<PAGE>
                                                                   EXHIBIT 10.25

                              [/\#/\] CERTAIN CONFIDENTIAL INFORMATION CONTAINED
                                  IN THIS DOCUMENT, MARKED BY BRACKETS, HAS BEEN
                                OMITTED AND FILED SEPARATELY WITH THE SECURITIES
                                    AND EXCHANGE COMMISSION PURSUANT TO RULE 406
                                      OF THE SECURITIES ACT OF 1933, AS AMENDED.

              LICENSE, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

         This License, Development and Commercialization Agreement (this
"Agreement") is made this ____ day of _________, 200_ and between Myogen, Inc.
("Myogen"), a Delaware corporation with principal offices at 7575 West 103rd
Avenue, Westminster, Colorado 80021, and Novartis Institutes for BioMedical
Research, Inc. ("NIBRI"), a Delaware corporation with principal offices at 400
Technology Square, Cambridge, Massachusetts 02139.

         Capitalized terms used but not defined in this Agreement have the
meanings provided in the Collaboration and Option Agreement by and between the
parties dated as of October 8, 2003 (the "Collaboration Agreement").

                                  INTRODUCTION

         WHEREAS, pursuant to the Collaboration Agreement, Myogen and NIBRI are,
or have been, engaged in discovering and developing compounds having a specific
therapeutic effect on the Myogen Targets or Collaboration Targets (each as
defined in the Collaboration Agreement);

         WHEREAS, NIBRI has exercised its option under the Collaboration
Agreement to license exclusively one or more of the Development Candidates (as
defined herein) for development and commercialization in the Licensed Field (as
defined herein) and in the Territory;

         NOW THEREFORE, in consideration of the foregoing premises, the parties
agree as follows:


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                                   ARTICLE I

                                  DEFINITIONS

         1.1. "ACTIVE COMPOUND" shall have the meaning set forth in Section 1.1
of the Collaboration Agreement.

         1.2. "AFFILIATE" shall have the meaning set forth in Section 1.3 of the
Collaboration Agreement.

         1.3. "COLLABORATION AGREEMENT" shall mean that certain Collaboration
and Option Agreement dated as of October 7, 2003 by and between Myogen and
NIBRI.

         1.4. "COLLABORATION COMPOUND" shall have the meaning set forth in
Section 1.4 of the Collaboration Agreement.

         1.5. "COLLABORATION TARGET" shall have the meaning set forth in Section
1.5 of the Collaboration Agreement.

         1.6. "COMMENCEMENT DATE" shall mean, with respect to the application of
this Agreement to a Development Candidate, the date on which NIBRI exercises its
option under Section 4.4 of the Collaboration Agreement with respect to that
Development Candidate.

         1.7. "COMPOUND" shall have the meaning set forth in Section 1.7 of the
Collaboration Agreement.

         1.8. "CONTROLLED" shall have the meaning set forth in Section 1.8 of
the Collaboration Agreement.

         1.9. "CO-PROMOTION EXPENSES" shall mean, with respect to each Drug
Product, [/\#/\]

                  (a)      [/\#/\]

                  (b)      [/\#/\]

                  (c)      [/\#/\]

                  (d)      [/\#/\]

                  (e)      [/\#/\]


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                  (f)      [/\#/\]

                  (g)      [/\#/\]

                  (h)      [/\#/\]

                  (i)      [/\#/\]

                  (j)      [/\#/\]

                  (k)      [/\#/\]

                  (l)      [/\#/\]

     [/\#/\]

         1.10. "CO-PROMOTION NOTICE" shall have the meaning set forth in Section
3.5(a) hereof.

         1.11. "CO-PROMOTION RESPONSE" shall have the meaning set forth in
Section 3.5(a) hereof.

         1.12. "CO-PROMOTION SHARE" shall have the meaning set forth in Section
3.5(a) hereof.

         1.13. "DEVELOPMENT CANDIDATE" shall mean the NIBRI Compound, Myogen
Compound or the Collaboration Compound, together with the Myogen Target or
Collaboration Target on which it has therapeutic action, as to which NIBRI has
entered into this License Agreement.

         1.14. "DEVELOPMENT COSTS" shall mean, [/\#/\]

                  (a)      [/\#/\]

                  (b)      [/\#/\]

                  (c)      [/\#/\]

                  (d)      [/\#/\]



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                  (e)      [/\#/\]

         1.15. "DEVELOPMENT PROGRAM" shall mean activities associated with
development of Active Compounds as Development Candidates for sale as Drug
Products in the Territory, including but not limited to: (a) formulation of
Active Compounds as Development Candidates for use in preparation for
preclinical studies; (b) preclinical animal studies performed in accordance with
GLP (or the applicable equivalent) in preparation for the filing of an IND (or
the applicable equivalent); (c) formulation and manufacture of Active Compounds
as Development Candidates for preclinical and clinical studies; (d) planning,
implementation, evaluation and administration of human clinical trials; (e)
manufacturing process development and scale-up for the manufacture of bulk
Active Compound and Drug Product; (f) preparation and submission of applications
for regulatory approval; and (g) post-market surveillance of approved drug
indications, as required or agreed as part of a marketing approval by any
governmental regulatory authority.

         1.16. "DRUG PRODUCT" shall mean a product prepared from bulk Active
Compound with respect to a Development Candidate, in finished dosage form ready
for administration to the ultimate consumer as a pharmaceutical.

         1.17. "[/\#/\] CO-PROMOTION SHARE" shall be equal to: (a) [/\#/\] the
Co-Promotion Share for the first year following the commercial launch of the
Drug Product in any of [/\#/\]; (b) [/\#/\] of the Co-Promotion Share for the
second year following the commercial launch of the Drug Product in any of
[/\#/\]; and (c) [/\#/\] of the Co-Promotion Share for the third and each
successive year following the commercial launch of the Drug Product in any of
[/\#/\].

         1.18. [/\#/\]

         1.19. "EXPIRATION DATE" shall have the meaning set forth in Section 8.1
hereof.

         1.20. "FIRST COMMERCIAL SALE" shall mean the first shipment of a Drug
Product to a Third Party by NIBRI or an Affiliate or sublicensee of NIBRI in a
country in the Territory following applicable Regulatory Approval of the Drug
Product in such country.



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         1.21. "GCP" shall mean the current Good Clinical Practice standards for
clinical trials for pharmaceuticals, as set forth in the Food, Drug and Cosmetic
Act and applicable regulations promulgated thereunder, as amended from time to
time, and such standards of good clinical practice as are required by the
regulatory authorities of the organizations and governmental agencies in
countries in which Drug Products are intended to be sold.

         1.22. "GLP" shall mean the current Good Laboratory Practices
regulations promulgated by the FDA, published at 21 CFR Part 58, as such
regulations may be from time to time amended, and such equivalent regulations or
standards of countries outside the United States as may be applicable to
activities conducted hereunder.

         1.23. "GMP" shall mean the current Good Manufacturing Practice
regulations promulgated by the FDA, published at 21 CFR Part 210 et seq., as
such regulations may be amended, and such equivalent foreign regulations or
standards as may be applicable with respect to bulk Active Compound or a Drug
Product manufactured or sold outside the United States.

         1.24. "GROSS CONTRIBUTION" means, with respect to Drug Products
co-promoted by the parties in accordance with Section 3.5 hereof, [/\#/\]

                  (a)      [/\#/\]

                  (b)      [/\#/\]

         1.25. "IND" shall mean an application to the Food and Drug
Administration, the filing of which is necessary to commence clinical testing of
Compounds in humans, or the equivalent application to the equivalent agency in
any other country or group of countries.

