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                                                                 Exhibit 10.19


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

                                     MITOKOR

                            WARRANT TO PURCHASE SHARES
                           OF SERIES E PREFERRED STOCK

         THIS CERTIFIES THAT, for value received, MEIER MITCHELL & COMPANY and
its assignees are entitled to subscribe for and purchase that number of the
fully paid and nonassessable shares of Series E Preferred Stock (as adjusted
pursuant to Section 4 hereof, the "Shares") of MITOKOR, a California corporation
(the "Company"), as is determined pursuant to the next paragraph hereof at the
price per share as is determined pursuant to the next paragraph hereof (such
price and such other price as shall result, from time to time, from the
adjustments specified in Section 4 hereof is herein referred to as the "Warrant
Price"), subject to the provisions and upon the terms and conditions hereinafter
set forth. As used herein, (a) the term "Series Preferred" shall mean the
Company's presently authorized Series E Preferred Stock, and any stock into or
for which such Series E Preferred Stock may hereafter be converted or exchanged,
and after the automatic conversion of the Series E Preferred Stock to Common
Stock shall mean the Company's Common Stock, (b) the term "Date of Grant" shall
mean December 15, 1999, and (c) the term "Other Warrants" shall mean any other
warrants issued by the Company in connection with the transaction with respect
to which this Warrant was issued, and any warrant issued upon transfer or
partial exercise of or in lieu of this Warrant. The term "Warrant" as used
herein shall be deemed to include Other Warrants unless the context clearly
requires otherwise.

         The Warrant Price shall be the lower of (i) $6.00 and (ii) the price
per share of preferred stock in the next venture round which occurs before the
earlier of (a) August 31, 2000, and (b) the entire "Credit Amount" being
borrowed by the Company under the "Facility;" provided, however, the Warrant
Price shall not be lower than $4.80. The "Facility" shall mean the Equipment
Loan and Security Agreement dated as of December 15, 1999 (the "Loan
Agreement"). The "Credit Amount" shall have the meaning given such term in the
Loan Agreement. The number of shares for which this Warrant is exercisable shall
be the nearest whole number determined by dividing $51,000 by the Warrant Price
determined pursuant to this paragraph.

         1.  TERM. The purchase right represented by this Warrant is
exercisable, in whole or in part, at any time and from time to time from the
Date of Grant through the later of (i) ten (10) years after the Date of Grant or
(ii) five (5) years after the closing of the Company's initial public offering

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of its Common Stock ("IPO") effected pursuant to a Registration Statement on
Form S-1 (or its successor) filed under the Securities Act of 1933, as amended
(the "Act").

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

         3.  STOCK FULLY PAID; RESERVATION OF SHARES. All Shares that may be
issued upon the exercise of the rights represented by this Warrant will, upon
issuance pursuant to the terms and conditions herein, be fully paid and
nonassessable, and free from all taxes, liens and charges with respect to the
issue thereof. During the period within which the rights represented by this
Warrant may be exercised, the Company will at all times have authorized, and
reserved for the purpose of the issue upon exercise of the purchase rights
evidenced by this Warrant, a sufficient number of shares of its Series Preferred
to provide for the exercise of the rights represented by this Warrant and a
sufficient number of shares of its Common Stock to provide for the conversion of
the Series Preferred into Common Stock.


                                      -2-

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         4.  ADJUSTMENT OF WARRANT PRICE AND NUMBER OF SHARES. The number and
kind of securities purchasable upon the exercise of this Warrant and the Warrant
Price shall be subject to adjustment from time to time upon the occurrence of
certain events, as follows:

             (a) RECLASSIFICATION OR MERGER. In case of any reclassification or
change of securities of the class issuable upon exercise of this Warrant (other
than a change in par value, or from par value to no par value, or from no par
value to par value, or as a result of a subdivision or combination), or in case
of any merger of the Company with or into another corporation (other than a
merger with another corporation in which the Company is the acquiring and the
surviving corporation and which does not result in any reclassification or
change of outstanding securities issuable upon exercise of this Warrant), or in
case of any sale of all or substantially all of the assets of the Company, the
Company, or such successor or purchasing corporation, as the case may be, shall
duly execute and deliver to the holder of this Warrant a new Warrant (in form
and substance satisfactory to the holder of this Warrant), or the Company shall
make appropriate provision without the issuance of a new Warrant, so that the
holder of this Warrant shall have the right to receive, at a total purchase
price not to exceed that payable upon the exercise of the unexercised portion of
this Warrant, and in lieu of the shares of Series Preferred theretofore issuable
upon exercise of this Warrant, (i) the kind and amount of shares of stock, other
securities, money and property receivable upon such reclassification, change,
merger or sale by a holder of the number of shares of Series Preferred then
purchasable under this Warrant. Any new Warrant shall provide for adjustments
that shall be as nearly equivalent as may be practicable to the adjustments
provided for in this Section 4. The provisions of this subparagraph (a) shall
similarly apply to successive reclassifications, changes, mergers and transfers.

