Document:

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                                                                   EXHIBIT 10.23

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

                                LICENSE AGREEMENT

         This License Agreement ("AGREEMENT") is made as of this 30th day of
June 2003 (the "EFFECTIVE DATE") by and between ABBOTT LABORATORIES, an Illinois
corporation, with its principal office at 100 Abbott Park Road, Abbott Park, IL
60064-6049 ("ABBOTT") and MYOGEN, INC., a Delaware corporation, with its
principal office at 7575 W. 103rd Avenue, Westminster, CO 80021-5426 ("MYOGEN").

                                   WITNESSETH

WHEREAS, Abbott is the holder or licensee of certain patent applications and
patents ("Patents," as more fully defined below) relating to Compound (as
defined below);

WHEREAS, Abbott also possesses proprietary Know-How (as defined below) relating
to Compound; and

WHEREAS, Myogen wishes to obtain, and Abbott wishes to grant to Myogen, an
exclusive license in the Myogen Territory (as defined below) under the Abbott
Technology (as defined below) for the development and commercialization of
Product for use in the Field (as defined below).

NOW, THEREFORE, in consideration of the mutual obligations and promises as set
forth herein, the parties do hereby agree as follows:

1.       DEFINITIONS

         In addition to the terms defined in the other provisions of this
         Agreement, as used in this Agreement, the following terms shall have
         the following respective meanings:

         1.1      "ABBOTT TECHNOLOGY" means the Patents and Know-How, including
                  all Improvements developed by Abbott and Improvements that are
                  jointly developed by Abbott and Myogen pursuant to Article 15.

         1.2      "AFFILIATE" means any corporation, company, partnership, joint
                  venture and/or firm, which controls, is controlled by, or is
                  under common control with either party hereto. For purposes of
                  this definition, control shall mean direct or indirect
                  ownership of more than fifty percent (50%) of the stock or
                  participating shares entitled to vote for the election of
                  directors (but only as long as such ownership exists).

         1.3      "API" means the Compound in an active pharmaceutical form
                  suitable for manufacture of Product.

         1.4      CANCER FIELD means the prophylactic or therapeutic
                  administration to humans or non-human animals as an agent,
                  either alone or in combination with other agents, for the
                  prevention, treatment or palliation of cancer including
                  neoadjuvant,

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

                  adjuvant or supportive care and/or as part of combination with
                  radiotherapy, surgery, chemo-, biologic- or other therapy
                  associated with cancer, including, but not limited to, pain
                  and bone/skeletal complications or indications from bone
                  metastasis.

         1.5      "CO-MARKETING" means the sale by Myogen and Abbott of the same
                  formulation of a Product independently under separate trade
                  names in a particular country.

         1.6      "COMBINATION PRODUCT" means a pharmaceutical product that is
                  comprised in part of API and in part of one or more other
                  pharmaceutically active agents in any configuration,
                  formulation or combination.

         1.7      "COMMERCIALLY REASONABLE EFFORTS" means the level of efforts
                  and resources required to carry out clinical or regulatory
                  development, manufacturing, or commercialization, as
                  applicable, of Product in a manner consistent with the efforts
                  that a similarly situated pharmaceutical company would
                  typically devote to a product of similar market potential,
                  profit potential and strategic value.

         1.8      "COMPOUND" means the compound identified as LU 135252
                  (Darusentan) with the following formula:

                  [GRAPHIC FORMULA]

                  and its racemates, isomers, Prodrugs, active metabolites and
                  any pharmaceutically acceptable salt or complex thereof, in
                  its current and any other formulation, whether made before or
                  after the Effective Date.

         1.9      "CONFIDENTIAL INFORMATION" means any and all information or
                  data relating to the Compound and/or Product which a party
                  discloses to the other party, its employees or
                  representatives, including information that is conceived or
                  reduced to practice during the Term by either party or by a
                  Third Party conducting feasibility and evaluation studies for
                  Myogen, whether in writing, orally or by observation,
                  including, without limitation, all scientific, clinical,
                  technical, commercial, financial and business information and
                  Know-How, and other information or data that is identified as
                  confidential at the time it is communicated. Confidential
                  Information shall not include information or any portion
                  thereof which:

                  (a)      is known to the receiving party at the time of
                           disclosure and documented by written records made
                           prior to the date of this Agreement;

                  (b)      is subsequently disclosed to the receiving party
                           without any obligations of confidence by an
                           unaffiliated third person who has not obtained it
                           directly or indirectly from the other party and who
                           has the right to make such disclosure;

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

                  (c)      becomes patented, published or otherwise part of the
                           public domain; or

                  (d)      is independently developed by or for the receiving
                           party by person(s) having no knowledge of or access
                           to such information and without breach of any
                           confidentiality obligation as evidenced by its
                           written records.

                  (e)      The contents of and the Exhibits to this Agreement
                           shall constitute Confidential Information.

         1.10     "CO-PROMOTION" means the joint promotion of the Product by the
                  parties under the same brand name and label.

         1.11     "CO-PROMOTION AGREEMENT" means the agreement setting forth the
                  terms governing the parties Co-Promotion arrangement, to be
                  negotiated by the Parties upon Abbott's exercise of the
                  Co-Promotion Option.

         1.12     "CO-PROMOTION OPTION" shall have the meaning ascribed to such
                  term in Section 3.1 of this Agreement

         1.13     "CO-PROMOTION TERRITORY" means any country in the Myogen
                  Territory where Abbott has entered into a Co-Promotion
                  Agreement with Myogen.

         1.14     "CRD" means the medical condition commonly known as chronic
                  renal disease.

         1.15     "EFFECTIVE DATE" shall have the meaning ascribed to such term
                  in the opening paragraph of this Agreement.

         1.16     "EMEA" means the European Medicines Evaluation Agency, or any
                  successor thereto.

         1.17     "EUROPE" means all members of the European Union as of the
                  Effective Date.

         1.18     "EU Major Markets" means the following countries:
                   United Kingdom, Spain, France, Italy and Germany.

         1.19     "FIELD" means all human and non-human diagnostic, prophylactic
                  and therapeutic uses of the Compound and/or Product in any
                  formulation or dosage form for any and all indications except
                  therapeutic uses and indications in the Cancer Field.

         1.20     "FIRST COMMERCIAL SALE" means the first sale of Product in the
                  Myogen Territory, after Regulatory Approval, by Myogen, any
                  Affiliates or sublicensees of Myogen, or any contract sales
                  force of Myogen or its Affiliates, to any unaffiliated Third
                  Party as evidenced by the selling party's invoice or other
                  relevant document provided to such Third Party. A sale to an
                  unaffiliated Third Party shall not include quantities
                  delivered solely for research purposes, for clinical trials or
                  quantities distributed as free samples or promotions.

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<PAGE>

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

         1.21     "IMPROVEMENTS" means all additions, developments,
                  modifications, enhancements and adaptations (i) which directly
                  relate to or are used in connection with the Compound and/or
                  Product, or any formulations thereof or additions,
                  developments, modifications, enhancements, improvements and
                  adaptations thereto, and (ii) which are conceived or reduced
                  to practice during the Term. Ownership of Improvements shall
                  be as set forth in Article 15 hereof.

         1.22     "IND" means an investigational new drug application filed with
                  the applicable Regulatory Authority in a country of the Myogen
                  Territory, in order to commence human clinical testing of a
                  drug. An IND, together with all supplemental filings
                  referencing the initial IND filing, shall be deemed one and
                  the same IND for all purposes of this Agreement.

         1.23     "KNOW-HOW" means any proprietary technology, information,
                  method of use, process, technique, idea or invention (other
                  than the Patents) owned, possessed or used by Abbott or its
                  Affiliates as of the Effective Date which is directly related
                  to or used in connection with the Compound and/or Product,
                  including all trade secrets and any other technical
                  information relating to development, manufacture, use or sale
                  of the Compound and/or Product, provided that Abbott continues
                  to have the right to license and/or sublicense to Myogen.

         1.24     "MANUFACTURING AND SUPPLY AGREEMENT" means an agreement
                  between the parties for the manufacture and supply of Compound
                  and/or Product as contemplated and described more fully under
                  Section 6.6(b) below.

         1.25     "Myogen Territory" means all countries of the world.

         1.26     "MYOGEN TRADEMARK" means any trademark registered, owned or
                  chosen for Product by Myogen in any country of the Myogen
                  Territory and the Co-Promotion Territory.

         1.27     "NDA" means an application (whether original, supplementary or
                  abbreviated) to the applicable Regulatory Authority in a
                  country of the Myogen Territory, for approval by such
                  Regulatory Authority, necessary for the commercial sale of
                  Product in such country. An NDA, together with all
                  supplemental filings referencing the initial NDA filing, shall
                  be deemed one and the same NDA for all purposes of this
                  Agreement.

         1.28     "NET SALES" means gross sales of the Product invoiced to
                  unrelated third parties in arm's length transactions, by
                  Myogen or any Myogen Affiliates or sublicensees of Myogen, or
                  any contract sales force of Myogen or its Affiliates,
                  including, but not limited to, pharmaceutical wholesalers,
                  pharmacies, hospitals or dispensing physicians, less any of
                  the following charges or expenses that are incurred in
                  connection with gross sales of the Product during the Term:

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<PAGE>

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

                  (a)      discounts, including cash discounts, customary trade
                           allowances or rebates actually taken, governmental
                           rebates, chargebacks, commissions, and group
                           purchasing management fees for formulary access;

                  (b)      credits or allowances given or made for rejection,
                           recall or return of previously sold Product actually
                           taken;

                  (c)      any tax or government charge, duty or assessment
                           (including any tax such as a value added or similar
                           tax or government charge) levied on the sale,
                           transportation or delivery of Product when included
                           on the invoice or other written document between the
                           parties as payable by the purchaser and collectable
                           by Myogen, its Affiliate or sub-licensee; and

                  (d)      freight, postage, transportation, insurance and
                           duties on shipment of Product when included on the
                           invoice or other written document between the parties
                           as payable by the purchaser and collectable by
                           Myogen, its Affiliates or sublicensees.

         With respect to a Combination Product, Net Sales of such Combination
         Product shall first be calculated in accordance with Net Sales of
         Product above, and then the Net Sales of such Combination Product shall
         be determined on a country-by-country basis as follows:

                           (i)      by multiplying the Net Sales of such
                  Combination Product by the fraction A/(A+B), where A is the
                  average selling price in such country of Product which
                  contains the Compound as its sole active ingredient and B is
                  the total of the average selling prices in such country of
                  pharmaceutical product(s) which contain each of the other
                  active ingredients as their sole active ingredient; or

                           (ii)     if either the average selling price of the
                  Product which contains the Compound as its sole active
                  ingredient or the average selling price of all of the other
                  pharmaceutical products which contain each of the other active
                  ingredients in such Combination Product is not available, by
                  multiplying the Net Sales of such Combination Product by a
                  percentage, determined by mutual agreement of the parties,
                  which represents the proportionate economic value of the
                  Compound relative to the economic value contributed by all
                  other active ingredients in such Combination Product. If the
                  parties cannot agree, then the alternative dispute resolution
                  procedure set forth on Exhibit D shall be used to determine
                  the matter.

         1.29     "PATENTS" means the patent applications and patents listed in
                  Exhibit A hereto and any patents or patent applications
                  derived from those listed in Exhibit A in the sense of making
                  a priority claim to one of those listed patents or patent
                  applications, including foreign equivalents, and any and all
                  substitutions, extensions, additions, reissues,
                  re-examinations, renewals, divisions, continuations,
                  continuations-in-part or supplementary protection certificates
                  and any other patent applications and patents owned by or
                  licensed to (with the right to sublicense) Abbott or its
                  Affiliates during the Term specifically claiming the Compound
                  or Product or solely relating to any Improvements to the
                  Compound derived from Abbott Technology.

         1.30     "PRODRUG" means a pharmaceutical compound which, following
                  administration to a human, is metabolized into the Compound or
                  an Improvement.

         1.31     "PRODUCT" means any formulation containing the Compound or an
                  Improvement to the Compound as an active ingredient for use in
                  the Field.

         1.32     "REGULATORY APPROVAL" or "RA" means all governmental approvals
                  and authorizations necessary for the commercial sale of the
                  Product in a country of the

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

                  Myogen Territory, including, but not limited to, marketing
                  authorization, pricing approval and pricing reimbursement, as
                  applicable.

         1.33     "REGULATORY AUTHORITY" means the United States Food and Drug
                  Administration ("FDA") or any successor entity and its
                  equivalent in other countries of the Myogen Territory,
                  including, but not limited to, the EMEA.

         1.34     "RESISTANT HYPERTENSION" means the indication in which
                  elevated blood pressure in a patient population has been
                  treated with multiple anti-hypertensive therapeutic agents and
                  where the patients' blood pressure has not been adequately
                  controlled. This population includes but is not limited to
                  sub-populations such as patients who also have CRD.

         1.35     "ROYALTY PERIOD" shall have the meaning ascribed to such term
                  in Section 7.4(a) of this Agreement.

         1.36     "TERM" means the period commencing on the Effective Date and
                  terminating as set forth in Article 10 below.

         1.37     "THIRD PARTY" means any entity not a party to this Agreement
                  and not an Affiliate of Myogen or Abbott.

         1.38     "VALID CLAIM" means a claim of an unexpired Patent which
                  covers the manufacture, use or sale of the Product that has
                  not been withdrawn, canceled or disclaimed nor held to be
                  invalid or unenforceable by a court or government agency of
                  competent jurisdiction in an unappealed or unappealable
                  decision.

         1.39     "WORK PLAN" means the preliminary summary of the development
                  plan for the Product, which preliminary summary is attached
                  hereto as Exhibit B, and the final version of which will be
                  completed by Myogen, reviewed by Abbott and attached hereto as
                  the final version of Exhibit B by December 31, 2003.

2.       LICENSE GRANT

         Subject to Abbott's Co-Promotion Rights set out in this Agreement,
         Abbott hereby grants to Myogen an exclusive right and license in the
         Myogen Territory, under the Abbott Technology, for all uses in the
         Field, with the right to grant sublicenses pursuant to Section 6.7
         hereof, to (i) research, develop, modify and improve Compound and
         Product; (ii) apply for and obtain Regulatory Approvals; and (iii) use,
         import/export, market, offer to sell and sell, Product and Compound;
         and (iv) make, or have made, the Compound and Product for use in the
         Field.

3.       ABBOTT'S CO-PROMOTION RIGHTS

         3.1      Abbott shall have the right of first negotiation
                  ("CO-PROMOTION OPTION") to participate with Myogen in the
                  Co-Promotion of Product in the Co-Promotion Territory, under
                  terms and conditions to be negotiated within [/\#/\] of
                  Abbott's exercise of the Co-Promotion Option.

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<PAGE>

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

         3.2      The Co-Promotion Option shall become effective upon Myogen's
                  notice to Abbott that it intends to seek a Co-Promotion
                  arrangement in a particular country or group of countries in
                  the Myogen Territory and shall remain open for a [/\#/\]
                  period thereafter ("CO-PROMOTION OPTION PERIOD"). Abbott may
                  exercise its Co-Promotion Option by providing Myogen with
                  notice of its intention to exercise its Co-Promotion Option
                  before the expiration of the Co-Promotion Option Period. The
                  parties shall have [/\#/\] to conclude the terms of the
                  Co-Promotion arrangement in the country or countries in
                  question. If Abbott fails to give notice of its exercise or
                  its election not to exercise its Co-Promotion Option before
                  the expiration of the Co-Promotion Option Period, Abbott will
                  be deemed to have waived all rights under its Co-Promotion
                  Option. In the event Abbott waives or otherwise fails to
                  exercise its Co-Promotion Option or if the parties are unable
                  to conclude an agreement within the [/\#/\] negotiation
                  period, then Myogen shall be free to enter into such an
                  arrangement with any Third Party in that country or group of
                  countries. If Co-Promotion is not legally permitted in any
                  country of the Co-Promotion Territory, Abbott's right to
                  negotiate as set forth in this Section 3.2 will be limited to
                  Co-Marketing rights in such country or countries, the terms of
                  which shall be negotiated by the parties.

4.       JAPAN OPTION

         4.1      JAPAN OPTION. Myogen grants Abbott a right of first
                  negotiation to become Myogen's exclusive development and
                  commercialization partner of Product in Japan ("JAPAN
                  OPTION").

         4.2      The Japan Option shall become effective [/\#/\] following the
                  enrollment of the first patient in the first clinical trial as
                  outlined in the Work Plan and shall remain open for a sixty
                  (60) day period thereafter ("JAPAN OPTION PERIOD"). Abbott may
                  exercise its Japan Option by providing Myogen with notice of
                  its intention to exercise its Japan Option before the
                  expiration of the Japan Option Period. The parties shall have
                  sixty (60) days to conclude the terms of the development and
                  commercialization arrangement for Japan. If Abbott fails to
                  give notice of its exercise or its election not to exercise
                  its Japan Option before the expiration of the Japan Option
                  Period, Abbott will be deemed to have waived all rights under
                  its Japan Option. In the event Abbott waives or otherwise
                  fails to exercise its Japan Option within the Japan Option
                  Period or if the parties are unable to conclude an agreement
                  within the sixty (60) day negotiation period, then Myogen
                  shall be free to enter into such an arrangement with any Third
                  Party in Japan.

5.       INFORMATION

         5.1      CONVEYANCE OF INFORMATION/INVENTORY.

                  (a)      By June 30, 2003, Abbott shall convey to Myogen or
                           its designee all the information under Abbott's or
                           its Affiliates' control relating to the

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

                           Compound (the "DATA TRANSFER"). Abbott shall use
                           Commercially Reasonable Efforts to ensure that it has
                           located and conveyed all of the information under its
                           and its Affiliates' control and Abbott agrees to
                           immediately convey to Myogen any information which
                           Abbott locates after June 30, 2003. The information
                           to be transferred and conveyed as part of the Data
                           Transfer includes, but is not limited to: (i) all
                           information relating to Patents and Know-How; (ii)
                           worldwide regulatory documentation for the Compound,
                           including, without limitation, complete copies of all
                           existing IND filings for any Product, all supplements
                           thereto and all other regulatory files and FDA
                           correspondence related to any Product; (iii) clinical
                           trial protocols, draft and final clinical reports,
                           case report forms from clinical trials; (iv) safety
                           data, toxicity study reports; (v) data and
                           information related to all indications, doses, and
                           formulations, both actual and proposed, for the
                           Products; (vi) manufacturing protocols, batch records
                           and current standard operating procedures, including,
                           but not limited to, quality analysis and quality
                           control methodologies and standards; (vii) claims
                           related to potential violations of any Third Party
                           rights; and (viii) all collaborative research
                           agreements; in each case, to the extent in the
                           control of Abbott, its Affiliates and agents. For
                           purposes of this Section 5.1, information shall not
                           be deemed under Abbott's and its Affiliates' control
                           if such information is protected by confidentiality
                           agreements with third parties; provided, however,
                           that Abbott shall provide Myogen with notice that
                           such information is subject to third party
                           confidentiality obligations at the time of its
                           identification. With respect to such protected
                           information, Abbott shall use Commercially Reasonable
                           Efforts to obtain the consent of such third parties
                           to release the protected information to Myogen.

                  (b)      By June 30, 2003, Abbott will execute and deliver a
                           letter to the FDA authorizing the transfer of the IND
                           filing for the Compound to Myogen and authorizing
                           Myogen to do and take all actions that are necessary
                           to transfer the IND filings for the Compound in the
                           name of Myogen. In addition, during the [/\#/\] day
                           period following the Effective Date Abbott shall
                           provide at an Abbott location to be identified by
                           Abbott reasonable assistance to Myogen, [/\#/\] to
                           Myogen, to affect the orderly transfer of
                           Product-related development activities and regulatory
                           documents to Myogen provided that Myogen shall be
                           responsible for its own out of pocket expenses.

                  (c)      Abbott will complete, at Abbott's expense, two
                           ongoing studies nearing completion as of the
                           Effective Date, [/\#/\]. Abbott will complete, at
                           Abbott's option, but subject to Myogen's approval of
                           the applicable expenditures, any of the pre-clinical
                           studies identified on

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<PAGE>

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

                           Exhibit C for the Compound, and Myogen will reimburse
                           Abbott for [/\#/\] associated with such studies.

