Exhibit 10.6


               ASSUMPTION, CONSENT AND LOAN MODIFICATION AGREEMENT

            THIS ASSUMPTION, CONSENT AND LOAN MODIFICATION AGREEMENT (this
"Agreement") is made and entered into effective as of May 31, 2005, by and among
KS PARCEL D, LLC, a Delaware limited liability company ("Original Borrower"),
THE LYME TIMBER COMPANY, a New Hampshire limited partnership ("Original
Guarantor"), BIOMED REALTY TRUST, INC., a Maryland corporation ("Guarantor"),
BMR - 500 KENDALL STREET LLC, a Delaware limited liability company ("Borrower"),
and THE VARIABLE ANNUITY LIFE INSURANCE COMPANY, a Texas corporation ("Lender").

                                    RECITALS

            A. Original Borrower is the owner of certain real property and
improvements thereon commonly known as 500 Kendall Street, Cambridge,
Massachusetts, as more particularly described on EXHIBIT A attached hereto (the
"Real Property").

            B. On or about November 21, 2003, Lender made a loan to Original
Borrower in the original principal amount of $75,000,000.00 (the "Loan").

            C. The Loan is evidenced by a Promissory Note dated as of November
21, 2003, in the original principal amount of the Loan, executed by Original
Borrower (the "Note").

            D. The Loan is secured in part by a Mortgage, Security Agreement,
Fixture Filing, Financing Statement and Assignment of Leases and Rents (with
Leasehold Addendum) of even date with the Note (the "Mortgage") executed by
Original Borrower, recorded in the Middlesex County (South District) Registry of
Deeds, at Book 41489, Page 077 as Instrument No. 00000754 and encumbering
certain "Property" (as defined in the Mortgage), which Property includes, among
other things, the Real Property.

            E. Repayment of the obligations for which Original Borrower may
incur personal liability under the terms of the Note and Mortgage is guaranteed
by a Guaranty Agreement of even date with the Note (the "Original Guaranty"),
made by Original Guarantor.

            F. In connection with the Loan, Original Borrower and Original
Guarantor have executed an Environmental Indemnity Agreement of even date with
the Note (the "Original Environmental Indemnity").

            G. Original Borrower has agreed to convey the Real Property and the
other Property of Original Borrower to Borrower (the "Transfer"), and Lender has
agreed to consent to the Transfer, provided that (i) Borrower assumes all of the
obligations of Original Borrower under the Loan, subject to the terms and
conditions of this Agreement (the "Assumption"), and (ii) Guarantor executes and
delivers to Lender a Guaranty Agreement concerning the exceptions to
non-recourse provisions set forth in the Note (the "Guaranty"), and an
Environmental Indemnity Agreement relating to the Property ("Environmental
Indemnity"), each of which shall be in form and substance satisfactory to
Lender.



            H. The Note, Mortgage, Original Guaranty, Original Environmental
Indemnity and each other document executed by Original Borrower and/or Original
Guarantor in connection with the Loan are hereinafter collectively referred to
as the "Original Loan Documents." The Original Loan Documents, as modified
hereby, together with this Agreement, the Guaranty, the Environmental Indemnity
and each other document executed by Borrower and/or Guarantor in connection with
the Assumption, are hereinafter referred to as the "Loan Documents."

            I. In connection with the Transfer and the Assumption, Lender has
agreed, subject to the terms and conditions of this Agreement, to release
Original Borrower from its obligations under the Original Loan Documents, and
Original Guarantor from its obligations under the Original Guaranty and Original
Environmental Indemnity, in each case to the extent liability for such
obligations has not heretofore accrued.

                                    AGREEMENT

            NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereby agree as
follows:

            1. Incorporation of Recitals. The Recitals set forth above are
hereby incorporated into and made a part of this Agreement.

            2. Capitalized Terms. All capitalized terms used herein without
definition shall have the meanings given to them in the Mortgage. In the event
of any conflict between definitions set forth herein and the definitions set
forth in any other Loan Document, the definitions set forth herein shall
control.

