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                                                                    EXHIBIT 10.1


     THIS CONTRACT CONTAINS INDEMNIFICATION PROVISIONS. READ IT CAREFULLY.

                         OFFICE BUILDING LEASE AGREEMENT
                             BASIC LEASE INFORMATION

This Office Lease dated April 8, 1998 (the "Lease") amends and replaces the old
lease between the same parties dated October 16, 1996 as amended by Amendment of
Lease dated March 26, 1997 (the "Old Lease"). The Old Lease governs the
relationship of the parties from October 16, 1996 to the Commencement Date of
this Lease; thereafter the terms of this Lease apply.


LEASE DATE:                APRIL 8, 1998

TENANT:                    ILEX ONCOLOGY, INC., A DELAWARE CORPORATION

TENANT ADDRESS:            11550 IH 10 WEST, SUITE 300
                           SAN ANTONIO, TEXAS  78230

CONTACT:                   JAMES KOCH                TELEPHONE: (210) 677-6080

LANDLORD:                  N.W.A.  LIMITED PARTNERSHIP

LANDLORD'S ADDRESS:        11550 IH 10 WEST , SUITE 185
                           SAN ANTONIO, TEXAS  78230

CONTACT:                   BUILDING MANAGER          TELEPHONE: (210) 694-4024

PREMISES:         Suite No. 300 deemed to contain 21,036 square feet of Rentable
     Area (as hereinafter defined), the same being 18,291 square feet of Usable 
     Area (as hereinafter defined);

                  Suite 170 deemed to contain 4,810 square feet of Rentable Area
                  (as hereinafter defined), the same being 4,183 square feet of
                  Usable Area (as hereinafter defined);

                  Suite 120 deemed to contain 1,308 square feet of Rentable Area
                  (as hereinafter defined), the same being 1,137 square feet of
                  Usable Area (as hereinafter defined) is added to the Premises
                  on the date Landlord has substantially completed the Tenant
                  Improvements for the Suite and tendered possession of that
                  Suite to Tenant.

                  Suite 100 deemed to contain 11,090 square feet of Rentable
                  Area (as hereinafter defined), the same being _________ square
                  feet of Usable Area (as hereinafter defined) is added to the
                  Premises on the date Landlord has substantially completed the
                  Tenant Improvements for the Suite and tendered possession of
                  that Suite to Tenant.

                  Suite 180 deemed to contain 4,025 square feet of Rentable Area
                  (as hereinafter defined), the same being __________ square
                  feet of Usable Area (as hereinafter defined) is added to the
                  Premises on the date Landlord has substantially completed the
                  Tenant Improvements for the Suite and tendered possession of
                  that Suite to Tenant.

                  Suite 270 deemed to contain 1.336 square feet of Rentable Area
                  (as hereinafter defined), the same being 1,162 square feet of
                  Usable Area (as hereinafter defined) is added to the Premises
                  on May 1, 1998 and deleted from the Premises when Suite 100 is
                  added to the Premises;

                  Suite 240 deemed to contain 3,261 square feet of Rentable Area
                  (as hereinafter defined), the same being 2,836 square feet of
                  Usable Area (as hereinafter defined) is added to the Premises
                  on July 1, 1998 and deleted from the Premises when Suite 100
                  is added to the Premises;

                  Suites 300, 170, 270, 240, 100, 120 and 180 are outlined on
                  the plan attached to this Amendment as Exhibit A, and are
                  located in the office building (the "Building") located on the
                  land described as, NCB 17442, BLK 1, LOT 1, NW Office Park
                  UT-1, Bexar County, Texas and known as Northwest Atrium Office
                  Building, 11550 IH 10 West (the "Land").


TERM:                      The period commencing ON THE DATE OF COMPLETE 
                           EXECUTION OF THIS LEASE (the

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