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                                                                     Exhibit 4.3




                                 DIADEXUS, INC.

                           INVESTOR'S RIGHTS AGREEMENT

                                 JULY 11, 2001


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                                TABLE OF CONTENTS

<TABLE>
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                                                                                           PAGE
                                                                                           ----
<S>                                                                                         <C>
1.   REGISTRATION RIGHTS.....................................................................1

   1.1  DEFINITIONS..........................................................................1
   1.2  COMPANY REGISTRATION.................................................................2
   1.3  OBLIGATIONS OF THE COMPANY...........................................................2
   1.4  FURNISH INFORMATION..................................................................4
   1.5  EXPENSES OF REGISTRATION.............................................................4
   1.6  UNDERWRITING REQUIREMENTS............................................................4
   1.7  DELAY OF REGISTRATION................................................................5
   1.8  INDEMNIFICATION......................................................................5
   1.9  REPORTS UNDER SECURITIES EXCHANGE ACT OF 1934........................................7
   1.10   ASSIGNMENT OF REGISTRATION RIGHTS..................................................7
   1.11   MARKET-STANDOFF AGREEMENT..........................................................8
   1.12   TERMINATION OF REGISTRATION RIGHTS.................................................8

2.   COVENANTS OF THE COMPANY................................................................8

   2.1  RESERVATION OF COMMON STOCK..........................................................9
   2.2  COMPANY RIGHT OF FIRST OFFER.........................................................9
   2.3  TERMINATION OF COVENANTS.............................................................9

3.   MISCELLANEOUS..........................................................................10

   3.1  SUCCESSORS AND ASSIGNS..............................................................10
   3.2  AMENDMENTS AND WAIVERS..............................................................10
   3.3  NOTICES.............................................................................10
   3.4  SEVERABILITY........................................................................10
   3.5  GOVERNING LAW.......................................................................10
   3.6  COUNTERPARTS........................................................................11
   3.7  TITLES AND SUBTITLES................................................................11
   3.8  AGGREGATION OF STOCK................................................................11
   3.9  VOTING AGREEMENT....................................................................11
</TABLE>


                                       i
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                                 DIADEXUS, INC.

                           INVESTOR'S RIGHTS AGREEMENT

        This Investor's Rights Agreement (the "Agreement") is made as of the
11th day of July, 2001, by and between diaDexus, Inc., a Delaware corporation
(the "Company") and the investor listed on Exhibit A hereto (the "Investor").

                                    RECITALS

        The Company and the Investor have entered into a Series D Preferred
Stock Purchase Agreement (the "Purchase Agreement") of even date herewith
pursuant to which the Company desires to sell to the Investor and the Investor
desires to purchase from the Company shares of the Company's Series D Preferred
Stock (the "Series D Stock"). A condition to the Investor's obligations under
the Purchase Agreement is that the Company and the Investor enter into this
Agreement in order to provide the Investor with certain rights, including the
registration of shares of the Company's Common Stock, par value $0.01 per share
(the "Common Stock"), issuable upon conversion of the Series D Stock held by it.
In order to induce the Investor to purchase shares of the Company's Series D
Stock, the Company hereby agrees that this Agreement will govern certain rights
of the Investor with respect to the Series D Stock as set forth herein.

                                    AGREEMENT

        The parties hereby agree as follows:

1.      REGISTRATION RIGHTS. The Company and the Investor covenant and agree as
follows:

        1.1 DEFINITIONS. For purposes of this Section 1:

            (a) The terms "register," "registered," and "registration" refer to
a registration effected by preparing and filing a registration statement or
similar document in compliance with the Securities Act of 1933, as amended (the
"Securities Act"), and the declaration or ordering of effectiveness of such
registration statement or document;

