<PAGE>

                                                                  EXECUTION COPY





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                                                                   Exhibit 10.20

                               SECURITY AGREEMENT

                          dated as of November 7, 2001


                                      among


                        EAGLEFUNDING CAPITAL CORPORATION
                                   as Conduit,

                             FLEET SECURITIES, INC.
              as Administrator of EagleFunding Capital Corporation,


               FLEET NATIONAL BANK and FIRST UNION NATIONAL BANK,
                             as Liquidity Providers,


       BANCBOSTON LEASING INVESTMENTS INC. and FIRST UNION NATIONAL BANK,
                                  as Investors,


                              FLEET NATIONAL BANK,
                            as Administrative Agent,


                          GENOME STATUTORY TRUST 2001A,
                                    as Lessor

                                       and
                          HUMAN GENOME SCIENCES, INC.,
                                    as Lessee


================================================================================



<PAGE>

                                                                          (HGSI)

                               SECURITY AGREEMENT

        SECURITY AGREEMENT, dated as of November 7, 2001 (this "Security
Agreement"), among EAGLEFUNDING CAPITAL CORPORATION, a Delaware corporation (the
"Conduit"), FLEET SECURITIES, INC. as Administrator of EagleFunding Capital
Corporation, (the "EagleFunding Administrator"), FLEET NATIONAL BANK and FIRST
UNION NATIONAL BANK, as Liquidity Providers (the "Liquidity Providers"),
BANCBOSTON LEASING INVESTMENTS INC. and FIRST UNION NATIONAL BANK as Investors
(the "Investors"), FLEET NATIONAL BANK as administrative agent (the
"Administrative Agent"), Lessor Hedging Agreement Counterparties and GENOME
STATUTORY TRUST 2001A, a Delaware business trust, as lessor (the "Lessor") and
HUMAN GENOME SCIENCES, INC., a Delaware corporation, as lessee and construction
agent (the "Lessee").

        WHEREAS, the Conduit intends from time to time to issue its Commercial
Paper Notes in the United States commercial paper market;

        WHEREAS, the Conduit, the Administrator, the Liquidity Providers and the
Administrative Agent have entered into a Loan Agreement pursuant to which the
Conduit may elect to lend a portion of the net proceeds of its issuance of
Commercial Paper Notes from time to time to Lessor, failing which the Liquidity
Providers have agreed to lend funds to Lessor;

        WHEREAS, pursuant to the Trust Agreement and the Participation
Agreement, the Investors have agreed to make Investor Contributions to the
Lessor;

        WHEREAS, Lessee desires by this Security Agreement and the other
Security Documents to which it is a party, among other things, to provide for
the assignment, pledge and grant of a security interest by Lessee to the
Administrative Agent for the benefit of the Lessor, among other things, in
certain of Lessee's right, title and interest in and to the Lessee Collateral
(as defined below);

        WHEREAS, Lessor desires by this Security Agreement and the other
Security Documents to which it is a party, among other things, to provide for
the assignment, pledge and grant of a security interest by Lessor to the
Administrative Agent for the benefit of the Participants and the Lessor Hedging
Agreement Counterparties, among other things, in certain of the Lessor's right,
title and interest in and to the Participant Collateral (as defined below);

        NOW THEREFORE, the parties hereto agree as follows:

                              GRANTING CLAUSE FIRST

        This Security Agreement secures the payment of all obligations of Lessee
now or hereafter existing under the Participation Agreement, the Lease and each
other Operative Document, whether for principal, interest, costs, fees, expenses
or otherwise, and all other obligations of Lessee, howsoever created, arising or
evidenced, whether direct or indirect, absolute or contingent or now or
hereafter existing or due or to become due under the Operative


<PAGE>

                                                       SECURITY AGREEMENT (HGSI)


Documents (all such obligations and other obligations of Lessee being the
"Secured Lessee Obligations").

        To secure payment and performance of the Secured Lessee Obligations,
Lessee does hereby grant, bargain, sell, assign, transfer, convey, and confirm,
unto the Administrative Agent (on behalf of the Lessor), a security interest in
and lien on all right, title and interest of Lessee in, to and under the Lessee
Collateral.