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

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


                                      -3-

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record date fixed for the determination of the shareholders of the Company
entitled to receive such dividend or distribution.

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

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


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

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

         7.  COMPLIANCE WITH ACT; DISPOSITION OF WARRANT OR SHARES OF SERIES
PREFERRED.

             (a) COMPLIANCE WITH ACT. The holder of this Warrant, by acceptance
hereof, agrees that this Warrant, and the shares of Series Preferred to be
issued upon exercise hereof and any Common Stock issued upon conversion thereof
are being acquired for investment and that such holder will not offer, sell or
otherwise dispose of this Warrant, or any shares of Series Preferred to be
issued upon exercise hereof or any Common Stock issued upon conversion thereof
except under circumstances which will not result in a violation of the Act or
any applicable state securities laws.


                                      -4-

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

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

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

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

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

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

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

             (b) DISPOSITION OF WARRANT OR SHARES. With respect to any offer,
sale or other disposition of this Warrant or any shares of Series Preferred
acquired pursuant to the exercise of this


                                      -5-

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

             (c) APPLICABILITY OF RESTRICTIONS. Neither any restrictions of any
legend described in this Warrant nor the requirements of Section 7(b) above
shall apply to any transfer of, or grant of a security interest in, this Warrant
(or the Series Preferred or Common Stock obtainable upon exercise thereof) or
any part hereof (i) to a partner of the holder if the holder is a partnership or
to a member of the holder if the holder is a limited liability company, (ii) to
a partnership of which the holder is a partner or to a limited liability company
of which the holder is a member, or (iii) to any affiliate of the holder if the
holder is a corporation; PROVIDED, HOWEVER, in any such transfer, if applicable,
the transferee shall on the Company's request agree in writing to be bound by
the terms of this Warrant as if an original holder hereof.


         8.  RIGHTS AS SHAREHOLDERS; INFORMATION. No holder of this Warrant, as
such, shall be entitled to vote or receive dividends or be deemed the holder of
Series Preferred or any other securities of the Company which may at any time be
issuable on the exercise hereof for any purpose, nor shall anything contained
herein be construed to confer upon the holder of this Warrant, as such, any of
the rights of a shareholder of the Company or any right to vote for the election
of directors or upon any matter submitted to shareholders at any meeting
thereof, or to receive notice of meetings, or to receive dividends or
subscription rights or otherwise until this Warrant shall have been exercised
and the Shares purchasable upon the exercise hereof shall have become
deliverable, as provided herein. Notwithstanding the foregoing, the Company will
transmit to the holder of this


                                      -6-

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Warrant such information, documents and reports as are generally distributed to
the holders of any class or series of the securities of the Company concurrently
with the distribution thereof to the shareholders.

         9.  [RESERVED]


         10. ADDITIONAL RIGHTS.

             10.1 ACQUISITION TRANSACTIONS. The Company shall provide the holder
of this Warrant with at least twenty (20) days' written notice prior to closing
thereof of the terms and conditions of any of the following transactions (to the
extent the Company has notice thereof): (i) the sale, lease, exchange,
conveyance or other disposition of all or substantially all of the Company's
property or business, or (ii) its merger into or consolidation with any other
corporation (other than a wholly-owned subsidiary of the Company), or any
transaction (including a merger or other reorganization) or series of related
transactions, in which more than 50% of the voting power of the Company is
disposed of.

