Document:

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                                                                   EXHIBIT 10.16

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED OR ANY STATE SECURITIES LAWS. NO SALE OR DISPOSITION MAY BE EFFECTED
WITHOUT (i) EFFECTIVE REGISTRATION STATEMENTS RELATED THERETO, (ii) AN OPINION
OF COUNSEL OR OTHER EVIDENCE, REASONABLY SATISFACTORY TO THE COMPANY, THAT SUCH
REGISTRATIONS ARE NOT REQUIRED, (iii) RECEIPT OF NO-ACTION LETTERS FROM THE
APPROPRIATE GOVERNMENTAL AUTHORITIES, OR (iv) OTHERWISE COMPLYING WITH THE
PROVISIONS OF SECTION 7 OF THIS WARRANT.

                                  MYOGEN, INC.

                           WARRANT TO PURCHASE SHARES
                            OF SERIES PREFERRED STOCK

         THIS CERTIFIES THAT, for value received, SILICON VALLEY BANK and its
assignees are entitled to subscribe for and purchase that number of the fully
paid and nonassessable shares of Series Preferred Stock (as adjusted pursuant to
Section 4 hereof, the "Shares") of MYOGEN, INC., a Delaware corporation (the
"Company"), as is determined pursuant to the next paragraph hereof at the price
per share as is determined pursuant to the next paragraph hereof (such price and
such other price as shall result, from time to time, from the adjustments
specified in Section 4 hereof is herein referred to as the "Warrant Price"),
subject to the provisions and upon the terms and conditions hereinafter set
forth. As used herein, (a) the term "Series Preferred" shall mean, (i) if the
Qualified Financing Price (as defined below) is greater than $1.375 per share,
the Company's presently authorized Series D Preferred Stock, and any stock into
or for which such Series D Preferred Stock may hereafter be converted or
exchanged, and after the automatic conversion of the Series D Preferred Stock to
Common Stock shall mean the Company's Common Stock, or (ii) if the Qualified
Financing Price is not greater than $1.375 per share, the Company's convertible
preferred stock sold in the Qualified Financing ("Next Round Preferred Stock"),
and any stock into or for which such Next Round Preferred Stock may hereafter be
converted or exchanged, and after the automatic conversion of the Next Round
Preferred Stock to Common Stock shall mean the Company's Common Stock, (b) the
term "Date of Grant" shall mean December 6 2002, and (c) the term "Other
Warrants" shall mean any other warrants issued by the Company in connection with
the transaction with respect to which this Warrant was issued, and any warrant
issued upon transfer or partial exercise of or in lieu of this Warrant. The term
"Warrant" as used herein shall be deemed to include Other Warrants unless the
context clearly requires otherwise.

                  The Warrant Price shall be the lower of (i) $1.375 and (ii)
the lowest effective price per share (on a common stock equivalent basis and
taking into account any securities issued together with the preferred stock) at
which shares of the Company's convertible preferred stock are sold in a
Qualified Financing ("Qualified Financing Price"); provided, however, if a
Qualified Financing has not closed prior to the exercise of this Warrant, then
the Warrant Price shall be $1.375 and the Series Preferred shall mean the
Company's Series D Preferred Stock. A "Qualified Financing" shall mean the sale
of the convertible preferred stock of the Company to purchasers which include
venture capital investors in an aggregate cash amount not less than $3,000,000.
The number of shares for which this Warrant is exercisable shall be the nearest
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whole number determined by dividing $180,000 by the Warrant Price determined
pursuant to this paragraph.

         1. Term. The purchase right represented by this Warrant is exercisable,
in whole or in part, at any time and from time to time from the Date of Grant
through the later of (i) ten (10) years after the Date of Grant or (ii) five (5)
years after the closing of the Company's initial public offering of its Common
Stock ("IPO") effected pursuant to a Registration Statement on Form S-1 (or its
successor) filed under the Securities Act of 1933, as amended (the "Act").

         2. Method of Exercise; Payment; Issuance of New Warrant. Subject to
Section 1 hereof, the purchase right represented by this Warrant may be
exercised by the holder hereof, in whole or in part and from time to time, at
the election of the holder hereof, by (a) the surrender of this Warrant (with
the notice of exercise substantially in the form attached hereto as Exhibit A-1
duly completed and executed) at the principal office of the Company and by the
payment to the Company, by certified or bank check, or by wire transfer to an
account designated by the Company (a "Wire Transfer") of an amount equal to the
then applicable Warrant Price multiplied by the number of Shares then being
purchased; (b) if in connection with a registered public offering of the
Company's securities, subject to Section 7(c) below, the surrender of this
Warrant (with the notice of exercise form attached hereto as Exhibit A-2 duly
completed and executed) at the principal office of the Company together with
notice of arrangements reasonably satisfactory to the Company for payment to the
Company either by certified or bank check or by Wire Transfer from the proceeds
of the sale of shares to be sold by the holder in such public offering of an
amount equal to the then applicable Warrant Price per share multiplied by the
number of Shares then being purchased; or (c) exercise of the "net issuance"
right provided for in Section 10.2 hereof. The person or persons in whose
name(s) any certificate(s) representing shares of Series Preferred shall be
issuable upon exercise of this Warrant shall be deemed to have become the
holder(s) of record of, and shall be treated for all purposes as the record
holder(s) of, the shares represented thereby (and such shares shall be deemed to
have been issued) immediately prior to the close of business on the date or
dates upon which this Warrant is exercised. In the event of any exercise of the
rights represented by this Warrant, certificates for the shares of stock so
purchased shall be delivered to the holder hereof as soon as possible and in any
event within thirty (30) days after such exercise and, unless this Warrant has
been fully exercised or expired, a new Warrant representing the portion of the
Shares, if any, with respect to which this Warrant shall not then have been
exercised shall also be issued to the holder hereof as soon as possible and in
any event within such thirty-day period; provided, however, at such time as the
Company is subject to the reporting requirements of the Securities Exchange Act
of 1934, as amended, if requested by the holder of this Warrant, the Company
shall cause its transfer agent to deliver the certificate representing Shares
issued upon exercise of this Warrant to a broker or other person (as directed by
the holder exercising this Warrant) within the time period required to settle
any trade made by the holder after exercise of this Warrant.

         3. Stock Fully Paid; Reservation of Shares. All Shares that may be
issued upon the exercise of the rights represented by this Warrant will, upon
issuance pursuant to the terms and conditions herein, be fully paid and
nonassessable, and free from all preemptive rights and taxes, liens and charges
with respect to the issue thereof. During the period within which the rights
represented by this Warrant may be exercised, the Company will at all times have
authorized, and reserved for the purpose of the issue upon exercise of the
purchase rights evidenced by this

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Warrant, a sufficient number of shares of its Series Preferred to provide for
the exercise of the rights represented by this Warrant and a sufficient number
of shares of its Common Stock to provide for the conversion of the Series
Preferred into Common Stock.

         4. Adjustment of Warrant Price and Number of Shares. The number and
kind of securities purchasable upon the exercise of this Warrant and the Warrant
Price shall be subject to adjustment from time to time upon the occurrence of
certain events, as follows:

            (a) Reclassification or Merger. In case of any reclassification or
change of securities of the class issuable upon exercise of this Warrant (other
than a change in par value, or from par value to no par value, or from no par
value to par value, or as a result of a subdivision or combination), or in case
of any merger of the Company with or into another corporation or any other
corporate reorganization, in which the stockholders of the Company immediately
prior to such consolidation, merger or reorganization, own less than fifty
percent (50%) of the Company's voting power immediately after such
consolidation, merger or reorganization, or any transaction or series of related
transactions in which in excess of fifty percent (50%) of the Company's voting
power is transferred (other than (A) a Sale of the Company as defined in Section
10.1 or (B) a merger with another corporation in which the Company is the
acquiring and the surviving corporation and which does not result in any
reclassification or change of outstanding securities issuable upon exercise of
this Warrant), or in case of any sale of all or substantially all of the assets
of the Company, the Company, or such successor or purchasing corporation, as the
case may be, shall duly execute and deliver to the holder of this Warrant a new
Warrant (in form and substance satisfactory to the holder of this Warrant), so
that the holder of this Warrant shall have the right to receive upon exercise of
this Warrant, at a total purchase price not to exceed that payable upon the
exercise of the unexercised portion of this Warrant, and in lieu of the shares
of Series Preferred theretofore issuable upon exercise of this Warrant, (i) the
kind and amount of shares of stock, other securities, money and property
receivable upon such reclassification, change, merger or sale by a holder of the
number of shares of Series Preferred then purchasable under this Warrant, or
(ii) in the case of such a merger or sale in which the consideration paid
consists all or in part of assets other than securities of the successor or
purchasing corporation, at the option of the holder of this Warrant, the
securities of the successor or purchasing corporation having a value at the time
of the transaction equivalent to the value of the Series Preferred purchasable
upon exercise of this Warrant at the time of the transaction. Any new Warrant
shall provide for adjustments that shall be as nearly equivalent as may be
practicable to the adjustments provided for in this Section 4. The provisions of
this Section 4(a) shall similarly apply to successive reclassifications,
changes, mergers and sales.

            (b) Subdivision or Combination of Shares. If the Company at any time
while this Warrant remains outstanding and unexpired shall subdivide or combine
its outstanding shares of Series Preferred, the Warrant Price shall be
proportionately decreased and the number of Shares issuable hereunder shall be
proportionately increased in the case of a subdivision and the Warrant Price
shall be proportionately increased and the number of Shares issuable hereunder
shall be proportionately decreased in the case of a combination.

            (c) Stock Dividends and Other Distributions. If the Company at any
time while this Warrant is outstanding and unexpired shall (i) pay a dividend
with respect to Series Preferred payable in Series Preferred, then the Warrant
Price shall be adjusted, from and after the

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date of determination of shareholders entitled to receive such dividend or
distribution, to that price determined by multiplying the Warrant Price in
effect immediately prior to such date of determination by a fraction (A) the
numerator of which shall be the total number of shares of Series Preferred
outstanding immediately prior to such dividend or distribution, and (B) the
denominator of which shall be the total number of shares of Series Preferred
outstanding immediately after such dividend or distribution; or (ii) make any
other distribution with respect to Series Preferred (except any distribution
specifically provided for in Sections 4(a) and 4(b)), then, in each such case,
provision shall be made by the Company such that the holder of this Warrant
shall receive upon exercise of this Warrant a proportionate share of any such
dividend or distribution as though it were the holder of the Series Preferred
(or Common Stock issuable upon conversion thereof) as of the record date fixed
for the determination of the shareholders of the Company entitled to receive
such dividend or distribution.

            (d) Adjustment of Number of Shares. Upon each adjustment in the
Warrant Price, the number of Shares of Series Preferred purchasable hereunder
shall be adjusted, to the nearest whole share, to the product obtained by
multiplying the number of Shares purchasable immediately prior to such
adjustment in the Warrant Price by a fraction, the numerator of which shall be
the Warrant Price immediately prior to such adjustment and the denominator of
which shall be the Warrant Price immediately thereafter.

            (e) Antidilution Rights. The other antidilution rights applicable to
the Shares of Series Preferred purchasable hereunder are set forth in the
Company's Certificate of Incorporation, as amended through the Date of Grant, a
true and complete copy of which is attached hereto as Exhibit B (the "Charter").
Such antidilution rights shall not be restated, amended, modified or waived in
any manner that is adverse to the holder hereof without such holder's prior
written consent. The Company shall promptly provide the holder hereof with any
restatement, amendment, modification or waiver of the Charter promptly after the
same has been made.

         5. Notice of Adjustments. Whenever the Warrant Price or the number of
Shares purchasable hereunder shall be adjusted pursuant to Section 4 hereof, the
Company shall make a certificate signed by its chief financial officer setting
forth, in reasonable detail, the event requiring the adjustment, the amount of
the adjustment, the method by which such adjustment was calculated, and the
Warrant Price and the number of Shares purchasable hereunder after giving effect
to such adjustment, and shall cause copies of such certificate to be mailed
(without regard to Section 13 hereof, by first class mail, postage prepaid) to
the holder of this Warrant. In addition, whenever the conversion price or
conversion ratio of the Series Preferred shall be adjusted, the Company shall
make a certificate signed by its chief financial officer setting forth, in
reasonable detail, the event requiring the adjustment, the amount of the
adjustment, the method by which such adjustment was calculated, and the
conversion price or ratio of the Series Preferred after giving effect to such
adjustment, and shall cause copies of such certificate to be mailed (without
regard to Section 13 hereof, by first class mail, postage prepaid) to the holder
of this Warrant. Whenever the Warrant Price or the number of Shares purchasable
hereunder shall be adjusted pursuant to the occurrence of a Qualified Financing,
the Company shall make a certificate signed by its chief financial officer
setting forth, in reasonable detail, the event requiring the adjustment, the
amount of the adjustment, the method by which such adjustment was calculated,
and the Warrant Price and the number of Shares purchasable hereunder after

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giving effect to such adjustment, and shall cause copies of such certificate to
be mailed (without regard to Section 13 hereof, by first class mail, postage
prepaid) to the holder of this Warrant.

         6. Fractional Shares. No fractional shares of Series Preferred will be
issued in connection with any exercise hereunder, but in lieu of such fractional
shares the Company shall make a cash payment therefor based on the fair market
value of the Series Preferred on the date of exercise as reasonably determined
in good faith by the Company's Board of Directors.

         7. Compliance with Act; Disposition of Warrant or Shares of Series
Preferred.

            (a) Compliance with Act. The holder of this Warrant, by acceptance
hereof, agrees that this Warrant, and the shares of Series Preferred to be
issued upon exercise hereof and any Common Stock issued upon conversion thereof
are being acquired for investment and that such holder will not offer, sell or
otherwise dispose of this Warrant, or any shares of Series Preferred to be
issued upon exercise hereof or any Common Stock issued upon conversion thereof
except under circumstances which will not result in a violation of the Act or
any applicable state securities laws. Upon exercise of this Warrant, unless the
Shares being acquired are registered under the Act and any applicable state
securities laws or an exemption from such registration is available, the holder
hereof shall confirm in writing that the shares of Series Preferred so purchased
(and any shares of Common Stock issued upon conversion thereof) are being
acquired for investment and not with a view toward distribution or resale in
violation of the Act and shall confirm such other matters related thereto as may
be reasonably requested by the Company. This Warrant and all shares of Series
Preferred issued upon exercise of this Warrant and all shares of Common Stock
issued upon conversion thereof (unless registered under the Act and any
applicable state securities laws) shall be stamped or imprinted with a legend in
substantially the following form:

"THE SECURITIES EVIDENCED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES LAWS. NO SALE OR DISPOSITION
MAY BE EFFECTED WITHOUT (i) EFFECTIVE REGISTRATION STATEMENTS RELATED THERETO,
(ii) AN OPINION OF COUNSEL OR OTHER EVIDENCE, REASONABLY SATISFACTORY TO THE
COMPANY, THAT SUCH REGISTRATIONS ARE NOT REQUIRED, (iii) RECEIPT OF NO-ACTION
LETTERS FROM THE APPROPRIATE GOVERNMENTAL AUTHORITIES, OR (iv) OTHERWISE
COMPLYING WITH THE PROVISIONS OF SECTION 7 OF THE WARRANT UNDER WHICH THESE
SECURITIES WERE ISSUED, DIRECTLY OR INDIRECTLY."

         Said legend shall be removed by the Company, upon the request of a
holder, at such time as the restrictions on the transfer of the applicable
security shall have terminated. In addition, in connection with the issuance of
this Warrant, the holder specifically represents to the Company by acceptance of
this Warrant as follows:

               (1) The holder is aware of the Company's business affairs and
financial condition, and has acquired information about the Company sufficient
to reach an informed and knowledgeable decision to acquire this Warrant. The
holder is acquiring this Warrant for its own account for investment purposes
only and not with a view to, or for the resale in connection with, any
"distribution" thereof in violation of the Act.