            3. Representations and Warranties of Original Borrower. Original
Borrower represents and warrants to Lender as follows:

                  (a) None of the Property, Chattels or Intangible Personalty is
      subject to any liens, encumbrances, security interests, or other claims
      whatsoever, except for the lien of the Loan Documents and except insofar
      as such property may be encumbered by the Permitted Exceptions
      (hereinafter defined).

                  (b) Any brokerage commissions due from Original Borrower or
      its affiliates in connection with the Transfer and/or the Assumption have
      been paid in full (or will be paid simultaneously with the Transfer), and
      any such commissions coming due in the future, the non-payment of which
      could result in a lien on, or a claim against, the Property or Lender,
      will be promptly paid by Original Borrower. Original Borrower hereby
      agrees to indemnify, defend and hold harmless Lender from any and all
      liability, claims, demands, actions and causes of action whatsoever
      arising out of or relating to the claim of any person for any brokerage
      commissions, including, without limitation, Lender's attorneys' fees and
      expenses, and costs and expenses incurred by Lender in investigating,
      preparing or defending against any litigation or claim, action, suit,
      proceeding or demand of any kind or character related thereto.

                                        2


            4. Representations, Warranties and Covenants of Borrower. Borrower
hereby re-makes each and every representation and warranty of Original Borrower
to Lender contained in ARTICLE III of the Mortgage (excluding those contained in
SUBSECTIONS 3.3(a) and 3.3(t)), as modified hereby, and Borrower (and Guarantor
with respect to SUBSECTIONS (f) and (g) below) further represents, warrants and
covenants to Lender as follows:

                  (a) Borrower is a limited liability company, duly formed,
      validly existing, and in good standing under the laws of the State of
      Delaware, and has full power and authority to consummate the Transfer and
      the Assumption and to perform its obligations under the Loan Documents.
      Borrower is qualified to transact business in the Commonwealth of
      Massachusetts.

                  (b) The consummation of the Transfer and the Assumption, and
      the execution, delivery, and/or performance by Borrower of this Agreement
      and the other Loan Documents: (i) will not result in any breach of, or
      constitute a default under, any mortgage, agreement, articles of
      organization, operating agreement or other instrument to which Borrower is
      a party or by which Borrower may be bound or affected; (ii) do not
      contravene any applicable law, regulation or order; (iii) require no
      authorization, approval, consent or other action by, and no notice to or
      filing with, any governmental authority or regulatory body; and (iv) are
      within Borrower's powers and have been duly authorized by all necessary
      action.

                  (c) This Agreement and the other Loan Documents to which
      Borrower is a party constitute legal, valid and binding obligations of
      Borrower, enforceable against Borrower in accordance with their terms,
      subject to applicable bankruptcy law and the rights of creditors
      generally.

                  (d) This Agreement and the other Loan Documents collectively
      grant to Lender a valid and enforceable first priority security conveyance
      of and security interest in the Property, subject only to the Permitted
      Exceptions.

                  (e) Borrower has no set-offs, counterclaims, defenses or other
      causes of action against Lender or any of Lender's officers, agents or
      employees arising out of the indebtedness evidenced by the Note, any
      action taken or not taken by Lender or any of Lender's officers, agents or
      employees with respect to the Loan or the Loan Documents, the Transfer,
      the Assumption, or the modification of the Loan Documents, and, to the
      extent any such set-offs, counterclaims, defenses or other causes of
      action may exist, whether known or unknown, such items are waived by
      Borrower. Borrower expressly disclaims any reliance on any oral
      representation made or allegedly made by Lender or any of its officers,
      agents or employees with respect to the Loan, the Loan Documents or this
      Agreement.

                  (f) There are no pending or threatened actions, suits or
      proceedings at law, in equity or before or by any governmental authorities
      that, if determined adversely, could affect Borrower, Guarantor, the
      Property, the validity or enforceability of the Note and Mortgage or the
      priority of the lien thereof. Neither Borrower nor Guarantor is in

                                        3


      default with respect to any order, writ, injunction, decree or demand of
      any court or governmental authorities.

