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                                                                    EXHIBIT 10.5

                  RESEARCH AND ASSIGNMENT AND LICENSE AGREEMENT

        This Research and Assignment and License Agreement (this "Agreement") is
effective as of February 24, 1999 ("the EFFECTIVE DATE") by and between Ixsys,
Inc., a Delaware corporation, having an address at 3520 Dunhill Road, San Diego,
CA 92121 ("IXSYS"), and MedImmune, Inc., a Delaware Corporation, having offices
at 35 West Watkins Mill Road, Gaithersburg, MD 20878 ("MEDIMMUNE").

        WHEREAS, MEDIMMUNE desires that IXSYS perform certain research and
development to modify a certain antibody; and

        WHEREAS, IXSYS desires to perform such work on the terms and conditions
of this Agreement.

        NOW THEREFORE in consideration of the mutual promises and other good and
valuable consideration, the parties agree as follows:

        SECTION 1 - DEFINITIONS.

        The terms used in this Agreement have the following meaning:

        1.1 "AFFILIATE," as applied to a person or entity, means any other
person or entity controlling or controlled by or under common control with such
person or entity. The term "control" means possession of the power to direct or
cause the direction of the management and policies whether through the ownership
of voting securities, by contract or otherwise. The ownership of voting
securities of a person, organization or entity, however, shall not, in and of
itself, constitute "control" for purposes of this definition, unless said
ownership is of a majority of


                                      -1-
<PAGE>   2

the outstanding securities entitled to vote of such person, organization or
entity. Affiliate shall also mean a limited partnership in which a subsidiary of
such person, organization or entity is a general partner.

        1.2 "ANTIBODY" means an antibody that specifically binds to ***
(including, but not limited to, variants, chimeric antibodies, humanized
antibodies, recombinant antibodies, grafted antibodies, single chain antibodies,
and the like) developed by IXSYS during the term of the PROGRAM or a fragment of
such an antibody.

        1.3 "ASSIGNED MATERIALS AND INFORMATION" means all ANTIBODIES, cell
lines used by IXSYS for producing ANTIBODIES, polynucleotides encoding
ANTIBODIES, assays, vectors and constructs for producing ANTIBODIES, sequence
information regarding such ANTIBODIES and polynucleotides, and the results of
the testing and evaluation of such ANTIBODIES and information and data useful
for the manufacture, making and use of ANTIBODY, in each case which is developed
by IXSYS during the term of the PROGRAM, and only in the case of assays, vectors
and constructs, only to the extent IXSYS or its AFFILIATES has the right during
the term of the PROGRAM to assign such to MEDIMMUNE.

        1.4 "ASSIGNED PATENT(S)" means any patent or patent application (or
equivalents thereof, such as extensions or other rights that give the right to
exclude others such as Supplementary Protection Certificates) anywhere in the
world to the extent a claim thereof would be infringed by the manufacture, use,
or sale of a product comprising an ANTIBODY and that is based on ANTIBODY and/or
ASSIGNED MATERIALS AND INFORMATION.

        1.5 "DESIGNATED AMOUNT" means the total worldwide sales of products
comprising the EXISTING ANTIBODY sold by or on behalf of MEDIMMUNE for the
twelve-


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<PAGE>   3

month period prior to the time a PRODUCT receives all licensing and pricing
approvals for sale of PRODUCT in a country.

        1.6 *** means ***.

        1.7 "EXISTING IXSYS PATENT(S)" means any patent or patent application
(or equivalents thereof, such as extensions or other rights that give the right
to exclude others such as Supplementary Protection Certificates) anywhere in the
world to the extent the claims of which would be infringed by the manufacture,
use or sale of a product comprising an ANTIBODY, and only to the extent that it
is either owned by or licensed to IXSYS (with the right to grant sublicenses) or
as to which IXSYS otherwise has licensable rights, in each case, as of the
EFFECTIVE DATE.

        1.8 "FIRST COMMERCIAL SALE" means, in each country, (a) the first sale
of a PRODUCT by MEDIMMUNE, its AFFILIATE or SUBLICENSEE following approval of
its marketing by the appropriate governmental agency for the country in which
the sale is to be made, or (b) when governmental approval is not required, the
first commercial sale of a PRODUCT by MEDIMMUNE, its AFFILIATE or SUBLICENSEE in
that country.

        1.9 "FTE" means one full time equivalent scientific investigator,
together with all reasonably necessary materials, equipment and facilities used
thereby.

        1.10 "MATERIALS" means ANTIBODIES, cell lines used or developed by IXSYS
for producing ANTIBODIES, polynucleotides encoding ANTIBODIES, and the assays,
vectors and constructs for producing ANTIBODIES, in each case only to the extent
owned by or licensed to IXSYS (with the right to grant sublicenses) or as to
which IXSYS otherwise has transferable



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rights, and in the possession and control of IXSYS, in each case, that exists as
of the EFFECTIVE DATE.

