**Exhibit10.1**

 

**LEASEAGREEMENT**

THIS LEASE AGREEMENT is made as of this 22nd day ofJune, 2007, between **ARE-TECH SQUARE, LLC,**a Delaware limited liability company (“Landlord”), and **SIRTRIS PHARMACEUTICALS, INC.**, a Delawarecorporation (“Tenant”).

**BASIC LEASE PROVISIONS**
| **Address:**                                     |   | 200 Technology Square, Cambridge, Massachusetts                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Premises:**                                    |   | That portion of the Project, containing a total of  approximately 44,084 rentable square feet, as determined by Landlord,  consisting of approximately (i) 17,357 rentable square feet on the second (2nd) floor of the Building (“**Second Floor Space**”), (ii) 17,357  rentable square feet on the third (3rd)  floor of the Building (“**Third Floor Space**”),  (iii) 8,679 rentable square feet on the fourth (4th) floor of the Building (“**Fourth Floor Space**”); (iv) 471  rentable square feet on the first (1st)  floor of the Building (“**First Floor Space**”)  and (v) 220 rentable square feet of space, in the basement of the  Building (the “**Basement Space**”),  as shown on **Exhibit A.** |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Building:**                                    |   | The specific building in which the Premises are  located, which building is within the Project and located at 200 Technology  Square, also known as Unit 200 of the Condominium described in **Exhibit B**.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Project:**                                     |   | The real property on which the Building is located,  also known as Technology Square Condominium (the “**Condominium**”), together with all improvements thereon and  appurtenances thereto from time to time located thereon in the City of  Cambridge, Middlesex County, Commonwealth of Massachusetts, as described on **Exhibit B**. The Landlord reserves the right to modify the  Condominium at any time and from time to time, but the parties acknowledge  the Condominium presently consists of Units 100, 200, 300, 400, 500, 600 and  700 (also known as Buildings 100, 200, 300, 400, 500, 600 and 700), as well  as specified common areas on the Condominium (including the Technology Square  Garage).                                                     |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Base Rent:**                                   |   | $58.50 per rentable square foot per year, subject to  annual increase on the Adjustment Date as set forth herein                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Rentable Area  of Premises:**                  |   | 44,084 sq. ft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Rentable Area  of Building:**                  |   | 177,101 sq. ft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Tenant’s Share  of Operating  Expenses:** |   | 24.89%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Rentable Area  of Project:**                   |   | 1,164,288 sq. ft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| ** **                                       |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| **Building’s  Share of Project:**           |   | 15.21%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

 

 

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| **Security Deposit:**            |   | $1,925,805.38 (subject to proportionate increase in  the event Tenant exercises its Expansion Right pursuant to Section 39  hereof, and subject to potential reduction in accordance with Section 6  hereof).                                                                                                                                                                           |
|----------------------------------|--------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ** **                       |   |                                                                                                                                                                                                                                                                                                                                                                                    |
| **Target  Commencement  Date:**  |   | December 1, 2007                                                                                                                                                                                                                                                                                                                                                                        |
| ** **                       |   |                                                                                                                                                                                                                                                                                                                                                                                    |
| **Rent  Commencement  Date:**    |   | (1) With respect to the Basement Space, First Floor  Space, Second Floor Space, and Third Floor Space, the Rent Commencement Date  shall be the Commencement Date, and (2) with respect to the Fourth Floor  Space, the Rent Commencement Date shall be the earlier of (a) one year after  the Commencement Date or (b) the date of Tenant’s occupancy of the Fourth  Floor Space. |
| ** **                       |   |                                                                                                                                                                                                                                                                                                                                                                                    |
| **Rent Adjustment  Percentage:** |   | Greater of (a) 3.5% or (b) the CPI Adjustment  Percentage                                                                                                                                                                                                                                                                                                                               |
| ** **                       |   |                                                                                                                                                                                                                                                                                                                                                                                    |
| **Base Term:**                   |   | Beginning on the Commencement Date and ending ten  (10) years from the first day of the first full month of the Term (as defined  in Section 2) hereof.                                                                                                                                                                                                                                 |
| ** **                       |   |                                                                                                                                                                                                                                                                                                                                                                                    |
| **Permitted Use:**               |   | Research and development laboratory, related office  and other related uses consistent with the character of the Project and  otherwise in compliance with the provisions of Section 7 hereof.                                                                                                                                                                                          |

 
| **Address for Rent Payment:**                                                                                             | ** ** | **Landlord’s Notice Address:**                                                        |
|---------------------------------------------------------------------------------------------------------------------------|------------|--------------------------------------------------------------------------------------------|
| 385 East Colorado Boulevard, Suite 299  Pasadena, CA 91101  Attention: Accounts Receivable                                |       | 385 East Colorado Boulevard, Suite 299  Pasadena, CA 91101  Attention: Corporate Secretary |
|                                                                                                                      |       |                                                                                       |
| **Tenant’s Notice Address:**                                                                                         | ** ** | ** **                                                                                 |
| ** **                                                                                                                | ** ** | ** **                                                                                 |
| From and after the Commencement Date, the  Premises, Attention: Chief Executive Officer; prior  to the Commencement Date: |       |                                                                                       |
|                                                                                                                      |       |                                                                                       |
| 790 Memorial Drive  Cambridge, MA 02139  Attention: Chief Executive Officer                                               |       |                                                                                       |

 

The following Exhibits and Addenda are attached heretoand incorporated herein by this reference:
| x**EXHIBIT A** - PREMISES DESCRIPTION                                                                                                  |   | x**EXHIBIT B** - DESCRIPTION OF PROJECT           |
|----------------------------------------------------------------------------------------------------------------------------------------|--------|---------------------------------------------------|
| x**EXHIBIT C** – WORK LETTER                                                                                                      |   | x**EXHIBIT D** - COMMENCEMENT DATE                |
| x**EXHIBIT E** – RULES AND REGULATIONS                                                                                            |   | x**EXHIBIT F** - TENANT’S PERSONAL  PROPERTY |
| x**EXHIBIT G** – REPLACEMENT SECTIONS  2(A), 2(B), 2(C) AND 3(A) OF WORK LETTER FOR AVAILABLE SPACE (PER SECTION  39(B) OF LEASE) |   | x**EXHIBIT H** – ROOFTOP EQUIPMENT  LOCATION |

 

1.             **Lease of Premises.**  Upon and subject to all of the terms andconditions hereof,  Landlord herebyleases the Premises to Tenant and Tenant hereby leases the Premises fromLandlord.  Subject to the terms of thisLease, Landlord shall use reasonable efforts to provide to Tenant reasonableaccess to the Premises 24 hours per day, 7 days per week.  The portions of the Project which are for the

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non-exclusive use of tenants of the Project arecollectively referred to herein as the “**Common Areas.**”  Landlord reserves the right to modify CommonAreas, provided that such modifications do not materially adversely affectTenant’s access to or use of the Premises for the Permitted Use.  Tenant shall also have the non-exclusiveright, in common with others entitled thereto (i) to use the atrium locatedbetween the Building and Building 100 (the “**Atrium**”),and (ii) subject to the conditions set forth herein, to install communicationsequipment within its proportionate share of available space on the roof of theBuilding in the location specified on the roof plan attached hereto as **Exhibit H**. Any such rooftop equipment shall (a) be installed, if at all, in a goodand workmanlike manner by Tenant at Tenant’s sole cost and expense, (b) besubject to the requirements of all applicable laws and regulations andotherwise subject to the terms and conditions of this Lease, (c) not interferein any way with base building systems or equipment, adversely affect thestructural integrity of the Building or adversely impact the roof, roofmembrane or any roof warranty in any manner and (d) not interfere with therights of any other tenants of the Building.

2.             **Delivery; Acceptance ofPremises; Commencement Date**. Landlord shall use reasonable efforts to deliver the Premises to Tenanton or before the Target Commencement Date, with Landlord’s Work, if any,Substantially Completed (“**Delivery**” or “**Deliver**”).  IfLandlord fails to timely Deliver the Premises, Landlord shall not be liable toTenant for any loss or damage resulting therefrom, and this Lease shall not bevoid or voidable except as provided herein. If Landlord does not Deliver the Premises within 60 days of the TargetCommencement Date (as such date may be extended due to Force Majeure (asdefined in Section 34) delays and Tenant Delays), this Lease may beterminated by Tenant by written notice to Landlord, and if so terminated:  (a) the Security Deposit, or any balancethereof (i.e., after deducting therefrom all amounts to which Landlord isentitled under the provisions of this Lease), shall be returned to Tenant, and(b) neither Landlord nor Tenant shall have any further rights, duties or obligationsunder this Lease, except with respect to provisions which expressly survivetermination of this Lease.** **As used herein, the terms “**Landlord’s Work**,” “**Tenants’ Work**,”“**Tenant Delays**” and “**Substantially Completed**”****shall have themeanings set forth for suchterms in the Work Letter.  If Tenant doesnot elect to void this Lease within ten (10) business days of the lapse of such60 day period, such right to void this Lease shall be waived and this Leaseshall remain in full force and effect.

The “**Commencement Date**”shall be the earliest of: (i) the later of (a) December 1, 2007, (b) the dateLandlord Delivers the Premises to Tenant or (c) the date Landlord could haveDelivered the Premises but for Tenant Delays; and (ii) the date Tenantconducts any business in the Premises or any part thereof.  The “**Rent****Commencement Date**” shall be (a) the Commencement Date, withrespect to the First Floor Space, Second Floor Space, and Third Floor Space,and (b) with respect to the Fourth Floor Space only, the earlier of (X) oneyear after the Commencement Date or (Y) the date Tenant conducts any businessin the Fourth Floor Space or any part thereof.**** **Uponrequest of Landlord, Tenant shall execute and deliver a written acknowledgmentof the Commencement Date, the RentCommencement Date(s) and the expiration date of the Term when such areestablished in the form of the “Acknowledgement of Commencement Date” attachedto this Lease as **Exhibit D**; provided, however,Tenant’s failure to execute and deliver such acknowledgment shall not affectLandlord’s rights hereunder.  The “**Term**” of this Lease shall be the Base Term, as defined abovein the Basic Lease Provisions and anyExtension Terms which Tenant may elect pursuant to Section 41 hereof.

Except as set forth in the Work Letter, ifapplicable:  (i) Tenant shall accept thePremises in their condition as of the Commencement Date, subject to allapplicable Legal Requirements (as defined in Section 7 hereof); (ii)Landlord shall have no obligation for any defects in the Premises; and (iii)Tenant’s taking possession of the Premises shall be conclusive evidence thatTenant accepts the Premises and that the Premises were in good condition at thetime possession was taken.  Any occupancyof the Premises by Tenant before the Commencement Date shall be subject to allof the terms and conditions of this Lease, except that, if such occupancy doesnot include any operation of Tenant’s business, then Tenant shall not berequired to pay Base Rent or Tenant’s Share of Operating Expenses prior to theCommencement Date.

Tenant agrees and acknowledges that neither Landlordnor any agent of Landlord has made any representation or warranty with respectto the condition of all or any portion of the Premises or the

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Project, and/or thesuitability of the Premises or the Project for the conduct of Tenant’sbusiness, and Tenant waives any implied warranty that the Premises or theProject are suitable for the Permitted Use. This Lease constitutes the complete agreement of Landlord and Tenantwith respect to the subject matter hereof and supersedes any and all priorrepresentations, inducements, promises, agreements, understandings andnegotiations which are not contained herein. Landlord in executing this Lease does so in reliance upon Tenant’srepresentations, warranties, acknowledgments and agreements contained herein.

3.             **Rent**.

(a)           **Base Rent**.  The first month’s Base Rent and the SecurityDeposit shall be due and payable on delivery of an executed copy of this Leaseto Landlord.  Tenant shall pay to Landlordin advance, without demand, abatement, deduction or set-off, monthlyinstallments of Base Rent on or before the first day of each calendar monthduring the Term hereof beginning after the Rent Commencement Date, in lawfulmoney of the United States of America, at the office of Landlord for payment ofRent set forth above, or to such other person or at such other place asLandlord may from time to time designate in writing.  Payments of Base Rent for any fractional calendarmonth shall be prorated.  The obligationof Tenant to pay Base Rent and other sums to Landlord and the obligations ofLandlord under this Lease are independent obligations.  Tenant shall have no right at any time toabate, reduce, or set-off any Rent (as defined in Section 5) due hereunderexcept for any abatement as may be expressly provided in this Lease.

(b)           **Additional Rent. **In addition to Base Rent, Tenantagrees to pay to Landlord as additional rent (“**AdditionalRent**”):  (i) Tenant’s Share of“Operating Expenses” (as defined in Section 5), and (ii) any and allother amounts Tenant assumes or agrees to pay under the provisions of thisLease, including, without limitation, any and all other sums that may becomedue by reason of any default of Tenant or failure to comply with the agreements,terms, covenants and conditions of this Lease to be performed by Tenant, afterany applicable notice and cure period.

4.             **Base Rent Adjustments**.  Base Rent shall be increased on each annualanniversary of the first day of the first full month during the Term of thisLease (each an “**Adjustment Date**”) by multiplyingthe Base Rent payable immediately before such Adjustment Date by the RentAdjustment Percentage and adding the resulting amount to the Base Rent payableimmediately before such Adjustment Date. Base Rent, as so adjusted, shall thereafter be due as providedherein.  Base Rent adjustments for anyfractional calendar month shall be prorated. **“CPI Adjustment Percentage”** means (i) afraction, stated as a percentage, the numerator of which shall be the Index forthe calendar month 3 months before the month in which the Adjustment Dateoccurs, and the denominator of which shall be the Index for the calendar month3 months before the last Adjustment Date or, if no prior Base Rent adjustmenthas been made, 3 months before the first day of the first full month during theTerm of this Lease, less (ii) 1.00.  “**Index**” means the “Consumer Price Index-All UrbanConsumers-Northeast Region, All Items” compiled by the U.S. Department ofLabor, Bureau of Labor Statistics, (1982-84 = 100).  If a substantial change is made in the Index,the revised Index shall be used, subject to such adjustments as Landlord mayreasonably deem appropriate in order to make the revised Index comparable tothe prior Index.  If the Bureau of LaborStatistics ceases to publish the Index, then the successor or most nearlycomparable index, as reasonably determined by Landlord, shall be used, subjectto such adjustments as Landlord may reasonably deem appropriate in order tomake the new index comparable to the Index. Landlord shall give Tenant written notice indicating the Base Rent, asadjusted pursuant to this Section, and the method of computation and Tenantshall pay to Landlord an amount equal to any underpayment of Base Rent by Tenantwithin 15 days of Landlord’s notice to Tenant. Failure to deliver such noticeshall not reduce, abate, waive or diminish Tenant’s obligation to pay theadjusted Base Rent.

