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                                                                   EXHIBIT 10.11

[DIADEXUS LETTERHEAD]

December 20, 1999

Dr. George Poste
6711 E. Camelback, #6
Scottsdale, AZ 85251

       RE: Consultantship Agreement

Dear George:

       diaDexus, a Delaware limited liability company with offices at 3303
Octavius Drive, Santa Clara, California 95054, (hereinafter "diaDexus") is
pleased to note that you (hereinafter "CONSULTANT") may be interested in
providing consulting services to diaDexus as hereinafter defined. Accordingly,
diaDexus proposes the following terms of agreement.

       1. CONSULTANT shall render consulting services to diaDexus as acting
Chief Executive Officer of diaDexus, LLC.

       2. CONSULTANT shall make himself available to diaDexus for the services
provided under this Consultantship Agreement on meeting dates as mutually
agreed.

       3. diaDexus's designated representative shall be Patrick Plewman or such
other representatives which it may subsequently designate in writing.

       4. For consulting services rendered hereunder, diaDexus agrees to pay
CONSULTANT Twenty Thousand US Dollars (U.S. $20,000) on the first of each
calendar quarter (beginning January 1, 2000) until the Agreement is terminated
pursuant to Paragraph 12. diaDexus will also pay CONSULTANT's reasonable
round-trip traveling and living expenses from CONSULTANT's home to the
consulting site. Statements for traveling and living expenses shall be submitted
by CONSULTANT at the end of the trip, and diaDexus will pay such expenses after
receipt and approval thereof. The above-noted payments are full and complete
compensation for all obligations assumed under this Consultantship Agreement and
for all inventions, improvements or patent rights assigned under this
Consultantship Agreement.

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[DIADEXUS LOGO]

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       5. Although CONSULTANT is free to carry out other consultative
arrangements, CONSULTANT shall keep confidential any technical information or
data which are made available to him by diaDexus or its affiliates, or which
result from CONSULTANT's work for diaDexus or its affiliates; and CONSULTANT
agrees that he will not disclose the same to third parties by publication or
otherwise, or use the same for any purpose other than providing consulting
services hereunder without prior approval in writing by diaDexus.

       6. The obligations of confidentiality imposed by this Consultantship
Agreement shall not apply to information which CONSULTANT can show was already
known to CONSULTANT, information which is or becomes part of the public domain
through no fault of CONSULTANT, and information which is given to CONSULTANT by
a third party who has a right to do so.

       7. CONSULTANT shall disclose promptly any inventions or improvements made
or conceived by him, either alone or jointly with others, in the course of or as
a result of the work done hereunder, or as a result of information supplied to
CONSULTANT by diaDexus. CONSULTANT also shall, upon diaDexus's written request,
assign CONSULTANT's entire right, title and interest in and to any and all such
inventions and improvements to diaDexus and to execute such documents as may be
required to file applications and to obtain patents in the name of diaDexus or
its nominees, in any countries, covering such inventions or improvements.

       8. CONSULTANT represents that CONSULTANT is under no obligation which is
inconsistent with this Consultantship Agreement and that CONSULTANT will not
enter into any agreement with a third party, the terms of which may be
inconsistent with this Consultantship Agreement.

       9. Any notices, payments or statements to be made under this
Consultantship Agreement shall be made to CONSULTANT at the address to which
this letter is directed and to any one of diaDexus's designated representatives.

       10. Nothing in this Consultantship Agreement shall in any way be
construed to constitute CONSULTANT as an agent, employee or representative of
diaDexus. CONSULTANT shall perform the services hereunder as an independent
contractor. CONSULTANT acknowledges and agrees that CONSULTANT is obligated to
report as income all compensation received by CONSULTANT pursuant to this
Consultantship Agreement, and CONSULTANT agrees to and acknowledges the
obligation to pay all self-employment and other taxes thereon. CONSULTANT
further agrees to indemnify diaDexus and hold it harmless to the extent of any
obligation imposed on diaDexus (i) to pay in withholding taxes or similar items
or (ii) resulting from CONSULTANT'S being determined not to be an independent
contractor.
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[DIADEXUS LOGO]

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       11. The obligations set forth in paragraphs 4, 5, 7, 8, and 10 hereof
shall survive the expiration or termination of this Consultantship Agreement.

       12. This Consulting Agreement may be terminated by either party at any
time and for any reason effective upon written notice from one party to the
other. In the event this Agreement is terminated, diaDexus shall make a final
payment to CONSULTANT covering consulting services up to and including the
quarter in which the Agreement is terminated.

If the above terms are accepted, please sign and date the duplicate copies of
this letter in the spaces provided below and return one fully executed copy to
diaDexus.

                                Very truly yours,

                                diaDexus, LLC

                                By:  /s/ PATRICK PLEWMAN
                                   ---------------------------------------------
                                Patrick Plewman, Chief Operating Officer


AGREED TO AND ACCEPTED:

By: /s/ GEORGE POSTE
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Title:  Consultant
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Date:  1/3/2000
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