<PAGE>


                                                                   EXHIBIT 10.10

                                LEASE AGREEMENT


IN CONSIDERATION OF the mutual covenants and agreements herein stated, the
INSTITUTE OF GAS TECHNOLOGY, an Illinois corporation having its principal
offices at 1700 South Mount Prospect Road, Des Plaines, Illinois, 60018
(hereinafter called "IGT") agrees to lease to MediChem Research Inc. an Illinois
corporation with principal offices at 1700 South Mount Prospect Road, Des
Plaines, Illinois, 60018 (hereinafter called "Tenant") the rooms of IGT's
Building listed in Exhibit A attached hereto and made a part hereof under the
following terms and conditions:

     1.  Term of Agreement
         -----------------

         The term of this Agreement shall be one (1) year beginning 12:01 a.m.
         October 1, 1997, and ending 12:00 midnight September 30, 1998.

     2.  Compensation
         ------------

         During the first year of this Agreement, Tenant shall pay a total
         rental amount of Eighty One Thousand Dollars ($81,000) for the use of
         rooms listed in Exhibit A, said amount to be paid monthly in advance in
         equal installments of Six Thousand Seven Hundred Fifty Dollars
         ($6,750.00) by Tenant to IGT. The above rent amount was calculated by
         multiplying the total room square footage from Exhibit A, by a base
         rental rate of $15 per square foot.

         The above rental rate includes a $2/ square foot estimated allocation
         for property taxes. Upon receipt by IGT of the actual tax bill for the
         term of the lease for the leased space, IGT will either bill the
         overage to tenant, or credit the amount over collected to the tenant.

         Tenant shall pay the equivalent of one months rent as a deposit. Said
         deposit is due and payable to IGT upon signing of the lease and will be
         returned upon vacating the building in satisfactory condition.

         The Tenant will not be responsible for any charge for depreciation
         should the building be sold.

         Tenant has option to renew lease at a fixed annual increase of 3% for
         either a one or three year period. Tenant will advise of execution of
         the option 3 months prior to termination of lease.

     3.  Late Charges and Interest on Past Due Obligations
         -------------------------------------------------

         Tenant's failure to pay rent promptly may cause IGT to incur
         unanticipated costs. The exact amount of such costs are impractical or
         extremely difficult to ascertain. Such costs may include, but are not
         limited to, processing and accounting charges and late charges which
         may be imposed on IGT by any ground lease, mortgage or trust deed
         encumbering the Property. Therefore, if IGT does not receive any rent
         payment within ten (10) days after it becomes due, Tenant shall pay IGT
         a late
<PAGE>

         charge equal to ten percent (10%) of the overdue amount. The parties
         agree that such late charge represents a fair and reasonable estimate
         of the costs IGT will incur by reason of such late payment.

         Any amount owed by Tenant to IGT which is not paid when due shall bear
         interest at the rate of fifteen percent (15%) per annum from the due
         date of such amount. However, interest shall not be payable on late
         charges to be paid by Tenant under this Lease. The payment of interest
         on such amounts shall not excuse or cure any default by Tenant under
         this Lease. If the interest rate specified in this lease is higher than
         the rate permitted by law, the interest rate is hereby decreased to the
         maximum legal interest rate permitted by law.

     4.  Use of Property
         ---------------

     A.  Tenant shall use property only for laboratory research consisting of
         chemical organic synthesis and associated business activities. Tenant
         shall not cause or permit the Property to be used in any way which
         constitutes a violation of any local, State of Illinois or Federal law,
         ordinance, or governmental regulation or order, which annoys or
         interferes with the rights of Tenants of the building, or which
         constitutes a nuisance or waste.

         Tenant shall promptly take all actions necessary to comply with all
         applicable local, State of Illinois and Federal statutes, ordinances,
         rules, regulations, orders and requirements regulating the use by
         Tenant of the Property, including the Occupational Safety and Health
         Act.

