Exhibit 10.25

Amendment No. 1 to Exclusive License Agreement

           This Amendment No. 1 (this “Amendment”) to Exclusive License
Agreement, effective as of December 3, 1996 (as amended, the “License
Agreement”) is made as of October 1, 2002 by and between Pharmacia & Upjohn
Company, a corporation organized and existing under the laws of the State of
Delaware (“Pharmacia”), and United Therapeutics Corporation (formerly known as
Lung RX, Inc.), a corporation organized and existing under the laws of the State
of Delaware (“United Therapeutics”).

           WHEREAS, Pharmacia and United Therapeutics have entered into the
License Agreement regarding United Therapeutics’s development and
commercialization of the Product (as defined in the License Agreement);

           WHEREAS, United Therapeutics has received the FDA approval for the
Product in the United States;

           WHEREAS, the parties desire to amend certain terms and conditions of
the Agreement as set forth herein;

           NOW THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged by both parties, Pharmacia and
United Therapeutics hereby agree as follows:

  1.   Definitions. Unless otherwise defined herein, all capitalized terms used
in this Amendment shall have the meanings ascribed to them in the License
Agreement.     2.   Use of Know-How. For clarity, United Therapeutics
acknowledges and agrees that the Product, as approved by the FDA, utilizes or
incorporates the Know-How.     3.   Milestone Payment. United Therapeutics shall
pay to Pharmacia an amount equal to $100,000 within ten (10) days after the
signing of this Amendment as the milestone payment for the approval of the first
NDA in the United States pursuant to Section 5.2(a) of the License Agreement.  
  4.   Amended Royalties. Section 6.1 of the License Agreement is hereby amended
and restated in its entirety as follows:         “In consideration of the
Know-How license granted to United Therapeutics hereunder, United Therapeutics
shall pay or caused to be paid to P&U a royalty equal to 4% of Net Sales of the
Product in the Territory for a period of 10 years commencing on the date of the
first commercial sale of the first Product sold in the applicable country in the
Territory; provided, however, no royalties shall be due on the first $25 million
of Net Sales of the Product in any calendar year. Notwithstanding the foregoing,
with respect to Europe only, United Therapeutics’ obligations to pay royalties
payable on Net Sales of a given Product shall cease as of the date on which the
Know-How embodied in such Product becomes published or generally known to the
public through no fault on the part of United Therapeutics or its Affiliates or
sublicensees.”

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  5.   Third Party Royalties. Section 6.3 of the License Agreement is hereby
amended and restated in its entirety as follows:         “If United Therapeutics
or its sublicensees determine, at United Therapeutics’ or its sublicensees’s
discretion, that it is necessary to pay royalties or other fees to any Third
Party in order to market or develop a Product in a given country of the
Territory, United Therapeutics may deduct such royalties from royalties
thereafter due P&U with respect to Net Sales of such Product in such country,
but in no event shall the royalties due P&U on such Net Sales of such Product in
such country on account of any reduction pursuant to this Section 6.3 be thereby
reduced to less than 2% of Net Sales of Product for which royalties are payable
pursuant to Section 6.1 hereof.”     6.   Entire Agreement. This Amendment
constitutes the entire understanding and agreement between the parties and
supersedes all previous writings and understandings between the parties with
respect to the subject matter hereof. No term or provision of this Amendment
shall be varied or modified by any prior or subsequent statement, conduct or act
of either of the parties, except that the parties may amend this Amendment by
written instruments specifically referring to and executed in the same manner as
this Amendment. In the event any of the provisions in the License Agreement
shall be inconsistent with the provisions of this Amendment, the provisions in
this Amendment shall govern.     7.   No Other Changes. Except as expressly
modified herein, all terms and conditions of the License Agreement shall remain
in full force and effect.

           IN WITNESS WHEREOF, the parties have caused their authorized
representatives to execute this Amendment as of the date first above written.

      PHARMACIA & UPJOHN COMPANY   UNITED THERAPEUTICS CORPORATION

              By:   /s/ Douglas R. Morton, Jr.   By:   /s/ Paul Mahon Name:  
Douglas R. Morton, Jr.   Name:   Paul Mahon Title:   Group Vice President,
Technology   Title:   Sr. Vice President & General Counsel     Acquisitions &
Operations             Discovery Research        

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