<PAGE>   1

                                                                    EXHIBIT 10.5

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AND
HAVE BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO, OR IN CONNECTION WITH,
THE SALE OR DISTRIBUTION THEREOF. NO SUCH SALE OR DISTRIBUTION MAY BE EFFECTED
WITHOUT AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF
COUNSEL IN A FORM SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT
REQUIRED UNDER THE SECURITIES ACT OF 1933



                                 DIADEXUS, INC.


              WARRANT FOR THE PURCHASE OF SHARES OF PREFERRED STOCK


                                  JUNE 1, 2000



                                                                  129,032 Shares


FOR VALUE RECEIVED, DIADEXUS, INC. a Delaware corporation ("the Company"),
hereby certifies that PRUDENTIAL SECURITIES INCORPORATED, or permitted assigns
thereof, is entitled to purchase from the Company, at any time or from time to
time prior to 5:00 p.m., New York City time, on that date which is five (5)
years from the date hereof, 129,032 fully paid and nonassessable shares of the
Series C Preferred Stock, par value $.01 per share ("Series C Preferred Stock"),
of the Company upon payment of the purchase price of $7.75 per share; each
subject to adjustment pursuant to the terms hereof. The voting powers,
preferences and relative, participating, optional and other special rights and
qualifications, limitations and restrictions of the Preferred Stock are set
forth in the Certificate of Incorporation of the Company and a Certificate of
Amendment thereof which were filed with the Secretary of State of the State of
Delaware on April 3, 2000, and April 6, 2000, respectively, and copies of which
have been delivered to the Holder.

Hereinafter, (i) the preferred stock referred to above, together with any other
equity securities which may be issued by the Company in exchange for, upon
conversion of or otherwise with respect thereto or in substitution therefor, is
referred to as the

<PAGE>   2

"Preferred Stock," (ii) the shares of the Preferred Stock purchasable hereunder
or under any other Warrant (as hereinafter defined) are referred to as the
"Warrant Shares," (iii) the aggregate purchase price payable hereunder for the
Warrant Shares is referred to as the "Aggregate Warrant Price," (iv) the price
payable hereunder for each of the Warrant Shares is referred to as the "Per
Share Warrant Price," (v) this Warrant and all warrants hereafter issued in
exchange or substitution for this Warrant are referred to as the "Warrants" and
(vi) the holder of this Warrant is referred to as the "Holder" and the holders
of this Warrant and all other Warrants are referred to as the "Holders."

The Per Share Warrant Price is subject to adjustment as hereinafter provided; in
the event of any such adjustment, the number of Warrant Shares shall be adjusted
by dividing the Aggregate Warrant Price by the Per Share Warrant Price in effect
immediately after such adjustment.

1.      Exercise of Warrant.

        (a)     This Warrant may be exercised, in whole at any time or in part
                from time to time, prior to its expiration as set forth above by
                the Holder by sending written notice (an "Exercise Notice") to
                the Company. The Holder shall be obligated to surrender of this
                Warrant to the Company (with the subscription form at the end
                hereof duly executed) on or prior to the third business day
                following the date that the Exercise Notice was duly sent at the
                address set forth in Subsection 11 hereof, together with proper
                payment of the Aggregate Warrant Price, or the proportionate
                part thereof if this Warrant is exercised in part. Payment for
                Warrant Shares shall be made by cashier's check or by wire
                transfer of funds. An Exercise Notice shall be deemed to be duly
                sent: (a) if sent by overnight courier, the date when delivered
                by the Holder to Federal Express or other reliable courier or if
                by hand, on the date delivered, or (b) if sent by telecopy, upon
                receipt by the sender of an acknowledgment or transmission
                report generated by the machine from which the telecopy was sent
                indicating that the telecopy was sent in its entirety to the
                recipient's telecopy number. Upon any exercise of this Warrant
                following the earlier of (a) a public offering of the common
                stock of the Company (the "Common Stock"), (b) the consolidation
                or merger of the Company into any other entity following which
                the Company shall not be the continuing or surviving corporation
                of such consolidation or merger, (c) the consolidation or merger
                of any other entity into the Company following which the Company
                shall be the



