FIFTH AMENDMENT TO OFFICE LEASE

Exhibit 10.6

FIFTH AMENDMENT TO OFFICE LEASE

THIS FIFTH AMENDMENT TO OFFICE LEASE (this “ Amendment ”) is made and effective as of December 1, 2006 (the “ Effective Date ”) by and between MAGUIRE PROPERTIES-SAN DIEGO TECH CENTER, LLC, a Delaware limited liability company (“ Landlord ”), and KINTERA, INC., a Delaware corporation (“ Tenant ”).

RECITALS

A. Landlord is the owner of that certain improved real property located at 9605 Scranton Road Drive, San Diego, California (referred to herein alternatively as “ Building 1 ” or the “ Building ”). Building 1 is a part of that certain project, with all common areas and appurtenant parking facilities, commonly known as the “San Diego Tech Center” (the “ Project ”).

B. San Diego Tech Center, LLC, a Delaware limited liability company (“ SDTC ”), predecessor-in-interest to Calwest (defined below), as landlord, and Tenant, as tenant, entered into that certain Office Building Lease dated as of August 7, 2000 (the “ Original Lease ”), as amended by (i) that certain First Amendment to Lease dated November 1, 2000 (the “ First Amendment ”) by and between Calwest Industrial Properties, LLC (“ Calwest ”), successor-in-interest to SDTC and predecessor-in-interest to Landlord, as landlord, and Tenant, as tenant, (ii) that certain Second Amendment to Lease dated June 24, 2002 (the “ Second Amendment ”) by and between Calwest, as landlord, and Tenant, as tenant, (iii) that certain Third Amendment to Lease dated February 13, 2004 (the “ Third Amendment ”) by and between Calwest, as landlord, and Tenant, as tenant, and (iv) that certain Fourth Amendment to Lease dated April 1, 2005 (the “ Fourth Amendment ”) by and between Calwest, as landlord, and Tenant, as tenant. The Original Lease as amended by the First Amendment, the Second Amendment, the Third Amendment and the Fourth Amendment are collectively referred to herein as the “ Lease ”.

C. Pursuant to the Lease, Tenant has certain rights to use and occupy (i) that certain premises consisting of all of the second (2nd) Floor of the Building consisting of approximately 20,543 rentable square feet (approximately 18,345 usable square feet) (the “ Second Floor Premises ”) as more particularly shown on Exhibit “A-1”, attached hereto, and (ii) that certain premises consisting of a portion of the sixth (6th) Floor of the Building commonly known as Suites 600 and 620 and consisting of approximately 9,769 rentable square feet (approximately 8,822 usable square feet) (the “ Sixth Floor Premises ”) (collectively, the “ Existing Premises ”), all as more particularly described in the Lease.

D. The Lease is scheduled to expire on February 28, 2007 (the “ Scheduled Expiration Date ”).

E. Landlord and Tenant hereby desire by this Amendment to (i) surrender to Landlord the Sixth Floor Premises on or before the Sixth Floor Premises Termination Date (defined in Section 1.1, below) and (ii) add to the Premises that certain space in the Building commonly known as Suite 310 consisting of approximately 7,350 rentable square feet (approximately 6,608 usable square feet) (the “ Suite 310 Premises ”) as more particularly shown on Exhibit “A-2”, attached hereto, (iii) extend the Term of the Lease, and (iv) further amend the Lease upon and subject to each of the terms, conditions, and provisions set forth herein.

F. All capitalized terms used herein without definition are defined as set forth in the Lease.

NOW, THEREFORE, in consideration of the Recitals set forth above, the agreements set forth below and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Landlord and Tenant hereby agree as follows:

1. Amendment .

     1.1 Termination of Tenant’s Lease of the Sixth Floor Premises . Tenant agrees that Tenant shall vacate and surrender the Sixth Floor Premises to Landlord in the condition required by Section 10.2 of the Original Lease on or before the Sixth Floor Premises Termination Date (defined below); provided, however, that notwithstanding the foregoing (and notwithstanding anything to the contrary contained in the Lease), (a) Tenant shall have no obligation to replace any walls that Tenant has previously removed from the Premises with the consent of Landlord and (b) Tenant shall have no obligation under this Section 1.1 (or under Section 10.2 of the Original Lease) to remove from the Sixth Floor Premises any Alterations (other than any Alterations which are of an extraordinary nature (such as fountains, raised computer flooring, fish tanks, etc.) which would likely be unusable by a subsequent office tenant of the Sixth Floor Premises). Notwithstanding anything to the contrary contained herein, in the event that Tenant does not vacate and surrender the Sixth Floor Premises to Landlord on or before the Sixth Floor Premises Termination Date, then such tenancy shall be deemed a “holdover tenancy” subject to the provisions of Section 30.10 of the Original Lease (as amended by Section 1.11 below), including, without limitation, the obligation of Tenant to pay to Landlord “holdover” Rent with respect to the Sixth Floor Premises. Following the Sixth Floor Premises Termination Date, neither Landlord nor Tenant shall have any further rights or obligations under the Lease with respect to the Sixth Floor Premises, other than any rights or obligations applicable to the Sixth Floor Premises which by their terms survive the expiration or earlier termination of the Lease (including, without limitation, Tenant’s obligations under Section 30.10 of the Original Lease and under this Section 1.1), and the Sixth Floor Premises shall be deleted from the “Premises” demised under the Lease. The “ Sixth Floor Premises Termination Date ” means the date that is ten (10) business days following the Substantial Completion Date (defined below).

