STOCK PURCHASE AGREEMENT


THIS STOCK PURCHASE AGREEMENT (the "Agreement") is made as of
the 24th day of February, 1999 by and between IXSYS, INC., a
Delaware corporation (the "Company"), and MedImmune, Inc.
("Purchaser").

     W I T N E S S E T H:

     WHEREAS, the Company and Purchaser have entered into a
License Agreement dated as of even date herewith (the "License
Agreement") pursuant to which the Company has granted the
Purchaser a license to certain technology; and

     WHEREAS, pursuant to Section 6.13 of the License Agreement,
the Purchaser has agreed to purchase the Common Stock described
in this Agreement on the terms and conditions set forth herein:

     NOW, THEREFORE, the parties hereby agree as follows:

     1.  Purchase and Sale of Stock.

     1.1  Sale and Issuance of Common Stock.  Subject to the
terms and conditions of this Agreement, Purchaser agrees to
purchase and the Company agrees to sell and issue to Purchaser
(CONFIDENTIAL TREATMENT REQUESTED) shares of the Company's
Common Stock at the Closing for a purchase price (the "Purchase
Price") of (CONFIDENTIAL TREATMENT REQUESTED) per share.

     1.2  Closing.  The purchase and sale of the Common Stock
shall take place at the offices of the Company at 3520 Dunhill
Street, San Diego, California, at 10:00 A.M. on February 24,
1999 (the "Closing").  At the Closing the Company shall deliver
to Purchaser a certificate representing the Common Stock which
Purchaser is purchasing against delivery to the Company by
Purchaser of a bank wire in the amount of (CONFIDENTIAL
TREATMENT REQUESTED) payable to the Company's order.

     2.  Representations and Warranties of the Company.  The
Company hereby represents and warrants to Purchaser that:

     2.1  Organization.  The Company is a corporation duly
organized, validly existing and in good standing under the laws
of the State of Delaware and has all requisite corporate power
and authority to carry on its business as now conducted and as
proposed to be conducted and is qualified to do business as a
foreign corporation and is in good standing in each jurisdiction
in which qualification is necessary under applicable law, except
where the failure to be so qualified would not have a material
adverse effect on its business.

     2.2  Authorization.  All corporate action on the part of
the Company, its officers, directors and stockholders necessary
for the authorization, execution and delivery of this Agreement,
the performance of all obligations of the Company hereunder and
the authorization, issuance and delivery of the Common Stock
being sold hereunder, to the extent that the foregoing requires
performance on or prior to the Closing, has been taken or will
be taken on or prior to the Closing, and this Agreement
constitutes a valid and legally binding obligation of the
Company enforceable against the Company in accordance with its
terms.

     2.3  Valid Issuance of Common Stock.  The Common Stock
which is being purchased by Purchaser hereunder, when issued,
sold and delivered in accordance with the terms hereof for the
consideration expressed herein, will be duly and validly issued,
fully paid and nonassessable.

     2.4  Governmental Consents.  No consent, approval, order or
authorization of, or registration, qualification, designation,
declaration or filing with, any federal, state, local or
provincial governmental authority on the part of the Company is
required in connection with the consummation of the transactions
contemplated by this Agreement, except for any post-sale filings
pursuant to applicable state securities laws, which filings will
be effected within the applicable time periods.

     2.5  No Conflicts.  Neither the execution, delivery and
performance of this Agreement by the Company nor the
consummation by the Company of the transactions contemplated
hereby will result in the breach or violation of any of the
terms and provisions of, or constitute a default under, any
statute, any rule, regulation or order of any governmental
agency or body or any court, domestic or foreign, having
jurisdiction over the Company or any of its properties, (ii) any
agreement or instrument to which the Company is a party or by
which the Company is bound or to which any of the properties of
the Company is subject or (iii) the certificate of incorporation
or by-laws or other organizational documents of the Company,
which breach or violation would be materially adverse to the
Company.

     2.6  Capitalization.  At the Closing, the authorized
capital stock of the Company will be (i) (CONFIDENTIAL TREATMENT
REQUESTED) shares of Common Stock and (ii) (CONFIDENTIAL
TREATMENT REQUESTED)  shares of Preferred Stock.   Immediately
prior to the Closing, (CONFIDENTIAL TREATMENT REQUESTED) shares
of common stock and (CONFIDENTIAL TREATMENT REQUESTED) shares of
preferred stock (convertible as of the Closing into
(CONFIDENTIAL TREATMENT REQUESTED) shares of Common Stock)
were issued and outstanding.