                  (d)      By June 30, 2003, Abbott shall, for the purposes of
                           supplying Myogen with Compound for use in conducting
                           clinical trials and at Myogen's expense, initiate the
                           process of re-testing and re-qualifying the Compound
                           and releasing to Myogen the specified quantities of
                           previously manufactured bulk API (Compound)
                           consisting of approximately [/\#/\] of Compound
                           located at Abbott's Ludwigshafen facility. Abbott
                           shall convert re-qualified Compound into tablet form
                           as well as provide matching placebos at Abbott's
                           [/\#/\] plus Abbott's [/\#/\]of Compound in such
                           tablets [/\#/\] according to a manufacturing,
                           delivery and payment schedule to be mutually agreed
                           by the parties. If Abbott is unable to re-qualify the
                           previously manufactured bulk API, Abbott shall,
                           within a Commercially Reasonable time, manufacture a
                           new batch of API sufficient to allow Myogen to
                           commence its clinical trials at Abbott's [/\#/\].
                           Abbott hereby states that its fully burdened costs
                           for the manufacture of the existing API is [/\#/\].
                           Abbott shall use commercially reasonable efforts to
                           maintain the cost of the bulk API at a cost equal to
                           or less than [/\#/\]. Myogen shall pay Abbott
                           [/\#/\].

                  (e)      Myogen shall, [/\#/\] identify which batches of the
                           existing API they wish Abbott to hold for Myogen's
                           future purchase, and Abbott shall be free to dispose
                           of all batches not so identified. Myogen may purchase
                           quantities of API from time to time on an as-needed
                           basis. Myogen [/\#/\].

                  (f)      Abbott represents and warrants that the Compound,
                           matched placebo and Product conveyed to Myogen under
                           Section 5.1(d) has been or shall be manufactured in
                           accordance with current Good Manufacturing Practices
                           ("CGMP"). Other than the foregoing warranty, any
                           Compound shall be conveyed "AS IS" and "WITH ALL
                           FAULTS," WITHOUT ANY OTHER WARRANTY OF ANY KIND
                           WHATSOEVER, EXPRESS OR IMPLIED, INCLUDING WARRANTIES
                           OF MERCHANTABILITY AND FITNESS FOR PARTICULAR
                           PURPOSE. Myogen shall be responsible for all testing,
                           quality control and certification of such Compound.

6.       FEASIBILITY/EVALUATION/DEVELOPMENT/MANUFACTURING/MARKETING/OTHER

         6.1      FEASIBILITY/EVALUATION STUDIES. Myogen shall use Commercially
                  Reasonable Efforts to evaluate the Compound in accordance with
                  the Work Plan. Myogen shall have sole responsibility for
                  conducting and/or supervising the feasibility and evaluation
                  studies on the Compound as set forth in the Work Plan. Myogen
                  shall provide Abbott with summaries of the feasibility and
                  evaluation studies conducted

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<PAGE>

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

                  by or on behalf of Myogen, including summaries of reports and
                  data generated under such studies, on a semi-annual basis
                  (including at any annual review meeting held pursuant to
                  Section 6.2 below), and all such information shall be treated
                  as Myogen's Confidential Information. Recognizing that certain
                  work to be conducted on behalf of Myogen will be performed by
                  one or more Third Parties and recognizing that such work
                  (e.g., formulations) may involve the patented subject matter
                  of such Third Party, Myogen will use Commercially Reasonable
                  Efforts to: (a) provide in its license with the Third Party
                  that the patented subject matter of such Third Party may be
                  sublicensed to Abbott in the event that the Compound and
                  Product are returned to Abbott under Sections 6.3(b) and
                  Article 10; and (b) negotiate a [/\#/\] with such Third Party.
                  In the event that Myogen is unable to negotiate a royalty-free
                  license/sublicense, Abbott agrees to [/\#/\] thereunder if it
                  elects to practice under such license/sublicense following the
                  return of the Compound and Product under Sections 6.3(b) and
                  Article 10. Myogen agrees to promptly provide Abbott with
                  written notice of the terms of any [/\#/\] prior to entering
                  into any such [/\#/\] with Third Parties, which pertain to the
                  Compound and/or Product, in order for Abbott to have the
                  opportunity to comment on said terms and conditions before
                  Myogen enters into that [/\#/\].

         6.2      REVIEW. Beginning six (6) months following the Effective Date
                  and every six (6) months thereafter while Myogen is developing
                  the Compound, Myogen shall provide Abbott with a written
                  report reviewing the progress of the Work Plan and the results
                  of such work and studies remaining to be completed under the
                  Work Plan, which report shall be deemed Myogen Confidential
                  Information. In the event Abbott so requests, the parties
                  shall meet in person once during each calendar year to discuss
                  these topics. The meeting shall be held at a mutually
                  agreeable time at Myogen's headquarters. Each party shall be
                  responsible for its own costs of attendance.

         6.3      CLINICAL DEVELOPMENT.

                  (a)      Myogen shall use Commercially Reasonable Efforts to
                           develop the Compound in accordance with the Work Plan
                           and not to materially deviate from the time schedule
                           stated therein except as may be dictated by valid
                           scientific, clinical and/or Regulatory circumstances
                           and shall use Commercially Reasonable Efforts to
                           maximize the commercial opportunity of the Compound
                           and Product. Myogen may modify the Work Plan if
                           required to adjust the Work Plan under such
                           circumstances and will communicate such modifications
                           to Abbott. If Myogen requires any other material
                           modification to the Work Plan, it will so notify
                           Abbott within a reasonable time. Myogen shall have
                           sole responsibility for designing, conducting and
                           paying for the cost of the clinical development of
                           Product and shall use Commercially Reasonable Efforts
                           to conduct such

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     10
<PAGE>

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

                           clinical development as set forth below. Abbott
                           hereby agrees that [/\#/\].

                  (b)      In the event Myogen breaches a material obligation
                           under Section 6.3(a) or 6.5(b) of this Agreement,
                           Abbott may then advise Myogen that Abbott believes
                           that Myogen has breached such material obligation and
                           that Abbott is adversely impacted thereby. Upon so
                           advising Myogen, either Party may initiate an
                           alternative dispute resolution procedure ("ADR") as
                           set forth in Exhibit D and request the ADR to rule
                           upon whether Myogen has breached any such material
                           obligation. In the event that the neutral conducting
                           such ADR renders a ruling that Myogen has breached
                           such material obligation and that Abbott was
                           adversely impacted thereby, and Myogen fails to
                           comply with the terms of the neutral's ruling within
                           the time specified therein for compliance (which in
                           no event shall be less than ninety (90) days), or if
                           such compliance cannot be fully achieved by such
                           date, Myogen has failed to commence compliance and/or
                           has failed to use diligent efforts to achieve full
                           compliance as soon thereafter as is reasonably
                           possible, then Abbott's sole remedy shall be the
                           right to terminate this Agreement and the licenses
                           granted hereunder, and to obtain from Myogen a
                           license to Improvements under Section 15.

         6.4      COMMERCIALIZATION.

                  (a)      Myogen shall use Commercially Reasonable Efforts to
                           develop, register and commercialize Product in the
                           U.S. and EU Major Markets. It is the parties'
                           expectation that Myogen will commercialize Product in
                           all commercially viable markets in the Myogen
                           Territories other than the Co-Promotion Territories
                           within [/\#/\] following First Commercial Sale of the
                           Product. If, following such [/\#/\] period, there
                           remain markets outside the Co-Promotion Territories
                           where Myogen is not commercializing Product which
                           Abbott, in its reasonable estimation, believes are
                           commercially viable markets, then the parties shall
                           meet within thirty (30) days of Abbott's written
                           notice for the purpose of developing a mutually
                           agreeable action plan for such under-served markets.
                           If the parties are unable to agree on an action plan,
                           Myogen shall have the option to enlist a marketing
                           partner to assist Myogen in marketing the Product in
                           the underserved markets, or to offer to Abbott the
                           option, for Abbott and its Affiliates, to sell the
                           Product directly in each such country, by paying to
                           Myogen or its sublicensees a reasonable royalty to be
                           mutually agreed by the Parties. Myogen agrees to
                           provide Product to Abbott and its Affiliates for sale
                           in

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED       11
<PAGE>

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

                           each such country at the same delivered [/\#/\] of
                           goods (as evidenced by Myogen's internal records)
                           incurred by Myogen in procuring or manufacturing
                           Product for its own sales plus [/\#/\] and to
                           cooperate with Abbott by, among other things, working
                           with Abbott and its Affiliates to coordinate, in the
                           relevant country, marketing and sales strategies and
                           the development of selling and other materials
                           necessary for the effective sale and marketing of
                           Product in such country consistent with Myogen's
                           global Product marketing strategies. The rights and
                           obligations of the parties with respect to
                           commercialization within the Co-Promotion Territory
                           will be as agreed upon and set forth in the
                           Co-Promotion Agreement.

                  (b)      If there is any material disagreement between the
                           parties concerning whether a market is commercially
                           viable such that Myogen should be commercializing
                           Product in accordance with Section 6.4(a) hereof, or
                           if Myogen reasonably believes that enlisting a
                           marketing partner (including Abbott) to assist it in
                           selling the Product in a particular country will have
                           a substantial negative impact on Myogen's local,
                           regional or global commercial efforts, then the
                           matter may be submitted to ADR. If the neutral
                           conducting such ADR makes a final determination that
                           a market is commercially viable and that Myogen
                           should be commercializing Product in such market, the
                           neutral shall provide Myogen with the opportunity to
                           commercialize Product in such market. If Myogen fails
                           to commercialize Product within the time period
                           prescribed by the neutral (which in no event shall be
                           less than ninety (90) days), then the neutral may
                           issue an order allowing Abbott to terminate Myogen's
                           license with respect to that country.

         6.5      MARKETING/MARKETING PLAN/REGULATORY REVIEWS.

                  (a)      Except as set forth in Articles 3 and 4 above, in the
                           Myogen Territory and subject to Abbott's [/\#/\]
                           rights, if any, Myogen shall have sole responsibility
                           for marketing Product, including entering into any
                           co-marketing and/or co-promotion arrangement. Myogen
                           shall distribute all Product samples in the United
                           States in accordance with the Prescription Drug
                           Marketing Act.

                  (b)      Subject to the terms of any [/\#/\] arrangement
                           between Myogen and Abbott, six months prior to launch
                           in any of the EU Major Markets, the United States or
                           Canada (collectively "Key Markets"), Myogen shall
                           prepare a marketing plan ("Marketing Plan"), with
                           regard to the marketing and sale of the Product. The
                           Marketing Plan shall contain a ten year sales
                           forecast for each indication for the [/\#/\], a
                           detailed summary of the size of the sales force to be
                           utilized in the sale of the Product, and detailed
                           estimate of the promotional spending to be allocated
                           to the promotion of the Product. Myogen shall on a
                           commercially reasonable basis enlist the

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      12
<PAGE>

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

                           services of professional consultants normally used in
                           the development of similar marketing plans for
                           products similar to Product. Abbott shall have the
                           opportunity to review said Marketing Plan
                           sufficiently in advance of its finalization in order
                           to provide comments to said Marketing Plan. Myogen
                           shall ensure that the Marketing Plan is sufficient to
                           maximize the commercial opportunity of Darusentan and
                           shall use Commercially Reasonable Efforts to
                           implement such Marketing Plan.

                  (c)      Myogen shall, at its sole expense and consistent with
                           its obligations under Section 6.4(a), apply for RA's
                           in all countries in the Myogen Territory for the
                           purposes of selling the Product.

         6.6      MANUFACTURING.

                  (a)      Myogen will be solely responsible for and/or will
                           arrange for the manufacture of Compound and/or
                           Product. Abbott shall provide Myogen with the
                           manufacturing protocol for the Compound and/or
                           Product, which protocol shall be considered Abbott
                           Confidential Information. All additional Know-How or
                           Abbott Confidential Information relating to raw
                           materials or precursors to the Compound, and all
                           additional information and documentation in Abbott's
                           or its Affiliates' possession, which are necessary to
                           make Compound and/or Product, shall be transferred to
                           Myogen by June 30, 2003.

                  (b)      If Myogen elects to negotiate terms and conditions
                           with a Third Party manufacturer ("TPM") for the
                           manufacture and supply of the Compound and/or Product
                           to Myogen, Myogen shall first offer Abbott the
                           opportunity to negotiate a Manufacturing and Supply
                           Agreement providing for Abbott to supply Myogen with
                           its requirements of the Compound and Product. The
                           parties shall have [/\#/\] to execute a definitive
                           Manufacturing and Supply Agreement. If the parties
                           are unable to conclude a definite Manufacturing and
                           Supply Agreement, then Myogen shall be free to
                           negotiate such an agreement with a TPM. Myogen shall
                           be solely responsible for all costs and expenses
                           necessary to qualify such TPM. Myogen may provide the
                           manufacturing protocol to the TPM under terms that
                           provide for the protection of Abbott Confidential
                           Information.

         6.7      SUBLICENSING. Subject to Abbott's Co-Promotion rights, Myogen
                  may sublicense its rights under this Agreement, in the Myogen
                  Territory, without obtaining Abbott's prior written consent.
                  Each sublicense shall be in writing and shall include
                  provisions acknowledging that such sublicense is subject to
                  the license granted Myogen under this Agreement, that each
                  sublicensee shall make reports and keep and maintain records
                  of sales to at least the same extent as required under this
                  Agreement, allowing Abbott the same access and audit rights as
                  permitted under this Agreement, and that such sublicense shall
                  be automatically

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED       13
<PAGE>

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

                  terminated upon termination of this Agreement. Myogen shall
                  remain primarily liable for the performance of sublicensees.
                  Myogen shall provide Abbott with a copy of each sublicense
                  agreement.

7.       FINANCIALS

         7.1      EXECUTION LICENSE FEE. Myogen shall pay to Abbott a
                  non-refundable payment of Three Million Dollars ($3,000,000)
                  in cash on the Effective Date.

         7.2      SECOND LICENSE FEE PAYMENT. Myogen shall convey to Abbott a
                  non-refundable payment of Two Million Dollars ($2,000,000) in
                  cash on or before December 31, 2003.

         7.3      MILESTONES. Myogen shall make the following [/\#/\] milestone
                  payments ("Milestones") to Abbott within [/\#/\] of the
                  occurrence of the following events with respect to any
                  Product, regardless of whether or not Myogen has sublicensed
                  any of its rights under this Agreement:

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED       14
<PAGE>

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

REGULATORY FILING MILESTONE                                           PAYMENT

Submission of first filing of an NDA in [/\#/\]:                      [/\#/\]

Submission of first filing seeking Regulatory                         [/\#/\]
Approval in [/\#/\]:

REGULATORY APPROVAL MILESTONE                                         PAYMENT

First Indication:

Upon Regulatory Approval in [/\#/\]:                                  [/\#/\]
Upon Regulatory Approval of an [/\#/\] filing or approval in
[/\#/\]:                                                              [/\#/\]
Upon Regulatory Approval in [/\#/\]:                                  [/\#/\]

Second Indication:

Upon Regulatory Approval in [/\#/\].:                                 [/\#/\]
Upon Regulatory Approval of an [/\#/\] filing or approval in
[/\#/\]:                                                              [/\#/\]
Upon Regulatory Approval in [/\#/\]:                                  [/\#/\]

Third Indication:

Upon Regulatory Approval in [/\#/\]:                                  [/\#/\]
Upon Regulatory Approval of an [/\#/\] filing or approval in
[/\#/\]:                                                              [/\#/\]
Upon Regulatory Approval in [/\#/\]:                                  [/\#/\]

Each milestone payment will be made only once regardless of how many Products
are developed or commercialized or the number of indications for which a Product
has received Regulatory Approval. The total maximum milestone payments and
license fees due Abbott with respect to any and all Products if all of the
foregoing milestones are met will be [/\#/\].

For purposes of this Section 7.3 the term "Indication" with respect to Second
Indication and Third Indication refers to a new indication for the use of an
existing, approved Product for which (a) an additional clinical trial must be
conducted with the Product in order to obtain Regulatory Approval for such use;
and (b) where such Regulatory Approval results in a Regulatory
Authority-approved label expanding the approved uses of the Product.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      15
<PAGE>

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

         7.4      ROYALTY PAYMENTS.

                  (a)      MARGINAL ROYALTY RATE AND ROYALTY PERIOD. Beginning
                           with the First Commercial Sale by Myogen, any
                           Affiliates or sublicensees of Myogen, or any contract
                           sales force of Myogen or its Affiliates, Myogen shall
                           pay to Abbott a royalty on annual aggregate worldwide
                           Net Sales of all Product in accordance with the
                           following schedule:

                           ANNUAL NET SALES            MARGINAL ROYALTY RATE

                           [/\#/\]                            [/\#/\]
                           [/\#/\]                            [/\#/\]
                           [/\#/\]                            [/\#/\]

                           In those countries where no Valid Claim exists at the
                           time of launch of the Product covering the Compound
                           or any Product, Myogen will pay Abbott a royalty of
                           [/\#/\] of Myogen's Net Sales in such country in
                           consideration for licenses to Abbott Know-How
                           relating to the Compound or Product for a period of
                           not more than [/\#/\] after Regulatory Approval of
                           the Product in such country; provided however, if
                           during the Term a Valid Claim comes into existence
                           for any such country, then the normal royalty rate
                           shall apply to sales in that country unless generic
                           competition to the Product exists in that country and
                           the generic product has at least a [/\#/\] market
                           share in that country, in which case the reduced
                           royalty rate shall apply for the [/\#/\] period
                           described above for so long as the generic product
                           has a [/\#/\] market share, provided however, if the
                           market share of the generic product drops below
                           [/\#/\] during such [/\#/\] period, the normal
                           royalty rate shall again apply for so long as the
                           market share of the generic product is below [/\#/\].

                           The obligation of Myogen to pay a full royalty to
                           Abbott shall be on a country-by-country basis and
                           shall continue with respect to Product manufactured
                           or sold in a country until the expiration of the last
                           Patent in such country that contains a Valid Claim
                           (the "ROYALTY PERIOD").

                  (b)      REDUCED ROYALTY. Upon the end of the Royalty Period
                           in any country of the Myogen Territory on a
                           country-by-country basis, Myogen shall have an
                           exclusive, perpetual and irrevocable license under
                           the Abbott Technology in such country of the Myogen
                           Territory, with all of the rights granted under
                           Article 2 hereof, except that, for a period of
                           [/\#/\] from the expiration of the Valid Claim in
                           that country, Myogen shall pay to Abbott a reduced
                           royalty of [/\#/\] of Net Sales of Product in such
                           country (the "REDUCED ROYALTY PERIOD").

                  (c)      ROYALTY REPORTS AND PAYMENTS. Beginning with the
                           First Commercial Sale anywhere in the Myogen
                           Territory, within forty-five (45) days after the end
                           of each calendar quarter, Myogen shall

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<PAGE>

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

                           prepare and deliver to Abbott a report detailing the
                           calculation of Net Sales, on a country-by-country
                           basis, for such just ended quarter along with the
                           calculation of royalties due thereon pursuant to
                           Sections 7.4(a) and (b) above. Each report shall be
                           accompanied by full payment in U.S. dollars of the
                           royalties shown thereon to be due. In the event that
                           conversion from foreign currency is required in
                           calculating a royalty payment hereunder, the exchange
                           rate used shall be the average of the ratio in effect
                           on the first business day and the last business day
                           of the applicable quarter for which royalties are
                           calculated, as reported at the 9:00 am (Central
                           Standard Time) exchange rate according to Reuters, or
                           a substantially similar global publication if Reuters
                           is no longer published. All such quarterly reports
                           shall show sales in the currency of the country in
                           which the sales were made and the currency conversion
                           rate used to arrive at the US dollar amounts shown in
                           the quarterly report.

                  (d)      BOOKS AND RECORDS/AUDIT RIGHTS. Myogen shall keep
                           books and records accurately showing all Products
                           manufactured, used or sold under the terms of this
                           Agreement. The relevant portions of such books and
                           records shall be open to inspection by
                           representatives of Abbott, at Abbott's cost, solely
                           for the purposes of determining the correctness of
                           the royalties payable under this Agreement. Such
                           audit, conducted no more than one time per calendar
                           year, shall be during normal business hours after
                           reasonable advance notice and subject to suitable
                           confidentiality provisions. In the event an audit
                           shows a deficiency to be due, Myogen shall
                           immediately pay such deficiency along with the
                           reasonable costs and expenses of the audit if the
                           deficiency is more than five percent (5%) of the
                           amount due during such audited period. If the audit
                           shows that an excess was paid, Myogen shall be
                           entitled to deduct the amount of such excess from the
                           payment due for the next calendar quarter. Such books
                           and records shall be preserved for a period of at
                           least three (3) years after the date of the royalty
                           payment to which they pertain, and no audit may be
                           conducted with respect to royalties due in any
                           calendar year that is more than two (2) years
                           preceding the calendar year in which the audit is
                           being conducted. Books and records for a given
                           calendar year may only be audited once.

