AMENDMENT NO. 4 TO MARINA VILLAGE NET OFFICETECH LEASE

Exhibit 10.12

AMENDMENT NO. 4

TO

MARINA VILLAGE NET OFFICE–TECH LEASE

THIS AMENDMENT NO. 4 (“Amendment No. 4”) is made and entered into as of March 1, 2005 (the “Effective Date”), by and between ALAMEDA REAL ESTATE INVESTMENTS, a California limited partnership (“Landlord”), and XENOGEN CORPORATION, a Delaware corporation (“Tenant”).

RECITALS

NOW, THEREFORE, in consideration of the mutual agreements herein contained, Landlord and Tenant hereby agree as follows:

“Tenant’s failure to pay any rent or other sum payable hereunder when due in accordance with the provisions of this Lease where such failure is the first (1^st) or second (2^nd) failure to timely pay in any calendar year during the term of the Lease and such failure is not cured within five (5) days after delivery of notice to Tenant from Landlord specifying such failure to pay, and thereafter, Tenant’s failure to pay rent or any other sum payable hereunder when due; provided, however, that any notice provided by Landlord hereunder shall be in lieu, of and not in addition to, any notice required under Section 1161 et seq. of the California Code of Civil Procedure;”

“5. the default by Tenant beyond applicable notice and cure periods in the performance of any of the terms, covenants, agreements, or conditions

contained in (A) that certain Marina Village Net Office-Tech Lease dated June 6, 2000, as amended, by and between Landlord and Tenant for premises located at 2061 Challenger Drive, Suites 100, 101, 102 and 103, Alameda, California (the ‘Challenger Lease’); and (B) that certain Marina Village Net Office-Tech Lease dated as of March 1, 2005 by and between Landlord and Tenant for premises located at 850 Marina Village Parkway, Alameda, California (the ‘850 Lease’).”

“6. Landlord shall also have the remedy described in California Civil Code Section 1951.4 (lessor may continue the lease in effect after lessee’s breach and abandonment and recover rent as it becomes due, if lessee has the right to sublet or assign, subject only to reasonable limitations).

7. Landlord’s acceptance of payment from Tenant of less than the amount of rent then due shall not constitute a waiver of any rights of Landlord or Tenant including, without limitation, any right of Landlord to recover possession of the Premises.”

“d. Tenant hereby waives all rights under California Code of Civil Procedure Section 1179 and California Civil Code Section 3275 providing for relief from forfeiture, and any other right now or hereafter existing to redeem the Premises or reinstate this Lease after termination pursuant to this Paragraph 13 or by order or judgment of any court or by and legal process; provided, however, that such waiver shall only apply in the case of monetary defaults and/or material nonmonetary defaults by Tenant under this Lease.

e. Landlord and Tenant hereby waive trial by jury in any action, proceeding or counterclaim brought by either of the parties hereby against the other on any matters not relating to personal injury or property damage but otherwise arising out of or in any way connected with this Lease, the relationship of Landlord and Tenant under this Lease, Tenant’s use or occupancy of the Premises and any statutory remedy.

f. The remedies provided for in this Lease are in addition to any other remedies available to Landlord at law or in equity, by statute or otherwise.”

“Tenant waives the provisions of California Civil Code Section 1950.7, and all other present or future laws that restrict the amount or types of claims that a

landlord may make upon a security deposit or imposes upon a landlord or a successor any obligation with respect to the handling or return of security deposits. Notwithstanding anything to the contrary herein, Tenant acknowledges and agrees that the amount of the security deposit under the Lease, that would otherwise be returned to Tenant hereunder, if any, shall not be returned to Tenant but, rather, shall be applied by Landlord as the deposit under the 850 Lease.”

“In addition, such communications shall be deemed given when transmitted to a party by electronic facsimile, with confirmation of receipt, to the telephone number specified in the Basic Lease Information, as it may be changed by notice.”

Return Date. During the period following the Premises Return Date and ending on the final Early Termination Date (as defined below), Tenant shall continue to pay rent and perform its other obligations under the Lease with respect to all or any portion of the Premises as to which an Early Termination (as defined below) has not occurred, except as otherwise provided herein. If Landlord is successful, having used commercially reasonable efforts, in reletting all or any portion of the Premises following the Premises Return Date, Landlord shall notify Tenant of such fact, and Landlord’s notice(s) shall specify which portion of the Premises is affected and a date for early termination of this Lease (each, an “Early Termination”) with respect to such portion of the Premises (each, an “Early Termination Date”) in which event the Lease shall terminate on the following terms:

for such Lease term extension as soon as the Commencement Date of the 850 Lease is determined. If Tenant fails to make such election by delivering its notice to Landlord within such five (5) business day period, the Lease shall terminate on the date of Term Expiration set forth in the Lease.

IN WITNESS WHEREOF, Landlord and Tenant have entered into this Amendment No. 4 as of the Effective Date.

EXHIBIT A

List of Specialized Improvements

860 Atlantic Avenue, Alameda

Large Equipment List to be retained by Xenogen Corporation