                  (g) Any brokerage commissions due in connection with the
      Transfer and/or the Assumption have been paid in full, and any such
      commissions coming due in the future will be promptly paid or caused to be
      paid by Borrower or Guarantor. Borrower and Guarantor hereby jointly and
      severally agree to indemnify, defend and hold harmless Lender from any and
      all liability, claims, demands, actions and causes of action whatsoever
      arising out of or relating to the claim of any person for any brokerage
      commissions, including, without limitation, Lender's attorneys' fees and
      expenses, and costs and expenses incurred by Lender in investigating,
      preparing or defending against any litigation or claim, action, suit,
      proceeding or demand of any kind or character related thereto.

                  (h) All state or local mortgage taxes, intangible taxes, stamp
      taxes and other fees or taxes (including customary per-page or document
      filing and recording fees imposed by law) required to be paid in the
      Commonwealth of Massachusetts in connection with the Transfer, the
      Assumption, or the execution, delivery, filing, or recording of this
      Agreement or any other Loan Document have been or will be paid upon the
      recording of this Agreement. Borrower and Guarantor hereby jointly and
      severally agree to indemnify, defend and hold harmless Lender from any and
      all liability, claims, demands, actions and causes of action whatsoever
      arising out of or relating to the claim of any person or entity for any
      such tax or fee, including, without limitation, Lender's attorneys' fees
      and expenses, and costs and expenses incurred by Lender in investigating,
      preparing or defending against any litigation or claim, action, suit,
      proceeding or demand of any kind or character related thereto.

            5. Assumption of Liability. Borrower represents, warrants,
covenants, agrees and confirms to Lender that, concurrently herewith, it is
accepting the assignment, conveyance and transfer of the Property, Chattels and
Intangible Personalty, subject to the lien of the Original Loan Documents, and
that from and after the date of this Agreement, Borrower assumes liability for
the indebtedness evidenced by the Note (the outstanding principal balance of
which was $73,189,432.93 as of May 31, 2005) and for each other obligation of
Original Borrower under the Original Loan Documents (referred to herein as the
"Obligations"), and agrees to timely pay or perform such Obligations in
accordance with the terms of the Loan Documents. Accordingly, Borrower
acknowledges that it (a) has previously been supplied with copies of all of the
Original Loan Documents, (b) has had full opportunity to review the terms of the
Original Loan Documents, (c) is entering into this Agreement with the full
realization and understanding that the Property is subject to the liens and
other restrictions and conditions created by and set forth in the Original Loan
Documents, as modified hereby. Lender represents to Borrower that, to the best
of Lender's knowledge, the Original Loan Documents consist of the documents
listed on EXHIBIT B attached hereto and made a part hereof.

            6. Grant of Property; Grant of Security Interest. Borrower hereby
acknowledges and confirms that the Mortgage, as modified hereby, constitutes a
first priority security conveyance of and first lien on the Property, subject
only to the Permitted Exceptions, and secures payment of the Obligations,
including, without limitation, the obligations evidenced

                                       4


by the Note, as modified hereby. Nevertheless, as security for such Obligations,
Borrower hereby (a) grants, bargains, sells, conveys, mortgages and warrants
unto Lender the entire right, title and interest of Borrower in and to the
Property, and (b) grants to Lender a security interest in the Property, Chattels
and Intangible Personalty. In the event of any default under the Loan Documents,
Lender shall have all rights with respect to the Property, Chattels and
Intangible Personalty that are granted by the Loan Documents. Borrower agrees
that it will execute and deliver to Lender such financing statements and other
documents as Lender may deem necessary or advisable in order to perfect or
otherwise protect its security interest in the Property, Chattels and Intangible
Personalty.

            7. Consent of Lender. Lender hereby consents to the Transfer and to
the Assumption. Except as otherwise specifically provided in the Loan Documents,
no further transfer of all or any portion of the Property, Chattels, or
Intangible Personalty shall be permitted without the prior written consent of
Lender.

            8. Modifications. The Original Loan Documents are further modified
as follows:

                  (a) All references to the term "Borrower," "Maker," "Grantor,"
      "Mortgagor" or "Debtor" contained in any Original Loan Document shall be
      deemed to refer to Borrower, and all references to the address of
      "Borrower," "Maker," "Grantor" or "Debtor" in any Original Loan Document
      are hereby replaced with the address of Borrower set forth in SECTION 15
      hereof.

                  (b) All references to any Original Loan Document (e.g., to the
      Note or the Mortgage) in any Original Loan Document shall be deemed to
      refer to such document as modified hereby, and all references to the "Loan
      Documents" shall be deemed to refer to the Loan Documents as defined
      herein.