                  (e)      WITHHOLDING TAXES ON ROYALTIES. Where any sum due to
                           be paid to Abbott hereunder is subject to any
                           withholding or similar tax, the parties shall use all
                           reasonable efforts to do all such acts and things and
                           to sign all such documents as will enable them to
                           take advantage of any available exemption, applicable
                           double taxation agreement or treaty. In the event
                           there is no exemption or applicable double taxation
                           agreement or treaty, or if an applicable double
                           taxation agreement or treaty reduces but does not
                           eliminate such withholding or similar tax, Myogen
                           shall pay such

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<PAGE>

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

                           withholding or similar tax to the appropriate
                           government authority, deduct the amount paid from the
                           amount due Abbott and secure and send to Abbott proof
                           of such payment, together with copies of all relevant
                           correspondence with such government authority.

                  (f)      THIRD PARTY ROYALTIES. In the event that Myogen is
                           required to pay royalties to a Third Party under
                           patents in any country owned or controlled by such
                           Third Party, Myogen will be entitled to deduct
                           [/\#/\] of such Third Party royalties against royalty
                           payments due to Abbott; provided that royalties due
                           to Abbott shall not be reduced by greater than
                           [/\#/\] and provided further that a license under
                           such Third Party patents is necessary in order to
                           market any Product in said country. Notwithstanding
                           the foregoing, prior to the Effective Date, Abbott
                           has provided to Myogen a list of any known royalties
                           that are owed to Third Parties as of the Effective
                           Date along with copies of any agreements with Third
                           Parties pursuant to which such royalties are owed,
                           and Myogen shall have no liability with respect to
                           and shall have no obligation to pay any such Third
                           Party royalty obligations incurred with respect to
                           the Product prior to the Effective Date.

                  (g)      LATE PAYMENTS. Any payments due under this Agreement,
                           which are late, shall bear interest at the rate of
                           one percent (I%) per month.

8.       REPRESENTATIONS/WARRANTIES

         8.1      REPRESENTATIONS AND WARRANTIES OF ABBOTT. Abbott represents
                  and warrants that:

                  (a)      it is duly organized, validly existing and in good
                           standing under the laws of Illinois, that it has full
                           corporate power and authority to enter into this
                           Agreement and to carry out its provisions, and that
                           there are no outstanding agreements, assignments or
                           encumbrances in existence that are inconsistent with
                           the provisions of this Agreement;

                  (b)      it is duly authorized to execute and deliver this
                           Agreement and to perform its obligations hereunder
                           and that the execution, delivery and performance of
                           this Agreement by it does not require the consent,
                           approval or authorization of or notice, filing or
                           registration with any governmental agency or
                           Regulatory Authority;

                  (c)      as of the Effective Date, to the best of Abbott's
                           knowledge, (i) it has sufficient rights under the
                           Abbott Technology necessary to grant the rights
                           specified in this Agreement and to perform its
                           obligations hereunder; (ii) there are no claims,
                           judgments or settlements against or owed by it
                           relating to the Abbott Technology; (iii) the exercise
                           of Myogen's rights to

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

                           the Compound under this Agreement or Myogen's use of
                           the Abbott Technology under this Agreement will not
                           infringe any intellectual property rights of a Third
                           Party with the exception of infringement arising from
                           the use of Compound or Abbott Technology in
                           combination with the technology of a Third Party and
                           such infringement would have been avoided without
                           such combination; (iv) the material provided to
                           Myogen concerning the manufacturing process for the
                           Compound as it relates to process historical cost,
                           historical yield and historical quality are accurate
                           in all material respects; (v) there are no known
                           adverse events that have not been described in the
                           documents provided to Myogen or the applicable
                           Regulatory Authority; (vi) Abbott has exerted
                           Commercial Reasonable Efforts to gather and convey to
                           Myogen all documents in Abbott's or its Affiliates'
                           possession and notices from Regulatory Authorities as
                           part of the Data Transfer described in Article 5.1
                           (a); and (vii) Exhibit A includes the relevant
                           Patents necessary to market and sell the Product as
                           contemplated in the Work Plan.

                  (d)      as of the Effective Date, to the best of Abbott's
                           knowledge, (i) none of the Patents are invalid or
                           unenforceable, (ii) it has complied in all material
                           respects with all applicable laws and regulations in
                           connection with the preparation and submission of any
                           filings with any Regulatory Authority; (iii) it has
                           filed with applicable Regulatory Authorities all
                           required and material notices, supplemental
                           applications and annual or other reports, including
                           adverse experience reports, with respect to the
                           Compound; and (iv) there is no pending or overtly
                           threatened action by the Regulatory Authorities that
                           will have a material adverse effect on the timing of
                           a Regulatory Approval of the Compound or any
                           Products.

         8.2      REPRESENTATIONS AND WARRANTIES OF MYOGEN. Myogen represents
                  and warrants that it is duly organized, validly existing and
                  in good standing under the laws of Delaware, that it has full
                  corporate power and authority to enter into this Agreement and
                  to carry out its provisions, and that there are no outstanding
                  agreements, assignments or encumbrances in existence that are
                  inconsistent with the provisions of this Agreement. Myogen
                  further represents and warrants that it is duly authorized to
                  execute and deliver this Agreement and to perform its
                  obligations hereunder, and that the execution, delivery and
                  performance of this Agreement by it does not require the
                  consent, approval or authorization of or notice, filing or
                  registration with any governmental agency or Regulatory
                  Authority.

         8.3      INDEMNIFICATION BY MYOGEN. Myogen shall indemnify and hold
                  Abbott, its Affiliates and their directors, officers,
                  employees and agents harmless from and against any and all
                  liabilities, actions, suits, claims, demands, prosecutions,
                  damages, costs, expenses or money judgments finally awarded
                  (including

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                                 DOCUMENT, MARKED BY BRACKETS, IS FILED WITH THE
                                  SECURITIES AND EXCHANGE COMMISSION PURSUANT TO
                             RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                  reasonable legal fees) (collectively, "LIABILITIES") incurred
                  by or instituted or rendered against Abbott to the extent such
                  Liabilities result from a Third Party claim arising from
                  product liability claims or from the willful misconduct or the
                  negligent acts or omissions of Myogen or its Affiliates or
                  Myogen's material breach of this Agreement, except to the
                  extent such Third Party claims arise out of the negligence or
                  willful misconduct of Abbott, its Affiliates and their
                  directors, officers, employees and agents, or the material
                  breach of this Agreement or the Manufacturing and Supply
                  Agreement, if any, by Abbott, its Affiliates and their
                  directors, officers, employees and agents, and provided that
                  Abbott gives Myogen prompt notice in writing of any such claim
                  or lawsuit and permits Myogen to undertake sole control of the
                  defense and settlement thereof at Myogen's expense. In any
                  such claim or lawsuit:

                  (a)      Abbott will cooperate in the defense by providing
                           access to witnesses and evidence available to it.
                           Abbott shall have the right to participate, at its
                           expense, in any defense to the extent that in its
                           reasonable judgment Abbott may be prejudiced by
                           Myogen's sole defense thereof.

                  (b)      With respect to this Agreement, Abbott shall not
                           settle, offer to settle or admit liability in any
                           claim or suit in which Abbott intends to seek
                           indemnification by Myogen without the written consent
                           of the CEO, COO or CFO of Myogen.

         8.4      INDEMNIFICATION BY ABBOTT. Abbott shall indemnify and hold
                  Myogen, its Affiliates and their directors, officers,
                  employees and agents harmless from and against any and all
                  Liabilities, incurred by or instituted or rendered against
                  Myogen to the extent such Liabilities result from a Third
                  Party claim arising from the willful misconduct or the
                  negligent acts or omissions of Abbott or its Affiliates or
                  Abbott's material breach of this Agreement, except to the
                  extent such Third Party claims arise out of the negligence or
                  willful misconduct of Myogen, its Affiliates and their
                  directors, officers, employees and agents, or the material
                  breach of this Agreement by Myogen, its Affiliates and their
                  directors, officers, employees and agents, and provided that
                  Myogen gives Abbott prompt notice in writing of any such claim
                  or lawsuit and permits Abbott to undertake sole control of the
                  defense and settlement thereof at Abbott's expense. In any
                  such claim or lawsuit:

                  (a)      Myogen will cooperate in the defense by providing
                           access to witnesses and evidence available to it.
                           Myogen shall have the right to participate, at its
                           expense, in any defense to the extent that in its
                           reasonable judgment Myogen may be prejudiced by
                           Abbott's sole defense thereof

                  (b)      With respect to this Agreement, Myogen shall not
                           settle, offer to settle or admit liability in any
                           claim or suit in which Myogen intends to seek

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      20
<PAGE>

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

                           indemnification by Abbott without the written consent
                           of a duly authorized officer of Abbott.

         8.5      REPORTABLE OCCURRENCES. Each party warrants that it shall
                  advise the other promptly of any occurrence, which is reported
                  or reportable by it to the Regulatory Authorities relating in
                  any way to the Compound or the Product.

         8.6      LIMITATION. EXCEPT FOR THE EXPRESS WARRANTIES IN THIS ARTICLE
                  8, NEITHER PARTY MAKES ANY WARRANTIES, EXPRESS OR IMPLIED, IN
                  FACT OR BY OPERATION OF LAW, STATUTORY OR OTHERWISE. EACH
                  PARTY SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTY OF
                  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. EXCEPT
                  FOR VIOLATIONS OF ARTICLE 9 AND AMOUNTS FINALLY AWARDED FOR
                  INDEMNIFICATION FOR THIRD PARTY LIABILITIES UNDER SECTIONS 8.3
                  AND 8.4 ABOVE, NEITHER PARTY SHALL BE LIABLE TO THE OTHER
                  PARTY HERETO FOR ANY SPECIAL, CONSEQUENTIAL, EXEMPLARY OR
                  INCIDENTAL DAMAGES (INCLUDING LOST OR ANTICIPATED PROFITS
                  RELATING TO THE SAME) ARISING FROM ANY CLAIM RELATING TO THIS
                  AGREEMENT, WHETHER SUCH CLAIM IS BASED ON CONTRACT, TORT
                  (INCLUDING NEGLIGENCE) OR OTHERWISE, EVEN IF AN AUTHORIZED
                  REPRESENTATIVE OF SUCH PARTY IS ADVISED OF THE POSSIBILITY OR
                  LIKELIHOOD OF SAME.

9.       CONFIDENTIALITY AND NON-DISCLOSURE

         9.1      NONDISCLOSURE. Neither party shall use or disclose any
                  Confidential Information received by it from the other party
                  pursuant to this Agreement without the prior written consent
                  of the other. This obligation will continue for a period of
                  seven (7) years after termination of this Agreement or
                  expiration of the Term, whichever is earlier. Subject to the
                  exceptions immediately below, Abbott shall hold in confidence
                  and shall not directly or indirectly disclose or provide to
                  any Third Party information pertaining to the Compound or
                  Abbott Technology without Myogen's prior written consent. The
                  parties recognize that pursuant to Articles 3 and 4, Abbott
                  may be involved in marketing and selling the Compound and
                  Product in the Co-Promotion Territory. Abbott shall be
                  permitted to disclose information pertaining to the Compound
                  and the Abbott Technology to the extent necessary for Abbott
                  to perform its obligations under this Agreement, including,
                  but not limited to, its Co-Promotion activities, and only if
                  the recipient of such information is under a duty of
                  confidentiality to Abbott.

         9.2      RESTRICTION. Each party shall restrict dissemination of
                  Confidential Information to those of its employees,
                  contractors, agents and sublicensees (if any) who have an
                  actual need to know and have a legal obligation to protect the
                  confidentiality of such Confidential Information. All
                  Confidential Information disclosed by one

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      21
<PAGE>

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

                  party to the other shall remain the sole property of the
                  disclosing party and neither party shall obtain any right of
                  any kind to the Confidential Information disclosed, except as
                  granted under this Agreement.

         9.3      RESTRICTION EXEMPTIONS. Nothing contained in this Article 9
                  shall be construed to restrict the parties from using or
                  disclosing Confidential Information solely to the extent and
                  solely as required:

                  (a)      for regulatory, tax or customs reasons;

                  (b)      by court order or other governmental order or written
                           request, provided in each case the party disclosing
                           information promptly informs the other and uses its
                           best efforts to limit the disclosure and to maintain
                           confidentiality to the maximum extent possible and
                           permits the other party to attempt by appropriate
                           legal means to limit such disclosure; or

                  (c)      to perform acts permitted by this Agreement,
                           including (i) disclosure by Myogen to third parties
                           undertaking feasibility and evaluation studies,
                           clinical trials and the like on behalf of Myogen, so
                           long as such third parties are under a legal
                           obligation to Myogen to protect the confidentiality
                           of such Confidential Information, or (ii) disclosure
                           by Myogen to sublicensees, so long as such
                           sublicensees are under a legal obligation to Myogen
                           to protect the confidentiality of such Confidential
                           Information, or (iii) disclosure by Myogen in
                           connection with the marketing and commercial sale of
                           Product, or (iv) disclosure by Myogen to the extent
                           required by law; and (v) disclosure by Abbott in
                           connection with its Co-Promotion activities, if any.

10.      TERM AND TERMINATION

         10.1     This Agreement shall continue in effect unless and until
                  terminated as provided in this Section 10 or in Section
                  6.3(b). Upon the end of the Royalty Period in any country of
                  the Myogen Territory, Myogen shall have an exclusive, subject
                  to Abbott's Co-Promotion Rights, perpetual and irrevocable
                  license under the Abbott Technology, with all of the rights
                  granted under Article 2 hereof, and without any further
                  obligation to Abbott, except for the payment obligations
                  accruing prior to such date and the indemnification
                  obligations under Section 8.3, and except for any obligation
                  to pay a reduced royalty for the Reduced Royalty Period, as
                  provided in Section 7.4(b) hereof.

         10.2     If, after January 1, 2004, Myogen determines in its reasonable
                  scientific and commercial judgment that the Compound does not
                  have an acceptable profile or a reasonable likelihood of
                  commercial success, or that it is economically or technically
                  impractical for Myogen to continue developing and marketing
                  the Product, Myogen shall have the right to terminate this
                  Agreement upon ninety

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      22
<PAGE>

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

                  (90) days written notice, at the end of which the termination
                  shall be effective. Upon such termination, Myogen shall pay
                  all payments and royalties which may have become due prior to
                  the effective date of such termination, including, but not
                  limited to, the Second License Fee Payment provided for under
                  Section 7.2, and Myogen shall assign and deliver, and Abbott
                  shall be entitled to retain for its own use, all studies and
                  information relating to the Compound. Myogen shall transfer
                  all RA's held in its name and Abbott shall be granted a
                  license to all Improvements as set forth in Section 15 hereof.
                  In addition, Myogen shall continue to be responsible for any
                  milestones obtained by Myogen (or its sublicensee) with
                  respect to the Product thereafter notwithstanding Myogen's
                  earlier termination under this Section 10.2.

         10.3     Either party may terminate this Agreement by giving to the
                  other party prior written notice of not less than thirty (30)
                  days in the case of a monetary breach and of not less than
                  ninety (90) days in the event the other party shall commit a
                  non-monetary material breach of this Agreement (other than an
                  alleged breaches of Sections 6.3(a) or 6.5(b) or Section
                  6.4(a), in which event the provisions of Sections 6.3(b) and
                  Section 6.4(b), respectively, shall apply), and such breaching
                  party (or that party's sublicensee) shall fail to cure, or
                  commence action to cure, such breach during such thirty (30)
                  or ninety (90) day period, as applicable. In the case of a
                  non-monetary breach (other than an alleged breaches of
                  Sections 6.3(a) or 6.5(b) or Section 6.4(a), the cure period
                  may be extended for such longer period as may reasonably be
                  necessary if cure is not reasonably possible within the
                  initial ninety (90) day period, provided the breaching party
                  continues its diligent efforts to cure. No such cancellation
                  and termination shall release the breaching party from any
                  obligations hereunder incurred prior thereto. In the event of
                  a dispute whether a material breach has occurred, the
                  existence of material breach shall be determined using the ADR
                  procedure set forth in Exhibit D. A party's right to terminate
                  this Agreement shall only apply if the breaching party fails
                  to cure such breach in the manner required by the final
                  judgment of the ADR hearing. In the event that this Agreement
                  is terminated for Myogen's material breach, Abbott shall be
                  entitled to retain for its own use all funds previously paid
                  by Myogen, Myogen shall pay all payments and royalties which
                  may have become due prior to the effective date of such
                  termination, including, but not limited to, the Second License
                  Fee Payment provided for under Section 7.2, and Myogen shall
                  assign and deliver, and Abbott shall be entitled to retain for
                  its own use, all studies and information relating to the
                  Compound, Myogen shall transfer all RA's held in its name and
                  Abbott shall be granted a license to all Improvements
                  generated hereunder as set forth in Section 15 hereof. In the
                  event this Agreement is terminated for Abbott's material
                  breach, Myogen shall be entitled to retain for its own use all
                  studies, information and Improvements generated hereunder, no
                  license to Improvements shall be granted to Abbott under
                  Section 15 hereof and Abbott shall be obligated pay any
                  amounts that became payable pursuant to this Agreement prior
                  to the termination date.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      23
<PAGE>

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

         10.4     Either party may terminate this Agreement on thirty (30) days
                  notice if the other party passes a resolution or the court
                  makes an order for its winding up; or has a receiver or
                  administrator appointed over its business or all of its
                  assets; or is or becomes bankrupt; or ceases its business
                  operations. In the event that this Agreement is terminated
                  under this Section 10.4, subject to the other terms of this
                  Agreement, the terminating party shall be entitled to the
                  assignment and delivery of, and shall be entitled to retain
                  for its own use all studies, information and Improvements
                  (subject to the license set forth in Section 15 as it concerns
                  Abbott) generated hereunder. Notwithstanding the bankruptcy or
                  insolvency of Abbott or the impairment of performance by
                  Abbott of its obligations under this Agreement as a result of
                  bankruptcy or insolvency of Abbott, Myogen shall be entitled
                  to retain the licenses granted herein, without any further
                  obligation to Abbott other than the payment obligations under
                  Article 7.

         10.5     Termination of this Agreement shall be without prejudice to
                  any rights of either party against the other which may have
                  accrued up to the date such termination becomes effective.

         10.6     All causes of action accruing to either party under this
                  Agreement shall survive expiration or termination of this
                  Agreement for any reason.

         10.7     Upon any termination or expiration of this Agreement, each
                  party shall promptly return to the other party all written
                  Confidential Information of the other party, and all copies
                  thereof (retaining one copy of the Confidential Information of
                  the other in its confidential files for archival purposes
                  only), which is not covered by a paid-up license or other
                  rights specified herein surviving such termination or
                  expiration.

         10.8     In the event the Myogen license in Article 2 hereof is
                  terminated for any country due to an uncured material breach
                  by Myogen, Myogen agrees to provide Product to Abbott and/or
                  its Affiliates, or their designee, for sale in each such
                  country at the same fully burdened delivered cost of goods (as
                  evidenced by Myogen's internal records) incurred by Myogen in
                  procuring or manufacturing Product for its own sales and to
                  cooperate with Abbott, or its designee, by, among other
                  things, coordinating marketing and sales strategies consistent
                  with Myogen's global Product marketing strategies, clinical
                  studies and development plans.

11.      INFRINGEMENT OF PATENTS BY THIRD PARTY. In the event of an actual or
         suspected infringement of a Patent by a Third Party, the following
         shall apply:

         11.1     NOTICE. Each party shall give the other written notice if one
                  of them becomes aware of any infringement by a Third Party of
                  any Patent. Upon notice of any such infringement, the parties
                  shall promptly consult with one another with a view toward
                  reaching agreement on a course of action to be pursued.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      24
<PAGE>

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

         11.2     ABBOTT'S RIGHT TO BRING INFRINGEMENT ACTION.

                  (a)      ABBOTT ELECTION. If a Third Party infringes any
                           Patent, Abbott shall have the right, but not the
                           obligation, to institute and prosecute an action or
                           proceeding to abate such infringement and to resolve
                           such matter by settlement or otherwise.