                                       2
<PAGE>   3

                continuing or surviving entity but, in connection with such
                consolidation or merger, the Preferred Stock shall be changed
                into or exchanged for stock or other securities of any other
                entity, (d) the transfer of all or substantially all of the
                properties or assets of the Company to any other entity, or (e)
                the sale (other than in an original issuance transaction) of
                more than 25% of the outstanding capital stock of the Company to
                any other person, the Holder may in the Exercise Notice, at its
                option, instruct the Company, its successor or any entity into
                which the Preferred Stock shall be convertible, to apply to the
                payment required by this Section 1 such number of the shares of
                Preferred Stock otherwise issuable to such Holder upon such
                exercise as shall be specified in such Exercise Notice, in which
                case an amount equal to the excess of the Market Price of such
                specified number of shares on the date of the exercise over the
                portion of the payment required by this Section 1 attributable
                to such shares shall be deemed to have been paid to the Company
                and the number of shares issuable upon such exercise shall be
                reduced by such specified number. For the purpose of this
                warrant agreement, the "Market Price" of a share of Preferred
                Stock or other securities shall mean the closing price of a
                share of Preferred Stock or other security on the date that the
                Exercise Notice is duly sent (or if such day is not a trading
                day, on the first trading day thereafter) on the principal
                national securities exchange on which the shares of Preferred
                Stock or securities are listed or admitted to trading or, if not
                listed or admitted to trading on any national securities
                exchange, the average of the reported bid and asked prices on
                such trading day in the over-the-counter market as furnished by
                the National Quotation Bureau, Inc., or, if such firm is not
                then engaged in the business of reporting such prices, as
                furnished by any similar firm then engaged in such business
                selected by the Company, or, if there is no such firm, as
                furnished by any member of the National Association of
                Securities Dealers, Inc. selected by the Company or, if the
                shares of Preferred Stock or securities are not publicly traded,
                the Market Price for such day shall be the fair market value
                thereof determined jointly by the Company and the Holder of this
                Warrant; provided, however, that if such parties are unable to
                reach agreement within a reasonable period of time, the Market
                Price shall be determined in good faith by the independent
                investment banking firm selected jointly by the Company and the
                Holder of this Warrant or, if that selection cannot be made
                within 15 days, by an independent investment banking firm
                selected by the American Arbitration Association in accordance
                with its rules;



                                       3
<PAGE>   4

                provided, further, that if the Common Stock is publicly traded,
                the Market Price of the Preferred Stock shall be equal to the
                Market Price of the Common Stock multiplied by the number of
                shares of Common Stock or other securities issuable upon
                conversion of a share of Preferred Stock; and, provided,
                further, that in the event of a transaction of the type
                described in clause, (b), (c), (d) or (e) above, the Market
                Price of the Preferred Stock shall be equal to the value of the
                consideration received or to be received by the holders thereof
                in such transaction.

                If this Warrant is exercised in part, this Warrant must be
                exercised for a number of whole shares of the Preferred Stock,
                and the Holder is entitled to receive a new Warrant covering the
                Warrant Shares which have not been exercised and setting forth
                the proportionate part of the Aggregate Warrant Price applicable
                to such Warrant Shares. Upon such surrender of this Warrant, the
                Company will (a) issue a certificate or certificates in the name
                of the Holder for the largest number of whole shares of the
                Preferred Stock to which the Holder shall be entitled and, if
                this Warrant is exercised in whole, in lieu of any fractional
                share of the Preferred Stock to which the Holder shall be
                entitled, pay to the Holder, cash in an amount equal to the fair
                value of such fractional share (determined in such reasonable
                manner as the Board of Directors of the Company shall
                determine), and (b) deliver the other securities and properties
                receivable upon the exercise of this Warrant, or the
                proportionate part thereof if this Warrant is exercised in part,
                pursuant to the provisions of this Warrant.

                Each exercise of this Warrant shall be deemed to have been
                effected immediately prior to the close of business on the
                business day on which this Warrant shall have been surrendered
                to the Company as provided in this Section 1, and at such time
                the person or persons in whose name or names any certificate or
                certificates for shares of Preferred Stock shall be issuable
                upon such exercise shall be deemed to have become the holder or
                holders of record thereof.

        (b)     The Company will, at the time of each exercise of this Warrant,
                upon the request of the Holder, acknowledge in writing its
                continuing obligation to afford to the Holder all rights
                (including, without limitation, any rights to registration of
                the shares of underlying Common Stock) to which the Holder shall
                continue to be entitled after



                                       4
<PAGE>   5

                such exercise in accordance with the terms of this Warrant,
                provided, that if the Holder shall fail to make any such
                request, such failure shall not affect the continuing obligation
                of the Company to afford such rights to the Holder.