     B.  As used in this Lease, the term "Hazardous Material" means any
         flammable items, hazardous or toxic substances, material or waste or
         related materials, including any substances defined as or included in
         the definition of "hazardous substances", "Hazardous wastes",
         "Hazardous materials" or toxic substances" now or subsequently
         regulated under any applicable federal, state or local laws or
         regulations, including without limitation petroleum-based products,
         solvents, cyanide, acids, pesticides, ammonia compounds and other
         chemical products, and similar compounds, and including any different
         products and materials which are subsequently found to have adverse
         effects on the environment or the health and safety of persons. Tenant
         agrees that any Hazardous Material generated, produced, brought upon,
         used, stored, or treated in or about the property by Tenant, its
         agents, employees, contractors, subleases or invitees will be handled
         in a reasonable and safe manner pursuant to the laws and regulations
         contained in paragraph 4a above. IGT will not refuse any reasonable and
         accepted safe use of such hazardous chemicals. IGT shall be entitled to
         take into account such other factors or facts as IGT may reasonably
         determine to be relevant in determining whether to grant or withhold
         consent to Tenant's proposed activity with respect to Hazardous
         Material. In no event, however, shall IGT be required to consent to the
         installation or use of any storage tanks on the Property. In order to
         monitor the hazardous materials, IGT will have access to the MSDS
         declarations in held in
<PAGE>

         each company. A standard statement of the use and operations of the
         laboratory will be posted at each laboratory entrance.

     5.  Assignment
         ----------

         Tenant shall not assign this Agreement nor permit by any act or default
         any transfer of Tenant's interests by operation of law, nor offer the
         premises or any part thereof for lease or sublease, nor permit the use
         thereof for any purpose other than as above mentioned, without, in each
         case, the written consent of IGT. This lease will inure to the benefit
         of the successors and assigns of both IGT and the Tenant.

     6.  Surrender of Premises
         ---------------------

         Tenant shall surrender the premises at the end of the term or upon
         termination of the Agreement in as good condition as reasonable and
         fair wear and tear use thereof will permit, with all keys thereto, and
         shall not make any alterations to the premises without the written
         consent of IGT; and all alterations which may be made by either party
         hereto upon the premises, except movable furniture and fixtures put in
         at the expense of Tenant, shall be the property of IGT, and shall
         remain upon and be surrendered with the premises as a part thereof at
         the termination of this Agreement.

     7.  IGT Not Liable
         --------------

         IGT shall not be liable for any loss of property or defects in the
         building or in the premises, or any accidental damages to the personal
         property of Tenant in or about the building or the premises, from
         water, rain or snow which may leak into, issue or flow from any part of
         the building or premises, or from the pipes or plumbing, works of the
         same. In addition, IGT shall not be liable to Tenant for any damages or
         injury to personal property of Tenant or for bodily harm or injury to
         any individual arising out of Tenant's use of the premises pursuant to
         this Agreement.

     8.  Indemnity
         ---------

         Tenant shall indemnify IGT against and hold IGT harmless from any and
         all costs, claims or liability arising from: (a) Tenant's use of the
         Property; (b) the conduct of Tenant's business or anything else done or
         permitted by Tenant to be done in or about the Property, including any
         contamination of the Property or any other property resulting from the
         presence or use of Hazardous Material caused or permitted by Tenant;
         (c) any breach or default in the performance of Tenant's obligations
         under this Lease; (d) any misrepresentation or breach of warranty by
         Tenant under this Lease; or (e) other acts or omissions of Tenant.
         Tenant shall defend IGT against any such cost, claim or liability at
         Tenant's expense with counsel reasonable acceptable to IGT or, at IGT's
         election, Tenant shall reimburse IGT for any legal fees or costs
         incurred by IGT in connection with any such claim. As a material part
         of the consideration to IGT, Tenant assumes all risk of
<PAGE>

         damage to property or injury to persons in or about the Property
         arising from any cause, and Tenant hereby waives all claims in respect
         thereof against IGT, except for any claim arising out of IGT's gross
         negligence or willful misconduct. As used in this Section, the term
         "Tenant" shall include Tenant's employees, agents, contractors and
         invitees, if applicable.

     9.  Signs and Auctions
         ------------------

         Tenant shall not place any signs on the Property without IGT's prior
         written consent. Tenant shall not conduct or permit any auctions or
         sheriff's sales at the Property, Adequate and agreeable signage shall
         be provided by IGT at the entrance to the site, the entrance to the
         building and in the interior of the building such that the location of
         the Tenant space can be easily determined. The nature and consistency
         of the signage will be determined jointly by IGT and the Tenant.

     10. Services to be Provided by IGT
         ------------------------------

         IGT shall provide the following services to Tenant at no additional
         expense to Tenant:

         (1)  Heat and air conditioning equal to that provided to the remainder
              of IGT's building. Excessive usage beyond normal laboratory usage
              will be billed to Tenant.

         (2)  Electricity equal to that provided to the rest of IGT's building.
              Excessive usage beyond normal laboratory usage will be billed to
              Tenant.

         (3)  Janitorial service.

         (4)  Water and sewer connections.

