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                                                                   EXHIBIT 10.22

             AMENDMENT NO. 4 TO COLLABORATION AND LICENSE AGREEMENT

               This amendment (the "Amendment") is made this 17th day of
February, 2000, among SmithKline Beecham Corporation, a Pennsylvania corporation
with offices at One Franklin Plaza, Philadelphia, Pennsylvania 19101, USA
(hereinafter "SB Corporation"); SmithKline Beecham plc, an English corporation
with offices at New Horizons Court, Brentford, Middlesex, TW8 9EP, England
(hereinafter "SB plc"), diaDexus LLC, a Delaware limited liability company with
offices at 3303 Octavius Drive, Santa Clara, CA 95054 (hereinafter "diaDexus")
and Incyte Pharmaceuticals, Inc, a Delaware corporation with offices at 3174
Porter Drive, Palo Alto, CA 94304 (hereinafter "Incyte").

                                  WITNESSETH:

        WHEREAS, SB Corporation, SB plc, diaDexus and Incyte are parties to that
certain Collaboration and License Agreement dated September 2, 1997, as amended
(the "Collaboration Agreement");

        WHEREAS, pursuant to the terms of the Collaboration Agreement, diaDexus
granted Incyte, SB Corporation and SB plc certain beneficial rights that relate
to inventions and discoveries made by diaDexus in the field of Rx/Other as
defined in the Collaboration Agreement (the "diaDexus Rights");

        WHEREAS, SB Corporation, SB plc and Incyte desire to assign certain of
the diaDexus Rights to diaDexus;

        WHEREAS, pursuant to the terms of the Collaboration Agreement, Incyte
granted diaDexus certain beneficial rights that relate to Incyte Diagnostic IP
(as defined in the Collaboration Agreement) and pursuant to the terms of the
Incyte Database Agreements (as defined in the Collaboration Agreement) Incyte
granted diaDexus certain beneficial rights that relate to Incyte Database
Know-How and Incyte Database Technology (each as defined in the Collaboration
Agreement);

        WHEREAS, SB Corporation, SB plc, diaDexus and Incyte desire to delete
all references to Incyte Diagnostic Know-How, Incyte Diagnostic Patents, and
Incyte Diagnostic IP (each as defined in the Collaboration Agreement) in the
Collaboration Agreement, and otherwise amend the Collaboration Agreement in
accordance with the terms and conditions of this Amendment; and

        WHEREAS, Incyte and diaDexus desire to replace the Incyte Database
Agreements with a new expanded database agreement to be entered as of the date
of this Amendment.

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        NOW, THEREFORE, in consideration of the covenants and obligations
expressed herein and other good and valuable consideration, the receipt and
adequacy of which is hereby acknowledged, the parties agree as follows:

1.      DEFINITIONS.

        1.1 All capitalized words used herein shall have the meaning set forth
in the Collaboration Agreement, except as expressly otherwise defined herein.

2.      Specific Provisions.

        2.1 All references in the Collaboration Agreement to Incyte Diagnostic
Know-How, Incyte Diagnostic Patents, and Incyte Diagnostic IP are deleted in
their entirety. diaDexus acknowledges it has no rights in and to Incyte
Diagnostic Know-How, Incyte Diagnostic Patents, and/or Incyte Diagnostic IP
pursuant to the terms of the Collaboration Agreement. As of the date of this
Amendment, diaDexus represents and warrants to SB that it has not received any
Incyte Diagnostic Know-How, Incyte Diagnostic Patents, and/or Incyte Diagnostic
IP from Incyte pursuant to the terms of the Collaboration Agreement.

        2.2 Paragraph 5.6.2(a) is hereby deleted in its entirety and replaced
with the following:

        5.6.2 Rx/Other

                (a) Subject to subparagraph (b) below and Paragraph 5.6.5(b),
                diaDexus grants to SB an exclusive world-wide license(s), with
                the right to sublicense, under diaDexus IP generated during the
                Extended License Period to Make, Have Made, Use, and Sell any
                and all products and processes in the field of Rx/Other,
                provided such diaDexus IP is based on the use of or derived by
                use of SB Diagnostic IP. During the Extended License Period,
                upon request, diaDexus shall provide to SB, as may be reasonably
                available to it, research reagents developed by or on behalf of
                diaDexus from the use of SB Diagnostic IP. SB shall reimburse
                diaDexus for the actual costs of producing such reagents.