            (b) The term "Registrable Securities" means (i) the shares of Common
Stock issuable or issued upon conversion of the Series D Stock, and (ii) any
other shares of Common Stock of the Company issued as (or issuable upon the
conversion or exercise of any warrant, right or other security which is issued
as) a dividend or other distribution with respect to, or in exchange for or in
replacement of, the shares listed in (i); provided, however, that the foregoing
definition shall exclude in all cases any Registrable Securities sold by a
person in a transaction in which his or her rights under this Agreement are not
assigned. Notwithstanding the foregoing, Common Stock or other securities shall
only be treated as Registrable Securities if and so long as they have not been
(A) sold to or through a broker or dealer or underwriter in a public
distribution or a public securities transaction, or (B) sold in a transaction
exempt from the registration and prospectus delivery requirements of the
Securities Act under Section 4(1) thereof
<PAGE>


so that all transfer restrictions, and restrictive legends with respect thereto,
if any, are removed upon the consummation of such sale;

            (c) The number of shares of "Registrable Securities then
outstanding" shall be determined by the number of shares of Common Stock
outstanding which are, and the number of shares of Common Stock issuable
pursuant to then exercisable or convertible securities which are, Registrable
Securities;

            (d) The term "Holder" means any person owning or having the right to
acquire Registrable Securities or any assignee thereof in accordance with
Section 1.10 of this Agreement;

            (e) The term "Form S-3" means such form under the Securities Act as
in effect on the date hereof or any successor form under the Securities Act;

            (f) The term "SEC" means the Securities and Exchange Commission; and

            (g) The term "Qualified IPO" means a firm commitment underwritten
public offering by the Company of shares of its Common Stock pursuant to a
registration statement on Form S-1 under the Securities Act, the public offering
price of which is not less than $10.00 per share (appropriately adjusted for any
stock split, dividend, combination or other recapitalization) and which results
in aggregate cash proceeds to the Company of at least $20,000,000 (prior to
underwriting discounts and commissions).

        1.2 COMPANY REGISTRATION. If (but without any obligation to do so) the
Company proposes to register (including for this purpose a registration effected
by the Company for shareholders other than the Holders) any of its stock under
the Securities Act in connection with the public offering of such securities
solely for cash (other than a registration relating solely to the sale of
securities to participants in a Company stock plan or a transaction covered by
Rule 145 under the Securities Act), the Company shall, at such time, promptly
give each Holder written notice of such registration. Upon the written request
of each Holder given within twenty (20) days after mailing of such notice by the
Company in accordance with Section 3.3, the Company shall, subject to the
provisions of Section 1.6, cause to be registered under the Securities Act all
of the Registrable Securities that each such Holder has requested to be
registered. The Company shall have the right to terminate or withdraw any
registration initiated by it under this Section 1.2 prior to the effectiveness
of such registration whether or not any Holder has elected to include
Registrable Securities in such registration.

        1.3 OBLIGATIONS OF THE COMPANY. Whenever required under this Section 1
to effect the registration of any Registrable Securities, the Company shall, as
expeditiously as reasonably possible:

            (a) Prepare and file with the SEC a registration statement with
respect to such Registrable Securities and use its best efforts to cause such
registration statement to become effective, and, upon the request of the Holders
of a majority of the Registrable Securities registered thereunder, keep such
registration statement effective for up to one hundred twenty (120) days. The
Company shall not be required to file, cause to become effective or maintain the


                                       2
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effectiveness of any registration statement that contemplates a distribution of
securities on a delayed or continuous basis pursuant to Rule 415 under the
Securities Act.

            (b) Prepare and file with the SEC such amendments and supplements to
such registration statement and the prospectus used in connection with such
registration statement as may be necessary to comply with the provisions of the
Securities Act with respect to the disposition of all securities covered by such
registration statement for up to one hundred twenty (120) days.

            (c) Furnish to the Holders such numbers of copies of a prospectus,
including a preliminary prospectus, in conformity with the requirements of the
Securities Act, and such other documents as they may reasonably request in order
to facilitate the disposition of Registrable Securities owned by them.

            (d) Use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or blue sky
laws of such jurisdictions as shall be reasonably requested by the Holders,
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions.