        It is expressly agreed that anything herein contained to the contrary
notwithstanding, Lessee shall remain liable under the Operative Documents to
which it is party to perform all of the obligations assumed by it thereunder,
all in accordance with and pursuant to the terms and provisions thereof, and
none of Lessor, the Administrative Agent, the Participants or any Lessor Hedging
Agreement Counterparty shall have any obligation or liability under such
Operative Documents by reason of or arising out of the assignment hereunder, nor
shall Lessor, the Administrative Agent, any Participant or any Lessor Hedging
Agreement Counterparty be required or obligated in any manner to perform or
fulfill any obligations of Lessee under or pursuant to such Operative Documents
or, except as herein expressly provided, to make any payment, or to make any
inquiry as to the nature or sufficiency of any payment received by it, or
present or file any claim, or take any action to collect or enforce the payment
of any amounts which may have been assigned to it or to which it may be entitled
at any time or times.

        Upon the occurrence and during the continuance of any Construction
Agency Event of Default or Lease Event of Default, Lessee does hereby
irrevocably constitute the Administrative Agent, on behalf of Lessor, the true
and lawful attorney-in-fact of Lessee, with full power (in the name of Lessee or
otherwise), (i) to ask for, require, demand, and receive, any and all monies and
claims for monies (in each case including insurance and requisition proceeds)
due and to become due under or arising out of the property which now or
hereafter constitutes part of the Lessee Collateral, (ii) to endorse any checks
or other instruments or orders in connection therewith and (iii) to file any
claims or to take any action or to institute any proceedings which Lessor or the
Administrative Agent may deem to be necessary or advisable with respect to the
Lessee Collateral.

                             GRANTING CLAUSE SECOND

        This Security Agreement secures the payment of all obligations of Lessor
now or hereafter existing under the Participation Agreement and each other
Operative Document, whether for principal, interest, costs, fees, expenses or
otherwise, and all other obligations of Lessor to the Participants, the Conduit
and the Lessor Hedging Agreement Counterparties, howsoever created, arising or
evidenced, whether direct or indirect, absolute or contingent or now or
hereafter existing or due or to become due (all such obligations and other
obligations of Lessor being the "Secured Lessor Obligations").

        To secure payment and performance of the Secured Lessor Obligations,
Lessor does hereby grant, bargain, sell, assign, transfer, convey, and confirm,
unto the Administrative Agent (on behalf of the Participants and the Lessor
Hedging Agreement Counterparties), a security



                                       2
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                                                       SECURITY AGREEMENT (HGSI)


interest in and lien on all right, title and interest of Lessor in, to and under
the following described property, rights and privileges, other than Excluded
Amounts and Excepted Rights (which collectively, excluding Excluded Amounts and
Excepted Rights, are hereinafter called the "Participant Collateral" or the
"Collateral"):

                (1)     the Lessee Collateral and all other property pledged to
        the Lessor, or in which the Lessor has been granted a security interest,
        whether pursuant to Granting Clause First above or any other Operative
        Documents or otherwise;

                (2)     all equipment of Lessor, including all parts thereof and
        all accessions, additions, attachments, improvements, substitutions and
        replacements thereto and therefor and all accessories related thereto
        (collectively referred to as the "Equipment");

                (3)     all inventory in all of its forms of Lessor, including
        (a) all raw materials and work in process therefor, finished goods
        thereof, and materials used or consumed in the manufacture or production
        thereof, (b) all goods in which Lessor has an interest in mass or a
        joint or other interest or right of any kind (including goods in which
        Lessor has an interest or right as consignee), and (c) all goods which
        are returned to or repossessed by Lessor, and all accessions thereto,
        products thereof and documents therefor (all of the foregoing
        collectively referred to as the "Inventory");

                (4)     the Participation Agreement and an original executed
        counterpart of the Lease to which a chattel paper receipt is attached,
        including the security interest granted thereunder in favor of Lessor
        and including all rights to receive payments thereunder (including Rent)
        other than Excluded Amounts;

                (5)     the Security Documents, the Material Construction
        Contracts and the other Operative Documents;

                (6)     all accounts, contracts, contract rights, chattel paper,
        documents, instruments, and general intangibles (including tax refunds)
        of Lessor, whether or not arising out of or in connection with the sale
        or lease of goods or the rendering of services, and all rights of Lessor
        now or hereafter existing in and to all security agreements, guaranties,
        leases and other contracts securing or otherwise relating to any such
        accounts, contracts, contract rights, chattel paper, documents,
        instruments, and general intangibles (all of the foregoing collectively
        referred to as the "Receivables", and any and all such security
        agreements, guaranties, leases and other contracts collectively referred
        to as the "Related Contracts");