5.             **Operating Expense Payments**.  Landlord shall deliver to Tenant a writtenestimate of Operating Expenses for each calendar year during the Term (the “**Annual Estimate**”), which may be revised by Landlord fromtime to time during such calendar year. During each month of the Term, on the same date that Base Rent is due,Tenant shall pay Landlord an amount equal to 1/12th ofTenant’s Share of the Annual Estimate. Payments for any fractional calendar month shall be prorated.

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The term “**Operating Expenses**”means all costs and expenses of any kind or description whatsoever incurred oraccrued each calendar year by Landlord with respect to the Building (including the Landlord’sreasonable determination of the Building’s proportionate share of all expensesattributable to the Atrium (which the parties acknowledge shall be greater thanthe Building’s Share of Project), as well as the Building’s Share of Project ofall other costs and expenses of any kind or description incurred or accrued byLandlord with respect to the Project and the Condominium (including withoutlimitation all costs of compliance with the PTDM, as hereinafter defined) whichare not specific to the Building or any other building located in the Project)****(including, without duplication, Taxes (as defined in Section9), reasonable reserves consistent with good business practice for futurerepairs and replacements, capital repairs and improvements amortized (except asexcluded from Operating Expenses as set forth in clause (b), below) over theuseful life of such capital items determined in accordance with GAAP (asdefined in Section 22(a)), or as reasonably determined by Landlord tothe extent such items constitute repairs, replacements or improvements to theheating, ventilation and air conditioning system or other building equipment,and the costs of Landlord’s third party property manager or, if there is nothird party property manager or if the third party property manager does notprovide all management services, administration rent in the amount of 3.0% ofBase Rent, less any management fees paid to any third party manager), excludingonly:

(a)           the original construction costs ofthe Project and renovation prior to the date of the Lease and costs ofcorrecting defects in such original construction or renovation;

(b)           capital expenditures for expansion ofthe Project or for curing a noncompliance of the Building with applicable LegalRequirement (as defined Section 27) where such noncompliance constituteda non-compliance as of the date hereof;

(c)           interest, principal payments ofMortgage (as defined in Section 27) debts of Landlord, financing costsand amortization of funds borrowed by Landlord, whether secured or unsecuredand all payments of base rent (but not taxes or operating expenses) under anyground lease or other underlying lease of all or any portion of the Project;

(d)           depreciation of the Project (exceptfor capital improvements, the cost of which are includable in Operating Expenses);

(e)           advertising, legal and space planningexpenses and leasing commissions and other costs and expenses incurred inprocuring and leasing space to tenants for the Project, including any leasingoffice maintained in the Project, free rent and construction allowances fortenants;

(f)            legal and other expenses incurred inthe negotiation or enforcement of leases;

(g)           completing, fixturing, improving,renovating, painting, redecorating or other work, which Landlord pays for orperforms for other tenants within their premises, and costs of correctingdefects in such work;

(h)           costs of utilities outside normalbusiness hours sold to tenants of the Project;

(i)            costs to be reimbursed by othertenants of the Project or Taxes to be paid directly by Tenant or other tenantsof the Project, whether or not actually paid;

(j)            costs incurred by Landlord fortesting, cleanup and remediation of Hazardous Materials to the extent, and onlyto the extent, that Landlord has actually received reimbursement for such costsfrom a third party, it being acknowledged and agreed that Landlord shall haveno obligation to endeavor to obtain any such reimbursement;

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(k)           salaries, wages, benefits and othercompensation paid to officers and employees of Landlord who are not assigned inwhole or in part to the operation, management, maintenance or repair of theProject;

(l)            general organizational,administrative and overhead costs relating to maintaining Landlord’s existence,either as a corporation, partnership, or other entity, including generalcorporate, legal and accounting expenses;

(m)          costs (including attorneys’ fees andcosts of settlement, judgments and payments in lieu thereof) incurred inconnection with disputes with tenants, other occupants, or prospective tenants,and costs and expenses, including legal fees, incurred in connection withnegotiations or disputes with employees, consultants, management agents, leasingagents, purchasers or mortgagees of the Building;

(n)           costs incurred by Landlord due to theviolation by Landlord, its employees, agents or contractors or any tenant ofthe terms and conditions of any lease of space in the Project or any LegalRequirement (as defined in Section 7);

(o)           penalties, fines or interest incurredas a result of Landlord’s inability or failure to make payment of Taxes and/or to file any tax or informational returnswhen due, or from Landlord«‘s failure to make any payment of Taxes required tobe made by Landlord hereunder before delinquency;

(p)           overhead and profit increment paid toLandlord or to subsidiaries or affiliates of Landlord for goods and/or servicesin or to the Project to the extent the same exceeds the costs of such goodsand/or services rendered by unaffiliated third parties on a competitive basis;

(q)           costs of Landlord’s charitable orpolitical contributions, or of fine art maintained at the Project;

(r)            costs in connection with services(including electricity), items or other benefits of a type which are notstandard for the Project and which are not available to Tenant without specificcharges therefor, but which are provided to another tenant or occupant of theProject, whether or not such other tenant or occupant is specifically chargedtherefor by Landlord;

(s)           costs incurred in the sale orrefinancing of the Project;

(t)            net income taxes of Landlord or theowner of any interest in the Project, franchise, capital stock, gift, estate orinheritance taxes or any federal, state or local documentary taxes imposedagainst the Project or any portion thereof or interest therein; and

(u)           any expenses otherwise includablewithin Operating Expenses to the extent actually reimbursed by persons otherthan tenants of the Project under leases for space in the Project.

Within 90 days after the end of each calendar year (orsuch longer period as may be reasonably required), Landlord shall furnish toTenant a statement (an “**Annual Statement**”)showing in reasonable detail:  (a) the totaland Tenant’s Share of actual Operating Expenses for the previous calendar year,and (b) the total of Tenant’s payments in respect of Operating Expenses forsuch year.  If Tenant’s Share of actualOperating Expenses for such year exceeds Tenant’s payments of OperatingExpenses for such year, the excess shall be due and payable by Tenant as Rentwithin 30 days after delivery of such Annual Statement to Tenant.  If Tenant’s payments of Operating Expensesfor such year exceed Tenant’s Share of actual Operating Expenses for such yearLandlord shall pay the excess to Tenant within 30 days after delivery of suchAnnual Statement, except that after the expiration, or earlier termination ofthe Term or if Tenant is delinquent in its obligation to pay Rent, Landlordshall pay the excess to Tenant after deducting all other amounts due Landlord.

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The Annual Statement shall be final and binding uponTenant unless Tenant, within 90 days after Tenant’s receipt thereof, shallcontest any item therein by giving written notice to Landlord, specifying eachitem contested and the reason therefor.* *If, during such 90 day period,Tenant reasonably and in good faith questions or contests the accuracy ofLandlord’s statement of Tenant’s Share of Operating Expenses, Landlord willprovide Tenant with access to Landlord’s books and records relating to theoperation of the Project and such information as Landlord reasonably determinesto be responsive to Tenant’s questions (the “**ExpenseInformation**”).  If afterTenant’s review of such Expense Information, Landlord and Tenant cannot agreeupon the amount of Tenant’s Share of Operating Expenses, then Tenant shall havethe right to have an independent public accounting firm selected by Tenanteither (x) from among the 5 largest in the United States or (y) otherwiseapproved by Landlord (which approval shall not be unreasonably withheld ordelayed), in either case, working pursuant to a fee arrangement other than acontingent fee (at Tenant’s sole cost and expense), audit and/or review theExpense Information for the year in question (the “**IndependentReview**”).  The results of anysuch Independent Review shall be binding on Landlord and Tenant.  If the Independent Review shows that thepayments actually made by Tenant with respect to Operating Expenses for thecalendar year in question exceeded Tenant’s Share of Operating Expenses forsuch calendar year, Landlord shall at Landlord’s option either (i) credit theexcess amount to the next succeeding installments of estimated OperatingExpenses or (ii) pay the excess to Tenant within 30 days after delivery of suchstatement, except that after the expiration or earlier termination of thisLease or if Tenant is delinquent in its obligation to pay Rent, Landlord shallpay the excess to Tenant after deducting all other amounts due Landlord.  If the Independent Review shows that Tenant’spayments with respect to Operating Expenses for such calendar year were lessthan Tenant’s Share of Operating Expenses for the calendar year, Tenant shallpay the deficiency to Landlord within 30 days after delivery of suchstatement.  If the Independent Reviewshows that Tenant has overpaid with respect to Operating Expenses by more than5% then Landlord shall reimburse Tenant for all costs incurred by Tenant forthe Independent Review.  OperatingExpenses for the calendar years in which Tenant’s obligation to share thereinbegins and ends shall be prorated. Notwithstanding anything set forth herein to the contrary, if theBuilding is not at least 95% occupied on average during any year of the Term,Tenant’s Share of Operating Expenses for such year shall be computed as thoughthe Building had been 95% occupied on average during such year.

“**Tenant’s Share**”shall be the percentage set forth in the Basic Lease Provisions as Tenant’sShare, as reasonably adjusted by Landlord following a measurement of therentable square footage of the Building and the Premises to be done by Landlordduring the first year of the Base Term, or as soon as is reasonably practicablethereafter, and shall be subject to further adjustment for changes in thephysical size of the Premises, Building or Project occurring thereafter.  Any such measurement or remeasurement shallbe performed in accordance with Landlord’s standard method of measuring spacein the Project, consistently applied. Landlord shall have the right to equitably adjust the Rentable Area ofPremises, Rentable Area of Building, Rentable Area of Project and Building’sShare of Project following any such measurement or remeasurement of thePremises, Building or Project.  Landlordmay equitably increase Tenant’s Share for any item of expense or costreimbursable by Tenant that relates to a repair, replacement, or service thatbenefits only the Premises or only a portion of the Project that includes thePremises or that varies with occupancy or use. Base Rent, Tenant’s Share of Operating Expenses and all other amountspayable by Tenant to Landlord hereunder are collectively referred to herein as “**Rent**.”

6.             **Security Deposit**.  Tenant shall deposit with Landlord, upondelivery of an executed copy of this Lease to Landlord, a security deposit (the“**Security Deposit**”) for the performanceof all of Tenant’s obligations hereunder in the amount set forth in the BasicLease Provisions, which Security Deposit shall be in the form of anunconditional and irrevocable letter of credit (the “**Letter ofCredit**”):  (i) in form andsubstance satisfactory to Landlord, (ii) naming Landlord as beneficiary, (iii)expressly allowing Landlord to draw upon it at any time from time to time bydelivering to the issuer notice that Landlord is entitled to draw thereunder,(iv) issued by an FDIC-insured financial institution satisfactory to Landlord,and (v) redeemable by presentation of a sight draft in the state of Landlord’schoice.  If Tenant does not provideLandlord with a substitute Letter of Credit complying with all of therequirements hereof at least 10 days before the stated expiration date of anythen current Letter of Credit, Landlord shall have the right to draw the fullamount of the current Letter of Credit and hold the funds drawn in cash withoutobligation for interest thereon as the Security Deposit.  In the event Tenant exercises its ExpansionRight (as

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defined in Section 39 below), the Security Depositshall be increased proportionately to reflect any resulting increase in BaseRent payable under the Lease, as set forth in Section 39.  The Security Deposit shall be held byLandlord as security for the performance of Tenant’s obligations under this Lease.  The Security Deposit is not an advance rentaldeposit or a measure of Landlord’s damages in case of Tenant’s default.  Upon each occurrence of a Default (as definedin Section 20), Landlord may use all or any part of the Security Depositto pay delinquent payments due under this Lease, and the cost of any damage,injury, expense or liability caused by such Default, without prejudice to anyother remedy provided herein or provided by law.  Upon any such use of all or any portion ofthe Security Deposit, Tenant shall pay Landlord on demand the amount that willrestore the Security Deposit to the amount set forth in the Basic LeaseProvisions.  Tenant hereby waives theprovisions of any law, now or hereafter in force, which provide that Landlordmay claim from a security deposit only those sums reasonably necessary toremedy defaults in the payment of Rent, to repair damage caused by Tenant or toclean the Premises, it being agreed that Landlord may, in addition, claim thosesums reasonably necessary to compensate Landlord for any other loss or damage,foreseeable or unforeseeable, caused by the act or omission of Tenant or anyofficer, employee, agent or invitee of Tenant. Upon bankruptcy or other debtor-creditor proceedings against Tenant, theSecurity Deposit shall be deemed to be applied first to the payment of Rent andother charges due Landlord for periods prior to the filing of suchproceedings.  Upon any such use of all orany portion of the Security Deposit, Tenant shall, within 5 business days afterdemand from Landlord, restore the Security Deposit to its original amount.  If Tenant shall fully perform every provisionof this Lease to be performed by Tenant, the Security Deposit, or any balancethereof (i.e., after deducting therefrom all amounts to which Landlord isentitled under the provisions of this Lease), shall be returned to Tenant (or,at Landlord’s option, to the last assignee of Tenant’s interest hereunder)within 90 days after the expiration or earlier termination of this Lease.