            (e) In the event of any underwritten public offering, enter into and
perform its obligations under an underwriting agreement, in usual and customary
form, with the managing underwriter of such offering. Each Holder participating
in such underwriting shall also enter into and perform its obligations under
such an agreement.

            (f) Notify each Holder of Registrable Securities covered by such
registration statement at any time when a prospectus relating thereto is
required to be delivered under the Securities Act of the happening of any event
as a result of which the prospectus included in such registration statement, as
then in effect, includes an untrue statement of a material fact or omits to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading in the light of the circumstances then
existing, such obligation to continue for one hundred twenty (120) days. The
Company will use reasonable efforts to amend or supplement such prospectus in
order to cause such prospectus not to include any untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
to make the statements therein not misleading in the light of the circumstances
then existing.

            (g) Cause all such Registrable Securities registered pursuant
hereunder to be listed on each securities exchange on which similar securities
issued by the Company are then listed.

            (h) Provide a transfer agent and registrar for all Registrable
Securities registered pursuant hereunder and a CUSIP number for all such
Registrable Securities, in each case not later than the effective date of such
registration.

            (i) Use its best efforts to furnish, at the request of any Holder
requesting registration of Registrable Securities pursuant to this Section 1, on
the date that such Registrable Securities are delivered to the underwriters for
sale in connection with a registration pursuant to this Section 1, if such
securities are being sold through underwriters, (i) an opinion, dated such


                                       3
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date, of the counsel representing the Company for the purposes of such
registration, in form and substance as is customarily given to underwriters in
an underwritten public offering, addressed to the underwriters, and (ii) a
letter dated such date, from the independent certified public accountants of the
Company, in form and substance as is customarily given by independent certified
public accountants to underwriters in an underwritten public offering, addressed
to the underwriters.

        1.4 FURNISH INFORMATION. It shall be a condition precedent to the
obligations of the Company to take any action pursuant to this Section 1 with
respect to the Registrable Securities of any selling Holder that such Holder
shall furnish to the Company such information regarding itself, the Registrable
Securities held by it, and the intended method of disposition of such securities
as shall be required to effect the registration of such Holder's Registrable
Securities.

        1.5 EXPENSES OF REGISTRATION. All expenses other than underwriting
discounts and commissions incurred in connection with registrations, filings or
qualifications of Registrable Securities pursuant to Section 1.2 for each Holder
(which right may be assigned as provided in Section 1.10), including (without
limitation) all registration, filing, and qualification fees, printers' and
accounting fees, fees and disbursements of counsel for the Company and the
reasonable fees and disbursements of one counsel for the selling Holder or
Holders selected by them with the approval of the Company, which approval shall
not be unreasonably withheld, shall be borne by the Company.

        1.6 UNDERWRITING REQUIREMENTS. In connection with any offering involving
an underwriting of shares of the Company's capital stock, the Company shall not
be required under Section 1.2 to include any of the Holders' securities in such
underwriting unless they accept the terms of the underwriting as agreed upon
between the Company and the underwriters selected by it (or by other persons
entitled to select the underwriters), and then only in such quantity as the
underwriters determine in their sole discretion will not jeopardize the success
of the offering by the Company. If the total amount of securities, including
Registrable Securities, requested by shareholders to be included in such
offering exceeds the amount of securities sold other than by the Company that
the underwriters determine in their sole discretion is compatible with the
success of the offering, then the Company shall be required to include in the
offering only that number of such securities, including Registrable Securities,
which the underwriters determine in their sole discretion will not jeopardize
the success of the offering (the securities so included to be apportioned pro
rata among the selling shareholders according to the total amount of securities
entitled to be included therein owned by each selling shareholder or in such
other proportions as shall mutually be agreed to by such selling shareholders;
provided, however, that the Company shall not be required to include any
Registrable Securities until such time as the Company has included all shares of
Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock
of the Company (or any shares of Common Stock issued upon conversion thereof)
requested by holders of such stock to be included in such offering). For
purposes of the preceding parenthetical concerning apportionment, for any
selling shareholder which is a holder of Registrable Securities and which is a
partnership or corporation, the partners, retired partners and shareholders of
such holder, or the estates and family members of any such partners and retired
partners and any trusts for the benefit of any of the foregoing persons shall be
deemed to be a single "selling shareholder," and any pro-rata reduction with
respect to such "selling shareholder" shall be based upon the aggregate amount
of shares


                                       4
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carrying registration rights owned by all entities and individuals included in
such "selling shareholder," as defined in this sentence.

