Third Amendment to Purchase and Sale Contract between Technology Square Finance, LLC and ARE-MA Region No. 31, LLC

EXHIBIT 10.4

THIS THIRD AMENDMENT TO PURCHASE AND SALE CONTRACT ("Amendment") is entered into as of July 26, 2006, by and between TECHNOLOGY SQUARE FINANCE, LLC, a Massachusetts limited liability company ("Seller") and ARE-MA REGION NO. 31, LLC, a Delaware limited liability company ("Buyer").

WHEREAS, Seller and Buyer entered into that certain Purchase and Sale Contract dated as of July 3, 2006, as amended by a First Amendment to Purchase and Sale Contract (the "First Amendment") dated as of July 10, 2006 and a Second Amendment to Purchase and Sale Contract (the "Second Amendment") dated as of July 14, 2006 (as so amended, the "Agreement") with respect to certain real and personal property (the "Property") located at Technology Square, Cambridge, Massachusetts, which Property is more particularly described in the Agreement; and

WHEREAS, Seller and Buyer have agreed to amend the Agreement as more particularly set forth below.

NOW, THEREFORE, for mutual consideration, the receipt and sufficiency of which are hereby acknowledged by the parties, Seller and Buyer hereby amend the Agreement as follows:

1. Capitalized Terms. Capitalized terms not defined herein shall have the meanings ascribed to them in the Agreement.

2. Additional Seller Deliveries at Closing. Seller and Buyer hereby agree that Seller shall deliver the following additional documents at the Closing in accordance with the terms of Section 6.2 of the Agreement:

1. A true, correct and complete list of all Space Leases in effect with respect to the Premises, updated through the date of the Closing, in the form attached to the Agreement as Exhibit T (the "Updated Rent Roll");

3. Additional Seller Representations and Warranties. Section 12.1 of the Agreement is hereby amended by adding the following new representations and warranties of Seller to Buyer under the Agreement as Subsections (l) and (m) after the end of Subsection (k) and before the beginning of Section 12.2 of the Agreement:

4. Revised First Amendment to Development Agreement. Exhibit G to the Second Amendment, the "Form of First Amendment to Development Agreement," is hereby deleted in its entirety and replaced with Exhibit G attached hereto.

5. Extension of Closing Date. The first paragraph of Article 6 of the Agreement is hereby amended by deleting therefrom the date "July 26, 2006" and replacing it with the date "July 27, 2006."

6. Counterparts. This Amendment may be executed in one or more counterpart copies, all of which counterparts shall have the same force and effect as if all parties hereto had executed a single copy of this Amendment.

7. Ratification. Except as amended hereby, the Agreement shall remain in full force and effect.

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IN WITNESS WHEREOF, the parties have executed this Amendment as of the day and year first above written.

SELLER:

BUYER:

Escrow Agent acknowledges the terms of the foregoing Amendment, and agrees to continue to be bound by those terms of the Agreement applicable to the Escrow Agent.

ESCROW AGENT: