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                                                                    EXHIBIT 10.6

                                  MYOGEN, INC.

                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

         THIS SERIES D PREFERRED STOCK PURCHASE AGREEMENT (the "AGREEMENT") is
entered into as of this 21st day of August, 2001, by and among MYOGEN, INC., a
Delaware corporation (the "COMPANY") and EACH OF THOSE PERSONS AND ENTITIES,
SEVERALLY AND NOT JOINTLY, WHOSE NAMES ARE SET FORTH ON THE SCHEDULE OF
PURCHASERS ATTACHED HERETO AS EXHIBIT A (which persons and entities are
hereinafter collectively referred to as "PURCHASERS" and each individually as a
"PURCHASER").

                                    RECITALS

         WHEREAS, the Company has authorized the sale and issuance of up to an
aggregate of forty four million four hundred twenty-one thousand eight hundred
seventeen (44,421,817) shares of its Series D Preferred Stock (the "SHARES");

         WHEREAS, Purchasers desire to purchase the Shares on the terms and
conditions set forth herein; and

         WHEREAS, the Company desires to issue and sell the Shares to Purchasers
on the terms and conditions set forth herein;

         NOW, THEREFORE, in consideration of the foregoing recitals and the
mutual promises hereinafter set forth, the parties hereto agree as follows:

1. AGREEMENT TO SELL AND PURCHASE

         1.1 AUTHORIZATION OF SHARES. On or prior to the First Closing (as
defined in Section 2 below), the Company shall have authorized (i) the sale and
issuance to Purchasers of the Shares having the rights, preferences, privileges
and restrictions set forth in the Restated Certificate of Incorporation of the
Company, as amended, in the form attached hereto as Exhibit B (the "RESTATED
CERTIFICATE") and (ii) the issuance of such shares of Common Stock to be issued
upon the conversion of the Shares (the "CONVERSION SHARES").

         1.2 SALE AND PURCHASE. Subject to the terms and conditions hereof, the
Company hereby agrees to issue and sell to each Purchaser and each Purchaser
agrees to purchase from the Company, the number of Shares set forth opposite
such Purchaser's name on Exhibit A at a purchase price of one dollar and
thirty-seven and one-half cents ($1.375) per share.

2. CLOSING, DELIVERY AND PAYMENT

         2.1 CLOSING. The closing of the sale and purchase of the Shares under
this Agreement shall take place on the date hereof (the "FIRST CLOSING") and at
a Second Closing, if any, (as defined below, and each of the First Closing and
the Second Closing shall be a "CLOSING") at the offices of Cooley Godward LLP,
380 Interlocken Crescent, Suite 900, Broomfield, Colorado

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80021 or at such other time or place as the Company and Purchasers may mutually
agree (each such date is hereinafter referred to as a "CLOSING DATE").

         2.2 DELIVERY. At each Closing, subject to the terms and conditions
hereof, the Company will deliver to the Purchasers a certificate representing
the number of Shares to be purchased at the Closing by each Purchaser, against
payment of the purchase price therefor by certified check or wire transfer of
immediately available funds made payable to the Company, in exchange for
services previously rendered or any combination of the foregoing.

         2.3 SECOND CLOSING. At any time on or before the 60th day following the
First Closing or at such time as the Company and the holders of a majority of
the Shares purchased at the First Closing (pursuant to Section 2.1) may mutually
agree, the Company may sell the balance of the Shares not sold at the First
Closing to such persons as may be approved by the Board of Directors of the
Company (the "ADDITIONAL PURCHASERS"). Such sales made at the Second Closing,
(i) shall be made on the terms and conditions set forth in this Agreement, (ii)
the representations and warranties of the Company set forth in Section 3 hereof
(and the Schedule of Exceptions) shall speak as of the First Closing and the
Company shall have no obligation to update any such disclosure, (iii) the
representations and warranties of the Additional Purchasers in Section 4 hereof
shall speak as of such Second Closing and (iv) the conditions of the Additional
Purchasers' obligations at the Second Closing shall be those set forth in
Section 5.2 below. This Agreement, including without limitation, the Schedule of
Purchasers, may be amended by the Company without the consent of the Purchasers
to include any Additional Purchasers. Any shares of the Company's Series D
Preferred Stock sold pursuant to this Section 2.3 shall be deemed to be "Shares"
for all purposes under this Agreement and any Additional Purchasers thereof
shall be deemed to be "Purchasers" for all purposes under this Agreement.

3. REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         Except as set forth on the Schedule of Exceptions, the Company hereby
represents and warrants to each Purchaser as of the First Closing as follows:

         3.1 ORGANIZATION, GOOD STANDING AND QUALIFICATION. The Company is a
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware. The Company has all requisite corporate power and
authority to own and operate its properties and assets, to execute and deliver
this Agreement, the Third Amended and Restated Investor Rights Agreement in the
form attached hereto as Exhibit C (the "INVESTOR RIGHTS AGREEMENT") and the
Third Amended Stockholders Agreement attached hereto as Exhibit D (the
"STOCKHOLDERS AGREEMENT") and the Regulatory Sideletter with J.P. Morgan
Partners (SBIC), LLC in the form attached hereto as Exhibit E (the "REGULATORY
SIDELETTER"), to issue and sell the Shares, the Conversion Shares, upon
conversion thereof, and to carry out the provisions of this Agreement, the
Investor Rights Agreement, the Stockholders Agreement and the Restated
Certificate and to carry on its business as presently conducted and as presently
proposed to be conducted. The Company is duly qualified and is authorized to do
business and is in good standing as a foreign corporation in Colorado and in all
jurisdictions in which the nature of its activities and of its properties (both
owned and leased) makes such qualification necessary, except for those
jurisdictions in which failure to do so would not have a material adverse effect

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on the Company or its business. The Company does not have any subsidiaries and
is not a participant in any joint venture, partnership or similar arrangement.

         3.2 CAPITALIZATION; VOTING RIGHTS. The authorized capital stock of the
Company, immediately prior to the First Closing, will consist of eighty-three
million (83,000,000) shares of Common Stock and sixty-five million four hundred
forty-five thousand (65,445,000) shares of Series Preferred. Four million four
hundred sixty-five thousand nine hundred ninety-eight (4,465,998) shares of
Common Stock are issued and outstanding. The Company has reserved twelve million
six hundred seventeen thousand three hundred twenty (12,617,320) shares of
Common Stock for issuance to employees, consultants and other service providers
pursuant to its 1998 Equity Incentive Plan (the "PLAN"). Seven hundred thirty
nine thousand five hundred thirty five (739,535) shares of the issued and
outstanding Common Stock are shares purchased pursuant to restricted stock
agreements under the Plan, and ninety-two thousand three (92,003) shares of the
issued and outstanding Common Stock are shares purchased pursuant to exercises
of options granted under the Plan. There are outstanding options or purchase
rights which have been issued to the Company's employees, consultants and other
service providers pursuant to the Plan to purchase up to one million seven
hundred thirteen thousand seven hundred eighty-four (1,713,784) shares of Common
Stock, and ten million seventy-one thousand nine hundred ninety-eight
(10,071,998) shares of Common Stock are reserved for options or purchase rights
which have not been granted as of the date hereof under the Plan. Six million
thirty-five thousand (6,035,000) shares of Series Preferred are designated
Series A Preferred Stock, six million thirty-five thousand (6,035,000) shares of
which are issued and outstanding. Eight hundred ten thousand (810,000) shares of
Series Preferred are designated Series B Preferred Stock, eight hundred three
thousand six hundred six (803,606) shares of which are issued and outstanding.
Thirteen million one hundred thousand (13,100,000) shares of Series Preferred
are designated Series C Preferred Stock, thirteen million ninety thousand nine
hundred ten (13,090,910) shares of which are issued and outstanding. Forty-five
million five hundred thousand (45,500,000) shares of Series Preferred are
designated Series D Preferred Stock, none of which are issued and outstanding.
All issued and outstanding shares of the Company's Common Stock, Series A
Preferred Stock, Series B Preferred Stock and Series C Preferred Stock (i) have
been duly authorized and validly issued to the persons listed on Exhibit F
hereto, (ii) are fully paid and nonassessable, and (iii) were issued in
compliance with all applicable state and federal laws concerning the issuance of
securities. The rights, preferences, privileges and restrictions of the Shares
are as stated in the Restated Certificate. The Conversion Shares have been duly
and validly reserved for issuance. Other than as set forth on Exhibit F, and
except as may be granted pursuant to the Investor Rights Agreement and the
Stockholders Agreement, there are no outstanding options, warrants, rights
(including conversion or preemptive rights and rights of first refusal), proxy
or shareholder agreements, or agreements of any kind for the purchase or
acquisition from the Company of any of its securities. Except for the Company's
right to repurchase shares of stock from its directors and employees pursuant to
certain restricted stock purchase agreements, agreements entered into pursuant
to the Plan and provisions contained in the Restated Certificate and Investor
Rights Agreement, there are no outstanding rights or obligations of the Company
to repurchase or redeem any of its securities. When issued in compliance with
the provisions of this Agreement and the Certificate, the Shares and the
Conversion Shares will be validly issued, fully paid and nonassessable, and will
be free of any liens or encumbrances; provided, however, that the Shares and the
Conversion Shares may be

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subject to restrictions on transfer under state and/or federal securities laws
as set forth herein or as otherwise required by such laws at the time a transfer
is proposed.

         3.3 AUTHORIZATION; BINDING OBLIGATIONS. All corporate actions on the
part of the Company, its officers, directors and stockholders necessary for the
authorization of this Agreement, the Investor Rights Agreement ,the Stockholders
Agreement and the Regulatory Sideletter, the performance of all obligations of
the Company hereunder and thereunder at the Closing and the authorization, sale,
issuance and delivery of the Shares pursuant hereto and the Conversion Shares
pursuant to the Restated Certificate has been taken or will be taken prior to
the Closing. The Agreement, the Investor Rights Agreement, the Stockholders
Agreement and the Regulatory Sideletter, when executed and delivered, will be
valid and binding obligations of the Company enforceable in accordance with
their terms, except (i) as limited by applicable bankruptcy, insolvency,
reorganization moratorium or other laws of general application affecting
enforcement of creditors' rights; (ii) general principles of equity that
restrict the availability of equitable remedies; and (iii) to the extent that
the enforceability of the indemnification provisions in Section 2.9 of the
Investor Rights Agreement may be limited by applicable laws. The sale of the
Shares and the subsequent conversion of Shares into Conversion Shares are not
and will not be subject to any preemptive rights or rights of first refusal that
have not been properly waived or complied with.

         3.4 FINANCIAL STATEMENTS. The Company has made available to each
Purchaser (a) its unaudited balance sheet as at December 31, 2000 and unaudited
statement of income and cash flows for the twelve (12) months ending December
31, 2000, and (b) its unaudited balance sheet as at June 30, 2001 (the
"Statement Date") and unaudited consolidated statement of income and cash flows
for the six (6) month period ending on the Statement Date (collectively, the
"Financial Statements"), copies of which are attached hereto as Exhibit G. The
Financial Statements, have been prepared in accordance with generally accepted
accounting principles applied on a consistent basis throughout the periods
indicated, except as disclosed therein, and present fairly the financial
condition and position of the Company as of December 31, 2000 and the Statement
Date; provided, however, that the Financial Statements are subject to normal
recurring year-end audit adjustments (which are not expected to be material),
and do not contain all footnotes required under generally accepted accounting
principles.

         3.5 LIABILITIES. The Company has no material liabilities and, to the
best of its knowledge, knows of no material contingent liabilities not disclosed
in the Financial Statements, except current liabilities incurred in the ordinary
course of business subsequent to the Statement Date, which have not been, either
in any individual case or in the aggregate, materially adverse to the financial
condition or operating results of the Company.

         3.6 AGREEMENTS; ACTION.

                  (a) Except for agreements explicitly contemplated hereby and
agreements between the Company and its employees with respect to the sale of the
Company's Common Stock and except as set forth on the Schedule of Exceptions,
there are no agreements, understandings or proposed transactions between the
Company and any of its officers, directors, affiliates or any affiliate thereof.

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                  (b) Except as set forth on the Schedule of Exceptions, there
are no agreements, understandings, instruments, contracts, proposed
transactions, judgments, orders, writs or decrees to which the Company is a
party or to its knowledge by which it is bound which may involve (i) obligations
(contingent or otherwise) of, or payments to, the Company in excess of $25,000
or (ii) the license of any patent, copyright, trade secret or other proprietary
right to or from the Company (other than licenses arising from the purchase of
"off the shelf" or other standard products), or (iii) provisions restricting or
affecting the development, manufacture, marketing, sale or distribution of the
Company's products or services, or (iv) indemnification by the Company with
respect to infringements of proprietary rights (other than indemnification
obligations arising from purchase or sale agreements entered into in the
ordinary course of business).

                  (c) Since the date of the Financial Statements, the Company
has not (i) declared or paid any dividends, or authorized or made any
distribution upon or with respect to any class or series of its capital stock,
(ii) incurred any indebtedness for money borrowed or any other liabilities
(other than with respect to dividend obligations, distributions, indebtedness
and other obligations incurred in the ordinary course of business or as
disclosed in the Balance Sheet) individually in excess of $25,000 or, in the
case of indebtedness and/or liabilities individually less than $25,000, in
excess of $50,000 in the aggregate, (iii) made any loans or advances to any
person, other than ordinary advances for travel and business expenses, or (iv)
sold, exchanged or otherwise disposed of any of its assets or rights, other than
the sale of its inventory in the ordinary course of business,

                  (d) For the purposes of subsections (b) and (c) above, all
indebtedness, liabilities, agreements, understandings, instruments, contracts
and proposed transactions involving the same person or entity (including persons
or entities the Company has reason to believe are affiliated therewith) shall be
aggregated for the purpose of meeting the individual minimum dollar amounts of
such subsections.

                  (e) Except as set forth on the Schedule of Exceptions, the
Company has not engaged in the past three months in any discussion (i) with any
representative of any corporation or corporations regarding the consolidation or
merger of the Company with or into any such corporation or corporations, (ii)
with any corporation, partnership, association or other business entity or any
individual regarding the sale, conveyance or disposition of all or substantially
all of the assets of the Company, or a transaction or series of related
transactions in which more than fifty percent (50%) of the voting power of the
Company is disposed of, or (iii) regarding any other form of acquisition,
liquidation, dissolution or winding up of the Company.

         3.7 OBLIGATIONS WITH RELATED PARTIES. Except as set forth on the
Schedule of Exceptions, there are no obligations of the Company to owners,
directors, stockholders, or employees of the Company other than (a) for payment
of salary for services rendered, (b) reimbursement for reasonable expenses
incurred on behalf of the Company and (c) for other standard employee benefits
made generally available to all employees (including stock option agreements
outstanding under any stock option plan approved by the Board of Directors of
the Company). None of the officers, directors or stockholders of the Company, or
any members of their immediate families, are indebted to the Company or have any
direct or indirect ownership interest in any firm or corporation with which the
Company is affiliated or with which the

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Company has a business relationship, or any firm or corporation which competes
with the Company (except as a holder of securities of a publicly traded company
to the extent of not more than two percent (2%) of the issued and outstanding
securities of such corporation). No officer, director or stockholder or any
member of their immediate families is, directly or indirectly, interested in any
material contract with the Company. Except as may be disclosed in the Financial
Statements, the Company is not a guarantor or indemnitor of any indebtedness of
any other person, firm or corporation.

         3.8 CHANGES. Since the Statement Date there has not been to the
Company's knowledge:

                  (a) Any change in the assets, liabilities, financial condition
or operations of the Company from that reflected in the Financial Statements,
other than changes in the ordinary course of business, none of which
individually or in the aggregate has had or is expected to have a material
adverse effect on such assets, liabilities, financial condition or operations of
the Company;

                  (b) Any resignation or termination of any officers or key
employee of the Company; and the Company does not know of the impending
resignation or termination of employment of any such officer or key employee;

                  (c) Any material change, except in the ordinary course of
business, in the contingent obligations of the Company by way of guaranty,
endorsement, indemnity, warranty or otherwise;

                  (d) Any damage, destruction or loss, whether or not covered by
insurance, materially and adversely affecting the properties, business or
prospects or financial condition of the Company;

                  (e) Any waiver by the Company of a valuable right or of a
material debt owed to it;

                  (f) Any direct or indirect loans made by the Company to any
stockholder, employee, officer or director of the Company, other than advances
made in the ordinary course of business;

                  (g) Any material change in any compensation arrangement or
agreement with any employee, officer, director or shareholder;

                  (h) Any declaration or payment of any dividend or other
distribution of the assets of the Company;

                  (i) Any labor organization activity;

                  (j) Any debt, obligation or liability incurred, assumed or
guaranteed by the Company, except for those immaterial amounts and for current
liabilities incurred in the ordinary course of business;

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                  (k) Any sale, assignment or transfer of any patents,
trademarks, copyrights, trade secrets or other intangible assets;

                  (l) Any change in any material agreement to which the Company
is a party or by which it is bound which materially and adversely affects the
business, assets, liabilities, financial condition, operations or prospects of
the Company, including compensation agreements with the Company's employees; or

                  (m) Any other event or condition of any character that, either
individually or cumulatively, has materially and adversely affected the
business, assets, liabilities, financial condition, operations or prospects of
the Company.