         (5)  natural gas, and compressed air distributed to existing outlet in
              the laboratories.

         (6)  uncharged access to lunch room facilities and parking spaces for
              employees and visitors.

         (7)  24 hour access to the laboratories



     11. Landlord's Remedies
         -------------------

     If, within five (5) days after notice from IGT, default be made in the
     payment of any installment of rent or any other monies due hereunder, IGT
     may terminate this Agreement. Upon such termination, IGT may re-enter the
     premises and remove all persons, fixtures and chattels therefrom. Upon such
     repossession of the premises, IGT shall attempt to relet the premises (or
     so much thereof as IGT shall not require for its own purposes) for such
     rent and for such terms as shall be satisfactory to IGT (including the
     right to relet the premises for a term greater or lesser than remaining
     under this
<PAGE>

     Agreement and the right to change the character or use made of the
     premises). For the purposes of such reletting, IGT may decorate and make
     any repairs, changes, alterations or additions in or to the premises that
     may be necessary to accomplish such reletting. Tenant shall also pay to
     IGT, as liquidated damages and not as a penalty, (i) if IGT fails to relet
     the premises, the present value of the rent which Tenant would have paid
     for the remainder of the term or (ii) if IGT relets the premises, the
     present value of the amount by which the rent which Tenant would have paid
     for the remainder of the term exceeds the rent to be received from such
     reletting during such period. The discount rate used to determine such
     present value shall be the current six (6) month treasury bill rate.

     12.  Telephone Service
          -----------------

          Tenant shall have the right to install telephone equipment at its
          expense and shall have access to other parts of IGT's building for
          such purpose.

     13.  Building Security
          -----------------

          Tenant shall require all of its employees and guests to obey the
          security regulations of IGT. IGT shall give copies of such regulations
          and changes in such regulations to Tenant for distribution to its
          employees. IGT security and reception personnel shall admit Tenant
          employees and guests to the premises and shall provide identification
          cards for such employees and guests.

     14.  Insurance
          ---------

          During the Lease Term, Tenant shall maintain a policy of commercial
          general liability insurance (sometimes known as broad form
          comprehensive general liability insurance) insuring Tenant against
          liability for bodily injury, property damage (including loss of use of
          property) and personal injury arising out of the operation, use or
          occupancy of the Property. Tenant shall name IGT as an additional
          insured under such policy. The initial amount of such insurance shall
          be One Million Dollars ($1,000,000) per occurrence and shall be
          subject to periodic increase based upon inflation, increased liability
          awards, recommendation of IGT's professional insurance advisers and
          other relevant factors. The liability insurance obtained by Tenant
          under this Paragraph shall (i) be primary and noncontributing; (ii)
          contain cross-liability endorsements; and (iii) insure IGT against
          Tenant's performance under Section 8, if the matters giving rise to
          the indemnity under Section 8 result from the negligence of Tenant.
          The amount and coverage of such insurance shall not limit Tenant's
          liability nor relieve Tenant of any other obligation under this Lease.
          IGT may also obtain comprehensive public liability insurance in an
          amount and with coverage determined by IGT insuring IGT against
          liability arising out of ownership, operation, use or occupancy of the
          Property. The policy obtained by IGT shall not be contributory and
          shall not provide primary insurance. Prior to occupancy, Tenant shall
          provide a certificate of insurance to IGT demonstrating the existence
          of the above referenced coverage.
<PAGE>

     15.  IGT's Access
          ------------

          IGT or its agents may enter the Property at all reasonable times
          during normal business hours to show the Property to potential buyers,
          investors or Tenants or other parties; to do any other act or to
          inspect and conduct tests in order to monitor Tenant's compliance with
          all applicable environmental laws and all laws governing the presence
          and use of Hazardous Material; or for any other purpose IGT deems
          necessary. IGT shall give Tenant prior notice of such entry two
          business days in advance, except in the case of an emergency. IGT may
          place customary "For Sale" or "For Lease" signs on the property.

     16.  Adjudication
          ------------

          This lease will be govern by the laws of the State of Illinois and any
          adjudication will be in the Courts of the State of Illinois.

     17.  Employment
          ----------

          Tenant, its owners and officers, or any company owned or controlled by
          any of the aforementioned will not employ, offer compensation to, or
          contract to provide future compensation to any IGT employee or former
          IGT employee for a period of two years from the date of termination of
          employment with IGT without the prior written approval of the
          President of IGT.


IN WITNESS WHEREOF, the parties hereto have caused their hands and seals to be
affixed to the aforegoing instrument on the date first written above.