        1.7 DELAY OF REGISTRATION. No Holder shall have any right to obtain or
seek an injunction restraining or otherwise delaying any such registration as
the result of any controversy that might arise with respect to the
interpretation or implementation of this Section 1.

        1.8 INDEMNIFICATION. In the event any Registrable Securities are
included in a registration statement under this Section 1:

            (a) To the extent permitted by law, the Company will indemnify and
hold harmless each Holder, any underwriter (as defined in the Securities Act)
for such Holder and each person, if any, who controls such Holder or underwriter
within the meaning of the Securities Act or the Securities Exchange Act of 1934,
as amended (the "Exchange Act"), against any losses, claims, damages, or
liabilities (joint or several) to which they may become subject under the
Securities Act, the Exchange Act or other federal or state law, insofar as such
losses, claims, damages, or liabilities (or actions in respect thereof) arise
out of or are based upon any of the following statements, omissions or
violations (collectively a "Violation"): (i) any untrue statement or alleged
untrue statement of a material fact contained in such registration statement,
including any preliminary prospectus or final prospectus contained therein or
any amendments or supplements thereto, (ii) the omission or alleged omission to
state therein a material fact required to be stated therein, or necessary to
make the statements therein not misleading, or (iii) any violation or alleged
violation by the Company of the Securities Act, the Exchange Act, any state
securities law or any rule or regulation promulgated under the Securities Act,
the Exchange Act or any state securities law; and the Company will pay to each
such Holder, underwriter or controlling person, as incurred, any legal or other
expenses reasonably incurred by them in connection with investigating or
defending any such loss, claim, damage, liability, or action; provided, however,
that the indemnity agreement contained in this subsection 1.8(a) shall not apply
to amounts paid in settlement of any such loss, claim, damage, liability, or
action if such settlement is effected without the consent of the Company (which
consent shall not be unreasonably withheld), nor shall the Company be liable to
any Holder, underwriter or controlling person for any such loss, claim, damage,
liability, or action to the extent that it arises out of or is based upon a
Violation which occurs in reliance upon and in conformity with written
information furnished expressly for use in connection with such registration by
any such Holder, underwriter or controlling person.

               (b) To the extent permitted by law, each selling Holder will
indemnify and hold harmless the Company, each of its directors, each of its
officers who has signed the registration statement, each person, if any, who
controls the Company within the meaning of the Securities Act, any underwriter,
any other Holder selling securities in such registration statement and any
controlling person of any such underwriter or other Holder, against any losses,
claims, damages, or liabilities (joint or several) to which any of the foregoing
persons may become subject, under the Securities Act, the Exchange Act or other
federal or state law, insofar as such losses, claims, damages, or liabilities
(or actions in respect thereto) arise out of or are based upon any Violation, in
each case to the extent (and only to the extent) that such Violation occurs in
reliance upon and in conformity with written information furnished by such
Holder under an instrument duly executed by such Holder and stated to be
expressly for use in connection with


                                       5
<PAGE>


such registration; and each such Holder will pay, as incurred, any legal or
other expenses reasonably incurred by any person intended to be indemnified
pursuant to this subsection 1.8(b), in connection with investigating or
defending any such loss, claim, damage, liability, or action; provided, however,
that the indemnity agreement contained in this subsection 1.8(b) shall not apply
to amounts paid in settlement of any such loss, claim, damage, liability or
action if such settlement is effected without the consent of the Holder, which
consent shall not be unreasonably withheld; provided, that in no event shall any
indemnity under this subsection 1.8(b) exceed the net proceeds from the offering
received by such Holder.