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1.2 Addition of Suite 310 Premises .

      (a) Commencing on the Suite 310 Premises Commencement Date (as defined below), the Suite 310 Premises shall be added to the Premises, and following the Suite 310 Premises Commencement Date, all references in the Lease to “Premises” shall include the Suite 310 Premises. The “ New Rent Commencement Date ” means the date that is five (5) days (including a weekend) after the earlier to occur of (i) the Substantial Completion Date (defined below) or (ii) the Outside Start Date (defined below). The “ Substantial Completion Date ” means the date on which Substantial Completion of all of the Fifth Amendment Tenant Improvements (as defined in the Work Letter attached hereto as Exhibit “ B ” (the “ Work Letter ”)) occurs; provided, however, that if Landlord is delayed in achieving Substantial Completion of the Fifth Amendment Tenant Improvements by reason of any Tenant Delay (defined in the Work Letter), the Substantial Completion Date shall be deemed to occur on the date that Substantial Completion of the Fifth Amendment Tenant Improvements would have occurred had the Tenant Delay(s) not occurred. The “ Outside Start Date ” means October 1, 2007; provided, however, that the Outside Start Date shall be extended on a day for day basis for each day of Landlord Delay (defined in the Work Letter) that occurs. Any disputes between the parties as to the date upon which the Substantial Completion Date or the Outside Start Date would have occurred had Tenant Delay(s) or Landlord Delay(s), as applicable, not occurred shall be resolved by means of arbitration pursuant to Section 30.18 of the Lease.

      (b) The term of Tenant’s lease of the Suite 310 Premises (the “ Suite 310 Premises Term ”) shall commence on the New Rent Commencement Date and shall expire on the Extended Term Expiration Date

      (c) Following the New Rent Commencement Date, all references in the Lease to the “Premises” shall mean and refer to the Second Floor Premises and the Suite 310 Premises, collectively, and the “Premises” shall consist of a total of approximately 27,893 rentable square feet in the aggregate.

1.3 Extension of Term . Landlord and Tenant hereby agree to extend the Term of the Lease for an additional period (the “ Extended Term ”) commencing on March 1, 2007 (the “ Extended Term Commencement Date ”) and continuing through the last day of the calendar month in which the date that is sixty (60) months after the New Rent Commencement Date occurs (the “ Extended Term Expiration Date ”).

1.4 Rent .

       (a) Prior to Substantial Completion . During the portion of the Term commencing on the date (the “ Execution Date ”) on which Tenant shall deliver a copy of an executed counterpart of this Agreement to Landlord and continuing through and including the New Rent Commencement Date (including any portion of the Extended Term prior to the New Rent Commencement Date), Tenant shall continue to pay to Landlord Rent with respect to the Premises in the amounts required and in the manner required under the Lease (and Rent shall be payable during each month (or partial month) after the Scheduled Expiration date and prior to the New Rent Commencement Date at the same monthly rate that Rent is payable with respect to the month in which the Scheduled Expiration Date occurs (i.e., the Rent for February, 2007, which is set forth in the Lease)).

      (b) Second Floor Premises . Commencing on the New Rent Commencement Date and continuing through the Extended Term, the Rent payable with respect to the Second Floor Premises shall be as follows and shall be payable in accordance with and subject to the procedures set forth in Article 4 of the Original Lease:

* Month 1 commences on the New Rent Commencement Date. In the event that the New Rent Commencement Date shall occur on a day other than the first day of any calendar month, Months 1 – 12 shall include the partial calendar month during which the New Rent Commencement Date occurs together with the following twelve (12) full calendar months (such that, by way of example, if the New Rent Commencement Date were to occur on March 21, 2007, Months 1—12 would begin on March 21, 2007 and end on March 31, 2008, and thirteen (13) payments of Monthly Rent (one of which would be prorated) would be payable with respect to Months 1 – 12).

** Monthly Rents set forth above escalate at an annual rate of 3%. Monthly Rent Rates set forth above also escalate at an annual rate of 3% but have been rounded to the nearest cent.