INSTITUTE OF GAS TECHNOLOGY                MEDICHEM RESEARCH INC.

By:___________________________________     By:_________________________________

Name:_________________________________     Name:_______________________________

Title:________________________________     Title:______________________________

Date:_________________________________     Date:_______________________________
<PAGE>

                                   EXHIBIT A


     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois. Both IGT
and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number
which may or may not represent actual square footage.

Room No.                  Estm. Square Footage
-------                   --------------------

607-613                   5,400
<PAGE>

                            SECRETARY'S CERTIFICATE


INSERT FORMS 1 THRU 6 HERE
<PAGE>

                         Lease Guaranty PAGES 1 THRU 3


INSERT FORMS 1 THRU 3 HERE
<PAGE>

             PREPAYMENT RIDER TO EQUIPMENT LEASE DATED _____, 1996
                  BETWEEN MEDICHEM RESEARCH, INC., AS LESSEE
            AND THE CIT GROUP/EQUIPMENT FINANCING, INC., AS LESSOR

1)   Lessee shall have the right to prepay the amount due under the Equipment
Lease, (Lease) in whole but not in part, at any time during the term of the
Lease, provided that Lessee gives Lessor at least 30 days prior written notice
of its intention to prepay and in addition to the payment of all principal,
accrued interest, late charges and other amounts due under the Lease, Lessor
pays a prepayment fee equal to:

     a)  There shall be no prepayment penalty if such prepayment occurs during
         the first year

     b)  Four percent (4%) of the amount prepaid if such prepayment occurs
         during the second year

     c)  Three percent (3%) of the amount prepaid if such prepayment occurs
         during the third year

     d)  Two percent (2%) of the amount prepaid if such prepayment occurs during
         the fourth year

     e)  One percent (1%) of the amount prepaid if such prepayment occurs during
         the fifth year

2)   Each year shall mean a period of twelve (12) consecutive months. The first
year shall commence September ____, 1996. Subsequent years shall run
consecutively, each commencing on the anniversary of the first year.

3)   In the event of prepayment, the method used to calculate the unpaid balance
will be used based on a Simple Interest Method,

Lessee:  MEDICHEM RESEARCH, INC.         Lessor: THE CIT GROUP/EQUIP. FIN., INC.


By: __________________________________   By: __________________________________

Title: _______________________________   Title: _______________________________
<PAGE>

                     Delivery and Installation Certificate


INSERT A FORM HERE
<PAGE>

                                  EXHIBIT A1-1

     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois. Both IGT
and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number
which may or may not represent actual square footage.


          Room No.                     Estm. Square Footage
          --------                     --------------------

          607-613                             5,400

          622                                   485

<PAGE>

                                                                   July 21, 1998

Ms. Nancy A. Tryrrell
Director of Business Development
MediChem Research, Inc.
12305 S. New Avenue
Lemont, IL  60439

Subject:      Amendment No. 1 to Lease Agreement between MediChem Research Inc.
              and Institute of Gas Technology

Dear Nancy:


     Thank you for renewing your lease for another year. Enclosed please find
your fully executed copy of the subject amendment.

     If MediChem has any further needs or we can be of any assistance to you,
please do not hesitate to contact us.

                                             Sincerely,



                                             Harriet V. Heidelmeier
                                             Legal Services
                                             847/768-0800

Enclosures
<PAGE>

                                                               December 18, 1998


Ms. Katie Verzal
Des Plaines Laboratory Manager
MediChem Research, Inc.
12305 So. New Avenue
Lemont, IL  60439

Subject:   Amendment No. 2 to Lease Agreement Between MediChem Research Inc. and
           Institute of Gas Technology

Dear Ms. Verzal:

     The subject Amendment has been prepared in response to your request to
expand MediChem's laboratory space. If MediChem is in agreement with the terms
of this Amendment please have the enclosed copies signed on their behalf by a
duly authorized individual and return two (2) copies to my attention. Upon
receipt they will be signed on behalf of the Institute of Gas Technology and one
(1) fully executed copy will be returned to you.

     If you have any questions or concerns relating to this correspondence
please do not hesitate to contact us.

                                            Sincerely,


                                            Harriet V. Heldelrneier
                                            Legal Services
                                            847/768-0800

Enclosures

cc:  J. Meek
     D. Gornick
<PAGE>

December 21, 1998

Ms. Harriet V. Heidelmeier
Legal Services
Institute of Gas Technology
1700 S. Mount Prospect Road
Des Plaines, IL  60018

Dear Ms. Heidelmeier:

     Please find enclosed two copies of the executed lease agreement between
MediChem Research, Inc. and IGT. Please return one signed copy to my attention
at our Lemont facility. Thank you for your cooperation, and we looking forward
to working with you in the future.