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               (2) The holder understands that this Warrant has not been
registered under the Act in reliance upon a specific exemption therefrom, which
exemption depends upon, among other things, the bona fide nature of the holder's
investment intent as expressed herein.

               (3) The holder further understands that this Warrant must be held
indefinitely unless subsequently registered under the Act and qualified under
any applicable state securities laws, or unless exemptions from registration and
qualification are otherwise available. The holder is aware of the provisions of
Rule 144, promulgated under the Act.

               (4) The holder is an "accredited investor" as such term is
defined in Rule 501 of Regulation D promulgated under the Act.

            (b) Disposition of Warrant or Shares. With respect to any offer,
sale or other disposition of this Warrant or any shares of Series Preferred
acquired pursuant to the exercise of this Warrant prior to registration of such
Warrant or shares, the holder hereof agrees to give written notice to the
Company prior thereto, describing briefly the manner thereof, together with a
written opinion of such holder's counsel, or other evidence, if reasonably
satisfactory to the Company, to the effect that such offer, sale or other
disposition may be effected without registration or qualification (under the Act
as then in effect or any federal or state securities law then in effect) of this
Warrant or such shares of Series Preferred or Common Stock and indicating
whether or not under the Act certificates for this Warrant or such shares of
Series Preferred to be sold or otherwise disposed of require any restrictive
legend as to applicable restrictions on transferability in order to ensure
compliance with such law. Upon receiving such written notice and reasonably
satisfactory opinion or other evidence, the Company, as promptly as practicable
but no later than fifteen (15) days after receipt of the written notice, shall
notify such holder that such holder may sell or otherwise dispose of this
Warrant or such shares of Series Preferred or Common Stock, all in accordance
with the terms of the notice delivered to the Company. If a determination has
been made pursuant to this Section 7(b) that the opinion of counsel for the
holder or other evidence is not reasonably satisfactory to the Company, the
Company shall so notify the holder promptly with details thereof after such
determination has been made. Notwithstanding the foregoing, this Warrant or such
shares of Series Preferred or Common Stock may, as to such federal laws, be
offered, sold or otherwise disposed of in accordance with Rule 144 or 144A under
the Act, provided that the Company shall have been furnished with such
information as the Company may reasonably request to provide a reasonable
assurance that the provisions of Rule 144 or 144A have been satisfied. Each
certificate representing this Warrant or the shares of Series Preferred thus
transferred (except a transfer pursuant to Rule 144 or 144A) shall bear a legend
as to the applicable restrictions on transferability in order to ensure
compliance with such laws, unless in the aforesaid opinion of counsel for the
holder, such legend is not required in order to ensure compliance with such
laws. The Company may issue stop transfer instructions to its transfer agent in
connection with such restrictions.

            (c) Market Stand-Off Agreement. The holder shall be subject to the
"Market Stand-Off Agreement" set forth in Section 2.12 of the Third Amended and
Restated Investor's Rights Agreement dated as of August 21, 2001 by and among
the Company and certain of its investors (as the same may be amended or restated
from time to time, the "Investors' Rights Agreement"), as if holder were a party
thereto.

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            (d) Applicability of Restrictions. Neither any restrictions of any
legend described in this Warrant nor the requirements of Section 7(b) or 7(c)
above shall apply to any transfer of, or grant of a security interest in, this
Warrant (or the Series Preferred or Common Stock obtainable upon exercise
thereof) or any part hereof (i) to a partner of the holder if the holder is a
partnership or to a member of the holder if the holder is a limited liability
company, or (ii) to Silicon Valley Bancshares (holder's parent company) or any
affiliate of the holder if the holder is a corporation or bank; provided,
however, in any such transfer, (x) the transferee shall on the Company's request
agree in writing to be bound by the terms of this Warrant as if an original
holder hereof, and (z) other than the transfer to Silicon Valley Bancshares the
transferor shall give the Company prior written notice thereof in reasonable
detail, including the name of the transferee and the extent of the rights and/or
number of shares to be transferred. Subject to the provisions of this Section
7(d), upon receipt by holder of the executed Warrant, holder will transfer all
or part of this Warrant or the Shares issuable upon exercise of this Warrant (or
the securities issuable, directly or indirectly, upon conversion of the Shares,
if any) to Silicon Valley Bancshares, holder's parent company. Subject to the
provisions of this Section 7(c) and upon providing Company with written notice,
holder or Silicon Valley Bancshares may transfer all or part of this Warrant or
the Shares issuable upon exercise of this Warrant (or the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) to The Silicon
Valley Bank Foundation.

         8. Rights as Shareholders; Information. No holder of this Warrant, as
such, shall be entitled to vote or receive dividends or be deemed the holder of
Series Preferred or any other securities of the Company which may at any time be
issuable upon the exercise hereof for any purpose, nor shall anything contained
herein be construed to confer upon the holder of this Warrant, as such, any of
the rights of a shareholder of the Company or any right to vote for the election
of directors or upon any matter submitted to shareholders at any meeting
thereof, or to receive notice of meetings, or to receive dividends or
subscription rights or otherwise until this Warrant shall have been exercised
and the Shares purchasable upon the exercise hereof shall have become
deliverable, as provided herein. Notwithstanding the foregoing, the Company will
transmit to the holder of this Warrant such information, documents and reports
as are generally distributed to all of the holders of any class or series of the
securities of the Company concurrently with the distribution thereof to such
shareholders.

         9. Registration Rights. The Company shall take such action as may
reasonably necessary to amend the Investors' Rights Agreement to include the
Shares as Registerable Securities, as such term is defined therein, solely for
the purposes of Sections 2.3 and 2.5 through 2.12 of the Investors' Rights
Agreement and the holder hereof shall execute and deliver such counterpart
signature pages to the Investors' Rights Agreement and take such other action as
may be reasonably necessary to become a party to the investors' Rights Agreement
or to have the Shares included as Registerable Securities thereunder.

         10. Additional Rights.

         10.1 Acquisition Transactions. The Company shall provide the holder of
this Warrant with at least twenty (20) days' written notice prior to closing
thereof of the terms and conditions of any of the following transactions (to the
extent the Company has notice thereof): (i) the sale, lease, exchange,
conveyance or other disposition of all or substantially all of the Company's

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property or business, or (ii) any consolidation or the merger of the Company
with or into any other corporation or other entity or person, or any other
corporate reorganization, in which the stockholders of the Company immediately
prior to such consolidation, merger or reorganization, own less than fifty
percent (50%) of the Company's voting power immediately after such
consolidation, merger or reorganization, or any transaction or series of related
transactions in which in excess of fifty percent (50%) of the Company's voting
power is transferred. Any transaction described in (i) or (ii) above in which
the sole consideration paid in respect of the Company's property, business and
stock is cash or publicly traded securities shall be deemed a "Sale of the
Company" for purposes of this Warrant. If, following receipt of such notice from
the Company, the holder of this Warrant shall notify the Company not less than
five (5) days prior to the closing of such Sale of the Company of such holder's
intent to exercise the purchase right represented by this Warrant as provided in
Section 2 above (including, without limitation, by way of net issuance as
provided in Section 10.2 below), such exercise will be deemed effective upon
completion of such Sale of the Company or, alternatively, rescinded in the event
such Sale of the Company is not completed. If, following receipt of timely
notice from the Company, the holder of this Warrant has not notified the Company
of its election not less than five (5) days prior to the closing of such Sale of
the Company, then: (X) if the fair market value of one share of the Series
Preferred is greater than the Warrant Price then in effect, this Warrant shall
be deemed automatically exercised pursuant to Section 10.2 and Section 10.3
below upon completion of such Sale of the Company; and (Y) if the fair market
value of one share of the Series Preferred is equal to or less than the Warrant
Price then in effect, this Warrant will expire upon completion of such Sale of
the Company.

         10.2 Right to Convert Warrant into Stock: Net Issuance.

            (a) Right to Convert. In addition to and without limiting the rights
of the holder under the terms of this Warrant, if the fair market price of one
share of Series preferred is greater tan the Warrant Price then in effect, the
holder shall have the right to convert this Warrant or any portion thereof (the
"Conversion Right") into shares of Series Preferred as provided in this Section
10.2 at any time or from time to time during the term of this Warrant. Upon
exercise of the Conversion Right with respect to a particular number of shares
subject to this Warrant (the "Converted Warrant Shares"), the Company shall
deliver to the holder (without payment by the holder of any exercise price or
any cash or other consideration) that number of shares of fully paid and
nonassessable Series Preferred as is determined according to the following
formula:

         X=   B - A
            --------
                Y

         Where: X =  the number of shares of Series Preferred that shall be
                     issued to holder

                Y =  the fair market value of one share of Series Preferred

                A =  the aggregate Warrant Price of the specified number
                     of Converted Warrant Shares immediately prior to the
                     exercise of the Conversion Right (i.e., the number of
                     Converted Warrant Shares multiplied by the Warrant
                     Price)

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                B =  the aggregate fair market value of the specified
                     number of Converted Warrant Shares (i.e., the number
                     of Converted Warrant Shares multiplied by the fair
                     market value of one Converted Warrant Share)

         No fractional shares shall be issuable upon exercise of the Conversion
Right, and, if the number of shares to be issued determined in accordance with
the foregoing formula is other than a whole number, the Company shall pay to the
holder an amount in cash equal to the fair market value of the resulting
fractional share on the Conversion Date (as hereinafter defined). For purposes
of Section 10 of this Warrant, shares issued pursuant to the Conversion Right
shall be treated as if they were issued upon the exercise of this Warrant.

            (b) Method of Exercise. The Conversion Right may be exercised by the
holder by the surrender of this Warrant at the principal office of the Company
together with a written statement (which may be in the form of Exhibit A-1 or
Exhibit A-2 hereto) specifying that the holder thereby intends to exercise the
Conversion Right and indicating the number of shares subject to this Warrant
which are being surrendered (referred to in Section 10.2(a) hereof as the
Converted Warrant Shares) in exercise of the Conversion Right. Such conversion
shall be effective upon receipt by the Company of this Warrant together with the
aforesaid written statement, or on such later date as is specified therein (the
"Conversion Date"), and, at the election of the holder hereof, may be made
contingent upon the closing of the sale of the Company's Common Stock to the
public in a public offering pursuant to a Registration Statement under the Act
(a "Public Offering"). Certificates for the shares issuable upon exercise of the
Conversion Right and, if applicable, a new warrant evidencing the balance of the
shares remaining subject to this Warrant, shall be issued as of the Conversion
Date and shall be delivered to the holder within thirty (30) days following the
Conversion Date.

            (c) Determination of Fair Market Value. For purposes of this Section
10.2, "fair market value" of a share of Series Preferred (or Common Stock if the
Series Preferred has been automatically converted into Common Stock) as of a
particular date (the "Determination Date") shall mean:

               (i) If the Conversion Right is exercised in connection with and
contingent upon a Public Offering, and if the Company's Registration Statement
relating to such Public Offering ("Registration Statement") has been declared
effective by the Securities and Exchange Commission, then the initial "Price to
Public" specified in the final prospectus with respect to such offering.

               (ii) If the Conversion Right is not exercised in connection with
and contingent upon a Public Offering, then as follows:

            (A) If traded on a securities exchange, the fair market value of the
Common Stock shall be deemed to be the average of the closing prices of the
Common Stock on such exchange over the five trading days immediately prior to
the Determination Date, and the fair market value of the Series Preferred shall
be deemed to be such fair market value of the Common Stock multiplied by the
number of shares of Common Stock into which each share of Series Preferred is
then convertible;

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<PAGE>
            (B) If traded on the Nasdaq Stock Market or other over-the-counter
system, the fair market value of the Common Stock shall be deemed to be the
average of the closing bid prices of the Common Stock over the five trading days
immediately prior to the Determination Date, and the fair market value of the
Series Preferred shall be deemed to be such fair market value of the Common
Stock multiplied by the number of shares of Common Stock into which each share
of Series Preferred is then convertible; and

            (C) If there is no public market for the Common Stock, then fair
market value shall be determined by the Company's board of directors acting in
good faith.

In making a determination under clauses (A) or (B) above, if on the
Determination Date, five trading days had not passed since the IPO, then the
fair market value of the Common Stock shall be the average closing prices or
closing bid prices, as applicable, for the shorter period beginning on and
including the date of the IPO and ending on the trading day prior to the
Determination Date (or if such period includes only one trading day the closing
price or closing bid price, as applicable, for such trading day). If closing
prices or closing bid prices are no longer reported by a securities exchange or
other trading system, the closing price or closing bid price shall be that which
is reported by such securities exchange or other trading system at 4:00 p.m. New
York City time on the applicable trading day.

         10.3 Exercise Prior to Expiration. To the extent this Warrant is not
previously exercised as to all of the Shares subject hereto, and if the fair
market value of one share of the Series Preferred is greater than the Warrant
Price then in effect, this Warrant shall be deemed automatically exercised
pursuant to Section 10.2 above (even if not surrendered) immediately before its
expiration. For purposes of such automatic exercise, the fair market value of
one share of the Series Preferred upon such expiration shall be determined
pursuant to Section 10.2(c). To the extent this Warrant or any portion thereof
is deemed automatically exercised pursuant to this Section 10.3, the Company
agrees to promptly notify the holder hereof of the number of Shares, if any, the
holder hereof is to receive by reason of such automatic exercise.

         11. Representations and Warranties. The Company represents and warrants
to the holder of this Warrant, as of the Date of Grant, as follows:

            (a) This Warrant has been duly authorized and executed by the
Company and is a valid and binding obligation of the Company enforceable in
accordance with its terms, subject to laws of general application relating to
bankruptcy, insolvency and the relief of debtors and the rules of law or
principles at equity governing specific performance, injunctive relief and other
equitable remedies.

            (b) The shares of Series D Preferred Stock have been duly authorized
and reserved for issuance by the Company and, when issued in accordance with the
terms hereof, will be validly issued, fully paid and nonassessable and free from
preemptive rights. If this Warrant becomes exercisable for shares of Next Round
Preferred Stock, the Company shall duly authorize and reserve for issuance
sufficient shares of the Next Round Preferred Stock, and such shares, when
issued in accordance with the terms hereof, will be validly issued, fully paid
and nonassessable and free from preemptive rights.

                                      -10-
<PAGE>
            (c) The rights, preferences, privileges and restrictions granted to
or imposed upon the Company's Series D Preferred Stock and the holders thereof
are as set forth in the Charter, and on the Date of Grant, each share of the
Company's Series D Preferred Stock represented by this Warrant is convertible
into one share of Common Stock. The rights, preferences, privileges and
restrictions granted to or imposed on the Company's Next Round Preferred Stock
shall be set forth in an amendment to the Charter.

            (d) The shares of Common Stock issuable upon conversion of the
Series D Preferred Stock have been duly authorized and reserved for issuance by
the Company and, when issued in accordance with the terms of the Charter will be
validly issued, fully paid and nonassessable. If this Warrant becomes
exercisable for shares of Next Round Preferred Stock, the shares of Common Stock
issuable upon conversion of such shares of Next Round Preferred Stock will be
duly authorized and reserved for issuance by the Company and, when issued in
accordance with the terms of the Charter, as amended, will be validly issued,
fully paid and nonassessable.