         1.26. "IN VIVO VALIDATION" means, with respect to an Active Compound,
the achievement of physiologically significant activity in an appropriate in
vivo model or models, where the level of physiologically significance and the in
vivo model(s) to be used will be specified by the JSC with respect to High
Priority Targets and Low Priority Targets and by Myogen with respect to
Extra-Collaboration Targets.



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         1.27. "KNOW-HOW" means all Technology other than inventions that are
the subject of Patents, including, but not limited to, information, technical
information, techniques, data, inventions, discoveries, trade secrets,
processes, practices, methods, materials, compositions, formulas, improvements,
knowledge, know-how, skill, experience, or test data, whether or not patented or
confidential, which is Controlled by a party relating to the Myogen Technology
or the development, manufacture, use, sale, offer for sale, or import of any
Active Compound, Development Candidate, or Drug Product, or any Improvement
thereto, including (but not limited to), pharmacological, toxicological,
pre-clinical and clinical test data, analytical and quality control data,
packaging, marketing, pricing, distribution, sales and manufacturing data or
descriptions, compositions-of-matter, assays and biological materials related
thereto and the content of this Agreement.

         1.28. "KNOW-HOW PERIOD" shall have the meaning set forth in Section
8.1.

         1.29. "IMPROVEMENT" means any enhancement in the formulation,
ingredients, preparation, presentation, means of delivery, dosage, packaging of,
manufacture, or any new or expanded therapeutic indication(s) for, an Active
Compound, a Drug Product, or any other metabolite or isomer thereof.

         1.30. "IMPROVEMENT PATENT" means any Patent (except for the formulation
Patent and use Patent with respect to a Development Candidate) containing claims
that cover an Improvement.

         1.31. "JOINT PATENT" shall mean a Patent which, absent rights
thereunder, would be infringed by the research, development, manufacture, use,
importation, sale, or distribution of the Development Candidate or a Drug
Product relating thereto, and is owned or Controlled jointly by NIBRI or a NIBRI
Affiliate, on the one hand, and Myogen or a Myogen Affiliate, on the other hand.

         1.32. "JOINT KNOW-HOW" shall mean Know-How that is owned or Controlled
jointly by NIBRI or a NIBRI Affiliate, on the one hand, and Myogen or a Myogen
Affiliate, on the other hand.



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         1.33. "JOINT TECHNOLOGY" shall mean Joint Patents and Joint Know-How.

         1.34. "LICENSED FIELD" shall mean all human and veterinary health care
applications including, but not limited to, research, prognosis and diagnosis
(subject to Section 2.5), therapeutics, prophylaxis, and monitoring with respect
to any indication, together with all agricultural purposes.

         1.35. "LICENSED PATENTS" shall mean any Myogen Patents that become the
subject of NIBRI's rights under Article II of this Agreement upon exercise of
its license and development option in accordance with the provisions of Section
4.4 of the Collaboration Agreement.

         1.36. "LISTED COUNTRY" shall mean a country listed on Schedule 1.36
hereof, as Schedule 1.36 may be amended from time to time on mutual written
agreement of the parties.

         1.37. "LIVE CLAIM" shall mean a claim of any issued, unexpired Licensed
Patent that shall not have been withdrawn, canceled or disclaimed, nor held
invalid or unenforceable by a court of competent jurisdiction in an unappealed
or unappealable decision.

         1.38. "MYOGEN COMPOUND" shall have the meaning set forth in Section
1.22 of the Collaboration Agreement.

         1.39. "MYOGEN KNOW-HOW" shall have the meaning set forth in Section
1.23 of the Collaboration Agreement, as the same shall exist on the Commencement
Date and at any time during the term of this Agreement.

         1.40. "MYOGEN PATENTS" shall have the meaning set forth in Section 1.24
of the Collaboration Agreement, as in effect on the Commencement Date and at any
time during the term of this Agreement. A list of Myogen Patents is appended
hereto as Schedule 1.40 and will be updated periodically to reflect additions
thereto during the course of this Agreement.

         1.41. "MYOGEN TARGET" shall have the meaning set forth in Section 1.25
of the Collaboration Agreement.



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         1.42. "MYOGEN TECHNOLOGY" shall mean all Myogen Patents and Myogen
Know-How.

         1.43. "NDA" means a New Drug Application submitted to the Food and Drug
Administration seeking approval to market and sell a Drug Product in the
Licensed Field in the United States of America, or a corresponding application
filed with any other regulatory agency seeking approval to market and sell a
Drug Product in the Licensed Field in a country in the Territory.

         1.44. "NET SALES" shall mean, with respect to a Drug Product, [/\#/\]

                  (a)      [/\#/\]

                  (b)      [/\#/\]

                  (c)      [/\#/\]

                  (d)      [/\#/\]

                  (e)      [/\#/\]

                  (f)      [/\#/\]

                  (g)      [/\#/\]

                  (h)      [/\#/\]

                  (i)      [/\#/\]

                  (j)      [/\#/\]

     [/\#/\]

                  (i)      [/\#/\]

                  (ii)     [/\#/\]



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                  (iii)    [/\#/\]

         1.45. "NIBRI COMPOUND" shall have the meaning set forth in Section 1.28
of the Collaboration Agreement.

         1.46. "NIBRI KNOW-HOW" shall have the meaning set forth in Section 1.29
of the Collaboration Agreement, as the same shall exist on the Commencement Date
and at any time during the term of this Agreement with respect to the
Development Candidate, any Drug Product incorporating the same, and their
respective use and manufacture.

         1.47. "NIBRI PATENTS" shall have the meaning set forth in Section 1.30
of the Collaboration Agreement, as in effect on the Commencement Date and at any
time during the term of this Agreement.

         1.48. "NIBRI TECHNOLOGY" shall mean all NIBRI Patents and NIBRI
Know-How.

         1.49. "PATENT PERIOD" shall have the meaning set forth in Section 8.1.

         1.50. "PATENTS" shall mean all existing patents and patent applications
and all patent applications hereafter filed, including any continuation,
continuation-in-part, division, provisional or any substitute applications, any
patent issued with respect to any such patent applications, any reissue,
reexamination, renewal or extension (including any supplementary protection
certificate) of any such patent, and any confirmation patent or registration
patent or patent of addition based on any such patent, and all foreign
counterparts of any of the foregoing.

         1.51. "PERSON" shall mean any individual, corporation, partnership,
association, limited liability company, trust, unincorporated organization or
government or political subdivision thereof.

         1.52. "PHASE I CLINICAL TRIAL" shall mean a clinical study, conducted
in accordance with a protocol approved by NIBRI of a Drug Product in human
volunteers with the endpoint of determining initial tolerance, safety and/or
pharmacokinetic information in single dose, single ascending dose, multiple dose
and/or multiple ascending dose regimens.


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         1.53. "PHASE II CLINICAL TRIAL" shall mean a clinical study, conducted
in accordance with a protocol approved by NIBRI, of a Drug Product in patients
to determine initial efficacy and dose range finding.

         1.54. "PHASE III CLINICAL TRIAL" shall mean a clinical study in
patients, conducted in accordance with a protocol approved by NIBRI, which
protocol is designed to ascertain efficacy and safety of a Drug Product for the
purpose of preparing and submitting a filing for Regulatory Approval in a
particular country in the Territory.