Sincerely,



John Flavin
Vice President of Contractual Operations
<PAGE>

                               AMENDMENT NO. 2
                          TO LEASE AGREEMENT BETWEEN
                            MEDICHEM RESEARCH INC.
                                     AND
                          INSTITUTE OF GAS TECHNOLOGY

     THIS AMENDMENT made and entered into on the date of final execution hereof,
by and between INSTITUTE OF GAS TECHNOLOGY, an Illinois not-for-profit
corporation with principal offices at 1700 South Mount Prospect Road, Des
Plaines, Illinois 60018, (hereinafter called "IGT") and MEDICHEM RESEARCH INC.,
an Illinois corporation, having its principal place of business at, 1700 South
Mount Prospect Road, Des Plaines, Illinois 60018 (hereinafter called "Tenant").

     WHEREAS Tenant and IGT have entered into a Lease dated September 16, 1997,
for the lease of IGT premises to Tenant; and,

     WHEREAS, IGT and Tenant (hereinafter collectively called "the parties")
hereto desire to add Lab 636 to the space being leased by Tenant, and

     WHEREAS, IGT agrees to renovate Lab 636 in stages and allow Tenant to phase
in use of the area as each space becomes available, and

     WHEREAS, IGT will have approximately one-third of Lab 636 renovated and
available for occupancy by January 1, 1999 and the remainder available by
February 1, 1999,

     NOW THEREFORE, in consideration of the premises and Mutual promises herein
contained, the parties hereto agree as follows:

ARTICLE 2. Compensation, add the following paragraphs:
           ------------

     For the remainder of the term of this Lease (January 1, 1999 through
September 30, 1999), Tenant shall pay a total rental amount of One Hundred
Forty-Three Thousand Seven Hundred Seventy-Five Dollars ($143,775) for the use
of rooms listed in the attached Exhibit A2- 1, which attachment is hereby herein
incorporated and made a part hereof. The rental amount is to be paid monthly in
advance as follows:

     January 1, 1999 through January 30, 1999 - Tenant shall pay the current
     ----------------------------------------
     rental rate of Seven Thousand Five Hundred Seventy-Seven Dollars ($7,577)
     in addition to Two Thousand Four Hundred Thirty-Eight Dollars ($2,438) for
     one-third of Lab 636 and rooms 637-640, for a total of Ten Thousand Fifteen
     Dollars ($10,015).

     February 1, 1999 through September 30, 1999 - Tenant shall pay Seven
     -------------------------------------------
     Thousand Five Hundred Seventy-Seven Dollars ($7,577) per month plus Nine
     Thousand One Hundred Forty-Three Dollars ($9,143) for rental of Lab 636 and
     rooms 637-645, for a total of Sixteen Thousand Seven Hundred Twenty Dollars
     ($16,720).

<PAGE>

The above rental amount was calculated by multiplying the occupied square
footage of Lab 636 and rooms 637-645 by a base rental rate of $13 per square
foot and adding it to the rental rate for the space covered under Amendment
No.1.

     Upon renewal of this Agreement the base rental rate of $13 per square foot
will apply to all space listed in Exhibit A2-1 for the period October 1, 1999
through September 30, 2000. Tenant has option to renew lease for either a one or
three year period at a fixed annual increase of 3%, excluding year one. Tenant
will advise of execution of the option 3 months prior to termination of lease.

     Except as provided herein, all other terms and conditions of this agreement
as heretofore changed remain in full force and effect.


                                    AGREED:


INSTITUTE OF GAS TECHNOLOGY                MEDICHEM RESEARCH INC.

By: _______________________________        By: _________________________________

Name: _____________________________        Name: _______________________________

Title: ____________________________        Title: ______________________________

Date: _____________________________        Date: _______________________________
<PAGE>

                                 EXHIBIT A2-1

     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois. Both IGT
and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number,
which may or may not represent actual square footage.