                (7)     all books, records, writings, databases, information and
        other property relating to, used or useful in connection with,
        evidencing, embodying, incorporating or referring to, any of the
        foregoing (to the extent there are no restrictions at law or contract on
        the assignment contemplated herein);



                                       3
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                                                       SECURITY AGREEMENT (HGSI)


                (8)     all books, records, writings, databases, information and
        other property relating to, used or useful in connection with,
        evidencing, embodying, incorporating or referring to, any of the
        foregoing (to the extent there are no restrictions at law or contract on
        the assignment contemplated herein);

                (9)     all rights to exercise remedies under the Lease (other
        than relating to Excluded Amounts of Excepted Rights); and

                (10)    all products, accessions, rents, issues, profits,
        returns, income and proceeds of and from any and all of the foregoing
        Participant Collateral (including proceeds which constitute property of
        the types described in the foregoing clauses of this Granting Clause
        Second, proceeds deposited from time to time in any lockboxes of Lessor,
        and, to the extent not otherwise included, all payments under insurance
        (whether or not the Administrative Agent is the loss payee thereof), or
        any indemnity, warranty or guaranty payable by reason of loss or damage
        to or otherwise with respect to any of the foregoing Participant
        Collateral).

        Lessor hereby assigns, transfers and conveys to the Administrative Agent
for the benefit of the Participants and the Lessor Hedging Agreement
Counterparties all payments (except Excluded Amounts) payable by Lessee under
the Lease and all amounts payable to it by Construction Agent under the
Construction Agency Agreement.

        It is expressly agreed that anything herein contained to the contrary
notwithstanding, Lessor shall remain liable under the Operative Documents to
which it is party to perform all of the obligations assumed by it thereunder,
all in accordance with and pursuant to the terms and provisions thereof, and
none of the Participants, the Administrative Agent or any Lessor Hedging
Agreement Counterparty shall have any obligation or liability under such
Operative Documents by reason of or arising out of the assignment hereunder, nor
shall the Participants, the Administrative Agent or any Lessor Hedging Agreement
Counterparty be required or obligated in any manner to perform or fulfill any
obligations of Lessor under or pursuant to such Operative Documents or, except
as herein expressly provided, to make any payment, or to make any inquiry as to
the nature or sufficiency of any payment received by it, or present or file any
claim, or take any action to collect or enforce the payment of any amounts which
may have been assigned to it or to which it may be entitled at any time or
times.

        Lessor does hereby irrevocably constitute the Administrative Agent (on
behalf of the Participants and the Lessor Hedging Agreement Counterparties) the
true and lawful attorney-in-fact of Lessor, with full power (in the name of
Lessor or otherwise), other than with respect to Excepted Rights and Excluded
Amounts, (i) to ask for, require, demand, and receive, any and all monies and
claims for monies (in each case including insurance and requisition proceeds)
due and to become due under or arising out of the Operative Documents to which
Lessor is party, and all other property which now or hereafter constitutes part
of the Participant Collateral, (ii) to endorse any checks or other instruments
or orders in connection therewith and (iii) to file any claims or to take any
action or to institute any proceedings which the Participants, the
Administrative Agent or any Lessor Hedging Agreement Counterparty may deem to be



                                       4
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                                                       SECURITY AGREEMENT (HGSI)


necessary or advisable. Under the Lease and the Participation Agreement, Lessee
is directed to make all payments of Rent (other than Excluded Amounts) and all
other amounts which are required to be paid to Lessor pursuant to the Lease
(other than Excluded Amounts) directly to the Administrative Agent in accordance
with the provisions of Article II, for application as provided in this Security
Agreement and the Participation Agreement.

        Concurrently with the delivery hereof, Lessor is delivering to the
Administrative Agent the original executed counterpart of the Lease (to which a
chattel paper receipt is attached) which it received from Lessee.

        Each of Lessee and Lessor agrees that at any time and from time to time,
upon the written request of the Administrative Agent, each of Lessee and Lessor
will promptly and duly execute and deliver or cause to be duly executed and
delivered any and all such further instruments and documents as the
Administrative Agent may reasonably deem necessary in obtaining the full
benefits of the assignment hereunder and of the rights and powers herein
granted.