            (e) The execution and delivery of this Warrant are not, and the
issuance of the Shares upon exercise of this Warrant in accordance with the
terms hereof will not be, inconsistent with the Company's Charter or by-laws, do
not and will not contravene in any material respects any law, governmental rule
or regulation, judgment or order applicable to the Company, and do not and will
not conflict with or contravene any provision of, or constitute a default under,
any indenture, mortgage, contract or other instrument of which the Company is a
party or by which it is bound or require the consent or approval of, the giving
of notice to, the registration or filing with or the taking of any action in
respect of or by, any Federal, state or local government authority or agency or
other person, except for the filing of notices pursuant to federal and state
securities laws, which filings will be effected by the time required thereby.

            (f) There are no actions, suits, audits, investigations or
proceedings pending or, to the knowledge of the Company, threatened against the
Company in any court or before any governmental commission, board or authority
which, if adversely determined, could have a material adverse effect on the
ability of the Company to perform its obligations under this Warrant.

            (g) The number of shares of Common Stock of the Company outstanding
on the date hereof, on a fully diluted basis (assuming the conversion of all
outstanding convertible securities and the exercise of all outstanding options
and warrants), does not exceed 90,000,000 shares.

         12. Modification and Waiver. This Warrant and any provision hereof may
be changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought.

         13. Notices. Any notice, request, communication or other document
required or permitted to be given or delivered to the holder hereof or the
Company shall be delivered, or shall be sent by certified or registered mail,
postage prepaid, to each such holder at its address as shown on the books of the
Company or to the Company at the address indicated therefor on the signature
page of this Warrant.

                                      -11-
<PAGE>
         14. Binding Effect on Successors. This Warrant shall be binding upon
any corporation succeeding the Company by merger, consolidation or acquisition
of all or substantially all of the Company's assets, and all of the obligations
of the Company relating to the Series Preferred issuable upon the exercise or
conversion of this Warrant shall survive the exercise, conversion and
termination of this Warrant and all of the covenants and agreements of the
Company shall inure to the benefit of the successors and assigns of the holder
hereof.

         15. Lost Warrants or Stock Certificates. The Company covenants to the
holder hereof that, upon receipt of evidence reasonably satisfactory to the
Company of the loss, theft, destruction or mutilation of this Warrant or any
stock certificate and, in the case of any such loss, theft or destruction, upon
receipt of an indemnity reasonably satisfactory to the Company, or in the case
of any such mutilation upon surrender and cancellation of such Warrant or stock
certificate, the Company will make and deliver a new Warrant or stock
certificate, of like tenor, in lieu of the lost, stolen, destroyed or mutilated
Warrant or stock certificate.

         16. Descriptive Headings. The descriptive headings of the various
Sections of this Warrant are inserted for convenience only and do not constitute
a part of this Warrant. The language in this Warrant shall be construed as to
its fair meaning without regard to which party drafted this Warrant.

         17. Governing Law. This Warrant shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the State of Delaware.

         18. Survival of Representations, Warranties and Agreements. All
representations and warranties of the Company and the holder hereof contained
herein shall survive the Date of Grant, the exercise or conversion of this
Warrant (or any part hereof) or the termination or expiration of rights
hereunder. All agreements of the Company and the holder hereof contained herein
shall survive indefinitely until, by their respective terms, they are no longer
operative.

         19. Remedies. In case any one or more of the covenants and agreements
contained in this Warrant shall have been breached, the holders hereof (in the
case of a breach by the Company), or the Company (in the case of a breach by a
holder), may proceed to protect and enforce their or its rights either by suit
in equity and/or by action at law, including, but not limited to, an action for
damages as a result of any such breach and/or an action for specific performance
of any such covenant or agreement contained in this Warrant.

         20. No Impairment of Rights. The Company will not, by amendment of its
Charter or through any other means, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
action as may be necessary or appropriate in order to protect the rights of the
holder of this Warrant against impairment.

         21. Severability. The invalidity or unenforceability of any provision
of this Warrant in any jurisdiction shall not affect the validity or
enforceability of such provision in any other jurisdiction, or affect any other
provision of this Warrant, which shall remain in full force and effect.

                                      -12-
<PAGE>
         22. Recovery of Litigation Costs. If any legal action or other
proceeding is brought for the enforcement of this Warrant, or because of an
alleged dispute, breach, default, or misrepresentation in connection with any of
the provisions of this Warrant, the successful or prevailing party or parties
shall be entitled to recover reasonable attorneys' fees and other costs incurred
in that action or proceeding, in addition to any other relief to which it or
they may be entitled.

         23. Entire Agreement; Modification. This Warrant constitutes the entire
agreement between the parties pertaining to the subject matter contained in it
and supersedes all prior and contemporaneous agreements, representations, and
undertakings of the parties, whether oral or written, with respect to such
subject matter.

         24. Acceptance. Receipt of this Warrant by the holder hereof shall
constitute acceptance of and agreement to all of the terms and conditions
contained herein.

                                      -13-
<PAGE>
         The Company has caused this Warrant to be duly executed and delivered
as of the Date of Grant specified above.

                                MYOGEN, INC.

                                By:      /s/ Joseph L. Turner
                                   -----------------------------------------
                                Name:    Joseph L. Turner
                                     ---------------------------------------
                                Title:   Vice President, Finance and
                                      -------------------------------------
                                         Administration and Chief Financial
                                         Officer
                                Address:  7577 West 103rd Avenue, Suite 102,
                                Boulder, Colorado 80021

                                      -14-
<PAGE>
                                   EXHIBIT A-1

                               NOTICE OF EXERCISE

To:      MYOGEN, INC.  (the "Company")

         1. The undersigned hereby:

                  [ ]      elects to purchase ________ shares of [Series
                           Preferred Stock] [Common Stock] of the Company
                           pursuant to the terms of the attached Warrant, and
                           tenders herewith payment of the purchase price of
                           such shares in full, or

                  [ ]      elects to exercise its net issuance rights pursuant
                           to Section 10.2 of the attached Warrant with respect
                           to ________ Shares of [Series Preferred Stock]
                           [Common Stock].

         2. Please issue a certificate or certificates representing ________
shares in the name of the undersigned or in such other name or names as are
specified below:

                    ----------------------------------------
                                     (Name)

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

                    ----------------------------------------
                                    (Address)

         3. The undersigned represents that the aforesaid shares are being
acquired for the account of the undersigned for investment and not with a view
to, or for resale in connection with, the distribution thereof and that the
undersigned has no present intention of distributing or reselling such shares,
all except as in compliance with applicable securities laws.

                                               ---------------------------------
                                               (Signature)

---------------------------
          (Date)
<PAGE>
                                   EXHIBIT A-2

                               NOTICE OF EXERCISE

To:      MYOGEN, INC. (the "Company")

         1. Contingent upon and effective immediately prior to the closing (the
"Closing") of the Company's public offering contemplated by the Registration
Statement on Form S__ filed _______________, 200__, the undersigned hereby:

         [ ] elects to purchase ________ shares of [Series Preferred Stock]
[Common Stock] of the Company (or such lesser number of shares as may be sold on
behalf of the undersigned at the Closing) pursuant to the terms of the attached
Warrant, or

         [ ] elects to exercise its net issuance rights pursuant to Section 10.2
of the attached Warrant with respect to ________ Shares of [Series Preferred
Stock] [Common Stock].

         2. Please deliver to the custodian for the selling shareholders a stock
certificate representing such ________ shares.

         3. The undersigned has instructed the custodian for the selling
shareholders to deliver to the Company $________ or, if less, the net proceeds
due the undersigned from the sale of shares in the aforesaid public offering. If
such net proceeds are less than the purchase price for such shares, the
undersigned agrees to deliver the difference to the Company prior to the
Closing.

                                               ---------------------------------
                                               (Signature)

---------------------------
          (Date)
<PAGE>
                                    EXHIBIT B

                                     CHARTER

                             [INTENTIONALLY OMITTED]<PAGE>
                                                                   EXHIBIT 10.17

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

                                LICENSE AGREEMENT

                                   (ENOXIMONE)

                                 BY AND BETWEEN

                          HOECHST MARION ROUSSEL, INC.

                                       AND

                                  MYOGEN, INC.

                         EFFECTIVE AS OF OCTOBER 1, 1998

<PAGE>

                                TABLE OF CONTENTS

<Table>
<Caption>
                                                                                                                PAGE

<S>                                                                                                           <C>
ARTICLE 1             DEFINITIONS.................................................................................1
         1.1      "Affiliate".....................................................................................1
         1.2      "Control".......................................................................................1
         1.3      "Development"...................................................................................1
         1.4      "Development Expenses"..........................................................................2
         1.5      "Development Plans".............................................................................2
         1.6      "Drug Approval Application".....................................................................2
         1.7      "Enoximone".....................................................................................2
         1.8      "Europe"........................................................................................2
         1.9      "Equity payments"...............................................................................2
         1.10     "FDA"...........................................................................................2
         1.11     "Field".........................................................................................2
         1.12     "HMR Data"......................................................................................2
         1.13     "HMR Know-how"..................................................................................2
         1.14     "HMR Patent"....................................................................................2
         1.15     "HMR Trademark".................................................................................3
         1.16     "IND"...........................................................................................3
         1.17     "Information"...................................................................................3
         1.18     "Joint Patent"..................................................................................3
         1.19     "Major Market Country"..........................................................................3
         1.20     "Material Breach"...............................................................................3
         1.21     "Milestone Payments"............................................................................3
         1.22     "Myogen Data"...................................................................................3
         1.23     "Myogen Know-how"...............................................................................3
         1.24     "Myogen Patent".................................................................................3
         1.25     "NDA" or "New Drug Applications"................................................................4
         1.26     "Net Sales".....................................................................................4
         1.27     "Patent"........................................................................................4
         1.28     "Patent Expenses"...............................................................................4
         1.29     "Product".......................................................................................4
         1.30     "Q & A".........................................................................................5
         1.31     "Regulatory Approval"...........................................................................5
         1.32     "Regulatory Filings"............................................................................5
         1.33     "Signing Fees"..................................................................................5
         1.34     "Sublicensee"...................................................................................5
         1.35     "Sublicense Fees"...............................................................................5
         1.36     "Terminated Countries"..........................................................................5
         1.37     "Termination Effective Date"....................................................................5
         1.38     "Territory".....................................................................................5
         1.39     "Third Party"...................................................................................5
         1.40     "Transfer Date".................................................................................5
         [*#*]
</Table>

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

                                TABLE OF CONTENTS
                                   (CONTINUED)

<Table>
<Caption>
                                                                                                                 PAGE

<S>                                                                                                              <C>
         1.42     "Written Disclosure"............................................................................5
ARTICLE 2             LICENSE GRANTS..............................................................................5
         2.1      Patent and Know-how License to Myogen to Conduct Development....................................5
         2.2      Patent and Know-how License to Myogen for Commercialization.....................................5
         2.3      Sublicenses.....................................................................................6
ARTICLE 3             DEVELOPMENT.................................................................................6
         3.1      Scope...........................................................................................6
         3.2      Conduct of Development..........................................................................6
         [*#*]
         3.4      Development Plans...............................................................................7
         3.5      Status Meetings.................................................................................7
         3.6      Obligations of the Parties......................................................................7
         3.7      Existing Inventory..............................................................................8
         3.8      Regulatory Matters..............................................................................9
ARTICLE 4             MILESTONES AND ROYALTIES....................................................................9
         4.1      Europe.........................................................................................10
         4.2      Territory other than Europe....................................................................10
         4.3      Duration of Royalty Obligations................................................................10
         4.4      Royalty Rate if Generics Introduced............................................................11
         4.5      Sales by Sublicensees..........................................................................11
         4.6      Royalty Payments and Reports...................................................................11
         4.7      Taxes..........................................................................................11
         4.8      Blocked Currency...............................................................................12
         4.9      Payments to or Reports by Affiliates...........................................................12
         4.10     No Multiple Royalties..........................................................................12
ARTICLE 5             CONFIDENTIALITY............................................................................12
         5.1      Confidentiality; Exceptions....................................................................12
         5.2      Authorized Disclosure..........................................................................12
         5.3      Survival.......................................................................................13
         5.4      Termination of Prior Agreement.................................................................13
         5.5      Publications...................................................................................13
ARTICLE 6             OWNERSHIP OF INTELLECTUAL PROPERTY AND PATENT RIGHTS.......................................13
         6.1      Ownership......................................................................................13
         6.2      Disclosure of Patentable Inventions............................................................14
         6.3      Patent Filings.................................................................................14
         6.4      Third Party Patent Rights......................................................................15
         6.5      Enforcement Rights.............................................................................15
         6.6      Assignment of Joint Patents....................................................................16
ARTICLE 7             REPRESENTATIONS AND WARRANTIES; EXCLUSIVITY................................................17
         7.1      Representations and Warranties.................................................................17
         7.2      Exclusivity; Non-competition Within The Field..................................................17
ARTICLE 8             INFORMATION & REPORTS......................................................................17
</Table>

                                      -ii-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

                                TABLE OF CONTENTS
                                   (CONTINUED)

<Table>
<Caption>
                                                                                                                 PAGE

<S>                                                                                                              <C>
         8.1      Records of Revenues and Expenses...............................................................17
         8.2      Publicity Review...............................................................................18
ARTICLE 9             TERM AND TERMINATION.......................................................................18
         9.1      Term...........................................................................................18
         9.2      Termination by HMR For Myogen's Failure to Meet Milestones or Discontinuing
                  Development....................................................................................18
         9.3      Termination by HMR For Myogen's Failure to Commercialize or Market Products in
                  the Territory..................................................................................19
         9.4      Termination for Material Breach by Myogen......................................................21
         9.5      Termination Without Cause......................................................................22
         9.6      Termination for Material Breach by HMR.........................................................23
ARTICLE 10            INDEMNIFICATION............................................................................24
         10.1     Indemnification by HMR.........................................................................24
         10.2     Indemnification by Myogen......................................................................24
ARTICLE 11            DISPUTE RESOLUTION.........................................................................25
         11.1     General........................................................................................25
         11.2     Negotiation....................................................................................25
         11.3     Arbitration....................................................................................25
         11.4     Survivability..................................................................................26
         11.5     Jurisdiction...................................................................................26
ARTICLE 12            MISCELLANEOUS..............................................................................26
         12.1     Assignment; Binding Effect.....................................................................26
         12.2     Research and Development Entities..............................................................27
         12.3     Consents Not Unreasonably Withheld.............................................................27
         12.4     Force Majeure..................................................................................27
         12.5     Further Actions................................................................................27
         12.6     No Trademark Rights............................................................................27
         12.7     Notices........................................................................................27
         12.8     Waiver.........................................................................................28
         12.9     Severability...................................................................................28
         12.10    Ambiguities....................................................................................28
         12.11    Governing Law..................................................................................28
         12.12    Headings.......................................................................................28
         12.13    Counterparts...................................................................................28
         12.14    Entire Agreement...............................................................................28
         12.15    Additional Agreements..........................................................................29
</Table>

                                     -iii-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

                                LICENSE AGREEMENT

         LICENSE AGREEMENT (the "Agreement") effective as of October 1, 1998
(the "Effective Date"), by and between MYOGEN, INC., a Delaware corporation
("Myogen") and HOECHST MARION ROUSSEL, INC., a Delaware corporation ("HMR").
Myogen and HMR are sometimes referred to herein individually as a "Party" and
together as the "Parties."

                              W I T N E S S E T H:

         WHEREAS, HMR is a leading multinational health care company with a
broad product portfolio of drugs for the treatment of human diseases;

         WHEREAS, Myogen is a biotechnology company that has expertise and
experience in the research and development of compounds for use in treating
cardiovascular disease;

         WHEREAS, Myogen desires to obtain an exclusive worldwide license from
HMR for the right to develop and commercialize Enoximone (as defined in Article
1.8) on the terms and subject to the conditions set forth in this Agreement.