        1.11 "NET SALES" means, with respect to any PRODUCT, the invoiced sales
price of such PRODUCT sold by MEDIMMUNE, its AFFILIATES and SUBLICENSEES to
independent customers who are not AFFILIATES, less (a) actual and customary
credits, allowances, discounts and rebates to, and chargebacks from the account
of, such independent customers for spoiled, damaged, out-dated, rejected or
returned PRODUCT; (b) actual freight and insurance costs incurred in
transporting such PRODUCT to such customers; (c) actual and customary cash,
quantity and trade discounts; (d) sales, use, value-added and taxes or
governmental charges (excluding what is commonly known as income taxes) incurred
in connection with the exportation or importation of such PRODUCT; (e) the cost
to MEDIMMUNE of the devices for dispensing or administering such PRODUCT as well
as diluents or similar materials which accompany such PRODUCT as it is sold and
(f) reasonable allowance for bad debt, all of the above in accordance with
Generally Accepted Accounting Principles. For purposes of determining NET SALES,
a sale shall have occurred when an invoice therefor shall be generated or the
PRODUCT shipped for delivery. Sales of PRODUCTS by MEDIMMUNE, an AFFILIATE or
SUBLICENSEE to any AFFILIATE or SUBLICENSEE which is a reseller thereof shall be
excluded, and only the subsequent sale of such PRODUCTS by AFFILIATES or
SUBLICENSEES to unrelated parties shall be deemed NET SALES hereunder.

        1.12 "PRODUCT" means a product comprising (i) an ANTIBODY, the
manufacture, use or sale of which infringes a VALID PATENT CLAIM under the
ASSIGNED PATENTS or under the EXISTING IXSYS PATENTS as to which MEDIMMUNE
retains a license under this Agreement, (ii) an ANTIBODY assigned to MEDIMMUNE
by IXSYS under this Agreement, or

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<PAGE>   5

(iii) an ANTIBODY which is derived from an ANTIBODY assigned to
MEDIMMUNE under this Agreement.

        1.13 "PROGRAM" means the research and development program described
generally in Section 2.1.

        1.14 "ROYALTY PERIOD" means, with respect to each PRODUCT in each
country in the LICENSED TERRITORY, (a) if the manufacture, use, offer for sale,
sale or import of such PRODUCT in such country at the time of the FIRST
COMMERCIAL SALE infringes a VALID PATENT CLAIM (if in an issued patent) but for
the license granted by this Agreement, the royalty period continues for as long
as such VALID PATENT CLAIM remains in effect and (if in an issued patent) is
infringed thereby but for the license granted by this Agreement, or (b)
otherwise, *** years from the date of the FIRST COMMERCIAL SALE of such
PRODUCT in such country.

        1.15   ***

        1.16 "SUBLICENSEE" means any AFFILIATE or THIRD PARTY that is granted a
sublicense by MEDIMMUNE under this Agreement.

        1.17 "THIRD PARTY(IES)" means a person or entity other than IXSYS or
MEDIMMUNE or any of their AFFILIATES.

        1.18 The term "VALID PATENT CLAIM" shall mean either (a) a claim of an
issued and unexpired patent included within the ASSIGNED PATENTS or the EXISTING
IXSYS PATENTS, which has not been held permanently revoked, unenforceable or
invalid by a decision of a court or other governmental agency of competent
jurisdiction, unappealable or unappealed within the time allowed for appeal, and
which has not been admitted to be invalid or unenforceable through reissue or
disclaimer or otherwise or (b) a claim of a pending patent

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application included within the ASSIGNED PATENTS or the EXISTING IXSYS PATENTS,
which claim was filed in good faith and has not been abandoned or finally
disallowed without the possibility of appeal or refiling of such application,
the subject matter of which has not been pending for more than five (5) years,
including the pendency of any prior application.

        1.19 The use herein of the plural shall include the singular, and the
use of the masculine shall include the feminine.

        1.20   All dollars are United States Dollars.

        SECTION 2 - THE PROGRAM

        2.1 (a) IXSYS shall perform a program of research and development in
accordance with this Section 2 to produce modified antibodies to the
***, and shall use its commercially reasonable efforts to produce a modified
antibody of the *** that *** as compared to ***, as measured in the *** model.

            (b) The parties shall prepare a mutually acceptable written workplan
for the PROGRAM. Any such workplan shall be modified and supplemented from time
to time only by the mutual written agreement of the parties.

            (c) The research and development work to be performed by IXSYS under
the PROGRAM shall not be performed by a THIRD PARTY without the written approval
of MEDIMMUNE.


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            (d) IXSYS shall allocate not less than *** FTEs to conduct the
PROGRAM and at the request of MEDIMMUNE upon sixty (60) days' prior written
notice, IXSYS shall be required to allocate up to *** FTEs to conduct the
PROGRAM, provided that once the FTEs are increased, MEDIMMUNE will not have
the right to decrease the number of FTEs.

            (e) The PROGRAM shall commence on the date thirty (30) days after
the EFFECTIVE DATE and continue for a term of *** thereafter provided however
at the request of MEDIMMUNE, and upon sixty (60) days' prior written notice
to IXSYS, the term shall be extended for up to *** in *** increments.

        2.2 It is understood that MEDIMMUNE intends to measure the potency of
ANTIBODY obtained from IXSYS in the *** model to determine the potency thereof
with a view toward developing and commercializing such an ANTIBODY. It is
further understood and agreed that ANTIBODY obtained from IXSYS that is
tested, if any, shall be determined by MEDIMMUNE, within its sole
and absolute discretion, that MEDIMMUNE, within its sole and absolute
discretion, shall determine whether or not to develop and/or commercialize a
PRODUCT and which, if any, PRODUCT shall be developed and commercialized and in
which, if any, countries it should be developed and commercialized.

        2.3 (a) MEDIMMUNE shall pay IXSYS at the rate equal to *** per FTE
required to be allocated to the PROGRAM as set forth above, payable in equal
quarterly installments of *** per FTE per quarter in advance on the
EFFECTIVE DATE and each three (3)


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month anniversary thereof during the term of the PROGRAM for the period of
Section 2.1(e) which amount covers both direct and indirect expenses. If the
number of FTEs is increased in any quarter, the pro-rata amount for such quarter
for such increase shall be paid for the remainder of such quarter (and provided
that such payment shall be due on the effective date of such increase if the
notice and effective date of such increase is in the same calendar quarter).

            (b) MEDIMMUNE shall not be required to make any payments to IXSYS
for research that exceeds the aggregate amount described in Section 2.3(a), and
IXSYS shall not be required to perform research or development under the PROGRAM
that exceeds such aggregate amount, unless agreed to in writing by both parties.

        2.4 Within ten (10) days after the EFFECTIVE DATE, MEDIMMUNE shall
provide IXSYS with such quantity (as reasonably sufficient to enable IXSYS to
conduct the PROGRAM) of the ***, polynucleotides encoding the *** and ***, the
*** and together with any other information and data which the parties mutually
agree is reasonably necessary for IXSYS to conduct the PROGRAM. Additionally,
during the term of the PROGRAM, MEDIMMUNE shall provide IXSYS, at MEDIMMUNE's
sole cost, with such technical assistance as IXSYS reasonably requests regarding
the use of such assay under the PROGRAM.

        2.5 During the term of the PROGRAM, IXSYS shall permit representatives
of MEDIMMUNE, upon reasonable notice during normal business hours at MEDIMMUNE's
expense, to visit the facilities where IXSYS is conducting the PROGRAM and
during such visits shall make employees of IXSYS, who are performing research
and development under the



                                      -8-

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PROGRAM, reasonably available to representatives of MEDIMMUNE to discuss such
research and development and the results thereof.

        2.6 Not later less than once each calendar quarter during the term of
the PROGRAM, and not more than thirty (30) days after conclusion of the term of
the PROGRAM, IXSYS, at the cost and expense of IXSYS, shall transfer to
MEDIMMUNE the ASSIGNED MATERIALS AND INFORMATION and any other MATERIALS not
previously transferred to MEDIMMUNE hereunder.

        2.7 For a period of six (6) months after the conclusion of the term of
the PROGRAM, IXSYS, at the cost and expense of IXSYS, shall provide MEDIMMUNE
with such technical assistance as reasonably requested by MEDIMMUNE with respect
to the use of the ASSIGNED MATERIALS AND INFORMATION, and MATERIALS hereunder.

        2.8 Except as permitted by MEDIMMUNE, during the term of the PROGRAM and
for a period of *** years thereafter, IXSYS and its AFFILIATES shall not (1)
research, develop, make, have made, use or sell any antibody or any antibody
fragment directed to *** or any polynucleotide encoding the foregoing, (2)
perform research or development work for a THIRD PARTY with respect to any such
antibody, fragment or polynucleotide , or (3) research, develop, make, have
made, use or sell or grant rights to a THIRD PARTY with respect to any such
antibody, fragment or polynucleotide that was conceived or reduced to practice
during the term of the PROGRAM or within a period of *** years thereafter.

        2.9 IXSYS shall have the right to publish the results of IXSYS' work
under the PROGRAM; provided, however, that IXSYS shall provide MEDIMMUNE the
opportunity to


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review any proposed manuscripts or any other proposed disclosure describing such
work sixty (60) days prior to their submission for publication or other proposed
disclosure. MEDIMMUNE and IXSYS shall discuss whether or not such publication or
disclosure should occur and it is expressly understood that MEDIMMUNE shall have
the sole right to make a final determination as to whether or not such
publication or disclosure shall occur provided that such determination is not
unreasonable. It shall not be unreasonable to deny publication on the basis that
the information proposed to be published is not generally available to the
public and may aid a competitor in developing a competitive product.

        SECTION 3 - ASSIGNMENT AND LICENSE GRANTS.