            (c) Promptly after receipt by an indemnified party under this
Section 1.8 of notice of the commencement of any action (including any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying party under this Section 1.8, deliver to
the indemnifying party a written notice of the commencement thereof and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume the defense thereof with counsel mutually
satisfactory to the parties; provided, however, that an indemnified party
(together with all other indemnified parties which may be represented without
conflict by one counsel) shall have the right to retain one separate counsel,
with the reasonable fees and expenses to be paid by the indemnifying party, if
representation of such indemnified party by the counsel retained by the
indemnifying party would be inappropriate due to actual or potential differing
interests between such indemnified party and any other party represented by such
counsel in such proceeding. The failure to deliver written notice to the
indemnifying party within a reasonable time of the commencement of any such
action, if materially prejudicial to its ability to defend such action, shall
relieve such indemnifying party of any liability to the indemnified party under
this Section 1.8, but the omission so to deliver written notice to the
indemnifying party will not relieve it of any liability that it may have to any
indemnified party otherwise than under this Section 1.8. No Indemnifying Party,
in the defense of any such claim or litigation, shall except with the consent of
each Indemnified Party, consent to entry of any judgment or enter into any
settlement which does not include as an unconditional term thereof the giving by
the claimant or plaintiff to such Indemnified Party of a release from all
liability in respect to such claim or litigation.

            (d) If the indemnification provided for in this Section 1.8 is held
by a court of competent jurisdiction to be unavailable to an indemnified party
with respect to any loss, liability, claim, damage or expense referred to
therein, then the indemnifying party, in lieu of indemnifying such indemnified
party hereunder, shall contribute to the amount paid or payable by such
indemnified party as a result of such loss, liability, claim, damage, or expense
in such proportion as is appropriate to reflect the relative fault of the
indemnifying party on the one hand and of the indemnified party on the other in
connection with the statements or omissions that resulted in such loss,
liability, claim, damage or expense as well as any other relevant equitable
considerations; provided, that in no event shall any contribution by a Holder
under this Subsection 1.8(d) exceed the net proceeds from the offering received
by such Holder. The relative fault of the indemnifying party and of the
indemnified party shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission to state a material fact relates to information supplied by the
indemnifying party or by the indemnified party and the parties' relative intent,
knowledge, access to information, and opportunity to correct or prevent such
statement or omission.


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<PAGE>


            (e) The obligations of the Company and Holders under this Section
1.8 shall survive the completion of any offering of Registrable Securities in a
registration statement under this Section 1, and otherwise.

        1.9 REPORTS UNDER SECURITIES EXCHANGE ACT OF 1934. With a view to making
available to the Holders the benefits of Rule 144 promulgated under the
Securities Act and any other rule or regulation of the SEC that may at any time
permit a Holder to sell securities of the Company to the public without
registration or pursuant to a registration on Form S-3, the Company agrees to:

            (a) make and keep public information available, as those terms are
understood and defined in SEC Rule 144, at all times after ninety (90) days
after the effective date of the first registration statement filed by the
Company for the offering of its securities to the general public so long as the
Company remains subject to the periodic reporting requirements under Sections 13
or 15(d) of the Exchange Act;

            (b) take such action, including the voluntary registration of its
Common Stock under Section 12 of the Exchange Act, as is necessary to enable the
Holders to utilize Form S-3 for the sale of their Registrable Securities, such
action to be taken as soon as practicable after the end of the fiscal year in
which the first registration statement filed by the Company for the offering of
its Common Stock to the general public is declared effective;

            (c) file with the SEC in a timely manner all reports and other
documents required of the Company under the Securities Act and the Exchange Act;
and

            (d) furnish to any Holder, so long as the Holder owns any
Registrable Securities, forthwith upon request (i) a written statement by the
Company that it has complied with the reporting requirements of SEC Rule 144 (at
any time after ninety (90) days after the effective date of the first
registration statement filed by the Company), the Securities Act and the
Exchange Act (at any time after it has become subject to such reporting
requirements), or that it qualifies as a registrant whose securities may be
resold pursuant to Form S-3 (at any time after it so qualifies), (ii) a copy of
the most recent annual or quarterly report of the Company and such other reports
and documents so filed by the Company, and (iii) such other information as may
be reasonably requested in availing any Holder of any rule or regulation of the
SEC which permits the selling of any such securities without registration or
pursuant to such form.