         NOW, THEREFORE, in consideration of the foregoing premises and the
mutual covenants and agreements contained herein, the parties agree as follows:

                                   ARTICLE 1

                                   DEFINITIONS

         For purposes of this Agreement, the terms defined in this Article I
shall have the meanings specified below:

         1.1 "AFFILIATE" shall mean any corporation, firm, partnership or other
entity, whether de jure or de facto, which directly or indirectly owns, is owned
or is under common ownership with a party to this Agreement to the extent of
more than fifty percent (50%) of the equity (or such lesser percentage which is
the maximum allowed to be owned by a foreign corporation in a particular
jurisdiction) having the power to direct the affairs of the entity and any
person, firm, partnership, corporation or other entity actually controlled by,
controlling or under common control with a party to this Agreement. This term
does not include those individuals or entities who have made an equity
investment in a party but who have no significant operational management with
respect to the party.

         1.2 "CONTROL" means possession of the ability to grant a license or
sublicense as provided for herein without violating the terms of any agreement
or other arrangement with or proprietary rights of any Third Party.

         1.3 "DEVELOPMENT" shall mean all activities relating to obtaining
Regulatory Approval of a Product, Product line extensions, alternative delivery
systems and new indications therefor and all activities relating to developing
the ability to manufacture the same. This includes pre-clinical testing,
toxicology, formulation, bulk product, fill/finish, manufacturing

                                      -1-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

process development, manufacturing and quality assurance technical support,
clinical studies, regulatory affairs and outside counsel regulatory legal
services.

         1.4 [*#*]

         1.5 "DEVELOPMENT PLANS" shall mean the Development Plans referred to in
Article 3.4.

         1.6 "DRUG APPROVAL APPLICATION" means an application for Regulatory
Approval required before commercial sale or use of a Product as a drug in a
country in the Territory.

         1.7 "ENOXIMONE" shall mean
1,3-dihydro-4-methyl-5-[*#*]-2H-imidazol-2-one, and all
pharmaceutically-acceptable forms (e.g., salts) and all formulations thereof,
including, without limitation, that formulation developed by HMR and marketed
under the trade name of Perfan in Europe.

         1.8 "Europe" shall mean the following countries Austria, Belgium,
Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the
Netherlands, Portugal, Spain Sweden, and the United Kingdom.

         1.9 "EQUITY PAYMENTS" shall have the meaning set forth in Article
2.3.2.

         1.10 "FDA" means the United States Food and Drug Administration or any
other equivalent regulatory authority in the Territory.

         1.11 "FIELD" means the prevention, treatment and/or diagnosis of
cardiovascular diseases and disorders.

         1.12 "HMR DATA" means all Information related to the Product HMR or any
of its Affiliates has in its possession arising out of all pre-clinical and
clinical research and development conducted by or on behalf of HMR or its
Affiliates or disclosed to HMR or its Affiliates by licensors and other
collaborators to the extent not subject to a restrictive confidentiality
arrangement with a Third Party.

         1.13 "HMR KNOW-HOW" means Information which (i) HMR discloses, or is
required to disclose, to Myogen under this Agreement and (ii) is within the
Control of HMR and its Affiliates. Notwithstanding anything herein to the
contrary, HMR Know-how shall exclude any HMR Patent.

         1.14 "HMR PATENT" means any and all Patents which cover the discovery,
evaluation, manufacture, use or importation, offer for sale and/or sale of
Enoximone in the Field or Product, which Patent is owned or Controlled by HMR or
any of its Affiliates as listed in Schedule 1.14, including HMR's or any of its
Affiliates' interest in any Joint Patent. HMR will promptly notify Myogen of any
HMR Patents that are issued or applied for hereafter.

         1.15 "HMR TRADEMARK" means the trademark Perfan in Europe and any other
trademarks or tradenames used by HMR to market Enoximone in any country in the
Territory.

         1.16 "IND" shall mean an Investigational New Drug Application.

                                      -2-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

         1.17 "INFORMATION" means techniques and data including inventions,
practices, methods, assays, knowledge, know-how, skill, experience, marketing,
pricing, distribution, cost, sales and manufacturing information and test data
including pharmacological, pharmacokinetic, toxicological and clinical data,
analytical and quality control data, stability and integrity data, formulation
data, quality control data, and safety and efficacy data.

         1.18 "JOINT PATENT" shall have the meaning set forth in Article 6.3.1.

         1.19 "MAJOR MARKET COUNTRY" means [*#*]

         1.20 "MATERIAL BREACH" shall have the meaning set forth in Article 9.4
(d).

         1.21 "MILESTONE PAYMENTS" shall have the meaning set forth in Article
2.3.2.

         1.22 "MYOGEN DATA" means all Information arising out of all Development
(as defined in Article III) conducted by or on behalf of Myogen or its
sublicensees, or disclosed to Myogen by its licensors and other collaborators
necessary to obtain Regulatory Approval for marketing of Products in the
Territory.

         1.23 "MYOGEN KNOW-HOW" means Information which (i) Myogen discloses, or
is required to disclose, to HMR under this Agreement and (ii) is within the
Control of Myogen, including, without limitation, all Information developed by
or on behalf of Myogen relating to the Product. [*#*] HMR also acknowledges
that Myogen's performance under this Agreement cannot violate any of the terms
of those agreements between Myogen [*#*] which have been provided to HMR set
out as Schedule 1.23. Notwithstanding anything herein to the contrary, Myogen
Know-how shall exclude any Myogen Patents.

         1.24 "MYOGEN PATENT" means any and all Patents for inventions made
solely by Myogen personnel on behalf of Myogen or its Affiliates which covers
the evaluation, manufacture, use, importation, offer for sale and/or sale of
Enoximone for development by Myogen within the Field or Product, which Patent is
owned or Controlled by Myogen or its Affiliates, including Myogen's interest in
any Joint Patent. [*#*] HMR also acknowledges that Myogen's performance under
this Agreement cannot violate any of the terms of those agreements between
Myogen [*#*] which have been provided to HMR set out as Schedule 1.23. Myogen
shall-promptly notify HMR of any Myogen Patents which are issued or applied for
hereafter.

         1.25 "NDA" OR "NEW DRUG APPLICATIONS" shall mean any and all
applications submitted to the FDA under Sections 505, 507, or 512 of the Federal
Food, Drug and Cosmetic Act and any applicable regulations related to any
Products, including without limitation, full NDAs, "paper" NDAs and abbreviated
NDAs (ANDAs) and all amendments and supplements or equivalents in the Territory.

         1.26 "NET SALES" of Myogen and/or its sublicensee shall mean such
party's [*#*]

                                      -3-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

                  [*#*]

         No deductions shall be made for commissions paid to individuals whether
they be with independent sales agencies or regularly employed by Myogen and on
its payroll, or for cost of collections. Products shall be considered "sold"
when billed out or invoiced. In the event that the sale is made to an Affiliate,
the Net Sale will not be less than an equivalent sale to a non-Affiliate.

         1.27 "PATENT" means an (i) United States patent, continuation,
continuation-in-part, division, patent of addition, reexamination, reissue,
renewal, extension, term restoration and foreign counterpart thereof, including
a supplementary protection certificate and other administrative protection, and
(ii) application for a United States patent and foreign counterpart thereof; in
either case, which claim the manufacture, sale or use of Enoximone or a Product,
or formulations or manufacture thereof, for use in the Field. Any other compound
or use outside of the Field disclosed or claimed in such patent or patent
application is not within this definition of "Patent."

         1.28 "PATENT EXPENSES" means [*#*]

         1.29 "PRODUCT" shall mean any finished pharmaceutical composition
containing Enoximone as a pharmaceutically active ingredient (either alone or in
combination with one or more other pharmaceutically active ingredients), for use
in the Field.

         1.30 "Q & A" shall have the meaning set forth in Article 8.2.

         1.31 "REGULATORY APPROVAL" means any approval (including pricing and
reimbursement approvals), product and/or establishment license, registration or
authorization of any federal, state or local regulatory agency, department,
bureau or other governmental entity necessary for the manufacture, use, storage,
import, export, transport or sale of a Product.

         1.32 "REGULATORY FILINGS" shall have the meaning set forth in Article
3.8.2.

         1.33 "SIGNING FEES" shall have the meaning set forth in Article 2.3.2.

         1.34 "SUBLICENSEE" shall have the meaning set forth in Article 2.3.2.

         1.35 "SUBLICENSE FEES" shall have the meaning set forth in Article
2.3.2.

         1.36 "TERMINATED COUNTRIES" shall have the meaning set forth in Article
9.3.1.

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         1.37 "TERMINATION EFFECTIVE DATE" shall have the meaning set forth in
Article 9.2.

         1.38 "TERRITORY" means all countries and territories of the world
provided that any country(ies) in which this Agreement is terminated shall be
removed from the scope of this definition.

         1.39 "THIRD PARTY" means any entity other than Myogen or HMR or their
respective Affiliates.

         1.40 "TRANSFER DATE" shall have the meaning set forth in Article 4.1
(c).

         1.41 [*#*]

         1.42 "WRITTEN DISCLOSURE" shall have the meaning set forth in Article
8.2.

                                   ARTICLE 2

                                 LICENSE GRANTS

         2.1 PATENT AND KNOW-HOW LICENSE TO MYOGEN TO CONDUCT DEVELOPMENT. Upon
the terms and subject to the conditions of this Agreement, HMR grants to Myogen
an exclusive license (even as to HMR and its Affiliates) under the HMR Patents
and HMR Know-how, and Joint Patents, if any, to conduct Development in the
Territory in accordance with the terms of this Agreement with respect to
Enoximone for use in the Field; [*#*]

         2.2 PATENT AND KNOW-HOW LICENSE TO MYOGEN FOR COMMERCIALIZATION. Upon
the terms and subject to the conditions of this Agreement, including, without
limitation, the royalty payment obligations herein, HMR grants to Myogen an
exclusive (even as to HMR and its Affiliates) license under the HMR Patents and
HMR Know-how to conduct manufacturing, pre-marketing activities,
commercialization (including the right to make, have made, use, import, sell,
offer for sale and have sold) and related activities in the Territory with
respect to Enoximone and any Product in accordance with the terms of this
Agreement; [*#*]

         2.3 SUBLICENSES.

         2.3.1 APPROVAL REQUIRED. The foregoing license shall include the right
to sublicense, but only upon prior written notice to HMR.

         2.3.2 [*#*]

                                   ARTICLE 3

                                   DEVELOPMENT

         3.1 SCOPE. Myogen shall conduct a development program with respect to
Products with the objective of obtaining Regulatory Approval and commercializing
a Product as set forth in this Agreement.

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         3.2 CONDUCT OF DEVELOPMENT. Myogen will be solely responsible for
carrying out Development of Products. Throughout the term hereof, Myogen shall
have the right to engage Third Parties to perform its research, development and
commercialization activities pursuant to this Agreement, provided such Third
Party agrees to be bound by Article V hereof or the equivalent. Notwithstanding
any other provision hereof, Myogen shall have sole control and authority over
all aspects of Development and commercialization of Products in the Territory,
and HMR shall not have any liability with respect thereto.

         3.3 [*#*] Promptly after the date of execution of this Agreement,
Myogen shall assume full responsibility for all aspects of [*#*] trials under
the IND for Enoximone that was submitted to the FDA. HMR will transfer all
records and study data relating to the [*#*] trials to Myogen. Myogen and HMR
will cooperate to ensure an orderly and clear transfer of responsibility.

         3.4 DEVELOPMENT PLANS. Development of Products pursuant to this Article
III shall be governed by a separate written plan attached as Exhibit 3.4 hereto
("Development Plan") which, together with updates, shall be prepared by Myogen
and submitted to HMR for its information. Each Development Plan will describe
the proposed overall program of development for Products, including, process
development, clinical studies and regulatory plans and other elements of
obtaining Regulatory Approval. Each Development Plan will set forth key
objectives. Each Development Plan will be updated annually by Myogen and,
together with any updates thereto, be provided to HMR for its information.

         3.5 STATUS MEETINGS. Representatives from HMR and Myogen will meet at
least two (2) times annually to discuss development and commercialization of
Products for use in the Field for purposes of HMR's information and to monitor
Myogen's compliance with the provisions of this Agreement. The location of such
meetings will alternate between Myogen's facilities and HMR's facilities. Each
Party will bear its own travel and related costs. Myogen shall provide HMR all
Information reasonably requested by HMR during the term hereof relating to the
development and commercialization of Products for use in the Field and Products.

         3.6 OBLIGATIONS OF THE PARTIES.

         3.6.1 MYOGEN'S OBLIGATIONS.

                  (a) Myogen shall use reasonable commercial diligence,
consistent with accepted business practices and legal requirements relating to
pharmaceutical drug development and within the general guidelines as set forth
in the Development Plans and any updates thereto, to continue Development of
Products in the Territory, devoting the same degree of attention and diligence
to such development efforts as similar companies devote to development
activities for potential drug products of comparable market potential.

                  (b) Myogen shall initiate a Phase III study for the purpose of
obtaining FDA Regulatory Approval of a Product after regulatory consultation
with the FDA within 3 years after the Effective Date; provided that in the event
Myogen experiences any delays in complying with this Section 3.6.1(b) that are
caused by parties or events outside of the control of Myogen, including, without
limitation, [*#*] As used in this Section 3.6.1(b), [*#*]

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                  (c) In the event Myogen fails to meet the commercial diligence
requirements of this Article 3.6.1, HMR may in its discretion terminate this
Agreement as provided in Article IX herein.

         3.6.2 HMR'S OBLIGATIONS.

                  (a) Within 120 days after execution of this Agreement, HMR
shall transfer to Myogen the IND for Enoximone, shall deliver to Myogen all HMR
Data in the form in which it is currently available in order to facilitate
commencement of Development hereunder, and thereafter shall provide such
additional HMR Data or data subsequently developed by HMR and its Affiliates
reasonably requested by Myogen.

                  (b) It is expressly understood that HMR has no obligation to
finalize clinical reports but that HMR shall deliver to Myogen the raw data and,
if available, the final clinical reports.

         3.6.3 DEVELOPMENT REPORTS. Myogen shall submit semi-annual written
summary reports which describe the progress of development efforts undertaken by
it, if any, under this Agreement. Summary reports shall include, without
limitation, a description and statement of purpose of each study in progress,
and with respect to clinical trials, the number of patients which enrolled in,
dropped from, or completed the study, as well as any side effect or unexpected
data, and the progress towards the diligence obligations set forth in Article
3.6.1.

         3.6.4 DEVELOPMENT AND COMMERCIALIZATION EXPENSES.

                  (a) During the term of this Agreement, (i) [*#*]

                  (b) [*#*]

         3.7 EXISTING INVENTORY.

                  (a) Within 120 days after the date of execution of the
Agreement, Myogen shall purchase from HMR and HMR shall deliver to Myogen,
approximately [*#*] active ingredient to be used by Myogen for Development.

                  (b) Upon the Transfer Date (as defined in Section 4.1 hereof),
Myogen shall purchase from HMR and HMR shall deliver to Myogen, that number of
kilograms of Enoximone active ingredient [*#*] as shall be determined by
Myogen in its sole discretion upon the Transfer Date.

                  (c) [*#*] of Enoximone active ingredient purchased under
this Section 3.7, payment of which shall be made by Myogen within ten (10)
business days after the relevant shipment has been dispatched by HMR. HMR will
ship the Enoximone "Free Carrier, HMR site Midland, MI, (FCA per INCOTERMS, 1990
version)".

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         3.8 REGULATORY MATTERS.

                  3.8.1 COMPLIANCE WITH REGULATIONS. Myogen, and HMR to the
extent it is providing services will conduct their efforts hereunder in
compliance with all applicable regulatory requirements, including without
limitation, the FDA's Good Clinical Practice, Good Laboratory Practice and Good
Manufacturing Practice regulations and the guidelines of the International
Conference on Harmonization of Technical Requirements for Registration of
Pharmaceuticals for Human Use.