                  (c) All references to the Guaranty in any Original Loan
      Document shall be deemed to refer to the Guaranty executed by Guarantor.

                  (d) All references to the Environmental Indemnity in any
      Original Loan Document shall be deemed to refer to the Environmental
      Indemnity executed by Borrower and Guarantor.

                  (e) All references to "Permitted Exceptions" contained in any
      Original Loan Document are hereby amended to refer to the Permitted
      Exceptions as defined herein.

                  (f) SECTION 1.17 of the Mortgage is hereby amended to provide
      that the Taxpayer I.D. No. of the "MORTGAGOR" thereunder is 27-0121751 and
      the Organizational Identification No. of the "Mortgagor" is 3958164.

                  (g) SUBSECTION 3.3(a) of the Mortgage is hereby deleted and
      replaced in its entirety by SUBSECTION 4(a) hereof.

                                        5


                  (h) SUBSECTION 3.3(t) of the Mortgage is hereby deleted in its
      entirety and replaced with the following:

                  "(t) there exists no brokerage agreement with respect to the
      sale of any portion of the Property."

                  (i) SUBSECTION 3.3(u)(i) of the Mortgage is hereby deleted in
      its entirety and replaced with the following:

                  "(i) there are no contracts presently affecting the Property
            ("Contracts") having a term in excess of three hundred and
            sixty-five (365) days or not terminable by Mortgagor (without
            penalty) on thirty (30) days' notice;"

                  (j) SUBSECTIONS 4.5(a) and (b) of the Mortgage are hereby
      deleted in their entireties and replaced with the following:

                  "(a) Coverages Required. Mortgagor shall maintain or cause to
            be maintained, with financially sound and reputable insurance
            companies or associations, all insurance required under the terms of
            that certain Agreement Concerning Insurance Requirements concerning
            the Property executed by Mortgagor for the benefit of Mortgagee (the
            "Insurance Agreement"), and shall comply with each and every
            covenant and agreement contained in such Insurance Agreement.

                  (b) Renewal Policies. Not less than thirty (30) days prior to
            the expiration date of each insurance policy required pursuant to
            the Insurance Agreement, Mortgagor will deliver to Mortgagee an
            appropriate renewal policy (or a certified copy thereof), together
            with evidence satisfactory to Mortgagee that the applicable premium
            has been prepaid."

                  (k) The reference to ninety (90) days in SUBSECTION 4.12(c) of
      the Mortgage is hereby replaced with one hundred twenty (120) days.

                  (l) SUBSECTION 4.23 of the Mortgage is hereby modified to
      provide that the "Property Manager" thereunder shall be either Meredith &
      Grew, Incorporated or Borrower.

                  (m) SUBSECTIONS 5.4(b) and 5.4(d) of the Mortgage are hereby
      deleted in their entireties.

            9. Conditions Precedent. Lender's consent hereunder is subject to
Lender having received each of the following, in form and substance satisfactory
to Lender and its counsel:

                                        6


                  (a) A fee payable to Lender in the amount of $731,894.33 (1%
      of outstanding principal balance of Loan).

                  (b) Financing statements and/or such other documents as Lender
      may require in order to create, perfect against Borrower and otherwise
      protect its security interests and liens on the Property, Chattels and
      Intangible Personalty.

                  (c) Such searches of the public records as Lender may deem
      necessary or advisable.

                  (d) Copies of all agreements among Borrower, Original Borrower
      and other parties involved in the Transfer relating in any way to the
      Transfer, including, without limitation, all deeds and bills of sale
      transferring the Property, Chattels and/or Intangible Personalty from
      Original Borrower to Borrower, all of which documentation must be
      satisfactory to Lender in its sole discretion.

                  (e) Certified copies of Borrower's organizational documents,
      together with all amendments thereto, and evidence satisfactory to Lender
      that (i) Borrower is a limited liability company, duly organized, validly
      existing and in good standing under the laws of the State of Delaware, and
      is qualified to transact business in the Commonwealth of Massachusetts,
      and (ii) Borrower has the power and authority to enter into the Transfer
      and the Assumption and to perform its obligations under the Loan
      Documents.