        3.1 (a) IXSYS hereby grants to MEDIMMUNE and MEDIMMUNE hereby accepts
from IXSYS a sole and exclusive worldwide right and license (or sublicense, as
applicable) (1) under and to EXISTING IXSYS PATENTS to research, develop, make,
have made, use, import, export and sell, offer to sell or have sold PRODUCTS and
(2) to make, have made and to use MATERIALS for all the purposes of Section
3.1(a)(1). Notwithstanding anything to the contrary in this Agreement, the
rights and licenses granted to MEDIMMUNE under this Agreement exclude any right
or license (express or implied) under any IXSYS patent rights or know-how
regarding the generation, discovery or modification of antibody libraries,
antibodies or fragments thereof, generally.

        (b) To the extent that the rights and licenses granted to MEDIMMUNE
under Section 3.1(a) is a sublicense under a license agreement between IXSYS and
a THIRD PARTY, the rights and licenses granted to MEDIMMUNE under such
sublicense are limited to the extent that IXSYS has the right to grant
sublicenses under such license agreement and such sublicense



                                      -10-
<PAGE>   11

is subject to the terms, conditions and restrictions of such license agreement
that are applicable to a sublicensee thereunder. MEDIMMUNE shall not take or
omit to take any action the effect of which would cause IXSYS to be in breach of
IXSYS' obligations under such license agreements (without regard to any
applicable cure or notice requirements thereof).

        3.2 MEDIMMUNE shall have the right to grant sublicenses under the
licenses and sublicenses granted under Section 3.1 (with the right to grant
further sublicenses, subject to any terms, conditions and restrictions on
further sublicensing under any license agreement under which MEDIMMUNE is a
sublicensee) to its AFFILIATES and THIRD PARTIES. Each such sublicense shall be
subject to the terms and conditions of this Agreement.

        3.3 The licenses granted hereunder include the right of MEDIMMUNE, its
AFFILIATES and SUBLICENSEES to grant to the purchaser thereof the right to use
and/or resell a purchased PRODUCT for which a royalty has been paid hereunder on
NET SALES of such PRODUCT (determined in accordance with Section 1.11), without
payment of any further royalty to IXSYS.

        3.4 (a) IXSYS agrees to assign and hereby assigns to MEDIMMUNE all
right, title and interest in and to the ASSIGNED MATERIALS AND INFORMATION
together with all ASSIGNED PATENTS and other intellectual property rights
arising therefrom.

            (b) IXSYS agrees to cooperate with MEDIMMUNE and cause its employees
to cooperate with MEDIMMUNE and to perform all acts, at MEDIMMUNE's request on
reasonable notice and during normal business hours, as reasonably necessary (i)
to perfect MEDIMMUNE's ownership interest in and to the ASSIGNED MATERIALS AND
INFORMATION together with all ASSIGNED PATENTS and other intellectual property
rights arising therefrom, and (ii) to facilitate the preparation, filing,
prosecution and enforcement of the


                                      -11-
<PAGE>   12

ASSIGNED PATENTS. MEDIMMUNE shall reimburse IXSYS on demand for the reasonable
cost to IXSYS (at the rate set forth in Section 2.3(a) plus all out-of-pocket
expenses) incurred in connection therewith.

            (c) IXSYS hereby reserves the nonexclusive, nontransferable right to
use information and data that are included in ASSIGNED MATERIALS AND INFORMATION
for its own internal research use; provided, however, that IXSYS shall not use
the ASSIGNED MATERIALS AND INFORMATION to make, have made, use or sell any
antibody directed to ***, or perform research or development work for a THIRD
PARTY with respect to any such antibody.

        SECTION 4 - CONFIDENTIALITY.

        4.1 During the term of this Agreement, IXSYS agrees not to provide or
disclose to a THIRD PARTY any MATERIALS without the written permission of
MEDIMMUNE.

        4.2 After the date of this Agreement, subject to Section 2.9, IXSYS
agrees not to provide or disclose to a THIRD PARTY any ASSIGNED MATERIALS AND
INFORMATION without the written permission of MEDIMMUNE.

        4.3 During the term of this Agreement, it is contemplated that each
party will disclose to the other party confidential information which is owned
or controlled by the party providing such information or which that party is
obligated to maintain in confidence and which is designated by the party
providing such information as confidential ("Confidential Information"). Each
party shall have the right to refuse to accept the other party's Confidential
Information. Each party agrees to retain the other party's Confidential
Information in confidence, to limit disclosure of any such Confidential
Information to its officers, directors, employees, consultants,


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sublicensees and permitted assigns on a need to know basis, to use the other
party's Confidential Information only for the purposes of this Agreement, and
not to disclose any such Confidential Information to any other person or entity
without the prior written consent of the party providing such Confidential
Information. For the avoidance of doubt ASSIGNED MATERIALS AND INFORMATION are
Confidential Information of MEDIMMUNE.

        4.4 The obligations of confidentiality and non-use of Sections 4.1, 4.2
and 4.3 will not apply to:

               (i) Confidential Information generally known to the public prior
        to its disclosure hereunder; or

               (ii) Confidential Information that subsequently becomes known to
        the public by some means other than a breach of this Agreement;

               (iii) Confidential Information that is subsequently disclosed to
        the receiving party by a third party having a lawful right to make such
        disclosure; or

               (iv) is approved for release by the parties.