                  3.8.2 REGULATORY FILINGS. After transfer of the IND for
Enoximone that was submitted to the FDA and HMR Data to Myogen, Myogen shall, at
its own expense, prepare and submit all filings with the regulatory authorities
with respect to Enoximone in each Major Market Country (the "Regulatory
Filings"), and Myogen shall be responsible for causing such applications to
progress through the approval process in a timely manner. [*#*] Myogen shall,
promptly after each such Regulatory Filing, deliver to HMR a report with a brief
summary of such Regulatory Filing, which shall be held by HMR subject to the
provisions of Article V.

                  3.8.3 MAINTENANCE OF RECORDS. Myogen shall maintain records
with respect to activities conducted in connection with the Development of
Enoximone in sufficient detail and in the manner appropriate for Regulatory
Approval purposes and in a manner which will reflect all clinical and
pre-clinical studies conducted, results achieved and data obtained by Myogen in
the course of such Development.

                  3.8.4 ADVERSE EVENT REPORTING. After transfer of the IND for
Enoximone that was submitted to the FDA to Myogen, Myogen shall be responsible
for reporting of adverse experience information to meet the current requirements
for Adverse Drug Reaction reporting to the FDA. The parties recognize that the
holder of a IND may be required to submit information regarding adverse events
concerning the Product to various governmental agencies. In addition,
supplemental information may be required to be provided at periodic intervals
and adverse events may be required to be reported at more frequent intervals
depending on the severity of the event.

                                   ARTICLE 4

                            MILESTONES AND ROYALTIES

         4.1 Europe. As consideration for the rights granted to Myogen by HMR
under this Agreement for Europe Myogen shall make the following payments to HMR:

                  (a) Myogen will pay to HMR [*#*] upon signing of this
Agreement;

         (b) Myogen will pay to HMR [*#*] upon the earlier of (i) the approval
by the FDA for Myogen to proceed with Phase III clinical studies with the oral
Formulation of a product or (ii) six (6) months after the Effective Date;

                  (c) On a date no later than one (1) year from the date of
signing (the "Transfer Date"), Myogen shall pay to HMR [*#*] Upon the Transfer
Date (i) HMR shall transfer to

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Myogen any and all of its rights and obligations for Enoximone and Product
commercialization activities in Europe except as specified in this Section
4.1(c), and (ii) HMR shall transfer whatever rights it may have under the
existing HMR Trademarks in the countries listed in Exhibit 4.1.(c). Myogen will
[*#*] prepare and provide the documents necessary to transfer the HMR Trademark
rights. HMR is not transferring, and Myogen does not accept any liabilities
caused by or arising from the manufacture, use, commercialization or sale of the
Product incurred or arising prior to the Transfer Date. All accounts payable or
receivable existing as of the Transfer Date or relating to any periods prior to
the Transfer Date shall remain the accounts payable or receivable of HMR. All
reporting, tax and other responsibilities and obligations relating to the
Enoximone or Product for periods prior to the Transfer Date shall remain with
HMR. All returns of Enoximone or Product shipped prior to the Transfer Date
shall be the responsibility of HMR;

                  (d) On the first anniversary of the Transfer Date, Myogen
shall pay to HMR [*#*]

                  (e) On the second anniversary of the Transfer Date, Myogen
shall pay to HMR [*#*]

                  (f) Beginning on [*#*] Myogen will pay to HMR for a period
of [*#*] years, on a quarterly basis within 60 days after the end of each
calendar quarter, periodic payments equal to [*#*] that occurred in the
immediately preceding calendar quarter;

                  [*#*]

         4.2 TERRITORY OTHER THAN EUROPE. With respect to markets in the
Territory excluding [*#*] and in consideration of the rights granted by HMR
under this Agreement, Myogen shall pay to HMR, on a quarterly basis within sixty
(60) days after the end of each calendar quarter, periodic payments equal to
[*#*] in such markets that occurred in the immediately preceding calendar
quarter.

         4.3 DURATION OF ROYALTY OBLIGATIONS. If this Agreement is not
terminated in accordance with the other provisions hereof, Myogen's obligation
to pay earned royalties hereunder in a particular country shall continue until
[*#*] From and after [*#*] all royalty amounts shall be reduced by [*#*]
but shall in no event be less than [*#*] until the [*#*] after which time
all royalty obligations shall cease entirely.

         4.4 ROYALTY RATE IF GENERICS INTRODUCED. In the event that a generic
version of a Product is marketed in any country of the Territory where no
relevant Patents within the HMR Patents or Joint Patents have issued, the
royalty rate in that country will be reduced to [*#*] of the applicable
royalty provided in Articles 4.1 and 4.2 but shall in no event be less than
three and [*#*]

         4.5 SALES BY SUBLICENSEES. In the event Myogen grants licenses or
sublicenses to others to make or sell Products, such licenses or sublicenses
shall include an obligation for the

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<PAGE>

licensee or sublicensee to account for and report to Myogen its Net Sales of
such Products on the same basis as if such Net Sales were sales by Myogen, and
Myogen shall pay royalties to HMR as if the Net Sales of the sublicensee were
sales of Myogen. Amounts payable by the sublicensee to Myogen on account of the
sublicense shall not be included in amounts deducted from gross sales in
arriving at Net Sales.

         4.6 ROYALTY PAYMENTS AND REPORTS. Royalty payments under this Agreement
shall be made to HMR or its designee along with the report summarizing the Net
Sales of any Products by Myogen, its Affiliates or Sublicensees during the
relevant quarter within sixty (60) days following the end of each calendar
quarter. All payments to HMR shall be in U.S. currency. For the purpose of
calculating payments, the currency exchange rate for converting any currency to
U.S. dollars shall be the exchange rate in the key currency cross rates table in
the final edition of The Wall Street Journal (U.S. Eastern Edition) or in the
case the currency exchange rate is not published in The Wall Street Journal, the
mid-point of the closing bid and ask price of "Reuter's 2000 Information
Service" historical databases, on the last business day of each calendar quarter
to which such payment relates. A "business day" is a day on which banks are open
for business in the country of the currency to be translated. Unless HMR
instructs Myogen otherwise payments pursuant to this Article V shall be made by
bank wire transfer as follows:

                  Citibank, New York
                  Hoechst Marion Roussel, Inc.
                  [*#*]

         4.7 TAXES. HMR shall pay any and all taxes levied on account of
royalties it receives under this Agreement. If laws or regulations require that
taxes be withheld, then Myogen will (i) deduct those taxes from the remittance
royalty, (ii) timely pay the taxes to the proper taxing authority and (iii) send
proof of payment to HMR within thirty (30) days following such payment.

         4.8 BLOCKED CURRENCY. In each country where the local currency is
blocked or cannot be removed from such country, Myogen will pay the royalty owed
on Net Sales in that country in US currency to HMR at the exchange rate in
Article 4.6.

         4.9 PAYMENTS TO OR REPORTS BY AFFILIATES. Any payment required under
any provision of this Agreement to be made to either Party or any report
required to be made by either Party shall be made to or by an Affiliate of that
Party if designated by that Party as the appropriate recipient or reporting
entity.

         4.10 NO MULTIPLE ROYALTIES. No multiple royalties shall be payable
because any Product, its manufacture, use, lease or sale are or shall be covered
by more than one HMR Patent or HMR Know-how licensed under this Agreement.

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                                   ARTICLE 5

                                 CONFIDENTIALITY

         5.1 CONFIDENTIALITY; EXCEPTIONS. Except to the extent expressly
authorized by this Agreement or otherwise agreed in writing, the Parties agree
that, for the term of this Agreement and for [*#*] years thereafter, the
receiving Party shall keep confidential and shall not publish or otherwise
disclose or use for any purpose other than as provided for in this Agreement any
Information related to the Products and other information and materials
furnished to it by the other Party pursuant to this Agreement, or any provisions
of this Agreement that are the subject of an effective order of the Securities
and Exchange Commission granting confidential treatment pursuant to the
Securities Exchange Act of 1934, as amended (collectively, "Confidential
Information"), except to the extent that it can be established by the receiving
Party that such Confidential Information:

                  (a) was already known to the receiving Party at the time of
disclosure by the other Party;

                  (b) was generally available to the public or otherwise part of
the public domain at the time of its disclosure to the receiving Party;

                  (c) became generally available to the public or otherwise part
of the public domain after its disclosure and other than through any act or
omission of the receiving Party in breach of this Agreement;

                  (d) was disclosed to the receiving Party by a Third Party who
had no obligation to the disclosing Party not to disclose such information to
others; or

                  (e) was independently developed by the receiving Party without
breach of the provisions of this Agreement (and can be verified by the
disclosing Party as such).

         5.2 AUTHORIZED DISCLOSURE. Each Party may disclose Confidential
Information hereunder to the extent such disclosure is reasonably necessary in
(i) filing or prosecuting patent applications, (ii) prosecuting or defending
litigation, (iii) complying with applicable laws or regulations or (iv)
conducting pre-clinical or clinical trials, provided that if a Party is required
by law or regulation to make any such disclosure of the other Party's
Confidential Information it will, except where impracticable for necessary
disclosures (e.g., in the event of medical emergency), give reasonable advance
notice to the other Party of such disclosure requirement and, except to the
extent inappropriate in the case of patent applications, will use its reasonable
efforts to secure confidential treatment of such Confidential Information
required to be disclosed. In addition each Party shall be entitled to disclose,
under a binder of confidentiality containing provisions as protective as those
of this Article V, Confidential Information to any Third Party for the purpose
of carrying out the purposes of this Agreement. Nothing in this Article V shall
restrict any Party from using for any purpose consistent with the terms of this
Agreement any Information developed by it during the term of this Agreement.
When a Party makes disclosure of Confidential Information to any of its
employees, it shall obtain an acknowledgment and

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<PAGE>

agreement from each such employee that such employee agrees to be bound by the
provisions of Article 6.1 hereof or the equivalent.

         5.3 SURVIVAL. This Article V shall survive the termination or
expiration of this Agreement for a period of [*#*] years.

         5.4 TERMINATION OF PRIOR AGREEMENT. All Information exchanged between
the Parties under the Confidentiality Agreement between Myogen and HMR, dated as
of February 4, 1997, as amended, shall be deemed Confidential Information and
shall be subject to the terms of this Article V, and shall be included within
the definitions of Myogen Know-how and HMR Know-how.

         5.5 PUBLICATIONS. Except as required by law, each Party agrees that it
shall not publish or present Information or Confidential Information without the
opportunity for prior review by the other Party. Each Party shall provide to the
other the opportunity to review and approve any proposed publications or
presentations (including information to be presented verbally) which relate to
Enoximone or the Products or otherwise constitutes Confidential Information as
early as reasonably practical, but at least four weeks prior to their intended
submission for publication (except, where applicable, with the written consent
of an appropriate officer of the other Party) and such submitting Party agrees,
upon written request from the other Party, not to submit such abstract or
manuscript for publication or to make such presentation until the other Party
consents. It is understood and agreed that the provisions of this Article 5.5
are directed to publications and presentations that may be made to the general
public, including the relevant scientific communities, and that nothing herein
will prevent or limit Myogen from preparing materials that may contain
Information or Confidential Information and making presentations with respect
thereto that are private in nature.

                                   ARTICLE 6

              OWNERSHIP OF INTELLECTUAL PROPERTY AND PATENT RIGHTS

         6.1 OWNERSHIP.

                  6.1.1 HMR shall solely own, and it alone shall have the right
to apply for Patents within and outside of the United States for any inventions
made solely by HMR's personnel or consultants in the course of performing work
under this Agreement.

                  6.1.2 Myogen and/or UTC shall solely own, and Myogen alone
shall have the right to apply for Patents within and outside of the United
States for any inventions made solely by Myogen's personnel or consultants, or
substantially by Myogen with insignificant contribution from HMR, in the course
of performing work under this Agreement.

                  6.1.3 Inventions made jointly by personnel or consultants of
Myogen and HMR, so long as both Parties have made substantial contribution to
the inventions, shall be owned jointly, without accounting, by Myogen and/or UTC
and HMR. The law of joint ownership of inventions of the United States shall
apply to any joint ownership of patents within the United States claiming joint
inventions of the Parties.

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         6.2 DISCLOSURE OF PATENTABLE INVENTIONS. Each Party shall provide to
the other any invention disclosure submitted in the normal course of performing
its obligations hereunder which discloses an invention related to the Enoximone
in the Field or the Products. Such invention disclosures shall be provided to
the other Party promptly after submission and in no event later than ten (10)
days after the end of the calendar quarter in which the disclosure was
submitted, provided, however, that no disclosure is required that would
constitute publication prior to the time a patent issues, and in any case all
submissions will be considered Confidential Information of the Party submitting
the invention disclosure.

         6.3 PATENT FILINGS.

                  6.3.1 MYOGEN AND JOINT PATENTS. Myogen shall prepare, file,
and prosecute Patents for (i) inventions relating to Enoximone that are made
pursuant to Section 6.1.2 hereof by Myogen personnel and consultants (all of
which shall be issued in Myogen's and/or UTC's name and shall be Myogen
Patents), and (ii) inventions relating to Enoximone that are made jointly
pursuant to Section 6.1.3 hereof by personnel and consultants of Myogen and HMR
in the course of the performance of the Parties' obligations under this
Agreement (which shall be issued in HMR's and Myogen's and/or UTC joint name and
shall be "Joint Patents"), and will use reasonable efforts to file initially all
such applications in the United States. With respect to Joint Patents only (A)
the determination of the countries outside of the United States in which to file
patent applications shall be made by Myogen and, if appropriate, UTC; (B) Myogen
shall keep HMR informed of the status of such Patents and shall seek the advice
of HMR with respect to such Patent strategy and draft applications and shall
give reasonable consideration to any suggestions or recommendation of HMR
concerning the preparation, filing, prosecution and maintenance thereof; and (C)
the Parties shall cooperate in good faith in the prosecution of such Patents and
shall share all material Information relating thereto promptly after receipt of
such Information.

                  6.3.2 HMR PATENTS. HMR shall file, prosecute and be entitled
to be issued in its name Patents to cover inventions relating to Enoximone that
are made solely by HMR personnel and consultants (all of which will be HMR
Patents), and will use reasonable efforts to file initially all such
applications in the United States. The determination of the countries outside of
the U.S. in which to file shall be made by mutual agreement of the Parties. If,
however, there is a dispute as to where to file, the more comprehensive filing
shall be made. HMR shall keep Myogen informed of the status of each HMR Patent
and shall seek the advice of Myogen with respect to HMR Patent strategy and
draft applications and shall give reasonable consideration to any suggestions or
recommendations of Myogen concerning the preparation, filing, prosecution and
maintenance thereof. The Parties shall cooperate reasonably in the prosecution
of all applications for HMR Patents and shall share all material Information
relating thereto promptly after receipt of such Information. If, during the term
of this Agreement, HMR intends to allow any HMR Patent under which Myogen has a
license under this Agreement, to lapse or become abandoned without having first
filed a substitute, HMR shall, whenever practicable, notify Myogen of such
intention at least sixty (60) days prior to the date upon which such HMR Patent
shall lapse or become abandoned, and Myogen shall thereupon have the right, but
not the obligation, to assume responsibility for the prosecution and maintenance
thereof (and Patent Expenses shall continue to be shared).

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         6.4 THIRD PARTY PATENT RIGHTS.

                  (a) HMR represents and warrants that to its knowledge that
there are no Third Party rights which may be infringed by the manufacture or
sale of any Product, the use of any Patent, Know-how or any other activity
contemplated by this Agreement.