                  (f) Endorsements to the ALTA-form title insurance policy in
      force currently in the amount of the Loan (or a new policy, if reasonably
      required by Lender) naming Lender as insured mortgagee, issued by a title
      insurance company acceptable to Lender, insuring that the Mortgage, as
      modified and assumed by Borrower hereby, constitutes a first priority lien
      on the Property, with such additional endorsements as may be required by
      Lender, and with no exceptions or exclusions other than the following (the
      "Permitted Exceptions"): (i) the "Permitted Exceptions" as defined in the
      Mortgage (excluding real property taxes for 2004 and subsequent years not
      yet due and payable), (ii) real property taxes for the year 2005 and
      subsequent years not yet due and payable, and (iii) such other exceptions
      as may be acceptable to Lender in its sole discretion. Lender reserves the
      right to require a current "as-built" survey of the Property if required
      by the title insurance company in order to issue endorsements (or a new
      policy) in compliance with the requirements of this Subsection.

                  (g) A legal opinion of Borrower's counsel, addressed to Lender
      and dated as of the date hereof, in form and substance satisfactory to
      Lender, opining that (i) the Assumption and the execution, delivery and/or
      assumption of the Loan Documents have been duly authorized by all
      necessary parties (other than Lender), (ii) the Loan Documents are binding
      and enforceable against Borrower in accordance with their terms, and (iii)
      the Environmental Indemnity and Guaranty are binding and enforceable
      against Guarantor in accordance with their terms, and addressing such
      other matters (including the good standing, authority and due execution
      and delivery by Borrower and Guarantor) as Lender may reasonably require.

                                        7


                  (h) Such financial and other information regarding Borrower
      and Guarantor as Lender may reasonably require.

                  (i) A certificate of insurance acceptable to Lender evidencing
      compliance with the insurance coverage requirements set forth in SECTION
      4.5 of the Mortgage (or an endorsement to the existing policy indicating
      the new owner of the Property).

                  (j) The execution by Guarantor of the Guaranty and
      Environmental Indemnity.

            10. No Other Modifications. Except as expressly modified hereby, the
Original Loan Documents remain in full force and effect in accordance with their
terms. In the event of any inconsistency between this Agreement and any Original
Loan Document, this Agreement shall control. Lender shall have no obligation to
make any further modifications to any of the Original Loan Documents.

            11. Costs and Expenses. Original Borrower shall pay on demand all
reasonable costs and expenses incurred by Lender in connection with the
Assumption and the Transfer and each other transaction contemplated hereby,
including, without limitation: costs actually accrued or paid by Lender in
connection with the negotiation, preparation, execution or recording of this
Agreement or any other documents prepared in connection with the transactions
contemplated herein or associated herewith; attorneys' fees and the fees of any
other person or entity engaged by Lender in connection herewith; appraisal,
title insurance and recording costs, fees and expenses; and any tax, assessment
or similar charge due in connection with the Assumption or the execution,
recordation and/or amendment of the Loan Documents. Borrower shall pay on demand
all reasonable costs and premiums incurred by Lender in connection with the
title insurance required hereunder.

            12. Further Assurances. The parties hereby agree to execute any and
all additional documents that may reasonably be required in order to evidence,
secure or carry out the agreements and undertakings set forth in this Agreement.

            13. Release.

                  (a) Lender hereby releases and forever discharges Original
      Borrower and Original Guarantor from any and all causes of action, suits,
      liabilities, debts, damages, controversies, agreements, trespasses,
      judgments, executions, demands and claims of any nature whatsoever,
      whether in law or equity, whether known or unknown, whether primary or
      secondary, and any and all rights, duties, liabilities and obligations,
      whether presently enforceable or enforceable in the future, by reason of
      any matter or cause which directly or indirectly is based on or related
      to, arises out of, or is in any way connected with the Loan, the Original
      Loan Documents or Original Borrower's or Original Guarantor's performance
      under the Original Loan Documents; provided, however, that neither
      Original Borrower nor Original Guarantor shall be released from any
      recourse liability under SECTION 18 of the Note (and original Grantor's
      corresponding obligations under the Original Guaranty), or any liability
      arising under the Original

                                        8


      Environmental Indemnity that has heretofore accrued or could be based on
      any event which has occurred or any state of affairs that existed prior to
      or as of the date hereof, including, without limitation, any liability
      relating to the potential claim by Verizon regarding contamination of
      surface water or groundwater in the immediate vicinity of the Property.