         3.9 TITLE TO PROPERTIES AND ASSETS; LIENS, ETC. The Company has good
and marketable title to its properties and assets, including the properties and
assets reflected in the Financial Statements and good title to its leasehold
estates, to the Company's knowledge, in each case subject to no mortgage,
pledge, lien, lease, encumbrance or charge, other than (i) those resulting from
taxes which have not yet become delinquent, (ii) minor liens and encumbrances
which do not materially detract from the value of the property subject thereto
or materially impair the operations of the Company, and (iii) those that have
otherwise arisen in the ordinary course of business. All Facilities, machinery,
equipment, fixtures, vehicles and other properties owned, leased or used by the
Company are in good operating condition and repair and are reasonably fit and
usable for the purposes for which they are being used.

         3.10 PATENTS AND TRADEMARKS. The Company owns or possesses sufficient
legal rights to all patents, trademarks, service marks, trade names, copyrights,
trade secrets, information and other proprietary rights and processes
("INTELLECTUAL PROPERTY") necessary for its business as now conducted and as
proposed to be conducted, without any known infringement of the rights of
others. Except as set forth on the Schedule of Exceptions, there are no
outstanding options, licenses or agreements of any kind relating to the
foregoing, nor is the Company bound by or a party to any options, licenses or
agreements of any kind with respect to the patents, trademarks, service marks,
trade names, copyrights, trade secrets, licenses, information and other
proprietary rights and processes of any other person or entity other than such
licenses or agreements arising from the purchase of "off the shelf" or standard
products. Except as set forth on the Schedule of Exceptions, at no time during
the conception or reduction to practice of any of the Company's Intellectual
Property was any developer, inventor or other contributor to such Intellectual
Property operating under any grants from any governmental entity or agency or
private source, performing research sponsored by any governmental entity or
agency or private source or subject to any employment agreement or invention
assignment or nondisclosure agreement or other obligation with any third party
that could adversely affect the Company's rights in such Intellectual Property.
Except as set forth on the Schedule of Exceptions, the Company is not obligated
to make any payments by the way of royalties, fees or otherwise to any owner or
licensor of any patent, trademark, trade name, copyright or other intangible
asset, with respect to the use thereof or in connection with the conduct of its
business, or otherwise. Except as set forth on the Schedule of Exceptions, the
Company has not granted to any third party any option, license or other right of
any kind to its Intellectual Property. Except as set forth on the Schedule of
Exceptions, the Company does not license any technology from any third party
other than for internal use. The Company has not received any communications

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alleging that the Company has violated or, by conducting its business as
proposed, would violate any of the patents, trademarks, service marks, trade
names, copyrights or trade secrets or other proprietary rights of any other
person or entity. The Company is not aware of any violation by a third party of
any of the Company's patents, trademarks, service marks, trade names,
copyrights, trade secrets, information or other proprietary rights and
processes. Except as set forth on the Schedule of Exceptions, the Company is not
aware that any of its officers, employees, consultants, contractors or
stockholders is obligated under any contract (including licenses, covenants or
commitments of any nature) or other agreement, or subject to any judgment,
decree or order of any court or administrative agency, that would interfere with
their duties to the Company or that would conflict with the Company's business
as proposed to be conducted or that would prevent such officers, employees,
consultants or contractors from assigning inventions to the Company. Neither the
execution nor delivery of this Agreement, nor the carrying on of the Company's
business by the employees or consultants of the Company, nor the conduct of the
Company's business as proposed, will, to the Company's knowledge, conflict with
or result in a breach of the terms, conditions or provisions of, or constitute a
default under, any contract, covenant or instrument under which any employee or
consultant is now obligated. The Company does not believe it is or will be
necessary to utilize any inventions, trade secrets or proprietary information of
any of its employees made prior to their employment by the Company, except for
inventions, trade secrets or proprietary information that have been assigned or
licensed to the Company.

         3.11 COMPLIANCE WITH OTHER INSTRUMENTS. The Company is not in violation
or default of any term of its Restated Certificate or Bylaws, or of any
provision of any mortgage, indenture, contract, agreement, instrument or
contract to which it is party or by which it is bound or of any judgment,
decree, order, writ or, to its knowledge, any statute, rule or regulation
applicable to the Company which would materially and adversely affect the
business, assets, liabilities, financial condition, operations or prospects of
the Company. The execution, delivery, and performance of and compliance with
this Agreement, the Investor Rights Agreement, the Stockholders Agreement and
the Regulatory Sideletter, and the issuance and sale of the Shares pursuant
hereto and of the Conversion Shares pursuant to the Restated Certificate, will
not result in any such material violation, or be in conflict with or constitute
a default under any such term, or result in the creation of any mortgage,
pledge, lien, encumbrance or charge upon any of the properties or assets of the
Company or the suspension, revocation impairment, forfeiture or nonrenewal of
any permit license, authorization or approval applicable to the Company, its
business or operations or any of its assets or properties or require notice to
or consent of any party to any material agreement to which the Company or its
property is bound.

         3.12 LITIGATION. There is no action, suit, proceeding or investigation
pending or to the Company's knowledge currently threatened against the Company
that questions the validity of this Agreement, the Investor Rights Agreement,
the Stockholders Agreement or the Regulatory Sideletter or the right of the
Company to enter into any of such agreements, or to consummate the transactions
contemplated hereby or thereby, or which might result, either individually or in
the aggregate, in any material adverse change in the assets, condition, affairs
or prospects of the Company, financially or otherwise, or any change in the
current equity ownership of the Company, nor is the Company aware that there is
any basis for the foregoing. The foregoing includes, without limitation, actions
pending or threatened (or any basis therefor known to the Company) involving the
prior employment of any of the Company's employees, their use in

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connection with the Company's business of any information or techniques
allegedly proprietary to any of their former employers, or their obligations
under any agreements with prior employers. The Company is not a party or subject
to the provisions of any order, writ, injunction, judgment or decree of any
court or government agency or instrumentality. There is no action, suit,
proceeding or investigation by the Company currently pending or which the
Company intends to initiate.

         3.13 TAX RETURNS AND PAYMENTS. The Company has filed all tax returns
and reports (federal, state and local) required to be filed by it. To the
Company's knowledge, there are no material misstatements or omissions of facts
in the tax returns and reports filed by the Company. All taxes shown to be due
and payable on such returns, any assessments imposed, and to the Company's
knowledge all other taxes due and payable by the Company on or before the
Closing have been paid or will be paid prior to the time they become delinquent.
The Company has not been advised (i) that any of its returns, federal, state or
other, have been or are being audited as of the date hereof, or (ii) of any
deficiency in assessment or proposed judgment to its federal, state or other
taxes. The Company has no knowledge of any liability of any tax to be imposed
upon its properties or assets as of the date of this Agreement that is not
adequately provided for. The Company has not elected pursuant to the Internal
Revenue Code of 1986, as amended (the "CODE"), to be treated as a Subchapter S
corporation or a collapsible corporation pursuant to Section 1362(a) or Section
341(f) of the Code, nor has it made any other elections pursuant to the Code
(other than elections that relate solely to methods of accounting, depreciation
or amortization) that would have a material effect on the business, properties
or condition (financial or otherwise) of the Company. The Company has withheld
or collected from each payment made to its employees the amount of all taxes
(including without limitation, federal income taxes, Federal Insurance
Contribution Act taxes and Federal Unemployment Tax Act taxes) required to be
withheld or collected therefrom, and has paid the same to the proper tax
receiving officers or authorized depositories.

         3.14 EMPLOYEES. The Company has no collective bargaining agreements
with any of its employees. There is no labor union organizing activity pending
or, to the Company's knowledge, threatened with respect to the Company. No
employee has any agreement or contract, written or verbal, regarding his
employment. To the Company's knowledge, no employee of the Company, nor any
consultant with whom the Company has contracted, is in violation of any term of
any employment contract, patent disclosure agreement or any other agreement
relating to the right of any such individual to be employed by, or to contract
with, the Company because of the nature of the business to be conducted by the
Company; and to the Company's knowledge the continued employment by the Company
of its present employees, and the performance of the Company's contracts with
its independent contractors, will not result in any such violation. The Company
has not received any notice alleging that any such violation has occurred. No
employee of the Company has been granted the right to continued employment by
the Company or to any material compensation following termination of employment
with the Company. The Company is not aware that any officer or key employee, or
that any group of key employees, intends to terminate their employment with the
Company, nor does the Company have a present intention to terminate the
employment of any officer, key employee or group of key employees. Each officer
and key employee is devoting 100% of his or her business time to the conduct of
the business of the Company. The Company does not have any Employee Benefit Plan
as defined in the Employee Retirement Income Security Act of 1974.

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         3.15 PROPRIETARY INFORMATION AND INVENTIONS AGREEMENTS. Each employee,
officer, consultant and contractor of the Company has executed either a
Proprietary Information and Inventions Agreement or a Consulting Agreement
substantially in the forms of Exhibit H-1 and Exhibit H-2 attached hereto. The
Company is not aware that any of its employees, officers, consultants or
contractors is in violation thereof.

         3.16 REGISTRATION RIGHTS. Except as required pursuant to the Investor
Rights Agreement and the Series B Preferred Stock Purchase Agreement, dated
March 16, 2000, and those persons and entities identified on Exhibit A thereto,
the Company is presently not under any obligation, and has not granted any
rights, to register (as defined in Section 1.2 of the Investor Rights Agreement)
any of the Company's presently outstanding securities or any of its securities
that may hereafter be issued.

         3.17 COMPLIANCE WITH LAWS; PERMITS. To its knowledge, the Company is
not in violation of any applicable statute, rule, regulation, order or
restriction of any domestic or foreign government or any instrumentality or
agency thereof in respect of the conduct of its business or the ownership of its
properties which violation would materially and adversely affect the business,
assets, liabilities, financial condition operations or prospects of the Company.
No governmental orders, permissions, consents, approvals or authorizations are
required to be obtained and no registrations or declarations are required to be
filed in connection with the execution and delivery of this Agreement and the
issuance of the Shares or the Conversion Shares, except such as has been duly
and validly obtained or filed, or with respect to any filings that must be made
after the Closing, which will be filed in a timely manner. The Company has all
franchises, permits, licenses and any similar authority necessary for the
conduct of its business as now being conducted by it, the lack of which could
materially and adversely affect the business, properties, prospects or financial
condition of the Company and believes it can obtain, without undue burden or
expense, any similar authority for the conduct of its business as planned to be
conducted. To the Company's knowledge, it is not in default in any material
respect under any of such franchises, permits, licenses or other similar
authority.

         3.18 ENVIRONMENTAL AND SAFETY LAWS. To its knowledge, the Company is
not in violation of any applicable statute, law or regulation relating to the
environment or occupational health and safety, and to its knowledge, no material
expenditures are or will be required in order to comply with any such existing
statute, law or regulation. No Hazardous Materials (as defined below) are used
or have been used, stored, or disposed of by the Company or, to the Company's
knowledge after reasonable investigation, by any other person or entity on any
property owned, leased or used by the Company. For the purposes of the preceding
sentence, "HAZARDOUS MATERIALS" shall mean (a) materials which are listed or
otherwise defined as "hazardous" or "toxic" under any applicable local, state,
federal and/or foreign laws and regulations that govern the existence and/or
remedy of contamination on property, the protection of the environment from
contamination, the control of hazardous wastes, or other activities involving
hazardous substances, including building materials or (b) any petroleum products
or nuclear materials.

         3.19 OFFERING VALID. Assuming the accuracy of the representations and
warranties of the Purchasers contained in Section 4.2 hereof, the offer, sale
and issuance of the Shares and the Conversion Shares will be exempt from the
registration requirements of the U.S. Securities Act of 1933, as amended (the
"SECURITIES ACT") and will have been registered or qualified (or are

                                       10
<PAGE>

exempt from registration and qualification) under the registration, permit or
qualification requirements of all applicable state securities laws. Neither the
Company nor any agent on its behalf has solicited or will solicit any offers to
sell or has offered to sell or will offer to sell all or any part of the Shares
to any person or persons so as to bring the sale of such Shares by the Company
within the registration provisions of the Securities Act. No consent, approval,
order or authorization of, or registration, qualification, designation,
declaration or filing with, any federal, state or local governmental authority
on the part of the Company is required in connection with the offer, sale or
issuance of the Shares (and the Common Stock issuable upon conversion of the
Shares) or the consummation of any other transactions contemplated by this
Agreement, except for (i) filings pursuant to Section 25102(f) of the California
Corporate Securities Law of 1968, as amended, and the rules thereunder, other
applicable state securities laws and Regulation D of the Securities Act, which
filings shall be effected within the requisite time periods, and (ii) the filing
of the Restated Certificate in the office of the Secretary of State of the State
of Delaware which shall be filed by the Company on or prior to the Closing.

         3.20 FULL DISCLOSURE. The Company has provided each Purchaser with all
information which such Purchaser has requested for deciding whether to purchase
the Shares and all information which the Company believes is reasonably
necessary to enable the Purchasers to make such decision. This Agreement, the
Exhibits hereto, the Investor Rights Agreement, the Stockholders Agreement and
all other documents delivered by the Company to Purchasers or their attorneys or
agents in connection herewith or therewith or with the transactions contemplated
hereby or thereby, do not contain any untrue statement of a material fact nor,
to the Company's knowledge, omit to state a material fact necessary in order to
make the statements contained herein or therein not misleading. To the Company's
knowledge, there are no facts which (individually or in the aggregate)
materially adversely affect the business, assets, liabilities, financial
condition, prospects or operations of the Company that have not been set forth
in the Agreement, the Exhibits hereto, or in other documents delivered to
Purchasers or their attorneys or agents in connection herewith.

         3.21 CORPORATE DOCUMENTS; MINUTE BOOKS. The Certificate and Bylaws of
the Company are in the form previously provided to special counsel to the
Purchasers. The minute books of the Company provided to the Purchaser's legal
counsel contain a complete set of minutes of all meetings of and records of all
actions taken by directors and stockholders since the time of incorporation.

         3.22 REAL PROPERTY HOLDING CORPORATION. The Company is not a real
property holding corporation within the meaning of Internal Revenue Code Section
897(c)(2) and any regulations promulgated thereunder.

         3.23 MANUFACTURING AND MARKETING RIGHTS. The Company has not granted
rights to manufacture, produce, assemble, license, market or sell its products
to any third party, and is not bound by any agreement that affects the Company's
exclusive right to develop, manufacture, assemble, distribute, market or sell
its products.

         3.24 VOTING AGREEMENTS. Except as set forth in the Schedule of
Exceptions, the Stockholders Agreement, the Restated Certificate or the
Investors Rights Agreement, the Company has no agreement, obligation or
commitment with respect to the election of any

                                       11
<PAGE>

individual or individuals to the Board of Directors, and to the best of the
Company's knowledge, there is no voting agreement or other arrangement among its
stockholders with respect to the election of any individual or individuals to
the Board of Directors.

         3.25 INSURANCE. The Company has in full force and effect fire and
casualty insurance policies and insurance against other hazards, risks and
liabilities to persons and property to the extent and in the manner customary
for companies in similar businesses similarly situated.

         3.26 DISTRIBUTIONS. There has been no declaration or payment by the
Company of any dividend, nor any distribution by the Company of any assets of
any kind, to any class or series of its capital stock.

         3.27 BROKERS OR FINDERS. No broker or finder is entitled to any
brokerage or other fee from the Company based upon arrangements made by or on
behalf of the Company in connection with the transactions contemplated by this
Agreement.

4. REPRESENTATIONS AND WARRANTIES OF THE PURCHASERS

         Each Purchaser hereby represents and warrants to the Company as follows
(such representations and warranties do not lessen or obviate the
representations and warranties of the Company set forth in this Agreement):

         4.1 REQUISITE POWER AND AUTHORITY. Purchaser has all necessary power
and authority under all applicable provisions of law to execute and deliver this
Agreement, the Investor Rights Agreement and the Stockholders Agreement and to
carry out their provisions. All action on Purchaser's part required for the
lawful execution and delivery of this Agreement, the Investor Rights Agreement
and the Stockholders Agreement have been or will be effectively taken prior to
the Closing. Upon their execution and delivery, this Agreement, the Investor
Rights Agreement and the Stockholders Agreement will be valid and binding
obligations of Purchaser, enforceable in accordance with their terms, except (i)
as limited by applicable bankruptcy, insolvency, reorganization, moratorium or
other laws of general application affecting enforcement of creditors' rights,
(ii) general principles of equity that restrict the availability of equitable
remedies, and (iii) to the extent that the enforceability of the indemnification
provisions of Section 2.9 of the Investor Rights Agreement may be limited by
applicable laws.