        Each of Lessee and Lessor hereby warrants and represents that:

        (A)     it has not assigned or pledged, and hereby covenants that it
will not assign or pledge, so long as this Security Agreement shall remain in
effect, any of its right, title or interest hereby assigned, to anyone other
than (i) in the case of Lessee, to the Lessor and the Administrative Agent on
behalf of Lessor, and (ii) in the case of Lessor, to the Participants and the
Lessor Hedging Agreement Counterparties, and the Administrative Agent for the
benefit of Participants and the Lessor Hedging Agreement Counterparties, and

        (B)     Lessor will not, except as provided in this Security Agreement
and any other Operative Documents or except with the consent of the
Administrative Agent, (i) accept any payment from Lessee, (ii) enter into any
agreement amending or supplementing the Lease, the Participation Agreement or
any other Operative Document to which it is party, (iii) execute any waiver or
modification of, or consent under, the terms of, or (except with respect to its
Excluded Amounts and subject to its Excepted Rights) exercise any rights, power
or privileges under, the Lease, the Participation Agreement or any other
Operative Document to which it is party, or (iv) settle or compromise any claim
arising under the Lease or the Participation Agreement.

        Lessor hereby ratifies and confirms each Operative Document to which it
is party and hereby agrees that it will not take or omit to take any action, the
taking or omission of which might result in an alteration or impairment of any
such Operative Document or this Security Agreement or of any of the rights
created by any such document or the assignment hereunder.

        IT IS HEREBY COVENANTED AND AGREED by and between the parties hereto as
follows:



                                       5
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                                                       SECURITY AGREEMENT (HGSI)


                                   ARTICLE I

             DEFINITIONS; APPOINTMENT OF ADMINISTRATIVE AGENT, ETC.

        SECTION 1.01    Definitions. Unless otherwise defined herein,
capitalized terms shall have the meaning ascribed to them in Appendix A to the
Participation Agreement, dated as of even date herewith, among the Lessor, the
Lessee, the Investors, the Administrative Agent, the Liquidity Agent, the
Conduit, the Administrator, the Liquidity Providers and Wells Fargo Bank,
Northwest, N.A., as trustee for the Lessor and the rules of usage set forth
therein shall apply hereto.

        SECTION 1.02    Appointment of Administrative Agent, etc. (a) Each of
the Lessor, and the Participants hereby appoints Fleet National Bank as the
Administrative Agent and hereby presently transfers to the Administrative Agent
all rights of the Lessor, the Participants and the Lessor Hedging Agreement
Counterparties under this Security Agreement, including all right, title and
interest of Lessee or Lessor in and to the applicable Collateral (including all
payments payable by Lessee under the Lease), except for Excluded Amounts and
Excepted Rights. The parties agree that the Administrative Agent is holding the
original executed counterpart of the Lease, as bailee pursuant to Section 9-313
of the UCC. The Administrative Agent acknowledges that it has been notified of
the security interests granted in this Security Agreement in the original
executed counterpart of the Lease. Proceeds of the Collateral shall be
distributed by the Administrative Agent in accordance with Article X of the
Participation Agreement.

        (b)     Lessee hereby acknowledges such appointment and the transfer of
rights of the Lessor to the Administrative Agent under this Security Agreement.
Lessor hereby acknowledges such appointment and the transfer of rights of the
Participants to the Administrative Agent under this Security Agreement.

                                   ARTICLE II

                                 RENT PAYMENTS

        SECTION 2.01    Payment of Rent and Other Amounts. Pursuant to this
Security Agreement, all of the payments (other than Excluded Amounts) made by
Lessee under the Operative Documents have been assigned to the Administrative
Agent. Lessee shall pay or cause to be paid each installment of the Base Rent,
Supplemental Rent, and other amounts payable under the Lease and the Operative
Documents, (excluding, in each case, Excluded Amounts and subject, in each case,
to Excepted Rights) to the Administrative Agent. At the appropriate times, the
Conduit and Lessor shall instruct all other Persons who may come to owe to the
Participants, the Lessor Hedging Agreement Counterparties or Lessor amounts
pursuant to the Lease or any other Operative Document to pay such amounts
(excluding, in each case, Excluded Amounts and subject, in each case, to
Excepted Rights) and each of the Participants and Lessor shall use reasonable
efforts to cause all such Persons to make all such payments to the
Administrative Agent.