                           (i)      Abbott shall notify Myogen of its intention
                                    to bring an action or proceeding prior to
                                    filing the same and in sufficient time to
                                    allow Myogen the opportunity to discuss with
                                    Abbott the choice of counsel for such
                                    matter. Abbott shall keep Myogen informed of
                                    material developments in the prosecution or
                                    settlement of such action or proceeding.
                                    Abbott shall be responsible for all fees and
                                    expenses of any action or proceeding against
                                    infringes which Abbott initiates. Myogen
                                    shall cooperate fully [/\#/\], including
                                    executing and making available such
                                    documents as Abbott may reasonably request,
                                    and Myogen may, at its option or at the
                                    request of Abbott, join such action as
                                    co-plaintiff or party plaintiff if legally
                                    permissible or if the maintenance of the
                                    action or proceeding requires the same. In
                                    the event Myogen joins such action or
                                    proceeding at its election, or at the
                                    request of Abbott, it may be represented by
                                    its own counsel [/\#/\].

                           (ii)     If Abbott elects not to exercise such right,
                                    and the parties disagree on the utility of
                                    bringing an action against an alleged
                                    infringer, then the parties shall submit
                                    their disagreement to a mutually agreeable
                                    Third Party attorney with experience in
                                    patent litigation in the country of
                                    infringement for resolution. If the Third
                                    Party attorney decides that an infringement
                                    action has a reasonable chance of success,
                                    then Abbott shall be obligated to institute
                                    an action or proceeding in accordance with
                                    Section 11.2(a)(i) above. If the Third Party
                                    attorney decides that an infringement action
                                    does not have a reasonable chance of
                                    success, then no action shall be brought by
                                    either party unless Abbott elects within ten
                                    (10) days of the neutral's decision to
                                    institute such an action or proceeding (or
                                    except as otherwise provided in accordance
                                    with Section 11.2(a)(iii) below).

                           (iii)    If Myogen reasonably believes there is
                                    substantial merit to bringing such an action
                                    notwithstanding the neutral's decision
                                    pursuant to Section 11.2(a)(ii) above; or if
                                    Abbott elects to bring such action but
                                    delegates the authority to institute and
                                    prosecute such action or proceeding to
                                    Myogen, Myogen shall have the right to
                                    institute and prosecute such action or
                                    proceeding to abate such

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     25
<PAGE>

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

                                    infringement and to resolve such matter by
                                    settlement or otherwise. Abbott shall
                                    cooperate fully by joining as a party
                                    plaintiff if reasonably requested to do so
                                    by Myogen or if required to do so by law to
                                    maintain such action and by executing and
                                    making available such documents as Myogen
                                    may reasonably request. Abbott may be
                                    represented by counsel in any such action,
                                    [/\#/\].

                           (b)      ABBOTT'S USE OF PROCEEDS. All amounts of
                                    every kind and nature recovered from an
                                    action or proceeding of infringement brought
                                    by Abbott shall belong to Abbott, and shall
                                    be used first to reimburse Abbott for its
                                    documented and actual costs of prosecution,
                                    including attorneys' fees, expert fees and
                                    all other related expenses, second to
                                    reimburse Myogen for its documented and
                                    actual costs if it is represented by counsel
                                    in the proceeding. If such damage award is
                                    based upon a finding of Myogen's lost sales,
                                    the balance of the amount awarded as
                                    compensatory damages shall, beyond the costs
                                    incurred by Abbott and Myogen for their
                                    respective participations in the action or
                                    proceeding, shall first be used to provide
                                    Abbott the royalty it would have received if
                                    the lost sales had been licensed sales of
                                    Myogen under Section 7.4(a) hereinabove, and
                                    then the parties shall [/\#/\] unless the
                                    award is based upon lost profits of Myogen
                                    and Myogen participated as a party. In such
                                    case, Myogen shall be entitled to [/\#/\] of
                                    said remainder. Any exemplary damages
                                    awarded shall be [/\#/\] between Myogen and
                                    Abbott; [/\#/\].

                           (c)      MYOGEN'S USE OF PROCEEDS. All amounts of
                                    every kind and nature recovered from an
                                    action or proceeding of infringement brought
                                    by Myogen [/\#/\], and shall first be used
                                    to reimburse Myogen for its documented and
                                    actual costs of prosecution, second to
                                    reimburse Abbott for its documented and
                                    actual costs if it is represented by counsel
                                    in the proceedings, and the balance shall be
                                    considered Net Sales under this Agreement
                                    and subject to royalty obligation under
                                    Section 7.4.

12.      INFRINGEMENT OF THIRD PARTY RIGHTS; MYOGEN DEFENSE OF SUIT. If Abbott,
         its Affiliates, Myogen, its Affiliates, sublicensees, distributors or
         other customers are sued or threatened with suit by a Third Party
         alleging infringement of patents or other intellectual property rights
         that are alleged to cover the manufacture, use, sale, import, export or
         distribution of one or more Products, Abbott or Myogen, whichever is
         relevant, will promptly notify the other in writing and provide a copy
         of the lawsuit or claim. Myogen shall control the defense in any such
         claim or suit. Myogen shall keep Abbott timely informed of material
         developments in the defense of such claim or suit. If Myogen expends
         any amounts in connection with any Third Party claim of infringement or
         misappropriation, or is required to pay a royalty or other amount to a
         Third Party for the manufacture, use, sale, import, export or
         distribution of one or more Products in the Myogen Territory as a
         result of a final judgment or settlement, such amounts shall be

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     26
<PAGE>

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

         [/\#/\], but only where such claim, judgment or settlement arises out
         of Myogen's practice of a Patent or use of the Abbott Technology
         pursuant to the license granted under Article 2 of this Agreement
         except where such claim, judgment or settlement alleges an infringement
         arising from the practice of a Patent or use of the Abbott Technology
         in combination with the technology of a Third Party and such
         infringement would have been avoided without such combination. Abbott
         shall fully cooperate with Myogen in the defense of any such action at
         Abbott's expense. Myogen shall have the right to settle any such suit,
         including the right to grant one or more sublicenses with Abbott's
         prior written approval, which approval shall not unreasonably be
         withheld, provided that Myogen shall not otherwise have the right to
         surrender, limit or adversely affect any rights to the Patents. The
         terms of this Article 12 shall not apply to or affect Abbott's
         indemnity obligation for a breach of Section 8.1(c).

13.      PATENT PROSECUTION AND MAINTENANCE; PATENT COSTS: PATENT TERM
         EXTENSION.

         13.1     DISCLOSURE OF PATENTS/APPLICATIONS TO MYOGEN. Within thirty
                  (30) days of Myogen's request, Abbott shall provide Myogen a
                  list of Patents and patent applications in a given Patent
                  family. If, following Myogen's receipt of such list(s), Myogen
                  requests additional information, Abbott shall provide to
                  Myogen the complete text of, and all other information in its
                  possession or control directly related to (a) all patent
                  applications included in the given Patent family filed
                  anywhere in the Territories, and (b) all patents included in
                  the given Patent family as well as all information in
                  Abbott's, its Affiliates and its patent counsel's possession
                  concerning the institution or possible institution of any
                  interference, opposition, reexamination, reissue, revocation,
                  nullification or any official proceeding involving an issued
                  patent included in the given Patent family a[nywhere in the
                  Myogen Territory.

         13.2     PROSECUTION AND MAINTENANCE. Abbott shall be solely
                  responsible for the preparation, filing, prosecution and the
                  associated costs incurred in connection with maintenance of
                  the Patents (except for the case family including [/\#/\]
                  which is the responsibility of BASF AG; provided always that
                  Abbott shall use Commercially Reasonable Efforts to cause BASF
                  AG to defend or prosecute the case family as necessary) in
                  Abbott's name, including oppositions and interferences,
                  subject to Myogen's right to assume such duties in the event
                  Abbott reasonably fails to adequately prepare, file, prosecute
                  and maintain the Patents. By June 30, 2003, Abbott shall
                  inform BASF AG of Abbott's desire to have the Patent family
                  for which BASF AG has responsibility transferred to Abbott and
                  Abbott shall use commercially reasonable efforts to have BASF
                  AG agree to such transfer to Abbott within a reasonable time
                  after the Effective Date, and upon such transfer such Patents
                  will be subject to the same terms and conditions of this
                  Agreement as the Patents for which Abbott has responsibility
                  as of the Effective Date. Abbott and Myogen shall consult and
                  cooperate with each other, and Abbott shall keep Myogen
                  reasonably informed with respect to the prosecution

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      27
<PAGE>

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

                  and maintenance of the Patents hereunder, including the case
                  family which is the responsibility of BASF AG. In this regard
                  Abbott shall exercise its rights under its license from BASF
                  AG for this Patent family such that Myogen shall have the
                  opportunity to participate in the preservation of these Patent
                  rights if it chooses to do so. In connection with its duties
                  under this Section 13.2, Abbott will provide Myogen with: (a)
                  copies of all material documents received or prepared by
                  Abbott in the prosecution and maintenance of the Patents; (b)
                  advance written notice to the extent reasonably practical of
                  any action or proceeding relating to any Patent; and (c) a
                  bi-annual report on the status of prosecution of all Patents.
                  Abbott shall provide copies in a timely manner to allow Myogen
                  an opportunity, if it so elects, to review and comment on
                  Abbott's proposed patent strategy. If Myogen determines, upon
                  advice of its patent counsel, that further prosecution actions
                  with respect to an existing application within the Patents or
                  a reexamination, reissue, interference and action under 35 USC
                  Paragraph 146 or other official proceeding involving an issued
                  Patent anywhere in the Myogen Territory is required to ensure
                  the enforceability of such Patent or adequate claim coverage
                  within such Patents, Abbott shall have the right and sole
                  responsibility for conducting such prosecution action or
                  instituting such proceeding. If Abbott elects not to exercise
                  such right, then Myogen shall have the right and sole
                  responsibility for the pursuit of such activities, and Abbott
                  shall cooperate with Myogen and provide Myogen with all
                  necessary information to conduct such activities. Inasmuch as
                  the Patents cover other compounds not licensed to Myogen
                  hereunder, Abbott warrants that it will not take any action
                  with respect to the Patents, which would have a material
                  adverse effect on the patent coverage of the Compound.

         13.3     PATENT EXTENSIONS. Abbott shall have the right and sole
                  responsibility for obtaining patent term extensions under the
                  provisions of 35 USC Paragraph 156 for any U.S. Patent and for
                  non-U.S. Patents under similar provisions of law of other
                  countries involving a Product which has obtained Regulatory
                  Approval. Myogen shall cooperate with Abbott and provide
                  Abbott with all necessary information to obtain such
                  extensions. If Abbott elects not to exercise such right,
                  Myogen may file for such extension at its own expense, and
                  Abbott shall cooperate with Myogen and provide Myogen with all
                  necessary information to obtain such extensions.

14.      TRADEMARK. Myogen may select any Trademark or Trademarks for the
         Product in the Myogen Territory including the Co-Promotion Territory,
         ("MYOGEN TRADEMARKS"). All costs related to the selection and
         maintenance of the Myogen Trademark(s) shall be borne by Myogen. The
         Myogen Trademark(s) shall be owned by Myogen, and Abbott shall have no
         claims or rights in or to the Myogen Trademark(s), except such right as
         may be necessary for Abbott to commercialize Product following a
         termination under Sections 10.2, 10.3 or 10.4 above, and/or to fulfill
         its Co-Promotion activities in the Co-Promotion Territory.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED      28
<PAGE>

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

15.      IMPROVEMENTS. All Improvements made solely by Myogen and/or its
         Affiliates hereunder shall be the sole and exclusive property of Myogen
         ("MYOGEN IMPROVEMENTS"). All Improvements made solely by Abbott and/or
         its Affiliates ("ABBOTT IMPROVEMENTS") shall become part of the Abbott
         Technology, subject to the license to Myogen set forth in Article 2
         hereof. All Improvements made jointly by employees or others acting on
         behalf of Abbott and Myogen (or their Affiliates) hereunder shall be
         jointly owned by Abbott and Myogen ("JOINT IMPROVEMENTS"), without a
         duty of accounting to the other, to the extent such individuals would
         be considered "joint inventors" within the meaning of the U.S. patent
         laws. Each party shall take all necessary actions, including executing
         documents of assignment, to vest title to all Joint Improvements
         (including all intellectual property rights therein) with both parties.
         With respect to patents resulting from Joint Improvements, the parties
         shall select a mutually agreeable Third Party attorney to prepare,
         file, prosecute and maintain such patents. The Third Party attorney
         shall consult and apprise each party equally and both parties shall
         share 50/50 the costs and fees of employing such Third Party attorney.
         Abbott's interest in such Joint Improvements shall be subject to the
         license granted to Myogen under Article 2 hereof and subject to the
         terms and conditions of this Agreement. In the event this Agreement is
         terminated by Abbott for any reason, as set forth in Article 10, or by
         Myogen under Section 10.2, all Myogen improvements shall be exclusively
         licensed to Abbott solely for use with the Compound and Product on a
         worldwide basis on terms to be mutually agreed to by the parties after
         good faith negotiations, and Myogen retains all rights in and to any
         Myogen Improvements for any and all other uses.

16.      MISCELLANEOUS.

         16.1     FORCE MAJEURE. If the performance by either party of any of
                  its obligations under this Agreement shall be prevented by
                  circumstances beyond its reasonable control, which could not
                  have been avoided by the exercise of reasonable diligence,
                  then such party shall be excused from the performance of that
                  obligation for the duration of the event. The affected party
                  shall promptly notify the other party in writing should such
                  circumstances arise, give an indication of the likely extent
                  and duration thereof, and shall use commercially reasonable
                  efforts to resume performance of its obligations as soon as
                  practicable.

         16.2     NOTICES. Any notice required to be given or made under this
                  Agreement by one of the parties hereto to the other shall be
                  in writing, by personal delivery, registered U.S. mail or
                  overnight courier, addressed to such other party at its
                  address indicated below, or to such other address as the
                  addressee shall have last furnished in writing to the
                  addressor and shall be effective upon the date of receipt.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     29
<PAGE>

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

                  If to Myogen:         Myogen, Inc.
                                        7575 W. 103rd Avenue, #102
                                        Westminster, CO 80021-5426
                                        Attn:  President

                  With a copy to:       Cooley Godward LLP
                                        380 Interlocken Crescent
                                        Suite 900
                                        Broomfield, CO  80021-8023
                                        Attn:  Steven N. Dupont, Esq.

                  If to Abbott:         Abbott International Ltd.
                                        100 Abbott Park Road
                                        Dept. 6WP; Bldg. AP34
                                        Abbott Park, IL  60064-3537
                                        Attn:  Senior Vice President,
                                        International Operations

                  With a copy to:       Abbott Laboratories
                                        100 Abbott Park Road
                                        Dept. 364; Bldg. AP6D
                                        Abbott Park, IL 60064-6032
                                        Attn:  Senior Vice President, Secretary
                                        and General Counsel

         16.3     APPLICABLE LAW/COMPLIANCE. This Agreement shall be governed by
                  and construed in accordance with the laws of the State of
                  Illinois, excluding its conflict of laws provision. Each party
                  hereto shall comply with all applicable laws, rules,
                  ordinances, guidelines, consent decrees and regulations of any
                  federal, state or other governmental authority.

         16.4     ENTIRE AGREEMENT. This Agreement and the attachments
                  (Exhibits) contain the entire understanding of the parties
                  with respect to the subject matter hereof. All express or
                  implied agreements and understandings, either oral or written,
                  heretofore made are expressly merged in and made a part of
                  this Agreement. This Agreement may be amended, or any term
                  hereof modified, only by a written instrument duly executed by
                  both parties hereto.

         16.5     COUNTERPARTS . This Agreement may be executed in two or more
                  counterparts, each of which shall be deemed an original, but
                  all of which together shall constitute one and the same
                  instrument.

         16.6     SEVERABILITY/HEADINGS. If any provision of this Agreement is
                  deemed unenforceable, the remainder of the Agreement will not
                  be affected and, if

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     30
<PAGE>

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

                  appropriate, the parties will attempt to replace the
                  unenforceable provision with a new provision that, to the
                  extent possible, reflects the parties' original intent. The
                  captions and headings used in this Agreement are for reference
                  only and are not to be construed in any way as terms or used
                  to interpret the provisions of this Agreement.

         16.7     ASSIGNMENT. Neither party may without written approval of the
                  other assign this Agreement or transfer its interest or any
                  part thereof under this Agreement to any Third Party except
                  that (a) either party may assign this Agreement without
                  consent to a Third Party that acquires all or substantially
                  all of the business to which this Agreement pertains, or, (b)
                  either party may assign this Agreement in whole or part to any
                  Affiliate of that party and such party hereby guarantees the
                  performance by such Affiliate.

         16.8     DISPUTE RESOLUTION. The parties hereto shall attempt to settle
                  any dispute arising out of or relating to this Agreement in an
                  amicable way. Except for claims for injunctive or other
                  equitable relief, which may be brought in any court of
                  competent jurisdiction, any controversy, claim or right of
                  termination for cause which may arise under, out of, in
                  connection with, or relating to this Agreement, or any breach
                  thereof, shall be settled according to the Alternative Dispute
                  Resolution provisions attached hereto as Exhibit D.

         16.9     INDEPENDENT CONTRACTOR. It is understood that both parties
                  hereto are independent contractors and engage in the operation
                  of their own respective businesses and neither party hereto is
                  to be considered the agent of the other party for any purpose
                  whatsoever and neither party has any authority to enter into
                  any contract or assume any obligation for the other party or
                  to make any warranty or representation on behalf of the other
                  party. Each party shall be fully responsible for its own
                  employees, servants and agents, and the employees, servants
                  and agents of one party shall not be deemed to be employees,
                  servants and agents of the other party for any purpose
                  whatsoever.

         16.10    SURVIVAL. Sections 8.1, 8.2, 8.3, 8.4 and 8.6, Articles 9, of
                  this Agreement shall survive the expiration or termination of
                  this Agreement for any reason for a period of seven (7) years,
                  Articles 15, 16.8 and 16.10 of this Agreement shall survive
                  the expiration or termination of this Agreement for any reason
                  and Article 7 shall survive early termination of this
                  Agreement for any reason with respect to Product sold prior to
                  such termination and with respect to Product sold after such
                  termination if such termination was by Myogen pursuant to
                  Section 10.2, by Abbott for Myogen's breach pursuant to
                  Section 10.3, or by Abbott by reason of Myogen's insolvency
                  under Section 10.4. Nothing contained in the preceding
                  sentence shall be deemed to entitle Abbott to double recovery
                  of damages under any patent infringement suit against Myogen.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     31
<PAGE>

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

         16.11    PUBLICITY. No press release or other public announcement shall
                  be made by either party concerning the execution of this
                  Agreement or the fact that Myogen has licensed the Compound
                  from Abbott, without the prior written consent of the
                  non-disclosing party, which consent shall not be unreasonably
                  withheld. Neither party shall use the name of the other party,
                  its officers, employees or agents for purposes of any public
                  commercial activity without the other party's prior written
                  consent, except where the name of the other party must be
                  disclosed as a matter of law. Should either party wish to make
                  a disclosure or be required by law to make a disclosure, the
                  disclosing party shall submit a copy of the proposed
                  disclosure to the other party for review. The non-disclosing
                  party shall have two (2) weeks to review and comment on the
                  content of such disclosure. In the case of a disclosure
                  required by law, the disclosing party, subject to legal
                  requirements, shall use all reasonable efforts to accommodate
                  the non-disclosing party's comments. For non-routine matters
                  like an emergency, special circumstance, or other situation
                  where the law compels a disclosure in less than three (3)
                  week's time, the non-disclosing party agrees to use
                  commercially reasonable efforts to provide its review and
                  comment in order to meet the disclosing party's timetable.

                  (REMAINDER OF PAGE INTENTIONALLY LEFT BLANK)

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     32
<PAGE>

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

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the Effective Date.

ABBOTT LABORATORIES                        MYOGEN, INC.

By: /s/ Jeffrey M. Leiden                  By:  /s/ J. William Freytag
    -----------------------------------         --------------------------------

Name: Jeffrey M. Leiden                    Name: J. William Freytag
      ---------------------------------          -------------------------------

Its: President & COO                       Its:  President & CEO
     ----------------------------------          -------------------------------

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     1
<PAGE>
                      [/\#/\] CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS
                                 DOCUMENT, MARKED BY BRACKETS, IS FILED WITH THE
                                  SECURITIES AND EXCHANGE COMMISSION PURSUANT TO
                             RULE 406 OF THE SECURITIES ACT OF 1933, AS AMENDED.