     3.  Representations, Warranties and Covenants of Purchaser.
Purchaser hereby represents, warrants and covenants that:

     3.1  Authorization.  This Agreement constitutes its valid
and legally binding obligation.

     3.2  No Conflicts.  Neither the execution, delivery and
performance of this Agreement by Purchaser nor the consummation
by Purchaser of the transactions contemplated hereby will result
in the breach or violation of any of the terms and provisions
of, or constitute a default under, any statute, any rule,
regulation or order of any governmental agency or body or any
court, domestic or foreign, having jurisdiction over Purchaser
or any of its properties, (ii) any agreement or instrument to
which Purchaser is a party or by which Purchaser is a party or
by which Purchaser is bound or to which any of the properties of
Purchaser is subject or (iii) the certificate of incorporation
or by-laws or other organizational documents of Purchaser, which
breach or violation would be materially adverse to Purchaser.

     3.3  Purchase Entirely for Own Account.  This Agreement is
made with Purchaser in reliance upon Purchaser's representation
to the Company, which by Purchaser's execution of this Agreement
Purchaser hereby confirms, that the Common Stock will be
acquired for investment for Purchaser's own account, not as a
nominee or agent, and not with a view to the resale or
distribution of any part thereof, and that Purchaser has no
present intention of selling, granting any participation in, or
otherwise distributing the same.  By executing this Agreement,
Purchaser further represents that Purchaser does not have any
contract, undertaking, agreement or arrangement with any person
to sell, transfer or grant participations to such person or to
any third person, with respect to any of the Common Stock.
Purchaser represents that it has full power and authority to
enter into this Agreement.

     3.4  Investment Experience.  Purchaser  acknowledges that
it is able to fend for itself, can bear the economic risk of its
investment and has such knowledge and experience in financial or
business matters that it is capable of evaluating the merits and
risks of the investment in the Common Stock.

     3.5  Restricted Common Stock.  Purchaser understands that
the shares of Common Stock it is purchasing are characterized as
"restricted securities" under the federal securities laws
inasmuch as they are being acquired from the Company in a
transaction not involving a public offering and that under such
laws and applicable regulations such securities may be resold
without registration under the Securities Act of 1933, as
amended (the "Securities Act"), only in certain limited
circumstances.  In this connection Purchaser represents that it
is familiar with Securities and Exchange Commission (the "SEC")
Rule 144, as presently in effect, and understands the resale
limitations imposed thereby and by the Securities Act.

     3.6  Accredited Investor.  Purchaser is an accredited
investor as defined in Rule 501(a) of Regulation D of the SEC
under the Securities Act.

     3.7  Confidentiality.  Purchaser hereby represents,
warrants and covenants that it shall maintain in confidence, and
shall not use or disclose without the prior written consent of
the Company, any information identified as confidential that is
furnished to it by the Company in connection with this Agreement
(as opposed to information furnished pursuant to the License
Agreement or other agreements between the parties).  This
obligation of confidentiality shall not apply, however, to any
information (a) in the public domain through no unauthorized act
or failure to act by Purchaser, (b) lawfully disclosed to
Purchaser by a third party who possessed such information
without any obligation of confidentiality, (c) known previously
by Purchaser or lawfully developed by Purchaser independent of
any disclosure by the Company or (d) required to be disclosed by
applicable law, regulation or bona fide legal process provided
Purchaser takes reasonable steps to restrict and maintain the
confidentiality of such disclosure and provides reasonable prior
notice to the Company.  Purchaser further covenants that
Purchaser shall return to the Company all tangible materials
containing such information upon request by the Company.  This
confidentiality covenant shall expire, as to any particular
disclosure, five years after such disclosure.

     3.8  Right of First Offer in Favor of the Company.  Before
any shares of the Common Stock purchased hereunder may be sold
or transferred, such shares shall first be offered to the
Company as follows:

          (a)  Purchaser shall promptly deliver a notice to the
Company stating (i) its bona fide intention to sell or transfer
such shares, (ii) the number of such shares to be sold or
transferred, and the basic terms and conditions of such sale or
transfer, (iii) the price for which it proposes to sell or
transfer such shares, and (iv) proof satisfactory to the Company
that the proposed sale or transfer will not violate any
applicable federal or state securities laws.  The notice shall
be signed by Purchaser and state that Purchaser has a binding
commitment to sell the number of shares specified in such notice
to a third party on the terms stated in such notice.