If Landlord transfers its interest in the Project orthis Lease, Landlord shall either (a) transfer any Security Deposit then heldby Landlord to a person or entity assuming Landlord’s obligations under this Section6, or (b) return to Tenant any Security Deposit then held by Landlord andremaining after the deductions permitted herein.  Upon such transfer to such transferee or thereturn of the Security Deposit to Tenant, Landlord shall have no furtherobligation with respect to the Security Deposit, and Tenant’s right to thereturn of the Security Deposit shall apply solely against Landlord’stransferee.  The Security Deposit is notan advance rental deposit or a measure of Landlord’s damages in case of Tenant’sdefault.  Landlord’s obligationrespecting the Security Deposit is that of a debtor, not a trustee, and nointerest shall accrue thereon.

On the second anniversary of the Commencement Date,and every second year thereafter on the anniversary of such date until the endof the Base Term (each such date being a “**ReductionDate**”), provided Tenant is not then in default under any of itsobligations under the Lease and provided further that Tenant has not previouslybeen in default under any of its obligations under the Lease beyond applicablenotice and cure periods, then Tenant shall have the right, upon at least 10days’ prior written notice to Landlord, to reduce the Security Depositeffective as of such Reduction Date by the amount of $213,978.38 (provided thatsuch reduction amount shall be subject to proportionate increase in the eventthe Security Deposit has previously been increased as a result of Tenant’sexercise of its Expansion Right).  If theamount of the Security Deposit is reduced in accordance with this Section, thenfrom and after the date of each such reduction, the “**SecurityDeposit**” shall be deemed to be the reduced amount of the SecurityDeposit for all purposes of this Lease. By way of example only and in no way intending to limit the foregoing,if on the second anniversary of the Commencement Date (i.e., at the beginningof year 3 of the Base Term), Tenant is not in default under any of itsobligations under the Lease and has not previously been in default under anysuch obligations beyond applicable notice and cure periods, then Tenant shallhave the right, effective as of such second anniversary and upon the giving ofnotice as aforesaid, to reduce the Security Deposit by the amount of$213,978.38.  Likewise, at the beginningof each of years 5, 7 and 9 of the Base Term, provided no then-current defaultexists by Tenant and there has been no prior default by Tenant beyondapplicable notice and cure periods, Tenant shall again have the right to reducethe Security Deposit by the amount of $213,978.38 on each such Reduction Date.  There shall be no reduction of the SecurityDeposit following the expiration of the Base Term.  If at any time during the Term of this LeaseTenant defaults under any of its obligations beyond applicable notice and cureperiods, there shall be no further reduction of the Security Deposit.

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7.             **Use**.  The Premisesshall be used solely for the Permitted Use set forth in the Basic LeaseProvisions, and in compliance with all laws, orders, judgments, ordinances,regulations, codes, directives, permits, licenses, covenants and restrictionsnow or hereafter applicable to the Premises, and to the use and occupancythereof, including, without limitation, the Americans With Disabilities Act, 42U.S.C. § 12101, et seq. (together with the regulations promulgated pursuantthereto, “**ADA**”) (collectively, “**Legal Requirements**” and each, a “**Legal Requirement**”). Tenant shall, upon 5 days’ written notice from Landlord, discontinue anyuse of the Premises which is declared by any Governmental Authority (as definedin Section 9) having jurisdiction to be a violation of a LegalRequirement.  Subject to Landlord’sconsent, not to be unreasonably withheld, conditioned or delayed, Tenant mayappeal or contest such a declaration by any Governmental Authority as to aviolation of a Legal Requirement by Tenant, provided that Tenant shall providesuch reasonable security as may be requested by Landlord for the payment of anyfines or penalties as may be charged by such Governmental Authority, anyinterest thereon and the cost of the contest on the declaration of theproceedings or suit in which such contest may be had.  Such security may be provided by Tenant’sdelivering or causing to be delivered to Landlord cash or other securitysatisfactory to Landlord, or a bond of indemnity of a good and solvent suretycompany in form and amount satisfactory to Landlord.  In any event, Tenant agrees to indemnify andsave Landlord harmless from all cost and expenses incurred on account of Tenant’sparticipation in such appeal or contest. In no event shall Landlord be deemed to be unreasonable in disapprovingany such appeal or contest in the event that Landlord determines in its solediscretion (a) there is a possibility of criminal liability in connectiontherewith, (b) that the appeal or contest could be detrimental to thereputation of the Building and/or the Project, (c) that such appeal or contestcould adversely impact Landlord’s ability to lease other space in the Project,(d) that such appeal or contest could have an adverse impact on other occupantsof the Project, (e) that such appeal or contest would or could hurt its abilityto finance and/or sell the Building or the Project, (f) that the use sought tobe permitted pursuant to the appeal or contest would be inconsistent with otheruses of the Building or (g) that such appeal or contest would be likely toimpair the value of the Building and/or the Project.  Tenant will not use or permit the Premises tobe used for any purpose or in any manner that would void Tenant’s or Landlord’sinsurance, increase the insurance risk above the risk level of other occupantsat the Project, or cause the disallowance of any sprinkler or othercredits.  Tenant shall not permit anypart of the Premises to be used as a “place of public accommodation”, asdefined in the ADA or any similar legal requirement.  Tenant shall reimburse Landlord promptly upondemand for any additional premium charged for any such insurance policy byreason of Tenant’s failure to comply with the provisions of this Section orotherwise caused by Tenant’s use and/or occupancy of the Premises.  Tenant will use the Premises in a careful,safe and proper manner and will not commit or permit waste, overload the flooror structure of the Premises, subject the Premises to use that would damage thePremises or obstruct or interfere with the rights of Landlord or other tenantsor occupants of the Project, including conducting or giving notice of anyauction, liquidation, or going out of business sale on the Premises, or usingor allowing the Premises to be used for any unlawful purpose.  Tenant shall cause any equipment or machineryto be installed in the Premises so as to reasonably prevent sounds orvibrations from the Premises from extending into Common Areas, or other spacein the Project.  Tenant shall not placeany machinery or equipment weighing 500 pounds or more in or upon the Premisesor transport or move such items through the Common Areas of the Project or inthe Project elevators without the prior written consent of Landlord.  Except as may be provided under the WorkLetter, Tenant shall not, without the prior written consent of Landlord, usethe Premises in any manner which will require ventilation, air exchange,heating, gas, steam, electricity or water beyond the existing capacity of theProject as proportionately allocated to the Premises based upon Tenant’s Shareas usually furnished for the Permitted Use.

Landlord shall, as anOperating Expense (except as set forth in Section 5(b) (to the extent suchLegal Requirement is generally applicable to similar buildings in the area inwhich the Project is located) or at Tenant’s expenses (to the extent such LegalRequirement is applicable solely by reason of Tenant’s, as compared to othertenants of the Project, particular use of the Premises) make any alterations ormodifications to the Common Areas or the exterior of the Building that arerequired by Legal Requirements, including the ADA. Tenant, at its sole expense, shall make any alterations or modificationsto the interior of the Premises that are required by Legal Requirements(including, without limitation, compliance of the Premises with the ADA.  Notwithstanding any other provisionherein to the contrary, Tenant shall be responsible for any and all demands,claims, liabilities, losses, costs, expenses,

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actions, causes ofaction, damages or judgments, and all reasonable expenses incurred ininvestigating or resisting the same (including, without limitation, reasonableattorneys’ fees, charges and disbursements and costs of suit) (collectively, “**Claims**”) arising out of or in connection with LegalRequirements, and Tenant shall indemnify, defend, hold and save Landlordharmless from and against any and all Claims arising out of or in connectionwith any failure of the Premises to comply with any Legal Requirement;provided, however, that Tenant shall not be so responsible or be obligated toindemnify, defend or hold harmless under this paragraph with respect to thefailure of the Premises to comply with Legal Requirements except to the extentthat such failure to so comply arises by reason of Tenant’s use of the Premisesor Tenant’s actions or omissions or relates to the Tenant Improvementsconstructed under the Work Letter or Alterations (as that term is defined inSection 12) made by Tenant.

8.             **Holding Over**.  If, with Landlord’s express written consent,Tenant retains possession of the Premises after the termination of the Term,(i) unless otherwise agreed in such written consent, such possession shall besubject to immediate termination by Landlord at any time, (ii) all of the otherterms and provisions of this Lease (including, without limitation, theadjustment of Base Rent pursuant to Section 4 hereof) shall remain infull force and effect (excluding any expansion or renewal option or othersimilar right or option) during such holdover period, (iii) Tenant shallcontinue to pay Base Rent in the amount payable upon the date of the expirationor earlier termination of this Lease or such other amount as Landlord mayindicate, in Landlord’s sole and absolute discretion, in such written consent,and (iv) all other payments shall continue under the terms of this Lease.  If Tenant remains in possession of thePremises after the expiration or earlier termination of the Term without theexpress written consent of Landlord, (A) Tenant shall become a tenant atsufferance upon the terms of this Lease except that the monthly rental shall beequal to 150% of Rent in effect during the last 30 days of the Term and Tenantshall pay on account therefor on a per diem basis at such monthly rental ratefor each day that Tenant so retains possession, and (B) Tenant shall beresponsible for all damages suffered by Landlord resulting from or occasionedby Tenant’s holding over, including consequential damages.  No holding over by Tenant, whether with orwithout consent of Landlord, shall operate to extend this Lease except asotherwise expressly provided, and this Section 8 shall not be construedas consent for Tenant to retain possession of the Premises.  Acceptance by Landlord of Rent after theexpiration of the Term or earlier termination of this Lease shall not result ina renewal or reinstatement of this Lease.

9.             **Taxes**.  Landlord shallpay, as part of Operating Expenses, all taxes, levies, assessments andgovernmental charges of any kind (collectively referred to as “**Taxes**”) imposed by any federal, state, regional, municipal,local or other governmental authority or agency, including, without limitation,quasi-public agencies (collectively, “**Governmental Authority**”)during the Term, including, without limitation, all Taxes:  (i) imposed on or measured by or based, inwhole or in part, on rent payable to Landlord under this Lease and/or from therental by Landlord of the Project or any portion thereof, or (ii) based on thesquare footage, assessed value or other measure or evaluation of any kind ofthe Premises or the Project, or (iii) assessed or imposed by or on theoperation or maintenance of any portion of the Premises or the Project,including parking, or (iv) assessed or imposed by, or at the direction of, orresulting from statutes or regulations, or interpretations thereof, promulgatedby, any Governmental Authority, (v) imposed as a license or other fee onLandlord’s business of leasing space in the Project, or (vi) assessed orimposed by or on the operation or maintenance of any portion or whole of theCondominium (provided that to the extent any Taxes are assessed against theCondominium as a whole, such amounts shall be allocated among the buildingslocated in the Condominium based on the square footage of the buildings inquestion, unless Landlord reasonably determines that such allocation should bemade on another basis).  Landlord maycontest by appropriate legal proceedings the amount, validity, or applicationof any Taxes or liens securing Taxes. Taxes shall not include any net income taxes imposed on Landlord unlesssuch net income taxes are in substitution for any Taxes payable hereunder.  If any such Tax is levied or assesseddirectly against Tenant, then Tenant shall be responsible for and shall pay thesame at such times and in such manner as the taxing authority shallrequire.  Tenant shall pay, prior todelinquency, any and all Taxes levied or assessed against any personal propertyor trade fixtures placed by Tenant in the Premises, whether levied or assessedagainst Landlord or Tenant.  If any Taxeson Tenant’s personal property or trade fixtures are levied against Landlord orLandlord’s property, or if the assessed valuation of the Project is increasedby a value attributable to improvements in or alterations to the Premises,whether owned by Landlord or Tenant and whether or not affixed to the realproperty so as

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to become a part thereof, higher than the base valuation on whichLandlord from time-to-time allocates Taxes to all tenants in the Project,Landlord shall have the right, but not the obligation, to pay such Taxes.  Landlord’s determination of any excessassessed valuation shall be binding and conclusive, absent manifest error.  The amount of any such payment by Landlordshall constitute Additional Rent due from Tenant to Landlord immediately upondemand.

10.           **Parking**.  Subject toForce Majeure, a Taking (as defined in Section 19 below) and theexercise by Landlord of its rights hereunder, Tenant shall have the right, incommon with other tenants of the Project, to the non-exclusive use of 1.5parking spaces for every 1,000 rentable square feet of the Premises (which,based on 44,084 rentable square feet, equates to 66 parking spaces), whichspaces shall be located in the Technology Square Garage in those areasdesignated for non-reserved parking, subject in each case to Landlord’s rulesand regulations.  Tenant shall pay toLandlord or as directed by Landlord, monthly as Additional Rent hereunder, themarket rate for each parking space, as reasonably determined by Landlord fromtime to time, which as of the date hereof shall be $220.00 per space permonth.  Landlord shall not be responsiblefor enforcing Tenant’s parking rights against any third parties, includingother tenants of the Project*.*  Tenant shall, at Tenant’s soleexpense, for so long as the Parking and Traffic Demand Management Plan datedMay 9, 1999 as approved by the City of Cambridge on July 9, 1999, including theconditions set forth in such approval (as amended from time to time, the “**PTDM**”), remains applicable to theCondominium, (i) offer to subsidize mass transit monthly passes for all of itsemployees; (ii) implement a Commuter Choice Program; (iii) discouragesingle-occupant vehicle (“**SOV**”)use by its employees; (iv) promote alternative modes of transportation and useof alternative work hours; (v) meet with Landlord and/or its representatives nomore than quarterly discuss transportation programs and initiatives; (vi)participate in annual surveys monitoring transportation programs andinitiatives at Technology Square; (vii) cooperate with Landlord in connectionwith transportation programs and initiatives promulgated pursuant to the PTDM;(viii) provide alternative work programs (such as telecommuting, flex-time andcompressed work weeks) to its employees in order to reduce traffic impacts inCambridge during peak commuter hours; and (ix) otherwise cooperate withLandlord in encouraging employees to seek alternate modes of transportation.