         1.55. "PHASE IV CLINICAL TRIAL" shall mean a clinical study initiated
in a country after receipt of Regulatory Approval for a Drug Product in such
country.

         1.56. "REGISTRATION FILING" shall mean, with respect to each
Development Candidate or related Drug Product, the submission to the relevant
governmental regulatory authority of an appropriate application seeking any
Regulatory Approval, and shall include, without limitation, any marketing
authorization application, supplementary application or variation thereof, or
any equivalent applications.

         1.57. "REGULATORY APPROVAL" shall mean, with respect to a country in
the Territory, all authorizations by the appropriate governmental entity or
entities necessary for commercial sale of a Drug Product in that country
including, without limitation and where applicable, approval of labeling, price,
reimbursement and manufacturing.

         1.58. "REGULATORY EXPENSES" shall mean, with respect to a Development
Candidate or related Drug Product, all out-of-pocket costs and fully allocated
costs incurred by or on behalf of a party in connection with the preparation and
filing of Registration Filings and the maintenance of Regulatory Approvals.

         1.59. "TECHNOLOGY" shall mean all data, technical information,
know-how, experience, inventions (whether or not patented), trade secrets,
processes and methods discovered, developed or applied (with the consent of its
owner) and Controlled by either party or its Affiliates, in connection with
performance by either party under the Research Program, or



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in connection with the conduct of a Development Program, that relate to the
research, development, utilization, manufacture or use of Targets or Compounds.

         1.60. "TERRITORY" shall mean [/\#/\]

         1.61. "THIRD PARTY" shall mean any Person that is not a party or an
Affiliate of any party to this Agreement.

                                   ARTICLE II

                               RIGHTS AND LICENSES

         2.1. NIBRI RIGHTS. Subject to the other provisions of this Agreement,
Myogen grants to NIBRI and its Affiliates a license, exclusive even as to
Myogen, with the right to sublicense, under the Myogen Patents and the Myogen
Know-How and in the Licensed Field, to research and have researched, develop and
have developed, make and have made, and use and have used the Development
Candidate and to research and have researched, develop and have developed, make
and have made, manufacture and have manufactured, use and have used, market and
have marketed, distribute and have distributed, sell and have sold, export and
import for sale, and have exported or imported for sale, Drug Products in each
country in the Territory. NIBRI understands that the licenses granted under this
Agreement to certain Myogen Technology that has been licensed by Myogen pursuant
to agreements with the University of Texas Southwestern Medical Center, the
University of North Texas Health Sciences Center and the University Licensing
and Equity Holdings, Inc. are subject to the retained rights of such licensors
to use such Myogen Technology for research, teaching and other
educationally-related, non-commercial purposes. Myogen retains all rights to
Myogen Technology except to the extent explicitly granted to NIBRI hereunder.

         2.2. SCOPE OF EXCLUSIVITY; DILIGENCE; DEVELOPMENT RESPONSIBILITY.

                  (a) As long as NIBRI is using commercially reasonable efforts
         to diligently develop and/or commercialize the Development Candidate in
         the Licensed Field:



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                           (i) The licenses granted to NIBRI in Section 2.1
                  shall be effective also with respect to any other Active
                  Compound which falls under the same Live Claim as an Active
                  Compound constituting the Development Candidate provided that
                  all of the terms and conditions of this Agreement (including
                  royalty and milestone payments) shall apply to all such other
                  Active Compounds; and

                           (ii) Myogen shall not develop, make, have made, use,
                  market and sell, itself or through a Third Party licensee, for
                  use within the Licensed Field, any other Active Compound which
                  falls under the same Live Claim as an Active Compound
                  constituting the Development Candidate.

                  (b) NIBRI shall be deemed to be using commercially reasonable
         efforts with respect to the provisions of Section 2.1 and Section 3.4
         if NIBRI or any of its Affiliates is actively undertaking diligent,
         commercially reasonable efforts, similar to those used for other
         products of NIBRI or its Affiliates that are of similar commercial
         potential, for the continuing development and the commercialization of
         the Development Candidate in the Licensed Field, including, without
         limitation, the development and/or optimization and/or further
         characterization of Active Compounds, initiation and conduct of
         clinical trials, submission of regulatory filings and commercial launch
         of Drug Products.

                  (c) Except as otherwise provided herein, NIBRI will have sole
         responsibility for, and bear the cost of conducting, the Development
         Program with respect to each Development Candidate and/or seeking
         Regulatory Approval of any Drug Product.

         2.3. JOINT INVENTIONS AND JOINT PATENTS. All inventions conceived of
and reduced to practice during the term of, or as a result of, this Agreement,
jointly by employees or agents of Myogen or its Affiliates, on one hand, and
employees or agents of NIBRI or its Affiliates, on the other hand ("Joint
Inventions") and all Patent applications and Patents claiming



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Joint Inventions, shall be owned jointly by Myogen and NIBRI, and such Patent
applications and Patents shall be included within the Joint Patents. The rights
of each party with respect to the Joint Technology shall be determined in
accordance with United States patent law as it applies to issues of joint
ownership of intellectual property as of the Effective Date of the Collaboration
Agreement.

         2.4. INVENTIONS NECESSARY TO THE LICENSE. If Myogen conceives and
reduces to practice during the term of this Agreement any new Technology
relating to a Development Candidate or Drug Product and covered by a Myogen
Patent, or acquires or Controls (either on the Effective Date or at any time
during the term of this Agreement) any Patent on a Technology, and such
Technology is necessary to NIBRI's exercise of its licensed rights, then the
definition of Myogen Patent will be deemed to include such Patents that are
included within the licenses granted to NIBRI under this Agreement.

         2.5. DIAGNOSTIC AND PROGNOSTIC PRODUCTS. In the event that NIBRI
desires to develop and commercialize any diagnostic or prognostic products based
upon any Development Candidate, the parties agree to negotiate in good faith the
terms under which NIBRI would be granted rights to develop and commercialize
such products.

         2.6. RIGHTS TO DISCONTINUED COMPOUNDS. In the event that NIBRI elects
to discontinue the Development Program with respect to a NIBRI Compound or
elects to terminate this Agreement for its convenience, and NIBRI subsequently
contemplates collaborating with a Third Party with respect to development and/or
commercialization of such NIBRI Compound, NIBRI shall give Myogen written notice
of the same. Within [/\#/\] of receipt of such notice, Myogen shall inform NIBRI
in writing as to whether it wishes to negotiate in good faith a license to such
NIBRI Compound within the Field. If Myogen so informs NIBRI, then the parties
shall have [/\#/\]to negotiate a transaction in good faith. If the parties are
unable to consummate a transaction within such period (or such longer period as
the parties may agree to in writing), then NIBRI may enter into a Third Party
transaction with respect to the NIBRI Compound.



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                                  ARTICLE III

                        DEVELOPMENT AND COMMERCIALIZATION

         3.1. DEVELOPMENT AND COMMERCIALIZATION RIGHTS. Subject to any
co-funding/co-promotion rights granted to Myogen pursuant to Section 3.5 hereof,
NIBRI, its Affiliates and/or sublicensees, if any, shall have sole rights, even
as to Myogen, in the Licensed Field to develop and manufacture on a commercial
scale the Development Candidate, the related Drug Product, and the active
ingredient in such Drug Product in the Territory, and to commercialize,
manufacture, promote, sell, book sales, and distribute each Drug Product and/or
the active ingredient in such Drug Product in each country in the Territory.
(The foregoing right to manufacture is subject to any applicable United States
statutory requirement that technology the development of which was funded in
part by the United States government must be manufactured domestically, unless
the United States government shall waive such requirement.) NIBRI and its
Affiliates, in their sole discretion, shall select, file, and own all rights to
any and all trademarks and trade dress relating to the Drug Product.

