectual property right owned or controlled by such party is valid,
enforceable, or not infringed by any third party, or that the practice of such
rights does not infringe any property right of any third party. EXCEPT AS
EXPRESSLY MADE HEREIN, EACH PARTY DISCLAIMS ANY WARRANTY, EXPRESS OR IMPLIED,
INCLUDING (WITHOUT LIMITATION) ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR ANY PARTICULAR PURPOSE OR USE, OR ANY REPRESENTATION OR WARRANTY
THAT ANY PRODUCT WILL NOT INFRINGE ANY THIRD PARTY'S INTELLECTUAL PROPERTY
RIGHTS. NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY SPECIAL, INCIDENTAL
OR CONSEQUENTIAL DAMAGES ARISING OUT OF OR RELATED TO THIS AGREEMENT.

  9. Term and Termination.
     --------------------

     9.1 Term.  Unless earlier terminated or extended as provided in this
         ----
Agreement, the term of this Agreement shall commence upon the Effective Date and
shall continue in effect until June 30, 2001.  At the end of such term, the
parties may renew this Agreement upon such terms and conditions as may be
mutually agreed upon.

     9.2 Termination for Cause. Either party may terminate this Agreement in any
         ---------------------
of the following circumstances at the times indicated:

          (a)  If the other party breaches this Agreement at any time and has
not cured such breach within thirty (30) days after written notice thereof or,
if such breach is not curable within that period, then the non-breaching party
may terminate this Agreement upon written notice to the other party.

          (b)  Automatically, with no further action of either party, if a
receiver is appointed for a party or its property, a party makes an assignment
for the benefit of its creditors, any proceedings are commenced by, for or
against a party under any bankruptcy, insolvency or debtor's relief law, or a
party is liquidated or dissolved.

     9.3  Survival. Expiration or termination of this Agreement shall not
          --------
relieve the parties of any obligation accruing prior to such expiration or
termination, and the provisions of Sections 4,

                                       5
<PAGE>

5, and 6 shall survive the expiration or termination of this Agreement.

  10. Miscellaneous.
      -------------

      10.1  Force Majeure.  Neither party shall be liable for any failure to
            -------------
perform as contemplated by this Agreement to the extent due to causes beyond its
reasonable control, such as acts of God, acts of civil or military authorities,
fires, strikes, floods, wars, riots and other causes of a similar nature.

      10.2  Disputes and Arbitration.  The parties hereto are convinced that a
            ------------------------
large part of contract litigation is caused by a failure to reduce the essential
terms and conditions to writing and that much of the remainder is caused by
weaknesses or various kinds in written contracts.  Thus, they have endeavored to
use every care and caution in the preparation of this Agreement.  Nevertheless,
a relationship of this character may pose new problems from time to time
requiring subsequent resolution.  Therefore, it is the aim and intention of the
parties, in their mutual interests, to provide a practical and dignified means
for friendly adjustment of any differences in the interpretation of this
Agreement or the settlement of any disputes that may arise hereunder between the
parties.

            (a) Each party agrees to bring all such matters to the attention of
the other prior to instituting any arbitration as provided herein.  This shall
be done without prejudicing their harmonious relationship and operations
hereunder, and the offices of either party and their facilities shall be
available at all times for the prompt and effective adjustment of all such
differences under friendly and courteous circumstances.

            (b) If the dispute cannot be resolved within twenty (20) days after
being brought to a party's attention as described in paragraph (a) above, the
parties shall refer the dispute to the respective officers designated below (or
their successors) for attempted resolution by good faith negotiations within
forty (40) days of the notice described in paragraph (a) above:

            For Nexell:  ______________________________

            For Takara:  ______________________________

            (c) In the event the officers are unable to resolve such disputes on
behalf of the parties within forty (40) days of the notice described in
paragraph (a) above, the parties hereby agree to submit any and all disputes
arising hereunder to binding arbitration under the commercial rules of the
American Arbitration Association in Los Angeles, California.