        1.10 ASSIGNMENT OF REGISTRATION RIGHTS. The rights to cause the Company
to register Registrable Securities pursuant to this Section 1 may be assigned
(but only with all related obligations) by a Holder to a transferee or assignee
of at least 10,000 shares of such securities, provided the Company is, within a
reasonable time after such transfer, furnished with written notice of the name
and address of such transferee or assignee and the securities with respect to
which such registration rights are being assigned; and provided, further, that
such assignment shall be effective only if immediately following such transfer
the further disposition of such securities by the transferee or assignee is
restricted under the Securities Act. For the purposes of determining the number
of shares of Registrable Securities held by a transferee or assignee, the
holdings of transferees and assignees of a partnership who are partners or
retired partners of such partnership (including spouses and ancestors, lineal
descendants and siblings of such partners or


                                       7
<PAGE>


spouses who acquire Registrable Securities by gift, will or intestate
succession) shall be aggregated together and with the partnership; provided that
all assignees and transferees who would not qualify individually for assignment
of registration rights shall have a single attorney-in-fact for the purpose of
exercising any rights, receiving notices or taking any action under Section 1.

        1.11   MARKET-STANDOFF AGREEMENT.

            (a) MARKET-STANDOFF PERIOD; AGREEMENT. In connection with the
initial public offering of the Company's securities and upon request of the
Company or the underwriters managing such offering of the Company's securities,
each Holder agrees not to sell, make any short sale of, loan, grant any option
for the purchase of, or otherwise dispose of any securities of the Company
(other than those included in the registration) without the prior written
consent of the Company or such underwriters, as the case may be, for such period
of time (not to exceed 180 days) from the effective date of such registration as
may be requested by the Company or such managing underwriters and to execute an
agreement reflecting the foregoing as may be requested by the underwriters at
the time of the Company's initial public offering. In addition, the Holder
agrees to be bound by similar restrictions, and to sign a similar agreement, in
connection with any one (but only one) additional registration statement filed
within 12 months after the closing date of the initial public offering, provided
that the duration of the market-standoff period with respect to such additional
registration shall not exceed 90 days from the effective date of such additional
registration.

            (b) LIMITATIONS. The obligations described in Section 1.11(a) shall
apply only if all officers and directors of the Company and all persons holding
1% or more of the Common Stock (on a fully-diluted basis) enter into similar
agreements, and shall not apply to a registration relating solely to employee
benefit plans, or to a registration relating solely to a transaction pursuant to
Rule 145 under the Securities Act.

            (c) STOP-TRANSFER INSTRUCTIONS. In order to enforce the foregoing
covenants, the Company may impose stop-transfer instructions with respect to the
securities of each Holder (and the securities of every other person subject to
the restrictions in Section 1.11(a)).

            (d) TRANSFEREES BOUND. Each Holder agrees that it will not transfer
securities of the Company unless each transferee agrees in writing to be bound
by all of the provisions of this Section 1.11, provided that this Section
1.11(d) shall not apply to transfers pursuant to a registration statement.

        1.12 TERMINATION OF REGISTRATION RIGHTS. No Holder shall be entitled to
exercise any right provided for in this Section 1 after the earlier of (i) five
(5) years following the consummation of a Qualified IPO, or (ii) with respect to
any Holder, such time following a Qualified IPO as the Holder owns less than 1%
of the Common Stock (on an as-converted, fully diluted basis) and Rule 144 or
another similar exemption under the Securities Act is available for the sale of
all of such Holder's shares during a three (3)-month period without
registration.