                                    EXHIBIT A

                                       TO
                           EXCLUSIVE LICENSE AGREEMENT
                                     BETWEEN
                               ABBOTT LABORATORIES
                                       AND
                                  MYOGEN, INC.
                               DATED JUNE 30, 2003

                        PATENTS AND PATENT APPLICATIONS

<Table>
<Caption>
     NO.           PRIORITY DATE       WO NUMBER                IN-HOUSE NO.                      TITLE
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
<S>             <C>                  <C>                       <C>                <C>
      1              23.04.93         WO 94/25442                  43997             3-Het-Arylcarbonsaure-derivate
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
                                                                                   Verwendung von Carbonsaurederivaten als
      2              31.03.94         WO 95/26716                  44751                       Arzneimittel
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
      3              14.10.94         WO 96/11914                  45281                 Neue Carbonsaurederivate
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
      4              26.09.97         WO 99/16445                 480/1171        Combination of ETRAs plus RAS-inhibitors
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
      5              19.12.96           Germany                   480/1174        Combination of ETRAs plus vasodilators
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
                                                                                        Combination of ETRAs plus
      6              30.09.97         WO 99/16444                 480/1175                    beta-blockers
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
      7              05.12.97         WO 99/29308                 480/1181           Use of ETRAs to inhibit obesity
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
      8              30.10.98        WO 2000/026170                49493              Verfahren zur Racematspaltung
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
      9              20.01.00                                      51096           Enantioselective Synthesevon ETRAs
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
                                                                                  Combination of ETRAs plus aVb3 zur Behandlung
     10              19.09.00                                      51748                     von Restenosis
--------------  -------------------  ------------------------  -----------------  -----------------------------------------------
</Table>

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     1

<PAGE>

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

                                    EXHIBIT B

                                       TO
                           EXCLUSIVE LICENSE AGREEMENT
                                     BETWEEN
                               ABBOTT LABORATORIES
                                       AND
                                  MYOGEN, INC.
                               DATED JUNE 30, 2003

                                    WORK PLAN
                                  (PRELIMINARY)

[/\#/\]

                        PRELIMINARY DEVELOPMENT TIMELINES

[DRAWING]

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     1

<PAGE>

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

                                    EXHIBIT C

                                       TO
                           EXCLUSIVE LICENSE AGREEMENT
                                     BETWEEN
                               ABBOTT LABORATORIES
                                       AND
                                  MYOGEN, INC.
                               DATED JUNE 30, 2003

                              PRE-CLINICAL STUDIES

[/\#/\]

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     1

<PAGE>

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

                                    EXHIBIT D

                                       TO
                           EXCLUSIVE LICENSE AGREEMENT
                                     BETWEEN
                               ABBOTT LABORATORIES
                                       AND
                                  MYOGEN, INC.
                               DATED JUNE 30, 2003

                         ALTERNATIVE DISPUTE RESOLUTION

         The parties recognize that from time to time a dispute may arise
relating to either party's right or obligations under this Agreement. The
parties agree that any such dispute shall be resolved by the Alternative Dispute
Resolution ("ADR") provisions set forth in this Exhibit, the result of which
shall be binding upon the parties.

         To begin the ADR process, a party first must send written notice of the
dispute to the other party for attempted resolution by good faith negotiations
between their respective presidents (or their designees) of the affected
subsidiaries, divisions, or business units within twenty-eight (28) days after
such notice is received (all references to "days" in this ADR provision are to
calendar days). If the matter has not been resolved within twenty-eight (28)
days of the notice of dispute, or if the parties fail to meet within such
twenty-eight (28) days, either party may initiate an ADR proceeding as provided
herein. The parties shall have the right to be represented by counsel in such a
proceeding.

1.       To begin an ADR proceeding, a party shall provide written notice to the
         other party of the issues to be resolved by ADR. Within fourteen (14)
         days after its receipt of such notice, the other party may, by written
         notice to the party initiating the ADR, add additional issues to be
         resolved within the same ADR.

2.       Within twenty-one (21) days following receipt of the original ADR
         notice, the parties shall select a mutually acceptable neutral to
         preside in the resolution of any disputes in this ADR proceeding. If
         the parties are unable to agree on a mutually acceptable neutral within
         such period, either party may request the President of the CPR
         Institute for Dispute Resolution ("CPR"), 366 Madison Avenue, 14th
         Floor, New York, New York 10017, to select a neutral pursuant to the
         following procedures:

         (a)      The CPR shall submit to the parties a list of not less than
                  five (5) candidates within fourteen (14) days after receipt of
                  the request, along with a Curriculum Vitae for each candidate.
                  No candidate shall be an employee, director, or shareholder of
                  either party or any of their subsidiaries or affiliates.

         (b)      Such list shall include a statement of disclosure by each
                  candidate of any circumstances likely to affect his or her
                  impartiality.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED    1

<PAGE>

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

         (c)      Each party shall number the candidates in order of preference
                  (with the number one (1) signifying the greatest preference)
                  and shall deliver the list to the CPR within seven (7) days
                  following receipt of the list of candidates. If a party
                  believes a conflict of interest exists regarding any of the
                  candidates, that party shall provide a written explanation of
                  the conflict to the CPR along with its list showing its order
                  of preference for the candidates. Any party failing to return
                  a list of preferences on time shall be deemed to have no order
                  of preference.

         (d)      If the parties collectively have identified fewer than three
                  (3) candidates deemed to have conflicts, the CPR immediately
                  shall designate as the neutral the candidate for whom the
                  parties collectively have indicated the greatest preference.
                  If a tie should result between two candidates, the CPR may
                  designate either candidate. If the parties collectively have
                  identified three (3) or more candidates deemed to have
                  conflicts, the CPR shall review the explanations regarding
                  conflicts and, in its sole discretion, may either (i)
                  immediately designate as the neutral the candidate for whom
                  the parties collectively have indicated the greatest
                  preference, or (ii) issue a new list of not less than five (5)
                  candidates, in which case the procedures set forth in
                  subparagraphs 2(a) -2(d) shall be repeated.

3.       The ADR proceeding will be governed by and subject to the principles
         specified in the "CPR Rules for Non-Administered Arbitration" except to
         the extent such rules conflict with any of the provisions of this
         Agreement. No earlier than twenty-eight (28) days or later than six (6)
         months after selection, the neutral shall hold a hearing to resolve
         each of the issues identified by the parties, provided that the parties
         agree that stated goal of the parties is to hold such hearing within
         fifty-six (56) days after selection. The ADR proceeding shall take
         place at a location agreed upon by the parties. If the parties cannot
         agree, the neutral shall designate a location other than the principal
         place of business of either party or any of their subsidiaries or
         affiliates.

4.       At least seven (7) days prior to the hearing, each party shall submit
         the following to the other party and the neutral:

         (a)      a copy of all exhibits on which such party intends to rely in
                  any oral or written presentations to the neutral;

         (b)      a list of any witnesses such party intends to call at the
                  hearing, and a short summary of the anticipated testimony of
                  each witness;

         (c)      a proposed ruling on each issue to be resolved, together with
                  a request for a specific damage aware or other remedy for each
                  issue. The proposed rulings and remedies shall not contain any
                  recitation of the facts or any legal arguments and shall not
                  exceed one (1) page per issue.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     2

<PAGE>

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

         (d)      a brief in support of such party's proposed rulings and
                  remedies, provided that the brief shall not exceed twenty (20)
                  pages. This page limitation shall apply regardless of the
                  number of issues raised in the ADR proceeding.

         Except as expressly set forth in subparagraphs 4(a) - 4(d), no
         discovery shall be required or permitted by any means, including
         depositions, interrogatories, requests for admissions, or production of
         documents.

5.       The hearing shall be conducted on two (2) consecutive days and shall be
         governed by the following rules:

         (a)      Each party shall be entitled to five (5) hours of hearing time
                  to present its case. The neutral shall determine whether each
                  party has had the five (5) hours to which it is entitled.

         (b)      Each party shall be entitled, but not required, to make an
                  opening statement, to present regular and rebuttal testimony,
                  documents or other evidence, to cross-examine witnesses, and
                  to make a closing argument. Cross-examination of witnesses
                  shall occur immediately after their direct testimony, and
                  cross-examination time shall be charged against the party
                  conducting the cross-examination.

         (c)      The party initiating the ADR shall begin the hearing and, if
                  it chooses to make an opening statement, shall address not
                  only issues it raised but also any issues raised by the
                  responding party. The responding party, if it chooses to make
                  an opening statement, also shall address all issues raised in
                  the ADR. Thereafter, the presentation of regular and rebuttal
                  testimony and documents, other evidence, and closing arguments
                  shall proceed in the same sequence.

         (d)      Except when testifying, witnesses shall be excluded from the
                  hearing until closing arguments.

         (e)      Settlement negotiations, including any statements made
                  therein, shall not be admissible under any circumstances.
                  Affidavits prepared for purposes of the ADR hearing also shall
                  not be admissible. As to all other matters, the neutral shall
                  have sole discretion regarding the admissibility of any
                  evidence.

6.       Within seven (7) days following completion of the hearing, each party
         may submit to the other party and the neutral a post-hearing brief in
         support of its proposed rulings and remedies, provided that such brief
         shall not contain or discuss any new evidence and shall not exceed ten
         (10) pages. This page limitation shall apply regardless of the number
         of issues raised in the ADR proceeding.

7.       The neutral shall rule on each disputed issue within fourteen (14) days
         following completion of the hearing. Such ruling shall adopt in its
         entirety the proposed ruling and remedy of one of the parties on each
         disputed issue but may adopt one party's proposed rulings and remedies
         on some issues and the other party's proposed rulings and remedies on
         other issues. The neutral shall not issue any written opinion or
         otherwise explain the basis of the ruling.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     3
<PAGE>

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

8.       The neutral shall be paid a reasonable fee plus expenses. These fees
         and expenses, along with the reasonable legal fees and expenses of the
         prevailing party (including all expert witness fees and expenses), the
         fees and expenses of a court reporter, and any expenses for a hearing
         room, shall be paid as follows:

         (a)      If the neutral rules in favor of one party on all disputed
                  issues in the ADR, the losing party shall pay 100% of such
                  fees and expenses.

         (b)      If the neutral rules in favor of one, party on some issues and
                  the other party on other issues, the neutral shall issue with
                  the rulings a written determination as to how such fees and
                  expenses shall be allocated between the parties. The neutral
                  shall allocate fees and expenses in a way that bears a
                  reasonable relationship to the outcome of the ADR, with the
                  party prevailing on more issues, or on issues of greater value
                  or gravity, recovering a relatively larger share of its legal
                  fees and expenses.

9.       The rulings of the neutral and the allocation of fees and expenses
         shall be binding, non-reviewable, and non-appealable, and may be
         entered as a final judgment in any court having jurisdiction.

10.      Except as provided in paragraph 9 or as required by law, the existence
         of the dispute, any settlement negotiations, the ADR hearing, any
         submissions (including exhibits, testimony, proposed rulings, and
         briefs), and the rulings shall be deemed Confidential Information. The
         neutral shall have the authority to impose sanctions for unauthorized
         disclosure of Confidential Information.

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED     4

<PAGE>

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

1  ABBOTT
--------------------------------------------------------------------------------

Global Licensing & New Business Development
Abbott Laboratories
200 Abbott Park Road, Dept R50A/AP34-2
Abbott Park, Illinois 60064

                                                                   June 27, 2003

Myogen, Inc.
7575 W. 103rd Avenue
Westminster, CO 80021-5426

      Re:   License Agreement Dated June 27, 2003 ("License Agreement") Between
            Abbott Laboratories ("Abbott") and Myogen, Inc. ("Myogen")

Dear Sir or Madam:

In the event of a transfer of manufacturing responsibility to a Third Party
Manufacturer for the supply of Compound and/or Product in accordance with
Section 6.6(b) of the License Agreement, Myogen may request the assistance of
Abbott personnel with knowledge and skills in the manufacture of Compound and/or
Product to assist Myogen with such transfer.

Myogen may request such assistance by providing written notice to Abbott
specifying the nature of the assistance requested and suggesting the schedule
for Abbott to provide such assistance. Abbott shall reasonably cooperate with
Myogen's request and assign qualified Abbott personnel to provide such
assistance at a schedule subject to the mutual agreement of the parties.

Myogen shall compensate Abbott for each hour of personnel time spent providing
the assistance at the rate of [/\#/\]. Myogen shall also reimburse Abbott for
all reasonable costs and expenses incurred by such Abbott personnel in
connection with providing the assistance, including reasonable travel and
lodging expenses. The parties agree that Abbott shall not be obligated to supply
more than [/\#/\] of personnel time in response to Myogen's
request.

The parties indicate their agreement to the foregoing understanding by their
signatures below.

ABBOTT LABORATORIES                        MYOGEN, INC.

By: /s/ Signature Illegible                By: /s/J. William Freytag
    ----------------------------------         ---------------------------------
Title: Divisional Vice President           Title: President & CEO
       -------------------------------            ------------------------------
Date: 6-27-03                              Date: 6-27-03
      --------------------------------           -------------------------------

[/\#/\] CONFIDENTIAL TREATMENT REQUESTED    1<PAGE>
                                                                   EXHIBIT 10.24

                              [/\#/\] 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.

                       COLLABORATION AND OPTION AGREEMENT

                                 by and between

                                  MYOGEN, INC.

                                       and

                NOVARTIS INSTITUTES FOR BIOMEDICAL RESEARCH, INC.

<PAGE>

                              [/\#/\] 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.

                       COLLABORATION AND OPTION AGREEMENT

         This Agreement is made this 8th day of October, 2003 (the "Effective
Date") by and between Myogen, Inc. ("Myogen"), a Delaware corporation with
principal offices at 7575 W. 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.

                                  INTRODUCTION

         WHEREAS, Myogen is a biotechnology company with expertise and
experience in identifying Targets relating to, and discovering, developing and
commercializing compounds aimed at treating, cardiovascular disease;

         WHEREAS, NIBRI and its Affiliates are interested in developing and
commercializing drugs targeting the Myogen Targets using their expertise in
developing, manufacturing, marketing and selling pharmaceuticals worldwide;

         WHEREAS, both parties desire to enter into a collaboration the
objective of which will be to identify and validate compounds which act on the
Myogen Targets, and thereafter for NIBRI and its Affiliates to have the option
to develop, market and sell certain of those compounds as drugs upon the terms
set forth herein and in a License, Development and Commercialization Agreement
identical in substance to EXHIBIT A hereto;

         NOW THEREFORE, in consideration of the mutual covenants set forth in
this Agreement, and other good and valuable consideration, the parties agree as
follows:

                                    ARTICLE I

                                   DEFINITIONS

                                         [/\#/\]CONFIDENTIAL TREATMENT REQUESTED

                Collaboration and Option Agreement - Confidential

<PAGE>

         1.1. "ACTIVE COMPOUND" shall mean any chemical compound that has a
specific, desired therapeutic action on, interaction on, or modulation of a
Myogen Target or a Collaboration Target, and any and all compounds having the
same Active Moiety as such Active Compound, whether a small molecule, protein or
antibody.

         1.2. "ACTIVE MOIETY" shall have the meaning assigned to that term under
21 CFR 314.108(a), as such regulation is in effect on the Effective Date;
namely: "the molecule or ion excluding those appended portions of the molecule
that cause the drug to be an ester, salt (including a salt with hydrogen or
coordination bonds), or other noncovalent derivative (such as a complex, a
chelate or clathrate) of the molecule, responsible for the physiological or
pharmacological action of the drug substance."

         1.3. "AFFILIATE" shall mean, with respect to any Person, any other
Person that, directly or indirectly, by itself or through one or more
intermediaries, controls, or is controlled by, or is under common control with,
such Person. The term "control" means the possession, direct or indirect, of the
power to direct or cause the direction of the management and policies of a
Person, whether through the ownership of voting securities, by contract or
otherwise. Control will be presumed if one Person owns, either of record or
beneficially, at least 50% of the voting stock of any other Person. Such other
relationship as in fact results in actual control over the management, business,
and affairs of a Person shall also be deemed to constitute control; provided,
however, that no Person shall be deemed to exercise control over another Person
solely because the latter relies on the former for a majority of its business. A
Person will be deemed an Affiliate only so long as such ownership or control
relationship continues. In the case of NIBRI, "Affiliates" shall also expressly
be deemed to include the Novartis Institute for Functional Genomics, Inc., and
the Friedrich Miescher Institute for BioMedical Research and their respective
Affiliates.

         1.4. "COLLABORATION COMPOUND" shall mean any new chemical compound
synthesized for the first time or identified for the first time as an Active
Compound in the course of the Research Program, but shall explicitly exclude the
NIBRI Compounds.

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         1.5. "COLLABORATION TARGET" shall mean any Target identified for the
first time in the course of the Research Program or a Development Program.

         1.6. "COLLABORATION TECHNOLOGY" shall mean any Technology that relates
to Collaboration Targets and/or Collaboration Compounds.

         1.7. "COMPOUND" shall mean any Myogen Compound, NIBRI Compound, or
Collaboration Compound and other compounds having the same Active Moiety as a
Myogen Compound, NIBRI Compound, or Collaboration Compound.

         1.8. "CONTROLLED" shall mean, with respect to a Compound, Target, or
Technology, the legal authority or right of a party hereto to grant a license or
sublicense of intellectual property rights to another party hereto, or to
otherwise disclose proprietary or trade secret information to such other party,
without breaching the terms of any agreement with a Third Party, infringing upon
the intellectual property rights of a Third Party, or misappropriating the
proprietary or trade secret information of a Third Party.

         1.9. "CRITICAL ISSUES" shall have the meaning set forth in Section
2.7.2 hereof.

         1.10. "DEVELOPMENT CANDIDATE" shall mean a NIBRI Compound, Myogen
Compound or Collaboration Compound, together with the Myogen Target or
Collaboration Target on which it has therapeutic action, as to which NIBRI
exercises its Option pursuant to Section 4.4 of this Agreement to license for
development in the Field.

         1.11. "DEVELOPMENT PROGRAM" shall mean activities associated with
development of a Development Candidate as specified in the License Agreement.

         1.12. "EFFECTIVE DATE" shall mean the effective date of this Agreement
as set forth on the first page hereof.

         1.13. "FIELD" shall mean the research, treatment, prognosis, diagnosis,
prophylaxis, and monitoring of heart muscle disease.

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         1.14. "FTE" shall mean the equivalent of the work of one Myogen
scientist or other project managerial professional, full time for one year,
which equates to a total of [/\#/\] hours per year of work, on or directly
related to the Research Program, including attendance at relevant scientific
seminars and symposia. FTEs shall include equivalent scientific work in the
Research Program delegated to and carried out by contractors (including Myogen's
academic collaborators) under the general direction of Myogen scientists. The
annual rate per FTE shall be [/\#/\].

         1.15. "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 (as defined in the License Agreement) are
intended to be sold.

         1.16. "GLP" shall mean the current Good Laboratory Practices
regulations promulgated by the Food and Drug Administration, 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.

         1.17. "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.

         1.18. "IN VIVO VALIDATION" means, with respect to a Myogen Compound,
Collaboration Compound or NIBRI Compound, the achievement of physiologically
significant activity in an appropriate in vivo model or models, where the level
of physiological 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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         1.19. "JOINT STEERING COMMITTEE" or "JSC" shall have the meaning set
forth in Section 2.4 hereof.

         1.20. "KNOW-HOW" means all Technology other than inventions that are
the subject of Patents.

         1.21. "LICENSE AGREEMENT" shall mean the License, Development and
Commercialization Agreement, identical in substance to EXHIBIT A hereto, to be
executed by Myogen and NIBRI with respect to each Development Candidate.

         1.22. "MYOGEN COMPOUND" shall mean any Active Compound that is
Controlled by Myogen and is identified and/or synthesized by Myogen, its
Affiliates, and/or its external academic collaborators in the Field, except for
any Active Compound that has therapeutic action against both a Myogen Target and
Targets within Myogen's HDAC inhibitor program.

         1.23. "MYOGEN KNOW-HOW" shall mean all Know-How of Myogen or its
Affiliates relating to a Myogen Compound, a Collaboration Compound, a
Collaboration Target, or a Myogen Target or relating to or used in connection
with the Research Program.