2.      Reservation of Warrant Shares.

        The Company agrees that, prior to the expiration of this Warrant, the
        Company will at all times (a) have authorized and in reserve, and will
        keep available, solely for issuance or delivery upon the exercise of
        this Warrant, Warrant Shares, Common Stock and other securities and
        properties as from time to time shall be receivable upon the exercise of
        this Warrant, free and clear of all restrictions on sale or transfer and
        free and clear of all preemptive or similar contractual rights, (b) if
        the Series C Preferred Stock, Common Stock or other securities
        receivable upon exercise of this Warrant is authorized for quotation on
        the Nasdaq National Market ("NASDAQ") (or authorized for listing on a
        national securities exchange), keep the Warrant Shares, Common Stock or
        other securities authorized for quotation on the NASDAQ (or authorized
        for listing on the national securities exchange upon which the Common
        Stock is then listed) upon notice of issuance, and (c) take or refrain
        from taking, as applicable, such actions as are required to protect and
        preserve in good faith the value of this Warrant to the Holder.

3.      Protection Against Dilution.

        (a)     In case the Company shall hereafter (i) declare a dividend or
                make a distribution on its capital stock in shares of Preferred
                Stock, (ii) subdivide its outstanding shares of Preferred Stock
                into a greater number of shares, (iii) combine its outstanding
                shares of Preferred Stock into a smaller number of shares or
                (iv) issue by reclassification of its Preferred Stock any shares
                of capital stock of the Company, the Per Share Warrant Price and
                the number and kind of shares of Preferred Stock receivable upon
                exercise of this Warrant in effect at the time of the record
                date for such dividend or of the effective date of such
                subdivision, combination or reclassification shall be
                proportionately adjusted so that the Holder of any Warrant upon
                the exercise hereof shall be entitled to receive the number and
                kind of shares of Preferred Stock or other capital stock of the
                Company which the Holder would have received had it exercised
                such Warrant immediately prior thereto. An adjustment made
                pursuant to this Subsection 3(a) shall become



                                       5
<PAGE>   6

                effective immediately after the record date in the case of a
                dividend or distribution and shall become effective immediately
                after the effective date in the case of a subdivision,
                combination or reclassification. If, as a result of an
                adjustment made pursuant to this Subsection 3(a), the Holder of
                any Warrant thereafter surrendered for exercise shall become
                entitled to receive shares of two or more classes of capital
                stock or shares of Preferred Stock and other capital stock of
                the Company, the Board of Directors (whose determination shall
                be conclusive and shall be described in a written notice to the
                Holder of any Warrant promptly after such adjustment) shall
                determine the allocation of the adjusted Per Share Warrant Price
                between or among shares of such classes of capital stock or
                shares of Preferred Stock and other capital stock.

        (b)     If all of the Preferred Stock is redeemed or converted solely
                into shares of Common Stock, then this Warrant shall
                automatically become exercisable for that number of shares of
                Common Stock equal to the number of shares of Common Stock that
                would have been received if this Warrant had been exercised in
                full and the shares of Preferred Stock received thereupon had
                been simultaneously converted into shares of Common Stock
                immediately prior to such event, and the Per Share Warrant Price
                shall be automatically adjusted to equal the number obtained by
                dividing (i) the Aggregate Warrant Price by (ii) the number
                shares of Common Stock for which this Warrant is exercisable
                immediately after such redemption or conversion; provided that
                the number of shares and exercise price shall remain subject to
                further adjustment as may from time to time thereafter become
                applicable as provided in this Section 3.

        (c)     In the event that the Company shall any time prior to the full
                exercise of this Warrant declare a dividend or otherwise
                distribute to holders of Preferred Stock any assets, property,
                rights, evidences of indebtedness, securities, whether issued by
                the Company or by another, or any other thing of value, the
                Holder shall thereafter be entitled, in addition to the Warrant
                Shares or other securities and property receivable upon the
                exercise of this Warrant, to receive, upon the exercise of this
                Warrant, the same property, assets, rights, evidence of
                indebtedness, securities or other thing of value that they would
                have been entitled to receive at the time of such dividend or
                distribution as if the Warrant had been exercised immediately
                prior to such dividend or distribution.



