Document:

<PAGE>   1
                                                                     EXHIBIT 4.1

                       [INTROGEN THERAPEUTICS, INC. LOGO]

COMMON STOCK                                                        COMMON STOCK

   NUMBER                                                              SHARES

<TABLE>
<S>                                                                                  <C>
THIS CERTIFICATE IS TRANSFERABLE IN                                                            CUSIP 46119F 10 7
   NEW YORK, N.Y. OR BOSTON, MA.                                                     SEE REVERSE FOR CERTAIN DEFINITIONS
</TABLE>

                          INTROGEN THERAPEUTICS, INC.

              INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

THIS CERTIFICATE IS TRANSFERABLE IN                    CUSIP 46119F 10 7
   NEW YORK, N.Y. OR BOSTON, MA.             SEE REVERSE FOR CERTAIN DEFINITIONS

         THIS CERTIFIES THAT

         IS THE RECORD HOLDER OF

     FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK, $.001 PAR VALUE
                                 PER SHARE, OF

                          INTROGEN THERAPEUTICS, INC.

transferable on the books of the Corporation in person or by duly authorized
attorney upon surrender of the Certificate properly endorsed. This Certificate
is not valid until countersigned by the Transfer Agent and registered by the
Registrar.

     Witness the facsimile seal of the Corporation and the facsimile
signatures of its duly authorized officers.

DATED:

                       [INTROGEN THERAPEUTICS, INC. SEAL]

/s/ RODNEY VARNER                                   /s/ DAVID G. NANCE
   SECRETARY                               PRESIDENT AND CHIEF EXECUTIVE OFFICER

                                       COUNTERSIGNED AND REGISTERED:
                                                EQUISERVE TRUST COMPANY, N.A.
                                                                  TRANSFER AGENT
                                                                   AND REGISTRAR

                                       By

                                                /s/ CHARLES V. ROSSI

                                                            AUTHORIZED SIGNATURE<PAGE>   1
                                                                 EXHIBIT 10.7(c)

                       FIRST AMENDMENT TO LEASE AGREEMENT

     This is the First Amendment ("Amendment") to the Lease Agreement ("Lease
Agreement") made and entered into by and between Plaza Del Oro Business Center
and Introgen Therapeutics, Inc. with an effective date of June 7, 1996.

     For $10.00 and other good and valuable consideration, including exercise by
Tenant of its initial six month option to extend, Landlord and Tenant agree to
amend the Lease Agreement by adding the following language at the end of
subparagraph O of Article II of the Lease after the sentence ending with the
word "hereunder":

     Provided that Tenant exercises its first option to extend for a six month
     period as provided above, Tenant is hereby granted a second option to
     extend the term of this Lease for an additional six month period (the
     "Second Extension Term") upon the same terms and conditions as herein
     contained, provided, Tenant gives Landlord written notice of Tenant's
     election to extend its option for the Second Extension Term at least sixty
     days prior to the expiration of the initial extended term. Further,
     provided that Tenant has exercised its options for the initial extended
     term and for the Second Extension Term, Tenant is hereby granted an option
     to extend the term of this Lease for an additional six month period (the
     "Third Extension Term") upon the same terms and conditions as herein
     contained, provided, Tenant gives Landlord written notice of Tenant's
     election to exercise its option for a Third Extension Term at least sixty
     days prior to the expiration of the Second Extension Term. The rental to be
     paid for each of the three six month extended terms shall be an amount
     equal to the rental to be paid for the initial term hereunder.

     Except as herein amended, the Lease Agreement shall remain in full force
and effect. Landlord confirms that Tenant has timely exercised its option for
the initial six month extension term.

     Executed to be effective as of the 9 day of May, 1997.

                                                  SAM H. HAWKINS, dba
                                                  PLAZA DEL ORO BUSINESS CENTER

                                                  By: /s/ SAM H. HAWKINS
                                                      --------------------------
                                                      Sam H. Hawkins

                                                  INTROGEN THERAPEUTICS, INC.

                                                  By: /s/ DAVID ENLOE
                                                      --------------------------
                                                  Name: David Enloe
                                                        ------------------------
                                                  Title: VP-Administration
                                                         -----------------------<PAGE>   1
                                                                 EXHIBIT 10.7(d)

                      SECOND AMENDMENT TO LEASE AGREEMENT

This is the Second Amendment ("Second Amendment") to the Lease Agreement ("Lease
Agreement") made and entered into by and between Plaza del Oro Business Center
and Introgen Therapeutics, Inc. with an effective date of June 7, 1996 and
First Amendment ("First Amendment") thereto executed May 9, 1997.

