Document:

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                                                                   EXHIBIT 10.16

                                 Amendment No. 1
                                     to the
                     Master Strategic Relationship Agreement
                                between and among
           SmithKline Beecham Corporation, Incyte Pharmaceuticals, Inc
                                       and
                                  diaDexus, LLC

        This Amendment, made as of the 15th day of January 1998, by and among
SmithKline Beecham Corporation, a Pennsylvania corporation with offices at One
Franklin Plaza, Philadelphia, Pennsylvania 19101, U.S.A; Incyte Pharmaceuticals,
Inc., a Delaware corporation with offices at 3174 Porter Drive, Palo Alto,
California 94304; and diaDexus, a Delaware limited liability company with
offices at 3303 Octavius Drive, Santa Clara, California 95054;

                                  WITNESSETH:

               WHEREAS, Incyte, SB, and diaDexus entered into the Master
Strategic Relationship Agreement dated 2 September 1997; and

               WHEREAS, Incyte, SB, and diaDexus desire to amend such Master
Strategic Relationship Agreement;

               NOW, THEREFORE, in consideration of the premises and the mutual
covenants herein contained, the parties hereto agree as follows:

                                1.0 DEFINITIONS

1.1     All initially capitalized words and phrases shall have the same meaning
        as in the Master Strategic Relationship Agreement.

                                 2.0 AMENDMENT

2.1     Section 6.1(a)(i) of the Agreement shall be amended to read in its
        entirety as follows:

        Subject to Section 6.1(c), on April 15, 1998, SB shall make a second
        contribution to the LLC of cash in an aggregate amount equal to $7
        million.

2.2     Section 6.1(b)(i) of the Agreement shall be amended to read in its
        entirety as follows:

        Subject to Section 6.1(c), on April 15, 1998, Incyte shall make a second
        contribution to the LLC of cash in an aggregate amount equal to $2
        million.

2.3     Paragraph 10.7(a)(i), two occurrences of "ML" are replaced with "SB".

2.4     Paragraph 10.15 is amended to add the following:

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If to LLC, addressed to:
     diaDexus, LLC
     3303 Octavius Drive
     Santa Clara, CA 95054
     Attention: Patrick Plewman
     Vice President, Corporate Development and Assistant Secretary
     Tel: (408)-330-5004
     Fax: (408)-496-5777

Copy to:       Patricia Schreck, Vice President, General Counsel & Secretary
               diaDexus, LLC
               209 Pembroke Ave.
               Wayne, PA 19087
               Tel: (610)-964-7629
               Fax: (610)-341-1307

                                   3.0 EFFECT

3.1     The Master Strategic Relationship Agreement is amended as of January 15,
        1998 as provided herein in accordance with Paragraph 10.10 thereof.

3.2     All other terms and provisions of the Master Strategic Relationship
        Agreement shall be unaffected by this Amendment.

3.3     This Amendment may be executed in one or more counterparts, each of
        which shall be an original and all of which shall constitute together
        the same document.

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

SmithKline Beecham Corporation

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

Incyte Pharmaceuticals Inc.

By: /s/ RANDAL SCOTT
   -------------------------------

diaDexus, LLC

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

                                       2<PAGE>   1
                                                                   EXHIBIT 10.18

                                 Amendment No. 1
                                     to the
                       Collaboration and License Agreement
                                between and among
            SmithKline Beecham, PLC, SmithKline Beecham Corporation,
                          Incyte Pharmaceuticals, Inc.
                                       and
                                  diaDexus, LLC

        This Amendment, made as of the _ day of February 1998, by and among
SmithKline Beecham Corporation, a Pennsylvania corporation with offices at One
Franklin Plaza, Philadelphia, Pennsylvania 19101, U.S.A; SmithKline Beecham plc,
an English corporation with its principal offices at New Horizons Court,
Brentford, Middlesex, TW8 9EP, England; Incyte Pharmaceuticals, Inc., a Delaware
corporation with offices at 3174 Porter Drive, Palo Alto, California 94304; and
diaDexus, a Delaware limited liability company with offices at 3303 Octavius
Drive, Santa Clara, California 95054;

                                  WITNESSETH:

               WHEREAS, Incyte, SB, and diaDexus, LLC entered into the
Collaboration and License Agreement dated 2 September 1997; and

               WHEREAS, Incyte, SB, and diaDexus, LLC desire to amend such
Collaboration and License Agreement;

               NOW, THEREFORE, in consideration of the premises and the mutual
covenants herein contained, the parties hereto agree as follows:

                                1.0 DEFINITIONS

1.1     All initially capitalized words and phrases shall have the same meaning
        as in the Collaboration and License Agreement.

                                 2.0 AMENDMENT

2.1     The definition of "DiaDexus Affiliate" is deleted and substituted with
        the following definition:

        "diaDexus Affiliate": shall mean any corporation, firm, partnership, or
        other legal entity, which is directly or indirectly owned by diaDexus to
        the extent of which the common stock or other equity ownership thereof
        is one hundred percent (100%) owned by diaDexus; provided however, that
        where local laws require a minimum percentage of local ownership, the
        status of

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        diaDexus Affiliate will be established if diaDexus directly or
        indirectly owns or controls one hundred percent (100%) of the maximum
        ownership percentage that may, under such local laws, be owned or
        controlled by foreign interests.

2.2     All occurrences of the word "DiaDexus" are replaced with word
        "diaDexus".

2.3     The definition of "DiaDexus" is deleted and substituted with the
        following definition:

        "diaDexus": shall mean diaDexus, a Delaware limited liability company
        with offices at 3303 Octavius Drive, Santa Clara CA; and any diaDexus
        Affiliate(s) thereof to which any rights and/or obligations shall be
        assigned and/or delegated pursuant to this Agreement.