11.           **Utilities, Services.**  Landlord shall provide, subject to the termsof this Section 11, water, electricity, heat, light, power, telephone,sewer, and other utilities (including gas and fire sprinklers to the extent theProject is plumbed for such services), refuse and trash collection andjanitorial services (collectively, “**Utilities**”).  Landlord shall pay, as Operating Expenses orsubject to Tenant’s reimbursement obligation, for all Utilities used on thePremises, all maintenance charges for Utilities, and any storm sewer charges orother similar charges for Utilities imposed by any Governmental Authority orUtility provider, and any taxes, penalties, surcharges or similar chargesthereon.  Landlord shall cause, at Tenant’sexpense, any Utilities to be separately metered, check-metered or chargeddirectly to Tenant by the provider. Tenant shall pay directly to the Utility provider, prior to delinquency,any separately metered Utilities and services which may be furnished to Tenantor the Premises during the Term.  Tenantshall pay, as part of Operating Expenses, its share of all charges for jointlymetered Utilities based upon consumption, as reasonably determined by Landlordpursuant to any check-meter installed pursuant to this paragraph.  No interruption or failure of Utilities, fromany cause whatsoever other than Landlord’s willful misconduct, shall result ineviction or constructive eviction of Tenant, termination of this Lease or theabatement of Rent.  Tenant agrees tolimit use of water and sewer with respect to Common Areas to normal restroomuse.  Landlord’s sole obligation foreither providing emergency generators or providing emergency back-up power toTenant shall be: (i) to provide emergency generators with not less than thestated capacity of the emergency generators located in the Building as of theCommencement Date, and (ii) to contract with a third party to maintain theemergency generators as per the manufacturer’s standard maintenanceguidelines.  Landlord shall have noobligation to provide Tenant with operational emergency generators or back-uppower or to supervise, oversee or confirm that the third party maintaining theemergency generators is maintaining the generators as per the manufacturer’sstandard guidelines or otherwise.  Duringany period of replacement, repair or maintenance of the emergency generatorswhen the emergency generators are not operational, including any delays theretodue to the inability to obtain parts or replacement equipment, Landlord shallhave no obligation to provide Tenant with an alternative back-up generator orgenerators or alternative sources of back-up power.  Tenant expressly acknowledges and agrees thatLandlord does not guaranty that such emergency generators will be

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operational at all times or that emergency power will be available tothe Premises when needed.  In no eventshall Landlord be liable to Tenant or any other party for any damages of anytype, whether actual or consequential, suffered by Tenant or any such otherperson in the event that any emergency generator or back-up power or anyreplacement thereof fails or does not provide sufficient power.

12.           **Alterations and Tenant’s Property**.  Except for Tenant Improvements (as defined inthe Work Letter), which shall be governed by the Work Letter, any alterations,additions, or improvements made to the Premises by or on behalf of Tenant,including additional locks or bolts of any kind or nature upon any doors orwindows in the Premises, but excluding installation, removal or realignment offurniture systems (other than removal of furniture systems owned or paid for byLandlord) not involving any modifications to the structure or connections(other then by ordinary plugs or jacks) to Building Systems (as defined in Section 13)(“**Alterations**”) shall be subject toLandlord’s prior written consent, which may be given or withheld in Landlord’ssole discretion if any such Alteration affects the structure or BuildingSystems, but which shall otherwise not be unreasonably withheld ordelayed.  Tenant may constructnonstructural Alterations that will not affect the Building Systems orotherwise interfere with the occupants of the Project in the Premises withoutLandlord’s prior approval if the aggregate cost of all such work in any 12month period does not exceed $150,000 (a “Notice-Only Alteration”), providedTenant notifies Landlord in writing of such intended Notice-Only Alteration,and such notice shall be accompanied by plans, specifications, work contractsand such other information concerning the nature and cost of the Notice-OnlyAlteration as may be reasonably requested by Landlord, which notice andaccompanying materials shall be delivered to Landlord not less than 15 businessdays in advance of any proposed construction. If Landlord approves any Alterations, Landlord may impose suchconditions on Tenant in connection with the commencement, performance andcompletion of such Alterations as Landlord may deem appropriate in Landlord’sreasonable discretion.  Any request forapproval shall be in writing, delivered not less than 15 business days inadvance of any proposed construction, and accompanied by plans, specifications,bid proposals, work contracts and such other information concerning the natureand cost of the alterations as may be reasonably requested by Landlord,including the identities and mailing addresses of all persons performing workor supplying materials.  Landlord’s rightto review plans and specifications and to monitor construction shall be solelyfor its own benefit, and Landlord shall have no duty to ensure that such plansand specifications or construction comply with applicable LegalRequirements.  Tenant shall cause, at itssole cost and expense, all Alterations to comply with insurance requirementsand with Legal Requirements and shall implement at its sole cost and expenseany alteration or modification required by Legal Requirements as a result ofany Alterations.  Tenant shall pay toLandlord, as Additional Rent, on demand an amount equal to 10% of all chargesincurred by Tenant or its contractors or agents in connection with anyAlteration to cover Landlord’s overhead and expenses for plan review,coordination, scheduling and supervision. Before Tenant begins any Alteration, Landlord may post on and about thePremises notices of non-responsibility pursuant to applicable law.  Tenant shall reimburse Landlord for, andindemnify and hold Landlord harmless from, any expense incurred by Landlord byreason of faulty work done by Tenant or its contractors, delays caused by suchwork, or inadequate cleanup.

Tenant shall furnish security or make otherarrangements satisfactory to Landlord in its reasonable discretion to assurepayment for the completion of all Alterations work free and clear of liens, andshall provide (and cause each contractor or subcontractor to provide)certificates of insurance for workers’ compensation and other coverage inamounts and from an insurance company satisfactory to Landlord protectingLandlord against liability for personal injury or property damage duringconstruction.  Upon completion of anyAlterations, Tenant shall deliver to Landlord: (i) sworn statements setting forth the names of all contractors andsubcontractors who did the work and final lien waivers from all suchcontractors and subcontractors; and (ii) “as built” plans for any suchAlteration.

Other than (i) the items, if any, listed on **Exhibit F** attached hereto, (ii) any items agreed by Landlordin writing to be included on **Exhibit F** inthe future, and (iii) any trade fixtures, machinery, equipment and otherpersonal property not paid for out of the TI Fund (as defined in the WorkLetter) which may be removed without material damage to the Premises, whichdamage shall be repaired (including capping or terminating utility hook-ups behindwalls) by Tenant during the Term (collectively, “**Tenant’sProperty**”), all property of any kind paid for with the TI Fund, allAlterations, real property

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fixtures, built-inmachinery and equipment, built-in casework and cabinets and other similaradditions and improvements built into the Premises so as to become an integralpart of the Premises such as fume hoods which penetrate the roof or plenumarea, built-in cold rooms, built-in warm rooms, walk-in cold rooms, walk-inwarm rooms, deionized water systems, glass washing equipment, autoclaves,chillers, built-in plumbing, electrical and mechanical equipment and systems,and any power generator and transfer switch (collectively, “**Installations**”) shall be and shall remain the property ofLandlord during the Term and following the expiration or earlier termination ofthe Term, shall not be removed by Tenant at any time during the Term and shallremain upon and be surrendered with the Premises as a part thereof inaccordance with Section 28 following the expiration or earliertermination of this Lease; provided, however, that Landlordshall, at the time its approval of such Installation is requested or at thetime it receives notice of a Notice-Only Alteration notify Tenant if it haselected to cause Tenant to remove such Installation upon the expiration orearlier termination of this Lease (it being understood that Landlord shall notrequire Tenant to remove any alterations, additions, improvements, fixtures orequipment in the Premises as of the Commencement Date or alterations that arein the nature of typical office fit-up). If Landlord so elects, Tenant shall remove such Installation upon theexpiration or earlier termination of this Lease and restore any damage causedby or occasioned as a result of such removal, including, when removing any ofTenant’s Property which was plumbed, wired or otherwise connected to any of theBuilding Systems, capping off all such connections behind the walls of thePremises and repairing any holes.  Duringany such restoration period, Tenant shall pay Rent to Landlord as providedherein as if said space were otherwise occupied by Tenant.

13.           **Landlord’s Repairs**. Landlord, as an Operating Expense (subject to the terms of Section 5),shall maintain all of the structural, exterior, parking and other Common Areasof the Project, including HVAC, plumbing, fire sprinklers, elevators and allother building systems serving the Premises and other portions of the Project (“**Building Systems**”), in good repair, reasonable wear and tearand uninsured losses and damages caused by Tenant, or by any of Tenant’sagents, servants, employees, invitees and contractors (collectively, “**Tenant Parties**”) excluded; for the avoidance of doubt,uninsured losses shall not mean losses for which Landlord is required tomaintain insurance hereunder and for which Landlord fails to maintain suchrequired insurance.  Losses and damagescaused by Tenant or any Tenant Party shall be repaired by Landlord, to theextent not covered by insurance, at Tenant’s sole cost and expense.  Landlord reserves the right to stop BuildingSystems services when necessary (i) by reason of accident or emergency, or (ii)for planned repairs, alterations or improvements, which are, in the judgment ofLandlord, desirable or necessary to be made, until said repairs, alterations orimprovements shall have been completed. Landlord shall have no responsibility or liability for failure to supplyBuilding Systems services during any such period of interruption; provided,however, that Landlord shall, except in case of emergency, make acommercially reasonable effort to give Tenant 24 hours advance notice of anyplanned stoppage of Building Systems services for routine maintenance, repairs,alterations or improvements.  Landlordagrees to use commercially reasonable efforts not to interfere with the conductof Tenant’s ordinary business operations at the Premises during access of thePremises.  Tenant shall promptly giveLandlord written notice of any repair required by Landlord pursuant to this Section,after which Landlord shall have a reasonable opportunity to effect suchrepair.  Landlord shall not be liable forany failure to make any repairs or to perform any maintenance unless suchfailure shall persist for an unreasonable time after Tenant’s written notice ofthe need for such repairs or maintenance. Tenant waives its rights under any state or local law to terminate thisLease or to make such repairs at Landlord’s expense and agrees that the parties’respective rights with respect to such matters shall be solely as set forthherein.  Repairs required as the resultof fire, earthquake, flood, vandalism, war, or similar cause of damage ordestruction shall be controlled by Section 18.

14.           **Tenant’s Repairs**. Subject to Section 13 hereof, Tenant, at its expense, shallrepair, replace and maintain in the same condition as of the Commencement Dateor as thereafter improved in compliance with the terms hereof, reasonable wearand tear, Landlord’s repair obligations, any damage directly resulting fromdefault by Landlord, a fire or other casualty that is governed by Section 18and uninsured losses not caused by Tenant or any Tenant Party excepted, allportions of the Premises, including, without limitation, entries, doors,ceilings, interior windows, interior walls, and the interior side of demisingwalls; for the avoidance of doubt, uninsured losses shall not mean losses forwhich Tenant is required to maintain insurance hereunder and for which Tenantfails to maintain such required insurance.

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Such repair and replacement may include capital expenditures andrepairs whose benefit may extend beyond the Term.  Should Tenant fail to make any such repair orreplacement or fail to maintain the Premises, Landlord shall give Tenant noticeof such failure.  If Tenant fails tocommence cure of such failure within 10 days of Landlord’s notice, andthereafter diligently prosecute such cure to completion, Landlord may performsuch work and shall be reimbursed by Tenant within 10 days after demandtherefor for the reasonable out-of-pocket costs of such cure; provided,however, that if such failure by Tenant creates or could create an emergency,Landlord may immediately commence cure of such failure and shall thereafter beentitled to recover the costs of such cure from Tenant.  Subject to Sections 17 and 18,Tenant shall bear the full uninsured cost of any repair or replacement to anypart of the Project that results from damage caused by Tenant or any TenantParty and any repair that benefits only the Premises.

15.           **Mechanic’s Liens**.  Tenant shall discharge, by bond or otherwise,any mechanic’s lien filed against the Premises or against the Project for workclaimed to have been done for, or materials claimed to have been furnished to,Tenant within 10 days after the filing thereof, at Tenant’s sole cost and shallotherwise keep the Premises and the Project free from any liens arising out ofwork performed, materials furnished or obligations incurred by Tenant.  Should Tenant fail to discharge any lien describedherein, Landlord shall have the right, but not the obligation, to pay suchclaim or post a bond or otherwise provide security to eliminate the lien as aclaim against title to the Project and the cost thereof shall be immediatelydue from Tenant as Additional Rent.  IfTenant shall lease or finance the acquisition of office equipment, furnishings,or other personal property of a removable nature utilized by Tenant in theoperation of Tenant’s business, Tenant warrants that any Uniform CommercialCode Financing Statement filed as a matter of public record by any lessor orcreditor of Tenant will upon its face or by exhibit thereto indicate that suchFinancing Statement is applicable only to removable personal property of Tenantlocated within the Premises.  In no eventshall the address of the Project be furnished on the statement withoutqualifying language as to applicability of the lien only to removable personalproperty, located in an identified suite held by Tenant.

16.           **Indemnification**.  Tenant hereby indemnifies and agrees todefend, save and hold Landlord harmless from and against any and all Claims forinjury or death to persons or damage to property occurring within or about thePremises, arising directly or indirectly out use or occupancy of the Premises ora breach or default by Tenant in the performance of any of its obligationshereunder, unless caused solely by the willful misconduct or negligence ofLandlord.  Landlord shall not be liableto Tenant for, and Tenant assumes all risk of damage to, personal property(including, without limitation, loss of records kept within the Premises).  Tenant further hereby irrevocably waives anyand all Claims for injury to Tenant’s business or loss of income relating toany such damage or destruction of personal property (including, withoutlimitation, any loss of records), unless caused by the willful misconduct ornegligence of Landlord.  Landlord shallnot be liable for any damages arising from any act, omission or neglect of anytenant in the Project or of any other third party.