         4.2 INVESTMENT REPRESENTATIONS. Purchaser understands that neither the
Shares nor the Conversion Shares have been registered under the Securities Act.
Purchaser also understands that the Shares are being offered and sold pursuant
to an exemption from registration contained in the Securities Act based in part
upon Purchaser's representations contained in the Agreement. Purchaser hereby
represents and warrants as follows:

                  (a) PURCHASER BEARS ECONOMIC RISK. Purchaser has substantial
experience in evaluating and investing in private placement transactions of
securities in companies similar to the Company so that it is capable of
evaluating the merits and risks of its investment in the Company and has the
capacity to protect its own interests. Purchaser must bear the economic risk of
this investment indefinitely unless the Shares (or the Conversion Shares) are
registered pursuant to the Securities Act, or an exemption from registration is
available. Purchaser

                                       12
<PAGE>

understands that the Company has no present intention of registering the Shares,
the Conversion Shares or any shares of its Common Stock. Purchaser also
understands that there is no assurance that any exemption from registration
under the Securities Act will be available and that, even if available, such
exemption may not allow Purchaser to transfer all or any portion of the Shares
or the Conversion Shares under the circumstances, in the amounts or at the times
Purchaser might propose.

                 (b) ACQUISITION FOR OWN ACCOUNT. Purchaser is acquiring the
Shares and the Conversion Shares for Purchaser's own account for investment
only, and not with a view towards their distribution.

                 (c) PURCHASER CAN PROTECT ITS INTEREST. Purchaser represents
that by reason of its, or of its management's, business or financial experience,
Purchaser has the capacity to protect its own interests in connection with the
transactions contemplated in this Agreement, the Investor Rights Agreement and
the Stockholders Agreement. Further, Purchaser is aware of no publication of any
advertisement in connection with the transactions contemplated in the Agreement.

                 (d) ACCREDITED INVESTOR. Purchaser represents that it is an
accredited investor within the meaning of Regulation D under the Securities Act.

                 (e) COMPANY INFORMATION. Purchaser has received and read the
Financial Statements and has had an opportunity to discuss the Company's
business, management and financial affairs with directors, officers and
management of the Company and has had the opportunity to review the Company's
operations and facilities. Purchaser has also had the opportunity to ask
questions of and receive answers from, the Company and its management regarding
the terms and conditions of this investment.

                 (f) RULE 144. Purchaser acknowledges and agrees that the
Shares, and, if issued, the Conversion Shares must be held indefinitely unless
they are subsequently registered under the Securities Act or an exemption from
such registration is available. Purchaser has been advised or is aware of the
provisions of Rule 144 promulgated under the Securities Act, which permits
limited resale of shares purchased in a private placement subject to the
satisfaction of certain conditions, including, among other things, the
availability of certain current public information about the Company, the resale
occurring not less than one year after a party has purchased and paid for the
security to be sold, the sale being through an unsolicited brokers transaction
or in transactions directly with a market maker (as defined under the Securities
Exchange Act of 1934, as amended) and the number of shares being sold during any
three-month period not exceeding specified limitations.

         4.3 TRANSFER RESTRICTIONS. Each Purchaser acknowledges and agrees that
the Shares and, if issued, the Conversion Shares, are subject to restrictions on
transfer as set forth in the Investor Rights Agreement.

                                       13
<PAGE>

5. CONDITIONS TO CLOSING

         5.1 CONDITIONS TO PURCHASERS' OBLIGATIONS AT THE FIRST CLOSING.
Purchasers' obligations to purchase the Shares at the First Closing are subject
to the satisfaction, at or prior to the First Closing, of the following
conditions:

                  (a) REPRESENTATIONS AND WARRANTIES TRUE; PERFORMANCE OF
OBLIGATIONS. The representations and warranties made by the Company in Sections
3 and 6.13 hereof shall be true and correct in all material respects as of the
First Closing Date with the same force and effect as if they had been made as of
such First Closing Date, and the Company shall have performed and complied with
all agreements and conditions herein required to be performed or complied with
by it on or before the First Closing.

                  (b) LEGAL INVESTMENT. On the First Closing Date, the sale and
issuance of the Shares and the proposed issuance of the Conversion Shares shall
be legally permitted by all laws and regulations to which Purchasers and the
Company are subject.

                  (c) CONSENTS, PERMITS, AND WAIVERS. The Company shall have
obtained any and all consents, permits and waivers necessary or appropriate for
consummation of the transactions contemplated by the Agreement, the Investor
Rights Agreement and the Stockholders Agreement (except for such as may be
properly obtained subsequent to the First Closing).

                  (d) CORPORATE DOCUMENTS. The Company shall have delivered to
Purchasers or their counsel, copies of all corporate documents of the Company as
Purchasers shall reasonably request.

                  (e) COMPLIANCE CERTIFICATE. The Company shall have delivered
to Purchasers a Compliance Certificate, executed by the President of the
Company, dated the date of the First Closing, to the effect that the conditions
specified in subsections (a) through (l) of this Section 5.1 have been
satisfied. The Company shall have delivered to Purchasers a Secretary's
Certificate, executed by the Secretary of the Company, dated as of the First
Closing Date, in form and substance reasonably satisfactory to Purchasers.

                  (f) RESERVATION OF CONVERSION SHARES. The Conversion Shares
issuable upon conversion of the Shares shall have been duly authorized and
reserved for issuance upon such conversion.

                  (g) INVESTOR RIGHTS AGREEMENT. The Investor Rights Agreement
shall have been executed and delivered by the parties thereto.

                  (h) STOCKHOLDERS AGREEMENT. The Stockholders Agreement shall
have been executed and delivered by the parties thereto.

                  (i) BOARD OF DIRECTORS. Upon the First Closing, the authorized
size of the Board of Directors of the Company shall be eight (8) members as set
forth in the Stockholders Agreement, and Rodney Ferguson shall have been
appointed by the Board of Directors effective upon the First Closing.

                                       14
<PAGE>

                  (j) RESTATED CERTIFICATE. The Company shall have filed with
the Secretary of State of the State of Delaware the Restated Certificate, which
shall continue to be in full force and effect as of the First Closing Date.

                  (k) LEGAL OPINION. The Purchasers shall have received from
legal counsel to the Company an opinion addressed to them, dated as of the First
Closing, in substantially the form attached hereto as Exhibit I.

                  (l) PROCEEDINGS AND DOCUMENTS. All corporate and other
proceedings in connection with the transactions contemplated at the First
Closing hereby and all documents and instruments incident to such transactions
shall be reasonably satisfactory in substance and form to the Purchasers and
their special counsel and the Purchasers and their special counsel shall have
received all such counterpart originals or certified or other copies of such
documents as they may reasonably request.

                  (m) DUE DILIGENCE. The Purchasers shall (i) have completed
their due diligence of the Company, and (ii) be satisfied, in their sole
discretion, with the results of such due diligence review.

                  (o) REGULATORY SIDELETTER. The Company shall have executed and
delivered to J.P. Morgan Partners (SBIC), LLC the Regulatory Sideletter.

                  (p) SBA FORMS. The Company shall have delivered such
information and executed any documents or other instruments necessary for the
completion and filing of SBA Forms 480, 652 and 1031 and, to the extent
applicable, a Control Certification, no less than forty-eight (48) hours prior
to the First Closing.

                  (q) MINIMUM CLOSING AMOUNT. The aggregate purchase price to be
received by the Company at the First Closing shall be at least fifty million
dollars ($50,000,000).

         5.2 CONDITIONS TO PURCHASERS' OBLIGATIONS AT THE SECOND CLOSING.
Purchasers' obligations to purchase the Shares at the Second Closing are subject
to the satisfaction, at or prior to the Second Closing, of the following
conditions:

                  (a) LEGAL INVESTMENT. On the Second Closing Date, the sale and
issuance of the Shares and the proposed issuance of the Conversion Shares shall
be legally permitted by all laws and regulations to which Purchasers and the
Company are subject.

                  (b) COMPLIANCE CERTIFICATE. The Company shall have delivered
to Purchasers a Compliance Certificate, executed by the President of the
Company, dated the date of the Second Closing, to the effect that the conditions
specified in subsections (a) through (d) of this Section 5.2 have been
satisfied.

                  (c) LEGAL OPINION. The Purchasers shall have received from
legal counsel to the Company an opinion addressed to them, dated as of the
Second Closing, in substantially the form attached hereto as Exhibit I except
for such changes as may be required to update such opinion to the facts
concerning the Company or changes to applicable law which may occur prior to the
Second Closing.

                                       15
<PAGE>

                  (d) PROCEEDINGS AND DOCUMENTS. All corporate and other
proceedings in connection with the transactions contemplated at the Second
Closing hereby and all documents and instruments incident to such transactions
shall be reasonably satisfactory in substance and form to the Purchasers and
their special counsel and the Purchasers and their special counsel shall have
received all such counterpart originals or certified or other copies of such
documents as they may reasonably request.

        5.3 CONDITIONS TO OBLIGATIONS OF THE COMPANY. The Company's obligation
to issue and sell the Shares at each Closing is subject to the satisfaction, on
or prior to such Closing, of the following conditions:

                  (a) REPRESENTATIONS AND WARRANTIES TRUE. The representations
and warranties made by Purchasers in Sections 4 and 6.13 hereof shall be true
and correct in all material respects at the date of each Closing, with the same
force and effect as if they had been made on and as of said date.

                  (b) PERFORMANCE OF OBLIGATIONS. Purchasers shall have
performed and complied with all agreements and conditions herein required to be
performed or complied with by Purchasers on or before the Closing.

                  (c) INVESTOR RIGHTS AGREEMENT. The Investor Rights Agreement
shall have been executed and delivered by the Purchasers.

                  (d) STOCKHOLDERS AGREEMENT. The Stockholders Agreement shall
have been executed and delivered by the Purchasers

                  (e) CONSENTS, PERMITS, AND WAIVERS. The Company shall have
obtained any and all consents, permits and waivers necessary or appropriate for
consummation of the transactions contemplated by the Agreement, the Investor
Rights Agreement and the Stockholders Agreement (except for such as may be
properly obtained subsequent to the Closing).

6. MISCELLANEOUS

         6.1 GOVERNING LAW. This Agreement shall be governed in all respects by
the laws of the State of Colorado as such laws are applied to agreements between
Colorado residents entered into and performed entirely in Colorado.

         6.2 SURVIVAL. The representations, warranties, covenants and agreements
made herein shall survive the execution and delivery of this Agreement, any
investigation made by any Purchaser and each Closing. All statements as to
factual matters contained in any certificate or other instrument delivered by or
on behalf of the Company or the Purchasers pursuant hereto in connection with
the transactions contemplated hereby shall be deemed to be representations and
warranties by the Company or the Purchasers (as the case may be) hereunder
solely as of the date of such certificate or instrument.

         6.3 SUCCESSORS AND ASSIGNS. Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs,

                                       16
<PAGE>

executors and administrators of the parties hereto and shall inure to the
benefit of and be enforceable by each person who shall be a holder of the Shares
from time to time.

         6.4 ENTIRE AGREEMENT. This Agreement, the Exhibits and Schedules
hereto, the Investor Rights Agreement and the Stockholders Agreement and the
other documents delivered pursuant hereto constitute the full and entire
understanding and agreement between the parties with regard to the subjects
hereof and no party shall be liable or bound to any other in any manner by any
representations, warranties, covenants and agreements except as specifically set
forth herein and therein.

         6.5 SEVERABILITY. In case any provision of the Agreement shall be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby.

         6.6 AMENDMENT AND WAIVER.

                  (a) This Agreement may be amended or modified only upon the
written consent of the Company and holders of a majority of the Shares sold
pursuant to this Agreement (treated as if converted and including any Shares
issued upon the conversion of the Shares into Common Stock that have been
converted that have not been sold to the public).

                  (b) The obligations of the Company and the rights of the
holders of the Shares and the Conversion Shares under the Agreement may be
waived only with the written consent of the holders of a majority of the Shares
sold pursuant to this Agreement (treated as if converted and including any
Shares issued upon the conversion of the Shares into Common Stock that have not
been sold to the public).

         6.7 DELAYS OR OMISSIONS. It is agreed that no delay or omission to
exercise any right, power or remedy accruing to any party, upon any breach,
default or noncompliance by another party under this Agreement, the Investor
Rights Agreement and the Stockholders Agreement or the Restated Certificate,
shall impair any such right, power or remedy, nor shall it be construed to be a
waiver of any such breach, default or noncompliance, or any acquiescence
therein, or of or in any similar breach, default or noncompliance thereafter
occurring. It is further agreed that any waiver, permit, consent or approval of
any kind or character on any Purchaser's part of any breach, default or
noncompliance under this Agreement or under the Restated Certificate or any
waiver on such party's part of any provisions or conditions of the Agreement
must be in writing and shall be effective only to the extent specifically set
forth in such writing. All remedies, either under this Agreement, the Restated
Certificate, by-law, or otherwise afforded to any party, shall be cumulative and
not alternative.

         6.8 NOTICES. All notices required or permitted hereunder shall be in
writing and shall be deemed effectively given: (i) upon personal delivery to the
party to be notified; (ii) when sent by confirmed facsimile if sent during
normal business hours of the recipient, or if not, then on the next business
day; (iii) five (5) days after having been sent by registered or certified mail,
return receipt requested, postage prepaid; or (iv) one (1) day after deposit
with a nationally recognized overnight courier, specifying next day delivery,
with written verification of receipt. All communications shall be sent to the
Company at the address as set forth on the signature

                                       17
<PAGE>

page hereof and to Purchaser at the address set forth on Exhibit A attached
hereto or at such other address as the Company or Purchaser may designate by ten
(10) days advance written notice to the other parties hereto.

         6.9 EXPENSES. The Company shall pay all costs and expenses that it
incurs with respect to the negotiation, execution, delivery and performance of
the Agreement. The Company shall, at the First Closing, reimburse the reasonable
fees and expenses, not to exceed $50,000 in the aggregate, of Latham & Watkins,
special counsel for the Purchasers, Knobbe, Martens, Olson & Bear LLP, special
intellectual property counsel to the Purchasers, and consultants to the
Purchasers incurred in connection with the negotiation, execution, delivery and
performance of this Agreement.

         6.10 ATTORNEYS' FEES. In the event that any dispute among the parties
to this Agreement should result in litigation, the prevailing party in such
dispute shall be entitled to recover from the losing party all fees, costs and
expenses of enforcing any right of such prevailing party under or with respect
to this Agreement, including without limitation, such reasonable fees and
expenses of attorneys and accountants, which shall include, without limitation,
all fees, costs and expenses of appeals.

         6.11 TITLES AND SUBTITLES. The titles of the sections and subsections
of the Agreement are for convenience of reference only and are not to be
considered in construing this Agreement.

         6.12 COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

         6.13 BROKER'S FEES. Each party hereto represents and warrants that no
agent, broker, investment banker, person or firm acting on behalf of or under
the authority of such party hereto, other than J.P. Morgan Securities Inc., is
or will be entitled to any broker's or finder's fee or any other commission
directly or indirectly in connection with the transactions contemplated herein.
Each party hereto further agrees to indemnify each other party for any claims,
losses or expenses incurred by such other party as a result of the
representation in this Section 6.13 being untrue.

              [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK)

                                       18
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this SERIES D
PREFERRED STOCK PURCHASE AGREEMENT as of the date set forth in the first
paragraph hereof.

COMPANY                                       INVESTORS:

MYOGEN, INC.                                  J.P. MORGAN PARTNERS (SBIC), LLC

By: /s/ J. William Freytag                    By: /s/ Rodney A. Ferguson
   -----------------------                        ------------------------------
   J. William Freytag                         Name: Rodney A. Ferguson
   President                                        ----------------------------
                                              Title: Managing Director
                                                     ---------------------------

                                              NEW ENTERPRISE ASSOCIATES 10,
                                              LIMITED PARTNERSHIP

                                              By: NEA Partners 10, Limited
                                                  Partnership

                                              By: /s/ C. Richard Kramlich
                                                  ------------------------------
                                                  C. Richard Kramlich - General
                                                  Partner

                                              SEQUEL LIMITED PARTNERSHIP

                                              By: Sequel Venture Partners, LLC
                                                  its General Partner

                                              By: /s/ Dan Mitchell
                                                  ------------------------------
                                                  Manager

                                              INTERWEST PARTNERS VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                                              INTERWEST INVESTORS VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                              INTERWEST INVESTORS Q VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC, its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                                              NEW ENTERPRISE ASSOCIATES 9,
                                              LIMITED PARTNERSHIP

                                              By: NEA Partners 9, Limited
                                                  Partnership

                                              By: /s/ C. Richard Kramlich
                                                  ------------------------------
                                                  C. Richard Kramlich -
                                                  General Partner

                                              J.P. MORGAN SECURITIES INC.

                                              By: /s/ James F. Zanse
                                                  ------------------------------
                                              Name: James F. Zanse
                                                    ----------------------------
                                              Title:  Managing Director
                                                    ----------------------------

                                              BVCF IV, L.P.

                                              By: J.W. Puth Associates,
                                                  LLC, its General Partner

                                              By: Brinson Venture Management,
                                                  LLC, its Attorney-in-fact

                                              By: Adams Street Partners, LLC,
                                                  as its Administrative Member

                                              By: /s/ Terry Gould
                                                  ------------------------------
                                                  Terry Gould
                                                  Partner

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                              PACIFIC RIM LIFE SCIENCE NO. 1
                                              INVESTMENT PARTNERSHIP

                                              By: Pacific Rim Life Science
                                                  No. 1/2 Investment
                                                  Partnership, its general
                                                  partner

                                              By: /s/ Masahiro Michishita
                                                  ------------------------------
                                                  Masahiro Michishita, M.D.,
                                                  Ph.D., Managing General
                                                  Partner

                                              PACIFIC RIM LIFE SCIENCE NO. 2
                                              INVESTMENT PARTNERSHIP

                                              By: Pacific Rim Life Science
                                                  No. 1/2 Investment
                                                  Partnership, its general
                                                  partner

                                              By: /s/ Masahiro Michishita
                                                  ------------------------------
                                                  Masahiro Michishita, M.D.,
                                                  Ph.D., Managing General
                                                  Partner

                                              CMEA LIFE SCIENCES FUND, L.P.

                                              By: /s/ Thomas R. Baruch
                                                  ------------------------------
                                                  General Partner

                                              HFM CHARITABLE REMAINDER TRUST

                                              By: /s/ Roy M. Jones
                                                  ------------------------------
                                                  Roy M. Jones, Authorized Agent

                                              MONTAGU NEWHALL GLOBAL PARTNERS LP

                                              By: /s/ C. Ashton Newhall
                                                  ------------------------------

                                              Name: Ashton Newhall
                                                    ----------------------------

                                              Title: General Partner
                                                     ---------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                              /s/ David N. Low, Jr.
                                              ----------------------------------
                                              David N. Low, Jr.

                                              /s/ Jim F. Zanse
                                              ----------------------------------
                                              Jim F. Zanze

                                              /s/ Philippe McAuliffe
                                              ----------------------------------
                                              Philippe McAuliffe

                                              /s/ Mike Gaito
                                              ----------------------------------
                                              Mike Gaito

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                              CHINA DEVELOPMENT INDUSTRIAL
                                              BANK INC.

                                              By: /s/ Tai-ying Liu
                                                  ------------------------------
                                              Name: Tai-ying Liu
                                                    ----------------------------
                                              Title: Chairman and CEO
                                                     ---------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                              PERSEUS-SOROS BIOPHARMACEUTICAL
                                              FUND, LP

                                              By: Perseus-Soros Partners, LLC,
                                                  General Partner

                                                  By: SFM Participation, LP,
                                                      Member

                                                  By: SFM AH, Inc., General
                                                      Partner

                                                  /s/ Richard D. Holahan, Jr.
                                                  ------------------------------
                                                  By: Richard D. Holahan, Jr.
                                                  Title: Secretary

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                              HUNT VENTURES, L.P.

                                              By: /s/ Fulton Murray III
                                                  ------------------------------
                                              Name: J. Fulton Murray, III
                                                    ----------------------------
                                              Title: Managing Director
                                                     ---------------------------

                                              SILICON VALLEY BANCVENTURES, L.P.

                                              By: Silicon Valley BancVentures,
                                                  Inc., Its General Partner

                                              By: /s/ Greg Becker
                                                  ------------------------------
                                              Name: Greg Becker
                                                    ----------------------------
                                              Title: Investment Manager
                                                     ---------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                                  PACIFIC CAPITAL, LLC

                                                  /s/ T. Chester Wang
                                                  ------------------------------
                                                  T. Chester Wang

                                                  /s/ James Margolis
                                                  ------------------------------
                                                  James Margolis, MD

                                                  THOMAS J. TOY & CONSTANCE
                                                  K. TOY, JTWROS

                                                  /s/ Thomas J. Toy
                                                  ------------------------------
                                                  Thomas J. Toy

                                                  /s/ Constance K. Toy
                                                  ------------------------------
                                                  Constance K. Toy

                                                  /s/ Walter M. Narajowski
                                                  ------------------------------
                                                  Walter M. Narajowski

                                                  DIECK-MCGURK AND ASSOCIATES,
                                                  LP

                                                  By: /s/ Ronald Dieck
                                                      --------------------------
                                                  Ronald Dieck, General Partner

                                                  /s/ Daniel Rubin
                                                  ------------------------------
                                                  Daniel Ruben

                                                  /s/ David Pflueger
                                                  ------------------------------
                                                  David Pflueger

                                                  /s/ James Larrick
                                                  ------------------------------
                                                  James Larrick

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                    EXHIBIT A

                             SCHEDULE OF PURCHASERS

                                  FIRST CLOSING

<Table>
<Caption>
         NAME AND ADDRESS                                    SHARES              PRICE
         ----------------                                    ------              -----
<S>                                                     <C>                <C>
J.P. Morgan Partners (SBIC), LLC                        14,545,454         $19,999,999.25
50 California Street, Suite 2940
San Francisco, CA 94111
Attn:  Rod Ferguson

With a copy to:

J.P. Morgan Partners
Official Notices Clerk
1221 Avenue of the Americas
New York, NY 10020
Facsimile:  (212) 899-3401

and

J.P. Morgan Partners (SBIC), LLC
50 California Street, Suite 2940
San Francisco, CA 94111
Attn:  Shannon Horton

New Enterprise Associates 10, Limited Partnership        7,272,728         $10,000,001.00
1119 St. Paul Street
Baltimore, MD 21202
Attn:  Gene Trainor

Sequel Limited Partnership                                 290,909            $399,999.87
4430 Arapahoe Avenue, Suite 220
Boulder, CO 80303
Attn:  John Greff

InterWest Partners VIII, L.P.                            5,262,000          $7,235,250.00
3000 Sand Hill Road
Building 3, Suite 255
Menlo Park, CA 94025
Attn:  Arnold L. Oronsky

InterWest Investors VIII, L.P.                              42,000             $57,750.00
3000 Sand Hill Road
Building 3, Suite 255
Menlo Park, CA 94025
Attn:  Arnold L. Oronsky
</Table>

<PAGE>

<Table>
<Caption>
         NAME AND ADDRESS                                    SHARES              PRICE
         ----------------                                    ------              -----
<S>                                                     <C>                <C>
InterWest Investors Q VIII, L.P.                           150,546            $207,000.75
3000 Sand Hill Road
Building 3, Suite 255
Menlo Park, CA 94025
Attn:  Arnold L. Oronsky

New Enterprise Associates 9, Limited Partnership         6,181,819          $8,500,001.13
1119 St. Paul Street
Baltimore, MD 21202
Attn:  Gene Trainor

*J.P. Morgan Securities Inc.                               675,608
c/o Kathy Choi
225 Bush St., 4th Floor
San Francisco, CA 94104

BVCF IV, L.P.                                            2,181,819          $3,000,001.13
c/o Adam Street Partners, LLC
209 South LaSalle Street
Chicago, IL 60604
Attn:  Craig S. Taylor, Ph.D.

CMEA Life Sciences Fund, L.P.                              363,637            $500,000.87
One Embarcadero Center, Suite 3250
San Francisco, CA 94111
Attn:  Meryl L. Schreibstein

Pacific Rim Life Science No.1 Investment                   484,849            $666,667.37
Partnership
(C/O) Pacific Rim Ventures Co., Ltd.
2nd Floor, Green Plaza
3-7-20 Komazawa, Setagaya-ku
Tokyo 154-0012, Japan

Pacific Rim Life Science No.2 Investment                   242,424            $333,333.00
Partnership
(C/O) Pacific Rim Ventures Co., Ltd.
2nd Floor, Green Plaza
3-7-20 Komazawa, Setagaya-ku
Tokyo 154-0012, Japan

Both care of:
Daisuke Takahashi, Vice President, Pacific Rim
Ventures Co., Ltd.
2nd Floor, Green Plaza
3-7-20 Komazawa, Setagaya-ku
Tokyo 154-0012, Japan
TEL: 81-3-5779-6752
FAX: 81-3-5779-6753
dta@pacificrim-ventures.com
</Table>

                                       A-2

<PAGE>

<Table>
<Caption>
         NAME AND ADDRESS                                    SHARES              PRICE
         ----------------                                    ------              -----
<S>                                                     <C>                <C>
HFM Charitable Remainder Trust                             727,273          $1,000,000.30
3060 Peachtree Road NW
Nineteenth Floor
Atlanta, GA  30305
Attn: Roy M. Jones

Montagu Newhall Global Partners LP                         363,637            $500,000.87
52 Upper Brook Street
London W1K 2BU
Attention:  Rupert Montagu

David N. Low, Jr                                            18,182             $25,000.25
21 Deer Park Drive
Greenwich, CT 06831

Jim Zanze                                                    7,273             $10,000.38
2371 Broadway
San Francisco, CA. 94115

Philippe McAuliffe                                           5,819              $8,001.13
19 East 7th St., Apt. 4
New York, NY 10003

Mike Gaito                                                   3,636              $4,999.50
95 Horatio Street, Apt. 4C
New York, NY 10014

TOTAL:                                                  38,819,613         $52,448,006.80
</Table>

*Shares issued in exchange for past services.

                        SECOND CLOSING - NOVEMBER 2, 2001

<Table>
<Caption>
         NAME AND ADDRESS                                    SHARES              PRICE
         ----------------                                    ------              -----
<S>                                                     <C>                <C>
China Development Industrial Bank Inc.                   2,181,818          $2,999,999.75
125 Naking East Road Section 5
Overseas Business Department
Taipei, 105
Taiwan
Attn: Claire Tsai, Assistant Manager
</Table>

                                      A-3
<PAGE>

                        THIRD CLOSING - DECEMBER 27, 2001

<Table>
<Caption>
         NAME AND ADDRESS                                    SHARES              PRICE
         ----------------                                    ------              -----
<S>                                                     <C>                <C>
Perseus-Soros Biopharmaceutical Fund, LP                 5,818,181          $7,999,998.87
888 Seventh Avenue, 29th Floor
New York, NY  10106
Attn:  Steve Elms
       Andrew N. Schiff

with a copy to:

Perseus-Soros Biopharmaceutical Fund, L.P.
c/o Soros Fund Management LLC
888 Seventh Avenue, 31st Floor
New York, NY 10106
Attention:  Richard D. Holahan, Jr., Esq.

And

Paul, Weiss, Rifkind, Wharton & Garrison
1285 Avenue of the Americas
New York, New York 10019-6064
Attention: Bruce A. Gutenplan, Esq.

Hunt Ventures, L.P.                                      1,453,818          $1,998,999.75
Suite 1500
1445 Ross Avenue
Dallas, TX  75202
Attn:  Fulton Murray
       Tom Hurtekant, Esq.

Silicon Valley BancVentures L.P.                           545,454            $749,999.25
c/o
Silicon Valley BancVentures, Inc.
Attn:  Greg Becker
3000 Sand Hill Road
Building 1, Suite 200
Menlo Park, CA 94025

Pacific Rim Capital, LLC                                    36,363             $49,999.12
2150 California Street
Mountain View, CA  94040
Attn: T. Chester Wang

James Margolis, MD                                          36,363             $49,999.12
4701 Meridian Avenue
Suite 440, Adams Building
Miami Beach, FL 33140

Thomas J. Toy & Constance K. Toy, JTWROS                    18,181             $24,998.87
331 Parrott Drive
San Mateo, CA 94402
</Table>

                                       A-4

<PAGE>

<Table>
<Caption>
         NAME AND ADDRESS                                    SHARES              PRICE
         ----------------                                    ------              -----
<S>                                                     <C>                <C>
Walter M. Narajowski                                        18,181             $24,998.87
84 Blue Lagoon
Laguna Beach, CA 92651

Dieck-McGurk and Associates, LP                             18,181             $24,998.87
335 Lowell Avenue
Palo Alto, CA  94301
Attn:  Ron Dieck and Erin McGurk

Daniel Ruben                                                18,181             $24,998.87
15233 Camarillo St.
Sherman Oaks, CA 91403

David Pflueger                                              18,181             $24,998.87
Pluris Healthcare Systems
16596 W. Bayaud Dr.
Golden, CO 80401

James Larrick                                               18,181             $24,998.87
Panorama Research
2462 Wyandotte
Mt. View, CA 94043

TOTAL:                                                   7,999,265         $10,998,989.33
</Table>

                                       A-5
<PAGE>

                                    EXHIBIT B

                              RESTATED CERTIFICATE

                             [INTENTIONALLY OMITTED]

<PAGE>

                                    EXHIBIT C

              THIRD AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT

         Filed separately as Exhibit 10.8 to the Company's Registration
Statement on Form S-1.

<PAGE>

                                    EXHIBIT D

                THIRD AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

         Filed separately as Exhibit 10.9 to the Company's Registration
Statement on Form S-1.

<PAGE>

                                  MYOGEN, INC.

                             FIRST AMENDMENT TO THE
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

         Pursuant to Section 6.6 of the Series D Preferred Stock Purchase
Agreement, by and among Myogen, Inc. (the "Company") and the Purchasers listed
on Exhibit A thereto, dated as of August 21, 2001 (the "Agreement"), the Company
and each of the undersigned Purchasers hereby agree, effective as of this 26th
day of October, 2001 to the amendment (the "Amendment") set forth below.
Capitalized terms used but not defined herein have the meanings given them in
the Agreement.

                                    RECITALS

         A. The Company wishes to extend the period in which the Company may
sell the additional shares of Series D Preferred Stock pursuant to the Agreement
until December 31, 2001.

                                    AGREEMENT

                  The parties to the Agreement hereby agree as follows:

         1. Section 2.3 of the Agreement is hereby amended and restated to read
in its entirety as set forth below:

                  "2.3 SUBSEQUENT SALES OF SHARES. At any time on or before
         December 31, 2001 or at such time as the Company and the holders of a
         majority of the Shares purchased at the First Closing (pursuant to
         Section 2.1) may mutually agree, the Company may sell the balance of
         the Shares not sold at the First Closing to such persons as may be
         approved by the Board of Directors of the Company (the "ADDITIONAL
         PURCHASERS"). All such sales made at any additional closings (each a
         "SUBSEQUENT CLOSING"), (i) shall be made on the terms and conditions
         set forth in this Agreement, (ii) the representations and warranties of
         the Company set forth in Section 3 hereof (and the Schedule of
         Exceptions) shall speak as of the First Closing and the Company shall
         have no obligation to update any such disclosure, (iii) the
         representations and warranties of the Additional Purchasers in Section
         4 hereof shall speak as of such Subsequent Closing and (iv) the
         conditions of the Additional Purchasers' obligations at the Subsequent
         Closing shall be those set forth in Section 5.2 below. This Agreement,
         including without limitation, the Schedule of Purchasers, may be
         amended by the Company without the consent of the Purchasers to include
         any Additional Purchasers. Any shares of the Company's Series D
         Preferred Stock sold pursuant to this Section 2.3 shall be deemed to be
         "Shares" for all purposes under this Agreement and any Additional
         Purchasers thereof shall be deemed to be "Purchasers" for all purposes
         under this Agreement. All references to a Second Closing in the
         Agreement shall hereinafter refer to the Subsequent Closing. "

         2. This Amendment may be executed in any number of counterparts, each
of which may be executed by less than all of the parties hereto and each of
which shall constitute one and the same instrument.

         3. The undersigned Purchasers consent to a restatement of the Agreement
to incorporate this Amendment.

         4. This Amendment shall be effective upon its execution by the Company
and the holders of a majority of the Shares.

                                       1
<PAGE>

         5. The Amendment shall be governed and construed in accordance with the
laws of the State of Colorado as though made solely among residents of the State
of Colorado without regard to conflicts of law principals.

                       FIRST AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

                                       2
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this First
Amendment to the Series D Preferred Stock Purchase Agreement as of the date set
forth in the first paragraph above.

COMPANY                                       INVESTORS:

MYOGEN, INC.                                  J.P. MORGAN PARTNERS (SBIC), LLC

By: /s/ J. William Freytag                    By: /s/ Rodney A. Ferguson
   -----------------------                        ------------------------------
   J. William Freytag                         Name: Rodney A. Ferguson
   President                                  Title: Managing Director

                                              NEW ENTERPRISE ASSOCIATES 10,
                                              LIMITED PARTNERSHIP

                                              By: NEA Partners 10, Limited
                                                  Partnership

                                              By: /s/ C. Richard Kramlich
                                                  ------------------------------
                                                  C. Richard Kramlich, General
                                                  Partner

                                              SEQUEL LIMITED PARTNERSHIP

                                              By: Sequel Venture Partners, LLC
                                                  Its General Partner

                                              By: /s/ Dan Mitchell
                                                  ------------------------------
                                                  Manager

                                              INTERWEST PARTNERS VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                                              INTERWEST INVESTORS VII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                                              INTERWEST INVESTORS Q VIII, LP

                                              By:  InterWest Management Partners
                                                   VIII, LLC its general partner

                                              By:  /s/ Arnold Oronsky
                                                  ------------------------------

                       FIRST AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

<PAGE>

                                              NEW ENTERPRISE ASSOCIATES 9,
                                              LIMITED PARTNERSHIP

                                              By: NEA Partners 9, Limited
                                                  Partnership

                                              By: /s/ C. Richard Kramlich
                                                  ------------------------------
                                                  C. Richard Kramlich,
                                                  General Partner

                                              J.P. MORGAN SECURITIES INC.

                                              By: /s/ Rodney A. Ferguson
                                                  ------------------------------
                                              Name: Rodney A. Ferguson
                                              Title:  Managing Director

                                              BVCF IV, L.P.