For $10.00 and other good and valuable consideration, including exercise by
Tenant of its option to extend, Landlord and Tenant agree to amend the Lease
Agreement by adding the following language at the end of subparagraph O of
Article VI of the Lease and First Amendment after the sentence ending with the
word "hereunder".

         Provided that Tenant exercises its option to extend for the Third
         Extension Term, Tenant is hereby granted a fourth option to extend the
         term of this Lease for an additional two year period (the "Fourth
         Extension Term") commencing January 1, 1999 and ending December 31,
         2000 upon the same terms and conditions as herein contained except for
         rental which will be Twenty-Seven Thousand and no/100 Dollars per annum
         paid monthly in advance as provided herein in the amount of Two
         Thousand Two Hundred Fifty and no/100 Dollars ($2,250.00), and
         provided, Tenant gives Landlord written notice of Tenant's election to
         exercise its option for the Fourth Extension Term on or before
         August 1, 1998. Further, provided that Tenant has exercised its option
         for the Fourth Extension Term, Tenant is hereby granted an option to
         extend the term of this Lease for an additional one year period (the
         "Fifth Extension Term") upon the same terms and conditions as herein
         contained, provided, Tenant gives Landlord written notice of Tenant's
         election to exercise its option for the Fifth Extension Term at least
         one hundred eighty (180) days prior to the expiration of the Fourth
         Extension Term. The rental to be paid for the Fifth Extension Term
         shall be an amount equal to the rental to be paid for the Fourth
         Extension Term.

Except as herein amended, the Lease Agreement shall remain in full force and
effect. Landlord confirms that Tenant has timely exercised its option for the
Third Extension Term.

         Executed to be effective as of the 31st day of July, 1998.

                                     SAM H. HAWKINS, dba
                                     PLAZA DEL ORO BUSINESS CENTER

                                     By: /s/ SAM H. HAWKINS
                                         -----------------------------
                                         Sam H. Hawkins

                                     INTROGEN THERAPEUTICS, INC.

                                     By: /s/ J. DAVID ENLOE JR.
                                         -----------------------------
                                         J. David Enloe Jr.
                                         Vice President-Administration<PAGE>   1
                                                                 EXHIBIT 10.7(e)

                       THIRD AMENDMENT TO LEASE AGREEMENT

This is the Third Amendment ("Third Amendment") to the Lease Agreement ("Lease
Agreement") made and entered into by and between Plaza del Oro Business Center
and Introgen Therapeutics, Inc. with an effective date of June 7, 1996, a First
Amendment thereto dated May 9, 1997, and a Second Amendment ("Second Amendment")
thereto executed July 31, 1998.

For $10.00 and other good and valuable consideration, including exercise by
Tenant of its option to extend, Landlord and Tenant agree to amend the Lease
Agreement by adding the following language at the end of subparagraph O of
Article VI of the Lease and First and Second Amendment after the sentence with
the word "hereunder".

         Provided that Tenant exercised its option to extend the Fifth Term,
         Tenant is hereby granted a sixth option to extend the term of this
         Lease for an additional six month period (the "Sixth Extension Term")
         commencing January 1, 2002 and ending June 30, 2002 upon the same terms
         and conditions as herein contained except for rental which will be
         Twenty-seven Thousand and no/100 dollars per annum paid monthly in
         advance as provided herein in the amount of Two Thousand Two Hundred
         Fifty and no/100 Dollars ($2,250.00), and provided, Tenant gives
         Landlord written notice of Tenant's election to exercise its option for
         the Sixth Extension Term on or before July 1, 2001. Further, provided
         that Tenant has exercised its option for the Sixth Extension Term,
         Tenant is hereby granted an option to extend the term for this Lease
         for an additional six month period (the "Seventh Extension Term") upon
         the same terms and conditions as herein contained, provided, Tenant
         gives Landlord written notice of Tenant's election to exercise its
         option for the Seventh Extension Term at least sixty (60) days prior to
         the expiration of the Sixth Extension Term. The rental to be paid for
         the Seventh Extension Term shall be an amount equal to the rental to be
         paid for the Sixth Extension Term.

Except as herein amended, the Lease Agreement shall remain in full force and
effect. Landlord confirms that Tenant has timely exercised its option for the
Fifth Extension Term.

         Executed to be effective as of the 29th day of June, 2000.

                                          SAM H. HAWKINS, dba
                                          PLAZA DEL ORO BUSINESS CENTER

                                          By: /s/ SAM H. HAWKINS
                                              -------------------------
                                              Sam H. Hawkins

                                          INTROGEN THERAPEUTICS, INC.

                                          By: /s/ J. DAVID ENLOE JR.
                                              -------------------------
                                              J. David Enloe Jr.
                                              Vice President-Operations

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