17.           **Insurance**.  Landlordshall maintain all risk property and, if applicable, sprinkler damage insurancecovering the full replacement cost of the Project or such lesser coverageamount as Landlord may elect provided such coverage amount is not lessthan 90% of such full replacement cost, including Tenant Improvements (asdefined in and constructed pursuant to the Work Letter).  Landlord shall further procure and maintaincommercial general liability insurance with a single loss limit of not lessthan $2,000,000 for bodily injury and property damage with respect to theProject.  Landlord may, but is notobligated to, maintain such other insurance and additional coverages as it maydeem necessary, including, but not limited to, flood, environmental hazard andearthquake, loss or failure of building equipment, errors and omissions, rentalloss during the period of repair or rebuilding, workers’ compensation insuranceand fidelity bonds for employees employed to perform services and insurance forany improvements installed by Tenant or which are in addition to the standardimprovements customarily furnished by Landlord without regard to whether or notsuch are made a part of the Project.  Allsuch insurance shall be included as part of the Operating Expenses.  The Project may be included in a blanketpolicy (in which case the cost of such insurance allocable to the Project willbe determined by Landlord based upon the insurer’s cost calculations).  Tenant shall also reimburse Landlord for any

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increased premiums or additional insurance which Landlord reasonablydeems necessary as a result of Tenant’s use of the Premises.

Tenant, at its sole cost and expense, shall maintainduring the Term:  all risk propertyinsurance with business interruption and extra expense coverage, covering thefull replacement cost of all property and improvements installed or placed inthe Premises by Tenant at Tenant’s expense; workers’ compensation insurancewith no less than the minimum limits required by law; employer’s liabilityinsurance with such limits as required by law; and commercial general liabilityinsurance, with a minimum limit of not less than $2,000,000 per occurrence forbodily injury and property damage with respect to the Premises.**The commercial general liabilityinsurance policy shall name Landlord, its officers, directors, employees,managers, agents, invitees and contractors and the Additional Insured Parties(as defined in the next succeeding paragraph) (collectively, “**Landlord Parties**”), as additional insureds; insure on anoccurrence and not a claims-made basis; be issued by insurance companies whichhave a rating of not less than policyholder rating of A and financial categoryrating of at least Class X in “Best’s Insurance Guide”; shall not be cancelablefor nonpayment of premium unless 30 days prior written notice shall have beengiven to Landlord from the insurer; contain a hostile fire endorsement and acontractual liability endorsement; and provide primary coverage to Landlord(any policy issued to Landlord providing duplicate or similar coverage shall bedeemed excess over Tenant’s policies). Copies of such policies (if requested by Landlord), or certificates of insurance showing the limits ofcoverage required hereunder and showing Landlord as an additional insured,along with reasonable evidence of the payment of premiums for the applicableperiod, shall be delivered to Landlord by Tenant upon commencement of the Termand upon each renewal of said insurance. Tenant’s policy may be a “blanket policy” with an aggregate per locationendorsement which specifically provides that the amount of insurance shall notbe prejudiced by other losses covered by the policy.  Tenant shall, at least 5 days prior to theexpiration of such policies, furnish Landlord with renewal certificates.

In each instance where insurance is to name Landlordas an additional insured, Tenant shall upon written request of Landlord alsodesignate and furnish certificates so evidencing Landlord as additional insuredto the following parties (collectively “**AdditionalInsured Parties**”):  (i) anylender of Landlord holding a security interest in the Project or any portionthereof and any servicer in connection therewith, (ii) the landlord under anylease wherein Landlord is tenant of the real property on which the Project islocated, if the interest of Landlord is or shall become that of a tenant undera ground or other underlying lease rather than that of a fee owner, (iii) anymanagement company retained by Landlord to manage the Project, (iv) thecondominium association with respect to the Condominium, (v) any member,partner or shareholder of Landlord or the owner of any beneficial interesttherein or (vi) any other party reasonably designated by Landlord.

The property insurance obtained by Landlord and Tenantshall include a waiver of subrogation by the insurers and all rights based uponan assignment from its insured, against Landlord or Tenant, and theirrespective officers, directors, employees, managers, agents, invitees and contractors(“**Related Parties**”), in connection withany loss or damage thereby insured against. Neither party nor its respective Related Parties shall be liable to theother for loss or damage caused by any risk insured against under property insurancerequired to be maintained hereunder, and each party waives any claims againstthe other party, and its respective Related Parties, for such loss ordamage.  The failure of a party to insureits property shall not void this waiver. Landlord and its respective Related Parties shall not be liable for, andTenant hereby waives all claims against such parties for, business interruptionand losses occasioned thereby sustained by Tenant or any person claimingthrough Tenant resulting from any accident or occurrence in or upon thePremises or the Project from any cause whatsoever unless due to Landlord’swillful misconduct or gross negligence. If the foregoing waivers shall contravene any law with respect toexculpatory agreements, the liability of Landlord or Tenant shall be deemed notreleased but shall be secondary to the other’s insurer.

Landlord may require insurance policy limits to beraised to conform with requirements of Landlord’s lender and/or to bringcoverage limits to levels then being generally required of new tenants of ClassA laboratory/office buildings in the Kendall Square, Cambridge, Massachusettsarea.

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18.           **Restoration**.  If, at any time during the Term, the Projector the Premises are damaged or destroyed by a fire or other casualty, Landlordshall notify Tenant within 60 days after discovery of such damage as to theamount of time Landlord reasonably estimates it will take to restore theProject or the Premises, as applicable (the “**RestorationPeriod**”).  If the RestorationPeriod is estimated to exceed 18 months from the date of such casualty(the “**Maximum Restoration Period**”) or if thecasualty is an uninsured casualty, (which, for the avoidance of doubt, shallnot include casualties for which Landlord is required to maintain insurancehereunder and for which Landlord fails to maintain such required insurance),Landlord may, in such notice, elect to terminate this Lease as of the date thatis 75 days after the date of discovery of such damage or destruction*;*provided,however, thatnotwithstanding Landlord’s election to restore, Tenant may elect to terminatethis Lease by written notice to Landlord delivered within 5 business days ofreceipt of a notice from Landlord estimating a Restoration Period for thePremises longer than the Maximum Restoration Period.  Unless either Landlord or Tenant so elects toterminate this Lease, Landlord shall, subject to receipt of sufficientinsurance proceeds (with any deductible to be treated as a current OperatingExpense), promptly restore the Premises (including the Tenant Improvements, asdefined in and constructed pursuant to the Work Letter) (excluding theimprovements installed by Tenant or by Landlord and paid for by Tenant),subject to delays arising from the collection of insurance proceeds, from ForceMajeure events or as needed to obtain any license, clearance or otherauthorization of any kind required to enter into and restore the Premisesissued by any Governmental Authority having jurisdiction over Tenant’s use,storage, handling, treatment, generation, release, disposal, removal orremediation of Hazardous Materials (as defined in Section 30) in, on orabout the Premises (collectively referred to herein as “**HazardousMaterials Clearances**”); provided, however, that ifrepair or restoration of the Premises is not substantially complete as of theend of the Maximum Restoration Period or, if longer, the Restoration Period,Landlord may, in its sole and absolute discretion, elect not to proceed withsuch repair and restoration, or Tenant may by written notice to Landlorddelivered within 10 business days of the expiration of the Maximum RestorationPeriod or, if longer, the Restoration Period, elect to terminate this Lease, inwhich event Landlord shall be relieved of its obligation to make such repairsor restoration and this Lease shall terminate as of the date that is 75 daysafter the later of:  (i) discovery of suchdamage or destruction, or (ii) the date all Hazardous Materials Clearancesrequired to be obtained by Tenant are obtained, but Landlord shall retain anyRent paid and the right to any Rent payable by Tenant prior to such election byLandlord or Tenant.

Tenant, at its expense, shall promptly perform,subject to delays arising from the collection of insurance proceeds, from ForceMajeure (as defined in Section 34) events or to obtain HazardousMaterial Clearances, all repairs or restoration not required to be done byLandlord and shall promptly re-enter the Premises and commence doing businessin accordance with this Lease. Notwithstanding the foregoing, Landlord may terminate this Lease if thePremises are damaged during the last 12 months of the Term and Landlordreasonably estimates that it will take more than 2 months to repair such damage, or ifinsurance proceeds are not available for such restoration.  Rent shall be abated from the date allrequired Hazardous Material Clearances are obtained until the Premises arerepaired and restored, in the proportion which the area of the Premises, ifany, which is not usable by Tenant bears to the total area of the Premises,unless Landlord provides Tenant with other space during the period of repairthat is suitable for the temporary conduct of Tenant’s business.  Such abatement shall be the sole remedy ofTenant, and except as provided in this Section 18, Tenant waives anyright to terminate the Lease by reason of damage or casualty loss.

The provisions of this Lease, including this Section18, constitute an express agreement between Landlord and Tenant withrespect to any and all damage to, or destruction of, all or any part of thePremises, or any other portion of the Project, and any statute or regulation whichis now or may hereafter be in effect shall have no application to this Lease orany damage or destruction to all or any part of the Premises or any otherportion of the Project, the parties hereto expressly agreeing that this Section18 sets forth their entire understanding and agreement with respect to suchmatters.

19.           **Condemnation**.

(a)           If the whole or any material part ofthe Premises or the Project is taken for any public or quasi-public use undergovernmental law, ordinance, or regulation, or by right of eminent domain, orby

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private purchase in lieu thereof (a “**Taking**” or “**Taken**”), andthe Taking would either prevent or materially interfere with Tenant’s use ofthe Premises or materially interfere with or impair Landlord’s ownership oroperation of the Project, then upon written notice (a “**Termination Notice**”) by Landlord or Tenantthis Lease shall terminate and Rent shall be apportioned as of said date,subject to the provisions of Section 19(b) below.  If part of the Premises shall be Taken, and thisLease is not terminated as provided above, Landlord shall promptly restore thePremises and the Project as nearly as is commercially reasonable under thecircumstances to their condition prior to such partial Taking and the rentablesquare footage of the Building, the rentable square footage of the Premises,Tenant’s Share of Operating Expenses and the Rent payable hereunder during theunexpired Term shall be reduced to such extent as may be fair and reasonableunder the circumstances.  Upon any such Taking,Landlord shall be entitled to receive the entire price or award from any suchTaking without any payment to Tenant, and Tenant hereby assigns to LandlordTenant’s interest, if any, in such award. Tenant shall have the right, to the extent that same shall not diminishLandlord’s award, to make a separate claim against the condemning authority(but not Landlord) for such compensation as may be separately awarded orrecoverable by Tenant for moving expenses and damage to Tenant’s tradefixtures, if a separate award for such items is made to Tenant.  Tenant hereby waives any and all rights itmight otherwise have pursuant to any provision of state law to terminate thisLease upon a partial Taking of the Premises or the Project.

(b)          Evaluation.

(i)            If either party sends a TerminationNotice and the other believes it was wrongly sent, then such objecting partyshall so notify the other party within 10 days of such Termination Notice.  Landlord and Tenant shall then meet within 7days and make a good faith attempt to mutually appoint a single Evaluator(defined below) to determine whether the Termination Notice was properlysent.  If Landlord and Tenant are unableto agree upon a single Evaluator, then each shall, by written notice deliveredto the other within 10 days after the meeting, select an Evaluator.  If either party fails to timely give noticeof its selection for an Evaluator, the other party’s position regarding theTermination Notice shall conclusively be deemed correct.  The 2 Evaluators so appointed shall, within 5business days after their appointment, appoint a third Evaluator.  If the 2 Evaluators so selected cannot agreeon the selection of the third Evaluator within the time above specified, theneither party, on behalf of both parties, may request such appointment of suchthird Evaluator by application to any state court of general jurisdiction inthe jurisdiction in which the Premises are located, upon 10 days prior writtennotice to the other party of such intent.

(ii)           The decision of the Evaluator(s)shall be made within 30 days after the appointment of a single Evaluator or thethird Evaluator, as applicable.  Thedecision of the single Evaluator shall be final and binding upon the parties.  The agreement of two Evaluators in a threeEvaluator panel shall be final and binding upon the parties.  Each party shall pay the fees and expenses ofthe Evaluator appointed by or on behalf of such party and the fees and expensesof the third Evaluator shall be borne equally by both parties.

(iii)          An “Evaluator” shall be any personappointed by or on behalf of either party or appointed pursuant to theprovisions hereof and (i) shall be a licensed commercial real estate brokerwith not less than 15 years experience representing landlords and/or tenants inthe leasing of high tech or life sciences space in the greater Bostonmetropolitan area and (ii) be in all respects impartial and disinterested.

20.          **Events of Default**.  Each of the following events shall be adefault (“**Default**”) by Tenant under this Lease:

(a)           **Payment Defaults**.  Tenant shall fail to pay any installment ofRent or any other payment hereunder when due; provided, however, that Landlordwill give Tenant notice and an opportunity to cure any failure to pay Rentwithin 5 days of any such notice not more than once in any 12 month period andTenant agrees that such notice shall be in lieu of and not in addition to, orshall be deemed to be, any notice required by law.

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(b)           **Insurance**.  Any insurance required to be maintained byTenant pursuant to this Lease shall be canceled or terminated or shall expireor shall be reduced or materially changed, or Landlord shall receive a noticeof nonrenewal of any such insurance and Tenant shall fail to obtain replacementinsurance at least 20 days before the expiration of the current coverage.

(c)           **Abandonment**.  Tenant shall abandon the Premises.

(d)           **Improper Transfer**.  Tenant shall assign, sublease or otherwisetransfer or attempt to transfer all or any portion of Tenant’s interest in thisLease or the Premises except as expressly permitted herein, or Tenant’sinterest in this Lease shall be attached, executed upon, or otherwisejudicially seized and such action is not released within 90 days of the action.