                                              By: J.W. Puth Associates,
                                                  LLC, its General Partner

                                              By: Brinson Venture Management,
                                                  LLC, its Attorney-in-fact

                                              By: Adams Street Partners, LLC,
                                                  as its Administrative Member

                                              By: /s/ Terry Gould
                                                  ------------------------------
                                                  Terry Gould
                                                  Partner

                                              PACIFIC RIM LIFE SCIENCE NO. 1
                                              INVESTMENT PARTNERSHIP

                                              By: Pacific Rim Life Science
                                                  No. 1/2 Investment
                                                  Partnership, its general
                                                  partner

                                              By: /s/ Masahiro Michishita
                                                  ------------------------------
                                                  Masahiro Michishita, M.D.,
                                                  Ph.D., Managing General
                                                  Partner

                                              PACIFIC RIM LIFE SCIENCE NO. 2
                                              INVESTMENT PARTNERSHIP

                                              By: Pacific Rim Life Science
                                                  No. 1/2 Investment
                                                  Partnership, its general
                                                  partner

                                              By: /s/ Masahiro Michishita
                                                  ------------------------------
                                                  Masahiro Michishita, M.D.,
                                                  Ph.D., Managing General
                                                  Partner

                       FIRST AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

                                       2

<PAGE>

                                              CMEA LIFE SCIENCES FUND, L.P.

                                              By:
                                                  ------------------------------
                                                  General Partner

                                              HFM CHARITABLE REMAINDER TRUST

                                              By: /s/ Roy M. Jones
                                                  ------------------------------
                                                  Roy M. Jones, Authorized Agent

                                              MONTAGU NEWHALL GLOBAL PARTNERS LP

                                              By: /s/ C. Ashton Newhall
                                                  ------------------------------
                                              Name: Ashton Newhall
                                                    ----------------------------
                                              Title: General Partner
                                                     ---------------------------

                                              ----------------------------------
                                              David N. Low, Jr.

                                              /s/ James F. Zanse
                                              ----------------------------------
                                              Jim F. Zanze

                                              ----------------------------------
                                              Philippe McAuliffe

                                              /s/ Mike Gaito
                                              ----------------------------------
                                              Mike Gaito

                       FIRST AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

                                       3
<PAGE>

                                  MYOGEN, INC.

                             SECOND AMENDMENT TO THE
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

         Pursuant to Section 6.6 of the Series D Preferred Stock Purchase
Agreement, by and among Myogen, Inc. (the "Company") and the Purchasers listed
on Exhibit A thereto, dated as of August 21, 2001, as amended on October 26,
2001 (the "Agreement"), the Company and each of the undersigned Purchasers
hereby agree, effective as of this 20th day of December, 2001 to the amendment
(the "Amendment") set forth below. Capitalized terms used but not defined herein
have the meanings given them in the Agreement.

                                    RECITALS

                  A. The Company wishes to extend the period in which the
         Company may sell the additional shares of Series D Preferred Stock
         pursuant to the Agreement until February 15, 2002.

                  B. The Company wishes to increase the number of Shares of
         Series D Preferred Stock authorized for sale and issuance the Agreement
         to forty-nine million six hundred ninety-six (49,000,696) shares.

                                    AGREEMENT

                  The parties to the Agreement hereby agree as follows:

         1. The definition of "Shares" in the "Recitals" of the Agreement is
amended to refer to an aggregate of forty-nine million six hundred ninety-six
(49,000,696) shares of Series D Preferred Stock.

         2. Section 2.3 of the Agreement is hereby amended and restated to read
in its entirety as set forth below:

                  "2.3 SUBSEQUENT SALES OF SHARES. At any time on or before
         January 15, 2002 or at such time as the Company and the holders of a
         majority of the Shares purchased at the First Closing (pursuant to
         Section 2.1) may mutually agree, the Company may sell the balance of
         the Shares not sold at the First Closing to such persons as may be
         approved by the Board of Directors of the Company (the "ADDITIONAL
         PURCHASERS"). All such sales made at any additional closings after
         December 1, 2001 (each a "SUBSEQUENT CLOSING"), (i) shall be made on
         the terms and conditions set forth in this Agreement, (ii) the
         representations and warranties of the Company set forth in Section 3
         hereof (and the Schedule of Exceptions) shall speak as of the date of
         such Subsequent Closing, (iii) the representations and warranties of
         the Additional Purchasers in Section 4 hereof shall speak as of such
         Subsequent Closing and (iv) the conditions of the Additional
         Purchasers' obligations at the Subsequent Closing shall be those set
         forth in Section 5.2 below. This Agreement, including without
         limitation, the Schedule of Purchasers, may be amended by the Company
         without the consent of the Purchasers to include any Additional
         Purchasers. Any shares of the Company's Series D Preferred Stock sold
         pursuant to this Section 2.3 shall be deemed to be "Shares" for all
         purposes under this Agreement and any Additional Purchasers thereof
         shall be deemed to be "Purchasers" for all purposes under this
         Agreement. All references to a Second Closing in the Agreement shall
         hereinafter refer to the Subsequent Closing. "

         3. This Amendment may be executed in any number of counterparts, each
of which may be executed by less than all of the parties hereto and each of
which shall constitute one and the same instrument.

                                       1
<PAGE>

         4. The undersigned Purchasers consent to a restatement of the Agreement
to incorporate this Amendment.

         5. This Amendment shall be effective upon its execution by the Company
and the holders of a majority of the Shares.

         6. The Amendment shall be governed and construed in accordance with the
laws of the State of Colorado as though made solely among residents of the State
of Colorado without regard to conflicts of law principals.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                      SECOND AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

                                       2

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Second
Amendment to the Series D Preferred Stock Purchase Agreement as of the date set
forth in the first paragraph above.

COMPANY                                       INVESTORS:

MYOGEN, INC.                                  J.P. MORGAN PARTNERS (SBIC), LLC

By: /s/ J. William Freytag                    By: /s/ Rodney A. Ferguson
   -----------------------                        ------------------------------
   J. William Freytag                         Name: Rodney A. Ferguson
   President                                  Title: Managing Director

                                              NEW ENTERPRISE ASSOCIATES 10,
                                              LIMITED PARTNERSHIP

                                              By: NEA Partners 10, Limited
                                                  Partnership

                                              /s/ C. Richard Kramlich
                                              ----------------------------------
                                              C. Richard Kramlich, General
                                              Partner

                                              SEQUEL LIMITED PARTNERSHIP

                                              By: Sequel Venture Partners, LLC
                                                  Its General Partner

                                              By: /s/ Dan Mitchell
                                                  ------------------------------
                                                  Manager

                                              INTERWEST PARTNERS VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                                              INTERWEST INVESTORS VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                                              INTERWEST INVESTORS Q VIII, LP

                                              By: InterWest Management Partners
                                                  VIII, LLC its general partner

                                              By: /s/ Arnold Oronsky
                                                  ------------------------------

                      SECOND AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

<PAGE>
                                              NEW ENTERPRISE ASSOCIATES 9,
                                              LIMITED PARTNERSHIP

                                              By: NEA Partners 9, Limited
                                                  Partnership

                                              By: /s/ C. Richard Kramlich
                                                  ------------------------------
                                                  C. Richard Kramlich
                                                  General Partner

                                              J.P. MORGAN SECURITIES INC.

                                              By: /s/ James F. Zanse
                                                  ------------------------------
                                              Name: James F. Zanse
                                              Title: Managing Director

                                              BVCF IV, L.P.

                                              By: J.W. Puth Associates, LLC,
                                                  its General Partner

                                              By: Brinson Venture Management,
                                                  LLC, its Attorney-in-fact

                                              By: Adams Street Partners, LLC,
                                                  as its Administrative Member

                                              By: /s/ Craig S. Taylor
                                                  ------------------------------
                                                  Craig S. Taylor
                                                  Partner

                                              PACIFIC RIM LIFE SCIENCE NO. 1
                                              INVESTMENT PARTNERSHIP

                                              By: Pacific Rim Ventures Co,
                                                  Ltd., Managing Partner of
                                                  Pacific Rim Life Science
                                                  No. 1/2 Investment
                                                  Partnership

                                              By: /s/ Mashiro Michishita
                                                  ------------------------------
                                                  Mashiro Michishita, M.D.,
                                                  Ph.D., Managing General
                                                  Partner

                                              PACIFIC RIM LIFE SCIENCE NO. 2
                                              INVESTMENT PARTNERSHIP

                                              By: Pacific Rim Ventures Co,
                                                  Ltd., Managing Partner of
                                                  Pacific Rim Life Science
                                                  No. 1/2 Investment
                                                  Partnership

                                              By: /s/ Mashiro Michishita
                                                  ------------------------------
                                                  Mashiro Michishita, M.D.,
                                                  Ph.D., Managing General
                                                  Partner

                      SECOND AMENDMENT TO THE MYOGEN, INC.
                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

                                       2
<PAGE>

                                              CMEA LIFE SCIENCES FUND, L.P.

                                              By: /s/ Signature Illegible
                                                  ------------------------------
                                                  General Partner

                                              HFM CHARITABLE REMAINDER TRUST

                                              By:
                                                  ------------------------------
                                                  Roy M. Jones, Authorized Agent

                                              MONTAGU NEWHALL GLOBAL PARTNERS LP

                                              By: /s/ C. Ashton Newhall
                                                  ------------------------------
                                              Name: Ashton Newhall
                                              Title: General Partner

                                              ----------------------------------
                                              David N. Low, Jr.

                                              /s/ James F. Zanse
                                              ----------------------------------
                                              Jim F. Zanse

                                              ----------------------------------
                                              Philippe McAuliffe

                                              ----------------------------------
                                              Mike Gaito

                                              CHINA DEVELOPMENT INDUSTRIAL
                                              BANK INC.

                                              By:
                                                  ------------------------------
                                                  Name:
                                                        ------------------------
                                                  Title:
                                                         -----------------------

                       FIRST AMENDMENT TO THE MYOGEN, INC.
                THIRD AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

                                       3<PAGE>
                                                                    EXHIBIT 10.7

                                  MYOGEN, INC.

                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

         THIS SERIES D PREFERRED STOCK PURCHASE AGREEMENT (the "AGREEMENT") is
entered into as of this 27th day of August, 2003, by and among MYOGEN, INC., a
Delaware corporation (the "COMPANY") and each of those persons and entities,
severally and not jointly, whose names are set forth on the Schedule of
Purchasers attached hereto as EXHIBIT A (which persons and entities are
hereinafter collectively referred to as "PURCHASERS" and each individually as a
"PURCHASER").

                                    RECITALS

         WHEREAS, the Company has authorized the sale and issuance of up to an
aggregate of Twenty Nine Million Ninety Thousand Nine Hundred Nine (29,090,909)
additional shares of its Series D Preferred Stock (the "SHARES");

         WHEREAS, Purchasers desire to purchase the Shares on the terms and
conditions set forth herein; and

         WHEREAS, the Company desires to issue and sell the Shares to Purchasers
on the terms and conditions set forth herein;

         NOW, THEREFORE, in consideration of the foregoing recitals and the
mutual promises hereinafter set forth, the parties hereto agree as follows:

1. AGREEMENT TO SELL AND PURCHASE

         1.1 AUTHORIZATION OF SHARES. On or prior to the Closing (as defined in
Section 2 below), the Company shall have authorized (i) the sale and issuance to
Purchasers of the Shares having the rights, preferences, privileges and
restrictions set forth in the Restated Certificate of Incorporation of the
Company, as amended, in the form attached hereto as Exhibit B (the "RESTATED
CERTIFICATE") and (ii) the issuance of such shares of Common Stock to be issued
upon the conversion of the Shares (the "CONVERSION SHARES").

         1.2 SALE AND PURCHASE. Subject to the terms and conditions hereof, the
Company hereby agrees to issue and sell to each Purchaser and each Purchaser
agrees to purchase from the Company, the number of Shares set forth opposite
such Purchaser's name on Exhibit A at a purchase price of one dollar and
thirty-seven and one-half cents ($1.375) per share; provided that, with the
consent of the applicable Purchasers, the Company may reallocate the individual
amounts on Exhibit A among different Purchasers set forth on Exhibit A so long
as the total amount of the Shares is not increased above Twenty Nine Million
Ninety Thousand Nine Hundred Nine (29,090,909).

                                       1.
<PAGE>

2. CLOSING, DELIVERY AND PAYMENT

         2.1 CLOSING. The closing of the sale and purchase of the Shares under
this Agreement shall take place on the date hereof (the "CLOSING") at the
offices of Cooley Godward LLP, 380 Interlocken Crescent, Suite 900, Broomfield,
Colorado 80021 or at such other time or place as the Company and Purchasers may
mutually agree (such date is hereinafter referred to as a "CLOSING DATE").

         2.2 DELIVERY. At the Closing, subject to the terms and conditions
hereof, the Company will deliver to the Purchasers a certificate representing
the number of Shares to be purchased at the Closing by each Purchaser, against
payment of the purchase price therefor by certified check or wire transfer of
immediately available funds made payable to the Company, in exchange for
services previously rendered or any combination of the foregoing.

3. REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         Except as set forth on the Schedule of Exceptions, the Company hereby
represents and warrants to each Purchaser as of the Closing as follows:

         3.1 ORGANIZATION, GOOD STANDING AND QUALIFICATION. The Company is a
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware. The Company has all requisite corporate power and
authority to own and operate its properties and assets, to execute and deliver
this Agreement, the First Amendment in the form attached hereto as Exhibit C
(the "INVESTOR RIGHTS AGREEMENT AMENDMENT") to the Third Amended and Restated
Investor Rights Agreement dated as of August 21, 2001 (the "INVESTOR RIGHTS
AGREEMENT") and the Regulatory Sideletter with J.P. Morgan Partners (SBIC), LLC
in the form attached hereto as Exhibit D (the "REGULATORY SIDELETTER"), to issue
and sell the Shares, the Conversion Shares, upon conversion thereof, and to
carry out the provisions of this Agreement, the Investor Rights Agreement
Amendment and the Restated Certificate and to carry on its business as presently
conducted and as presently proposed to be conducted. The Company is duly
qualified and is authorized to do business and is in good standing as a foreign
corporation in Colorado and in all jurisdictions in which the nature of its
activities and of its properties (both owned and leased) makes such
qualification necessary, except for those jurisdictions in which failure to do
so would not have a material adverse effect on the Company or its business. The
Company does not have any subsidiaries and is not a participant in any joint
venture, partnership or similar arrangement.

         3.2 CAPITALIZATION; VOTING RIGHTS. The authorized capital stock of the
Company, immediately prior to the Closing, will consist of Two Hundred Twenty
Million Fifty Four Thousand Five Hundred Sixty-Five (220,054,565) shares of
Common Stock and One Hundred Twenty One Million One Hundred Nine Thousand Five
Hundred Sixty-Five (121,109,565) shares of Series Preferred. Five Million Two
Hundred Three Thousand Three Hundred Forty-Five (5,203,345) shares of Common
Stock are issued and outstanding. The Company has reserved Sixteen Million Six
Hundred Seventeen Thousand Three Hundred Twenty (16,617,320) shares of Common
Stock for issuance to employees, consultants and other service providers
pursuant to its 1998 Equity Incentive Plan (the "PLAN"). Seven Hundred Thirty
Nine Thousand Five Hundred Thirty-Five (739,535) shares of the issued and
outstanding Common Stock are

                                       2.
<PAGE>
 shares purchased pursuant to restricted stock agreements under the Plan, and
Six Hundred Fifty-Six Thousand One Hundred (656,100) shares of the issued and
outstanding Common Stock are shares purchased pursuant to exercises of options
granted under the Plan. There are outstanding options or purchase rights which
have been issued to the Company's employees, consultants and other service
providers pursuant to the Plan to purchase up to Ten Million Five Hundred
Thirty-Two Thousand Four Hundred Five (10,532,405) shares of Common Stock, Four
Million Six Hundred Eighty Nine Thousand Two Hundred Eighty (4,689,280) shares
of Common Stock are reserved for options or purchase rights which have not been
granted as of the date hereof under the Plan. Six million thirty-five thousand
(6,035,000) shares of Series Preferred are designated Series A Preferred Stock,
six million thirty-five thousand (6,035,000) shares of which are issued and
outstanding. Eight hundred ten thousand (810,000) shares of Series Preferred are
designated Series B Preferred Stock, eight hundred three thousand six hundred
six (803,606) shares of which are issued and outstanding. Thirteen million one
hundred thousand (13,100,000) shares of Series Preferred are designated Series C
Preferred Stock, thirteen million ninety thousand nine hundred ten (13,090,910)
shares of which are issued and outstanding. Seventy-Nine million (79,000,000)
shares of Series Preferred are designated Series D Preferred Stock, Forty Nine
Million Six Hundred Ninety-Six (49,000,696) shares of which are issued and
outstanding. All issued and outstanding shares of the Company's Common Stock,
Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and
Series D Preferred Stock (i) have been duly authorized and validly issued to the
persons listed on Exhibit E hereto, (ii) are fully paid and nonassessable, and
(iii) were issued in compliance with all applicable state and federal laws
concerning the issuance of securities. The rights, preferences, privileges and
restrictions of the Shares are as stated in the Restated Certificate. The
Conversion Shares have been duly and validly reserved for issuance. Other than
as set forth on Exhibit E, and except as may be granted pursuant to the Investor
Rights Agreement and the Third Amended and Restated Stockholders Agreement dated
as of August 21, 2001, as amended, (the "STOCKHOLDERS AGREEMENT") there are no
outstanding options, warrants, rights (including conversion or preemptive rights
and rights of first refusal), proxy or shareholder agreements, or agreements of
any kind for the purchase or acquisition from the Company of any of its
securities. Except for the Company's right to repurchase shares of stock from
its directors and employees pursuant to certain restricted stock purchase
agreements, agreements entered into pursuant to the Plan and provisions
contained in the Restated Certificate and Investor Rights Agreement, there are
no outstanding rights or obligations of the Company to repurchase or redeem any
of its securities. When issued in compliance with the provisions of this
Agreement and the Certificate, the Shares and the Conversion Shares will be
validly issued, fully paid and nonassessable, and will be free of any liens or
encumbrances; provided, however, that the Shares and the Conversion Shares may
be subject to restrictions on transfer under state and/or federal securities
laws as set forth herein or as otherwise required by such laws at the time a
transfer is proposed.