         1.24. "MYOGEN PATENTS" shall mean any Patents Controlled by Myogen or
any of its Affiliates relating to the Myogen Targets, Myogen Compounds,
Collaboration Targets, Collaboration Compounds, and methods or reagents used in
identifying, using, developing or manufacturing such Myogen Targets, Myogen
Compounds, Collaboration Targets, and Collaboration Compounds, as applicable. A
list of Myogen Patents is appended hereto as Schedule 1.24 and will be updated
periodically to reflect additions thereto during the course of this Agreement.

         1.25. "MYOGEN TARGET" shall mean any Target Controlled by Myogen and
identified and/or synthesized by Myogen, its Affiliates, and/or its external
academic collaborators in the Field, excluding any Targets within Myogen's HDAC
inhibitor program. A list of Myogen Targets as of the Effective Date is set
forth on Schedule 1.25 appended hereto. Such Schedule

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1.25 may be updated periodically to reflect additions thereto during the course
of this Agreement.

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

         1.27. "NIBRI COMPETITOR" means a Person with annual pharmaceutical
sales of [/\#/\] or more.

         1.28. "NIBRI COMPOUND" shall mean any Active Compound synthesized,
identified, or Controlled by NIBRI and/or its Affiliates.

         1.29. "NIBRI KNOW-HOW" shall mean all Know-How of NIBRI or its
Affiliates relating to a NIBRI Compound, a Collaboration Compound, a
Collaboration Target, or a Myogen Target.

         1.30. "NIBRI PATENTS" shall mean any Patents Controlled by NIBRI or any
of its Affiliates relating to NIBRI Compounds, Collaboration Compounds, Myogen
Targets, Collaboration Targets, and methods or reagents used in identifying,
developing, or manufacturing such NIBRI Compounds, Collaboration Targets, and
Collaboration Compounds, as applicable, as in effect on the Effective Date and
at any time during the term of this Agreement.

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

         1.32. "PATENTS" means 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.

         1.33. "PERSON" means any individual, corporation, partnership,
association, joint-stock company, trust, unincorporated organization or
government or political subdivision thereof.

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         1.34. "RESEARCH PLAN" shall have the meaning set forth in Section 2.3.1
hereof.

         1.35. "RESEARCH PROGRAM" shall mean research activities and development
activities undertaken under this Agreement, associated with the identification,
design and development of Targets, Compounds and Development Candidates as
provided herein, including but not limited to: identification and initial
testing of Targets and Compounds; selection of Development Candidates from
Targets and Compounds and preparation for preclinical assessment of those
Development Candidates; formulation and manufacture of Development Candidates
for use in preclinical and clinical studies performed in accordance with GCP;
preclinical animal studies performed in accordance with GLP (or the applicable
equivalent); planning, implementation, administration and evaluation of human
clinical trials performed in accordance with GCP and included in Proof of
Concept studies; and manufacturing process development and scale-up as
appropriate at the stage of development encompassed within the Proof of Concept
studies.

         1.36. "RESEARCH PROGRAM COSTS" shall mean extraordinary external
expenses and capital costs that are approved in advance by the JSC and incurred
by or on behalf of a party in connection with the conduct of the Research
Program.

         1.37. "RESEARCH YEAR" means a twelve (12) month period during the term
of a Research Program commencing on October 1 of a given year, and ending on
September 30 of the following year. The first Research Year hereunder shall be
deemed to have commenced on October 1, 2003.

         1.38. "TARGET" shall mean any biological entity identified as being
potentially involved in one or more disease states.

         1.39. "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 in connection with
the conduct of a Development Program under the License Agreement, that relate to
the research,

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development, utilization, manufacture or use of Compounds, Targets, or
Development Candidates, as applicable.

         1.40. "TERRITORY" shall mean worldwide.

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

         1.42. "WIND-DOWN PERIOD" shall have the meaning set forth in Section
9.4 hereof.

         1.43. "WORK PLAN" shall have the meaning set forth in Section 2.3.2
hereof.

         Capitalized terms used but not otherwise defined herein that are
defined in the License Agreement shall have the meaning ascribed to them
therein.

                                   ARTICLE II

                                RESEARCH PROGRAM

         2.1. COMMENCEMENT.

                  The Research Program shall commence as soon as practicable
after the Effective Date. The Joint Steering Committee shall direct the conduct
of the Research Program and Myogen and NIBRI shall collaborate in the conduct of
the Research Program, with the parties having the roles and responsibilities
specified in the Research Plan and/or applicable Work Plans, all as may be
deemed appropriate by the Joint Steering Committee. The Joint Steering Committee
shall review and coordinate the efforts of the parties with respect to the
Research Program.

         2.2. TERM.

                  The Research Program will conclude three (3) years from the
Effective Date, unless earlier terminated in accordance with the provisions
hereof. Unless earlier terminated in accordance with the provisions hereof, the
Research Program may be extended for an additional

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term of either one (1) year or two (2) years, in the sole discretion of NIBRI,
upon the provision of written notice to Myogen not later than ninety (90) days
prior to the end of the initial three (3) year Research Program term and,
thereafter, for additional one (1) year periods upon the mutual written
agreement of Myogen and NIBRI prior to the end of the then current Research
Year.

         2.3. RESEARCH PLAN; WORK PLANS.

                  2.3.1. Research Plan, Generally. NIBRI, in consultation with
Myogen, will prepare an overall research plan (the "Research Plan") for the
Research Program. An initial outline of the Research Plan shall be attached to
this Agreement as Schedule 2.3.1. A final version of the Research Plan will then
be submitted to the Joint Steering Committee for approval at the first meeting
of the Joint Steering Committee. The Research Plan will be revised, updated and
submitted to the Joint Steering Committee at least semi-annually for its review
and comment.

                  2.3.2. Work Plans. Within thirty (30) days of the Effective
Date, the parties will agree upon an initial work plan (a "Work Plan")
identifying: (a) priorities with respect to programs, Targets, and compounds
("Projects") to be pursued; (b) the responsibilities of each party with respect
to the same; (c) the appropriate resources of each party to be committed to the
Projects; and (d) developmental milestones, performance criteria, and timeframes
with respect to such Projects. The Work Plan shall be submitted for approval at
the first meeting of the JSC. It is anticipated that the number of Projects
selected for the Work Plan will be no less than three (3) at any time during the
collaboration, unless otherwise agreed to by the parties.

                  2.3.3. Plan Review. The Research Plan and all Work Plans will
be reviewed as necessary at each meeting of the Joint Steering Committee, and at
any other time upon the request of either party, and shall be modified as
appropriate to reflect material scientific or commercial developments. Any
disagreements between the parties with respect to modification of the Research
Plan or a Work Plan will be resolved in accordance with Section 2.7 of this
Agreement.

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                  2.3.4. Research Diligence. Each of Myogen and NIBRI shall work
diligently and shall use commercially reasonable efforts to fulfill its
respective obligations under the Research Plan and any Work Plan.

                  2.3.5. Submission of Reports. Upon achieving the developmental
milestones specified in a Work Plan with respect to a particular Project, Myogen
and NIBRI will complete and present to the JSC a report containing detailed
summaries of the data for the Project specified in the Work Plan.

         2.4. JOINT STEERING COMMITTEE.

                  Upon execution of this Agreement, Myogen and NIBRI will
establish a Joint Steering Committee ("JSC"), which shall consist of an equal
number of executives or scientists as may be designated by each party from time
to time. The JSC shall initially have six (6) members. If the JSC chooses to
designate a Committee Chair, the Chair will be appointed from among the members
of the JSC designated by NIBRI. The JSC shall hold its first meeting within
thirty (30) days of the Effective Date. Thereafter, the JSC shall meet
quarterly, or with such other frequency as may be established by the JSC (but in
no event less often than three (3) times per year), and at such time and
location as may be established by the JSC, for the following purposes:

                  (a)   Provide general oversight of the entire collaboration
                        between Myogen and NIBRI, including the Research Program
                        and any development and commercialization of a
                        Development Candidate under the License Agreement;

                  (b)   Periodically review the overall goals and strategy of
                        the Research Program;

                  (c)   Prioritize the allocation of resources dedicated to the
                        Research Program;

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                  (d)   Resolve any disagreement between the parties with regard
                        to a particular Development Candidate, and discuss and
                        resolve any other relevant issues submitted to it, in
                        accordance with the dispute resolution procedure set
                        forth in Section 2.7 below; and

                  (e)   Address any matters raised under relevant provisions of
                        the License Agreement.

                  The JSC shall have the authority to create project teams for
the Research Program, each of which will meet (via telephone or video conference
or in person) no less frequently than monthly, and which will report to the JSC
on its progress on activities performed on the Research Program. The JSC shall
also have the authority to create additional subcommittees as needed.
Notwithstanding the foregoing, the JSC shall not have the authority to amend or
modify the terms of this Agreement.

         2.5. EXCHANGE OF INFORMATION.

                  2.5.1. Myogen and NIBRI will share information with the JSC,
as soon as it is available, necessary to facilitate mutual understanding of the
status of the Research Program and decision-making in connection therewith.

                  2.5.2. Neither Myogen nor NIBRI shall use Technology disclosed
by the other party (excluding information which is no longer subject to
confidentiality restrictions under Article V by reason of the exceptions set
forth in Section 5.2(a), (b) and (c)) for any purpose, including the filing of
Patent applications containing such information without the other party's
consent (which shall not be unreasonably withheld), other than for carrying out
the Research Program or discharging its responsibilities under the License
Agreement, or as otherwise permitted under the License Agreement.

                  2.5.3. Upon conclusion of the Research Program and subject to
the provisions of Section 2.5.4 and Article V hereof, each party shall disclose
to the other all technical information known to it which constitutes NIBRI
Technology or Myogen Technology, as the case may be.

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                  2.5.4.

                  (a)  Neither party shall be entitled to information from the
                       other party concerning know-how or technology discovered
                       or developed by that party outside the Research Program
                       or a Development Program under the License Agreement
                       (except as otherwise provided in the License Agreement)
                       or otherwise unrelated to research or development of
                       Targets, Compounds or Development Candidates under this
                       Agreement or the License Agreement; except that each
                       party must disclose to the JSC in a timely manner any and
                       all know-how and/or technology which it discovers or
                       develops regarding: (i) the Myogen Targets; (ii) the
                       Collaboration Targets; or (iii) any Collaboration
                       Technology.

                  (b)  Neither party will apply its rights in any Technology or
                       the use thereof (and will use best efforts to prevent its
                       licensees, if any, from applying similar rights acquired
                       by license) to block or impede the use of such Technology
                       as permitted hereunder by the other party or its
                       assignees or licensees.

         2.6. PRIMARY DATA ACCESS.

                  Myogen and NIBRI shall grant each other access to all data
(including, without limitation, all primary data and data contained in
laboratory notebooks) generated in the course of performing its obligations
under the Research Program. Each party shall have the right, at reasonable
intervals and at such party's own expense, to make copies of such data to use
and transfer as permitted hereunder.

         2.7 DECISIONS OF THE JSC; RESOLUTION OF DISPUTES.

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                  2.7.1. The JSC shall make decisions unanimously where
possible, but at least by majority vote. In the event of a deadlock, NIBRI shall
have the deciding vote on all matters other than those addressed in Section
2.7.2.

                  2.7.2. In the event that the JSC is deadlocked as to: (a) any
proposed significant reorientation of the entire Research Program; or (b) any
material change in financial or other resources required to be expended by
Myogen in connection with the Research Program; ("Critical Issues") then the
parties may have the issue resolved in accordance with the dispute resolution
mechanism set forth in Section 11.3 hereof.

                                  ARTICLE III

                                    PAYMENTS

         3.1. SIGNATURE PAYMENTS BY NIBRI.

                  Within thirty (30) days of the Effective Date, NIBRI will make
an initial payment of four million dollars ($4,000,000) to Myogen, of which: (a)
one million ($1,000,000) is in consideration of licenses hereunder; and (b)
three million ($3,000,000) is a reimbursement of Myogen's past investment in
research and development of the Myogen Technology.

         3.2. ADDITIONAL CASH PAYMENT.

                  NIBRI shall make an additional payment of one million dollars
($1,000,000) within thirty (30) days after the first anniversary of the
Effective Date as a reimbursement of Myogen's past involvement in research and
development of the Myogen Technology.

         3.3. STAFFING AND RESEARCH SUPPORT PAYMENTS.

                  NIBRI will pay to Myogen: (a) [/\#/\]. The JSC shall determine
the exact number of FTEs to be funded by NIBRI in any particular Research Year
and the manner in which such FTEs shall be allocated under the Research Program.
Between [/\#/\] FTEs shall be funded by NIBRI in any Research Year in connection
with the Research Program. Any FTEs greater than

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[/\#/\] require NIBRI's prior approval. The annual rate per FTE shall be
[/\#/\]. The FTEs shall be funded in support of the Research Program under this
Agreement.

                  Payments due for each Research Year shall be made by NIBRI to
Myogen [/\#/\]. All payments shall be made without deduction for withholding or
other similar taxes, in United States dollars to the credit of such bank account
as may be designated by Myogen in writing to NIBRI. Any payments which fall due
on a date which is a legal holiday in the Commonwealth of Massachusetts may be
made on the next following day which is not a legal holiday in the Commonwealth.

                  In the event that NIBRI terminates its participation in the
Research Program pursuant to Section 9.4, it shall nevertheless continue during
the Wind-Down Period to fund: [/\#/\]

         3.4. RECORDS.

                  Myogen shall keep accurate records and books of accounts
containing all data reasonably required for the calculation and verification of
FTEs employed by, or equivalents supplied by, Myogen in accordance with the
Research Plan.

                  At NIBRI's request, Myogen shall make those records available,
no more than once a year, during reasonable working hours, for review by a
recognized independent accounting firm acceptable to both parties, at NIBRI's
expense, for the sole purpose of verifying the accuracy of those records in the
calculation of Research Program FTEs. NIBRI shall use commercially reasonable
efforts to cause the accounting firm to retain all such information in
confidence.

                  In the event of a negative difference between the average
number of FTEs stated to be involved in the Research Program and the number of
FTEs actually employed, the amount previously advanced to Myogen and
attributable to any such negative difference shall be due and payable to NIBRI
without delay. If the negative difference is more than [/\#/\] in any Research

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Year, then Myogen shall also pay the reasonable costs of the independent
accountant employed by NIBRI in the review. Interest at the rate of [/\#/\] per
month, assessed from the end of the Research Year to which the negative
difference relates, shall be due from Myogen.

         3.5. MILESTONE PAYMENTS.

                  NIBRI shall make milestone payments in accordance with this
Section 3.5: (a) with respect to each Myogen Compound, Collaboration Compound or
NIBRI Compound having an effect on a High Priority Target, as defined below
(whether or not an Option, as defined below, has been exercised), within [/\#/\]
of the achievement of such milestone; and (b) with respect to each Myogen
Compound, Collaboration Compound or NIBRI Compound having an effect on a Low
Priority Target (as to which NIBRI has exercised its Option), payment within
[/\#/\] days of exercise of the Option for all prior milestones achieved. Except
as explicitly set forth below, milestone payments shall be payable only once
with respect to a particular Myogen Compound, Collaboration Compound or NIBRI
Compound, even though that Myogen Compound, Collaboration Compound or NIBRI
Compound may be subsequently developed for indications other than those for
which regulatory approval was initially sought. In the event that a Myogen
Compound, Collaboration Compound or NIBRI Compound fails in development, any
milestone payments previously paid with respect to such Myogen Compound,
Collaboration Compound or NIBRI Compound shall be fully creditable toward the
same milestone due with respect to another Myogen Compound, Collaboration
Compound or NIBRI Compound advanced as a lead Compound in place of the failed
Compound that acts on the same Myogen Target or Collaboration Target. NIBRI may
deduct from any milestone payments otherwise due to Myogen under this Section
3.5 the amount of any withholding and similar taxes required under applicable
law to be withheld from such payments and paid to applicable tax authorities.

                  The schedule below corresponds to an identical schedule in the
License Agreement; payments made pursuant to this Agreement prior to exercise of
an Option shall be treated as payments made under the License Agreement.

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<Table>
<Caption>

                                                               MILESTONE
DEVELOPMENTAL MILESTONE:                                       PAYMENT
------------------------                                       -------
<S>                                                            <C>
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*                                   [/\#/\]

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 [/\#/\]                          [/\#/\]
</Table>

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

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                                   ARTICLE IV

                LICENSE, DEVELOPMENT AND COMMERCIALIZATION RIGHTS

         4.1. EVALUATION LICENSE.

                  4.1.1. Myogen hereby grants to NIBRI and its Affiliates a
non-sublicensable (except to the extent required to engage any academic
collaborators or contractors used in connection with the Research Program by
either party) license in the Territory and in the Field, to use and have used
any and all Myogen Technology, Myogen Compounds, Myogen Targets, Collaboration
Targets, and Collaboration Compounds solely for the purpose of performing the
Research Program. The license granted by Myogen is exclusive solely to the
extent provided in Section 4.2.2.

                  4.1.2. NIBRI hereby grants to Myogen and its Affiliates a
non-exclusive license in the Territory, to use and have used any and all NIBRI
Technology, NIBRI Compounds, Collaboration Targets, and Collaboration Compounds
solely for the purpose of performing the Research Program with respect to the
High Priority Targets and to use and have used only Collaboration Technology for
conducting research and development activities within the Research Program on
any Low Priority Targets or Extra-Collaboration Targets.

         4.2. OPTION TO LICENSE.

                  4.2.1. NIBRI shall have the exclusive right (the "Option") to
license any and all Active Compounds, together with their underlying Myogen
Targets or Collaboration Targets, as Development Candidates, for development and
commercialization of products with respect to any and all human or veterinary
health care uses and any and all agricultural uses, under the terms and
conditions set forth in the License Agreement.

                  4.2.2. While the Option is in effect, Myogen will not grant to
any Third Party rights within the Field to Myogen Technology, Myogen Compounds,
Myogen Targets, Collaboration Targets, or Collaboration Compounds nor will
Myogen enter into any

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collaboration with a Third Party with respect to any of the foregoing. The
latter restriction shall not apply to Extra-Collaboration Targets, as defined
below, or the Active Compounds having a therapeutic effect on such
Extra-Collaboration Targets, if NIBRI's right of first negotiation has lapsed or
failed to result in a completed transaction between Myogen and NIBRI, despite
the good faith efforts of the parties.

         4.3. PRIORITIZATION OF COMPOUNDS.

                  For purposes of this Agreement and the Research Program, the
JSC shall classify all Myogen Targets and Collaboration Targets as follows:

                  4.3.1. High Priority Targets (which may be identified using
Myogen Compounds, NIBRI Compounds, or Collaboration Compounds) are those Myogen
Targets and Collaboration Targets the study of which, and the allocation of
resources to which, the JSC has established as a high priority of the Research
Program. In the case of Active Compounds related to such High Priority Targets:

                  (a)      NIBRI shall make payments with respect to all
                           research milestones in accordance with Section 3.5
                           above, [/\#/\]

                  (b)      [/\#/\] shall be payable; and

                  (c)      NIBRI may exercise its Option to license an Active
                           Compound relating to a High-Priority Target [/\#/\]
                           other than termination for NIBRI's breach under
                           Section 9.3.

                  4.3.2. Low Priority Targets (which may be identified using
Myogen Compounds and Collaboration Compounds) are those Myogen Targets and
Collaboration Targets the study of which, and the allocation of resources to
which, the JSC has determined are not an immediate priority but could prove to
be of importance in the Research Program. Myogen may continue to study such Low
Priority Targets using its own resources. In the case of Active Compounds
related to such Low Priority Targets:

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                  (a)      [/\#/\] shall be payable so long as a Low Priority
                           Target retains that status;

                  (b)      At any time during the Research Term, but in any case
                           no later than [/\#/\] after In Vivo Validation of an
                           Active Compound in connection with such Low Priority
                           Target, the JSC will elect either to elevate its
                           status to that of a High Priority Target or to lower
                           its status to an Extra-Collaboration Target, as
                           defined below;

                  (c)      NIBRI may elect at any time during the Research Term,
                           but no later than [/\#/\] after In Vivo Validation of
                           an Active Compound in connection with such Low
                           Priority Target, to exercise its Option with respect
                           to the same. In the event NIBRI exercises its Option,
                           payments associated with all previously achieved
                           milestones shall be due and payable within [/\#/\] of
                           execution of the respective License Agreement; and

                  (d)      If NIBRI does not exercise its Option with respect to
                           a Myogen Compound or a Collaboration Compound
                           relating to a Low Priority Target within the [/\#/\]
                           time period set forth in the immediately preceding
                           subsection, then the Low Priority Target shall become
                           an Extra-Collaboration Target.