2.      COVENANTS OF THE COMPANY.


                                       8
<PAGE>


        2.1 RESERVATION OF COMMON STOCK. The Company will at all times reserve
and keep available, solely for issuance and delivery upon the conversion of the
Series D Stock, all Common Stock issuable from time to time upon such
conversion.

        2.2 COMPANY RIGHT OF FIRST OFFER. No holder of Series D Stock (or a
Permitted Transferee, as defined below) may sell or dispose, for value, of any
interest (a "Proposed Sale"), in any shares of Series D Stock (the "Shares"),
other than to a Permitted Transferee, unless such holder (the "Selling Holder")
delivers a notice (the "Notice") to the Company at least 10 business days prior
to the Proposed Sale setting forth the material terms and conditions of the
Proposed Sale including, without limitation, the number of Shares proposed to be
sold or transferred, and the form and amount of consideration to be paid.

            (a) At any time within 10 business days from the date such Notice is
received by the Company, the Company shall have the right to deliver to the
Selling Holder notice of its irrevocable commitment to purchase all (but not
less than all) of the Shares at the same price and upon the same terms as the
Selling Holder proposes to sell the Shares in the Notice. If the Company
delivers to the Selling Holder notice of such irrevocable commitment within such
10-business-day period, the Company and the Selling Holder agree to execute a
definitive agreement with respect to the Proposed Sale within 45 days from the
date of the Company's notice. If the Company does not deliver to the Selling
Holder notice of such irrevocable commitment within such 10-business-day period,
then the Selling Holder shall have 90 days from the end of such period within
which to sell the Shares upon terms not materially less favorable to the Selling
Holder than those terms set forth in the Notice. If such 90-day period shall
expire without such a sale having been consummated, or if the Selling Holder
proposes to sell the Shares upon terms materially less favorable to the Selling
Holder than those terms set forth in the Notice, the Selling Holder shall again
comply with the procedures set forth in this Section 2.2.

            (b) "Permitted Transferee" shall mean any affiliate (as such term is
defined in Rule 405 promulgated under the Securities Act), partner, member,
beneficiary (in the case of a trust), family member, trust for the benefit of
family members, or family limited partnership. This Section 2.2 shall not apply
to any transfer by gift, will, or intestacy, or to any assignment by operation
of law or merger.

            (c) Each certificate representing shares of Series D Stock shall
bear the following legend:

            "THE SHARES EVIDENCED HEREBY ARE SUBJECT TO CERTAIN RESTRICTIONS ON
            TRANSFER AS SET FORTH IN AN INVESTOR'S RIGHTS AGREEMENT BY AND AMONG
            THE COMPANY AND ITS STOCKHOLDERS (A COPY OF WHICH MAY BE OBTAINED
            FROM THE COMPANY), AND BY ACCEPTING ANY INTEREST IN SUCH SHARES THE
            PERSON ACCEPTING SUCH INTEREST SHALL BECOME BOUND BY ALL THE
            PROVISIONS OF SAID INVESTOR'S RIGHTS AGREEMENT."

        2.3 TERMINATION OF COVENANTS.


                                       9
<PAGE>


            (a) The covenants set forth in Sections 2.1 and 2.2 shall terminate
as to the Investor and be of no further force or effect (i) immediately prior to
the consummation of a Qualified IPO, or (ii) when the Company shall sell,
convey, or otherwise dispose of or encumber all or substantially all of its
property or business or merge into or consolidate with any other corporation
(other than a wholly-owned subsidiary corporation) or effect any other
transaction or series of related transactions in which more than fifty percent
(50%) of the voting power of the Company is disposed of, provided that this
subsection (ii) shall not apply to a merger effected exclusively for the purpose
of changing the domicile of the Corporation.

            (b) The covenants set forth in Sections 2.1 and 2.2 shall terminate
as to each Holder and be of no further force or effect when the Company first
becomes subject to the periodic reporting requirements of Sections 13 or 15(d)
of the Exchange Act, if this occurs earlier than the events described in Section
2.3(a) above.