         3.2. INFORMATION TRANSFER. Myogen shall deliver (to the extent not
previously delivered to NIBRI pursuant to the Collaboration Agreement) as
promptly as practicable to NIBRI all information in Myogen's possession or under
its control (including summaries of raw data from clinical studies conducted by
Myogen of each Active Compound and related Myogen Target or Collaboration Target
comprising a Development Candidate), all scientific reports, and all processes
and procedures that are necessary or useful for further development, manufacture
and commercial exploitation and distribution of a Development Candidate in the
Territory. Such information shall include a summary of all material written
communications (copies of which Myogen will provide to NIBRI at NIBRI's request)
between Myogen or (to the extent available to Myogen) its other licensees and
the Food and Drug Administration (or any other similar regulatory authority)
concerning the Development Candidate. This information shall also include copies
of all Patents, copyrights, copyright registrations and applications therefor
and all other manifestations of the intellectual property embodied in the
Development Candidate, whether in human or machine readable form. Information
provided by Myogen will be subject to the provisions of Article VI hereof.



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         3.3. REGULATORY APPROVALS. NIBRI and/or its Affiliates will be
responsible for all required Regulatory Approvals in the Territory. All filings
will be made by NIBRI and/or its Affiliates. All Regulatory Approvals will be
held in the name of NIBRI and/or its Affiliates. NIBRI and its Affiliates shall
have the right to cross-reference information and regulatory filings relating to
the Development Candidate arising out of development work which previously has
been conducted by Myogen and its Affiliates and licensees, for the purpose of
regulatory filings hereunder.

         3.4. DUE DILIGENCE. Upon exercise of its Option with respect to a
Development Candidate, NIBRI and its Affiliates shall commence a Development
Program with respect to such Development Candidate and shall use commercially
reasonable efforts (as defined in Section 2.2(b)) to effect introduction of the
Drug Product relating to such Development Candidate into one or more commercial
markets in the Territory. In the normal course of development, any Development
Candidate may be dropped from development for valid scientific or medical
reasons provided to Myogen by NIBRI in writing and may be replaced (at the sole
discretion of NIBRI and/or its Affiliates) with another Development Candidate
having a therapeutic action on the same Myogen Target or Collaboration Target,
and such occurrence shall not constitute a failure of due diligence.

         3.5. CO-FUNDING AND CO-PROMOTION OPTION.

                  (a) Following the completion of Phase II Clinical Trials with
         positive results leading to NIBRI's reasonable expectation that it will
         conduct Phase III Clinical Trials and generation of relevant reports,
         NIBRI will provide Myogen with a report containing all relevant
         pre-clinical data and all relevant clinical data from the Phase I
         Clinical Trials and the Phase II Clinical Trials and a preliminary
         estimate of anticipated Co-Promotion Expenses (including sales force
         details) (the "Co-Promotion Notice"). In the event that Myogen wishes
         to co-fund and co-promote a given Development Candidate in either
         [/\#/\], or [/\#/\] and [/\#/\], Myogen shall give NIBRI written notice
         of the same no later than [/\#/\] after its receipt of the Co-Promotion
         Notice (the "Co-Promotion Response"). The Co-Promotion Response will
         specify the level of financial commitment that Myogen



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         will assume with respect to the co-funding of such Development
         Candidate and the co-promotion of such Development Candidate in [/\#/\]
         (the "Co-Promotion Share"); provided, that Myogen shall be required to
         commit to fund no less than [/\#/\] and no greater than [/\#/\] of the
         Development Costs and Co-Promotion Expenses of such Development
         Candidate that are attributable to the development of the Development
         Candidate in [/\#/\] and, if applicable, [/\#/\].

                  (b) Along with the Co-Promotion Response, Myogen will provide
         NIBRI with certification to NIBRI's reasonable satisfaction that it has
         the financial resources to co-fund the Development Costs and a detailed
         plan under which Myogen will have the financial resources to undertake
         co-promotion of the Drug Products, including the requisite sales force
         and sales force infrastructure required to provide its share of the
         promotional efforts. NIBRI may require documentary and other evidence
         that Myogen has, or will have at the appropriate time, the requisite
         resources (including personnel) and expertise to perform such
         co-promotion, including satisfying the same percentage level of
         Co-Promotion Expenses and promotional effort (including sales force
         details). Each Co-Promotion Response shall contain a commitment by
         Myogen that Myogen will be able to satisfy its portion of the projected
         levels of Co-Promotion Expenses and promotional effort, which may be
         satisfied initially or partially through use of a contract sales force;
         provided, however, that oversight of the contract sales force will be
         provided by Myogen sales management personnel. NIBRI may reject the
         Co-Promotion Response (and the corresponding co-promotion opportunity
         with Myogen) only if it has reasonable grounds based on such
         information that Myogen will not have such capability at the
         appropriate time.

                  (c) NIBRI and Myogen shall enter into good faith negotiations
         and will use reasonable best efforts to conclude a
         co-funding/co-promotion definitive agreement (the "Definitive
         Agreement"). The Definitive Agreement will outline the overall
         framework for the co-promotion effort, including roles and
         responsibilities, total Co-Promotion Expenses required and Myogen's
         co-promotion



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         funding commitment in [/\#/\] and, if applicable, [/\#/\] that is at a
         percentage level identical to the Co-Promotion Share and [/\#/\]
         Co-Promotion Share, respectively. The Definitive Agreement shall
         reflect, among other things, the following:

                           (i) Given the expertise of NIBRI and its Affiliates
                  in sales and marketing, NIBRI shall have sole authority to
                  determine the required budget of the Development Program and
                  the Co-Promotion Expenses and the total levels of promotional
                  effort (including sales force details) for such Drug Product,
                  with Myogen's input taking into account Myogen's expertise in
                  the heart failure and cardiovascular market and its
                  Co-Promotion Share.

                           (ii) Myogen shall be required under the Definitive
                  Agreement to share a portion of the Co-Promotion Expenses
                  incurred by both NIBRI and Myogen, taken together, and to
                  provide the portion of the promotional effort (including sales
                  force details), equal to the Co-Promotion Share with respect
                  [/\#/\], and [/\#/\] Co-Promotion Share with respect to
                  [/\#/\].

                           (iii) Myogen shall be entitled to receive a portion
                  of the Gross Contribution derived from sales of the relevant
                  Drug Product in [/\#/\] equal to the Co-Promotion Share, and
                  in [/\#/\], equal to the [/\#/\] Co-Promotion Share, and
                  NIBRI's royalty obligations to Myogen under this Agreement
                  shall cease with respect to [/\#/\] and, if applicable,
                  [/\#/\].

                           (iv) In consideration of the rights granted to Myogen
                  under the Definitive Agreement, Myogen will be required to pay
                  NIBRI: (A) the Development Costs expended by NIBRI as of the
                  effective date of the Definitive Agreement that are
                  attributable to the development of the Development Candidate
                  in [/\#/\] and, if applicable, [/\#/\] multiplied by the
                  Co-Promotion Share (the "Expense Reimbursement"); plus (B) a
                  risk premium equal to the Expense Reimbursement multiplied by
                  [/\#/\]. These payments will be made in [/\#/\] installments
                  on [/\#/\] and on [/\#/\]



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                  the Definitive Agreement, regardless of the status of the
                  Development Program.

                           (v) If Myogen is unable to satisfy its co-funding and
                  co-promotion obligations under the Definitive Agreement, or if
                  Myogen elects to terminate its co-promotion rights during the
                  term of the Definitive Agreement, then Myogen's share of the
                  Gross Contribution will be proportionately reduced taking into
                  account Myogen's contribution to the co-funding and, if
                  applicable, the commercialization of the Drug Product, to be
                  more fully specified in the Definitive Agreement.

                           (vi) Additional terms and conditions customary in the
                  industry for an agreement of this type.

                  (d) In no event shall any portion of Myogen's co-funding
         commitment be provided by a Third Party (not including any funding
         obtained by Myogen through loans or capital investment by Third
         Parties) without the consent of NIBRI.

                  (e) Upon exercising its option to co-promote, Myogen will be
         allowed to appoint [/\#/\] on NIBRI's International Project Team for
         the Development Candidates or Drug Products that are under development
         by NIBRI hereunder and will have access to project summaries and other
         documents provided by NIBRI to other members of the International
         Project Team.

                                   ARTICLE IV

                         MILESTONE AND ROYALTY PAYMENTS

         4.1. MILESTONE PAYMENTS.

                  (a) NIBRI shall make milestone payments in accordance with
         this Section 4.1 with respect to Active Compounds developed as
         Development Candidates



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         hereunder. Except as explicitly set forth below, pre-clinical milestone
         payments shall be payable on only one Active Compound per Myogen Target
         or Collaboration Target, and clinical milestones shall be payable only
         once on a particular Active Compound, even though that Active Compound
         may be subsequently developed for indications other than those for
         which Regulatory Approval was initially sought. In the event that an
         Active Compound fails in development, any milestone payments previously
         paid with respect to such Active Compound shall be fully creditable
         toward the same milestone due with respect to another Active Compound
         that acts on the same Myogen Target or Collaboration Target. NIBRI may
         deduct from any milestone payments otherwise due to Myogen under this
         Article IV the amount of any withholding and similar taxes required
         under applicable law to be withheld from such payments and paid to
         applicable tax authorities.

                  (b) The following milestone payments shall be payable within
         [/\#/\] of the relevant developmental event:

                                                         MILESTONE
         DEVELOPMENTAL MILESTONE:                         PAYMENT
         ------------------------                        ---------
         Pre-Clinical Milestones:

             o   Validation of high-throughput assays*    [/\#/\]

             o   In vitro validation of lead compound*    [/\#/\]

             o   In Vivo Validation of lead compound      [/\#/\]
                 or use of the lead compound as a
                 starting point for medicinal chemistry
                 and/or SAR exploration*

             o   Completion of Tox/ADME screening         [/\#/\]
                 and preclinical candidate
                 determination*



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         Clinical Milestones:
         --------------------

            o    IND filing                               [/\#/\]

            o    Initiation of Phase II clinical          [/\#/\]
                 evaluation

            o    Initiation of Phase III clinical         [/\#/\]
                 studies

            o    Regulatory filing [/\#/\]                [/\#/\]

            o    First regulatory filing [/\#/\]          [/\#/\]

            o    Regulatory Approval [/\#/\]              [/\#/\]

            o    First Regulatory Approval [/\#/\]        [/\#/\]

*Criteria for determining the achievement of any Milestone will be established
by the JSC.

         4.2. ROYALTY PAYMENTS DURING THE PATENT PERIOD. During the Patent
Period (as defined in Section 8.1 hereof), NIBRI shall make the following
royalty payments to Myogen on total annual Net Sales to unaffiliated Third
Parties of each Drug Product incorporating an Active Compound that has a
therapeutic effect on a Myogen Target or a Collaboration Target and that is
developed as a Development Candidate hereunder: [/\#/\] of Net Sales, plus: (a)
compensation for Third Party royalties owed by Myogen to the University of Texas
Southwestern Medical Center and the University of North Texas Health Sciences
Center of up to [/\#/\] of Net Sales; and (b) compensation for Third Party
royalties owed by Myogen to University Licensing and Equity Holdings, Inc. of up
to [/\#/\] of Net Sales, only to the extent that such royalty obligations are
incurred in connection with such Development Candidate.

         4.3. ROYALTY PAYMENTS DURING A KNOW-HOW PERIOD. During a Know-How
Period (as defined in Section 8.1 hereof), and in consideration for NIBRI's
license of the Myogen Know-How related to the Development Candidate, NIBRI shall
pay a [/\#/\] royalty to Myogen on total annual Net Sales to unaffiliated Third
Parties of each Drug Product incorporating an Active Compound that has a
therapeutic effect on a Myogen Target or a Collaboration Target and that is
developed as a Development Candidate hereunder; provided, however, that no
period during which a Licensed Patent covers such Active Compound shall be



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deemed to be a Know-How Period, in which case no royalty pursuant to this
Section 4.3 shall be due to Myogen at any time. Subsequent to the Expiration
Date, the license of such Myogen Know-How shall be considered to be perpetual
and fully paid.

         4.4. RESPONSIBILITY FOR MYOGEN'S THIRD PARTY ROYALTY OBLIGATIONS.
Myogen shall have sole responsibility for payment of all its Third Party royalty
obligations.

         4.5. REDUCED ROYALTY OBLIGATIONS. The obligation of NIBRI to pay
royalties to Myogen under this License Agreement shall be reduced upon the
occurrence of the following events:

                  (a) In the event of Myogen's material breach of this
         Agreement, which shall remain uncured one hundred eighty (180) days
         after written notice by NIBRI to Myogen of the same, NIBRI may, at its
         election, pay [/\#/\] of the royalties thereafter owed to Myogen under
         this Article IV into a third party escrow account to be held pending
         resolution of the dispute between NIBRI and Myogen by a court of
         competent jurisdiction. NIBRI may satisfy any final, non-appealable
         judgment awarded by such court from the then-current balance of the
         escrow account, and any excess of some or all of the escrow account
         will be promptly refunded to Myogen; provided that this Section 4.5(a)
         will not limit any compensatory or punitive damages that are
         recoverable at law or equity by NIBRI for Myogen's breach hereof.

                  (b) In the event that no Live Claim exists covering the
         Development Candidate NIBRI's royalty payment obligations under this
         Agreement in such jurisdiction shall be reduced to [/\#/\] should a
         Third Party generic compound enter the market in a particular
         jurisdiction with respect to a such Development Candidate.

                  (c) All Third Party royalties and license fees owed by Myogen
         to any Myogen licensors under agreements with such Third Party or Third
         Parties with respect to a Development Candidate licensed hereunder
         shall be Myogen's responsibility, subject to the provisions of Section
         9.3(b) hereof. In the event that NIBRI or an Affiliate thereof is
         required to pay Third Party royalties or license fees



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         in order to use the Myogen Targets licensed to NIBRI hereunder, NIBRI's
         obligation to pay royalties to Myogen shall be reduced by [/\#/\] of
         the amounts actually paid by NIBRI or its Affiliate to such Third
         Party; provided, however, that NIBRI's payment obligation shall in any
         case not be reduced more than [/\#/\] of what otherwise would be owed
         to Myogen hereunder.