                  4.3.3. Extra-Collaboration Targets (which may be identified
using Myogen Compounds) are those Myogen Targets the study of which the JSC
determines not to pursue in connection with the Research Program, or which
subsequently become Extra-Collaboration Targets pursuant to Section 4.3.2(d). In
the case of Extra-Collaboration Targets:

                  (a)      Myogen may continue to study such Extra-Collaboration
                           Targets using its own resources, subject to its
                           continued commitment to the resource levels specified
                           in the Work Plans for the High Priority Targets and
                           the periodic review of the JSC;

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                  (b)      [/\#/\] shall be payable by NIBRI with respect to
                           Active Compounds acting on such Extra-Collaboration
                           Targets; and

                  (c)      In the event that Myogen contemplates collaborating
                           with a Third Party with respect to development and/or
                           commercialization of an Active Compound acting on an
                           Extra-Collaboration Target, Myogen shall give NIBRI
                           written notice of the same. Within [/\#/\] of receipt
                           of such notice, NIBRI shall inform Myogen in writing
                           as to whether it wishes to negotiate in good faith a
                           collaboration between NIBRI and Myogen for the same
                           purposes. If NIBRI so informs Myogen, 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 Myogen may enter into a Third Party
                           transaction with respect to the Extra-Collaboration
                           Target. The right of first negotiation set out in
                           this Section 4.3.3(c) shall survive [/\#/\] beyond
                           any early termination of this Agreement under Section
                           9.4 or [/\#/\] after expiration of this Agreement;
                           provided, however, that if any Active Compound or
                           Extra-Collaboration Target is in development at the
                           time of the termination of this right of first
                           negotiation and has not attained In Vivo Validation,
                           NIBRI may extend the right for a period of up to
                           [/\#/\] or until [/\#/\] after In Vivo Validation is
                           achieved, whichever occurs first, by paying to Myogen
                           an option fee of [/\#/\] for each such
                           Extra-Collaboration Target or Active Compound.

         4.4. EXERCISE OF AN OPTION.

                  NIBRI may exercise an Option by delivery to Myogen of written
notice of exercise (an "Exercise Notice") no later than [/\#/\] after the filing
of an IND for the Development Candidate, specifying the Development Candidate as
to which such Option is being exercised. The parties shall then promptly execute
a License, Development and

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Commercialization Agreement identical in substance to Exhibit A hereto (the
"License Agreement"), the terms of which are incorporated by reference into, and
are a part of, this Agreement, pursuant to which NIBRI will use commercially
reasonable efforts (as defined in the License Agreement), to further develop and
commercialize the Development Candidate. Development of each Development
Candidate shall proceed as soon as practicable after the Option is exercised, in
accordance with the terms of the License Agreement. NIBRI agrees that, during
the term of this Agreement and after termination of this Agreement, it will not
develop and/or commercialize (either by itself or through a Third Party) an
Active Compound that has been selected for research or development in the course
of the Research Program because it has a potential therapeutic effect against
any of the Myogen Targets or Collaboration Targets except under the terms of the
License Agreement.

         4.5. EXPIRATION OF OPTIONS. Options expire as follows:

                  4.5.1 An Option on an Active Compound relating to a High
Priority Target will expire on the first to occur of:

                  (a)      [/\#/\]

                  (b)      [/\#/\]

                  (c)      [/\#/\]

                  4.5.2 An Option on an Active Compound relating to a Low
Priority Target will expire at the first to occur of:

                  (a)      [/\#/\]

                  (b)      [/\#/\]

                  (c)      [/\#/\]

                  (d)      [/\#/\]

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         4.6. RIGHTS TO DISCONTINUED COMPOUNDS.

                  In the event that NIBRI elects to discontinue any Research
Program with respect to any Myogen Target for which the parties have identified
a NIBRI Compound that acts on such Target, and NIBRI subsequently contemplates
collaborating with a Third Party with respect to development and/or
commercialization of the 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. The right of first negotiation
set out in this Section 4.6 shall survive [/\#/\] beyond any termination of this
Agreement.

                                   ARTICLE V

                                 CONFIDENTIALITY

         5.1. UNDERTAKING.

                  During the term of this Agreement, each party (the "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 Proprietary Party takes reasonable measures to protect, including but not
limited to Collaboration Technology.

                  (a)      The 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.

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                  (b)      The Receiving Party further agrees to refrain from
                           directly or indirectly taking any action which would
                           constitute or facilitate the unauthorized use or
                           disclosure of such information. The Receiving Party
                           may disclose such information to its Affiliates,
                           officers, employees and agents, to authorized
                           licensees and sublicensees, and to subcontractors in
                           connection with the development or manufacture of
                           Compounds or Development Candidates, as applicable,
                           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, however, that such Affiliates,
                           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)      The Receiving Party shall be liable for any
                           unauthorized use and disclosure of such information
                           by its Affiliates, officers, employees and agents and
                           any such sublicensees and subcontractors.

         5.2. EXCEPTIONS.

                  Notwithstanding the foregoing, the provisions of Section 5.1
hereof shall not apply to knowledge, information, documents or materials that
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

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                  (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 disclosing party as established by
                           written records.

                  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:

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

                  (II)     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.

         5.3. PUBLICITY.

                  The parties will agree upon the timing and content of any
initial press release or other public communications relating to this Agreement
and the transactions contemplated herein.

                  (a)      Except to the extent already disclosed in that
                           initial press release or other public communication,
                           no public announcement concerning the existence or
                           the terms of this Agreement or concerning the
                           transactions described herein shall be made, either
                           directly or indirectly, by Myogen or NIBRI, except as
                           may be legally required by applicable laws,
                           regulations, or judicial order, without first
                           obtaining the approval of the other party and
                           agreement upon the nature, text, and timing of such
                           announcement, which

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                           approval and agreement shall not be unreasonably
                           withheld.

                  (b)      The party desiring to make any such public
                           announcement shall provide the other party with a
                           written copy of the proposed announcement in
                           sufficient time prior to public release to allow such
                           other party to comment upon such announcement, prior
                           to public release.

         5.4. SURVIVAL.

                  The provisions of this Article V shall survive the termination
of this Agreement.

                                   ARTICLE VI

                                   PUBLICATION

         6.1. PUBLICATION.

                  Each of NIBRI and Myogen, and their respective Affiliates,
agree not to publish or publicly present any results, data, or scientific
findings with respect to the Research Program (except in connection with filings
with the Food and Drug Administration or another similar governmental entity)
without the prior written consent of the JSC. In the event of information
already within the public domain, consent shall not be unreasonably withheld if
sought at least thirty (30) days prior to planned submission for publication or
oral presentation. In all other instances during the term of this Agreement,
publication shall be presumed to be impermissible until the JSC shall have
determined, in its sole judgment, that the intellectual property rights of the
parties in such information first shall have been adequately protected, whether
by foreign filing of Patents or otherwise. To the extent that a proposed
publication of any results, data, or scientific findings with respect to the
Research Program is subject to the terms of Myogen's existing license
agreements, sponsored research agreements or material transfer agreements with
the University of Texas Southwestern Medical Center, the University of North
Texas Health Sciences Center or the University of Colorado, the procedure for
publication of such results, data or findings will be as specified in those
agreements.

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                                  ARTICLE VII

                                 INDEMNIFICATION

         7.1. INDEMNIFICATION BY MYOGEN.

                  Myogen will indemnify, defend, and hold NIBRI and its
Affiliates, their respective employees, shareholders, officers and directors and
the successors, heirs and assigns of each of them, harmless against any loss,
damages, action, suit, claim, demand, liability, expense, bodily injury, death
or property damage (a "Loss"), that may be brought, instituted or arise against
or be incurred by such persons to the extent such Loss is based on or arises out
of: (a) the breach by Myogen of any of its covenants, representations or
warranties set forth in this Agreement; or (b) the development or
commercialization of a Development Candidate, but excluding any such Loss that
is caused by the negligent or reckless acts or omissions of NIRBI.

         7.2. INDEMNIFICATION BY NIBRI.

                  NIBRI will indemnify, defend, and hold Myogen, and its
Affiliates, and their respective employees, shareholders, officers and directors
and the successors, heirs, and assigns of each of them, harmless against any
Loss that may be brought, instituted or arise against or be incurred by such
persons to the extent such Loss is based on or arises out of: (a) the breach by
NIBRI of any of its covenants, representations or warranties set forth in this
Agreement; or (b) the development or commercialization of a Development
Candidate, but excluding any such Loss that is caused by the negligent or
reckless acts or omissions of Myogen.

         7.3. CLAIMS PROCEDURES.

                  Each Party entitled to be indemnified by the other Party (an
"Indemnified Party") pursuant to Section 7.1 or 7.2 hereof shall give notice to
the other Party (an "Indemnifying Party") promptly after such Indemnified Party
has actual knowledge of any threatened or asserted claim as to which indemnity
may be sought, and shall permit the Indemnifying Party to

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assume the sole control of the defense of any such claim or any litigation
resulting therefrom; provided, however:

                  (a)      That counsel for the Indemnifying Party, who shall
                           conduct the defense of such claim or any litigation
                           resulting therefrom, shall be approved by the
                           Indemnified Party (whose approval shall not
                           unreasonably be withheld) and the Indemnified Party
                           may participate in such defense at such party's
                           expense (unless: (i) the employment of counsel by
                           such Indemnified Party has been authorized by the
                           Indemnifying Party; or (ii) the Indemnified Party
                           shall have reasonably concluded that there may be a
                           conflict of interest between the Indemnifying Party
                           and the Indemnified Party in the defense of such
                           action, in each of which cases the Indemnifying Party
                           shall pay the reasonable fees and expenses of one law
                           firm serving as counsel for the Indemnified Party,
                           which law firm shall be subject to approval, not to
                           be unreasonably withheld, by the Indemnifying Party);
                           and

                  (b)      The failure of any Indemnified Party to give notice
                           as provided herein shall not relieve the Indemnifying
                           Party of its obligations under this Agreement to the
                           extent that the failure to give notice did not result
                           in harm to the Indemnifying Party or materially
                           compromise the defense of such claim.

                  (c)      No Indemnifying Party, in the defense of any such
                           claim or litigation, shall consent to entry of any
                           judgment or enter into any settlement, except with
                           the approval of each Indemnified Party (which
                           approval shall not be unreasonably withheld), except
                           a settlement which imposes only a monetary obligation
                           on the Indemnifying Party and which includes as an
                           unconditional term thereof the giving of a release
                           from all liability in respect to such claim or
                           litigation by the claimant or plaintiff to the
                           Indemnified Party.

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                  (d)      Each Indemnified Party shall furnish such information
                           or reasonable assistance regarding itself or the
                           claim in question as an Indemnifying Party may
                           reasonably request in writing and shall be reasonably
                           required in connection with the defense of such claim
                           and litigation resulting therefrom.

         7.4. COMPLIANCE.

                  The parties shall comply fully with all applicable laws and
regulations in connection with their respective activities under this Agreement.

                                  ARTICLE VIII

                          INTELLECTUAL PROPERTY RIGHTS

         8.1. OWNERSHIP.

                  8.1.1. Subject to any licenses explicitly granted under this
Agreement or a License Agreement, each party shall retain its intellectual
property rights in all Technology Controlled by it on the Effective Date or
otherwise arising outside of the Research Program.

                  8.1.2. Any new invention created or any new Know-How generated
exclusively by a party or its Affiliate (directly or through others acting on
its behalf) prior to and during the term of this Agreement shall be owned by
such party; provided, however, that if such new invention or new Know-How of
Myogen is necessary to NIBRI's exercise of its license rights under a License
Agreement, then the definition of Myogen Technology will be deemed to include
such new invention or new Know-How that are included within the licenses granted
to NIBRI under the License Agreement.

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                  8.1.3. Any new invention created jointly by the parties shall
be jointly owned (a "Joint Invention"), and the respective rights of the parties
with respect to the Joint Invention 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.

                  8.1.4. NIBRI will retain ownership of all intellectual
property rights in and to the NIBRI Compounds. Myogen will take all reasonable
actions requested by NIBRI, including execution of appropriate transfer
documents, patent filings and applications for registration, to perfect NIBRI's
ownership interests in and to the NIBRI Compounds.

         8.2. PREPARATION AND COSTS.

                  Myogen shall take responsibility and pay for the preparation,
filing, prosecution and maintenance of all Myogen Patents, and NIBRI shall take
responsibility and pay for the preparation, filing, prosecution and maintenance
of: (a) all NIBRI Patents; (b) any patents and patent applications claiming
Joint Inventions; and (c) all Patents related to Development Candidates. Myogen
shall provide the JSC with periodic reports listing, by name, Myogen Patents
filed in the United States and other jurisdictions, along with a general summary
of the claims made and the jurisdictions of filing. In good time, before the
deadline for foreign filing of any patent application filed in the United
States, Myogen will notify NIBRI whether it intends to foreign file such patent
application, and if it intends to do so, in what countries it proposes to
foreign file. The parties hereby agree that to the extent legally possible and
commercially reasonable, the responsible party shall, at a minimum, prepare,
file, prosecute and maintain patent coverage as described in this section in the
countries listed in Schedule 8.2 hereto. NIBRI and Myogen agree to use all
commercially reasonable efforts to secure patent protection on any intellectual
property created during the Research Program. NIBRI will consult with Myogen on
the drafting and prosecution of patent applications on Joint Inventions that
relate to the Myogen Targets and/or the Collaboration Targets in the United
States and in countries listed in Schedule 8.2 that are commercially viable,
and, to the extent reasonably practicable under the

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circumstances, give Myogen an opportunity to comment and suggest revisions to
any patent application covering such Joint Inventions.

         8.3. DISCONTINUATION.

                  The party initially responsible under Section 8.2 for the
preparation, filing, prosecution and maintenance of a particular Patent shall
give at least thirty (30) days advance notice to the other party of any decision
to cease preparation, filing, prosecution and maintenance of that Patent in a
jurisdiction listed on Schedule 8.2 hereof. Discontinuation may be elected on a
country-by-country basis or for a Patent application or Patent series in total.
In such case, the other party may elect at its sole discretion to continue
preparation, filing, and prosecution or maintenance of the discontinued Patent
at its sole expense.

         8.4. ADVICE TO JSC ON INTELLECTUAL PROPERTY MATTERS.

                  The JSC shall appoint an intellectual property subcommittee
comprising appropriate legal counsel from each party to advise the JSC on
intellectual property protection issues. Such subcommittee shall report at least
quarterly to the JSC.

                                   ARTICLE IX

                              TERM AND TERMINATION

         9.1. TERM.

                  This Agreement will extend until the termination (including
any early termination hereunder) of the Research Program (including any
extension thereof), unless earlier terminated by either party hereto in
accordance with this Agreement, or unless extended by mutual agreement of the
parties.

         9.2. TERMINATION OF THE RESEARCH PROGRAM BY NIBRI FOR CAUSE.

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                  Upon written notice to Myogen, NIBRI may at its sole
discretion unilaterally terminate the Research Program and this Agreement upon
the occurrence of any of the following events:

                  (a)      Myogen shall breach any of its material obligations
                           under this Agreement or the License Agreement, and
                           such breach shall not have been remedied or steps
                           initiated to remedy the same to NIBRI's reasonable
                           satisfaction, within sixty (60) days after NIBRI
                           sends written notice of breach to Myogen;

                  (b)      Myogen shall cease to function as a going concern by
                           suspending or discontinuing its business for any
                           reason except for interruptions caused by Force
                           Majeure, strike, labor dispute or any other events
                           over which it has no control; or

                  (c)      Upon a 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
                           subsequent to the transaction, in either case to an
                           entity or an Affiliate thereof reasonably conceived
                           by NIBRI to be a NIBRI Competitor.

                  In the event of any valid termination under this Section 9.2,
NIBRI shall not be required to make any payments under Section 3.3 hereof which
are not due and payable prior to receipt by Myogen of the notice of breach
referenced under Section 9.2(a) or receipt by Myogen of the notice of
termination pursuant to Section 9.2(b), as the case may be. Notwithstanding the
foregoing, any License Agreement then in effect shall continue in effect unless
it is expressly terminated in accordance with its terms.

         9.3. TERMINATION OF THE RESEARCH PROGRAM BY MYOGEN FOR CAUSE.

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                  Myogen may at its sole discretion terminate the Research
Program and this Agreement upon written notice to NIBRI upon the occurrence of
any of the following events:

                  (a)      NIBRI shall breach any of its material obligations
                           under this Agreement or the License Agreement and
                           such breach shall not have been remedied or steps
                           initiated to remedy the same to Myogen's reasonable
                           satisfaction, within sixty (60) days after Myogen
                           sends written notice of breach to NIBRI; or

                  (b)      NIBRI shall cease to function as a going concern by
                           suspending or discontinuing its business for any
                           reason except for interruptions caused by Force
                           Majeure, strike, labor dispute or any other events
                           over which it has no control, and no Affiliate of
                           NIBRI shall have assumed NIBRI's function.

                  Upon any termination under Section 9.3(a), all licenses and
other rights (including Options) granted hereunder shall also terminate.
Notwithstanding the foregoing, any License Agreement then in effect shall
continue in effect unless it is expressly terminated in accordance with its
terms.

         9.4. EARLY TERMINATION OF THE RESEARCH PROGRAM BY NIBRI.

                  In the event that, in its reasonable, good faith judgment, the
overall Research Program is proceeding unsatisfactorily, NIBRI may in its
absolute discretion terminate its participation in the Research Program
effective no earlier than eighteen (18) months from the Effective Date, upon
sixty (60) days' prior written notice to Myogen. [/\#/\]

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         9.5. EFFECT OF TERMINATION.

                  Except where explicitly provided elsewhere herein, termination
of this Agreement for any reason, or expiration of this Agreement, will not
affect: (a) obligations which have accrued as of the date of termination or
expiration; and (b) obligations and rights which, expressly or from the context
thereof, are intended to survive termination or expiration of this Agreement,
including but not limited to obligations of confidentiality under Section 2.5.2,
Article V hereof and the indemnification provisions of Article VII hereof.
Except as otherwise provided hereunder, all licenses granted under this
Agreement shall terminate upon termination or expiration of this Agreement.

                                   ARTICLE X

                         REPRESENTATIONS AND WARRANTIES

         10.1. REPRESENTATIONS AND WARRANTIES OF MYOGEN.

                  Myogen represents and warrants to NIBRI as follows:

                  (a)      AUTHORIZATION. This Agreement has been duly executed
                           and delivered by Myogen and constitutes the valid and
                           binding obligation of Myogen, enforceable against
                           Myogen in accordance with its terms except as
                           enforceability may be limited by bankruptcy,
                           fraudulent conveyance, insolvency, bankruptcy,
                           reorganization, moratorium and other laws relating to
                           or affecting creditors' rights generally and by
                           general equitable principles. The execution, delivery
                           and performance of this Agreement have been duly
                           authorized by all necessary action on the part of
                           Myogen, its officers and directors. No provision of
                           this Agreement violates any other agreement that
                           Myogen may have with any other person or company, and
                           Myogen acknowledges that NIBRI has relied on that
                           representation in entering into this Agreement.

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                  (b)      MYOGEN CONTROLLED RIGHTS. As of the Effective Date,
                           Myogen owns or possesses adequate licenses or other
                           rights to use all Myogen Technology relating to the
                           Myogen Compounds and Myogen Targets and to grant the
                           licenses and perform the obligations contemplated
                           herein, except to the extent that Myogen's agreements
                           with Third Party licensors contain restrictions on
                           further sublicense by NIBRI. The granting of an
                           Option to NIBRI hereunder does not violate any right
                           known to Myogen of any Third Party.

                  (c)      THIRD PARTY PATENTS. Except as disclosed in writing
                           between the parties to this Agreement or their
                           respective agents, as of the Effective Date, to
                           Myogen's knowledge there are no issued patents or
                           pending patent applications that, if issued, would be
                           infringed by the development, manufacture, use or
                           sale of any Myogen Compound or Myogen Target, as
                           applicable, pursuant to this Agreement.

         10.2. REPRESENTATIONS AND WARRANTIES OF NIBRI.

                  NIBRI represents and warrants to Myogen that this Agreement
has been duly executed and delivered by NIBRI and constitutes the valid and
binding obligation of NIBRI, enforceable against NIBRI in accordance with its
terms except as enforceability may be limited by bankruptcy, fraudulent
conveyance, insolvency, bankruptcy, reorganization, moratorium and other laws
relating to or affecting creditors' rights generally and by general equitable
principles. The execution, delivery and performance of this Agreement have been
duly authorized by all necessary action on the part of NIBRI, its officers and
directors. No provision of this Agreement violates any other agreement that
NIBRI may have with any other person or company, and NIBRI acknowledges that
Myogen has relied on that representation in entering into this Agreement.