        4.5 Neither party shall disclose any terms or conditions of this
Agreement to any third party without the prior consent of the other party;
provided, however, that a party may disclose the terms or conditions of this
Agreement, (a) on a need-to-know basis to its legal and financial advisors to
the extent such disclosure is reasonably necessary in connection with such
party's activities expressly permitted by this Agreement and ordinary and
customary business operations, and (b) to a third party in connection with (i)
an equity investment in such party, (ii) a merger, consolidation, change in
control or similar transaction by such party, or (iii) the transfer or sale of
all or substantially all of the assets of such party. Notwithstanding the
foregoing, prior

                                      -13-
<PAGE>   14

to execution of this Agreement the parties have agreed upon the substance of
information that may be used to describe the terms and conditions of this
transaction, and each party may disclose such information, as modified by mutual
written agreement of the parties, without the consent of the other party.

        4.6 The obligations of this Section 4 shall not apply to the extent that
a party is required to disclose information by applicable law, regulation or
bona fide legal process, provided that the party required to make the disclosure
takes reasonable steps to restrict and maintain confidentiality of such
disclosure and provides reasonable prior notice to the other party.

        4.7 Notwithstanding the foregoing, MEDIMMUNE shall have the right to
disclose Confidential Information of IXSYS to a THIRD PARTY with whom MEDIMMUNE
has or proposes to enter into a business relationship and who undertakes an
obligation of confidentiality and non-use with respect to such information, at
least as restrictive as the obligation under this Section 4.

        4.8 The parties' obligations under this Section 4 shall terminate five
(5) years after the expiration or termination of this Agreement.

        SECTION 5 - ROYALTIES.

        5.1 During the ROYALTY PERIOD, MEDIMMUNE shall pay royalties to IXSYS
for PRODUCTS as follows:

            (a) *** of that portion of NET SALES of PRODUCTS in a calendar
year up to the DESIGNATED AMOUNT;



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            (b) *** of that portion of NET SALES of PRODUCTS in a calendar
year above the DESIGNATED AMOUNT.

            The cumulative NET SALES for a calendar year shall be calculated
based on worldwide NET SALES.

        5.2 In the event that a PRODUCT is sold in combination with a
therapeutically active component that is not a PRODUCT (such combination being a
"Combination Product"), then NET SALES of such Combination Product upon which a
royalty is paid shall be subject to the following adjustment. If the PRODUCT and
the other therapeutically active component are sold separately in a country,
then NET SALES of such Combination Product in such country upon which a royalty
is paid shall be multiplied by the fraction A/A+B, where A equals the average
sales price of such PRODUCT sold separately in such country, and B equals the
average sales price of the other therapeutically active component sold
separately in such country. Otherwise, the parties shall enter into good faith
negotiations and attempt to reach mutual agreement to determine an appropriate
adjustment to the NET SALES of such Combination Product in a country to reflect
the relative contributions of the PRODUCT and the other therapeutically active
component to the value of the Combination Product in such country. If such
mutual agreement is not reached within ninety (90) days after commencement of
such negotiations, then the NET SALES of such Combination Product in such
country shall be determined by binding arbitration under Section 11.2.

        5.3 MEDIMMUNE shall keep, and shall cause each of its AFFILIATES and
SUBLICENSEES to keep, full and accurate books of account containing all
particulars that may be necessary for the purpose of calculating all royalties
payable to IXSYS. Such books of account, with all necessary supporting data,
shall be kept at their principal place of business, and


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for the three (3) years next following the end of the calendar year to which
each pertains, shall be open for inspection by an independent certified
accountant selected by IXSYS and reasonably acceptable to MEDIMMUNE upon
reasonable notice during normal business hours at IXSYS' expense for the sole
purpose of verifying royalty statements or compliance with this Agreement, but
in no event more than once in each calendar year. All information and data
offered shall be used only for the purpose of verifying royalties and shall be
treated as MEDIMMUNE Confidential Information subject to the obligations of this
Agreement.

        5.4 With each quarterly payment, MEDIMMUNE shall deliver to IXSYS a full
and accurate accounting of the calculation of the royalties owing hereunder to
include at least the following information:

            (a) Quantity of each PRODUCT subject to royalty sold (by country) by
MEDIMMUNE, its AFFILIATES and SUBLICENSEES;

            (b) NET SALES for each PRODUCT (by country);

            (c) The calculation of the gross royalties (before deductions) for
each PRODUCT (by country) and any deductions, offsets and credits therefrom; and

            (d) Total royalties payable to IXSYS for each PRODUCT (by country)
and the total royalties payable to IXSYS for all PRODUCTS (for all countries).

        5.5 In each year the amount of royalty due shall be calculated quarterly
as of March 31, June 30, September 30 and December 31 (each being the last day
of an "ACCOUNTING PERIOD") and shall be paid quarterly within the sixty (60)
days next following such date. Every such payment shall be supported by the
accounting prescribed in Section 5.4 and shall be made in United States
currency. Whenever for the purpose of calculating royalties conversion from any
foreign currency shall be required, such conversion shall be at the average of
the rate of

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<PAGE>   17

exchange (local currency per US$1) published in the Western Edition of The Wall
Street Journal under the caption "Currency Trading" for the last business day of
each month during the applicable ACCOUNTING PERIOD.