         3.3 AUTHORIZATION; BINDING OBLIGATIONS. All corporate actions on the
part of the Company, its officers, directors and stockholders necessary for the
authorization of this Agreement, the Investor Rights Agreement Amendment and the
Regulatory Sideletter, the performance of all obligations of the Company
hereunder and thereunder at the Closing and the authorization, sale, issuance
and delivery of the Shares pursuant hereto and the Conversion Shares pursuant to
the Restated Certificate has been taken or will be taken prior to the Closing.
The Agreement, the Investor Rights Agreement Amendment and the Regulatory
Sideletter, when executed and delivered, will be valid and binding obligations
of the Company enforceable in

                                       3.
<PAGE>

accordance with their terms, except (i) as limited by applicable bankruptcy,
insolvency, reorganization moratorium or other laws of general application
affecting enforcement of creditors' rights; (ii) general principles of equity
that restrict the availability of equitable remedies; and (iii) to the extent
that the enforceability of the indemnification provisions in Section 2.9 of the
Investor Rights Agreement Amendment may be limited by applicable laws. The sale
of the Shares and the subsequent conversion of Shares into Conversion Shares are
not and will not be subject to any preemptive rights or rights of first refusal
that have not been properly waived or complied with.

         3.4 FINANCIAL STATEMENTS. The Company has made available to each
Purchaser (a) its audited balance sheet as at December 31, 2002 and audited
statement of income and cash flows for the twelve (12) months ending December
31, 2002, and (b) its unaudited balance sheet as at June 30, 2003 (the
"Statement Date") and unaudited consolidated statement of income and cash flows
for the six (6) month period ending on the Statement Date (collectively, the
"Financial Statements"). The Financial Statements, have been prepared in
accordance with generally accepted accounting principles applied on a consistent
basis throughout the periods indicated, except as disclosed therein, and present
fairly the financial condition and position of the Company as of December 31,
2002 and the Statement Date; provided, however, that the Financial Statements
covering the six month period ending on the Statement Date are subject to normal
recurring year-end audit adjustments (which are not expected to be material),
and do not contain all footnotes required under generally accepted accounting
principles.

         3.5 LIABILITIES. The Company has no material liabilities and, to the
best of its knowledge, knows of no material contingent liabilities not disclosed
in the Financial Statements, except current liabilities incurred in the ordinary
course of business subsequent to the Statement Date, which have not been, either
in any individual case or in the aggregate, materially adverse to the financial
condition or operating results of the Company.

         3.6 AGREEMENTS; ACTION.

                  (a) Except for agreements explicitly contemplated hereby and
agreements between the Company and its employees with respect to the sale of the
Company's Common Stock and except as set forth on the Schedule of Exceptions,
there are no agreements, understandings or proposed transactions between the
Company and any of its officers, directors, affiliates or any affiliate thereof.

                  (b) Except as set forth on the Schedule of Exceptions, there
are no agreements, understandings, instruments, contracts, proposed
transactions, judgments, orders, writs or decrees to which the Company is a
party or to its knowledge by which it is bound which may involve (i) obligations
(contingent or otherwise) of, or payments to, the Company in excess of $50,000
or (ii) the license of any patent, copyright, trade secret or other proprietary
right to or from the Company (other than licenses arising from the purchase of
"off the shelf" or other standard products), or (iii) provisions restricting or
affecting the development, manufacture, marketing, sale or distribution of the
Company's products or services, or (iv) indemnification by the Company with
respect to infringements of proprietary rights (other than indemnification
obligations arising from purchase or sale agreements entered into in the
ordinary course of business).

                                       4.
<PAGE>

                  (c) Since the date of the Financial Statements, the Company
has not (i) declared or paid any dividends, or authorized or made any
distribution upon or with respect to any class or series of its capital stock,
(ii) incurred any indebtedness for money borrowed or any other liabilities
(other than with respect to dividend obligations, distributions, indebtedness
and other obligations incurred in the ordinary course of business or as
disclosed in the Balance Sheet) individually in excess of $50,000 or, in the
case of indebtedness and/or liabilities individually less than $50,000, in
excess of $100,000 in the aggregate, (iii) made any loans or advances to any
person, other than ordinary advances for travel and business expenses, or (iv)
sold, exchanged or otherwise disposed of any of its assets or rights, other than
the sale of its inventory in the ordinary course of business.

                  (d) For the purposes of subsections (b) and (c) above, all
indebtedness, liabilities, agreements, understandings, instruments, contracts
and proposed transactions involving the same person or entity (including persons
or entities the Company has reason to believe are affiliated therewith) shall be
aggregated for the purpose of meeting the individual minimum dollar amounts of
such subsections.

                  (e) Except as set forth on the Schedule of Exceptions, the
Company has not engaged in the past three months in any discussion (i) with any
representative of any corporation or corporations regarding the consolidation or
merger of the Company with or into any such corporation or corporations, (ii)
with any corporation, partnership, association or other business entity or any
individual regarding the sale, conveyance or disposition of all or substantially
all of the assets of the Company, or a transaction or series of related
transactions in which more than fifty percent (50%) of the voting power of the
Company is disposed of, or (iii) regarding any other form of acquisition,
liquidation, dissolution or winding up of the Company.

         3.7 OBLIGATIONS WITH RELATED PARTIES. Except as set forth on the
Schedule of Exceptions, there are no obligations of the Company to owners,
directors, stockholders, or employees of the Company other than (a) for payment
of salary for services rendered, (b) reimbursement for reasonable expenses
incurred on behalf of the Company and (c) for other standard employee benefits
made generally available to all employees (including stock option agreements
outstanding under any stock option plan approved by the Board of Directors of
the Company). None of the officers, directors or stockholders of the Company, or
any members of their immediate families, are indebted to the Company or have any
direct or indirect ownership interest in any firm or corporation with which the
Company is affiliated or with which the Company has a business relationship, or
any firm or corporation which competes with the Company (except as a holder of
securities of a publicly traded company to the extent of not more than two
percent (2%) of the issued and outstanding securities of such corporation). No
officer, director or stockholder or any member of their immediate families is,
directly or indirectly, interested in any material contract with the Company.
Except as may be disclosed in the Financial Statements, the Company is not a
guarantor or indemnitor of any indebtedness of any other person, firm or
corporation.

                                       5.
<PAGE>

         3.8 CHANGES. Since the Statement Date there has not been to the
Company's knowledge:

                  (a) Any change in the assets, liabilities, financial condition
or operations of the Company from that reflected in the Financial Statements,
other than changes in the ordinary course of business, none of which
individually or in the aggregate has had or is expected to have a material
adverse effect on such assets, liabilities, financial condition or operations of
the Company;

                  (b) Any resignation or termination of any officers or key
employee of the Company; and the Company does not know of the impending
resignation or termination of employment of any such officer or key employee;

                  (c) Any material change, except in the ordinary course of
business, in the contingent obligations of the Company by way of guaranty,
endorsement, indemnity, warranty or otherwise;

                  (d) Any damage, destruction or loss, whether or not covered by
insurance, materially and adversely affecting the properties, business or
prospects or financial condition of the Company;

                  (e) Any waiver by the Company of a valuable right or of a
material debt owed to it;

                  (f) Any direct or indirect loans made by the Company to any
stockholder, employee, officer or director of the Company, other than advances
made in the ordinary course of business;

                  (g) Any material change in any compensation arrangement or
agreement with any employee, officer, director or shareholder;

                  (h) Any declaration or payment of any dividend or other
distribution of the assets of the Company;

                  (i) Any labor organization activity;

                  (j) Any debt, obligation or liability incurred, assumed or
guaranteed by the Company, except for those immaterial amounts and for current
liabilities incurred in the ordinary course of business;

                  (k) Any sale, assignment or transfer of any patents,
trademarks, copyrights, trade secrets or other intangible assets;

                  (l) Any change in any material agreement to which the Company
is a party or by which it is bound which materially and adversely affects the
business, assets, liabilities, financial condition, operations or prospects of
the Company, including compensation agreements with the Company's employees; or

                                       6.
<PAGE>

                  (m) Any other event or condition of any character that, either
individually or cumulatively, has materially and adversely affected the
business, assets, liabilities, financial condition, operations or prospects of
the Company.

         3.9 TITLE TO PROPERTIES AND ASSETS; LIENS, ETC. The Company has good
and marketable title to its properties and assets, including the properties and
assets reflected in the Financial Statements and good title to its leasehold
estates, to the Company's knowledge, in each case subject to no mortgage,
pledge, lien, lease, encumbrance or charge, other than (i) those resulting from
taxes which have not yet become delinquent, (ii) minor liens and encumbrances
which do not materially detract from the value of the property subject thereto
or materially impair the operations of the Company, and (iii) those that have
otherwise arisen in the ordinary course of business. All Facilities, machinery,
equipment, fixtures, vehicles and other properties owned, leased or used by the
Company are in good operating condition and repair and are reasonably fit and
usable for the purposes for which they are being used.

         3.10 PATENTS AND TRADEMARKS. The Company owns or possesses sufficient
legal rights to all patents, trademarks, service marks, trade names, copyrights,
trade secrets, information and other proprietary rights and processes
("INTELLECTUAL PROPERTY") necessary for its business as now conducted and as
proposed to be conducted, without any known infringement of the rights of
others. Except as set forth on the Schedule of Exceptions, there are no
outstanding options, licenses or agreements of any kind relating to the
foregoing, nor is the Company bound by or a party to any options, licenses or
agreements of any kind with respect to the patents, trademarks, service marks,
trade names, copyrights, trade secrets, licenses, information and other
proprietary rights and processes of any other person or entity other than such
licenses or agreements arising from the purchase of "off the shelf" or standard
products. Except as set forth on the Schedule of Exceptions, at no time during
the conception or reduction to practice of any of the Company's Intellectual
Property was any developer, inventor or other contributor to such Intellectual
Property operating under any grants from any governmental entity or agency or
private source, performing research sponsored by any governmental entity or
agency or private source or subject to any employment agreement or invention
assignment or nondisclosure agreement or other obligation with any third party
that could adversely affect the Company's rights in such Intellectual Property.
Except as set forth on the Schedule of Exceptions, the Company is not obligated
to make any payments by the way of royalties, fees or otherwise to any owner or
licensor of any patent, trademark, trade name, copyright or other intangible
asset, with respect to the use thereof or in connection with the conduct of its
business, or otherwise. Except as set forth on the Schedule of Exceptions, the
Company has not granted to any third party any option, license or other right of
any kind to its Intellectual Property. Except as set forth on the Schedule of
Exceptions, the Company does not license any technology from any third party
other than for internal use. The Company has not received any communications
alleging that the Company has violated or, by conducting its business as
proposed, would violate any of the patents, trademarks, service marks, trade
names, copyrights or trade secrets or other proprietary rights of any other
person or entity. The Company is not aware of any violation by a third party of
any of the Company's patents, trademarks, service marks, trade names,
copyrights, trade secrets, information or other proprietary rights and
processes. Except as set forth on the Schedule of Exceptions, the Company is not
aware that any of its officers, employees, consultants, contractors or
stockholders is obligated under any contract (including licenses, covenants or
commitments of any nature) or other agreement, or subject to any judgment,
decree

                                       7.
<PAGE>

or order of any court or administrative agency, that would interfere with their
duties to the Company or that would conflict with the Company's business as
proposed to be conducted or that would prevent such officers, employees,
consultants or contractors from assigning inventions to the Company. Neither the
execution nor delivery of this Agreement, nor the carrying on of the Company's
business by the employees or consultants of the Company, nor the conduct of the
Company's business as proposed, will, to the Company's knowledge, conflict with
or result in a breach of the terms, conditions or provisions of, or constitute a
default under, any contract, covenant or instrument under which any employee or
consultant is now obligated. The Company does not believe it is or will be
necessary to utilize any inventions, trade secrets or proprietary information of
any of its employees made prior to their employment by the Company, except for
inventions, trade secrets or proprietary information that have been assigned or
licensed to the Company.

         3.11 COMPLIANCE WITH OTHER INSTRUMENTS. The Company is not in violation
or default of any term of its Restated Certificate or Bylaws, or of any
provision of any mortgage, indenture, contract, agreement, instrument or
contract to which it is party or by which it is bound or of any judgment,
decree, order, writ or, to its knowledge, any statute, rule or regulation
applicable to the Company which would materially and adversely affect the
business, assets, liabilities, financial condition, operations or prospects of
the Company. The execution, delivery, and performance of and compliance with
this Agreement, the Investor Rights Agreement Amendment and the Regulatory
Sideletter, and the issuance and sale of the Shares pursuant hereto and of the
Conversion Shares pursuant to the Restated Certificate, will not result in any
such material violation, or be in conflict with or constitute a default under
any such term, or result in the creation of any mortgage, pledge, lien,
encumbrance or charge upon any of the properties or assets of the Company or the
suspension, revocation impairment, forfeiture or nonrenewal of any permit
license, authorization or approval applicable to the Company, its business or
operations or any of its assets or properties or require notice to or consent of
any party to any material agreement to which the Company or its property is
bound.

         3.12 LITIGATION. There is no action, suit, proceeding or investigation
pending or to the Company's knowledge currently threatened against the Company
that questions the validity of this Agreement, the Investor Rights Agreement
Amendment or the Regulatory Sideletter or the right of the Company to enter into
any of such agreements, or to consummate the transactions contemplated hereby or
thereby, or which might result, either individually or in the aggregate, in any
material adverse change in the assets, condition, affairs or prospects of the
Company, financially or otherwise, or any change in the current equity ownership
of the Company, nor is the Company aware that there is any basis for the
foregoing. The foregoing includes, without limitation, actions pending or
threatened (or any basis therefor known to the Company) involving the prior
employment of any of the Company's employees, their use in connection with the
Company's business of any information or techniques allegedly proprietary to any
of their former employers, or their obligations under any agreements with prior
employers. The Company is not a party or subject to the provisions of any order,
writ, injunction, judgment or decree of any court or government agency or
instrumentality. There is no action, suit, proceeding or investigation by the
Company currently pending or which the Company intends to initiate.

                                       8.
<PAGE>

         3.13 TAX RETURNS AND PAYMENTS. The Company has filed all tax returns
and reports (federal, state and local) required to be filed by it. To the
Company's knowledge, there are no material misstatements or omissions of facts
in the tax returns and reports filed by the Company. All taxes shown to be due
and payable on such returns, any assessments imposed, and to the Company's
knowledge all other taxes due and payable by the Company on or before the
Closing have been paid or will be paid prior to the time they become delinquent.
The Company has not been advised (i) that any of its returns, federal, state or
other, have been or are being audited as of the date hereof, or (ii) of any
deficiency in assessment or proposed judgment to its federal, state or other
taxes. The Company has no knowledge of any liability of any tax to be imposed
upon its properties or assets as of the date of this Agreement that is not
adequately provided for. The Company has not elected pursuant to the Internal
Revenue Code of 1986, as amended (the "CODE"), to be treated as a Subchapter S
corporation or a collapsible corporation pursuant to Section 1362(a) or Section
341(f) of the Code, nor has it made any other elections pursuant to the Code
(other than elections that relate solely to methods of accounting, depreciation
or amortization) that would have a material effect on the business, properties
or condition (financial or otherwise) of the Company. The Company has withheld
or collected from each payment made to its employees the amount of all taxes
(including without limitation, federal income taxes, Federal Insurance
Contribution Act taxes and Federal Unemployment Tax Act taxes) required to be
withheld or collected therefrom, and has paid the same to the proper tax
receiving officers or authorized depositories.