                  (b) Neither Party makes any representation or warranty to the
other, other than that made in this Section 6.4, with respect to the validity,
enforceability, perfection or dominance of any Patent or other proprietary right
or with respect to the absence of rights of Third Parties which may be infringed
by the manufacture or sale of any Product, the use of any Patent, Know-how or
any other activity contemplated by this Agreement. Each Party agrees to bring to
the attention of the other Party any patent or patent application it discovers,
or has discovered, and which relates to the subject matter of this Agreement.

         6.5 ENFORCEMENT RIGHTS.

                  6.5.1 GENERAL.

                  (a) In the event a Third Party, through the actual or proposed
manufacture, import, use, sale or offer for sale of a product competitive with a
Product being developed or commercialized under this Agreement infringes or is
reasonably likely to infringe ("Competitive Product Infringement") any Myogen
Know-how, Myogen Patent, HMR Know-how, HMR Patents, or Joint Patents, Myogen
and/or UTC shall have the right to institute, prosecute and control any action
or proceeding with respect to such infringement, and the right to any and all
relief, recovery and the like. HMR has the right to participate and be
represented in such action by counsel of its own selection at its own expense.
HMR agrees to be joined as a party plaintiff, if necessary in any such action,
and to give Myogen reasonable assistance and any needed authority to control,
file and to prosecute such action.

                  (b) If either Party learns or determines in good faith that
there is or is a reasonable likelihood of Competitive Product Infringement of
any Myogen Patents, HMR Patents, or Joint Patents by a Third Party, the Party
first having knowledge shall promptly notify the other Party in writing thereof,
which notice shall set forth the facts of such actual or potential infringement
in reasonable detail. If Myogen or HMR, as the case may be, fails to institute
and prosecute an action or proceeding to abate any actual infringement within a
period of ninety (90) days after receiving written notice of actual infringement
or otherwise having knowledge of the actual infringement, then the other Party
shall have the right, but not the obligation, to bring and prosecute any action
and the Party which failed to bring such action agrees to be joined as a party
plaintiff in such action and to give the Party bringing such action reasonable
assistance and all authority to control, file and prosecute the action as may be
necessary; provided, however, that the Party which failed to bring the action
shall have the right to participate and to be represented in any such action by
counsel of its choice; provided, further, that HMR's right to bring such an
action may be limited if the Myogen Patent at issue is owned by UTC (HMR hereby
acknowledges that UTC has the first right to bring an action against an
infringer in the case of a Myogen Patent owned by UTC and licensed to Myogen).

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                  (c) [*#*] and related recoveries with respect to actions
brought under this Article 6.5.1 shall be [*#*] to the benefit of Myogen,
except as otherwise noted herein. Any amounts recovered in such action referred
to in this Article 6.5.1 shall be recovered by Myogen.

                  (d) No settlement or consent judgment or other voluntary final
disposition of suit under this Article 6.5.1 may be entered into without the
joint consent of Myogen and HMR, which consents shall not be withheld
unreasonably or delayed, except with respect to Myogen Patents owned by UTC.

             6.5.2 SETTLEMENT OF THIRD PARTY CLAIMS FOR PRODUCTS; ROYALTY
REDUCTION. If a Third Party asserts that a patent or other right owned by it is
infringed by the manufacture, use or sale of any Product and if following the
conclusion of proceedings brought as a result of such alleged infringement,
Myogen is required to pay the Third Party any payment of any kind for the right
to sell a Product in a particular country, the royalty rate then payable to HMR
attributable only to sales in such country shall be reduced by [*#*] The royalty
rate shall return to its previous level once Myogen has fully satisfied the
payment due to the Third Party. [*#*] No settlement or consent judgment or other
voluntary final disposition of a suit under this Article 6.5.2 may be entered
into without the mutual consent of Myogen and HMR which shall not be
unreasonably withheld or delayed.

             6.5.3 PATENT PROSECUTION RIGHTS. Notwithstanding the
provisions of Article 6.5.1, a Party shall not file or prosecute any action for
infringement of a Patent for which the other Party has the primary
responsibility if the other Party having primary responsibility is prosecuting
at least one such action for infringement of such Patent, without the agreement
of the other Party, which agreement shall not be unreasonably withheld.

         6.6 ASSIGNMENT OF JOINT PATENTS. Neither Party may assign its rights
under any Joint Patent except with the prior written consent of the other Party;
provided, however, that either party may assign such rights without consent to
an Affiliate or other permitted assignee under this Agreement in connection with
a merger or similar reorganization or sale of all or substantially all of its
assets.

                                   ARTICLE 7

                   REPRESENTATIONS AND WARRANTIES; EXCLUSIVITY

         7.1 REPRESENTATIONS AND WARRANTIES. Each Party hereby represents and
warrants to the other Party that this Agreement is a legal and valid obligation
binding on such Party and enforceable in accordance with its terms, subject to
laws regarding bankruptcy or insolvency generally, provided that the Parties
acknowledge and agree that this Agreement constitutes a license of "intellectual
property" as provided in Section 365(n) of the U.S. Bankruptcy Code. The
execution, delivery and performance of the Agreement by such Party does not
conflict with any agreement, instrument or understanding, oral or written, to
which it is a Party or by which it is bound, nor violate any law or regulation
of any court, governmental body or administrative or

                                      -15-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

other agency having jurisdiction over it. Such Party represents and warrants
that it has not, and covenants that during the term of the Agreement it will
not, grant to any Third Party any rights which would conflict or interfere with
or curtail or impair the rights granted to the other Party hereunder.

         7.2 EXCLUSIVITY; [*#*] and Myogen acknowledges that its activities and
operations pursuant to this Agreement shall be the principal mechanism by which
Myogen will commercialize the Products. HMR may terminate this Agreement for
cause pursuant to Article 9.4 hereof in the event of the material breach of this
paragraph 7.2 by Myogen or its Affiliates.

                                   ARTICLE 8

                              INFORMATION & REPORTS

         8.1 RECORDS OF REVENUES AND EXPENSES. Myogen will maintain complete and
accurate accounts and records of revenues, costs, expenses and payments earned
or made in connection with this Agreement and such records shall be available
for examination at HMR's expense during Myogen's reasonable business hours for a
period of two (2) years from creation of the individual records. In addition,
not more often than once each year, HMR may designate a firm of certified public
accountant acceptable to Myogen to verify the correctness of calculations and
classifications of such revenues, costs, expenses or payments earned or made in
connection with this Agreement. Amounts that are determined to be due as a
result of any variances in revenues, costs, expenses or payments earned or made
in connection with this Agreement discovered during such audit shall be paid by
Myogen within thirty (30) days of the conclusion of the audit (subject to
Article XIII hereof). If the audit results in a variance of more than 5% in
favor of HMR, the reasonable audit expenses of HMR shall be paid by Myogen. Any
records or accounting information received from Myogen shall be included within
the definition of Confidential Information for purposes of Article VI. In the
event the provisions of Section 9.5.3 apply, the provisions of this Section 8.1
shall apply to HMR.

         8.2 PUBLICITY REVIEW. Subject to the provisions of this Article 8.2, no
Party shall originate any written publicity, news release, or other public
announcement relating to this Agreement or the performance hereunder or the
existence of an arrangement between the Parties (collectively, "Written
Disclosure"), without the prior prompt review and written approval of the other,
which approval shall not be unreasonably withheld. In addition, each Party
agrees to submit to the other Party, for prompt review and written approval, any
question and answer sheet or similar materials ("Q & A") prior to using such
materials in connection with oral disclosures. With regard to any proposed
Written Disclosure or Q & A by Myogen, HMR shall take into consideration that
Myogen is a specialized privately held company and as such will find it
important to provide ongoing information about this Agreement and the status of
the Collaboration Agreement to investors or potential investors. Recognizing
that it is impractical to have each oral disclosure reviewed in advance, the
Parties agree that oral disclosures by any Party of information which is
immaterial and which relates to this Agreement, or to performance

                                      -16-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

hereunder or the existence of an arrangement between the Parties, shall be
generally consistent with previously approved Written Disclosures or Q & A's.
Notwithstanding the foregoing provisions of this Article 8.2, any Party may make
any public Written Disclosure it believes in good faith is required by
applicable law or any listing or trading agreement concerning its
publicly-traded securities based upon the written advice of counsel, provided
that prior to making such Written Disclosure, the disclosing Party shall provide
the other Party with an opportunity to promptly review the proposed Written
Disclosure. To the extent that the reviewing Party reasonably requests that any
information in the proposed Written Disclosure be deleted, the disclosing Party
shall take reasonable action to avoid disclosure, where possible, including
requesting confidential treatment of such information pursuant to Rule 406 of
the Securities Act of 1933 or Rule 26b-2 of the Securities Exchange Act of 1934,
as applicable (or any other applicable regulation relating to the confidential
treatment of information).

                                   ARTICLE 9

                              TERM AND TERMINATION

         9.1 TERM. This Agreement shall commence as of the Effective Date and
shall terminate as provided herein in its entirety or with respect to certain
countries in the Territory as set forth herein.

         9.2 TERMINATION BY HMR FOR MYOGEN'S FAILURE TO MEET MILESTONES OR
DISCONTINUING DEVELOPMENT. HMR shall have the right to terminate this Agreement
in its entirety under this Section 9.2 only during the period prior to [*#*]
if Myogen shall either: (a) discontinue Development of Product as set forth in
Article 3.6.1(a) or, (b) fails to meet the milestone set forth in 3.6.1(b).
Termination of this Agreement shall be made pursuant to a written notice (the
"Termination Notice") delivered by HMR to Myogen within ninety (90) days after
the expiration of the time period with respect to which such notice is being
delivered. Such termination shall be effective as of thirty (30) days following
delivery of the Termination Notice to Myogen (the "Termination Effective Date").
If HMR terminates this Agreement as set forth above, Myogen may retain all
rights granted under Article II herein to make, manufacture and commercialize
[*#*] Product sold under the trade name Perfan in Europe only ( the "European
Rights") paying a royalty rate of [*#*] to HMR for the duration of the HMR
Patents or for ten (10) years from the Transfer Date whichever is longer;
provided however, that Myogen satisfies all payment requirements of Article 4.1.
In the event HMR terminates this Agreement under this Section 9.2 and Myogen
elects not to retain European Rights, then Myogen shall return to HMR or
destroy, at HMR's discretion, all unused Enoximone [*#*] and all rights granted
under Article II of this Agreement shall terminate.

                  9.2.1 TERMINATION EFFECTIVE DATE. If HMR terminates this
Agreement pursuant to this Section 9.2, the Parties shall continue to perform
their obligations under this Agreement pending the winding down of operations on
the Termination Effective Date (other than with respect to the European Rights
as provided in this Section 9.2). Upon the Termination Effective Date:

                                      -17-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                  (a) all licenses and rights of Myogen to HMR Patents and HMR
Know- how hereunder shall terminate in their entirety with respect to Enoximone
and Product except with respect to the European Rights as provided in this
Section 9.2;

                  (b) all HMR Confidential Information and HMR Data shall be
returned to HMR (except with respect to the European Rights as provided in this
Section 9.2), except Myogen may retain one copy of such information solely for
legal archive purposes;

                  (c) Myogen shall transfer to HMR all INDs, Drug Approval
Applications and Regulatory Approvals related to Enoximone and Product(s) and
shall take such other actions and execute such other instruments, assignments
and documents as may be necessary to effect the transfer of such rights
hereunder to HMR (except with respect to the European Rights as provided in this
Section 9.2); and

                  (d) all Confidential Information of Myogen, excluding that
information transferred pursuant to Article 9.2 (c) above, shall be promptly
destroyed by HMR and HMR shall certify to Myogen such destruction, except HMR
may retain one copy of such information solely for legal archive purposes.

                  (e) Myogen shall return to HMR or destroy, at HMR's
discretion, any unused Enoximone obtained from HMR pursuant to Article 3.7
[*#*] provided, however, that in the event Myogen retains the European Rights,
as provided in this Section 9.2, Myogen shall not be obligated to return any
unused Enoximone.

         9.3 TERMINATION BY HMR FOR MYOGEN'S FAILURE TO COMMERCIALIZE OR MARKET
PRODUCTS IN THE TERRITORY.

              9.3.1 FAILURE TO COMMERCIALIZE IN MAJOR MARKET COUNTRIES. With
respect to each Major Market Country, if Myogen, (i) discontinues Development
(i.e. does not fulfill the criteria set forth in Article 3.6.1(a)) in any such
country, or (ii) does not Commercialize the Product in any such country within
[*#*] after obtaining Regulatory Approval in such country, then HMR shall have
the right to terminate this Agreement with respect to such Major Market
Countries (such countries shall be referred to as "Terminated Countries") and
the definition of the Territory shall thenceforth exclude such countries. HMR
shall provide written notification to Myogen of its intent to deem a particular
country a Terminated Country, and Myogen shall have ninety (90) days following
receipt of such written notice in which to respond to such proposed action. If
Myogen shall in good faith dispute such intention to deem a particular country a
Terminated Country, the Parties shall submit such matter to arbitration pursuant
to the terms of Article XI hereof. As used in this Section 9.3, "Commercialize"
means to commence the commercial sale or commercial distribution of the Product.

              9.3.2 FAILURE TO COMMERCIALIZE IN OTHER COUNTRIES. If Myogen
commercializes a product in all of the Major Market Countries within [*#*] after
obtaining relevant Regulatory Approval in each of these countries, then Myogen
shall have an additional [*#*] to commercialize the Product in other countries
in the Territory. HMR shall have the right, at its option, to terminate Myogen's
rights hereunder with respect to those countries where a Product has not been
commercialized as set forth above (any such countries

                                      -18-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

shall also be referred to as "Terminated Countries"), and the definition of the
Territory shall thenceforth exclude such countries. HMR shall provide written
notification to Myogen of its intent to deem a particular country a Terminated
Country, and Myogen shall have ninety (90) days following receipt of such
written notice in which to respond to such proposed action. If Myogen shall in
good faith dispute such intention to deem a particular country a Terminated
Country, the Parties shall submit such matter to arbitration pursuant to the
terms of Article XI hereof.

              9.3.3 EFFECT OF TERMINATED COUNTRIES. If HMR terminates this
Agreement with respect to a Terminated Country, then the following provisions
shall apply:

                  (a) HMR shall receive an exclusive (even as to Myogen but
subject to the existing rights of Third Parties and if necessary, subject to the
approval of UTC) right and license in the Terminated Countries with the right to
grant sublicenses, to all Myogen Patents, Myogen Know-how and all of Myogen's
interest in trademarks in the Terminated Countries related to Enoximone, to
make, have made, import, use, sell, offer for sale and have sold Products,
subject to the royalty obligations set forth below in Article 9.3.3(c), and
shall have the exclusive right (but not the obligation) to enforce the Patents
against Competitive Product Infringement in the Terminated Countries, except in
cases where UTC reserves this right, and the exclusive right (but not the
obligation) to enforce the trademark rights related to Enoximone against
infringers in the Terminated Countries.

                  (b) Myogen shall transfer all INDs, Drug Approval Applications
and Regulatory Approvals related to Enoximone in the Terminated Countries to
HMR, and take such other actions and execute such other instruments, assignments
and documents as may be necessary to transfer the rights hereunder in the
Terminated Countries to HMR.