        5.6 If the transfer of or the conversion into United States Dollar
equivalent of any remittance due hereunder is not lawful or possible in any
country, such remittance shall be made by the deposit thereof in the currency of
the country to the credit and account of IXSYS or its nominee in any commercial
bank or trust company located in that country, prompt notice of which shall be
given to IXSYS. IXSYS shall be advised in writing in advance by MEDIMMUNE and
provide to MEDIMMUNE a nominee, if so desired.

        5.7 Any tax required to be withheld by MEDIMMUNE under the laws of any
foreign country for the account of IXSYS shall be promptly paid by MEDIMMUNE for
and on behalf of IXSYS to the appropriate governmental authority, and MEDIMMUNE
shall furnish IXSYS with proof of payment of such tax. Any such tax actually
paid on IXSYS' behalf shall be deducted from royalty payments due IXSYS.

        5.8 Only one royalty shall be due and payable under each of the
applicable subsections under this Section 5 for the manufacture, use and sale of
a PRODUCT irrespective of the number of patents or claims thereof which cover
the manufacture, use and sale of such PRODUCT.

        5.9 (a) MEDIMMUNE shall pay to IXSYS the following milestone payments
upon the occurrence of the following events with respect to a PRODUCT:

        EVENT                                                          PAYMENT

        (i) Demonstration in the ***
        model that a PRODUCT has a ***
        as compared to ***


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                                 -17-

<PAGE>   18

        ***                                                           $ ***

        (ii) Demonstration in the ***
        model that a PRODUCT has a ***
        as compared to ***                                            $ ***

        (iii) Filing an IND (or its foreign equivalent) for a
        PRODUCT                                                       $ ***

        (iv) Obtains approval of a Biologics License Application
        (or its foreign equivalent) for a PRODUCT                     $ ***

            (b) The milestone payments under Section 5.9(a) are due and payable
sixty (60) days after the applicable milestone occurs.

            (c) *** of all milestone payments paid under Section 5.9(a)
are creditable against up to *** of each royalty payment that is to be made
pursuant to Section 5.1 until the full amount of such credit has been taken.

            (d) The total payment under Section 5.9(a)(i) and 5.9(a)(ii) shall
not exceed ***, and the total milestone payments for any and all PRODUCT
shall not exceed ***.

        SECTION 6 - WARRANTIES.

        6.1 Each of IXSYS and MEDIMMUNE warrants and represents to the other
that:

            (a) it has the corporate power and authority and the legal right to
enter into this Agreement and to perform its obligations hereunder;

            (b) it has taken all necessary corporate action on its part to
authorize the execution and delivery of this Agreement and the performance of
its obligations hereunder; and


*** CONFIDENTIAL MATERIAL REDACTED AND FILED SEPARATELY WITH THE COMMISSION


                                      -18-

<PAGE>   19

            (c) this Agreement has been duly executed and delivered on its
behalf, and constitutes a legal, valid, binding obligation, enforceable against
it in accordance with its terms.

        6.2 IXSYS represents and warrants to MEDIMMUNE that:

            (a) it has not previously granted and, prior to expiration or
termination of this Agreement, will not grant any rights in the EXISTING IXSYS
PATENTS, ASSIGNED PATENTS, MATERIALS, and ASSIGNED MATERIALS AND INFORMATION
that conflict with the rights and licenses granted to MEDIMMUNE herein;

            (b) all persons performing research by or on behalf of IXSYS under
the PROGRAM will be obligated to assign to IXSYS (for re-assignment to MEDIMMUNE
hereunder), the ownership of ASSIGNED MATERIALS AND INFORMATION, the ASSIGNED
PATENTS and all other intellectual property rights arising therefrom.

        6.3 Disclaimer. EXCEPT AS OTHERWISE EXPRESSLY SET FORTH IN SECTIONS 6.1
and 6.2, NEITHER PARTY MAKES ANY REPRESENTATION OR EXTENDS ANY WARRANTIES OF ANY
KIND EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT, OR VALIDITY
OF ANY PATENT RIGHTS ISSUED OR PENDING.

        SECTION 7 - INDEMNIFICATION.