          (b)  Within 30 days after the receipt of the notice
(the "Notice Period"), the Company may elect to purchase all or
a portion of the shares to which such notice refers, at the
price per share specified in the notice.  The election to
purchase shall be made by written notice to Purchaser.  If the
Company elects not to purchase all such shares, the Company may
assign its rights to purchase any shares not purchased by the
Company.

          (c)  If all of the shares to which the notice refers
are not elected to be purchased, as provided in subparagraph
3.8(b) hereof, Purchaser may sell the shares to the purchaser or
transferee disclosed to the Company as provided below at a price
not less than the price specified in the notice, provided that
(i) Purchaser has disclosed to the Company the identity of the
proposed purchaser or transferee within five (5) business days
of expiration of the Notice Period and prior to consummation of
the sale or transfer, (ii) such sale or transfer is consummated
within three months of the date of said notice to the Company,
and (iii) any such sale is made in compliance with applicable
federal and state securities laws and not in violation of any
other contractual restrictions to which Purchaser is bound.  The
third-party purchaser shall acquire the shares of stock subject
to the Company's rights of first offer and shall require
compliance with the procedures described in this Section 3.8.

          (d)  Any proposed transfer on terms and conditions
different from those set forth in the notice, as well as any
subsequent proposed transfer shall again be subject to the
Company's rights of first offer and shall require compliance
with the procedures described in this Section 3.8.

          (e)  Notwithstanding anything to the contrary
contained in this Agreement, this Section 3.8 shall be
terminated and shall have no further force and effect  six (6)
months after the effective date of the Company's registration of
its common equity securities pursuant to Section 12 of the
Securities Exchange Act of 1934 (the "34 Act Registration").

     3.9  Further Limitations on Disposition.  Without in any
way limiting the representations set forth above and
notwithstanding the provisions of Section 3.8, Purchaser further
agrees that:

          (a)  Purchaser shall not directly or indirectly sell,
offer to sell, contract to sell, grant any option to purchase or
otherwise transfer or dispose of all or any portion of the
Common Stock purchased hereunder, in violation of the Securities
Act, the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), or the rules of the Commission promulgated
thereunder, including Rule 144 under the Securities Act.  If
reasonably requested by the Company, Purchaser shall have
furnished the Company with an opinion of counsel, reasonably
satisfactory to the Company and its counsel, that any permitted
transfer or disposition will not require registration of such
shares under the Securities Act.  It is agreed that the Company
will not require opinions of counsel for transactions made
pursuant to Rule 144, as currently in existence, except in
unusual circumstances.

          (b)  During the period commencing as of the Closing
until (CONFIDENTIAL TREATMENT REQUESTED) months following the
conclusion of the last research and development program
conducted pursuant to the Research and Assignment and License
Agreements entered into between Purchaser and the Company
simultaneously herewith or which may later be entered into
pursuant to the Selection Agreement entered into between
Purchaser and the Company simultaneously herewith the number of
shares of Common Stock of the Company purchased hereunder which
Purchaser may, directly or indirectly, sell, offer to sell,
contract to sell, grant any option to purchase or otherwise
transfer or dispose of during the preceding (CONFIDENTIAL
TREATMENT REQUESTED) shall not exceed (CONFIDENTIAL TREATMENT
REQUESTED)  of the Company's outstanding Common Stock or Common
Stock into which outstanding Preferred Stock of the Company is
then convertible.

          (c)  During the period commencing as of the effective
date of the Company's 34 Act Registration until (CONFIDENTIAL
TREATMENT REQUESTED) days thereafter Purchaser shall not,
directly or indirectly sell, offer to sell, contract to sell,
grant any option to purchase or otherwise transfer or dispose of
(i) any of the Common Stock purchased hereunder pursuant to this
Agreement at any time during the first (CONFIDENTIAL TREATMENT
REQUESTED) day(s) of such period and (ii) not more than
(CONFIDENTIAL TREATMENT REQUESTED) of the Common Stock purchased
hereunder  at any time during the succeeding (CONFIDENTIAL
TREATMENT REQUESTED) day(s) of such period.