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<PAGE>
                                   ARTICLE XI

                               DISPUTE RESOLUTION

         11.1. GOVERNING LAW, AND JURISDICTION.

                  This Agreement shall be governed and construed in accordance
with the internal laws of the Commonwealth of Massachusetts.

         11.2. DISPUTE RESOLUTION PROCESS.

                  Except with respect to any matters under the purview of the
JSC pursuant to Section 2.7.1, and except for any claim or controversy relating
to a Critical Issue pursuant to Section 2.7.2 and Section 11.3, in the event of
any controversy or claim arising out of or relating to the legal rights and
remedies of the parties arising out of this Agreement, the parties shall, and
either party may, initially refer such dispute to the JSC, and failing
resolution of the controversy or claim within thirty (30) days after such
referral, the matter shall be referred to the President and Chief Executive
Officer of Myogen and the President and Chief Executive Officer of NIBRI who
shall, as soon as practicable, attempt in good faith to resolve the controversy
or claim. If such controversy or claim is not resolved within sixty (60) days of
the date of initial referral of the matter to the JSC, either party may submit
the dispute to any court of competent jurisdiction for resolution.

         11.3. DISPUTE RESOLUTION PROCESS FOR CRITICAL ISSUES.

                  In the event of any controversy or claim arising out of or
relating to a Critical Issue which the JSC is unable to resolve under Section
2.7.2, the parties shall refer the matter to the President and Chief Executive
Officer of Myogen and the President and Chief Executive Officer of NIBRI who
shall attempt in good faith and using their best efforts to resolve the
controversy or claim within sixty (60) days of the date of initial referral of
the matter from the JSC. If such controversy or claim is not resolved within
sixty (60) days, then Myogen may, at its election, either: (a) accept the final
position of the President and Chief Executive Officer of

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NIBRI with respect to such matter; or (b) terminate this Agreement on thirty
(30) days' written notice, subject to the provisions of Section 9.5. Section 9.4
shall not apply to any termination of this Agreement by Myogen pursuant to the
immediately-preceding subsection (b).

                                  ARTICLE XII

                            MISCELLANEOUS PROVISIONS

         12.1. WAIVER.

                  No provision of this Agreement may be waived except in writing
by both parties hereto. No failure or delay by either party hereto in exercising
any right or remedy hereunder or under applicable law will operate as a waiver
thereof, or a waiver of any right or remedy on any subsequent occasion.

         12.2. 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.

         12.3. SEVERABILITY.

                  Should one or more provisions of this Agreement be or become
invalid, then the parties hereto shall attempt 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

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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.

         12.4. GOVERNMENT ACTS.

                  In the event that any act, regulation, directive, or law of a
country or its government, 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 therein as may be necessary to fairly address the impact
thereof, are not successful after a reasonable period of time in producing
mutually acceptable modifications to this Agreement.

         12.5. GOVERNMENT APPROVALS.

                  Each party will use commercially reasonable best efforts to
obtain any government approval required in its country of domicile 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. Each party
will keep the other informed of progress in obtaining any such government
approval, and will cooperate with the other party in any such efforts.

         12.6. EXPORT CONTROLS.

                  This Agreement is made subject to any restrictions concerning
the export of materials and 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, each of NIBRI and Myogen
agrees that it will not export, directly or indirectly, any technical
information acquired from the other party under this Agreement or any products
using such technical information to any countries for which the United States
Government or any agency

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thereof at the time of export requires an export license or other governmental
approval, without first obtaining the written consent to do so from the
Department of Commerce or other agency of the United States Government when
required by applicable statute or regulation.

         12.7. ASSIGNMENT.

                  This Agreement may not be assigned or otherwise transferred by
either party without the prior written consent of the other party; provided,
however, that (a) NIBRI may assign this Agreement, without the consent of
Myogen: (i) to any of its Affiliates; or (ii) 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; and (b) Myogen may assign this
Agreement, without the consent of NIBRI 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 Person, provided, however, that any such
transaction in which a NIBRI Competitor acquires all of Myogen's assets or
business or merges with Myogen, NIBRI may terminate this Agreement pursuant to
Section 9.2(c). Any purported assignment in contravention of this Section 12.7
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.

         12.8. AFFILIATES.

                  Each party may perform its obligations hereunder personally or
through one or more Affiliates, although each party shall nonetheless be solely
responsible for the performance of its Affiliates. Neither party shall permit
any of its Affiliates to commit any act (including any act or omission) which
such party is prohibited hereunder from committing directly. The use of
subcontractors by either party shall not increase the financial obligations of
the other party hereunder in any respect.

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         12.9. COUNTERPARTS.

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

         12.10. NO AGENCY.

                  Nothing herein contained shall be deemed to create an agency,
joint venture, amalgamation, partnership or similar relationship between NIBRI
and Myogen and their respective Affiliates. 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.

         12.11. 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 such 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 W. 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

         12.12. 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.

         12.13. AUTHORITY.

                  The undersigned represent that they are authorized to sign
this Agreement on behalf of the parties hereto.

         12.14. ENTIRE AGREEMENT.

                  This Agreement contains the entire understanding of the
parties relating to the

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matters referred to herein, and may only be amended by a written document, duly
executed on behalf of the respective parties.

         12.15. NOTICE OF PHARMACEUTICAL SIDE-EFFECTS.

                  During the term of this Agreement, the parties shall keep each
other and the JSC 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 a Compound.

         12.16. INVOICE REQUIREMENT.

                  Any amounts payable to Myogen hereunder (except any royalty
payments required to be made under the provisions of Article IV of the License
Agreement) shall be made within thirty (30) days after receipt by NIBRI, or its
nominee designated for that purpose in advance by NIBRI in writing to Myogen, of
an invoice covering such payment.

                            [Signature page follows]

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<PAGE>

                              MYOGEN, INC.

                              By: /s/ J. William Freytag
                                  ----------------------------------------------
                                  J. William Freytag
                                  Title: President and Chief Executive Officer

                              NOVARTIS INSTITUTES FOR BIOMEDICAL
                              RESEARCH, INC.

                              By: /s/ Mark Fishman
                                  ----------------------------------------------
                                  Mark Fishman, M.D.
                                  Title: President and Chief Executive Officer

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                                  SCHEDULE 1.24

                                 MYOGEN PATENTS

--------------------------------------------------------------------------------

<Table>
<Caption>
PATENTS           FILING DATE       APP. NO.       COUNTRY      PAT. NO. ISSUE DATE  SUBJECT MATTER
-------           -----------       --------       -------      -------- ----------  --------------
<S>               <C>           <C>              <C>           <C>       <C>         <C>
MYOG:004-USD1      4/25/2000       09/558,472        U.S.                            Alpha Myosin Heavy Chain Gene Therapy
MYOG:004-USD2      10/1/2001       09/969,086        U.S.                            Alpha Myosin Heavy Chain Therapeutic/Screening
MYOG:004-WO        1/30/1998     PCT/US98/01983      PCT                             Alpha Myosin Heavy Chain
MYOG:004-CA        7/29/1999       2,278,465        Canada                           Alpha Myosin Heavy Chain
MYOG:004-EP        7/30/1999       98906089.2       Europe                           Alpha Myosin Heavy Chain
MYOG:004-JP        7/30/1999       10-533182        Japan                            Alpha Myosin Heavy Chain
MYOG:005-US         4/1/1998       09/053,293        U.S.      6,218,597  4/17/2001  Transgenic mice w/cardiac specific promoters
MYOG:006-US        9/26/1997       08/938,105        U.S.      6,353,151  3/5/2002   Transgeneic alpha myosin
MYOG:006-EP        5/24/1999       97943597.1       Europe                           Alpha Myosin Transgenes
MYOG:007-US        5/26/1998       09/047,755        U.S.      6,203,776  3/20/2001  Methods for identify adrenergic receptors
MYOG:020-US       10/15/1998       09/173,798        U.S.      6,201,165  3/13/2001  CamKIIa, CaMKIV,p38,MKK6,anf,bnp,beta myosin
                                                                                     transgenes
MYOG:020-WO       10/16/1998     PCT/US98/21988      PCT                             CamKIIa, CaMKIV,p38,MKK6,anf,bnp,beta myosin
                                                                                     transgenes
MYOG:020-AU        4/16/2000        10992/99      Australia       755429  8/16/2002  CamKIIa, CaMKIV,p38,MKK6,anf,bnp,beta myosin
                                                                                     transgenes
MYOG:020-EP        4/16/2000       98953672.7       Europe                           CamKIIa, CaMKIV,p38,MKK6,anf,bnp,beta myosin
                                                                                     transgenes
MYOG:020-JP        4/16/2000      2000-516026       Japan                            CamKIIa, CaMKIV,p38,MKK6,anf,bnp,beta myosin
                                                                                     transgenes
MYOG:020-MX        4/14/2000        0003678         Mexico                           CamKIIa, CaMKIV,p38,MKK6,anf,bnp,beta myosin
                                                                                     transgenes
MYOG:023-US       10/15/1998       09/173,795        U.S.        issue fee paid      transgenics
MYOG:024-US       11/10/1999       09/438,075        U.S.      6,372,957  4/16/2002  MEF2 methods of treatment
MYOG:024-USC1      1/9/2002        10/043,658        U.S.                            MEF2 screening methods
MYOG:024-WO       11/10/1999     PCT/US99/26725      PCT                             MEF2
MYOG:024-CA        5/7/2001        2,350,086        Canada                           MEF2
MYOG:024-EP        5/21/2001       99971848.9       Europe                           MEF2
MYOG:024-JP        5/10/2001      2000-581187       Japan                            MEF2
MYOG:025-US       10/15/1998       09/173,799        U.S.        issue fee paid      transgenics
MYOG:026-US        8/20/2000       09/643,206        U.S.        issue fee paid      HDAC screening and treatment
MYOG:026-USD1      8/20/2003    not yet assigned     U.S.                            HDAC transgenes
MYOG:026-WO        8/20/2000     PCT/US00/22958      PCT                             HDAC screening and treatment and transgenes
MYOG:026-CA        2/14/2002       2,382,045        Canada                           HDAC screening and treatment and transgenes
MYOG:026-EP        3/13/2002       00955805.7       Europe                           HDAC screening and treatment and transgenes
MYOG:026-JP        2/19/2002      2001-518892       Japan                            HDAC screening and treatment and transgenes
MYOG:028-US        7/18/2001       09/908,988        U.S.                            Muscle Ring Finger Proteins (MURFS) Screening
                                                                                     and Treatment
MYOG:028-WO        7/18/2001     PCT/US01/22896      PCT                             Muscle Ring Finger Proteins (MURFS) Screening
                                                                                     and Treatment
MYOG:029-US        4/16/1998       09/061,417        U.S.                            NF-AT3 inhibitors
MYOG:029-WO       10/16/1998     PCT/US98/21845      PCT                             NF-AT3 inhibitors
MYOG:029-AU       10/15/1998        98058/98      Australia       748334  9/12/2002  NF-AT3 inhibitors
MYOG:029-CA        4/10/2000       2,306,448        Canada                           NF-AT3 inhibitors
MYOG:029-EP        5/16/2000       9895233.7        Europe                           NF-AT3 inhibitors
MYOG:029-JP        4/17/2000      2000-516024       Japan                            NF-AT3 inhibitors
MYOG:035-USP1      1/22/2002       converted         U.S.                            Hypertrophic Cell Line
MYOG:035-USP2      2/11/2002       converted         U.S.                            Hypertrophic Cell Line
MYOG:035-US        1/21/2003       10/348,58         U.S.                            Hypertrophic Cell Line
MYOG:035-WO        1/21/2003     PCT/US03/62471      PCT                             Hypertrophic Cell Line
MYOG:036-US        2/13/2001       09/782,953        U.S.                            MCIP's screening, treatment, transgenics,
                                                                                     antibodies
MYOG:036-WO        2/13/2001     PCT/US01/21662      PCT                             MCIP's screening, treatment, transgenics,
                                                                                     antibodies
MYOG:036-CA        1/24/2003       2,415,967        Canada                           MCIP's screening, treatment, transgenics,
                                                                                     antibodies
MYOG:036-EP        2/5/2003        1952568.2        Europe                           MCIP's screening, treatment, transgenics,
                                                                                     antibodies
MYOG:036-JP       12/26/2002      2002-509354       Japan                            MCIP's screening, treatment, transgenics,
                                                                                     antibodies
MYOG:037-USP1      8/20/2002       converted         U.S.                            STARS screening, treatment, transgenics,
                                                                                     antibodies
MYOG:037-US        8/20/2003    not yet assigned     U.S.                            STARS screening, treatment, transgenics,
                                                                                     antibodies
MYOG:037-WO        8/20/2003     PCT/US03/10179      PCT                             STARS screening, treatment, transgenics,
                                                                                     antibodies
MYOG:044-USP1      5/21/2003    not yet assigned     U.S.                            HDAC Kinase
UTEC:007-USP1      11/1/2002       60/423,019        U.S.                            MALDI-TOF use as measure of intracellular
                                                                                     protein concentration
UTEC:007-USP2      11/2/2002       60/423,142        U.S.                            MALDI-TOF use as measure of intracellular
                                                                                     protein concentration
UTSD:729-US        11/7/2001       10/045,594        U.S.                            CALSARCINS
UTSD:729-WO        11/7/2001     PCT/US01/49861      PCT                             CALSARCINS
UTSD:729-CA        11/7/2001       2,425,396        Canada                           CALSARCINS
UTSD:729-EP        11/7/2001    not yet assigned    Europe                           CALSARCINS
UTSD:729-JP        11/7/2001      2002-548136       Japan                            CALSARCINS
UTSD:803-US        5/30/2002       10/159,971        U.S.                            MEK5
UTSD:803-CA        5/29/2002       2,384,907        Canada                           MEK5
UTSD:803-JP       11/22/2001      2001-358595       Japan                            MEK5
UTSD:845-US        3/4/2002        10/379,375        U.S.                            Transgenes
UTSD:845-CA        5/9/2002        2,385,734        Canada                           Transgenes
UTSD:845-JP       11/19/2001      2001-353806       Japan                            Transgenes
</Table>

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                                  SCHEDULE 1.25

                                 MYOGEN TARGETS

--------------------------------------------------------------------------------

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                                 SCHEDULE 2.3.1

                                  RESEARCH PLAN

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                                  SCHEDULE 8.2

                  LIST OF COUNTRIES REGARDING PATENT PROTECTION

--------------------------------------------------------------------------------

<Table>
<Caption>
<S>                                      <C>                                    <C>
Albania AL                               Algeria DZ                             Antigua and Barbuda AG
---------------------------------------- -------------------------------------- --------------------------------------
Argentina                                Armenia AM                             Australia AU
---------------------------------------- -------------------------------------- --------------------------------------
Austria AT                               Azerbaijan AZ                          Barbados BB
---------------------------------------- -------------------------------------- --------------------------------------
Belarus BY                               Belgium BE                             Belize BZ
---------------------------------------- -------------------------------------- --------------------------------------
Benin BJ                                 Bosnia and Herzegovina BA              Botswana BW
---------------------------------------- -------------------------------------- --------------------------------------
Brazil BR                                Bulgaria BG                            Burkina Faso BF
---------------------------------------- -------------------------------------- --------------------------------------
Cameroon CM                              Canada CA                              Central African Republic CF
---------------------------------------- -------------------------------------- --------------------------------------
Chad TD                                  Chile                                  China CN
---------------------------------------- -------------------------------------- --------------------------------------
Colombia CO                              Congo CG                               Costa Rica CR
---------------------------------------- -------------------------------------- --------------------------------------
Cote d'Ivoire CI                         Croatia HR                             Cuba CU
---------------------------------------- -------------------------------------- --------------------------------------
Cyprus CY                                Czech Republic CZ                      Democratic People's Republic of
                                                                                Korea KP
---------------------------------------- -------------------------------------- --------------------------------------
Denmark DK                               Dominica DM                            Ecuador EC
---------------------------------------- -------------------------------------- --------------------------------------
Egypt EG                                 Equatorial Guinea GQ                   Estonia EE
---------------------------------------- -------------------------------------- --------------------------------------
Finland FI 2                             France FR                              Gabon GA
---------------------------------------- -------------------------------------- --------------------------------------
Gambia GM                                Georgia GE                             Germany DE
---------------------------------------- -------------------------------------- --------------------------------------
Ghana GH                                 Greece GR                              Grenada GD
---------------------------------------- -------------------------------------- --------------------------------------
Guinea GN                                Guinea-Bissau GW                       Hong Kong
---------------------------------------- -------------------------------------- --------------------------------------
Hungary HU                               Iceland IS                             India IN
---------------------------------------- -------------------------------------- --------------------------------------
Indonesia ID                             Ireland IE                             Israel IL
---------------------------------------- -------------------------------------- --------------------------------------
Italy IT                                 Japan JP                               Kazakhstan KZ 1
---------------------------------------- -------------------------------------- --------------------------------------
Kenya KE                                 Kyrgyzstan KG                          Latvia LV
---------------------------------------- -------------------------------------- --------------------------------------
Lesotho LS                               Liberia LR                             Liechtenstein LI
---------------------------------------- -------------------------------------- --------------------------------------
Lithuania LT                             Luxembourg LU                          Madagascar MG
---------------------------------------- -------------------------------------- --------------------------------------
Malawi MW                                Malaysia                               Mali ML
---------------------------------------- -------------------------------------- --------------------------------------
Mauritania MR                            Mexico MX                              Monaco MC
---------------------------------------- -------------------------------------- --------------------------------------
Mongolia MN                              Morocco MA                             Mozambique MZ
---------------------------------------- -------------------------------------- --------------------------------------
Netherlands NL 4                         New Zealand NZ                         Nicaragua NI
---------------------------------------- -------------------------------------- --------------------------------------
Niger NE                                 Norway NO                              Oman OM
---------------------------------------- -------------------------------------- --------------------------------------
Pakistan                                 Papua New Guinea PG                    Peru
---------------------------------------- -------------------------------------- --------------------------------------
Philippines PH                           Poland PL                              Portugal PT
---------------------------------------- -------------------------------------- --------------------------------------
Republic of Korea KR                     Republic of Moldova MD                 Romania RO
---------------------------------------- -------------------------------------- --------------------------------------
Russian Federation RU                    Saint Lucia LC                         Saint Vincent and the Grenadines VC
---------------------------------------- -------------------------------------- --------------------------------------
Saudi Arabia                             Senegal SN                             Serbia and Montenegro CS
---------------------------------------- -------------------------------------- --------------------------------------
Seychelles SC                            Sierra Leone SL                        Singapore SG
---------------------------------------- -------------------------------------- --------------------------------------
Slovakia SK                              Slovenia SI                            South Africa ZA
---------------------------------------- -------------------------------------- --------------------------------------
Spain ES                                 Sri Lanka LK                           Sudan SD
---------------------------------------- -------------------------------------- --------------------------------------
Swaziland SZ                             Sweden SE                              Switzerland CH
---------------------------------------- -------------------------------------- --------------------------------------
Syrian Arab Republic SY                  Taiwan                                 Tajikistan TJ
---------------------------------------- -------------------------------------- --------------------------------------
Thailand                                 The former Yugoslav Republic of        Togo TG
                                         Macedonia MK
---------------------------------------- -------------------------------------- --------------------------------------
Trinidad and Tobago TT                   Tunisia TN                             Turkey TR
---------------------------------------- -------------------------------------- --------------------------------------
Turkmenistan TM                          Uganda UG                              Ukraine UA
---------------------------------------- -------------------------------------- --------------------------------------
United Arab Emirates AE                  United Kingdom GB                      United Republic of Tanzania TZ
---------------------------------------- -------------------------------------- --------------------------------------
United States of America US              Uruguay                                Uzbekistan UZ
---------------------------------------- -------------------------------------- --------------------------------------
Venezuela                                Viet Nam VN                            Zambia ZM
---------------------------------------- -------------------------------------- --------------------------------------
Zimbabwe ZW
</Table>

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                                    EXHIBIT A

          FORM OF LICENSE, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

--------------------------------------------------------------------------------

  [Filed separately as Exhibit 10.25 to the Registration Statement on Form S-1]

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           Collaboration and Option Agreement - Confidential

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