        7.1 MEDIMMUNE agrees to indemnify and hold harmless IXSYS, its
directors, officers, employees and agents (collectively, the "Indemnitees") from
and against all losses, liabilities, damages and expenses (including reasonable
attorneys' fees and costs) incurred in connection with any claims, demands,
actions or other proceedings by any third party arising


                                      -19-
<PAGE>   20

from (a) the research, development, manufacture, use or sale of ANTIBODIES or
PRODUCTS by MEDIMMUNE, its AFFILIATES or SUBLICENSEES, (b) the use of PRODUCTS
by any purchasers thereof, (c) the use by MEDIMMUNE, its AFFILIATES or
SUBLICENSEES of the EXISTING IXSYS PATENTS, the ASSIGNED MATERIALS AND
INFORMATION or the ASSIGNED PATENTS, (d) any act or omission by MEDIMMUNE, its
AFFILIATES OR SUBLICENSEES the effect of which would cause IXSYS to be in breach
of its obligations under the license agreements described in Section 3.1(b)
(without regard to any applicable cure or notice requirements thereof, or (e)
patent infringement by IXSYS during the PROGRAM based on a claim that an
ANTIBODY or ligand or assay provided by MEDIMMUNE to IXSYS infringes a patent of
a THIRD PARTY.

        7.2 If any such claims or actions are made, IXSYS shall be defended at
MEDIMMUNE's sole expense by counsel selected by MEDIMMUNE and reasonably
acceptable to IXSYS provided that IXSYS may, at its own expense, also be
represented by counsel of its own choosing.

        7.3 MEDIMMUNE's indemnification under Section 7.1 shall not apply to the
extent any loss, liability, damage or expense is attributable to the gross
negligence or intentional misconduct of the Indemnitees.

        7.4 MEDIMMUNE may not settle any such claim, demand, action or other
proceeding or otherwise consent to an adverse judgment in any such action or
other proceeding that diminishes the rights or interests of the Indemnitees
without the express written consent of the Indemnitees.


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<PAGE>   21

        7.5 IXSYS shall notify MEDIMMUNE promptly of any claim, demand, action
or other proceeding under Section 7.1 and shall reasonably cooperate with all
reasonable requests of MEDIMMUNE with respect thereto.

        SECTION 8 - ASSIGNMENT; SUCCESSORS.

        8.1 This Agreement shall not be assigned or otherwise transferred (in
whole or in part, whether voluntarily, by operation of law or otherwise) by
either of the parties without the prior written consent of the other party
(which consent shall not be unreasonably withheld); provided, however, that
either party may, without such consent, assign this Agreement and its rights and
obligations hereunder to an AFFILIATE or in connection with the transfer or sale
of all or substantially all of its business, or in the event of its merger,
consolidation, change in control or similar transaction, provided that such
assignment by IXSYS does not cause the termination of the rights and licenses
granted to MEDIMMUNE under this Agreement. Any permitted assignee shall assume
all obligations of its assignor under this Agreement. Any purported assignment
or transfer in violation of this Section 8.1 shall be void.

        8.2 Subject to the limitations on assignment herein, this Agreement
shall be binding upon and inure to the benefit of said successors in interest
and assigns of MEDIMMUNE and IXSYS.

        SECTION 9 - TERM AND TERMINATION.

        9.1 Except as otherwise specifically provided herein and unless sooner
terminated pursuant to Section 9.2 or 9.3 of this Agreement, this Agreement and
the licenses and rights granted thereunder shall remain in full force and effect
until MEDIMMUNE has no further



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<PAGE>   22

royalty obligation hereunder at which time MEDIMMUNE shall have a fully paid up,
non-cancelable, nonexclusive license to make, have made and use MATERIALS to
research, develop, make, have made, use, import, export, sell, offer to sell, or
have sold PRODUCTS.

        9.2 MEDIMMUNE shall have the right to terminate this Agreement upon
ninety (90) days prior written notice to IXSYS.

        9.3 IXSYS shall have the right to terminate this Agreement if and only
if MEDIMMUNE breaches its obligations under Section 5 or 7. If such a breach
shall occur, IXSYS shall provide MEDIMMUNE with written notice of such breach
and if such breach is not cured within thirty (30) days after such written
notice, IXSYS may terminate this Agreement by written notice to MEDIMMUNE,
provided such written notice is given within thirty (30) days after the
expiration of such initial thirty (30) day period.

        9.4 Upon any termination of this Agreement, MEDIMMUNE, at its option,
shall be entitled to sell any completed inventory of PRODUCT which remains on
hand as of the date of the termination, so long as MEDIMMUNE pays to IXSYS the
royalties applicable to said subsequent sales in accordance with the same terms
and conditions as set forth in this Agreement.

        9.5 In the event that this Agreement is terminated under Section 9.2 or
9.3, any sublicense granted under this Agreement shall remain in full force and
effect as a direct license between IXSYS and the SUBLICENSEE under the terms and
conditions of the sublicense agreement, subject to the SUBLICENSEE agreeing to
be bound to IXSYS under such terms and conditions within thirty (30) days after
IXSYS provides written notice to the SUBLICENSEE of the termination of this
Agreement. At the request of MEDIMMUNE, IXSYS will acknowledge to a SUBLICENSEE
IXSYS' obligations to the SUBLICENSEE under this paragraph.



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<PAGE>   23

        9.6 The provisions of Sections 2.8, 2.9, 3.4(c), 4, 7, 9.4, 9.5 and 9.6
shall survive any expiration or termination of this Agreement.

        9.7 Upon expiration or termination of this Agreement for any reason,
nothing herein shall be construed to release either party from any obligation
that matured prior to the effective date of such expiration or termination.