                  (b) Original Borrower and Original Guarantor hereby release
      and forever discharge Lender and all of Lender's successors and assigns,
      agents, attorneys and employees from any and all causes of action, suits,
      liabilities, debts, damages, controversies, agreements, trespasses,
      judgments, executions, demands and claims of any nature whatsoever,
      whether in law or equity, whether known or unknown, whether primary or
      secondary, and any and all rights, duties, liabilities and obligations,
      whether presently enforceable or enforceable in the future, by reason of
      any matter or cause which directly or indirectly is based on or related
      to, arises out of, or is in any way connected with the Transfer, the
      Assumption, the Loan, the Loan Documents, Lender's administration of the
      Loan, or Lender's performance under the Loan Documents; provided, however,
      that the foregoing release shall not preclude Original Borrower or
      Original Grantor from asserting good faith defenses that otherwise would
      have been available to them in any actions brought by Lender to enforce
      any recourse liability not released by Lender pursuant to SECTION 13(a)
      above.

            14. Escrowed Funds. Each of the parties hereto agrees that any funds
currently held in escrow by Lender's "Servicer" for the payment of real property
taxes and/or insurance, pursuant to SUBSECTIONS 4.4(b) and 4.5(c) of the
Mortgage, shall continue to be held by such Servicer for the benefit of the
Property, and Lender and Borrower hereby authorize Servicer to apply such funds
toward payment of taxes and/or insurance for the Property in accordance with the
terms of the Mortgage, as modified hereby. Original Borrower hereby assigns to
Borrower all of Original Borrower's right, title and interest to such funds.

            15. Notices. Any notice required or permitted to be given hereunder
shall be in writing and will be deemed given (a) upon personal delivery, (b) on
the first business day after receipted delivery to a courier service which
guarantees next-business-day delivery, or (c) on the third business day after
mailing, by registered or certified United States mail, postage prepaid, in any
case to the appropriate party at its address set forth below:

            If to Borrower:

                  BMR - 500 Kendall Street LLC
                  17140 Bernardo Center Drive, Suite 222
                  San Diego, California 92128
                  Attention: General Counsel

                                        9


            If to Lender:

                  The Variable Annuity Life Insurance Company
                  c/o AIG Global Investment Corp.
                  1 SunAmerica Center, 38th Floor
                  Century City
                  Los Angeles, California 90067-6022
                  Attention: Director, Mortgage Lending and Real Estate

Any party may change its address for notices or copies of notices by giving
notice to the other parties in accordance with this Section.

            16. Governing Law. This Agreement shall be subject to, governed by
and construed and enforced in accordance with the laws of the Commonwealth of
Massachusetts.

            17. Successors and Assigns. This Agreement shall be binding upon and
inure to the benefit of the parties hereto and their permitted successors and
assigns.

            18. WAIVER OF RIGHT TO JURY TRIAL. EACH PARTY TO THIS AGREEMENT
KNOWINGLY, IRREVOCABLY, VOLUNTARILY AND INTENTIONALLY WAIVES ANY RIGHT IT MAY
HAVE TO A TRIAL BY JURY IN RESPECT OF ANY ACTION, PROCEEDING OR COUNTERCLAIM
BASED ON THIS AGREEMENT, OR ARISING OUT OF, UNDER OR IN CONNECTION WITH THE
NOTE, THE MORTGAGE OR ANY OTHER LOAN DOCUMENT, ANY ORIGINAL LOAN DOCUMENT, OR
ANY COURSE OF CONDUCT, COURSE OF DEALING, STATEMENT (WHETHER VERBAL OR WRITTEN)
OR ACTIONS OF ANY PARTY HERETO OR TO ANY LOAN DOCUMENT OR ORIGINAL LOAN
DOCUMENT. THIS PROVISION IS A MATERIAL INDUCEMENT FOR THE PARTIES TO ENTER INTO
THE TRANSACTIONS EVIDENCED BY THIS AGREEMENT.