                                       6
<PAGE>   7

        (d)     In case the Company after the date hereof (a) shall consolidate
                with or merge into any other entity and shall not be the
                continuing or surviving corporation of such consolidation or
                merger, or (b) shall permit any other entity to consolidate with
                or merge into the Company and the Company shall be the
                continuing or surviving entity but, in connection with such
                consolidation or merger, the Preferred Stock shall be changed
                into or exchanged for stock or other securities of any other
                entity or cash or any other property, or (c) shall transfer all
                or substantially all of its properties or assets to any other
                entity, or (d) shall effect a capital reorganization or
                reclassification of the Preferred Stock or other securities of
                the Company ((a) - (d) being collectively referred to as
                "Transactions"), the Holder of this Warrant shall have the right
                thereafter to convert such Warrant into the kind and amount of
                securities, cash or other property which he would have received
                or have been entitled to receive immediately after such
                Transaction had this Warrant been converted immediately prior to
                the effective date of such Transaction and in any such case, if
                necessary, appropriate adjustment shall be made in the
                application of the provisions set forth in this Section 3 with
                respect to the rights and interests thereafter of the Holder of
                this Warrant to the end that the provisions set forth in this
                Section 3 shall thereafter correspondingly be made applicable,
                as nearly as may be reasonable, in relation to any shares of
                stock or other securities or, in relation to any shares of stock
                or other securities or property thereafter deliverable on the
                exercise of this Warrant. The above provisions of this
                Subsection 3(c) shall similarly apply to successive
                Transactions. The issuer of any shares of stock or other
                securities or property thereafter deliverable on the exercise of
                this Warrant shall be responsible for all of the agreements and
                obligations of the Company hereunder. Notice of any such
                Transaction and of said provisions so proposed to be made, shall
                be mailed to the Holders of the Warrants not less than 30 days
                prior to such event.

                Notwithstanding the foregoing, if the Holder so designates in a
                notice given to the Company on or before the date immediately
                preceding the date of the consummation of such Transaction, the
                Holder shall be entitled to receive the highest amount of
                securities, cash or other property to which such Holder would
                actually have been entitled as a shareholder if the Holder had
                exercised this Warrant immediately prior to such Transaction.



                                       7
<PAGE>   8

        (e)     No adjustment in the Per Share Warrant Price shall be required
                unless such adjustment would require an increase or decrease of
                at least 1% of the then existing Per Share Warrant Price;
                provided, however, that any adjustments which by reason of this
                Subsection 3(d) are not required to be made shall be carried
                forward and taken into account in any subsequent adjustment;
                provided further, however, that adjustments shall be required
                and made in accordance with the provisions of this Section 3
                (other than this Subsection 3(d)) not later than such time as
                may be required in order to preserve the tax-free nature of a
                distribution to the Holder of this Warrant or Preferred Stock
                issuable upon exercise hereof. All calculations under this
                Section 3 shall be made to the nearest cent or to the nearest
                share, as the case may be. Anything in this Section 3 to the
                contrary notwithstanding, the Company shall be entitled to make
                such reductions in the Per Share Warrant Price, in addition to
                those required by this Section 3, as it in its discretion shall
                deem to be advisable in order that any stock dividend,
                subdivision of shares or distribution of rights to purchase
                stock or securities convertible or exchangeable for stock
                hereafter made by the Company to its shareholders shall not be
                taxable.

        (f)     No adjustments shall be made under this Section 3 if the event
                requiring an adjustment results in an adjustment of the
                Conversion Price of the Preferred Stock under the Company's
                Certificate of Incorporation, as amended.

        (g)     In case any event shall occur as to which the provisions of this
                Section 3 are not strictly applicable but the failure to make
                any adjustment would not fairly protect the purchase rights
                represented by this Warrant in accordance with the essential
                intent and principles of such sections, then, in each such case,
                the Company shall appoint a firm of independent certified public
                accountants of recognized national standing (which may be the
                regular auditors of the Company), which shall give their opinion
                upon the adjustment, if any, on a basis consistent with the
                essential intent and principles established in this Section 3,
                necessary to preserve, without dilution, the purchase rights
                represented by this Warrant. Upon receipt of such opinion, the
                Company will promptly mail a copy thereof to the holder of this
                Warrant and shall make the adjustments described therein.



                                       8
<PAGE>   9

        (h)     Whenever the Per Share Warrant Price is adjusted as provided in
                this Section 3 and upon any modification of the rights of a
                Holder of Warrants in accordance with this Section 3, the
                Company shall promptly provide a certificate of the chief
                financial officer of the Company setting forth the Per Share
                Warrant Price and the number of Warrant Shares after such
                adjustment or the effect of such modification, a brief statement
                of the facts requiring such adjustment or modification and the
                manner of computing the same and cause copies of such
                certificate to be mailed to the Holders of the Warrants.