                                       6
<PAGE>

                                                       SECURITY AGREEMENT (HGSI)


        SECTION 2.02    Payments from Collateral Only. Without impairing any of
the other rights, powers, privileges, liens or security interests of the
Participants, the Lessor Hedging Agreement Counterparties or the Administrative
Agent under this Security Agreement or any other Operative Document, each
Participant and the Lessor Hedging Agreement Counterparties agree that, except
as expressly provided in this Security Agreement, the Trust Agreement, the Loan
Agreement, the Participation Agreement, the Liquidity Agreement or any other
Operative Document, (i) the obligation of Lessor to make all payments under the
Lease, and the performance by Lessor of every obligation or covenant contained
in this Security Agreement, the Participation Agreement, or any of the other
Operative Documents, shall be payable only from the income and proceeds of
Lessor to the extent included in the Participant Collateral or any other
collateral pledged by Lessor under the Security Documents and only to the extent
that Lessor shall have sufficient income or proceeds to the extent included in
the Participant Collateral to enable the Administrative Agent to make such
payments in accordance with the terms of Article X of the Participation
Agreement, and all of the statements, representations, covenants and agreements
made by Lessor contained in this Security Agreement and any agreement referred
to herein, unless expressly otherwise stated, are made and intended only for the
purpose of binding Lessor and establishing the existence of rights and remedies
which can be exercised and enforced against Lessor; therefore, anything
contained in this Security Agreement or such other agreements to the contrary
notwithstanding, no recourse shall be had with respect to this Security
Agreement or such other Operative Documents against Lessor, except to the extent
of such Participant Collateral, or against any officer, director, trustee,
servant, partner, member or direct or indirect parent or controlling person or
persons of Lessor; and (ii) none of Lessor or the Administrative Agent shall
have any personal liability for any amounts payable hereunder, under the
Participation Agreement or any of the other Operative Documents (except, in the
case of Lessor, to the extent of such Participant Collateral); provided,
however, that this Section 2.02 shall not be construed to prohibit any action or
proceeding against any party hereto for its own willful misconduct, gross
negligence, bad faith or criminal conduct for which it would otherwise be liable
(but only to the extent of the damages arising by reason thereof). Lessor hereby
acknowledges that the Administrative Agent has expressly reserved all its legal
rights and remedies against the Participant Collateral granted by Lessor,
including, without limitation of the generality of the foregoing, the right, in
the event of any payment due and unpaid from Lessor under the Loan Agreement, to
foreclose upon this Security Agreement and/or to receive the proceeds from the
Participant Collateral and otherwise to enforce any other right under this
Security Agreement.

                                   ARTICLE III

                      RECEIPT, DISTRIBUTION AND APPLICATION
                          OF INCOME FROM THE COLLATERAL

        SECTION 3.01    Distribution. Distributions of payments and collateral
proceeds shall be distributed in the manner set forth in Article X of the
Participation Agreement.



                                       7
<PAGE>

                                                       SECURITY AGREEMENT (HGSI)


                                   ARTICLE IV

             REMEDIES OF ADMINISTRATIVE AGENT UPON EVENT OF DEFAULT

        SECTION 4.01    Remedies Upon Default. If any Lease Event of Default or
Construction Agency Event of Default shall have occurred and be continuing the
Administrative Agent may exercise in respect of the Collateral, in addition to
other rights and remedies provided for herein or otherwise available to it, all
the rights and remedies of a secured party under the UCC (whether or not the UCC
applies to the Collateral at issue), and the Administrative Agent may also,
without notice except as specified below, sell the Collateral or any part
thereof in one or more parcels at public or private sale, or at any of the
Administrative Agent's offices or elsewhere, for cash, on credit or for future
delivery, and upon such other terms as the Administrative Agent may deem
commercially reasonable. Lessor agrees that, to the extent notice of sale shall
be required by law, at least ten days' notice to Lessor of the time and place of
any public sale or the time after which a private sale is to be made shall
constitute reasonable notification. The Administrative Agent shall not be
obligated to make any sale of Collateral regardless of notice of sale having
been given. The Administrative Agent may adjourn any public or private sale from
time to time by announcement at the time and place fixed therefore and such sale
may, without further notice, be made at the time and place to which it was so
adjourned. The Administrative Agent shall be entitled to consult with legal
counsel and financial advisors in connection with the sale of the Collateral and
shall be protected in any reasonable action or forbearance taken in connection
with the advice of such counsel or advisors.

        SECTION 4.02    Remedies Cumulative. Each and every right, power and
remedy given to the Administrative Agent specifically or otherwise in this
Security Agreement shall be cumulative and shall be in addition to every other
right, power and remedy herein specifically given or now or hereafter existing
at law, or under the UCC, or otherwise in equity or by statute, and each and
every right, power and remedy whether specifically herein given or otherwise
existing may be exercised from time to time and as often and in such order as
may be deemed expedient by the Administrative Agent, and the exercise or the
beginning of the exercise of any power or remedy shall not be construed to be a
waiver of the right to exercise at the same time or thereafter any other right,
power or remedy. No delay or omission by the Administrative Agent in the
exercise of any right, remedy or power or in the pursuance of any remedy shall
impair any such right, power or remedy or be construed to be a waiver of any
default on the part of Lessor or Lessee or to be an acquiescence therein.