            19. Counterparts. This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

            20. No Release of Liens. This Agreement in no way acts as a release
or relinquishment of those liens, security interests, security conveyances,
encumbrances, and rights securing payment of the Loan, including without
limitation the liens, security conveyances, and security interests created by
the Mortgage and the other Loan Documents. Such liens, security interests,
encumbrances and rights are hereby ratified, confirmed, renewed and extended by
Borrower and the Original Borrower in all respects.

                   [BALANCE OF PAGE INTENTIONALLY LEFT BLANK]

                                       10


            IN WITNESS WHEREOF, the parties hereto have executed and delivered
this Agreement as of the date first above written.

                                  ORIGINAL BORROWER:

                                  KS PARCEL D, LLC, a Delaware limited
                                  liability company

                                  By: Kendall Square, LLC, a Delaware limited
                                      liability company, its manager

                                      By: Lyme Properties LLC, a New Hampshire
                                          limited liability company, its manager

                                          By: /s/ David E. Clem
                                              ----------------------------------
                                          Name: David E. Clem
                                          Title: Manager

                                  ORIGINAL GUARANTOR:

                                  THE LYME TIMBER COMPANY, a New
                                  Hampshire limited partnership

                                  By: Woodland Management Associates, LLC, a
                                      New Hampshire limited liability company,
                                      its General Partner

                                      By: /s/ David M. Roby
                                          -----------------------------------
                                          David M. Roby, Manager



                                  BORROWER:

                                  BMR - 500 KENDALL STREET LLC, a Delaware
                                  limited liability company

                                  By: BioMed Realty, L.P., a Maryland limited
                                      partnership, its Member

                                      By: BioMed Realty Trust, Inc., a Maryland
                                          corporation, its General Partner

                                          By: /S/ GARY A. KREITZER
                                             ______________________________
                                          Name: Gary A. Kreitzer
                                          Title: Executive Vice President

                                  GUARANTOR:

                                  BIOMED REALTY TRUST, INC., a Maryland
                                  corporation

                                    By:   /S/ GARY A. KREITZER
                                        ________________________________________

                                  Name:  Gary A. Kreitzer
                                        ______________________________________

                                 Title:  Executive Vice President
                                        _____________________________________

                                  LENDER:

                                  THE VARIABLE ANNUITY LIFE INSURANCE COMPANY,
                                  a Texas corporation

                                  By: AIG Global Investment Corp., a New Jersey
                                      corporation, its investment advisor

                                      By:  /S/ ALAN J. NUSSENBLATT
                                          ____________________________________

                                    Name:  Alan J. Nussenblatt
                                          __________________________________

                                   Title:  Managing Director
                                          _________________________________



ORIGINAL BORROWER:

STATE OF __________________________)
                                   ) ss.
COUNTY OF _________________________)                         _____________, 2005

            Then personally appeared the above-named David E. Clem, Manager of
Lyme Properties LLC, a New Hampshire limited liability company, Manager of
Kendall Square, LLC, a Delaware limited liability company, Manager of KS Parcel
D, LLC, a Delaware limited liability company, and acknowledged the foregoing
instrument to be the free act and deed of David E. Clem and such limited
liability companies before me.

                                  _________________________________________
                                  Notary Public

                                  My commission expires: __________________

ORIGINAL GUARANTOR:

STATE OF __________________________)
                                   ) ss.
COUNTY OF _________________________)                         _____________, 2005

            Then personally appeared the above-named David M. Roby, as Manager
of Woodland Management Associates, LLC, a New Hampshire limited liability
company, as General Partner of THE LYME TIMBER COMPANY, a New Hampshire limited
partnership, and acknowledged the foregoing instrument to be the free act and
deed of David M. Roby and such limited liability company and limited partnership
before me.

                                  _________________________________________
                                  Notary Public

                                  My commission expires: __________________



GUARANTOR:

STATE OF __________________________)
                                   ) ss.
COUNTY OF _________________________)                         _____________, 2005

            Then personally appeared the above-named Gary A. Kreitzer, as
Executive Vice President of BIOMED REALTY TRUST, INC., a Maryland corporation,
and acknowledged the foregoing instrument to be the free act and deed of Gary A.
Kreitzer and such corporation before me.