        (i)     If the Board of Directors of the Company shall declare any
                dividend or other distribution with respect to the Preferred
                Stock, the Company shall mail notice thereof to the Holders of
                the Warrants not less than 15 days prior to the record date
                fixed for determining shareholders entitled to participate in
                such dividend or other distribution.

4.      Fully Paid Stock; Taxes.

        The Company will take all such actions as may be necessary to assure
        that the shares of the Preferred Stock represented by each and every
        certificate for Warrant Shares delivered on the exercise of this Warrant
        shall, at the time of such delivery, be validly issued and outstanding,
        fully paid and nonassessable, and not subject to preemptive rights, and
        the Company will take all such actions as may be necessary to assure
        that the par value or stated value, if any, per share of the Preferred
        Stock is at all times equal to or less than the then Per Share Warrant
        Price.

        The Company further covenants and agrees that it will pay, when due and
        payable, any and all Federal and state stamp, original issue or similar
        taxes which may be payable in respect of the issue of any Warrant Share
        or certificate therefor.

5.      Registration Rights.

        The Holder or the Holders of the Warrant shall have the registration
        rights set forth in Section 1 of the Investors' Rights Agreement
        ("Investors' Rights Agreement") among the Company and the purchasers of
        Series C Preferred Stock with respect to the Common Stock underlying the
        Warrant Shares, as if such Holder(s) was an Investor (as defined in the
        Investors' Rights Agreement).

6.      Ancillary Agreements.



                                       9
<PAGE>   10

        Upon any issuance of shares of Preferred Stock upon exercise of this
        Warrant, the Holder will become a party to, will be bound by and will
        have the rights set forth under (without the need for any written
        assumption by the Holder of) that certain Investors' Rights Agreement
        and that certain Voting Agreement dated as of April 6, 2000 in all
        respects as an "Investor" thereunder.

7.      Securities Unregistered; Legend.

        This Warrant is issued in reliance upon the Holder's representations to
        the Company, which by the acceptance of this Warrant the Holder hereby
        confirms, that (i) the Holder is an "accredited investor" as defined in
        Regulation D promulgated by the Securities and Exchange Commission under
        the Securities Act of 1933, as amended (the "Securities Act"), and (ii)
        the Warrant and the Warrant Shares to be acquired by the Holder will be
        acquired for investment for the Holder's own account, not as a nominee
        or agent, and not with a view to the resale or distribution of any part
        thereof, and that the Holder has no present intention of selling,
        granting any participation in, or otherwise distributing the same. The
        Warrant has not been, and upon their issuance the Warrant Shares will
        not be, registered under the Securities Act, by reason of a specific
        exemption from the registration provisions of the Securities Act which
        depends upon, among other things, the bona fide nature of the Holder's
        investment intent and the accuracy of the Holder's representations as
        expressed herein. The Warrant is, and upon issuance the Warrant Shares
        will be, "restricted securities" under applicable U.S. federal and state
        securities laws and pursuant to these laws, the Holder must hold such
        securities indefinitely unless they are registered with the Securities
        and Exchange Commission and qualified by state authorities, or an
        exemption from such registration and qualification requirements is
        available. If an exemption from registration or qualification is
        available, it may be conditioned on various requirements including, but
        not limited to, the time and manner of sale, the holding period for the
        Securities, and on requirements relating to the Company which are
        outside of the Holder's control, and, except as otherwise provided in
        this Warrant or the Investor Rights Agreement which the Company is under
        no obligation and may not be able to satisfy. The Warrant Shares, upon
        issuance, will bear the following legend, in addition to any applicable
        legends required by state blue sky laws and any legends required by the
        Investors' Rights Agreement or Voting Agreement:

        "THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
        UNDER THE SECURITIES ACT OF 1933, AND



                                       10
<PAGE>   11

        HAVE BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO, OR IN
        CONNECTION WITH, THE SALE OR DISTRIBUTION THEREOF. NO SUCH SALE OR
        DISTRIBUTION MAY BE EFFECTED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT
        RELATED THERETO OR AN OPINION OF COUNSEL IN A FORM SATISFACTORY TO THE
        COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT
        OF 1933."

8.      Loss, etc., of Warrant.

        Upon receipt of evidence satisfactory to the Company of the loss, theft,
        destruction or mutilation of this Warrant, and of indemnity reasonably
        satisfactory to the Company, if lost, stolen or destroyed, and upon
        surrender and cancellation of this Warrant, if mutilated, the Company
        shall execute and deliver to the Holder a new Warrant of like date,
        tenor and denomination.