--------------------------------------------------------------------------------
           Room No.               Estm. Sq. Footage          Rental Rate, $
           --------               -----------------          --------------
--------------------------------------------------------------------------------
           607-613                    5,400                      15.45
--------------------------------------------------------------------------------
             622                        485                      15.45
--------------------------------------------------------------------------------
Beginning January 1, 1999-

    637-645 and (A) of Lab 636        2,250                      13.00
--------------------------------------------------------------------------------
Beginning February 1, 1999-

    Remaining (B) of Lab 636          6,190                      13.00
--------------------------------------------------------------------------------
<PAGE>

                                                               February 17, 1999

Mr. John L. Flavin
Vice President of Contractual Operations
MediChem Research, Inc.
12305 So. New Avenue
Lemont, IL  60439

Subject:   Amendment No. 3 to Lease Agreement Between
           MediChem Research Inc. and Institute of Gas Technology

Dear Mr. Flavin:

     The subject Amendment has been prepared in response to your request to
expand MediChem's laboratory space to include Room 629. If MediChem is in
agreement with the terms of this Amendment please have the enclosed copies
signed on their behalf by a duly authorized individual and return two (2) copies
to my attention. Upon receipt they will be signed on behalf of the Institute of
Gas Technology and one (1) fully executed copy will be returned to you.

     If you have any questions or concerns relating to this correspondence
please do not hesitate to contact us.


                                            Sincerely,



                                            Harriet V. Heidelmeier
                                            Legal Services
                                            847/768-0800

Enclosures

cc:   J. Meek (w/e)
      D. Gornick (w/e)

<PAGE>

                                AMENDMENT NO. 3
                           TO LEASE AGREEMENT BETWEEN
                             MEDICHEM RESEARCH INC.
                                      AND
                          INSTITUTE OF GAS TECHNOLOGY

     THIS AMENDMENT made and entered into on the date of final execution hereof,
by and between INSTITUTE OF GAS TECHNOLOGY, an Illinois not-for-profit
corporation with principal offices at 1700 South Mount Prospect Road, Des
Plaines, Illinois 60018, (hereinafter called "IGT") and MEDICHEM RESEARCH INC.,
an Illinois corporation, having its principal place of business at, 1700 South
Mount Prospect Road, Des Plaines, Illinois 60018 (hereinafter called "Tenant").

     WHEREAS Tenant and IGT have entered into a Lease dated September 16, 1997,
for the lease of IGT premises to Tenant; and,

     WHEREAS, IGT and Tenant (hereinafter collectively called "the parties")
hereto desire to add Room 629 to the space being leased by Tenant;

     NOW THEREFORE, in consideration of the premises and mutual promises herein
contained, the parties hereto agree as follows:

ARTICLE 2.  Compensation, add the following paragraphs:
            ------------

     For the remainder of the term of this Lease (March 1, 1999 through
September 30, 1999),  Tenant shall pay a total rental amount of One Hundred
Twenty-Two Thousand Four Hundred Twenty-Three Dollars ($122,423) for the use of
rooms listed in the attached Exhibit A3-1, which attachment is hereby
incorporated herein and made part hereof.  The rental amount is to be paid
monthly in advance in equal installments of Seventeen Thousand Four Hundred
Eighty-Nine Dollars ($17,489) by Tenant to IGT.

The above rental amount was calculated by multiplying the occupied square
footage of Room 629 by a base rental rate of $13 per square foot and adding it
to the rental rate for the space covered under Amendment No. 2.

     Except as provided herein, all other terms and conditions of this agreement
as heretofore changed remain in full force and effect.


                                    AGREED:


INSTITUTE OF GAS TECHNOLOGY                  MEDICHEM RESEARCH INC.

By:______________________________            By:________________________________

Name:____________________________            Name:______________________________
<PAGE>

Title:___________________________           Title:______________________________

Date:____________________________           Date: ______________________________
<PAGE>

                                  EXHIBIT A3-1


     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois.  Both
IGT and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number,
which may or may not represent actual square footage.


---------------------------------------------------------------------------
       Room No.                Estm. Sq. Footage         Rental Rate, $
       --------                -----------------         --------------
---------------------------------------------------------------------------
        607-613                     5,400                   15.45
---------------------------------------------------------------------------
          622                        485                    15.45
---------------------------------------------------------------------------
Beginning January 1, 1999-

 637-645 and (A) of Lab 636         2,250                   13.00
---------------------------------------------------------------------------
Beginning February 16, 1999-

 Remaining  of Lab 636              6,190                   13.00
---------------------------------------------------------------------------
Beginning March 1, 1999-

 629                                 710                    13.00
---------------------------------------------------------------------------
<PAGE>

                                                                October 14, 1999



Mr. John L. Flavin
Vice President of Contractual Operations
MediChem Research, Inc.
12305 So. New Avenue
Lemont, IL  60439

Subject:  Amendment No. 4 to Lease Agreement Between
          MediChem Research Inc. and Institute of Gas Technology

Dear Mr. Flavin:

     Enclosed find one fully executed copy of the subject amendment, which has
been hand corrected, per MediChem's request, to reflect a reduction in the term
of the Agreement.