                  (c) Subject to Myogen's performance of the provisions of this
Article 9.3.3 and Myogen's fulfillment of its obligations for payments due under
Article 4.1, Myogen shall be entitled to receive royalties with respect to the
Net Sales by HMR or its sublicensees of Products in those Terminated Countries
under Article IX at a rate of [*#*]

         9.4 TERMINATION FOR MATERIAL BREACH BY MYOGEN.

                  (a) Subject to the provisions of this Article 9.4, if Myogen
shall have committed a Material Breach (as defined below) and such Material
Breach shall remain uncured and shall be continuing for a period of ninety (90)
days following receipt of written notice thereof from HMR, then, in addition to
any and all other rights and remedies that may be available, HMR shall have the
right to terminate this Agreement effective upon the expiration of such ninety
(90) day period. Any such written notice of alleged Material Breach from HMR
shall include a reasonably detailed description of all relevant facts and
circumstances demonstrating, supporting and/or relating to each such alleged
Material Breach by Myogen.

                                      -19-

                                          [*#*] CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                  (b) If HMR terminates this Agreement pursuant to the
provisions of this Article 9.4, then the following provisions shall apply:

                           (i) HMR shall receive an exclusive (even as to Myogen
but subject to the existing rights of Third Parties and if necessary, subject to
the approval of UTC) right and license in the Terminated Countries with the
right to grant sublicenses, to all Myogen Patents, Myogen Know-how and all of
Myogen's interest in trademarks in the Terminated Countries related to
Enoximone, to make, have made, import, use, sell, offer for sale and have sold
Products, subject to the royalty obligations set forth above in Article
9.3.3(c), and shall have the exclusive right (but not the obligation) to enforce
the Patents against Competitive Product Infringement in the Terminated Countries
at its sole expense, except in cases where UTC, reserves this right, and the
exclusive right (but not the obligation) to enforce the trademark rights related
to Enoximone against infringers in the Terminated Countries.

                           (ii) all licenses and rights in the HMR Patents, HMR
Know- how and HMR Trademarks granted to Myogen hereunder shall terminate;

                           (iii) all Confidential Information supplied by each
Party to the other Party shall be promptly destroyed by each Party and each
Party shall certify such destruction to the other, except that each Party may
retain one copy of such information solely for legal archive purposes;

                           (iv) Myogen shall cooperate in the transfer to HMR of
all NDAs, Drug Approval Applications and Regulatory Approvals related to
Enoximone, and shall take such other actions and execute such other instruments,
assignments and documents as may be necessary to effect the transfer of rights
hereunder to HMR.

                  (c) Termination of this Agreement pursuant to this Article 9.4
shall not relieve Myogen of any liability, including any obligation to make
payments hereunder, which accrued hereunder prior to the effective date of such
termination, nor preclude HMR from pursuing all rights and remedies it may have
hereunder or at law or in equity with respect to any breach of this Agreement
nor prejudice HMR's right to obtain performance of any obligation.

                  (d) For purposes of this Article 9.4 and Article 9.6,
"Material Breach" shall mean the breach or failure to perform, in a material
respect, a material obligation under this Agreement. Without limiting the
foregoing and by way of example only, the term "Material Breach" shall be deemed
to include the failure of Myogen in a material respect to meet Myogen's payment
or non-compete obligations. In no event shall a failure to meet timelines
specified in any Research and Development Plan, in and of itself, be deemed to
constitute a Material Breach in the event such failure is caused by parties or
events outside the control of Myogen, including, without limitation, any
additional requirements imposed by the FDA.

                  (e) The provisions of this Article 9.4 shall survive
termination of this Agreement for a period of [*#*].

                                      -20-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

         9.5 TERMINATION WITHOUT CAUSE.

              9.5.1 TERMINATION WITHOUT CAUSE (INCLUDING DENIAL OF [*#*]).
Myogen shall have a continuing right, subject to this Article 9.5, to terminate
this Agreement, (a) without cause, effective upon [*#*] advance written notice
to HMR, or (b) upon written notice to HMR, if within [*#*] after the Effective
Date Myogen has not received necessary consent or the like from the FDA to [*#*]
for Enoximone ((a), (b), or both (a) and (b), "Termination Without Cause").

              9.5.2 EFFECT OF TERMINATION WITHOUT CAUSE. If Myogen
terminates pursuant to this Article 9.5, then:

                  (a) all licenses and rights in the HMR Patents, HMR Know-how
and HMR Trademarks granted to Myogen hereunder shall terminate;

                  (b) all Confidential Information supplied by HMR to Myogen
shall be returned to HMR, except Myogen may retain one copy of such information
solely for legal archive purposes;

                  (c) Myogen shall cooperate in the transfer of all NDAs, Drug
Approval Applications and Regulatory Approvals related to Enoximone to HMR, and
shall take such other actions and execute such other instruments, assignments
and documents as may be necessary to effect the transfer of rights hereunder to
HMR.

              9.5.3 [*#*] UPON TERMINATION WITHOUT CAUSE. Notwithstanding
anything in this Article 9.5 to the contrary, if, and only if, (i) Myogen
terminates this Agreement pursuant to this Article 9.5 subsequent to the filing
by Myogen of an NDA covering the use of Enoximone in the Field but prior to the
completion of Myogen's due diligence obligations set forth in Article III of
this Agreement, (ii) HMR or any of its sublicensees completes the development
and commercialization of Enoximone and (iii) Myogen fulfills all of its
obligations for payments due under Article 4.1, then Myogen shall be entitled to
[*#*].

              9.5.4 TERMINATION DUE TO EXPIRATION OF ROYALTY OBLIGATIONS.
Unless earlier terminated, this Agreement shall terminate on a country by
country basis upon expiration of Myogen's obligation to pay royalties in such
countries pursuant to this Agreement.

              9.5.5 TERMINATION BY MUTUAL CONSENT. This agreement may be
terminated by the mutual written consent of the parties.

              9.5.6 ACCRUED RIGHTS, SURVIVING OBLIGATIONS. Termination,
relinquishment or expiration of the Agreement or any portion hereof for any
reason shall be without prejudice to any rights which shall have accrued to the
benefit of either Party prior to such termination, relinquishment or expiration,
including damages arising from any breach hereunder. Such termination,
relinquishment or expiration shall not relieve either Party from obligations
which are expressly indicated to survive termination or expiration of this
Agreement.

                                      -21-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

         9.6 TERMINATION FOR MATERIAL BREACH BY HMR.

                  (a) Subject to the provisions of this Article 9.6, if HMR
shall have committed a Material Breach (as defined below) and such Material
Breach shall remain uncured and shall be continuing for a period of ninety (90)
days following receipt of written notice thereof from Myogen, then, in addition
to any and all other rights and remedies that may be available to Myogen, Myogen
shall have the right to terminate this Agreement effective upon the expiration
of such ninety (90) day period. Any such written notice of alleged Material
Breach from Myogen shall include a reasonably detailed description of all
relevant facts and circumstances demonstrating, supporting and/or relating to
each such alleged Material Breach by HMR.

                  (b) If Myogen terminates this Agreement pursuant to the
provisions of this Article 9.6, the following provisions apply:

                           (i) all licenses and rights in the HMR Patents, HMR
Know-how and HMR Patents granted to Myogen hereunder shall [*#*]

                           (ii) all Confidential Information supplied by Myogen
to HMR shall be promptly returned to Myogen, except that HMR may retain one copy
of such information solely for legal archive purposes.

                  (c) Termination of this Agreement pursuant to this Article 9.6
shall not relieve HMR of any liability hereunder which accrued prior to the
effective date of such termination, nor preclude Myogen from pursuing all rights
and remedies it may have hereunder or at law or in equity with respect to any
breach of this Agreement, nor prejudice Myogen's right to obtain performance of
any obligation.

                  (d) For purposes of this Article 9.6, "Material Breach" shall
have the same meaning as it does for Article 9.4. By way of example only, the
term "Material Breach" shall be deemed to include the violation of the exclusive
nature of the grant of licenses and rights to Myogen under this Agreement, the
failure of HMR to supply the HMR Data, the failure of HMR to transfer the IND,
and the failure of HMR to transfer its rights pursuant to 4.1(c).

         9.7 TRANSFER OF TRADEMARK UPON TERMINATION. Should the agreement
terminate for any reason pursuant to this Article IX, other than pursuant to
section 9.6, at the written request of HMR, Myogen shall transfer to HMR its
rights under the HMR Trademarks previously assigned to it by HMR under section
4.1(c) hereof.

                                   ARTICLE 10

                                 INDEMNIFICATION

         10.1 INDEMNIFICATION BY HMR.

              10.1.1 MYOGEN INDEMNIFIED PARTIES. HMR hereby agrees to
indemnify, save, defend and hold Myogen and its agents and employees (the
"Myogen Indemnified Parties")

                                      -22-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

harmless from and against any and all suits, claims, actions, demands,
liabilities, expenses and/or loss, including reasonable legal expense and
attorneys' fees (collectively, "Losses"), incurred by or against any Myogen
Indemnified Parties, which arise out of the breach of this Agreement by HMR, or
any negligence or willful misconduct by HMR, except to the extent such Losses
are attributable to the breach of this Agreement by Myogen or any Myogen
Indemnified Parties or any negligence or willful misconduct by Myogen or any
Myogen Indemnified Parties.

              10.1.2 NOTICE OF CLAIM. In the event that a Myogen Indemnified
Party seeks indemnification under Article 10.1.1, it shall inform HMR of such
claim as soon as reasonably practicable after it receives notice of the claim
and shall permit HMR to assume direction and control of the defense of the claim
(including the right to settle the claim solely for monetary consideration), and
shall cooperate as reasonably requested (at the expense of HMR) in the defense
of the claim.

         10.2 INDEMNIFICATION BY MYOGEN.

              10.2.1 HMR INDEMNIFIED PARTIES. Myogen hereby agrees to
indemnify, save, defend and hold HMR and its agents and employees (the "HMR
Indemnified Parties") harmless from and against any and all Losses incurred by
or against such HMR Indemnified Parties which (i) arise out of the breach of
this Agreement by Myogen, or any negligence or willful misconduct by Myogen,
except to the extent such Losses are attributable to the breach of this
Agreement by HMR or any HMR Indemnified Parties or any negligence or willful
misconduct by HMR or any HMR Indemnified Parties , or (ii) arise out of the
design, manufacture, use, handling, storage, sale or other disposition of
Products by Myogen, its agents or sublicensees, except to the extent such Losses
also result from the negligence or willful misconduct of any HMR Indemnified
Parties

              10.2.2 NOTICE OF CLAIM. In the event that any HMR Indemnified
Party seeks indemnification under Article 10.2.1, it shall inform Myogen of a
claim as soon as reasonably practicable after it receives notice of the claim
and shall permit Myogen to assume direction and control of the defense of the
claim (including the right to settle the claim solely for monetary
consideration), and shall cooperate as reasonably requested (at the expense of
Myogen) in the defense of the claim.

              10.2.3 INSURANCE.

                  (a) Throughout the Term and thereafter for a period of ten
years (if such insurance is on a claims-made basis), each party shall carry and
maintain in full force and effect insurance with an insurance company or
companies having a Best's rating of A or higher against clinical trials
liability, commercial general liability, and/or product liability with respect
to such Product. Each Party shall include the other Party as an additional
insured under such Insurance policies. Such policies may be worldwide blanket
policies.

                  (b) Such insurance shall be unimpaired by claims, and shall
include indemnity against liability on the part of either Party and any of its
Affiliates, as well as HMR, as their interests may appear, due to injury,
disability or death of any person or persons, or injury to property, arising
from the manufacture, sale or use of such Product or components thereof in

                                      -23-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

amounts of not less than [*#*] million combined single limit, bodily injury
and property damage. Within 30 days after the date hereof, each Party shall
furnish the other Party with certificates of insurance evidencing the aforesaid
coverage and naming the other Party as an additional insured thereunder, which
certificates shall describe the principal terms of such policy or policies and
provide that 30 days prior written notice of cancellation or material changes in
said insurance policies will be given to the other Party.

                  (c) The indemnification obligations herein shall apply on a
first dollar basis, without limitation or reduction to any deductible or
self-insured retention which the Parties may have under their insurance
coverage.

                  (d) The provisions of this Article X shall survive the
expiration or termination of this Agreement for a period of ten years following
the effective date of such expiration or termination.

                                   ARTICLE 11

                               DISPUTE RESOLUTION

         11.1 GENERAL. The Parties recognize that disputes as to certain matters
may from time to time arise during the term of this Agreement which relate to
either Party's rights and/or obligations hereunder. It is the objective of the
Parties to establish procedures to facilitate the resolution of disputes rising
under this Agreement in an expedient manner by mutual cooperation and without
resort to litigation. To accomplish this objective, the Parties agree to follow
the procedures set forth in this Article XI if and when a dispute arises under
this Agreement.

         11.2 NEGOTIATION. Either Party may, by written notice to the other,
have such dispute referred to their respective executive officers designated
below or their successors, for attempted resolution by good faith negotiations
within fourteen (14) days after such notice is received. Said designated
officers are as follows:

              FOR HMR:  Head of Business Development and Strategic Planning

              FOR MYOGEN:  Chief Executive Officer

In the event the designated executive officers are not able to resolve such
dispute, either Party may at anytime after the fourteen (14) day period seek to
resolve the dispute through the means provided in Article 11.3.

         11.3 ARBITRATION. Any dispute, controversy or claim arising out of or
relating to this Agreement or the validity, construction, enforceability or
performance hereof or thereof, including without limitation disputes relating to
alleged breach or to termination of this Agreement, but excluding any dispute,
controversy or claim arising out of or relating to the validity, enforceability
or infringement of any Patent, shall be finally and exclusively resolved by
arbitration by binding Alternative Dispute Resolution ("ADR") pursuant to the
Commercial Arbitration Rules and the administration of the American Arbitration
Association for Large, Complex Cases then in effect. Arbitral proceedings shall
be conducted in Kansas City, Missouri,

                                      -24-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

if requested and begun by Myogen and in Denver, Colorado if requested and begun
by HMR, before three (3) arbitrators. The arbitral panel may award any remedy
allowed by law, including money damages, prejudgment interest and attorneys'
fees, and may grant final, complete, interim, or interlocutory relief, including
injunctive relief. Notwithstanding the foregoing, punitive, exemplary or
multiple damages may not be awarded.

              11.3.1 LEGAL FEES. Except as set forth in Article 11.3 above,
each Party shall bear its own legal fees.

              11.3.2 CONFIDENTIALITY. The ADR proceeding shall be
confidential and the arbitral panel shall issue appropriate protective orders to
safeguard each Party's Confidential Information. Except as required by law, no
Party shall make (or instruct the arbitrator to make) any public announcement
with respect to the proceedings or decision of the arbitrator without prior
written consent of each other Party. The existence of any arbitrated dispute,
and the award, shall be kept in confidence by the Parties and the arbitral
panel, except as required in connection with the enforcement of such award or as
otherwise required by applicable law.

         11.4 SURVIVABILITY. Any duty to arbitrate under this Agreement shall
remain in effect and enforceable after termination of this Agreement for any
reason for the statute of limitations applicable to any disputes arising out of
this Agreement.

         11.5 JURISDICTION. For the purpose of this Article XI, each Party
agrees to abide by the award rendered in any arbitration, and the Parties agree
to accept the jurisdiction of any court having jurisdiction over it for the
purposes of enforcing awards entered pursuant to this Article and for enforcing
the agreements reflected in this Article.

                                   ARTICLE 12

                                  MISCELLANEOUS

         12.1 ASSIGNMENT; BINDING EFFECT.

              12.1.1 ASSIGNMENT TO AFFILIATES. Either Party may assign any
of its rights or obligations under this Agreement in any country in the
Territory to any Affiliates; provided, however, that such assignment shall not
relieve the assigning Party of its responsibilities for performance of its
obligations under this Agreement.

