Exhibit 10.45

FOURTH AMENDMENT TO SUBLEASE

THIS FOURTH AMENDMENT TO
SUBLEASE (this FourthAmendment), dated October 12, 2007, is entered into by and between
DIADEXUS, INC., a Delaware corporation (Sublandlord), and MONOGRAM BIOSCIENCES,
INC., a Delaware corporation (Subtenant).

RECITALS

A.       Sublandlord and Subtenant entered into that certain Sublease dated June 1, 2002 (the Original Sublease), as amended by that
certain First Amendment to Sublease dated August 21, 2003, that certain Second Amendment to Sublease dated October 1, 2004 and that certain Third Amendment dated August 18, 2006 (together with the Original Sublease, the
Sublease), pursuant to which Sublandlord subleased to Subtenant, and Subtenant subleased from Sublandlord, certain Sublease Premises in a building located at 343 Oyster Point Boulevard, South San Francisco,
California.

B.       Capitalized terms not otherwise defined herein are
used as defined in the Sublease.

C.       Sublandlord and Subtenant
desire to amend the Sublease as set forth herein.

NOW, THEREFORE, in
consideration of the mutual covenants and conditions contained herein, Sublandlord and Subtenant covenant and agree as follows:

AGREEMENT

1.       Term. The sublease for the Section A, Section B Space and expanded premises as defined in the third sublease shall not expire on December 31, 2007 and
shall be extended to continue in full force and effect May 20, 2011, unless sooner terminated pursuant to any provision of the Sublease.

2.       Rent. Base Rent per month effective January 1, 2008 will be as follows:



|                                     |  |   |        |  |  | 
|------------------------------------ |  | - | ------ |  |  | 
|                                     |  |  
|January 1, 2008  December 31, 2008: |  | $ | 77,342 |  |  | 
|                                     |  |  
|January 1, 2009  December 31, 2009: |  | $ | 79,662 |  |  | 
|                                     |  |  
|January 1, 2010  December 31, 2010: |  | $ | 82,052 |  |  | 
|                                     |  |  
|January 1, 2011  May 20, 2011:      |  | $ | 84,514 |  |  | 

3.       Broker. Each party hereto represents
and warrants that it has dealt with no brokers in connection with this Fourth Amendment, and shall indemnify, protect, defend and hold the other harmless from all costs and expenses (including reasonable attorneys fees) arising from a breach
of the foregoing representation and warranty.

4.       Full Force and
Effect. Except as expressly amended hereby, the Sublease remains in full force and effect.



1.



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5.
      Counterparts. This Fourth Amendment may be executed in counterparts, each of which shall be an original, but all of which shall constitute a single agreement.

6.       Effectiveness.This Fourth Amendment shall not be effective until signed by
Master Landlord in the space set forth for that purpose below.

IN WITNESS
WHEREOF, the parties here caused this Fourth Amendment to be duly executed by their respective authorized officers as of the date first written above.



|             |  |                                        |  |                  |  | 
|------------ |  | -------------------------------------- |  | ---------------- |  | 
|SUBLANDLORD: |  | DIADEXUS, INC., a Delaware corporation |  |                 
|             |  |                                        | 
|             |  | By:                                    |  | /s/ David Foster |  | 

| |  |       |  |              |  | 
| |  | ----- |  | ------------ |  | 
| |  | Name: |  | DAVID FOSTER |  | 

|           |  |                                                    |  |           |  | 
|---------- |  | -------------------------------------------------- |  | --------- |  | 
|           |  | Its:                                               |  | EVP & CFO |  | 
|           |  |                                                   
|SUBTENANT: |  | MONOGRAM BIOSCIENCES, INC.,
a Delaware corporation |  |          

| |  |     |  |                     |  | 
| |  | --- |  | ------------------- |  | 
| |  |     | 
| |  | By: |  | /s/ AG Merriweather |  | 

| |  |       |  |                 |  | 
| |  | ----- |  | --------------- |  | 
| |  | Name: |  | AG Merriweather |  | 

| |  |      |  |     |  | 
| |  | ---- |  | --- |  | 
| |  | Its: |  | CFO |  | 

The undersigned, Master Landlord under the Master Lease, hereby consents to the
foregoing Fourth Amendment.

MASTER LANDLORD:



2.