         4.6. CERTAIN UNDERSTANDINGS REGARDING ROYALTY PAYMENTS. The parties
expressly agree that the royalties and milestones hereunder are in consideration
of the use of Myogen Technology to identify, synthesize, select or find useful
the Development Candidate as having a desired therapeutic effect on any Myogen
Target or Collaboration Target. Therefore, notwithstanding any earlier
expiration of the Licensed Patents, the term of payment of royalties hereunder
is required to compensate Myogen from revenues NIBRI or its Affiliates may in
the future derive from such use of the Myogen Technology and for the convenience
of accounting.


                                   ARTICLE V

                              REPORTING OBLIGATIONS

         5.1. DEVELOPMENT REPORTS. NIBRI shall prepare and submit to Myogen, on
a quarterly basis, reports which set forth in reasonable detail the progress of
the Development Program with respect to Development Candidate and the results of
work performed thereunder during the preceding quarter.

         5.2. SALES REPORTS AND RECORDS. During the term of this Agreement, but
only after the First Commercial Sale of a Drug Product, NIBRI shall deliver to
Myogen within ninety (90) days after the end of each calendar quarter a written
report showing actual Net Sales of Drug Products by NIBRI, its Affiliates and
sublicensees in each country in the Territory during such calendar quarter. All
Net Sales shall be stated in United States dollars, and shall convert the
amounts into United States dollars from the currency in which such amounts are
received by NIBRI using NIBRI's then-current standard exchange rate methodology
applied in its external reporting for the translation of foreign currency sales
into United States dollars. NIBRI will keep



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complete, true and accurate books of account and records for the purpose of
showing the derivation of Net Sales and all amounts payable to Myogen under this
Agreement. Such books and records will be kept by NIBRI or an Affiliate of NIBRI
for at least three (3) years following the end of the calendar quarter to which
they pertain. Such books and records, or copies thereof, will be made available
at NIBRI's principal place of business, upon request of Myogen, for inspection
and copying by an independent auditor appointed by Myogen for the purpose of
verifying NIBRI's sales reports or NIBRI's compliance in other respects with
this Agreement. Such inspections shall be at the expense of Myogen, unless a
variation or error exceeding five percent (5%) of the amount reported is
discovered in the course of any such inspection, whereupon the costs relating
thereto shall be for the account of NIBRI.

                                   ARTICLE VI

                                 CONFIDENTIALITY

         6.1. UNDERTAKING. During the term of this Agreement, each party (a
"Receiving Party") shall keep confidential, and other than as provided herein
shall not use or disclose, directly or indirectly, any trade secrets,
confidential or proprietary information, or any other knowledge, information,
documents or materials, owned, developed or possessed by the other party (the
"Proprietary Party"), whether in tangible or intangible form, the
confidentiality of which such other party takes reasonable measures to protect,
including but not limited to Collaboration Technology.

                  (a) Each Receiving Party shall take any and all lawful
         measures to prevent the unauthorized use and disclosure of such
         information, and to prevent unauthorized persons or entities from
         obtaining or using such information.

                  (b) Each Receiving Party further agrees to refrain from
         directly or indirectly taking any action that would constitute or
         facilitate the unauthorized use or disclosure of such information. Each
         Receiving Party may disclose such information to its Affiliates and to
         its or their respective officers, employees and agents, to authorized
         licensees and sublicensees, and to subcontractors in connection with
         the



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         development or manufacture of Development Candidate or Drug Products,
         to the extent necessary to enable such parties to perform their
         obligations hereunder or under the applicable license, sublicense or
         subcontract, as the case may be; provided, that such officers,
         employees, agents, licensees, sublicensees and subcontractors have
         entered into appropriate confidentiality agreements for secrecy and
         non-use of such information which by their terms shall be enforceable
         by injunctive relief at the instance of the Proprietary Party.

                  (c) Each Receiving Party shall be liable for any unauthorized
         use and disclosure of such information by its Affiliates or its or
         their respective officers, employees and agents and any such
         sublicensees and subcontractors.

         6.2. EXCEPTIONS. Notwithstanding the foregoing, the provisions of
Section 6.1 hereof shall not apply to knowledge, information, documents or
materials which the Receiving Party can conclusively establish:

                  (a) have entered the public domain without the Receiving
         Party's breach of any obligation owed to the Proprietary Party;

                  (b) have become known to the Receiving Party from a source
         other than the Proprietary Party, other than by breach of an obligation
         of confidentiality owed to the Proprietary Party; or

                  (c) are independently developed by the Receiving Party without
         breach of this Agreement, without reference to or reliance upon
         knowledge, information, or materials of the Proprietary Party as
         established by written records.

         6.3. In addition, a Receiving Party may, notwithstanding the
obligations of Section 5.1, disclose knowledge, information, documents or
materials that the Receiving Party can conclusively establish:

                  (a) are permitted to be disclosed by the prior written consent
         of the Proprietary Party; or



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                  (b) are required to be disclosed by the Receiving Party to
         comply with applicable laws or regulations, to defend or prosecute
         litigation or to comply with governmental regulations, provided that
         the Receiving Party provides prior written notice of such disclosure to
         the Proprietary Party and takes reasonable and lawful actions to avoid
         or minimize the degree of such disclosure.

         6.4. PUBLICITY. The timing and content of any press releases or other
public communications relating to the Agreement and the transactions
contemplated herein will, except as otherwise required by law, be determined
jointly by Myogen and NIBRI.

         6.5. SURVIVAL. The provisions of this Article VI shall survive the
termination of this Agreement.

                                  ARTICLE VII

                                     PATENTS

         7.1. PREPARATION. NIBRI shall take responsibility and pay for the
preparation, filing, prosecution and maintenance of: (a) any and all Patents in
the Territory included in NIBRI Patents, including without limitation any such
patents and patent applications claiming NIBRI Compounds or NIBRI Improvements
under the Collaboration Agreement; (b) subsequent to the Commencement Date with
respect to Development Candidate, any and all Patents covering a Development
Candidate and any uses, formulations and formulation process inventions with
respect thereto; and (c) all Joint Patents. Myogen and NIBRI shall each furnish
to the other party copies of significant documents relevant to any such
preparation, filing, prosecution or maintenance of Patents covered by
subsections (b) and (c) above. Myogen and NIBRI shall cooperate fully in the
preparation, filing, prosecution and maintenance of all Myogen Patents, NIBRI
Patents, and Joint Patents, executing all papers and instruments so as to enable
the responsible party to apply for, to prosecute and to maintain patent
applications and patents in its name in any country in the Territory. The
parties acknowledge the importance of maintaining the confidentiality of any
inventions or other information relating to potential patent claims prior to the
filing of patent applications with respect hereto. NIBRI shall provide Myogen



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prompt notice as to any decision to abandon a Myogen Patent or a Joint Patent in
a Listed Country.

         7.2. INFRINGEMENT. Each party shall notify the other promptly of any
possible infringements, imitations or unauthorized possession, knowledge or use
of the intellectual property embodied in any of the Development Candidate and
Myogen Know-How related to the manufacture or use of a Development Candidate or
Drug Products by Third Parties in any country in the Territory, of which such
party becomes aware. Each party shall promptly furnish the other party with full
details of such infringements, imitations or unauthorized possession, knowledge
or use, and shall assist in preventing any recurrence thereof. NIBRI or its
Affiliates shall be initially responsible, at its expense, for bringing any
action on account of any such infringements, imitations or possession, knowledge
or use, and Myogen shall cooperate with NIBRI, as NIBRI may reasonably request,
in connection with any such action. If, within sixty (60) days after receipt by
NIBRI of a written request from Myogen that it bring such an action, NIBRI does
not do so, Myogen shall have the right, at its expense and in its own name or in
the name of NIBRI, to do so on behalf of NIBRI, and NIBRI shall cooperate with
Myogen, as Myogen may reasonably request, in connection with such action,
including becoming a party to such suit. Such suit may not be settled by either
party without the other party's written consent, which shall not be unreasonably
withheld. Damages recovered in any actions referenced hereunder shall be
apportioned in accordance with the royalty schedules contained in this
Agreement, after reimbursement to each party of their respective expenses in
prosecuting such actions as provided hereunder.