              12.1.2 ASSIGNMENT TO NON-AFFILIATES. Either Party may assign
any of its rights or obligations under this Agreement or its ownership interest
in Joint Patents to a non-Affiliate only in connection with a merger or similar
reorganization or the sale of all or substantially all of its assets, or
otherwise with the prior written consent of the other Party. This Agreement
shall survive any such merger or reorganization of either Party with or into, or
such sale of assets to, a Third Party and no consent for such merger,
reorganization or sale shall be required hereunder; provided, that in the event
of such merger, reorganization or sale, no intellectual property rights of the
acquiring corporation shall be included in the Patents licensed.

                                      -25-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

              12.1.3 BINDING EFFECT. This Agreement shall be binding upon
and inure to the benefit of the Parties and their respective successors and
permitted assigns of the Parties. Any assignment not in accordance with this
Agreement shall be void and of no effect.

         12.2 RESEARCH AND DEVELOPMENT ENTITIES. Either Party may assign its
rights and obligations under this Agreement to an entity or entities (e.g.,
partnership or corporation) that are specifically formed for financial purposes
and that finance research and development performed by such Party; provided,
however, that such assignment shall not relieve the assigning Party of
responsibility for performance of its obligations under this Agreement.

         12.3 CONSENTS NOT UNREASONABLY WITHHELD. Whenever provision is made in
this Agreement for either Party to secure the consent or approval of the other,
such consent or approval shall not unreasonably be withheld or delayed. Whenever
provision is made in this Agreement for one Party to object or to disapprove a
matter, such objection or disapproval shall not be unreasonably exercised.

         12.4 FORCE MAJEURE. Neither Party shall lose any rights hereunder or be
liable to the other Party for damages or losses on account of failure of
performance by the defaulting Party if the failure is occasioned by government
action, war, fire, explosion, flood, strike, lockout, embargo, act of God, or
any other similar cause beyond the control of the defaulting Party, provided
that the Party claiming force majeure has exerted all reasonable efforts to
avoid or remedy such force majeure; provided, however, that in no event shall a
Party be required to settle any labor dispute or disturbance. The foregoing
shall not affect either Party's rights hereunder to terminate this Agreement in
its entirety or with respect to the Product or certain countries in the
Territory pursuant to the terms hereof.

         12.5 FURTHER ACTIONS. Each Party agrees to execute, acknowledge and
deliver such further instruments and do all such other acts as may be necessary
or appropriate in order to carry out the purposes and intent of this Agreement.

         12.6 NO TRADEMARK RIGHTS. Except as otherwise provided herein or
otherwise agreed to in writing by the Parties, no right, express or implied is
granted by this Agreement to use in any manner the name "Myogen," "HMR" or any
other trade name or trademark of the other Party or its Affiliates in connection
with the performance of the Agreement.

         12.7 NOTICES. All notices hereunder shall be in writing and shall be
deemed given if delivered personally or by facsimile transmission (receipt
verified), mailed by registered or certified mail (return receipt requested),
postage prepaid, or sent by a nationally recognized express courier service, to
the Parties at the following address (or at such other address for a Party as
shall be specified by like notice; provided, that notices of a change of address
shall be effective only upon receipt thereof).

                                      -26-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

         IF TO MYOGEN, ADDRESSED TO: MYOGEN, INC.
                                     Fitzsimmons Bldg. 500, P.O. Box 6366
                                     Denver, Colorado 80045-0366
                                     Attention: President
                                     Telephone: (303) 331-1264
                                     Telecopy:  (303) 331-1268

         IF TO HMR, ADDRESSED TO:    HOECHST MARION ROUSSEL, INC.
                                     Route 202-206, P.O. Box 6800
                                     Bridgewater, NJ 08807-0800
                                     Attention: Vice President, General Counsel
                                                Legal Department
                                     Telephone: (908) 231-3537
                                     Telecopy:  (908) 231-4480

         12.8 WAIVER. Except as specifically provided for herein, the waiver
from time to time by either Party of any of their rights or their failure to
exercise any remedy shall not operate or be construed as a continuing waiver of
same or of any other of such Party's rights or remedies provided in this
Agreement. All such waivers shall be in writing.

         12.9 SEVERABILITY. If any term, covenant or condition of this Agreement
or the application thereof to any party or circumstance shall, to any extent, be
held to be invalid or unenforceable, (i) the remainder of this Agreement, or the
application of such term, covenant or condition to the Parties or circumstances
other than those as to which it is held invalid or unenforceable shall not be
affected thereby and each term, covenant or condition of this Agreement shall be
valid and be enforced to the fullest extent permitted by law; and (ii) the
Parties hereto covenant and agree to renegotiate any such term, covenant or
application thereof in good faith in order to provide a reasonably acceptable
alternative to the term, covenant or condition of this Agreement or the
application thereof that is invalid or unenforceable, it being the intent of the
Parties that the basic purposes of this Agreement are to be effectuated.

         12.10 AMBIGUITIES. Ambiguities, if any, in this Agreement shall not be
construed against either Party, irrespective of which Party may be deemed to
have authored the ambiguous provision.

         12.11 GOVERNING LAW. This Agreement shall be governed by and
interpreted under the laws of the State of Delaware, without regard to
principles of conflicts of law.

         12.12 HEADINGS. The Article and paragraph headings contained herein are
for the purposes of convenience only and are not intended to define or limit the
contents of said Articles or paragraphs and do not form a part of this
Agreement.

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

         12.14 ENTIRE AGREEMENT. This Agreement and the Confidentiality
Agreement, including all Exhibits attached hereto and thereto, and all documents
delivered concurrently

                                      -27-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

herewith, set forth all the covenants, promises, agreements, warranties,
representations, conditions and understandings between the Parties hereto and
supersede and terminate all prior agreements, warranties, representations,
conditions or understandings, either oral or written, between the Parties other
than as specifically set forth herein and therein. No subsequent alteration,
amendment, change or addition to this Agreement shall be binding upon the
Parties hereto unless reduced to writing and signed by the respective authorized
officers of the Parties.

         12.15 ADDITIONAL AGREEMENTS. The Parties agree that after the execution
of this Agreement they will enter into to good faith negotiations with respect
to an Interim Supply Agreement and a Technical Agreement for Product supply by
HMR.

                                      -28-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

         IN WITNESS WHEREOF, the Parties have executed this Agreement in
duplicate originals by their duly authorized officers as of the date and year
first above written.

<Table>
<S>                                                    <C>
MYOGEN, INC.                                           HOECHST MARION ROUSSEL, INC.

By:    /s/ J. William Freytag                          By:      /s/ M A Yeomans
   -------------------------------------------            ------------------------------------------

Name:  J. William Freytag                              Name:    Michael A. Yeomans
     -----------------------------------------              ----------------------------------------

Title: President & CEO                                 Title: Vice President, Licensing & Alliances
      ----------------------------------------               ---------------------------------------
</Table>

                                      -29-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                                  SCHEDULE 1.14

                                     [*#*]

                                      -30-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                                  SCHEDULE 1.23

                                     [*#*]
                     INTELLECTUAL PROPERTY LICENSE AGREEMENT

                 FILED SEPARATELY AS AN EXHIBIT TO THE COMPANY'S
                      REGISTRATION STATEMENT OF FORM S-1.

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

                                   ----------

                                      -31-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                                   EXHIBIT 3.4
                                DEVELOPMENT PLAN

                                    [*#*]

                                      -32-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                                 SCHEDULE 3.6.4

Non-exempt personnel:  [*#*] per hour

Exempt personnel:  [*#*] per hour

                                      -33-

                                           [*#*]CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                                 EXHIBIT 4.1 (c)
                         PERFAN - ALL ACTIVE TRADEMARKS

                                    09/28/98

[*#*]

                                      -34-

                                          [*#*] CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

                                 First Amendment

                                     to the

                                License Agreement

                                   (Enoximone)

                                 By and Between

                          Hoechst Marion Roussel, Inc.

                                       and

                                  Myogen, Inc.

         This First Amendment is effective this 23rd day of November 1999, by
and between Hoechst Marion Roussel, Inc., ("HMR") a Delaware corporation and
Myogen, Inc. ("Myogen") a Delaware corporation, generally referred to as a
"Party" and together as the "Parties."

                                   BACKGROUND

         HMR and Myogen entered into a License Agreement dated October 1, 1998
(the "License Agreement"). The Parties now wish to amend the License Agreement
to change the Milestone and Royalty obligations, the Transfer Date and to add
Co-Marketing rights.

         NOW, THEREFORE, in consideration of the mutual promises and agreements
set forth herein, the Parties hereto agree as follows:

                                       1.

                                          [*#*] CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

1.  Capitalized terms not otherwise defined herein shall have the meanings set
    forth in the License Agreement.

2.  ARTICLE I, section 1.40 "Transfer Date" is deleted entirely and replaced
    with the following:

        1.40 "Transfer Date" shall mean the actual date that the transfer of
    European rights from HMR to Myogen commences, but in no event later than
    [*#*].

3.  ARTICLE II is amended to add a new section 2.4.

        2.4 Co-Marketing Rights. After the Transfer Date, [*#*] to HMR, Myogen
    grants to HMR the right to co-market in Europe, under terms and conditions
    to be negotiated in good faith which are consistent with standards for the
    pharmaceutical industry, the oral Enoximone product being developed by
    Myogen. If additional studies are required for European registration and HMR
    elects to perform these studies then the terms of the co-marketing agreement
    will be adjusted accordingly to reflect HMR's contribution to the
    development of European Enoximone. If HMR exercises its right to co-market,
    HMR shall market the oral Enoximone product under HMR's trade name.

4.  ARTICLE III, section 3.7(c) is amended to read in its entirety:

        (c) HMR shall invoice and charge Myogen [*#*] per kilogram of
    Enoximone active ingredient purchased under this Section 3.7, payment of
    which shall be made by Myogen in four quarterly payments beginning on
    [*#*]. HMR will ship the Enoximone [*#*].

                                       2.

                                          [*#*] CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

5.  ARTICLE IV, section 4.1(c) is amended by deleting the first sentence only
    and adding in its place:

        (c) [*#*], Myogen shall pay to HMR [*#*] payable in quarterly
    payments of [*#*] due no later than the first day of each calendar
    quarter.

6.  ARTICLE IV, sections 4.1 (d) and 4.1 (e) are deleted entirely and replaced
    with the following:

        (d) [*#*], Myogen shall pay to HMR [*#*] payable in quarterly
    payments of [*#*] due no later than the first day of each calendar
    quarter.

        (e) [*#*], Myogen shall pay to HMR [*#*] payable in quarterly
    payments of [*#*] due no later than the first day of each calendar
    quarter.

7.  ARTICLE IV section (f) is amended by deleting [*#*] and adding in its
    place [*#*].

8.  ARTICLE IV, section 4.3 is amended to change the last sentence to read:

        ...From and after the expiration of such claims, all royalty amounts,
    excluding those [*#*] shall be reduced by [*#*] but shall in no event be
    less than [*#*] until the [*#*] anniversary of the first commercial sale
    of the relevant Product in such country after which time all royalty
    obligations shall cease entirely.

                                       3.

                                          [*#*] CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

Except as amended hereby, the License Agreement shall remain unchanged and in
full force and effect.

         IN WITNESS WHEREOF, the Parties have caused this First Amendment to be
executed by their duly authorized representatives as of this date set forth
above.

HOECHST MARION ROUSSEL, INC.                  MYOGEN, INC.

By: /s/ Signature Illegible                   By: /s/ J. William Freytag
    ------------------------------                -----------------------------
Title:                                        Title: President and CEO
      ----------------------------                  ---------------------------

                                       4.

                                          [*#*] CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

              SECOND AMENDMENT TO THE LICENSE AGREEMENT (ENOXIMONE)

                                 BY AND BETWEEN

                          AVENTIS PHARMACEUTICALS INC.
                     (FORMERLY HOECHST MARION ROUSSEL, INC.)

                                       AND

                                  MYOGEN, INC.,

         This Second Amendment to the License Agreement (Enoximone) by and
between Aventis Pharmaceuticals Inc. (formerly Hoechst Marion Roussel, Inc.) and
Myogen, Inc., effective October 1, 1998 ("Second Amendment" and "License
Agreement," respectively) is effective this ____ day of May 2003 ("Effective
Date"), by and between Aventis Pharmaceuticals Inc., a Delaware corporation with
a principal office at 300 Somerset Corporate Blvd, Bridgewater, New Jersey 08807
("Aventis"), and Myogen, Inc., a Delaware corporation with a principal office at
7575 W. 103rd Avenue, suite 102, Westminster, CO 80021-5426 ("Myogen") (each
individually a "Party" and collectively "Parties").

                                   BACKGROUND

         Aventis and Myogen entered into the License Agreement on October 1,
1998, and subsequently amended it for the first time on November 25, 1999
("First Amendment"). Among other changes to the License Agreement, the First
Amendment added Section 2.4 Co-Marketing Rights, whereby Myogen granted to
Aventis the right to co-market the oral Enoximone product in Europe. The Parties
now wish to modify the terms of the First Amendment to terminate all such rights
granted to Aventis under the First Amendment to co-market the oral Enoximone
product in Europe; and, in consideration for the termination of the co-marketing
rights, to amend the License Agreement to provide for a royalty to be paid by
Myogen to Aventis if the Net Sales of the oral Enoximone product in Europe reach
or exceed the threshold described below.

         NOW, THEREFORE, in consideration of the mutual promises and agreements
set forth in this Second Amendment, the Parties agree as follows:

1. GRANT BACK OF CO-MARKETING RIGHTS RELATING TO ORAL ENOXIMONE PRODUCT.

         (a)      The license granted by Myogen to Aventis in Paragraph 3 of the
                  First Amendment (which added a new Section 2.4 to Article II
                  of the License Agreement) to co-market in Europe the oral
                  Enoximone product being developed by Myogen is hereby
                  terminated. Accordingly, Section 2.4 of the License Agreement
                  is hereby deleted in its entirety.

         (b)      It is understood that notwithstanding anything contained in
                  the License Agreement to the contrary, Aventis shall not have
                  any obligation of any

                                    1   [/\#/\] CONFIDENTIAL TREATMENT REQUESTED

<PAGE>

                  kind, financial or otherwise, with respect to the development
                  or co-marketing in Europe of the oral Enoximone product being
                  developed by Myogen.

2. Section 4.1(f) is amended and restated as follows:

         (f) Beginning [/\#/\], Myogen will pay to Aventis for a period of
[/\#/\] on a quarterly basis within sixty (60) days after the end of each
calendar quarter, periodic payments equal to the following percentage of Net
Sales in Europe that occurred during the immediately preceding calendar quarter:

                  (1) [/\#/\] of Net Sales in Europe less than [/\#/\] in a
                  calendar year; and,

                  (2) [/\#/\] of the incremental Net Sales in Europe that equal
                  or exceed [/\#/\] in a calendar year.

3. MISCELLANEOUS.

         (a)      Capitalized terms not otherwise defined in this Second
                  Amendment shall have the meaning set forth in the License
                  Agreement.

         (b)      Except as expressly modified by this Second Amendment, the
                  terms and conditions of the License Agreement (as previously
                  amended by the First Amendment) shall remain unchanged and in
                  full force and effect.

                  (REMAINDER OF PAGE INTENTIONALLY LEFT BLANK)

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

         IN WITNESS WHEREOF, the Parties have caused this Second Amendment to be
executed by their duly authorized representatives as of the Effective Date set
forth above.

AVENTIS PHARMACEUTICALS INC.               MYOGEN, INC.

By: /s/ Michael A. Yeomans, Ph.D.          By: /s/ J. William Freytag
    ----------------------------------         ---------------------------------

Title: VP, Head of Global Business         Title: President & CEO
       -------------------------------            ------------------------------
       Development
       -------------------------------

Date:     6/12/03                          Date: 5/6/03
       -------------------------------           -------------------------------

                                    3   [/\#/\] CONFIDENTIAL TREATMENT REQUESTED

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