      10.3  Notices.  All written notices or other written communications
            -------
required under this Agreement shall be deemed properly given when provided to
the parties entitled thereto by personal delivery (including delivery by
commercial services such as messengers and air freight forwarders), by
electronic means (such as by electronic mail, telex or facsimile transmission)
or by mail sent registered or certified mail, postage prepaid at the following
addresses (or to such other address of a party designated in writing by such
party to the others):

                                       6
<PAGE>

     COMPANY:       Nexell Therapeutics Inc.
                    9 Parker
                    Irvine, California 92818
                    Attn: William Wong
                    Fax No. (949) 470-6645

     DISTRIBUTOR:   Takara Shuzo Co., Ltd.
                    Sseta 3-4-1, Otsu
                    Shiga, 520-2193
                    Attn:  Ikumoshin Kato
                    Fax No.: 077-543-9254

All notices given by electronic means shall be confirmed by delivering to the
party entitled thereto a copy of said notice by certified or registered mail,
postage prepaid, return receipt requested.  All written notices shall be deemed
delivered and properly received upon the earlier of five (5) days after mailing
the confirmation notice or upon actual receipt of the notice provided by
personal delivery or electronic means.

      13.4  Exhibits.  All exhibits, attached hereto and referred to herein, are
            --------
an integral part of this Agreement and are incorporated herein by reference
hereby.

      10.5  Amendments.  Unless expressly permitted herein, no supplement,
            ----------
modification or amendment of any term, provision or condition of this Agreement
(including this Paragraph) shall be binding or enforceable unless evidenced in a
writing executed by the parties hereto.

      10.6  Entire Agreement and Waiver.  This Agreement contains the entire
            ---------------------------
agreement between the parties hereto and supersedes all prior and
contemporaneous agreements, arrangements, negotiations and understandings
between the parties hereto, relating to the subject matter hereof. There are no
other agreements, understandings, statements, promises or inducements, oral or
otherwise, contrary to the terms of this Agreement. No representations,
warranties, covenants or conditions, express or implied, whether by statute or
otherwise, other than as set forth herein, have been made by any party hereto.
No waiver of any term, provision, or condition of this Agreement, whether by
conduct or otherwise, in any one or more instances, shall be deemed to be, or
shall constitute, a waiver of any other provision hereof, whether or not
similar, nor shall such waiver constitute a continuing waiver, and no waiver
shall be binding unless executed in writing by the party making the waiver.

      10.7  No Assignment.  Neither this Agreement nor any of the rights or
            -------------
obligations hereunder shall be assignable by any party hereto without the
written consent of the other party first obtained (which consent shall not be
unreasonably withheld). Notwithstanding the foregoing, either party, without the
consent of the other, may assign this Agreement to an affiliate of such party.
However, if any assignee affiliate ceases to be an affiliate of the assignor
party, that event shall be deemed to be an assignment requiring the consent of
the other party. Subject to the foregoing, this Agreement shall be binding upon
and shall inure to the benefit of the parties hereto and their respective
representatives, successors and permitted assigns.

                                       7
<PAGE>

      10.8  Counterparts.  This Agreement may be executed in one or more
            ------------
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

      10.9  Governing Law And Disputes.  This Agreement and the performance
            --------------------------
thereof shall be construed, interpreted, applied and governed in all respects in
accordance with the internal laws of the State of California (without regard to
the application its conflict of laws).

      10.10  Reformation/Severability.  If any provision of this Agreement is
             ------------------------
declared invalid by any tribunal, then such provision shall be deemed
automatically adjusted to the minimum extent necessary to conform to the
requirements for validity as declared at such time and, as so adjusted, shall be
deemed a provision of this Agreement as though originally included herein. In
the event that the provision invalidated is of such a nature that it cannot be
so adjusted, the provision shall be deemed deleted from this Agreement as though
such provision had never been included herein. In either case, the remaining
provisions of this Agreement shall remain in effect.

      10.11  Language/Currency.  The governing language to be used for purposes
             -----------------
of the interpretation and meaning of this Agreement shall be English and all
references to dollars ($) shall be to U.S. Dollars.

      IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed and delivered by persons duly authorized as of the date first set forth
above.

NEXELL THERAPEUTICS INC.

/s/ L. William McIntosh
-----------------------
By:
Name:  L. William McIntosh
Title: President and Chief Operating Officer

TAKARA SHUZO CO., LTD.

/s/ Ikumoshin Kato
------------------
By:
Name:  Ikumoshin Kato, Ph.D.
Title: President, Biomedical Group

                                       8

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