2.4     The definition of "Incyte Affiliate" is deleted and substituted with
        the following definition:

        "Incyte Affiliate": shall mean any corporation, firm, partnership, or
        other legal entity, which is directly or indirectly owned by Incyte to
        the extent of which the common stock or other equity ownership thereof
        is one hundred percent (100%) owned by Incyte; provided however, that
        where local laws require a minimum percentage of local ownership, the
        status of Incyte Affiliate will be established if Incyte directly or
        indirectly owns or controls one hundred percent (100%) of the maximum
        ownership percentage that may, under such local laws, be owned or
        controlled by foreign interests.

2.5     Notices and deliveries to diaDexus pursuant to Paragraph 19.10 is
        deleted and replaced with the following:

If to diaDexus, addressed to:
        diaDexus, LLC
        3303 Octavius Drive
        Santa Clara, CA 95054
        Attention: Patrick Plewman
        Vice President, Corporate Development and Assistant Secretary
        Tel: (408)-330-5004
        Fax: (408)-496-5777

Copy to:      Patricia Schreck, Vice President, General Counsel & Secretary
              diaDexus, LLC
              209 Pembroke Ave.
              Wayne, PA 19087
              Tel: (610)-964-7629
              Fax: (610)-341-1307

                                       2

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                                   3.0 EFFECT

3.1     The Collaboration and License Agreement is amended as provided herein as
        of the date first written above in accordance with Paragraph 19.6
        thereof.

3.2     All other terms and provisions of the Collaboration and License
        Agreement shall be unaffected by this Amendment.

3.3     This Amendment may be executed in one or more counterparts, each of
        which shall be an original and all of which shall constitute together
        the same document.

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

SmithKline Beecham Corporation

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

SmithKline Beecham, plc

By: /s/ DONALD Y. PARMAN
   -------------------------------
         attorney-in-fact

Incyte Pharmaceuticals Inc.

By: /s/ RANDAL SCOTT
   -------------------------------

diaDexus, LLC

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

                                       3<PAGE>   1
                                                                   EXHIBIT 10.20

                              [INCYTE LETTERHEAD]

BY FACSIMILE

May 4, 1999

Joseph L. Harris
Senior Vice President and Director
Corporate Strategy and Business Development
SmithKline Beecham
One Franklin Plaza
Philadelphia, PA 19101

Patrick Plewman
Chief Operating Officer
diaDexus, LLC
3303 Octavius Drive
Santa Clara, CA 95054

Dear Joe and Bill:

        This letter follows up on our recent conversations regarding the
Collaboration and License Agreement, dated September 2, 1997, (the
"Collaboration and License Agreement"), among diaDexus, LLC ("diaDexus"), Incyte
Pharmaceuticals, Inc. ("Incyte"), SmithKline Beecham plc and SmithKline Beecham
Corporation (collectively, "SB"). When signed by diaDexus, Incyte and SB, this
letter will be an amendment to the Collaboration and License Agreement.

        1. Subject to the terms of this amendment, diaDexus, Incyte and SB agree
that intellectual property that is either (a) owned by SB Biologicals SA ("SB
Biologicals") or with respect to which SB Biologicals has the right to grant a
license or (b) owned by SB or with respect to which SB has the right to grant a
license to the extent the intellectual property described in this subsection (b)
is specific to a therapeutic vaccine product or prophylactic vaccine product
that is being developed, promoted or marketed by SB Biologicals (collectively
referred to as "SB Biological IP"), is not and will not be included within the
definitions of "SB Diagnostic IP" or "SB Technology IP" pursuant to the
Collaboration and License Agreement.

        2. SB Biologicals will remain subject to all of the provisions of the
Collaboration and License Agreement applicable to SB Affiliates, including
without limitation those in Section 7.1. In this regard the parties agree that,
during the Initial License Period (as defined in the Collaboration and License
Agreement), SB Biologicals will not itself engage in the business of making,
having made or selling cDx Kit(s), except in connection with the development,
marketing, co-marketing, distribution or sale of a specific therapeutic vaccine
product or prophylactic vaccine product.

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        3. For the avoidance of doubt, diaDexus, Incyte and SB acknowledge that
intellectual property pertaining to single nucleotide polmorphisms ("SNPs")
and/or genotyping that is owned by Incyte or with respect to which Incyte has
the right to grant a license is not and will not be included within the
definitions of "Incyte Diagnostic IP" or "Incyte Technology IP" pursuant to the
Collaboration and License Agreement.

        4. Nothing in this amendment shall constitute a waiver by any party of
any other right under the Collaboration and License Agreement, except as
explicitly set forth in this amendment.

        5. This amendment shall become effective upon execution of this
amendment, and shall be applied retroactively to the Effective Date of the
Collaboration and License Agreement.

        I believe that this is responsive to SB's request and ask that the
parties execute this amendment where indicated below. We are looking forward to
concluding the diaDexus financing.

                                   Sincerely,

                                   /s/ MARIAN N. MARRA
                                   -------------------
                                   Marian N. Marra
                                   Senior Vice President,
                                   Corporate Development

cc: Roy Whitfield
    Randy Scott

AGREED AND ACCEPTED:

SmithKline Beecham Corporation            SmithKline Beecham plc

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

Title: Secretary                          Title: Director
      ----------------------------              ----------------------------

Date: May 4, 1999                         Date: May 4, 1999
     -----------------------------             -----------------------------
diaDexus

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

Title: COO
      ----------------------------

Date: 8/10/99
     -----------------------------

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