                                  ARTICLE VIII

                              TERM AND TERMINATION

         8.1. TERM. The patent period with respect to any Development Candidate
or Drug Product incorporating that Development Candidate shall extend in each
country of the Territory until the later of the last to expire of any Licensed
Patents in that country covering the Development Candidate or Drug Product
incorporating that Development Candidate, the use thereof and/or the Myogen
Target or the Collaboration Target on which the Active Compound for the
Development Candidate acts, or in the case of [/\#/\], on a country-by-country
basis, the



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later of: (a) ten (10) years from the date of First Commercial Sale
of the Drug Product in that country; or (b) the last to expire of any Licensed
Patents in that country covering the Development Candidate or Drug Product (the
"Patent Period"). The know-how period with respect to any Development Candidate
or Drug Product incorporating that Development Candidate shall extend after the
First Commercial Sale in each country of the Territory for any period or periods
not to exceed five (5) years in the aggregate during which no Live Claim exists
covering the Development Candidate in such country (each a "Know-How Period").
Unless terminated earlier in accordance with the provisions herein, this
Agreement will expire, on a country-by-country basis, upon the completion of the
Patent Period and the Know-How Period (the "Expiration Date").

         8.2. MATERIAL BREACH BY NIBRI. Upon any material breach of the
provisions of this Agreement or of the Collaboration Agreement by NIBRI, which
material breach remains uncured by NIBRI one hundred eighty (180) days after
receipt of written notice of the same from Myogen, NIBRI's exclusive rights
within the Territory shall become non-exclusive, and upon Myogen's written
request, NIBRI shall thereupon render any reasonably necessary assistance to
Myogen or its designee to exercise Myogen's rights within the Territory.

         8.3. TERMINATION. Either Party may terminate this Agreement upon the
bankruptcy or financial insolvency of the other Party. NIBRI may terminate this
Agreement without cause at any time upon ninety (90) days written notice to
Myogen.

         8.4. EFFECT OF TERMINATION. Termination of this Agreement for any
reason, or expiration of this Agreement, will not affect: (a) obligations,
including the payment of any milestones or royalties, which have accrued as of
the date of termination or expiration; and (b) rights and obligations under the
following provisions of this Agreement, which shall survive termination or
expiration of this Agreement: Article VI, Sections 9.1, 9.2, and 9.3. Following
termination of this Agreement under Section 8.1 hereof with respect to a
particular country, NIBRI shall have a fully paid license under the Myogen
Technology to make, have made, use, sell, have sold and import for sale Drug
Product in that country in the Territory; provided however that NIBRI's
obligation to pay royalties and milestone payments under Article IV shall
continue after any termination of this Agreement for the time periods specified
in Section 8.1.



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                                   ARTICLE IX

                            MISCELLANEOUS PROVISIONS

         9.1. GOVERNING LAW, AND JURISDICTION. This Agreement shall be governed
and construed in accordance with the internal laws of the Commonwealth of
Massachusetts. Both parties hereto agree to submit to personal jurisdiction in
the Commonwealth of Massachusetts and to accept and agree to venue in that
Commonwealth.

         9.2. NO WARRANTY. Myogen makes no warranty of any kind whatsoever,
either express or implied, to NIBRI, or any customer of NIBRI, as to the ability
of NIBRI to understand and utilize the Myogen Technology. NIBRI makes no
warranty of any kind whatsoever, either express or implied, to Myogen, or to any
customer of Myogen, as to the ability of Myogen to understand and utilize the
NIBRI Technology. NIBRI shall indemnify and shall hold Myogen harmless against
and from any and all claims of Third Parties for damages due to personal injury
arising out of the actions of NIBRI, its Affiliates, agents, employees,
sublicensees or subcontractors, including but not limited to claims arising in
connection with the development, manufacturing, assembly, or sale of Development
Candidates and Drug Products by NIBRI. Myogen shall indemnify and hold NIBRI
harmless against and from any and all claims of Third Parties for damages due to
personal injury arising out of the actions of Myogen, its Affiliates, agents,
employees, sublicensees or subcontractors pursuant to this Agreement, including
but not limited to claims arising in connection with the Development Program.
During the term of this Agreement, the Parties shall keep each other promptly
and fully informed and will promptly notify appropriate authorities in
accordance with applicable law, after receipt of information with respect to any
serious adverse event (as defined by the ICH Harmonized Tripartite Guideline on
Clinical Safety Data Management), directly or indirectly attributable to the use
or application of Development Candidate or Drug Product.

         9.3. THIRD PARTY ACTIONS.

                  (a) To Myogen's knowledge, the exercise of the rights by NIBRI
         hereunder will not result in the infringement of valid patents of Third
         Parties.




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         Nevertheless, each party will promptly notify the other in the event
         any relevant Third Party patents come to its notice. Neither party
         gives a warranty to the other regarding the infringement of Third Party
         rights by the development, manufacture, use or sale of the Development
         Candidate or the practice of the Myogen Technology or the NIBRI
         Technology, and gives no indemnity against costs, damages, expenses or
         other losses arising out of proceedings brought against the other party
         or any other Person by any Third Party. In the event NIBRI is sued for
         infringement of any rights of any Third Party in the course of its
         development, manufacture, marketing and sale of Development Candidate
         or its use of Myogen Technology in connection therewith, Myogen shall
         extend to NIBRI, at no charge, good faith assistance and support in
         defending such action, and may participate in the conduct of the suit
         at its own expense, but shall otherwise be under no obligation in
         respect thereof. Legal expenses and fees arising from such a legal
         action shall be paid by NIBRI.

                  (b) In the event that the development of Development Candidate
         or the sale of a Drug Product in any country necessarily involves
         working within the scope of a Third Party's patent, which would
         otherwise be infringed by the practice of a Myogen Patent in connection
         with such development or sale, then Myogen will use reasonable efforts
         to obtain required licenses under the Third Party's patents, under
         terms reasonably acceptable to both Myogen and NIBRI, and the terms of
         Section 4.5(c) hereof shall apply; provided that neither Myogen nor
         NIBRI shall be required to accept any license which carries a financial
         obligation which is materially in excess of the range of financial
         obligations customarily associated with comparable non-exclusive
         licenses. If the terms of a required license under a Third Party patent
         do not meet the foregoing requirements and Myogen therefore elects not
         to assume any financial obligation, NIBRI may nonetheless elect to
         obtain the license, to continue sales of Drug Product in such country
         and to pay, itself, any amounts due under such license. If the required
         license is either unavailable or its terms are unacceptable both to
         Myogen and to NIBRI, then NIBRI may elect in its sole discretion to
         discontinue sales of the Drug Product in such country or at its sole
         expense to undertake the



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         defense of a patent infringement action or the prosecution of a
         declaratory judgment action with respect to the Third Party patents.

         9.4. FORCE MAJEURE. Neither party will be in breach hereof by reason of
its delay in the performance of or failure to perform any of its obligations
hereunder, if that delay or failure is caused by strikes, acts of God or the
public enemy, riots, incendiaries, interference by civil or military
authorities, compliance with governmental priorities for materials, or any fault
beyond its control or without its fault or negligence.

