<PAGE>
                                       
                                February 8, 1999

[Name]
Vice President, [Title]
[Address]

          Re:  Severance Payment
               -----------------

Dear [NAME]:

     You are currently serving as the Vice President, [TITLE] of NeXstar 
Pharmaceuticals, Inc.  In such capacity and as an incentive for your 
continued service, NeXstar hereby agrees as follows.

     If there is a Change in Control of NeXstar Pharmaceuticals, Inc., a
     Delaware corporation ("NeXstar"), during the period in which you are
     employed by NeXstar as its Vice President, [TITLE] and, within 12 months
     after such Change in Control, NeXstar or its successor:
     
          (a)  terminates your employment without Cause,
          (b)  substantially diminishes the functions and responsibilities of
               your job, or
          (c)  requires you to relocate your current place of residence, or
               requires you to work regularly in and from an office located more
               than 50 miles from the current office of NeXstar in which you now
               work,

     then NeXstar or its successor shall (1) pay you a severance amount equal to
     12 months of your then current base salary (excluding any bonuses or other
     compensation amounts), (2) provide for your continued participation in any
     health benefit plans offered by the Company for a period of 12 months after
     your termination of employment (provided such participation shall terminate
     upon your obtaining full time employment) at a cost to you equal to your
     cost immediately prior to such termination, and (3) provide outplacement
     services to you to the extent consistent with NeXstar's past practices;
     provided that you agree to sign a general release agreement releasing all
     claims you may have against NeXstar or its successor.  All severance
     benefits shall be paid consistent with NeXstar's past practices under its
     1998 Severance Pay Plan.  You shall be under no obligation to mitigate the
     costs to NeXstar or its successor of the severance payments contemplated by
     this Agreement.
     
     For purposes of this agreement, the following terms shall have the meanings
     set forth below:

<PAGE>

          "Cause" shall mean (a) the determination by the Board of Directors of
          the Company (the "Board") that you have ceased to perform your duties
          as an executive officer of the Company (other than as a result of your
          incapacity due to physical or mental illness or injury), which failure
          amounts to an intentional and extended neglect of your duties, (b) the
          Board's determination that you have engaged in or are about to engage
          in conduct materially injurious to the Company, (c) your having been
          convicted of a felony, or (d) your participation in activities
          prohibited by the terms of any agreement between the Company and you
          relating to your employment with the Company.

           "Change in Control" shall include, without limitation, the sale of
          more than 50% of the capital stock of NeXstar, a sale of all or
          substantially all of the assets of NeXstar (which shall not include
          the proposed spin-off of Iterex Technologies, Inc.) and a merger or
          consolidation of NeXstar with or into another corporate entity in a
          transaction in which NeXstar does not survive. 
          
          "Company" shall mean NeXstar and any successors thereto.

     This Agreement shall not be deemed a guarantee of employment or an 
express or implied contract of employment.  You remain an employee at will.

     Please indicate your agreement with these terms by executing this letter 
where indicated below and returning a copy to Barbara Kazmier, Vice 
President, Human Resources.

                                  NEXSTAR PHARMACEUTICALS, INC.


                                  By
                                     ------------------------------------------
                                     Michael E. Hart
                                     Vice President and Chief Financial Officer



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          [NAME]