         3.14 EMPLOYEES. The Company has no collective bargaining agreements
with any of its employees. There is no labor union organizing activity pending
or, to the Company's knowledge, threatened with respect to the Company. No
employee has any agreement or contract, written or verbal, regarding his
employment. To the Company's knowledge, no employee of the Company, nor any
consultant with whom the Company has contracted, is in violation of any term of
any employment contract, patent disclosure agreement or any other agreement
relating to the right of any such individual to be employed by, or to contract
with, the Company because of the nature of the business to be conducted by the
Company; and to the Company's knowledge the continued employment by the Company
of its present employees, and the performance of the Company's contracts with
its independent contractors, will not result in any such violation. The Company
has not received any notice alleging that any such violation has occurred. No
employee of the Company has been granted the right to continued employment by
the Company or to any material compensation following termination of employment
with the Company. The Company is not aware that any officer or key employee, or
that any group of key employees, intends to terminate their employment with the
Company, nor does the Company have a present intention to terminate the
employment of any officer, key employee or group of key employees. Each officer
and key employee is devoting 100% of his or her business time to the conduct of
the business of the Company. The Company does not have any Employee Benefit Plan
as defined in the Employee Retirement Income Security Act of 1974.

         3.15 PROPRIETARY INFORMATION AND INVENTIONS AGREEMENTS. Each employee,
officer, consultant and contractor of the Company has executed either a
Proprietary Information and Inventions Agreement or a Consulting Agreement
substantially in the forms of Exhibit F-1 and Exhibit F-2 attached hereto. The
Company is not aware that any of its employees, officers, consultants or
contractors is in violation thereof.

                                       9.
<PAGE>

         3.16 REGISTRATION RIGHTS. Except as required pursuant to the Investor
Rights Agreement Amendment and the Series B Preferred Stock Purchase Agreement,
dated March 16, 2000, and those persons and entities identified on Exhibit A
thereto, the Company is presently not under any obligation, and has not granted
any rights, to register (as defined in Section 1.2 of the Investor Rights
Agreement Amendment) any of the Company's presently outstanding securities or
any of its securities that may hereafter be issued.

         3.17 COMPLIANCE WITH LAWS; PERMITS. To its knowledge, the Company is
not in violation of any applicable statute, rule, regulation, order or
restriction of any domestic or foreign government or any instrumentality or
agency thereof in respect of the conduct of its business or the ownership of its
properties which violation would materially and adversely affect the business,
assets, liabilities, financial condition operations or prospects of the Company.
No governmental orders, permissions, consents, approvals or authorizations are
required to be obtained and no registrations or declarations are required to be
filed in connection with the execution and delivery of this Agreement and the
issuance of the Shares or the Conversion Shares, except such as has been duly
and validly obtained or filed, or with respect to any filings that must be made
after the Closing, which will be filed in a timely manner. The Company has all
franchises, permits, licenses and any similar authority necessary for the
conduct of its business as now being conducted by it, the lack of which could
materially and adversely affect the business, properties, prospects or financial
condition of the Company and believes it can obtain, without undue burden or
expense, any similar authority for the conduct of its business as planned to be
conducted. To the Company's knowledge, it is not in default in any material
respect under any of such franchises, permits, licenses or other similar
authority.

         3.18 ENVIRONMENTAL AND SAFETY LAWS. To its knowledge, the Company is
not in violation of any applicable statute, law or regulation relating to the
environment or occupational health and safety, and to its knowledge, no material
expenditures are or will be required in order to comply with any such existing
statute, law or regulation. No Hazardous Materials (as defined below) are used
or have been used, stored, or disposed of by the Company or, to the Company's
knowledge after reasonable investigation, by any other person or entity on any
property owned, leased or used by the Company. For the purposes of the preceding
sentence, "HAZARDOUS MATERIALS" shall mean (a) materials which are listed or
otherwise defined as "hazardous" or "toxic" under any applicable local, state,
federal and/or foreign laws and regulations that govern the existence and/or
remedy of contamination on property, the protection of the environment from
contamination, the control of hazardous wastes, or other activities involving
hazardous substances, including building materials or (b) any petroleum products
or nuclear materials.

         3.19 OFFERING VALID. Assuming the accuracy of the representations and
warranties of the Purchasers contained in Section 4.2 hereof, the offer, sale
and issuance of the Shares and the Conversion Shares will be exempt from the
registration requirements of the U.S. Securities Act of 1933, as amended (the
"SECURITIES ACT") and will have been registered or qualified (or are exempt from
registration and qualification) under the registration, permit or qualification
requirements of all applicable state securities laws. Neither the Company nor
any agent on its behalf has solicited or will solicit any offers to sell or has
offered to sell or will offer to sell all or any part of the Shares to any
person or persons so as to bring the sale of such Shares by the Company within
the registration provisions of the Securities Act. No consent, approval, order
or authorization of, or registration, qualification, designation, declaration or
filing with, any federal,

                                      10.
<PAGE>

state or local governmental authority on the part of the Company is required in
connection with the offer, sale or issuance of the Shares (and the Common Stock
issuable upon conversion of the Shares) or the consummation of any other
transactions contemplated by this Agreement, except for (i) filings pursuant to
Section 25102(f) of the California Corporate Securities Law of 1968, as amended,
and the rules thereunder, other applicable state securities laws and Regulation
D of the Securities Act, which filings shall be effected within the requisite
time periods, and (ii) the filing of the Restated Certificate in the office of
the Secretary of State of the State of Delaware which shall be filed by the
Company on or prior to the Closing.

         3.20 FULL DISCLOSURE. The Company has provided each Purchaser with all
information which such Purchaser has requested for deciding whether to purchase
the Shares and all information which the Company believes is reasonably
necessary to enable the Purchasers to make such decision. This Agreement, the
Exhibits hereto, the Investor Rights Agreement Amendment and all other documents
delivered by the Company to Purchasers or their attorneys or agents in
connection herewith or therewith or with the transactions contemplated hereby or
thereby, do not contain any untrue statement of a material fact nor, to the
Company's knowledge, omit to state a material fact necessary in order to make
the statements contained herein or therein not misleading. To the Company's
knowledge, there are no facts which (individually or in the aggregate)
materially adversely affect the business, assets, liabilities, financial
condition, prospects or operations of the Company that have not been set forth
in the Agreement, the Exhibits hereto, or in other documents delivered to
Purchasers or their attorneys or agents in connection herewith.

         3.21 CORPORATE DOCUMENTS; MINUTE BOOKS. The Certificate and Bylaws of
the Company are in the form previously provided to special counsel to the
Purchasers. The minute books of the Company provided to the Purchaser's legal
counsel contain a complete set of minutes of all meetings of and records of all
actions taken by directors and stockholders since the time of incorporation.

         3.22 REAL PROPERTY HOLDING CORPORATION. The Company is not a real
property holding corporation within the meaning of Internal Revenue Code Section
897(c)(2) and any regulations promulgated thereunder.

         3.23 MANUFACTURING AND MARKETING RIGHTS. The Company has not granted
rights to manufacture, produce, assemble, license, market or sell its products
to any third party, and is not bound by any agreement that affects the Company's
exclusive right to develop, manufacture, assemble, distribute, market or sell
its products.

         3.24 VOTING AGREEMENTS. Except as set forth in the Schedule of
Exceptions, the Stockholders Agreement, the Restated Certificate or the
Investors Rights Agreement, the Company has no agreement, obligation or
commitment with respect to the election of any individual or individuals to the
Board of Directors, and to the best of the Company's knowledge, there is no
voting agreement or other arrangement among its stockholders with respect to the
election of any individual or individuals to the Board of Directors.

                                      11.
<PAGE>

         3.25 INSURANCE. The Company has in full force and effect fire and
casualty insurance policies and insurance against other hazards, risks and
liabilities to persons and property to the extent and in the manner customary
for companies in similar businesses similarly situated.

         3.26 DISTRIBUTIONS. There has been no declaration or payment by the
Company of any dividend, nor any distribution by the Company of any assets of
any kind, to any class or series of its capital stock.

         3.27 BROKERS OR FINDERS. No broker or finder is entitled to any
brokerage or other fee from the Company based upon arrangements made by or on
behalf of the Company in connection with the transactions contemplated by this
Agreement.

         3.28 REAL PROPERTY HOLDING CORPORATION. The Company hereby represents
that it is not now and has never been a "United States real property holding
corporation", as defined in Section 897(c)(2) of the Internal Revenue Code of
1986, as amended, and Treasury Regulation Section 1.897-2(b), and that the
Company has filed with the Internal Revenue Service all statements, if any, with
its United States income tax returns, which are required under Treasury
Regulation Section 1.897-2(h).

4. REPRESENTATIONS AND WARRANTIES OF THE PURCHASERS

         Each Purchaser hereby represents and warrants to the Company as follows
(such representations and warranties do not lessen or obviate the
representations and warranties of the Company set forth in this Agreement):

         4.1 REQUISITE POWER AND AUTHORITY. Purchaser has all necessary power
and authority under all applicable provisions of law to execute and deliver this
Agreement and the Investor Rights Agreement Amendment and to carry out their
provisions. All action on Purchaser's part required for the lawful execution and
delivery of this Agreement and the Investor Rights Agreement Amendment have been
or will be effectively taken prior to the Closing. Upon their execution and
delivery, this Agreement and the Investor Rights Agreement Amendment will be
valid and binding obligations of Purchaser, enforceable in accordance with their
terms, except (i) as limited by applicable bankruptcy, insolvency,
reorganization, moratorium or other laws of general application affecting
enforcement of creditors' rights, (ii) general principles of equity that
restrict the availability of equitable remedies, and (iii) to the extent that
the enforceability of the indemnification provisions of Section 2.9 of the
Investor Rights Agreement Amendment may be limited by applicable laws.

         4.2 INVESTMENT REPRESENTATIONS. Purchaser understands that neither the
Shares nor the Conversion Shares have been registered under the Securities Act.
Purchaser also understands that the Shares are being offered and sold pursuant
to an exemption from registration contained in the Securities Act based in part
upon Purchaser's representations contained in the Agreement. Purchaser hereby
represents and warrants as follows:

                  (a) PURCHASER BEARS ECONOMIC RISK. Purchaser has substantial
experience in evaluating and investing in private placement transactions of
securities in companies similar to the Company so that it is capable of
evaluating the merits and risks of its investment in the Company and has the
capacity to protect its own interests. Purchaser must bear the economic

                                      12.
<PAGE>

risk of this investment indefinitely unless the Shares (or the Conversion
Shares) are registered pursuant to the Securities Act, or an exemption from
registration is available. Purchaser understands that the Company has no present
intention of registering the Shares, the Conversion Shares or any shares of its
Common Stock. Purchaser also understands that there is no assurance that any
exemption from registration under the Securities Act will be available and that,
even if available, such exemption may not allow Purchaser to transfer all or any
portion of the Shares or the Conversion Shares under the circumstances, in the
amounts or at the times Purchaser might propose.

                  (b) ACQUISITION FOR OWN ACCOUNT. Purchaser is acquiring the
Shares and the Conversion Shares for Purchaser's own account for investment
only, and not with a view towards their distribution.

                  (c) PURCHASER CAN PROTECT ITS INTEREST. Purchaser represents
that by reason of its, or of its management's, business or financial experience,
Purchaser has the capacity to protect its own interests in connection with the
transactions contemplated in this Agreement and the Investor Rights Agreement
Amendment. Further, Purchaser is aware of no publication of any advertisement in
connection with the transactions contemplated in the Agreement.

                  (d) ACCREDITED INVESTOR. Purchaser represents that it is an
accredited investor within the meaning of Regulation D under the Securities Act.

                  (e) COMPANY INFORMATION. Purchaser has received and read the
Financial Statements and has had an opportunity to discuss the Company's
business, management and financial affairs with directors, officers and
management of the Company and has had the opportunity to review the Company's
operations and facilities. Purchaser has also had the opportunity to ask
questions of and receive answers from, the Company and its management regarding
the terms and conditions of this investment.

                  (f) RULE 144. Purchaser acknowledges and agrees that the
Shares, and, if issued, the Conversion Shares must be held indefinitely unless
they are subsequently registered under the Securities Act or an exemption from
such registration is available. Purchaser has been advised or is aware of the
provisions of Rule 144 promulgated under the Securities Act, which permits
limited resale of shares purchased in a private placement subject to the
satisfaction of certain conditions, including, among other things, the
availability of certain current public information about the Company, the resale
occurring not less than one year after a party has purchased and paid for the
security to be sold, the sale being through an unsolicited brokers transaction
or in transactions directly with a market maker (as defined under the Securities
Exchange Act of 1934, as amended) and the number of shares being sold during any
three-month period not exceeding specified limitations.

         4.3 TRANSFER RESTRICTIONS. Each Purchaser acknowledges and agrees that
the Shares and, if issued, the Conversion Shares, are subject to restrictions on
transfer as set forth in the Investor Rights Agreement Amendment.

                                      13.
<PAGE>

5. CONDITIONS TO CLOSING

         5.1 CONDITIONS TO PURCHASERS' OBLIGATIONS AT THE CLOSING. Purchasers'
obligations to purchase the Shares at the Closing are subject to the
satisfaction, at or prior to the Closing, of the following conditions:

                  (a) REPRESENTATIONS AND WARRANTIES TRUE; PERFORMANCE OF
OBLIGATIONS. The representations and warranties made by the Company in Sections
3 hereof shall be true and correct in all material respects as of the Closing
Date with the same force and effect as if they had been made as of such Closing
Date, and the Company shall have performed and complied with all agreements and
conditions herein required to be performed or complied with by it on or before
the Closing.

                  (b) LEGAL INVESTMENT. On the Closing Date, the sale and
issuance of the Shares and the proposed issuance of the Conversion Shares shall
be legally permitted by all laws and regulations to which Purchasers and the
Company are subject.

                  (c) CONSENTS, PERMITS, AND WAIVERS. The Company shall have
obtained any and all consents, permits and waivers necessary or appropriate for
consummation of the transactions contemplated by the Agreement, the Investor
Rights Agreement and the Stockholders Agreement (except for such as may be
properly obtained subsequent to the Closing).

                  (d) CORPORATE DOCUMENTS. The Company shall have delivered to
Purchasers or their counsel, copies of all corporate documents of the Company as
Purchasers shall reasonably request.

                  (e) COMPLIANCE CERTIFICATE. The Company shall have delivered
to Purchasers a Compliance Certificate, executed by the President of the
Company, dated the date of the Closing, to the effect that the conditions
specified in subsections (a) through (l) of this Section 5.1 have been
satisfied. The Company shall have delivered to Purchasers a Secretary's
Certificate, executed by the Secretary of the Company, dated as of the Closing
Date, in form and substance reasonably satisfactory to Purchasers.

                  (f) RESERVATION OF CONVERSION SHARES. The Conversion Shares
issuable upon conversion of the Shares shall have been duly authorized and
reserved for issuance upon such conversion.

                  (g) INVESTOR RIGHTS AGREEMENT AMENDMENT. The Investor Rights
Agreement Amendment shall have been executed and delivered by the parties
thereto.

                  (h) BOARD OF DIRECTORS. Upon the Closing, the authorized size
of the Board of Directors of the Company shall be eight (8) members as set forth
in the Stockholders Agreement.

                  (i) RESTATED CERTIFICATE. The Company shall have filed with
the Secretary of State of the State of Delaware the Restated Certificate, which
shall continue to be in full force and effect as of the Closing Date.

                                      14.
<PAGE>

                  (j) LEGAL OPINION. The Purchasers shall have received from
legal counsel to the Company an opinion addressed to them, dated as of the
Closing, in substantially the form attached hereto as Exhibit G.

                  (k) PROCEEDINGS AND DOCUMENTS. All corporate and other
proceedings in connection with the transactions contemplated at the Closing
hereby and all documents and instruments incident to such transactions shall be
reasonably satisfactory in substance and form to the Purchasers and their
special counsel and the Purchasers and their special counsel shall have received
all such counterpart originals or certified or other copies of such documents as
they may reasonably request.

                  (l) DUE DILIGENCE. The Purchasers shall (i) have completed
their due diligence of the Company, and (ii) be satisfied, in their sole
discretion, with the results of such due diligence review.

                  (o) REGULATORY SIDELETTER. The Company shall have executed and
delivered to J.P. Morgan Partners (SBIC), LLC the Regulatory Sideletter.

         5.2 CONDITIONS TO OBLIGATIONS OF THE COMPANY. The Company's obligation
to issue and sell the Shares at the Closing is subject to the satisfaction, on
or prior to such Closing, of the following conditions:

                  (a) REPRESENTATIONS AND WARRANTIES TRUE. The representations
and warranties made by Purchasers in Sections 4 hereof shall be true and correct
in all material respects at the date of each Closing, with the same force and
effect as if they had been made on and as of said date.

                  (b) PERFORMANCE OF OBLIGATIONS. Purchasers shall have
performed and complied with all agreements and conditions herein required to be
performed or complied with by Purchasers on or before the Closing.

                  (c) INVESTOR RIGHTS AGREEMENT AMENDMENT. The Investor Rights
Agreement Amendment shall have been executed and delivered by the Purchasers.

                  (d) CONSENTS, PERMITS, AND WAIVERS. The Company shall have
obtained any and all consents, permits and waivers necessary or appropriate for
consummation of the transactions contemplated by the Agreement, the Investor
Rights Agreement Amendment and the Stockholders Agreement (except for such as
may be properly obtained subsequent to the Closing).

6. MISCELLANEOUS

         6.1 GOVERNING LAW. This Agreement shall be governed in all respects by
the laws of the State of Colorado as such laws are applied to agreements between
Colorado residents entered into and performed entirely in Colorado.