         9.5. WAIVER. Any waiver by either party of the breach of any term or
condition of this Agreement will not be considered as a waiver of any subsequent
breach of the same or any other term or condition hereof.

         9.6. SEVERABILITY. Should one or more provision of this Agreement be or
become invalid, then the parties hereto shall attempt in good faith to agree
upon valid provisions in substitution for the invalid provisions, which in their
economic effect come so close to the invalid provisions that it can be
reasonably assumed that the parties would have accepted this Agreement with
those new provisions. If the parties are unable to agree on such valid
provisions, the invalidity of such one or more provisions of this Agreement
shall nevertheless not affect the validity of the Agreement as a whole, unless
the invalid provisions are of such essential importance for this Agreement that
it may be reasonably presumed that the parties would not have entered into this
Agreement without the invalid provisions.

         9.7. GOVERNMENT ACTS. In the event that any act, regulation, directive,
or law of a government within the Territory, including its departments, agencies
or courts, should make impossible or prohibit, restrain, modify or limit any
material act or obligation of NIBRI or Myogen under this Agreement, the party,
if any, not so affected, shall have the right, at its option, to suspend or
terminate this Agreement as to such country, if good faith negotiations between
the parties to make such modifications herein as may be necessary to fairly
address the impact thereof, after a reasonable period of time are not successful
in producing mutually acceptable modifications to this Agreement.



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         9.8. GOVERNMENT APPROVALS. NIBRI or its sublicensees will obtain any
government approval required in the Territory to enable this Agreement to become
effective, or to enable any payment hereunder to be made, or any other
obligation hereunder to be observed or performed. NIBRI will keep Myogen
informed of progress in obtaining any such government approval, and Myogen will
cooperate with NIBRI in any such efforts.

         9.9. EXPORT CONTROLS. This Agreement is made subject to any
restrictions concerning the export of Development Candidate or Myogen Technology
from the United States that may be imposed upon or related to either party to
this Agreement from time to time by the Government of the United States.
Furthermore, NIBRI will not export, directly or indirectly, any Myogen
Technology or any Development Candidate utilizing such Myogen Technology to any
countries for which the United States Government or any agency thereof at the
time of export requires an export license or other governmental approval,
without first obtaining the written consent to do so (of which NIBRI will
promptly inform Myogen) from the Department of Commerce or other agency of the
United States Government when required by applicable statute or regulation.

         9.10. ASSIGNMENT. NIBRI may assign this Agreement, without the consent
of Myogen: (a) to any of its Affiliates; or (b) in connection with the transfer
or sale of all or substantially all of its assets or business or in the event of
its merger or consolidation with another company. Myogen may not assign or
otherwise transfer this Agreement or any of its rights or obligations under this
Agreement without the prior written consent of NIBRI, except, that Myogen may
assign this Agreement to any Person in connection with a transaction which
results in the sale, merger, consolidation, transfer, or other reorganization of
Myogen in which substantially all of the assets of Myogen are transferred or in
which the holders of Myogen's capital stock immediately prior to the transaction
hold less than a majority of the capital stock of the surviving entity after the
transaction; provided that should NIBRI demonstrate with reasonable certainty
that the proposed assignee is a significant competitor of NIBRI or its
Affiliates and Myogen's proposed transaction would cause a material adverse
effect on the commercial potential of the Drug Product, then NIBRI will provide
to Myogen written notice of such determination within [/\#/\] specifying the
reasons for such determination and, at NIBRI's



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election, the option to co-fund and co-promote Drug Products as set forth in
Section 3.5 shall be unavailable to Myogen and such assignee. Any purported
assignment in contravention of this Section 9.10 shall, at the option of the
nonassigning party, be null and void and of no effect. No assignment shall
release either party from responsibility for the performance of any accrued
obligation of such party hereunder. This Agreement shall be binding upon and
enforceable against the successor to or any permitted assignees from either of
the parties hereto.

         9.11. COUNTERPARTS. This Agreement may be executed in duplicate, each
of which shall be deemed to be original and both of which shall constitute one
and the same Agreement.

         9.12. NO AGENCY. Nothing in this Agreement shall be deemed to create an
agency, joint venture, amalgamation, partnership or similar relationship between
Myogen and NIBRI Notwithstanding any of the provisions of this Agreement,
neither party to this Agreement shall at any time enter into, incur, or hold
itself out to Third Parties as having authority to enter into or incur, on
behalf of the other party, any commitment, expense, or liability whatsoever, and
all contracts, expenses and liabilities in connection with or relating to the
obligations of each party under this Agreement shall be made, paid, and
undertaken exclusively by such party on its own behalf and not as an agent or
representative of the other.

         9.13. NOTICE. All communications between the parties with respect to
any of the provisions of this Agreement will be sent to the addresses set out
below or to other addresses as may be designated by one party to the other by
notice pursuant hereto, by prepaid certified mail (which shall be deemed
received by the other party on the seventh business day following deposit in the
mails), or by facsimile transmission or other electronic means of communication
(which shall be deemed received when transmitted), with confirmation by first
class letter, postage pre-paid, given by the close of business on or before the
next following business day:


         if to NIBRI, at:

             Novartis Institutes for BioMedical Research, Inc.
             400 Technology Square
             Cambridge, Massachusetts  02139
             Attention:  Robert L. Thompson, Vice President and General Counsel
             Fax:  (617) 871-3354



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         with a copy to:

             Kirkpatrick & Lockhart LLP
             75 State Street
             Boston, Massachusetts 02109
             Attention:  Eileen Smith Ewing, Esq.
             Fax:  (617) 261-3175

         if to Myogen, at:

             Myogen, Inc.
             7575 West 103rd Avenue
             Westminster, Colorado  80021
             Attention:  J. William Freytag, President and Chief Executive
             Officer
             Fax:  (303) 410-6667

         with a copy to:

             Cooley Godward LLP
             380 Interlocken Crescent, Suite 900
             Broomfield, Colorado  80021
             Attention:  Steven N. Dupont, Esq.
             Fax:  (720) 566-4099

         9.14. HEADINGS. The paragraph headings are for convenience only and
will not be deemed to affect in any way the language of the provisions to which
they refer.

         9.15. AUTHORITY. The undersigned represent that they are authorized to
sign this Agreement on behalf of the parties hereto. The parties each represent
that no provision of this Agreement will violate any other agreement that a
party may have with any other person or company. Each party has relied on that
representation in entering into this Agreement.

         9.16. ENTIRE AGREEMENT. This Agreement contains the entire
understanding of the parties relating to the matters referred to herein, and may
only be amended by a written document, duly executed on behalf of the respective
parties.



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                                       MYOGEN, INC.

                                       By:
                                           -------------------------------------

                                       Title:
                                              ----------------------------------


                                       Date of Signature:
                                                          ----------------------


                                       NOVARTIS INSTITUTES FOR BIOMEDICAL
                                       RESEARCH, INC.


                                       By:
                                           -------------------------------------

                                       Title:
                                              ----------------------------------

                                       Date of Signature:
                                                          ----------------------



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                                  SCHEDULE 1.36

                                LISTED COUNTRIES
--------------------------------------------------------------------------------

                                     [/\#/\]





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<PAGE>

                                  SCHEDULE 1.40

                                 MYOGEN PATENTS
--------------------------------------------------------------------------------

                                     [/\#/\]



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