3.      MISCELLANEOUS.

        3.1 SUCCESSORS AND ASSIGNS. Except as otherwise provided in this
Agreement, the terms and conditions of this Agreement shall inure to the benefit
of and be binding upon the respective permitted successors and assigns of the
parties (including transferees of any of the Series D Stock or any Common Stock
issued upon conversion thereof). Nothing in this Agreement, express or implied,
is intended to confer upon any party other than the parties hereto or their
respective successors and assigns any rights, remedies, obligations, or
liabilities under or by reason of this Agreement, except as expressly provided
in this Agreement.

        3.2 AMENDMENTS AND WAIVERS. Any term of this Agreement may be amended or
waived only with the written consent of the Company and the holders of 80% of
the Registrable Securities then outstanding. Any amendment or waiver effected in
accordance with this paragraph shall be binding upon each holder of any
Registrable Securities then outstanding, each future holder of all such
Registrable Securities, and the Company.

        3.3 NOTICES. Unless otherwise provided, any notice required or permitted
by this Agreement shall be in writing and shall be deemed sufficient upon
delivery, when delivered personally or by overnight courier or sent by telegram
or fax, or five days after being deposited in the U.S. mail, as certified or
registered mail, with postage prepaid, return receipt requested, and addressed
to the party to be notified at such party's address or fax number as set forth
below or on Exhibit A hereto or as subsequently modified by written notice.

        3.4 SEVERABILITY. If one or more provisions of this Agreement are held
to be unenforceable under applicable law, the parties agree to renegotiate such
provision in good faith. In the event that the parties cannot reach a mutually
agreeable and enforceable replacement for such provision, then (a) such
provision shall be excluded from this Agreement, (b) the balance of the
Agreement shall be interpreted as if such provision were so excluded and (c) the
balance of the Agreement shall be enforceable in accordance with its terms.

        3.5 GOVERNING LAW. This Agreement and all acts and transactions pursuant
hereto shall be governed, construed and interpreted in accordance with the laws
of the State of California, without giving effect to principles of conflicts of
laws.


                                       10
<PAGE>


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

        3.7 TITLES AND SUBTITLES. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

        3.8 AGGREGATION OF STOCK. All shares of the Series D Stock held or
acquired by affiliated entities or persons shall be aggregated together for the
purpose of determining the availability of any rights under this Agreement.

        3.9 VOTING AGREEMENT. The undersigned Investor hereby agrees to be bound
by the same terms and provisions of and to vote or act with respect its shares
in the same manner as the other stockholders of the Company as set forth in the
Voting Agreement, dated as of April 6, 2000, and entered into by and among the
Company, the holders of Common Stock of the Company, SmithKline Beecham, a
Pennsylvania corporation, Incyte Genomics, Inc., a Delaware corporation and the
holders of Series C Preferred Stock, which is attached hereto as Exhibit B,
(including voting for the election of directors specified therein).

                            [Signature Page Follows]


                                       11
<PAGE>


        The parties have executed this Investor's Rights Agreement as of the
date first above written.

COMPANY:                                           INVESTOR:


DIADEXUS, INC.                                     /s/ FUJIREBIO, INC.
                                                   -----------------------------
                                                   FUJIREBIO, INC.

By: /s/ PATRICK PLEWMAN                            By: T. Tokumitsu
   --------------------------                         --------------------------

                                                   Name: Tatsuo Tokumitsu
                                                        ------------------------
Address:                                                        (print)
3303 Octavius Drive
Santa Clara, CA 95054

                                                   Title: President and CEO
                                                         -----------------------
Fax:
408-496-5777
<PAGE>


                                    EXHIBIT A

                                    INVESTOR
<TABLE>
<CAPTION>
                   NAME/ADDRESS/FAX NO.          NO. OF SHARES
                   --------------------          -------------
                   <S>                           <C>
                   FUJIREBIO, INC.               20,833
</TABLE>