(e)           **Liens**.  Tenant shall fail to discharge or otherwise obtainthe release of any lien placed upon the Premises in violation of this Leasewithin 10 days after any such lien is filed against the Premises.

(f)            **Insolvency Events**.  Tenant or any guarantor or surety of Tenant’sobligations hereunder shall:  (A) make ageneral assignment for the benefit of creditors; (B) commence any case,proceeding or other action seeking to have an order for relief entered on itsbehalf as a debtor or to adjudicate it a bankrupt or insolvent, or seekingreorganization, arrangement, adjustment, liquidation, dissolution orcomposition of it or its debts or seeking appointment of a receiver, trustee,custodian or other similar official for it or for all or of any substantialpart of its property (collectively a “**Proceeding for Relief**”);(C) become the subject of any Proceeding for Relief which is not dismissedwithin 90 days of its filing or entry; or (D) die or suffer a legal disability(if Tenant, guarantor, or surety is an individual) or be dissolved or otherwisefail to maintain its legal existence (if Tenant, guarantor or surety is acorporation, partnership or other entity).

(g)           **Estoppel Certificate orSubordination Agreement.** Tenant fails to execute any document required from Tenant under Sections23 or 27 within 10 days after a second written notice requestingsuch document.

(h)           **Other Defaults**.  Tenant shall fail to comply with anyprovision of this Lease other than those specifically referred to in this Section20, and, except as otherwise expressly provided herein, such failure shallcontinue for a period of 30 days after written notice thereof from Landlord toTenant.

Any notice given under Section 20(h) hereofshall:  (i) specify the alleged default,(ii) demand that Tenant cure such default, (iii) be in lieu of, and not in additionto, or shall be deemed to be, any notice required under any provision ofapplicable law, and (iv) not be deemed a forfeiture or a termination of thisLease unless Landlord elects otherwise in such notice; provided that ifthe nature of Tenant’s default pursuant to Section 20(h) is such that itcannot be cured by the payment of money and reasonably requires more than 30days to cure, then Tenant shall not be deemed to be in default if Tenantcommences such cure within said 30 day period and thereafter diligentlyprosecutes the same to completion; provided, however, that suchcure shall be completed no later than 90 days from the date of Landlord’snotice.

21.           **Landlord’sRemedies.**

(a)           **PaymentBy Landlord; Interest.**  Upon aDefault by Tenant hereunder, Landlord may, without waiving or releasing anyobligation of Tenant hereunder, make such payment or perform such act.  All sums so paid or incurred by Landlord,together with interest thereon, from the date such sums were paid or incurred,at the annual rate equal to 12% per annum or the highest rate permitted by law(the “Default Rate”), whichever is less, shall be payable to Landlord on demandas additional Rent.  Nothing herein shallbe construed to create or impose a duty on Landlord to mitigate any damagesresulting from Tenant’s Default hereunder.

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(b)           **LatePayment Rent.**  Late payment byTenant to Landlord of Rent and other sums due will cause Landlord to incurcosts not contemplated by this Lease, the exact amount of which will beextremely difficult and impracticable to ascertain.  Such costs include, but are not limited to,processing and accounting charges and late charges which may be imposed onLandlord under any Mortgage covering the Premises.  Therefore, if any installment of Rent duefrom Tenant is not received by Landlord within 5 days after the date suchpayment is due, Tenant shall pay to Landlord an additional sum of 6% of theoverdue Rent as a late charge.  Theparties agree that this late charge represents a fair and reasonable estimateof the costs Landlord will incur by reason of late payment by Tenant.  In addition to the late charge, Rent not paidwhen due shall bear interest at the Default Rate from the 5th day after thedate due until paid.

(c)           **Remedies.**  Upon the occurrence of a Default, Landlord,at its option, without further notice or demand to Tenant, shall have inaddition to all other rights and remedies provided in this Lease, at law or inequity, the option to pursue any one or more of the following remedies, eachand all of which shall be cumulative and nonexclusive, without any notice ordemand whatsoever.  No cure in whole orin part of such Default by Tenant after Landlord has taken any action beyondgiving Tenant notice of such Default to pursue any remedy provided for herein(including retaining counsel to file an action or otherwise pursue anyremedies) shall in any way affect Landlord’s right to pursue such remedy or anyother remedy provided Landlord herein or under law or in equity, unlessLandlord, in its sole discretion, elects to waive such Default.

(i)            This Lease and the Term and estatehereby granted are subject to the limitation that whenever a Default shall havehappened and be continuing, Landlord shall have the right, at its election,then or thereafter while any such Default shall continue and notwithstandingthe fact that Landlord may have some other remedy hereunder or at law or inequity, to give Tenant written notice of Landlord’s intention to terminate thisLease on a date specified in such notice, which date shall be not less than 5days after the giving of such notice, and upon the date so specified, thisLease and the estate hereby granted shall expire and terminate with the sameforce and effect as if the date specified in such notice were the date hereinbeforefixed for the expiration of this Lease, and all right of Tenant hereunder shallexpire and terminate, and Tenant shall be liable as hereinafter in this Section21(c) provided.  If any such notice isgiven, Landlord shall have, on such date so specified, the right of re-entryand possession of the Premises and the right to remove all persons and propertytherefrom and to store such property in a warehouse or elsewhere at the riskand expense, and for the account, of Tenant. Should Landlord elect to re-enter as herein provided or should Landlordtake possession pursuant to legal proceedings or pursuant to any noticeprovided for by law, Landlord may from time to time re-let the Premises or anypart thereof for such term or terms and at such rental or rentals and upon suchterms and conditions as Landlord may deem advisable, with the right to makecommercially reasonable alterations in and repairs to the Premises.

(ii)           In the event of any termination ofthis Lease as in this Section 21 provided or as required or permitted by law orin equity, Tenant shall forthwith quit and surrender the Premises to Landlord,and Landlord may, without further notice, enter upon, re-enter, possess andrepossess the same by summary proceedings, ejectment or otherwise, and againhave, repossess and enjoy the same as if this Lease had not been made, and inany such event Tenant and no person claiming through or under Tenant by virtueof any law or an order of any court shall be entitled to possession or toremain in possession of the Premises. Landlord, at its option, notwithstanding any other provision of thisLease, shall be entitled to recover from Tenant, as and for liquidated damages,the sum of:

(A)          all Base Rent, Additional Rent andother amounts payable by Tenant hereunder then due or accrued and unpaid: and

(B)           the amount equal to the aggregate ofall unpaid Base Rent and Additional Rent which would have been payable if thisLease had not been terminated prior to the end of the Term then in effect,discounted to its then present value in

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accordance with acceptedfinancial practice using a rate of 5% per annum, for loss of the bargain; and

(C)           all other damages and expenses(including attorneys’ fees and expenses), if any, which Landlord shall havesustained by reason of the breach of any provision of this Lease; less

(D)          the net proceeds of any re-lettingactually received by Landlord and the amount of damages which Tenant provescould have been avoided had Landlord taken reasonable steps to mitigate itsdamages.

(iii)          Nothing herein contained shall limitor prejudice the right of Landlord, in any bankruptcy or insolvency proceeding,to prove for and obtain as liquidated damages by reason of such termination anamount equal to the maximum allowed by any bankruptcy or insolvencyproceedings, or to prove for and obtain as liquidated damages by reason of suchtermination, an amount equal to the maximum allowed by any statute or rule oflaw, but in each case not more than the amount to which Landlord wouldotherwise be entitled under this Section 21.

(iv)          Nothing in this Section 21 shall bedeemed to affect the right of either party to indemnifications pursuant to thisLease.

(v)           If Landlord terminates this Leaseupon the occurrence of a Default, Tenant will quit and surrender the Premisesto Landlord or its agents, and Landlord may, without further notice, enterupon, re-enter and repossess the Premises by summary proceedings, ejectment orotherwise.  The words “enter”, “re-enter”,and “re-entry” are not restricted to their technical legal meanings.

(vi)          If either party shall be in default inthe observance or performance of any provision of this Lease, and an actionshall be brought for the enforcement thereof, the non-prevailing party shallpay to the prevailing party all fees, costs and other expenses which may becomepayable as a result thereof or in connection therewith, including attorneys’fees and expenses.

(vii)         If Tenant shall default in the keeping,observance or performance of any covenant, agreement, term, provision orcondition herein contained, Landlord, without thereby waiving such default, mayperform the same for the account and at the expense of Tenant (a) immediatelyor at any time thereafter and without notice in the case of emergency or incase such default will result in a violation of any legal or insurancerequirements, or in the imposition of any lien against all or any portion ofthe Premises (but only after Tenant has failed to respond to such lien aspermitted by Section 15 within the time period provided in Section 15), and (b)in any other case if such default continues after any applicable notice andcure period provided in Section 21.  Allreasonable costs and expenses incurred by Landlord in connection with any suchperformance by it for the account of Tenant and also all reasonable costs andexpenses, including attorneys’ fees and disbursements incurred by Landlord inany action or proceeding (including any summary dispossess proceeding) broughtby Landlord to enforce any obligation of Tenant under this Lease and/or rightof Landlord in or to the Premises, shall be paid by Tenant to Landlord within10 days after demand.

(viii)        Independent of the exercise of any otherremedy of Landlord hereunder or under applicable law, Landlord may conduct anenvironmental test of the Premises as generally described in Section 30(d), atTenant’s expense, to the extent provided in Section 30(d).

(ix)           Except as otherwise provided in thisSection 21, no right or remedy herein conferred upon or reserved to Landlord isintended to be exclusive of any other right or remedy, and every right andremedy shall be cumulative and in addition to any other legal or equitable

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right or remedy givenhereunder, or now or hereafter existing. No waiver of any provision of this Lease shall be deemed to have beenmade unless expressly so made in writing. Landlord shall be entitled, to the extent permitted by law, to seekinjunctive relief in case of the violation, or attempted or threatened violation,of any provision of this Lease, or to seek a decree compelling observance orperformance of any provision of this Lease, or to seek any other legal orequitable remedy.

22.           **Assignmentand Subletting**.

(a)           **General Prohibition**.  Without Landlord’s prior written consentsubject to and on the conditions described in this Section 22, Tenantshall not, directly or indirectly, voluntarily or by operation of law, assignthis Lease or sublease the Premises or any part thereof or mortgage, pledge, orhypothecate its leasehold interest or grant any concession or license withinthe Premises, and any attempt to do any of the foregoing shall be void and ofno effect.  If Tenant is a corporation,partnership or limited liability company, the shares or other ownershipinterests thereof which are not actively traded upon a stock exchange or in theover-the-counter market, a transfer or series of transfers whereby 50% or moreof the issued and outstanding shares or other ownership interests of suchcorporation are, or voting control is, transferred (but excepting transfersupon deaths of individual owners) from a person or persons or entity orentities which were owners thereof at time of execution of this Lease topersons or entities who were not owners of shares or other ownership interestsof the corporation, partnership or limited liability company at time ofexecution of this Lease (a “**CorporateTransfer**”), shall be deemed an assignment of this Lease requiringthe consent of Landlord as provided in this Section 22.  Notwithstanding the foregoing, any publicoffering of shares or other ownership interest in Tenant shall not be deemed anassignment.

**Permitted Transfers**.  If Tenant desires to assign, sublease,hypothecate or otherwise transfer this Lease or sublet the Premises other thanpursuant to a Permitted Assignment (as defined below), then at least 15business days, but not more than 45 business days, before the date Tenantdesires the assignment or sublease to be effective (the “**AssignmentDate**”), Tenant shall give Landlord a notice (the “**Assignment Notice**”) containing such information about theproposed assignee or sublessee, including the proposed use of the Premises andany Hazardous Materials proposed to be used, stored handled, treated, generatedin or released or disposed of from the Premises, the Assignment Date, anyrelationship between Tenant and the proposed assignee or sublessee, and allmaterial terms and conditions of the proposed assignment or sublease, includinga copy of any proposed assignment or sublease in draft or final form (providedthat if a draft form is provided, a copy of the proposed assignment or subleasein its final form shall be provided to Landlord at least 5 business days priorto the time Landlord’s written consent is to be given), its final form, andsuch other information as Landlord may deem reasonably necessary or appropriateto its consideration whether to grant its consent.  Landlord may, by giving written notice toTenant within 15 business days after receipt of the Assignment Notice:  (i) grant such consent, (ii) refuse suchconsent, in its sole and absolute discretion, if the proposed assignment,hypothecation or other transfer or subletting concerns more than (together withall other then effective subleases) 50% of the Premises, (iii) refuse suchconsent, in its reasonable discretion, if the proposed subletting concerns(together with all other then effective subleases) 50% or less of the Premises(provided that Landlord shall further have the right to review and approve ordisapprove the proposed form of sublease prior to the effective date of anysuch subletting), or (iv) terminate this Lease with respect to the spacedescribed in the Assignment Notice as of the Assignment Date (an “**Assignment Termination**”). If Landlord delivers notice of its election to exercise an AssignmentTermination, Tenant shall have the right to withdraw such Assignment Notice bywritten notice to Landlord of such election within 5 business days afterLandlord’s notice electing to exercise the Assignment Termination.  If Tenant withdraws such Assignment Notice,this Lease shall continue in full force and effect.  If Tenant does not withdraw such AssignmentNotice, this Lease, and the term and estate herein granted, shall terminate asof the Assignment Date with respect to the space described in such AssignmentNotice.  No failure of Landlord toexercise any such option to terminate this Lease, or to deliver a timely noticein response to the Assignment Notice, shall be deemed to be Landlord’s consentto the proposed assignment, sublease or other transfer.  Tenant shall reimburse Landlord for all of

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Landlord’s reasonableout-of-pocket expenses in connection with its consideration of any AssignmentNotice.

Notwithstanding the foregoing, Landlord’s consent toan assignment of this Lease or a subletting of any portion of the Premises toany entity controlling, controlled by or under common control with Tenant shallnot be required, provided that Landlord shall have the right to approve theform of any such sublease or assignment.