        SECTION 4.03    Discontinuance of Proceedings. In case the
Administrative Agent shall have instituted any proceeding to enforce any right,
power or remedy under this Security Agreement by foreclosure, entry or
otherwise, and such proceedings shall have been discontinued or abandoned for
any reason or shall have been determined adversely to the Administrative Agent,
then and in every such case the Participants, the Lessor Hedging Agreement
Counterparties, the Administrative Agent, Lessee and Lessor shall, subject to
any determination in such proceedings, be restored to their former positions and
rights hereunder with respect to the Collateral, and all rights, remedies and
powers of the Administrative Agent shall continue as if no such proceedings had
been instituted.



                                       8
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                                                       SECURITY AGREEMENT (HGSI)


                                   ARTICLE V

                  THE PARTICIPANTS AND THE ADMINISTRATIVE AGENT

        SECTION 5.01    No Representations or Warranties as to Property or
Documents. NONE OF THE PARTICIPANTS, THE LESSOR HEDGING AGREEMENT
COUNTERPARTIES, OR LESSOR MAKES OR SHALL BE DEEMED TO HAVE MADE ANY
REPRESENTATION OR WARRANTY, EXPRESS OR IMPLIED, AS TO THE TITLE, VALUE,
COMPLIANCE WITH SPECIFICATIONS, CONDITION, DESIGN, QUALITY, DURABILITY,
OPERATION, MERCHANTABILITY OR FITNESS FOR USE OR PURPOSE OF ANY PROPERTY, OR ANY
OTHER REPRESENTATION OR WARRANTY WITH RESPECT TO ANY PROPERTY WHATSOEVER. None
of the Participants, the Lessor Hedging Agreement Counterparties, or Lessor
makes or shall be deemed to have made any representations or warranty as to the
validity, legality or enforceability of this Security Agreement, the Loan
Agreements, the Notes, the Participation Agreement, the Lease or any other
Operative Document as to the correctness of any statement contained in any
thereof, except for the representations and warranties of Lessor made in Section
5.3 of the Participation Agreement. The Administrative Agent makes no
representation or warranty hereunder whatsoever.

        SECTION 5.02    Loss of Principal or Interest. The Administrative Agent
shall not be liable for any loss of principal or interest resulting from a
Permitted Investment, provided, that any payments received or applied hereunder
by the Administrative Agent shall be accounted for by the Administrative Agent
so that any portion thereof paid or applied pursuant hereto shall be
identifiable as to the source thereof.

        SECTION 5.03    Reliance; Administrative Agent; Advice of Counsel. The
Administrative Agent shall not incur any liability to anyone in acting upon any
signature, instrument, notice, resolution, request, consent, order, certificate,
report, opinion, bond or other document or paper believed by it to be genuine
and believed by it to be signed by the proper party or parties. The
Administrative Agent may accept a copy of a resolution of the board of directors
or general manager of any party to the Participation Agreement, certified by the
Secretary or an Assistant Secretary thereof as duly adopted and in full force
and effect, as conclusive evidence that such resolution has been duly adopted
and that the same is in full force and effect. As to any fact or matter relating
to Lessee or Lessor the manner of ascertainment of which is not specifically
described herein, the Participants, the Lessor Hedging Agreement Counterparties,
or the Administrative Agent may for all purposes hereof rely on a certificate,
signed by a duly authorized officer of Lessee or Lessor, as to such fact or
matter, and such certificate shall constitute full protection to the
Participants, the Lessor Hedging Agreement Counterparties, or the Administrative
Agent for any action taken or omitted to be taken by them in good faith in
reliance thereon.