          (d)  Prior to Purchaser entering into any agreement or
commitment to sell, grant options to purchase or otherwise
transfer or dispose of any shares of Common Stock purchased
hereunder, Purchaser agrees to provide the Board of Directors or
President of the Company at least fourteen (14) days prior
written notice of Purchaser's intent to transfer or dispose of
such shares and to discuss with the Company in good faith a plan
for transferring or disposing of the shares in any orderly
fashion.

          (e)  Without limiting the foregoing, prior to the
effective date of the Company's 34 Act Registration, Purchaser
shall not, without the prior written consent of the Company,
directly or indirectly sell, offer to sell, grant an option to
purchase or otherwise transfer or dispose of any of the Common
Stock to any person engaged in any business directly competitive
with the Company.  For purposes of this subsection 3.9(d)
"directly competitive" shall mean the field of(CONFIDENTIAL
TREATMENT REQUESTED), or such other (CONFIDENTIAL TREATMENT
REQUESTED) field in which at least (CONFIDENTIAL TREATMENT
REQUESTED) of the Company's work force (on a full time
equivalent basis) is engaged at the time of the proposed
transfer.

     3.10 Standstill Provisions.  Commencing as of the Closing
and until the  first anniversary of the effective date of the
Company's 34 Act Registration, Purchaser (including all
affiliates or agents of Purchaser) shall not acquire beneficial
ownership of any shares of common stock of the Company, any
securities convertible into or exchangeable for common stock, or
any other right to acquire common stock, except by way of stock
dividends or other distributions to Purchaser as a holder of the
Common Stock generally, from the Company or any other person or
entity, without the prior written consent of the Company, which
consent may be withheld in the Company's sole discretion, if
such acquisition should cause Purchaser (including all
affiliates of Purchaser) to beneficially own more (CONFIDENTIAL
TREATMENT REQUESTED) of the Company's outstanding voting stock
(assuming the full conversion of all convertible securities of
the Company held by Purchaser and its affiliates); provided,
however, that in no event shall (i) the original purchase of the
Common Stock pursuant to this Agreement, (ii) the purchase of
additional shares of Common Stock in lieu of milestone payments
payable pursuant to the License Agreement or (iii) any reduction
in the outstanding shares of the Company's capital stock (or
rights or options), cause a violation of this Section 3.10.  In
order to facilitate Purchaser's compliance with this Section
3.10, upon the written request of Purchaser the Company shall
inform Purchaser of the number of outstanding shares of the
Company's voting stock, and Purchaser may rely on such
information in any purchase it makes within 30 days of the
receipt of such information.

     3.11 Voting Agreement. Purchaser agrees that it shall, so
long as it holds shares of the Company's Common Stock, vote such
shares with respect to any proposed sale of all or substantially
all of the assets, merger, combination or reorganization of the
Company in the same manner as stockholders holding a majority of
the voting securities of the Company and who are not themselves
a party to any such sale, merger, combination or reorganization.
This Section 3.11 shall terminate and shall have no further
force and effect twelve (12) months after the effective date of
the Company's 34 Act Registration.

     3.12 Legends.  It is understood that the certificates
evidencing the Common Stock may bear one or all of the following
legends:

          (a)  "The securities represented by this certificate
have not been registered under the Securities Act of 1933.  They
may not be sold, offered for sale, pledged or hypothecated in
the absence of a registration statement in effect with respect
to the securities under such Act or an opinion of counsel satis
factory to the Company that such registration is not required or
unless sold pursuant to Rule 144 of such Act."

          (b)  "The securities represented by this certificate
are subject to certain rights of first offer and repurchase and
certain restrictions on resale set forth in the Stock Purchase
Agreement dated February 24, 1999 between the Company and
MedImmune, Inc.  A copy of such restrictions and rights of first
offer and repurchase may be obtained from the Company upon
request."

          (c)  Any legend required by the laws of the State of
California or other jurisdiction.

     3.13 Stop-Transfer Instructions.  In order to enforce the
provisions of Sections 3.8 and 3.9 hereof, the Company may
impose stop-transfer instructions with respect to the shares of
the Common Stock held by Purchaser (and the shares or securities
of every other person subject to the foregoing restrictions).