                                  _________________________________________
                                  Notary Public

                                  My commission expires: __________________

BORROWER:

STATE OF __________________________)
                                   ) ss.
COUNTY OF _________________________)                         _____________, 2005

            Then personally appeared the above-named Gary A. Kreitzer, Executive
Vice President of BioMed Realty Trust, Inc., a Maryland corporation, as General
Partner of BioMed Realty, L.P., a Maryland limited partnership, as Member of BMR
- - 500 KENDALL STREET LLC, a Delaware limited liability company, and acknowledged
the foregoing instrument to be the free act and deed of Gary A. Kreitzer and
such corporation, limited partnership and limited liability company before me.

                                  _________________________________________
                                  Notary Public

                                  My commission expires: __________________



LENDER:

State of California                )
                                   ) ss
County of _________________________)

            On _______________________, 20__, before me,
________________________, personally appeared ________________________,
personally known to me, or proved to me on the basis of satisfactory evidence to
be the person(s) whose name(s) is/are subscribed to the within instrument and
acknowledged to me that he/she/they executed the same in his/her/their
authorized capacity(ies), and that by his/her/their signature(s) on the
instrument the person(s), or the entity upon behalf of which the person(s)
acted, executed the instrument.

            WITNESS my hand and official seal.

                                  __________________________________
                                  Signature of Notary



                                    EXHIBIT A

                                 (Real Property)

                                    Exhibit A

                                     Page 1



                                    EXHIBIT B

                        (LIST OF ORIGINAL LOAN DOCUMENTS)

1.    Promissory Note dated as of November 21, 2003 in the amount of
      $75,000,000.00;

2.    Mortgage, Security Agreement, Fixture Filing, Financing Statement and
      Assignment of Leases and Rents (With Leasehold Addendum) dated as of
      November 21, 2003 and recorded in Book 41489, Page 077 with the Registry
      of Deeds of Middlesex County, Massachusetts;

3.    Guaranty Agreement dated as of November 21, 2003 (not being assumed by
      Borrower);

4.    Environmental Indemnity Agreement dated as of November 21, 2003 (not being
      assumed by Borrower);

5.    UCC-1 Financing Statements:

      (a)   Delaware Secretary of State - Document No. 33119453, recorded
            November 26, 2003;

      (b)   Middlesex County - Book 41489, Page 128, recorded November 24, 2003;

6.    Certificate Concerning Leases and Financial Condition dated as of November
      21, 2003;

7.    Certificate Concerning Governing Documents dated as of November 21, 2003
      (not being assumed by Borrower);

8.    Agreement Concerning Insurance Requirements dated as of November 21, 2003
      (not being assumed by Borrower);

9.    Receipt and Agreement dated as of November 21, 2003 (not being assumed by
      Borrower);

10.   Parking Lease dated as of July 17, 2002;

11.   First Amendment to Parking Lease dated as of August 1, 2003;

12.   Second Amended and Restated Notice of Lease (Parcel D Parking Lease) dated
      as of August 1, 2003 and recorded November 24, 2003 in Book 35927, Page
      340 with the Middlesex County Registry of Deeds Southern District;

13.   Quit Claim Deed (Parcel D) to KS Parcel A/D, LLC and Quit Claim Deed
      (Parcel D) to Borrower (Establishing Parking Easement) dated July 17,
      2002;

                                    Exhibit B

                                     Page 1



14.   Estoppel Certificate and Agreement with Respect to Parking Rights dated as
      of November 21, 2003;

15.   Subordination and Recognition Agreement (Garage Loan Subordination) dated
      as of November 21, 2003 and recorded November 24, 2003 in Book 41380, Page
      521 with the Middlesex County Registry of Deeds Southern District;

16.   Subordination and Recognition Agreement (Condo Subordination) dated as of
      November 21, 2003; and recorded November 24, 2003 in Book 41489, Page 149
      with the Middlesex County Registry of Deeds Southern District;

17.   Side Letter Concerning Certificate of Occupancy dated as of October 31,
      2003; and

18.   Subordination, Non - Disturbance and Attornment Agreement - Genzyme
      Corporation dated as of November 21, 2003

                                    Exhibit B

                                     Page 2