                                       9
<PAGE>

                                                       SECURITY AGREEMENT (HGSI)


                                   ARTICLE VI

                                  MISCELLANEOUS

        SECTION 6.01    Termination of Security Agreement. This Security
Agreement shall remain in full force and effect until payment in full of the
Lease Balance and all other amounts due and payable by the Lessee under the
Operative Documents and the termination of the Commitments of the Participants,
provided, however, that this Security Agreement and the security interests
created hereby shall earlier terminate and this Security Agreement shall be of
no further force or effect upon any sale or other final disposition by the
Administrative Agent of all of the property constituting the Collateral and the
final distribution by the Administrative Agent of all monies or other property
or proceeds constituting the Collateral in accordance with the terms hereof.
Upon such termination of this Security Agreement, the Participants shall direct
the Administrative Agent to execute and deliver to or as directed in writing by
the Lessor, an appropriate instrument terminating this Security Agreement and
releasing Collateral from the assignment and pledge thereof hereunder, and the
Administrative Agent shall execute and deliver such instrument as aforesaid.
Except as aforesaid otherwise provided, this Security Agreement and the security
interests created hereby shall continue in full force and effect in accordance
with the terms hereof.

        SECTION 6.02    Sale of Collateral by Administrative Agent Is Binding.
Any sale or other conveyance of any Lessee Collateral or the Participant
Collateral by the Administrative Agent made pursuant to the terms of this
Security Agreement or the Lease shall be effective to transfer or convey all
right, title and interest of the Lessee or Lessor, as applicable, in and to such
Collateral. No purchaser or other grantee shall be required to inquire as to the
authorization, necessity, expediency or regularity of such sale or conveyance or
as to the application of any sale or other proceeds with respect thereto by the
Administrative Agent.

        SECTION 6.03    Security Agreement for Benefit of the Lessor,
Participants, Lessor Hedging Agreement Counterparties and the Administrative
Agent. Except as provided by Applicable Law or otherwise expressly provided in
the Operative Documents, nothing in this Security Agreement, whether express or
implied, shall be construed to give any legal or equitable right, remedy or
claim under or in respect of this Security Agreement to any Person other than
Lessor, the Participants, the Administrative Agent and the Lessor Hedging
Agreement Counterparties.

        SECTION 6.04    Notices. All notices, demands, requests, consents,
approvals and other instruments under this Security Agreement shall be made in
accordance with the notice provisions of the Participation Agreement.

        SECTION 6.05    Severability. Any provision of this Security Agreement
which is prohibited or unenforceable in any jurisdiction, shall, as to such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof, and any
such prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction.



                                       10
<PAGE>

                                                       SECURITY AGREEMENT (HGSI)


        SECTION 6.06    No Oral Modification or Continuing Waivers. No term or
provision of this Security Agreement may be changed, waived, discharged or
terminated orally, but only by an instrument in writing signed by the party or
other person against whom enforcement of the change, waiver, discharge or
termination is sought and then only in accordance with Section 12.5 of the
Participation Agreement.

        SECTION 6.07    Successors and Assigns. All covenants and agreements
contained herein shall be binding upon, and inure to the benefit of, each of the
parties hereto and the successors and assigns of each, all as herein provided.

        SECTION 6.08    Headings. The headings of the various Articles and
Sections herein and in the table of contents hereto are for convenience of
reference only and shall not define or limit any of the terms or provisions
hereof.

        SECTION 6.09    Governing Law; Counterpart Form. This Security Agreement
and the rights and obligations of the parties under this Security Agreement
shall be governed by, and construed and interpreted in accordance with, the laws
of the State of New York, including Section 5-1401 of the New York General
Obligations Law, but excluding to the maximum extent permitted by Applicable Law
all other conflicts of law principles and choice of law rules of New York. This
Security Agreement may be executed by the parties hereto in separate
counterparts, each of which when so executed and delivered shall be an original,
but all such counterparts shall together constitute but one and the same
instrument.

        SECTION 6.10    Continuing Security Interest. This Security Agreement
creates a continuing security interest in the Collateral.

                                  [End of Page]

                            [Signature Pages Follow]




                                       11
<PAGE>

                                                       SECURITY AGREEMENT (HGSI)


        IN WITNESS WHEREOF, the parties hereto have caused this SECURITY
AGREEMENT to be duly executed by their respective officers thereunto duly
authorized, as of the day and year first above written.


                                      EAGLEFUNDING CAPITAL CORPORATION



                                      By: /s/ THOMAS M. CALHOUN
                                          ----------------------------------
                                          Name:  Thomas M. Calhoun
                                          Title: Director, its
                                                 attorney-in-fact




<PAGE>

                                                       SECURITY AGREEMENT (HGSI)






                                      FLEET SECURITIES, INC.



                                      By: /s/ THOMAS M. CALHOUN
                                          ----------------------------------
                                          Name:  Thomas M. Calhoun
                                          Title: Director




<PAGE>

                                                       SECURITY AGREEMENT (HGSI)









                                      FLEET NATIONAL BANK, as Liquidity Provider



                                      By:  /s/ THOMAS W. DAVIES
                                          ----------------------------------
                                          Name:  Thomas W. Davies
                                          Title: Managing Director




<PAGE>

                                                       SECURITY AGREEMENT (HGSI)






                                      FIRST UNION NATIONAL BANK, as Liquidity
                                      Provider



                                      By: /s/ BARBARA K. ANGEL
                                          ----------------------------------
                                          Name:  Barbara Kaufmann Angel
                                          Title: Vice President







<PAGE>

                                                       SECURITY AGREEMENT (HGSI)






                                      BANCBOSTON LEASING INVESTMENTS INC.,
                                      as Investor



                                      By:  /s/ STEVEN CRISCIONE
                                          ----------------------------------
                                          Name:  Steven Criscione
                                          Title: Vice President




<PAGE>

                                                       SECURITY AGREEMENT (HGSI)






                                      FIRST UNION NATIONAL BANK, as Investor



                                      By: /s/ BARBARA K. ANGEL
                                          ----------------------------------
                                          Name:  Barbara Kaufmann Angel
                                          Title: Vice President


<PAGE>

                                                       SECURITY AGREEMENT (HGSI)






                                      FLEET NATIONAL BANK, as Administrative
                                      Agent



                                      By: /s/ THOMAS W. DAVIES
                                          ----------------------------------
                                          Name:  Thomas W. Davies
                                          Title: Managing Director




<PAGE>

                                                       SECURITY AGREEMENT (HGSI)







                                      GENOME STATUTORY TRUST 2001A, as Lessor



                                      By:  /s/ C. SCOTT NIELSON
                                          ----------------------------------
                                          Name:  C. Scott Nielson
                                          Title: Vice President




<PAGE>

                                                       SECURITY AGREEMENT (HGSI)






                                      HUMAN GENOME SCIENCES, INC., as Lessee



                                      By: /s/ STEVEN C. MAYER
                                          ----------------------------------
                                          Name:  Steven C. Mayer
                                          Title: Senior Vice President and CFO




<PAGE>



                                TABLE OF CONTENTS


<TABLE>
<CAPTION>
                                                                                                         PAGE
<S>                                                                                                     <C>

ARTICLE I    DEFINITIONS; APPOINTMENT OF ADMINISTRATIVE AGENT, ETC.........................................6

     SECTION 1.01    Definitions...........................................................................6
     SECTION 1.02    Appointment of Administrative Agent, etc..............................................6

ARTICLE II   RENT PAYMENTS.................................................................................6

     SECTION 2.01    Payment of Rent and Other Amounts.....................................................6
     SECTION 2.02    Payments from Collateral Only.........................................................7

ARTICLE III  RECEIPT, DISTRIBUTION AND APPLICATION OF INCOME FROM THE COLLATERAL...........................7

     SECTION 3.01    Distribution..........................................................................7

ARTICLE IV   REMEDIES OF ADMINISTRATIVE AGENT UPON EVENT OF DEFAULT........................................8

     SECTION 4.01    Remedies Upon Default.................................................................8
     SECTION 4.02    Remedies Cumulative...................................................................8
     SECTION 4.03    Discontinuance of Proceedings.........................................................8

ARTICLE V    THE PARTICIPANTS AND THE ADMINISTRATIVE AGENT.................................................9

     SECTION 5.01    No Representations or Warranties as to Property or Documents..........................9
     SECTION 5.02    Loss of Principal or Interest.........................................................9
     SECTION 5.03    Reliance; Administrative Agent; Advice of Counsel.....................................9

ARTICLE VI   MISCELLANEOUS................................................................................10

     SECTION 6.01    Termination of Security Agreement....................................................10
     SECTION 6.02    Sale of Collateral by Administrative Agent Is Binding................................10
     SECTION 6.03    Security Agreement for Benefit of the Lessor, Participants,
                     Lessor Hedging Agreement Counterparties and the Administrative Agent.................10
     SECTION 6.04    Notices..............................................................................10
     SECTION 6.05    Severability.........................................................................10
     SECTION 6.06    No Oral Modification or Continuing Waivers...........................................11
     SECTION 6.07    Successors and Assigns...............................................................11
     SECTION 6.08    Headings.............................................................................11
     SECTION 6.09    Governing Law; Counterpart Form......................................................11
     SECTION 6.10    Continuing Security Interest.........................................................11
</TABLE>



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