     If you have any questions or concerns relating to this correspondence
please do not hesitate to contact us.

                                          Sincerely,


                                          Harriet V. Heidelmeier
                                          Legal Services
                                          847/768-0800


Enclosures

cc: J. Meek (w/e)
    D. Gornick (w/e)
<PAGE>

                                AMENDMENT NO. 4
                           TO LEASE AGREEMENT BETWEEN
                             MEDICHEM RESEARCH INC.
                                      AND
                          INSTITUTE OF GAS TECHNOLOGY

     THIS AMENDMENT made and entered into on the date of final execution hereof,
by and between INSTITUTE OF GAS TECHNOLOGY, an Illinois not-for-profit
corporation with principal offices at 1700 South Mount Prospect Road, Des
Plaines, Illinois 60018, (hereinafter called "IGT") and MEDICHEM RESEARCH INC.,
an Illinois corporation, having its principal place of business at 1700 South
Mount Prospect Road, Des Plaines, Illinois 60018 (hereinafter called "Tenant").

     WHEREAS Tenant and IGT have entered into a Lease dated September 16, 1997,
for the lease of IGT premises to Tenant; and,

     WHEREAS, IGT and Tenant (hereinafter collectively called "the parties")
hereto desire to extend the term of this agreement,

     NOW THEREFORE, in consideration of the premises and mutual promises herein
contained, the parties hereto agree as follows:

ARTICLE 1. Term of Agreement, delete paragraph one in its entirety and replace
           -----------------
with the following:

     The term of this Agreement shall be three (3) years beginning 12:01 a.m.
October 1, 1997, and ending 12:00 midnight September 30, 2000.

ARTICLE 2.  Compensation, add the following paragraphs:
            ------------

     During the third year of this Agreement, October 1, 1999 through September
30, 2000,  Tenant shall pay a total rental amount of Two Hundred One Thousand
Seven Hundred Eighty-Seven and 30/100 Dollars ($201,787.30) for the use of rooms
listed in the attached Exhibit A4-1, which attachment is hereby incorporated
herein and made part hereof.  The rental amount is to be paid monthly in advance
in equal installments of Sixteen Thousand Eight Hundred Fifteen and 60/100
Dollars ($16,815.60) by Tenant to IGT.  The above rental amount was calculated
by multiplying the total room square footage from Exhibit A4-1, by a base rental
rate of $13 per square foot, and adding three percent (3%) annual escalation.

     Except as provided herein, all other terms and conditions of this agreement
as heretofore changed remain in full force and effect.
<PAGE>

                                    AGREED:


INSTITUTE OF GAS TECHNOLOGY                   MEDICHEM RESEARCH INC.

By:______________________________             By:_______________________________

Name:____________________________             Name:_____________________________

Title:___________________________             Title:____________________________

Date:____________________________             Date:_____________________________
<PAGE>

                                  EXHIBIT A4-1


     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois.  Both
IGT and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number,
which may or may not represent actual square footage.


-------------------------------------------------------------------------------
         Room No.                                  Estm. Square Footage
         --------                                  --------------------
--------------------------------------------------------------------------------
          607-613                                        5,400

--------------------------------------------------------------------------------
            622                                           520

--------------------------------------------------------------------------------
            629                                           710

--------------------------------------------------------------------------------
          636-645                                        8,440

--------------------------------------------------------------------------------
<PAGE>

                                                                 January 7, 2000


Mr. John L. Flavin
Vice President of Contractual Operations
MediChem Research Inc.
12305 So. New Avenue
Lemont, IL 60436

Subject: Amendment No. 5 to Lease Agreement Between
         MediChem Research Inc. and Institute of Gas Technology

Dear Mr. Flavin:

     Enclosed please find three copies of the subject Amendment.  If MediChem is
in agreement with the terms of this Amendment please have the enclosed copies
signed on their behalf by a duly authorized individual and return two (2) copies
to my attention.  Upon receipt they will be signed on behalf of the Institute of
Gas Technology and one (1) fully executed copy will be returned to you.

     If you have any questions or concerns relating to this correspondence
please do not hesitate to contact us.


                                  Sincerely,


                                  Harriet V. Heidelmeier
                                  Legal Services
                                  847/768-0800


Enclosures

cc: J. Meek (w/e)
    D. Gornick (w/e)
<PAGE>

                                  EXHIBIT A5-1

     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois.  Both
IGT and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number,
which may or may not represent actual square footage.