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      (c) Suite 310 Premises . Commencing on the New Rent Commencement Date and continuing through the Extended Term, the Rent payable with respect to the Suite 310 Premises shall be as follows and shall be payable in accordance with and subject to the procedures set forth in Article 4 of the Original Lease:

* Month 1 commences on the New Rent Commencement Date. In the event that the New Rent Commencement Date shall occur on a day other than the first day of any calendar month, months 1 – 12 shall include the partial calendar month during which the New Rent Commencement Date occurs together with the following twelve (12) full calendar months (such that, by way of example, if the New Rent Commencement Date were to occur on March 21, 2007, Months 1 – 12 would begin on March 21, 2007 and end on March 31, 2008, and thirteen (13) payments of Monthly Rent (one of which would be prorated) would be payable with respect to Months 1 – 12).

** Monthly Rents set forth above escalate at an annual rate of 3%. Monthly Rent Rates set forth above also escalate at an annual rate of 3% but have been rounded to the nearest cent.

1.5 Additional Charges . During the Term (as extended by the Extended Term), Tenant shall continue to pay to Landlord as Additional Charges, Tenant’s Building Share of Excess Building Expenses and Tenant’s Project Share of Excess Project Expenses, all in accordance with the provisions of the Lease, as amended hereby.

      (a) Extended Term Base Year . Effective as of the Extended Term Commencement Date, the Base Year set forth in (i) Item 6(c) of the Basic Lease Terms of Original Lease shall be amended from “2001” to “the calendar year 2007 (ii) Section 5.1(i) of the Original Lease shall be amended from “the period from January 1, 2001 through December 31, 2001” to “the period from January 1, 2007 through December 31, 2007”, and (iii) Section 5.1(j) of the Original Lease shall be amended from “the period from January 1, 2002 through December 31, 2002” to “the period from January 1, 2008 through December 31, 2008”.

       (b) The parties hereto agree that, during the portion of the Term commencing on the Execution Date and continuing through and including the New Rent Commencement Date (including any portion of the Extended Term prior to New Rent Commencement Date), calculation of Tenant’s Building Share of Excess Building Expenses and Tenant’s Project Share of Excess Project Expenses shall be based on the Tenant’s Building Share and Tenant’s Project Share, respectively, as set forth in the Lease (prior to this Amendment), notwithstanding that Tenant may be occupying premises within the Building and Project that does not compute to Tenant’s Building Share or Tenant’s Project Share (as set forth in the Lease, prior to this Amendment)

      (c) The parties hereto acknowledge and agree that, commencing on the New Rent Commencement Date, (i) the Tenant’s Building Share (as set forth in Section 5.1(e) of the Original Lease) shall mean 17.52% (27,893 rsf/159,165 rsf) and (ii) the Tenant’s Project Share (as set forth in Section 5.1(f) of the Original Lease) shall mean 4.31% (27,893 rsf/647,229 rsf).

      (d) Additional Expense Exclusions . In connection with the amendments to the Lease set forth in Section 1.5(e), below, it is hereby agreed that, from and after the Execution Date, for purposes of determining amounts payable by Tenant under Article 5 of the Original Lease (as amended hereby), (i) no portion of the Building Utility Costs (defined below) shall be included in Building Operating Expenses and (ii) no portion of the Project Utility Costs (defined below) be included in Building Expenses.

      (e) Utility Costs . Notwithstanding anything to the contrary in the Lease, commencing on the New Rent Commencement Date, Tenant’s pro rata share of all Utility Costs (defined below) allocable to the Premises shall be billed by Landlord to Tenant as a separate cost item (rather than as part of Building Expenses and Project Expenses). Accordingly, the parties hereto agree that commencing on the New Rent Commencement Date and continuing through the Extended Term, in addition to paying Rent and Tenant’s Building Share and Tenant’s Project Share of Building Expenses and Project Expenses allocable to the Premises, Tenant shall pay to Landlord, as Additional Charges, Tenant’s pro rata share of Utility Costs. Tenant’s pro rata share of Utility Costs shall be payable on a monthly basis, on the first day of each calendar month, in an amount reasonably estimated by Landlord (and as of the date hereof, Landlord’s estimate of amounts payable by Tenant for its pro rata share of Utility Costs is $2.76 per rentable square foot per annum (i.e., approximately $0.23 per rentable square foot per month). Landlord may, from time to time, by written notice to Tenant, revise its estimate for the Tenant’s pro rata share of Utility Costs, and thereafter all subsequent payments by Tenant under this Section 1.5(e) shall be based on such revised estimate. Subject to applicable Laws, all decisions with respect to Utility Services and the costs thereof, including, without limitation, with respect to the method and manner by which all Utility

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