        2.3 Paragraph 5.6.2(b) is amended by deleting "and Incyte" from line 3.

        2.4 Paragraph 5.6.2(c) is hereby deleted in its entirety.

        2.5 diaDexus represents and warrants to SB that, as of the date of this
Amendment, it has disclosed to SB and Incyte all diaDexus IP which is
potentially useful in the Rx/Other field which is reasonably available and
transferable in accordance with Section 9.3.7 of the Collaboration Agreement.

        2.6 Paragraph 6.2 is hereby deleted in its entirety.

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        2.7 For purposes of clarity, the following new Paragraph 14.6.3 is
hereby added:

        14.6.3. Freedom From Suit - Research. In the event diaDexus or its
        sublicensee(s) develops technology based on the use of or derived by the
        use of SB Diagnostic IP as targets in the development of ligands and
        said technology, or aspects thereof, is ultimately claimed in patents
        owned or controlled by diaDexus or its sublicensee(s), diaDexus, or its
        sublicensee(s), as the case may be, agrees not to sue or bring any
        action in any court or administrative agency or any other government
        authority alleging infringement of said patents as a result of
        activities of SB or its affiliates or (sub)licensee(s) in their internal
        research which would constitute an infringement of said patents, and
        further, diaDexus or its sublicensee(s) as the case may be) agrees to
        extend such freedom from suit or action to further (sub)licensee(s)s of
        SB, its affiliates, or licensees.

3.      EFFECT.

        3.1 The Collaboration Agreement is hereby amended retroactively as of
the original date of the Collaboration Agreement, September 2, 1997, and is
amended in accordance with Paragraph 19.6 of the Collaboration Agreement. This
Amendment shall become effective upon the effectiveness of the new Collaborative
Agreement between Incyte and diaDexus granting diaDexus LifeSeq Gold and
PathoSeq access until September 2, 2003.

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        3.2 Except as expressly set forth herein, all other terms and conditions
of the Collaboration Agreement shall remain unaffected by this Amendment.

        IN WITNESS WHEREOF, the parties, through their authorized officers, have
executed this Amendment as of the date first written above.

SMITHKLINE BEECHAM CORPORATION

By: /s/ DONALD Y. PARMAN
   -------------------------------

Its: Secretary
    -------------------------------

SMITHKLINE BEECHAM PLC

By: /s/ DONALD Y. PARMAN
   -------------------------------

Its: Attorney-in-Fact
    -------------------------------

DIADEXUS LLC

By: /s/ P. PLEWMAN
   -------------------------------

Its: President & COO
    -------------------------------

INCYTE PHARMACEUTICALS, INC.

By: [SIGNATURE ILLEGIBLE]
   -------------------------------

Its: President & CFO
    -------------------------------

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                                                                   EXHIBIT 10.23

March 30, 2000

Incyte Pharmaceuticals, Inc.
SmithKline Beecham plc
SmithKline Beecham Corporation

Re:  Collaboration and License Agreement between and among SmithKline Beecham
     plc and SmithKline Beecham Corporation (collectively, "SB"), Incyte
     Pharmaceuticals, Inc. ("Incyte"), and diaDexus, LLC ("diaDexus") dated
     September 2, 1997 as amended (the "Agreement")

Ladies and Gentlemen:

     This letter is intended to clarify and confirm the understandings of the
parties to the Agreement in respect of certain change of control transactions
involving diaDexus. In particular, the parties hereby confirm that,
notwithstanding Section 19.2 or any other provision of the Agreement, the
Agreement shall continue in full force and effect and be binding upon and
assignable (either expressly or by operation of law) to any successor in
interest of diaDexus upon any merger, consolidation, reorganization or
acquisition of stock or assets or similar transaction affecting all or
substantially all of the assets or voting control of diaDexus (collectively
"Merger"), without the need for any consent of the parties to the Agreement;
provided, however, that in the event of a Merger (i) in which the stockholders
of record as constituted immediately prior to such Merger will, immediately
after such Merger (by virtue of securities issued in connection with such
Merger), hold less than 50% of the voting power of the surviving entity or other
successor, (ii) occurring prior to September 2, 2001, and (iii) in which the
surviving entity or other successor in interest to diaDexus is a Pharmaceutical
Company (as defined below) (a "Restricted Merger"), SB's obligations pursuant to
Sections 4.2-4.5, 4.6.1, 4.6.3, 4.8, and 9.1 of the Agreement shall immediately
terminate; and further provided that as of the closing of Restricted Merger (the
"Merger Date") and until September 2, 2001:

     (1)  SB grants to diaDexus an exclusive, world-wide license under SB
          Diagnostic Patents with the right to sublicense pursuant to Section
          4.7, to Make, Have Made, Use, and Sell cDx Homebrews and cDx Kits in
          the field of Class I Dx Tests, Class II Dx Tests, all for which
          diaDexus has filed a Research Plan pursuant to Section 1.1, subject to
          all of the terms and conditions of the Agreement; and

     (2)  SB grants to diaDexus a non-exclusive, world-wide license under SB
          Diagnostic Patents with the right to sublicense pursuant to Section
          4.7, to Make, Have Made, Use, and Sell rDx Services and rDx Kits in
          the field of Class I Dx, all for which diaDexus has filed a Research
          Plan pursuant to Section 1.1, subject to all of the terms and
          conditions of the Agreement; and

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        (iii) after the Merger Date, SB shall not be required to disclose any
              licensed SB Diagnostic Patents to diaDexus unless requested to do
              so by diaDexus pursuant to Section 14.2 and the text of such SB
              Diagnostic Patent has become published.

        For purposes of this letter agreement, "Pharmaceutical Company" shall
mean any third party that performs ethical pharmaceuticals research and
development activities or an affiliate (as defined in Rule 405 under the
Securities Act of 1933, as amended) of such a third party.

        For each cDx Kit, rDx Service and rDx Kits that is based on or derived
from SB Diagnostic IP, diaDexus or its licenses, as appropriate, shall provide
SB with non-exclusive access to such Kits or Services on Commercially reasonable
terms.

        The parties additionally agree to delete (i) Sections 7.1 and 7.2 of the
Agreement and (ii) to terminate all of Incyte's obligations with respect to any
Incyte Technology IP, Incyte Technology Know-How and Incyte Technology Patents
to diaDexus.

        Capitalized terms used but not otherwise defined herein shall have the
meanings given them in the Agreement.

        The parties hereby acknowledge and agree that, as of the date of this
letter agreement, this letter agreement is a binding and enforceable agreement
among the parties with respect to the matters set forth herein.

        Except as expressly set forth above, the terms and of the Agreement
shall continue in full force and effect from and after the date hereof.

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        Please indicate your acceptance of and agreement with the foregoing by
countersigning a copy of this letter in the space provided below.

                               DIADEXUS LLC

                               By: /s/ PATRICK PLEWMAN
                                  -----------------------------
                               Name: Patrick Plewman
                               Title: President and Chief Operating Officer

Accepted and Agreed to:

INCYTE PHARMACEUTICALS, INC.

By: /s/ ROY A. WHITFIELD
   ------------------------------
Name: Roy A. Whitfield
Title: C.E.O.

SMITHKLINE BEECHAM, PLC

By: /s/ DONALD F. PARMAN
   ------------------------------
Name: Donald F. Parman
Title: Attorney-in-Fact

SMITHKLINE BEECHAM CORPORATION

By: /s/ DONALD F. PARMAN
   ------------------------------
Name: Donald F. Parman
Title: Secretary

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