     3.14 Transfers to Affiliates.  Notwithstanding the
provisions of Sections 3.8 and 3.9(b) and (c) hereof, Purchaser
may transfer the Common Stock to any affiliate of Purchaser who
agrees to be bound by the terms of this Agreement.  For purposes
of this Section 3.14, "affiliate" shall mean any entity which
controls or is controlled by Purchaser, and "control" shall mean
ownership of at least (CONFIDENTIAL TREATMENT REQUESTED) of the
voting stock or other ownership interest.

     4.  California Commissioner of Corporations.

     4.1  Corporate Securities Law.  THE SALE OF THE COMMON
STOCK WHICH ARE THE SUBJECT OF THIS AGREEMENT HAS NOT BEEN
QUALIFIED WITH THE COMMISSIONER OF CORPORATIONS OF THE STATE OF
CALIFORNIA AND THE ISSUANCE OF SUCH COMMON STOCK OR THE PAYMENT
OR RECEIPT OF ANY PART OF THE CONSIDERATION THEREFOR PRIOR TO
SUCH QUALIFICATION IS UNLAWFUL, UNLESS THE SALE OF COMMON STOCK
IS EXEMPT FROM QUALIFICATIONS BY SECTION 25100, 25102 OR 25105
OF THE CALIFORNIA CORPORATIONS CODE.  THE RIGHTS OF ALL PARTIES
TO THIS AGREEMENT ARE EXPRESSLY CONDITIONED UPON SUCH
QUALIFICATION BEING OBTAINED, UNLESS THE SALE IS SO EXEMPT.

     5.  Covenants.

     5.1  Delivery of Financial Statements.  The Company shall
deliver to Purchaser such financial statements of the Company
which the Company from time to time distributes to other holders
of the Company's Common Stock, concurrently with such
distribution.

     5.2  Registration Rights.  Purchaser shall have such
registration rights with respect to the Common Stock as are set
forth on EXHIBIT A attached hereto; provided, however, that
Purchaser shall agree to be bound by the provisions of such
EXHIBIT A as a condition precedent to the enjoyment of any such
rights and, at the written request of the Company in connection
with any request by Purchaser to exercise such rights, Purchaser
shall execute a specific acknowledgement and agreement to be so
bound (or else Purchaser shall be deemed to have forfeited such
rights).

     6.  Miscellaneous.

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

     6.2  Governing Law.  This Agreement shall be governed by
and construed under the laws of the State of California
(irrespective of its choice of law principles).

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

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

     6.5  Notices.  Unless otherwise provided, any notice
required or permitted under this Agreement shall be given in
writing and shall be deemed effectively given upon personal
delivery to the party to be notified (or upon the date of
attempted delivery where delivery is refused) or, if sent by
telecopier, telex, telegram, or other facsimile means, upon
receipt of appropriate confirmation of receipt, or upon deposit
with the United States Postal Service, by registered or
certified mail, or next day air courier, with postage and fees
prepaid and addressed to the party entitled to such notice at
the address indicated for such party on the signature page
hereof, or at such other address as such party may designate by
10 days' advance written notice to the other parties to this
Agreement.

     6.6  Finder's Fee.  Each party represents that it neither
is nor will be obligated for any finder's fee or commission in
connection with this transaction.  Purchaser agrees to indemnify
and hold harmless the Company from any liability for any
commission or compensation in the nature of a finder's fee (and
the costs and expenses of defending against such liability or
asserted liability) for which Purchaser or any of its officers,
partners, employees or representatives is responsible.

     The Company agrees to indemnify and hold harmless Purchaser
from any liability for any commission or compensation in the
nature of a finder's fee (and the costs and expenses of
defending against such liability or asserted liability) for
which the Company or any of its officers, employees or
representatives is responsible.

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

     6.8  Severability.  If one or more provisions of this
Agreement are held to be unenforceable under applicable law,
such provision shall be excluded from this Agreement and the
balance of this Agreement shall be interpreted as if such
provision were so excluded and shall be enforceable in accor
dance with its terms.

     6.9  Entire Agreement.  This Agreement and the Related
Agreements embody the entire agreement and understanding of the
parties hereto and thereto in respect of the subject matter
contained herein and therein and supersede all prior agreements
and understandings between the parties with respect to such
subject matter.  No party shall be liable or bound to any other
party in any manner by any warranties, representations or
covenants except as specifically set forth herein or therein.

     IN WITNESS WHEREOF,  the parties have executed this
Agreement as of the date first above written.




     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 Operating     Title: Vice Chairman &
Officer                                 Chief Financial Officer

Source: OneCLE Business Contracts.