In addition, Tenant shall, upon 30 days prior writtennotice to Landlord but without obtaining Landlord’s prior written consent, havethe right to make a Corporate Transfer not otherwise permitted hereunder orassign this Lease to a corporation or other entity which is a successor-in-interestto Tenant, by way of merger, consolidation or corporate reorganization, or bythe purchase of all or substantially all of the assets or the ownershipinterests of Tenant provided that (i) such merger or consolidation, or suchCorporate Transfer, acquisition or assumption, as the case may be, is for agood business purpose and not principally for the purpose of transferring theLease, and (ii) the net worth (as determined in accordance with generallyaccepted accounting principles (“**GAAP**”)) ofTenant after the Corporate Transfer or the assignee, as the case may be, is notless than the net worth (as determined in accordance with GAAP) of Tenant as ofthe date of Tenant’s most current quarterly or annual financial statements, and(iii) any such assignee shall agree in writing to assume all of the terms,covenants and conditions of this Lease arising after the effective date of theassignment (a “**Permitted Assignment**”).

(b)          **Additional Conditions**.  As a condition to any such assignment or subletting,whether or not Landlord’s consent is required, Landlord may require:

# (i)            that any assignee or subtenantagree, in writing at the time of such assignment or subletting, that ifLandlord gives such party notice that Tenant is in default under this Lease,such party shall thereafter make all payments otherwise due Tenant directly toLandlord, which payments will be received by Landlord without any liabilityexcept to credit such payment against those due under the Lease, and any suchthird party shall agree to attorn to Landlord or its successors and assignsshould this Lease be terminated for any reason; provided, however,in no event shall Landlord or its successors or assigns be obligated to acceptsuch attornment; and

# (ii)           A list of Hazardous Materials,certified by the proposed assignee or sublessee to be true and correct, whichthe proposed assignee or sublessee intends to use, store, handle, treat,generate in or release or dispose of from the Premises, together with copies ofall documents relating to such use, storage, handling, treatment, generation,release or disposal of Hazardous Materials by the proposed assignee orsubtenant in the Premises or on the Project, prior to the proposed assignmentor subletting, including, without limitation: permits; approvals; reports and correspondence; storage and managementplans; plans relating to the installation of any storage tanks to be installedin or under the Project (provided, said installation of tanks shall only bepermitted after Landlord has given its written consent to do so, which consentmay be withheld in Landlord’s sole and absolute discretion); and all closureplans or any other documents required by any and all federal, state and localGovernmental Authorities for any storage tanks installed in, on or under theProject for the closure of any such tanks. Neither Tenant nor any such proposed assignee or subtenant is required,however, to provide Landlord with any portion(s) of the such documents containinginformation of a proprietary nature which, in and of themselves, do not containa reference to any Hazardous Materials or hazardous activities.

(c)          **No Release of Tenant,Sharing of Excess Rents**. Notwithstanding any assignment or subletting, Tenant and any guarantoror surety of Tenant’s obligations under this Lease shall at all times remainfully and primarily responsible and liable for the payment of Rent and forcompliance with all of Tenant’s other obligations under this Lease.  If the Rent due and received from a sublesseeor assignee (or a combination of the rental received under such sublease orassignment plus any bonus or other consideration therefor or incident theretoin any form) exceeds the sum of******the rental payable under thisLease, (excluding however, any Rent payable under this Section) and actual and reasonable brokerage fees,legal costs and any design or construction fees (including build-out costallowances) directly related to and required pursuant to the terms of any suchsublease) (“**Excess Rent**”),then Tenant shall be bound

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and obligated to pay Landlord as Additional Renthereunder 50% of such Excess Rent within 10 days following receipt thereof byTenant.  If Tenant shall sublet thePremises or any part thereof, Tenant hereby immediately and irrevocably assignsto Landlord, as security for Tenant’s obligations under this Lease, all rentfrom any such subletting, and Landlord as assignee and as attorney-in-fact forTenant, or a receiver for Tenant appointed on Landlord’s application, maycollect such rent and apply it toward Tenant’s obligations under this Lease;except that, until the occurrence of a Default, Tenant shall have the right tocollect such rent.

(d)           **No Waiver**.  The consent by Landlord to an assignment orsubletting shall not relieve Tenant or any assignees of this Lease or anysublessees of the Premises from obtaining the consent of Landlord to anyfurther assignment or subletting nor shall it release Tenant or any assignee orsublessee of Tenant from full and primary liability under the Lease.  The acceptance of Rent hereunder, or theacceptance of performance of any other term, covenant, or condition thereof,from any other person or entity shall not be deemed to be a waiver of any ofthe provisions of this Lease or a consent to any subletting, assignment orother transfer of the Premises.

(e)           **PriorConduct of Proposed Transferee. **Notwithstandingany other provision of this Section 22, if (i) the proposed assignee orsublessee of Tenant has been required by any prior landlord, lender orGovernmental Authority to take remedial action in connection with HazardousMaterials contaminating a property, where the contamination resulted from suchparty’s action or use of the property in question, (ii) the proposed assigneeor sublessee is subject to an enforcement order issued by any GovernmentalAuthority in connection with the use, storage, handling, treatment, generation,release or disposal of Hazardous Materials (including, without limitation, anyorder related to the failure to make a required reporting to any GovernmentalAuthority), or (iii) because of the existence of a pre-existing environmentalcondition in the vicinity of or underlying the Project, the risk that Landlordwould be targeted as a responsible party in connection with the remediation ofsuch pre-existing environmental condition would be materially increased orexacerbated by the proposed use of Hazardous Materials by such proposedassignee or sublessee, Landlord shall have the absolute right to refuse toconsent to any assignment or subletting to any such party.

23.           **Estoppel Certificate.**  Tenant shall, within 10 business days ofwritten notice from Landlord, execute, acknowledge and deliver a statement inwriting in any form reasonably requested by a proposed lender or purchaser, (i)certifying that this Lease is unmodified and in full force and effect (or, ifmodified, stating the nature of such modification and certifying that thisLease as so modified is in full force and effect) and the dates to which therental and other charges are paid in advance, if any, (ii) acknowledging thatthere are not, to Tenant’s knowledge, any uncured defaults on the part ofLandlord hereunder, or specifying such defaults if any are claimed, and (iii)setting forth to the best of Tenant’s knowledge such further information withrespect to the status of this Lease or the Premises as may be requestedthereon.  Any such statement may berelied upon by any prospective purchaser or encumbrancer of all or any portionof the real property of which the Premises are a part.  Tenant’s failure to deliver such statementwithin such time shall, at the option of Landlord, be conclusive upon Tenantthat the Lease is in full force and effect and without modification except asmay be represented by Landlord in any certificate prepared by Landlord anddelivered to Tenant for execution.  Uponrequest by Tenant, Landlord will similarly execute an estoppel certificate: (i)certifying that this Lease is unmodified and in full force and effect (or, if modified,stating the nature of such modification and certifying that this Lease as somodified is in full force and effect) and the dates to which the rental andother charges are paid in advance, if any, (ii) acknowledging that there arenot, to Landlord’s knowledge, any uncured defaults on the part of Tenanthereunder, or specifying such defaults if any are claimed and (iii) settingforth to the best of Landlord’s knowledge such further information with respectto the status of this Lease or the Premises as may be reasonably requestedthereon.

24.           **Quiet Enjoyment**.  So long as Tenant shall perform all of thecovenants and agreements herein required to be performed by Tenant, Tenantshall, subject to the terms of this Lease, at all times during the Term, havepeaceful and quiet enjoyment of the Premises against any person claiming by,through or under Landlord.

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25.           **Prorations.**  All prorations required or permitted to bemade hereunder shall be made on the basis of a 360 day year and 30 day months.

26.           **Rules and Regulations**.  Tenant shall, at all times during the Termand any extension thereof, comply with all reasonable rules and regulations atany time or from time to time established by Landlord covering use of thePremises and the Project.  The current rulesand regulations are attached hereto as **Exhibit E**.  If there is any conflict between said rulesand regulations and other provisions of this Lease, the terms and provisions ofthis Lease shall control.  Landlord shallnot have any liability or obligation for the breach of any rules or regulationsby other tenants in the Project and shall not enforce such rules andregulations in a discriminatory manner.

27.           **Subordination**.  This Lease and Tenant’s interest and rightshereunder are hereby made and shall be subject and subordinate at all times tothe lien of any Mortgage now existing or hereafter created on or against theProject or the Premises, and all amendments, restatements, renewals,modifications, consolidations, refinancing, assignments and extensions thereof,without the necessity of any further instrument or act on the part of Tenant; provided,however that so long as there is no Default hereunder, Tenant’s right topossession of the Premises shall not be disturbed by the Holder of any suchMortgage created after the date hereof (a “**FutureMortgage**”) and Tenant’s rights hereunder shall be recognized by anyHolder of a Future Mortgage, subject to and in accordance with the terms ofsuch Holder’s standard form of subordination and non-disturbanceagreement.  Tenant agrees, at theelection of the Holder of any such Mortgage, to attorn to any such Holder.  Tenant agrees upon demand to execute,acknowledge and deliver such instruments, confirming such subordination, andsuch instruments of attornment as shall be requested by any such Holder, providedany such instruments contain appropriate non-disturbance provisions assuringTenant’s quiet enjoyment of the Premises as set forth in Section 24hereof.  Notwithstanding the foregoing,any such Holder may at any time subordinate its Mortgage to this Lease, withoutTenant’s consent, by notice in writing to Tenant, and thereupon this Leaseshall be deemed prior to such Mortgage without regard to their respective datesof execution, delivery or recording and in that event such Holder shall havethe same rights with respect to this Lease as though this Lease had beenexecuted prior to the execution, delivery and recording of such Mortgage andhad been assigned to such Holder.  Withrespect to any Holder of a Mortgage in existence as of the date hereof, Landlordagrees to use commercially reasonable efforts in seeking the agreement of suchHolder to execute a subordination, non-disturbance and attornment agreementwith Tenant, satisfactory in form and substance to both Tenant and such Holder.  The term “**Mortgage**”whenever used in this Lease shall be deemed to include deeds of trust, securityassignments, ground leases or other superior leases and any other encumbrances,and any reference to the “**Holder**” of aMortgage shall be deemed to include the beneficiary under a deed of trust.

28.           **Surrender**.  Upon the expiration of the Term or earliertermination of Tenant’s right of possession, Tenant shall surrender thePremises to Landlord in the same condition as received, subject to anyAlterations or Installations permitted by Landlord to remain in the Premises,free of Hazardous Materials brought upon, kept, used, stored, handled, treated,generated in, or released or disposed of from, the Premises by any person otherthan a Landlord Party (collectively, “**Tenant HazMat Operations**”)and released of all Hazardous Materials Clearances, broom clean, ordinary wearand tear and casualty loss and condemnation covered by Sections 18and 19 and repairs for which Landlord is responsible or damage directlyresulting solely from default by Landlord under this Lease, excepted.  At least 3 months prior to the surrender ofthe Premises, Tenant shall deliver to Landlord a narrative description of theactions proposed (or required by any Governmental Authority) to be taken byTenant in order to surrender the Premises (including any Installationspermitted by Landlord to remain in the Premises) at the expiration or earliertermination of the Term, free from any residual impact from the Tenant HazMatOperations and otherwise released for unrestricted use and occupancy (the “**Surrender Plan**”). Such Surrender Plan shall be accompanied by a current listing of (i) allHazardous Materials licenses and permits held by or on behalf of any TenantParty with respect to the Premises, and (ii) all Hazardous Materials used,stored, handled, treated, generated, released or disposed of from the Premises,and shall be subject to the review and approval of Landlord’s environmentalconsultant, such approval not to be unreasonably withheld or delayed.  In connection with the review and approval ofthe Surrender Plan, upon the request of Landlord, Tenant shall deliver toLandlord or its consultant such

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additional non-proprietary information concerningTenant HazMat Operations as Landlord shall request.  If Tenant has not received a written responsefrom Landlord on the Surrender Plan within 20 days after Tenant has deliveredthe Surrender Plan, accompanied by such other material and information as maybe required in this Section 28, Tenant shall notify Landlord in themanner set forth in Section 41(a) of such lack of response (the “**Response Notice**”).  A Response Notice shall be null and voidunless the first page thereof includes the following in bold-faced, all capitalletters type with at least a 12 pitch font: **THIS IS A LEGAL NOTICE AND THE FAILURETO RESPOND WITHIN TEN (10) BUSINESS DAYS SHALL CAUSE THE FORFEITURE OF CERTAINRIGHTS UNDER SECTION 28 OF YOUR LEASE WITH SIRTRIS PHARMACEUTICALS, INC.WITH RESPECT TO PREMISES AT 200 TECHNOLOGY SQUARE, CAMBRIDGE, MASSACHUSETTS.**  If 10 business days have elapsed followingthe date that Landlord has received the Response Notice to Landlord andLandlord has not provided a written response to the Surrender Plan, theSurrender Plan shall be deemed to be approved by Landlord.  On or before such surrender, Tenant shalldeliver to Landlord evidence that the approved Surrender Plan shall have beensatisfactorily completed and Landlord shall have the right, subject toreimbursement at Tenant’s expense as set forth below, to cause Landlord’senvironmental consultant to inspect the Premises and perform such additionalprocedures as may be deemed reasonably necessary to confirm that the Premisesare, as of the effective date of such surrender or early termination of theLease, free from any residual impact from Tenant HazMat Operations.  Tenant shall reimburse Landlord, asAdditional Rent, for the actual out-of pocket expense incurred by Landlord forLandlord’s environmental consultant to review and approve the Surrender Plan andto visit the Premises and verify satisfactory completion of the same, whichcost shall not exceed $5,000.  Landlordshall have the unrestricted right to deliver such Surrender Plan and any reportby Landlord’s environmental consultant with respect to the surrender of thePremises to third parties.