        9.8 All rights and licensing granted under or pursuant to this Agreement
by IXSYS to MEDIMMUNE are, and shall irrevocably be deemed to be, "intellectual
property" as defined in Section 101(56) of the Bankruptcy Code. In the event of
the commencement of a case by or against either party under any Chapter of the
Bankruptcy Code, this Agreement shall be deemed an executory contract and all
rights and obligations hereunder shall be determined in accordance with Section
365(n) thereof. Unless a party rejects this Agreement and the other party
decides not to retain its rights hereunder, the other party shall be entitled to
a complete duplicate of (or complete access to, as appropriate) all intellectual
property and all embodiments of such intellectual property held by the party and
the party shall not interfere with the rights of the other party, which are
expressly granted hereunder, to such intellectual property and all embodiments
of such intellectual property from another entity. Further, this Agreement shall
be deemed, upon presentation to another entity, to be the same as an express
instruction by the party to such other entity to provide such intellectual
property and all embodiments of such intellectual property directly to the other
party. Without limiting the foregoing provisions in this paragraph, the other
party shall be entitled to all post-bankruptcy-petition improvements, updates,
or developments of intellectual property created hereunder. If such intellectual
property is not fully developed as of the commencement of any bankruptcy case,
the other party shall have the right to complete development of the property.


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<PAGE>   24

        SECTION 10 - FORCE MAJEURE.

        10.1 No failure or omission by the parties hereto in the performance of
any obligation of this Agreement (other than an obligation for the payment of
money) shall be a breach of this Agreement, nor shall it create any liability,
if the same shall arise from any cause or causes beyond the reasonable control
of the affected party, including, but not limited to, the following, which for
purposes of this Agreement shall be regarded as beyond the control of the party
in question: acts of God; acts or omissions of any government; any rules,
regulations, or orders issued by any governmental authority or by any officer,
department, agency or instrumentality thereof; fire; storm; flood; earthquake;
accident; war; rebellion; insurrection; riot; invasion; strikes; and lockouts or
the like; provided that the party so affected shall use its commercially
reasonable efforts to avoid or remove such causes or nonperformance and shall
continue performance hereunder with the utmost dispatch whenever such causes are
removed.

        SECTION 11 - GENERAL PROVISIONS.

        11.1 The relationship between IXSYS and MEDIMMUNE is that of independent
contractors. IXSYS and MEDIMMUNE are not joint venturers, partners, principal
and agent, master and servant, employer or employee, and have no relationship
other than as independent contracting parties. IXSYS shall have no power to bind
or obligate MEDIMMUNE in any manner. Likewise, MEDIMMUNE shall have no power to
bind or obligate IXSYS in any manner.

        11.2 Any matter or disagreement under Section 5.2, which this Agreement
specifies is to be resolved by arbitration shall be submitted to a mutually
selected single arbitrator to so decide any such matter or disagreement. The
arbitrator shall conduct the arbitration in



                                      -24-
<PAGE>   25

accordance with the Rules of the American Arbitration Association, unless the
parties agree otherwise. If the parties are unable to mutually select an
arbitrator, the arbitrator shall be selected in accordance with the procedures
of the American Arbitration Association. The decision and award rendered by the
arbitrator shall be final and binding. Judgment upon the award may be entered in
any court having jurisdiction thereof. Any arbitration pursuant to this section
shall be held in San Diego, California or such other place as may be mutually
agreed upon in writing by the parties. The prevailing party in any such
arbitration shall be entitled to recover from the other party all reasonable
attorneys' fees and costs incurred by the prevailing party in connection
therewith.

        11.3 This Agreement sets forth the entire agreement and understanding
between the parties as to the subject matter thereof and supersedes all prior
agreements in this respect. There shall be no amendments or modifications to
this Agreement, except by a written document which is signed by both parties.

        11.4 This Agreement shall be construed and enforced in accordance with
the laws of the State of California without regard to the conflicts of law
principles thereof.

        11.5 The headings in this Agreement have been inserted for the
convenience of reference only and are not intended to limit or expand on the
meaning of the language contained in the particular article or section.

        11.6 Any delay in enforcing a party's rights under this Agreement or any
waiver as to a particular default or other matter shall not constitute a waiver
of a party's right to the future enforcement of its rights under this Agreement,
excepting only as to an expressed written and signed waiver as to a particular
matter for a particular period of time.



                                      -25-
<PAGE>   26

        11.7 Any notices given pursuant to this Agreement shall be in writing,
delivered by any means, addressed to the other party at its address indicated
below, or to such other address as the addressee shall have last furnished in
writing to the addressor and (except as otherwise provided in this Agreement)
shall be effective upon receipt by the addressee.

        IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date set forth above.


        IXSYS, INC.                                       MEDIMMUNE, INC.


By: /s/ Janine M. Taylor                           By:  /s/ David M. Mott

Name: Janine M. Taylor                             Name: David M. Mott

Title: President & Chief                           Title: Vice Chairman &
Operating Officer                                  Chief Financial Officer


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