9.      Warrant Holder Not Stockholder.

        Except as otherwise provided herein, this Warrant does not confer upon
        the Holder any right to vote or to consent to or receive notice as a
        stockholder of the Company, as such, in respect of any matters
        whatsoever, or any other rights or liabilities as a stockholder, prior
        to the exercise hereof.

10.     Amendment.

        These Warrants may be amended only by written mutual agreement of the
        Company and the Holders of a majority of the then outstanding Warrants.

11.     Communication.

        No notice or other communication under this Warrant shall be effective
        unless, but any notice or other communication shall be effective and
        shall be deemed to have been given if, the same is in writing and is
        mailed by first-class mail, postage prepaid, addressed as set forth
        below.

        If to the Company:    diaDexus, Inc.
                              3303 Octavius Drive
                              Santa Clara, CA  95054
                              Attn:Corporate Secretary

        or such other address as the Company has designated in writing to the
        Holder.



                                       11
<PAGE>   12

        If to the Holder:     Prudential Securities Incorporated
                              1751 Lake Cook Road
                              Deerfield, Illinois  60015
                              Attention:  D. Theodore Berghorst
                              Managing Director and Group Head

        or such other address as the Holder has designated in writing to the
        Company.

12.     Headings.

        The headings of this Warrant have been inserted as a matter of
        convenience and shall not affect the construction hereof.

13.     Applicable Law.

        This Warrant shall be governed by and construed in accordance with the
        laws of the State of California without giving effect to the principles
        of conflicts of laws thereof.

14.     Assignment.

        The Holder may assign or transfer this Warrant in whole or in part by
        completing and delivering to the Company the applicable document of
        assignment, duly executed, in the form attached hereto. Upon any such
        assignment or transfer, the term "Holder" shall be deemed to include any
        such assignee or transferee of the original Holder.

15.     Severability.

        If one or more provisions of this Warrant are held to be unenforceable
        under applicable law, such provision shall be excluded from this Warrant
        and the balance of the Warrant shall be interpreted as if such
        provisions were so excluded and the balance shall be enforceable in
        accordance with its terms.



                                       12
<PAGE>   13

IN WITNESS WHEREOF, diaDexus, Inc. has caused this Warrant to be signed by its
Chief Executive Officer and its corporate seal to be hereunto affixed and
attested by its Secretary this 11th day of October 2000.



                                           /s/ Patrick Plewman
                                           ------------------------------------
                                           Name: Patrick Plewman
                                           Title: President and CEO

ATTEST:

/s/ Sharon Tetlow
----------------------------------
Sharon Tetlow, Assistant Secretary

[Corporate Seal]



                                       13
<PAGE>   14

                                  SUBSCRIPTION



The undersigned, ___________________, pursuant to the provisions of the
foregoing Warrant, hereby agrees to subscribe for and purchase __________ shares
of the Series C Preferred Stock of diaDexus, Inc. covered by said Warrant, and
makes payment therefor in full at the price per share provided by said Warrant
by [delivering a cashier's check/wire transfer in the amount of
$___________][applying ___________ shares to such purchase].


Dated:                                 Signature:
       ----------------------                     ------------------------------

                                       Address:
                                                --------------------------------

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



                                       14
<PAGE>   15

                                   ASSIGNMENT



FOR VALUE RECEIVED diaDexus, Inc. hereby sells, assigns and transfers unto
_______________ the foregoing Warrant and all rights evidenced thereby, and does
irrevocably constitute and appoint ___________________, attorney, to transfer
said Warrant on the books of diaDexus, Inc.


Dated:                                 Signature:
       ----------------------                     ------------------------------

                                       Address:
                                                --------------------------------

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



                                       15
<PAGE>   16

                               PARTIAL ASSIGNMENT



FOR VALUE RECEIVED _______________ hereby assigns and transfers unto
_______________ the right to purchase _________ shares of the Series C Preferred
Stock of diaDexus, Inc. by the foregoing Warrant, and a proportionate part of
said Warrant and the rights evidenced hereby, and does irrevocably constitute
and appoint _____________________, attorney, to transfer that part of said
Warrant on the books of diaDexus, Inc.


Dated:                                 Signature:
       ----------------------                     ------------------------------

                                       Address:
                                                --------------------------------

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



                                       16