             Room No.                               Estm. Square Footage
             --------                               --------------------
-------------------------------------------------------------------------------
             607-613                                      5,400
-------------------------------------------------------------------------------
               622                                         710
-------------------------------------------------------------------------------
               629                                        8,440
-------------------------------------------------------------------------------
             636-645                                      8,440
-------------------------------------------------------------------------------
               548                                         161
-------------------------------------------------------------------------------
<PAGE>

                                                                January 28, 2000



Mr. Patrick W. Flavin
Manager of Legal Affairs
MediChem Research, Inc.
12305 So. New Avenue
Lemont, IL  60439

Subject: Amendment No. 5 to Lease Agreement Between
         MediChem Research Inc. and Institute of Gas Technology

Dear Mr. Flavin

     Enclosed for your records please find one fully executed copy of the
subject amendment.

     If you have any questions or concerns relating to this correspondence or if
we can be of any further assistance to you, please do not hesitate to contact
us.


                                   Sincerely,


                                   Harriet V. Heidelmeier
                                   Legal Services
                                   847/768-0800


Enclosures

cc: J. Meek (w/e)
    D. Gornick (w/e)
<PAGE>

                                AMENDMENT NO. 5
                           TO LEASE AGREEMENT BETWEEN
                             MEDICHEM RESEARCH INC.
                                      AND
                          INSTITUTE OF GAS TECHNOLOGY

     THIS AMENDMENT made and entered into on the date of final execution hereof,
by and between INSTITUTE OF GAS TECHNOLOGY, an Illinois not-for-profit
corporation with principal offices at 1700 South Mount Prospect Road, Des
Plaines, Illinois 60018, (hereinafter called "IGT") and MEDICHEM RESEARCH INC.,
an Illinois corporation, having its principal place of business at 1700 South
Mount Prospect Road, Des Plaines, Illinois 60018 (hereinafter called "Tenant").

     WHEREAS Tenant and IGT have entered into a Lease dated September 16, 1997,
for the lease of IGT premises to Tenant; and,

     WHEREAS, IGT and Tenant (hereinafter collectively called "the parties")
hereto desire to add Room 548 to the space being leased by Tenant,

     NOW THEREFORE, in consideration of the premises and mutual promises herein
contained, the parties hereto agree as follows:

ARTICLE 2.  Compensation, add the following paragraphs:
            ------------

     In addition to Tenant's monthly rental amount of Sixteen Thousand Eight
Hundred Fifteen and 60/100 Dollars ($16,815.60) Tenant shall pay $179.65 per
month for the use of Room 548, for a total monthly rental amount of Sixteen
Thousand Nine Hundred Ninety-Five and 25/100 Dollars ($16,995.25).  Tenant shall
take occupancy of Room 548 on January 10, 2000.  The prorated additional rent
for the month of January is $127.49.  Commencing with the February payment the
amount is to be paid monthly in advance in equal installments of Sixteen
Thousand Nine Hundred Ninety-Five and 25/100 Dollars ($16,995.25) by Tenant to
IGT.  The above rent amount was calculated by multiplying the total room square
footage from Exhibit A5-1, by a base rental rate of Thirteen and 39/100 Dollars
($13.39) per square foot.
<PAGE>

     Except as provided herein, all other terms and conditions of this agreement
as heretofore changed remain in full force and effect.


                                    AGREED:



INSTITUTE OF GAS TECHNOLOGY                 MEDICHEM RESEARCH INC.

By:_____________________________            By:________________________________

Name:___________________________            Name:______________________________

Title:__________________________            Title:_____________________________

Date:___________________________            Date:______________________________
<PAGE>

                                  EXHIBIT A5-1

     IGT agrees to lease to Tenant the following premises located at Institute
of Gas Technology, 1700 South Mt. Prospect Road, Des Plaines, Illinois.  Both
IGT and Tenant agree that the actual area to be used by Tenant is difficult to
measure, and that the estimated square footage below is a negotiated number,
which may or may not represent actual square footage.


--------------------------------------------------------------------------------
          Room No.                                  Estm. Square Footage
          --------
--------------------------------------------------------------------------------
           607-613                                          5,400
--------------------------------------------------------------------------------
             622                                             520
--------------------------------------------------------------------------------
             629                                             710
--------------------------------------------------------------------------------
           636-645                                          8,440
--------------------------------------------------------------------------------
             548                                             161
--------------------------------------------------------------------------------