         6.2 SURVIVAL. The representations, warranties, covenants and agreements
made herein shall survive the execution and delivery of this Agreement, any
investigation made by any

                                      15.
<PAGE>

Purchaser and each Closing. All statements as to factual matters contained in
any certificate or other instrument delivered by or on behalf of the Company or
the Purchasers pursuant hereto in connection with the transactions contemplated
hereby shall be deemed to be representations and warranties by the Company or
the Purchasers (as the case may be) hereunder solely as of the date of such
certificate or instrument.

         6.3 SUCCESSORS AND ASSIGNS. Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors and administrators of the
parties hereto and shall inure to the benefit of and be enforceable by each
person who shall be a holder of the Shares from time to time.

         6.4 ENTIRE AGREEMENT. This Agreement, the Exhibits and Schedules
hereto, the and Investor Rights Agreement Amendment and the other documents
delivered pursuant hereto constitute the full and entire understanding and
agreement between the parties with regard to the subjects hereof and no party
shall be liable or bound to any other in any manner by any representations,
warranties, covenants and agreements except as specifically set forth herein and
therein.

         6.5 SEVERABILITY. In case any provision of the Agreement shall be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby.

         6.6 AMENDMENT AND WAIVER.

                  (a) This Agreement may be amended or modified only upon the
written consent of the Company and holders of a majority of the Shares sold
pursuant to this Agreement (treated as if converted and including any Shares
issued upon the conversion of the Shares into Common Stock that have been
converted that have not been sold to the public).

                  (b) The obligations of the Company and the rights of the
holders of the Shares and the Conversion Shares under the Agreement may be
waived only with the written consent of the holders of a majority of the Shares
sold pursuant to this Agreement (treated as if converted and including any
Shares issued upon the conversion of the Shares into Common Stock that have not
been sold to the public).

         6.7 DELAYS OR OMISSIONS. It is agreed that no delay or omission to
exercise any right, power or remedy accruing to any party, upon any breach,
default or noncompliance by another party under this Agreement, the Investor
Rights Agreement Amendment or the Restated Certificate, shall impair any such
right, power or remedy, nor shall it be construed to be a waiver of any such
breach, default or noncompliance, or any acquiescence therein, or of or in any
similar breach, default or noncompliance thereafter occurring. It is further
agreed that any waiver, permit, consent or approval of any kind or character on
any Purchaser's part of any breach, default or noncompliance under this
Agreement or under the Restated Certificate or any waiver on such party's part
of any provisions or conditions of the Agreement must be in writing and shall be
effective only to the extent specifically set forth in such writing. All
remedies, either under this Agreement, the Restated Certificate, by-law, or
otherwise afforded to any party, shall be cumulative and not alternative.

                                      16.
<PAGE>

         6.8 NOTICES. All notices required or permitted hereunder shall be in
writing and shall be deemed effectively given: (i) upon personal delivery to the
party to be notified; (ii) when sent by confirmed facsimile if sent during
normal business hours of the recipient, or if not, then on the next business
day; (iii) five (5) days after having been sent by registered or certified mail,
return receipt requested, postage prepaid; or (iv) one (1) day after deposit
with a nationally recognized overnight courier, specifying next day delivery,
with written verification of receipt. All communications shall be sent to the
Company at the address as set forth on the signature page hereof and to
Purchaser at the address set forth on Exhibit A attached hereto or at such other
address as the Company or Purchaser may designate by ten (10) days advance
written notice to the other parties hereto.

         6.9 EXPENSES. Each of the parties hereto shall pay its own fees and
expenses (including the fees of any attorneys and accountants engaged by such
party) in connection with this Agreement and the transactions contemplated
hereby whether or not the transactions contemplated hereby are consummated.

         6.10 ATTORNEYS' FEES. In the event that any dispute among the parties
to this Agreement should result in litigation, the prevailing party in such
dispute shall be entitled to recover from the losing party all fees, costs and
expenses of enforcing any right of such prevailing party under or with respect
to this Agreement, including without limitation, such reasonable fees and
expenses of attorneys and accountants, which shall include, without limitation,
all fees, costs and expenses of appeals.

         6.11 TITLES AND SUBTITLES. The titles of the sections and subsections
of the Agreement are for convenience of reference only and are not to be
considered in construing this Agreement.

         6.12 COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

         6.13 BROKER'S FEES. Each party hereto represents and warrants that no
agent, broker, investment banker, person or firm acting on behalf of or under
the authority of such party hereto, is or will be entitled to any broker's or
finder's fee or any other commission directly or indirectly in connection with
the transactions contemplated herein. Each party hereto further agrees to
indemnify each other party for any claims, losses or expenses incurred by such
other party as a result of the representation in this Section 6.13 being untrue.

         6.14 WAIVER OF CONFLICTS. Each party to this Agreement acknowledges
that Cooley Godward LLP ("COOLEY GODWARD"), outside general counsel to the
Company, has in the past performed and is or may now or in the future represent
one or more Purchasers or their affiliates in matters unrelated to the
transactions contemplated by this Agreement (the "FINANCING"), including
representation of such Purchasers or their affiliates in matters of a similar
nature to the Financing. The applicable rules of professional conduct require
that Cooley Godward inform the parties hereunder of this representation and
obtain their consent. Cooley Godward has served as outside general counsel to
the Company and has negotiated the terms of the Financing solely on behalf of
the Company. The Company and each Purchaser hereby (a) acknowledge that they
have had an opportunity to ask for and have obtained information relevant to
such representation, including disclosure of the reasonably foreseeable adverse
consequences of such representation;

                                      17.
<PAGE>

(b) acknowledge that with respect to the Financing, Cooley Godward has
represented solely the Company, and not any Purchaser or any stockholder,
director or employee of the Company or any Purchaser; and (c) gives its informed
consent to Cooley Godward's representation of the Company in the Financing.

              [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK)

                                      18.
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this SERIES D
PREFERRED STOCK PURCHASE AGREEMENT as of the date set forth in the first
paragraph hereof.

COMPANY:                                     INVESTORS:
MYOGEN, INC.                                 NEW ENTERPRISE ASSOCIATES 9,
                                             LIMITED PARTNERSHIP

By: /s/ J. William Freytag                   By: NEA Partners 9, Limited
    -------------------------------              Partnership
    J. William Freytag
    President and Chief Executive Officer

                                             By: /s/ C. Richard Kramlich
                                                --------------------------------
                                                General Partner

                                             NEW ENTERPRISE ASSOCIATES 10,
                                             LIMITED PARTNERSHIP

                                             By: NEA Partners 10, Limited
                                                 Partnership

                                             By: /s/ C. Richard Kramlich
                                                --------------------------------
                                                General Partner

                                             J.P. MORGAN PARTNERS (SBIC), LLC

                                             By: /s/ Rodney A. Ferguson
                                                --------------------------------
                                             Its: Managing Director
                                                 -------------------------------

                                             INTERWEST PARTNERS VIII, LP

                                             By: InterWest Management Partners
                                                 VIII, LLC Its General Partner

                                             By: /s/ Arnold Oronsky
                                                --------------------------------

                                             INTERWEST PARTNERS VI, LP

                                             By: InterWest Management Partners
                                                 VI, LLC Its General Partner

                                             By: /s/ Arnold Oronsky
                                                --------------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                             INTERWEST INVESTORS VIII, LP

                                             By: InterWest Management Partners
                                                 VIII, LLC Its General Partner

                                             By: /s/ Arnold Oronsky
                                                --------------------------------

                                             INTERWEST INVESTORS VI, LP

                                             By: InterWest Management Partners
                                                 VIII, LLC Its General Partner

                                             By: /s/ Arnold Oronsky
                                                --------------------------------

                                             INTERWEST INVESTORS Q VIII, LP

                                             By: InterWest Management Partners
                                                 VIII, LLC Its General Partner

                                             By: /s/ Arnold Oronsky
                                                --------------------------------

                                             PERSEUS-SOROS BIOPHARMACEUTICAL
                                             FUND, LP

                                             By: Perseus-Soros Partners, LLC,
                                                 It's General Partner

                                             By: SFM Participation, L.P., Its
                                                 Managing Member

                                             By: SFM AH, LLC., Its General
                                                 Partner

                                             By: Soros Private Funds Management
                                                 LLC, Its Managing Member

                                             By: /s/ Jodye M. Anzalotta
                                                --------------------------------
                                             Name: Jodye M. Anzalotta
                                                  ------------------------------
                                             Title: Attorney-in-Fact
                                                   -----------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                            SEQUEL LIMITED PARTNERSHIP III

                                            By: Sequel Venture Partners, LLC
                                                 Its General Partner

                                            By: /s/ Daniel J. Mitchell
                                               ---------------------------------
                                               Manager

                                            SEQUEL ENTREPRENEURS' FUND III,
                                            L.P.

                                            By: Sequel Venture Partners, LLC
                                                Its General Partner

                                            By: /s/ Daniel J. Mitchell
                                               ---------------------------------
                                               Manager

                                            PACIFIC RIM LIFE SCIENCE NO. 1
                                            INVESTMENT PARTNERSHIP

                                            By: Pacific Rim Life Science No.1/2
                                                Investment Partnership, its
                                                general partner

                                            By: /s/ Masahiro Michishita
                                               ---------------------------------
                                               Masahiro Michishita, M.D., Ph.D.,
                                               Managing General Partner

                                            PACIFIC RIM LIFE SCIENCE NO. 2
                                            INVESTMENT PARTNERSHIP

                                            By: Pacific Rim Life Science No.1/2
                                                Investment Partnership, its
                                                general partner

                                            By: /s/ Masahiro Michishita
                                               ---------------------------------
                                               Masahiro Michishita, M.D., Ph.D.,
                                               Managing General Partner

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                             CMEA LIFE SCIENCES FUND, L.P.

                                             By: Thomas R. Baruch
                                                --------------------------------
                                                General Partner

                                             HUNT VENTURES, L.P.

                                             By: /s/ Christopher W. Kleinert
                                                --------------------------------
                                             Name: Christopher W. Kleinert
                                                  ------------------------------
                                             Title: Managing Director
                                                   -----------------------------

                                             BVCF IV, L.P.
                                             By: J.W. Puth Associates, LLC, its
                                                 General Partner
                                             By: Brinson Venture Management,
                                                 LLC, it's Attorney-in-fact
                                             By: Adams Street Partners, LLC, as
                                                 its Administrative Member

                                             By: /s/ Craig S. Taylor
                                                --------------------------------
                                                Craig S. Taylor
                                                Partner

                                             SILICON VALLEY BANCVENTURES L.P.

                                             By: /s/ Aaron Gershenberg
                                                --------------------------------
                                             Name: Aaron Gershenberg
                                                  ------------------------------
                                             Title: Managing Director
                                                   -----------------------------

                                             MONTAGU NEWHALL GLOBAL PARTNERS LP

                                             By: /s/ C. Ashton Newhall
                                                --------------------------------
                                             Name: C. Ashton Newhall
                                                  ------------------------------
                                             Title: General Partner
                                                   -----------------------------

                            STOCK PURCHASE AGREEMENT

<PAGE>

                                    EXHIBIT A

                             SCHEDULE OF PURCHASERS

<Table>
<Caption>
                     NAME AND ADDRESS                                SHARES             PRICE
                     ----------------                            --------------     --------------
<S>                                                              <C>                <C>

     New Enterprise Associates 10, Limited Partnership                9,454,456      13,000,000.75
     2490 Sand Hill Road
     Menlo Park, CA  94025
     Attn:  Sigrid Van Bladel

     New Enterprise Associates 9, Limited Partnership                   727,272         999,999.00
     2490 Sand Hill Road
     Menlo Park, CA  94025
     Attn:  Sigrid Van Bladel

     J.P. Morgan Partners (SBIC), LLC                                 5,818,181     $ 7,999,998.88
     50 California Street, Suite 2940
     San Francisco, CA 94111
     Attn:  Rod Ferguson

              With a copy to:

              J.P. Morgan Partners
              Official Notices Clerk
              1221 Avenue of the Americas
              New York, NY 10020
              Facsimile:  (212) 899-3401

              and

              J.P. Morgan Partners (SBIC), LLC
              50 California Street, Suite 2940
              San Francisco, CA 94111
              Attn:  Shannon Horton

     InterWest Partners VI, L.P.                                      1,128,261       1,551,358.88
     2710 Sand Hill Road
     Second Floor
     Menlo Park, CA 94025
     Attn:  Arnold L. Oronsky

     InterWest Investors VI, L.P.                                        35,375          48,640.62
     2710 Sand Hill Road
     Second Floor
     Menlo Park, CA 94025
     Attn:  Arnold L. Oronsky
</Table>

<PAGE>

<Table>
<Caption>
                     NAME AND ADDRESS                                SHARES             PRICE
                     ----------------                            --------------     --------------
<S>                                                              <C>                <C>
     InterWest Partners VIII, L.P.                                    2,828,534       3,889,234.25
     2710 Sand Hill Road
     Second Floor
     Menlo Park, CA 94025
     Attn:  Arnold L. Oronsky

     InterWest Investors VIII, L.P.                                      22,577          31,043.38
     2710 Sand Hill Road
     Second Floor
     Menlo Park, CA 94025
     Attn:  Arnold L. Oronsky

     InterWest Investors Q VIII, L.P.                                    80,924         111,270.50
     2710 Sand Hill Road
     Second Floor
     Menlo Park, CA 94025
     Attn:  Arnold L. Oronsky

     Perseus-Soros Biopharmaceutical Fund, LP                         2,569,832       3,533,519.00
     888 Seventh Avenue, 29th Floor
     New York, NY  10106
     Attn:  Steve Elms

              with a copy to:

              Perseus-Soros Biopharmaceutical
              Fund, L.P.
              c/o Soros Fund Management LLC
              888 Seventh Avenue, 31st Floor
              New York, NY 10106
              Attention: Richard Holahan, Jr., Esq.

              And

              Paul, Weiss, Rifkind, Wharton &
              Garrison
              1285 Avenue of the Americas
              New York, New York 10019-6064
              Attention: Bruce A. Gutenplan, Esq.

     Sequel Limited Partnership III                                   2,903,701       3,992,588.88
     4430 Arapahoe Avenue, Suite 220
     Boulder, CO 80303
     Attn:  Dan Mitchell

     Sequel Entrepreneurs' Fund III, L.P.                                80,697         110,958.38
     4430 Arapahoe Avenue, Suite 220
     Boulder, CO 80303
     Attn:  Dan Mitchell
</Table>

                                       A-2
<PAGE>

<Table>
<Caption>
                     NAME AND ADDRESS                                SHARES             PRICE
                     ----------------                            --------------     --------------
<S>                                                              <C>                <C>

     CMEA Life Sciences Fund, L.P.                                    1,019,245       1,401,461.88
     One Embarcadero Center, Suite 3250
     San Francisco, CA 94111
     Attn:  Meryl L. Schreibstein
            Christine Cordaro

     Hunt Ventures, L.P.                                                642,137         882,938.38
     Suite 1500
     1445 Ross Avenue
     Dallas, TX  75202-2785
     Attn:  Fulton Murray
            Tom Hurtekant, Esq.

     Pacific Rim Life Science No.1 Investment                           647,480         890,285.00
     Partnership
     (C/O) Pacific Rim Ventures Co., Ltd.
     2nd Floor, Green Plaza
     3-7-20 Komazawa, Setagaya-ku
     Tokyo 154-0012, Japan

     Pacific Rim Life Science No.2 Investment                           323,739         445,141.13
     Partnership
     (C/O) Pacific Rim Ventures Co., Ltd.
     2nd Floor, Green Plaza
     3-7-20 Komazawa, Setagaya-ku
     Tokyo 154-0012, Japan
              Both care of:
              Dr. Masahiro Michishita, President,
              Pacific Rim Ventures Co., Ltd.
              2nd Floor, Green Plaza
              3-7-20 Komazawa, Setagaya-ku
              Tokyo 154-0012, Japan

     BVCF IV, L.P.                                                      363,636         499,999.50
     c/o Adam Street Partners, LLC
     209 South LaSalle Street
     Chicago, IL 60604
     Attn:  Craig S. Taylor, Ph.D.

     Silicon Valley BancVentures L.P.                                   240,921         331,266.38
     c/o Silicon Valley BancVentures, Inc.
     Attn:  Adam Tweedy
     One Newton Executive Park
     Suite 200
     Newton, MA  02462

     Montagu Newhall Global Partners LP                                 203,849         280,292.38
     52 Upper Brook Street
     London W1K 2BU
     Attention:  Rupert Montagu

     TOTAL:                                                          29,090,907     $39,999,999.86
</Table>

                                       A-3
<PAGE>

                                    EXHIBIT B

                              RESTATED CERTIFICATE

                    [Filed separately as Exhibit 3.1 to the
                 Company's Registration Statement on Form S-1]

<PAGE>

                                    EXHIBIT C

                             FIRST AMENDMENT TO THE

              THIRD AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT

                    [Filed separately as Exhibit 10.8 to the
                 Company's Registration Statement on Form S-1]

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00055-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00055-of-00352.parquet"}]]