             10.2 RIGHT TO CONVERT WARRANT INTO STOCK: NET ISSUANCE.


                  (a) RIGHT TO CONVERT. In addition to and without limiting the
rights of the holder under the terms of this Warrant, the holder shall have the
right to convert this Warrant or any portion thereof (the "Conversion Right")
into shares of Series Preferred (or Common Stock if the Series Preferred has
been automatically converted into Common Stock) as provided in this Section 10.2
at any time or from time to time during the term of this Warrant. Upon exercise
of the Conversion Right with respect to a particular number of shares subject to
this Warrant (the "Converted Warrant Shares"), the Company shall deliver to the
holder (without payment by the holder of any exercise price or any cash or other
consideration) that number of shares of fully paid and nonassessable Series
Preferred (or Common Stock if the Series Preferred has been automatically
converted into Common Stock) as is determined according to the following
formula:

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

         Where: X  =  the number of shares of Series Preferred (or Common Stock
                      if the Series Preferred has been automatically converted
                      to Common Stock) that shall  be issued to holder

                Y  =  the fair market value of one share of Series Preferred
                      (or Common Stock if the Series Preferred has been
                      automatically converted to Common Stock)

                A  =  the aggregate Warrant Price of the specified number of
                      Converted Warrant Shares immediately prior to the exercise
                      of the Conversion Right (I.E., the number of Converted
                      Warrant Shares MULTIPLIED BY the Warrant Price)


                                      -7-

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                B  =  the aggregate fair market value of the specified number of
                      Converted Warrant Shares (I.E., the number of Converted
                      Warrant Shares MULTIPLIED BY the fair market value of one
                      Converted Warrant Share)

         No fractional shares shall be issuable upon exercise of the Conversion
Right, and, if the number of shares to be issued determined in accordance with
the foregoing formula is other than a whole number, the Company shall pay to the
holder an amount in cash equal to the fair market value of the resulting
fractional share on the Conversion Date (as hereinafter defined). For purposes
of Section 9 of this Warrant, shares issued pursuant to the Conversion Right
shall be treated as if they were issued upon the exercise of this Warrant.


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


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

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

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

                  (A) If traded on a securities exchange, the fair market value
of the Common Stock shall be deemed to be the average of the closing prices of
the Common Stock on such exchange over the 30-day period ending five business
days prior to the Determination Date, and the fair market value of the Series
Preferred shall be deemed to be such fair market value of the Common Stock
multiplied by the number of shares of Common Stock into which each share of
Series Preferred is then convertible;


                                      -8-

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

                  (C) If there is no public market for the Common Stock, then
fair market value shall be determined by mutual agreement of the holder of this
Warrant and the Company.


         11. REPRESENTATIONS AND WARRANTIES. The Company represents and warrants
to the holder of this Warrant as follows:

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

             (b) The Shares have been duly authorized and reserved for issuance
by the Company and, when issued in accordance with the terms hereof, will be
validly issued, fully paid and non-assessable;

             (c) The rights, preferences, privileges and restrictions granted to
or imposed upon the Series Preferred and the holders thereof are as set forth in
the Charter, and on the Date of Grant, each share of the Series Preferred
represented by this Warrant is convertible into one share of Common Stock;

             (d) The shares of Common Stock issuable upon conversion of the
Shares have been duly authorized and reserved for issuance by the Company and,
when issued in accordance with the terms of the Charter will be validly issued,
fully paid and nonassessable;


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

             (f) There are no actions, suits, audits, investigations or
proceedings pending or, to the knowledge of the Company, threatened against the
Company in any court or before any


                                      -9-

<Page>


governmental commission, board or authority which, if adversely determined, will
have a material adverse effect on the ability of the Company to perform its
obligations under this Warrant.


             (g) The number of shares of Common Stock of the Company outstanding
on the date hereof, on a fully diluted basis (assuming the conversion of all
outstanding convertible securities and the exercise of all outstanding options
and warrants), does not exceed 9,400,000 shares.



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

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

         14. BINDING EFFECT ON SUCCESSORS. This Warrant shall be binding upon
any corporation succeeding the Company by merger, consolidation or acquisition
of all or substantially all of the Company's assets, and all of the obligations
of the Company relating to the Series Preferred issuable upon the exercise or
conversion of this Warrant shall survive the exercise, conversion and
termination of this Warrant and all of the covenants and agreements of the
Company shall inure to the benefit of the successors and assigns of the holder
hereof.

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

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

         17. GOVERNING LAW. This Warrant shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the State of California.

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


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<Page>


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

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

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

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

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


                                      -11-

<Page>


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

                                       MITOKOR


                                       By   /s/ Walter H. Moos (W.H. Moos)
                                         ---------------------------------------

                                       Title  Chairman & CEO
                                            ------------------------------------

                                       Address:  11494 Sorrento Valley Road,
                                                 Suite 21
                                                 San Diego, CA  92121


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