If Tenant shall fail to prepare or submit a SurrenderPlan approved by Landlord, or if Tenant shall fail to complete the approvedSurrender Plan, or if such Surrender Plan, whether or not approved by Landlord,shall fail to adequately address any residual effect of Tenant HazMatOperations in, on or about the Premises, Landlord shall have the right to takesuch actions as Landlord may deem reasonable or appropriate to assure that thePremises and the Project are surrendered free from any residual impact fromTenant HazMat Operations, the cost of which actions shall be reimbursed byTenant as Additional Rent, without regard to the limitation set forth in thefirst paragraph of this Section 28.

Tenant shall immediately return to Landlord all keysand/or access cards to parking, the Project, restrooms or all or any portion ofthe Premises furnished to or otherwise procured by Tenant.  If any such access card or key is lost, Tenantshall pay to Landlord, at Landlord’s election, either the cost of replacingsuch lost access card or key or the cost of reprogramming the access securitysystem in which such access card was used or changing the lock or locks openedby such lost key.  Any Tenant’s Property,Alterations and property not so removed by Tenant as permitted or requiredherein shall be deemed abandoned and may be stored, removed, and disposed of byLandlord at Tenant’s expense, and Tenant waives all claims against Landlord forany damages resulting from Landlord’s retention and/or disposition of suchproperty.  All obligations of Tenanthereunder not fully performed as of the termination of the Term, including theobligations of Tenant under Section 30 hereof, shall survive theexpiration or earlier termination of the Term, including, without limitation,indemnity obligations, payment obligations with respect to Rent and obligationsconcerning the condition and repair of the Premises.

29.           **Waiver of Jury Trial**.  TENANT AND LANDLORD WAIVE ANY RIGHT TO TRIALBY JURY OR TO HAVE A JURY PARTICIPATE IN RESOLVING ANY DISPUTE, WHETHERSOUNDING IN CONTRACT, TORT, OR OTHERWISE, BETWEEN LANDLORD AND TENANT ARISINGOUT OF THIS LEASE OR ANY OTHER INSTRUMENT, DOCUMENT, OR AGREEMENT EXECUTED ORDELIVERED IN CONNECTION HEREWITH OR THE TRANSACTIONS RELATED HERETO.

30.           **EnvironmentalRequirements**.

(a)           **Prohibition/Compliance/Indemnity**.  Tenant shall not cause or permit anyHazardous Materials (as hereinafter defined) to be brought upon, kept, used,stored, handled, treated, generated  inor about, or released or disposed of from, the Premises or the Project inviolation of applicable

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Environmental Requirements (as hereinafter defined) byTenant or any Tenant Party, it being acknowledged that the foregoing shall notapply to Hazardous Materials that Tenant conclusively proves to have been inplace in the Premises (through no act or omission of Tenant, its agents orinvitees) prior to the Commencement Date, Tenant having the burden of proof inconnection therewith and being obligated hereunder until the same has been soproved or acknowledged by Landlord.  IfTenant breaches the obligation stated in the preceding sentence, or if thepresence of Hazardous Materials in the Premises during the Term or any holdingover results in contamination of the Premises, the Project or any adjacentproperty or if contamination of the Premises, the Project or any adjacentproperty by Hazardous Materials brought into, kept, used, stored, handled,treated, generated in or about, or released or disposed of from, the Premisesby anyone other than Landlord and Landlord’s employees, agents and contractorsotherwise occurs during the Term or any holding over, Tenant hereby indemnifiesand shall defend and hold Landlord, its officers, directors, employees, agentsand contractors harmless from any and all actions (including, withoutlimitation, remedial or enforcement actions of any kind, administrative orjudicial proceedings, and orders or judgments arising out of or resultingtherefrom), costs, claims, damages (including, without limitation, punitivedamages and damages based upon diminution in value of the Premises or theProject, or the loss of, or restriction on, use of the Premises or any portionof the Project), expenses (including, without limitation, reasonable attorneys’,consultants’ and experts’ fees, court costs and amounts paid in settlement ofany claims or actions), fines, forfeitures or other civil, administrative orcriminal penalties, injunctive or other relief (whether or not based uponpersonal injury, property damage, or contamination of, or adverse effects upon,the environment, water tables or natural resources), liabilities or losses(collectively, “**Environmental Claims**”) which ariseduring or after the Term as a result of such contamination.  Except as and to the extent otherwiseexpressly set forth above, this indemnification of Landlord by Tenant includes,without limitation, costs incurred in connection with any investigation of siteconditions or any cleanup, treatment, remedial, removal, or restoration workrequired by any federal, state or local Governmental Authority because ofHazardous Materials present in the air, soil or ground water above, on, orunder the Premises.  Without limiting theforegoing, if the presence of any Hazardous Materials on the Premises, theBuilding, the Project or any adjacent property caused or permitted by Tenant orany Tenant Party results in any contamination of the Premises,****the Building, the Project or any adjacent property, Tenantshall promptly take all actions at its sole expense and in accordance withapplicable Environmental Requirements as are necessary to return the Premises,****the Building, the Project or any adjacent property to thecondition existing prior to the time of such contamination, provided that Landlord’sapproval of such action shall first be obtained, which approval shall notunreasonably be withheld so long as such actions would not potentially have anymaterial adverse long-term or short-term effect on the Premises****, the Building or the Project.

(b)           **Business.**  Landlord acknowledges that it is not theintent of this Section 30 to prohibit Tenant from using the Premises forthe Permitted Use.  Tenant may operateits business according to prudent industry practices so long as the use orpresence of Hazardous Materials is strictly and properly monitored according toall then applicable Environmental Requirements. As a material inducement to Landlord to allow Tenant to use HazardousMaterials in connection with its business, Tenant agrees to deliver to Landlordprior to the Commencement Date a list identifying each type of HazardousMaterials to be brought upon, kept, used, stored, handled, treated, generatedon, or released or disposed of from, the Premises and setting forth any and allgovernmental approvals or permits required in connection with the presence,use, storage, handling, treatment, generation, release or disposal of suchHazardous Materials on or from the Premises (“**HazardousMaterials List**”).  Tenantshall deliver to Landlord an updated Hazardous Materials List at least once ayear and shall also deliver an updated list before any new Hazardous Materialis brought onto, kept, used, stored, handled, treated, generated on, orreleased or disposed of from, the Premises. Tenant shall deliver to Landlord true and correct copies of thefollowing documents (the “**Haz Mat Documents**”)relating to the use, storage, handling, treatment, generation, release ordisposal of Hazardous Materials prior to the Commencement Date, or ifunavailable at that time, concurrent with the receipt from or submission to aGovernmental Authority:  permits;approvals; reports and correspondence; storage and management plans, notice ofviolations of any Legal Requirements; plans relating to the installation of anystorage tanks to be installed in or under the Project (provided, saidinstallation of tanks shall only be permitted after Landlord has given Tenantits written consent to do so, which consent may be withheld in Landlord’s soleand absolute discretion); all closure plans or any other documents required byany and all federal, state and local Governmental Authorities

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for any storage tanks installed in, on or under theProject for the closure of any such tanks; and a Surrender Plan (to the extentsurrender in accordance with Section 28 cannot be accomplished in 3months).  Tenant is not required,however, to provide Landlord with any portion(s) of the Haz Mat Documentscontaining information of a proprietary nature which, in and of themselves, do notcontain a reference to any Hazardous Materials or hazardous activities.  It is not the intent of this Section toprovide Landlord with information which could be detrimental to Tenant’sbusiness should such information become possessed by Tenant’s competitors.

(c)           **Tenant Representation andWarranty**.  Tenant herebyrepresents and warrants to Landlord that (i) neither Tenant nor any of itslegal predecessors has been required by any prior landlord, lender orGovernmental Authority at any time to take remedial action in connection withHazardous Materials contaminating a property which contamination was permittedby Tenant of such predecessor or resulted from Tenant’s or such predecessor’saction or use of the property in question, and (ii) Tenant is not subject toany enforcement order issued by any Governmental Authority in connection withthe use, storage, handling, treatment, generation, release or disposal ofHazardous Materials (including, without limitation, any order related to thefailure to make a required reporting to any Governmental Authority).  If Landlord reasonably determines that thisrepresentation and warranty was not true as of the date of this lease, Landlordshall have the right to terminate this Lease in Landlord’s sole and absolutediscretion.

(d)           **Testing. **Landlord shall have the right toconduct annual tests of the Premises to determine whether any contamination ofthe Premises or the Project has occurred as a result of Tenant’s use.  Tenant shall be required to pay thereasonable cost of such annual test of the Premises; provided, however, that ifTenant conducts its own tests of the Premises using third party contractors andtest procedures acceptable to Landlord which tests are certified to Landlord,Landlord shall accept such tests in lieu of the annual tests to be paid for byTenant.  In addition, at any time, andfrom time to time, prior to the expiration or earlier termination of the Term,if required by a lender, potential lender, purchaser, potential purchaser,investor, potential investor or Governmental Authority or if Landlord hasreason to believe that contamination may have occurred, Landlord shall have theright, upon 7 days notice or such shorter period required by any other suchparty, to conduct appropriate tests of the Premises and the Project todetermine if contamination has occurred as a result of Tenant’s use of thePremises.  In connection with suchtesting, upon the request of Landlord, Tenant shall deliver to Landlord or itsconsultant such non-proprietary information concerning the use of HazardousMaterials in or about the Premises by Tenant or any Tenant Party.  Any consultant of Landlord that Landlordpermits to access the Premises shall have reasonably adequate types and amountsof insurance and shall not unreasonably interfere with Tenant’s use andoccupancy of the Premises.  Ifcontamination has occurred for which Tenant is liable under this Section 30,Tenant shall pay all costs to conduct such tests.  If no such contamination is found, Landlordshall pay the costs of such tests (which shall not constitute an OperatingExpense).  Landlord shall provide Tenantwith a copy of all third party, non-confidential reports and tests of thePremises made by or on behalf of Landlord during the Term withoutrepresentation or warranty and subject to a confidentiality agreement.  Tenant shall, at its sole cost and expense,promptly and satisfactorily remediate any environmental conditions identifiedby such testing in accordance with all Environmental Requirements.  Landlord’s receipt of or satisfaction withany environmental assessment in no way waives any rights which Landlord mayhave against Tenant.

(e)           **Underground Tanks**.  If underground or other storage tanks storingHazardous Materials located on the Premises or the Project are used by Tenantor are hereafter placed on the Premises or the Project by Tenant, Tenant shallinstall, use, monitor, operate, maintain, upgrade and manage such storagetanks, maintain appropriate records, obtain and maintain appropriate insurance,implement reporting procedures, properly close any underground storage tanks,and take or cause to be taken all other actions necessary or required underapplicable state and federal Legal Requirements, as such now exists or mayhereafter be adopted or amended in connection with the installation, use,maintenance, management, operation, upgrading and closure of such storagetanks.

(f)            **Tenant’s Obligations**.  Tenant’s obligations under this Section 30shall survive the expiration or earlier termination of the Lease.  During any period of time after theexpiration or earlier termination of this Lease required by Tenant or Landlordto complete the removal from the Premises of

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any Hazardous Materials for which Tenant isresponsible under this Section 30 (including, without limitation, therelease and termination of any licenses or permits restricting the use of thePremises and the completion of the approved Surrender Plan), Tenant shallcontinue to pay the full Rent in accordance with this Lease for any portion ofthe Premises not relet by Landlord in Landlord’s sole discretion, which Rentshall be prorated daily.

(g)           **Reports**.  Whenever Landlord requests reports, documentsor other materials from Tenant relating to Hazardous Materials under this Leaseand such reports, documents or materials contain Tenant’s trade secrets orproprietary information, Tenant may request Landlord to sign a mutually,reasonably acceptable form of confidentiality agreement and failing Landlord’sexecution of the same, Tenant may redact any trade secrets or proprietaryinformation from such reports, documents or other materials.

(h)           **Definitions.** As used herein, the term “**EnvironmentalRequirements**” means all applicable present and future statutes,regulations, ordinances, rules, codes, judgments, orders or other similarenactments of any Governmental Authority regulating or relating to health,safety, or environmental conditions on, under, or about the Premises or theProject, or the environment, including without limitation, the following:  the Comprehensive Environmental Response,Compensation and Liability Act; the Resource Conservation and Recovery Act; andall state and local counterparts thereto, and any regulations or policiespromulgated or issued thereunder.  Asused herein, the term “**Hazardous Materials**”means and includes any substance, material, waste, pollutant, or contaminantlisted or defined as hazardous or toxic, or regulated by reason of its impactor potential impact on humans, animals and/or the environment under anyEnvironmental Requirements, asbestos and petroleum, including crude oil or anyfraction thereof, natural gas liquids, liquefied natural gas, or synthetic gasusable for fuel (or mixtures of natural gas and such synthetic gas).  As defined in Environmental Requirements, Tenantis and shall be deemed to be the “**operator**” ofTenant’s “**facility**” and the “**owner**”of all Hazardous Materials brought on the Premises by Tenant or any TenantParty, and the wastes, by-products, or residues generated, resulting, orproduced therefrom.

31.           **Tenant’sRemedies/Limitation of Liability**. Landlord shall not be in default hereunder unless Landlord fails toperform any of its obligations hereunder within 30 days after written noticefrom Tenant specifying such failure (unless such performance will, due to thenature of the obligation, require a period of time in excess of 30 days, thenafter such period of time as is reasonably necessary).  Upon any default by Landlord, Tenant shallgive notice by registered or certified mail to any Holder of a Mortgagecovering the Premises and to any landlord of any lease of property in or onwhich the Premises are located and Tenant shall offer such Holder and/orlandlord a reasonable opportunity to cure the default, including time to obtainpossession of the Project by power of sale or a judicial action if such shouldprove necessary to effect a cure; provided Landlord shall have furnishedto Tenant in writing the names and addresses of all such persons who are toreceive such notices.  All obligations ofLandlord hereunder shall be construed as covenants, not conditions; and, exceptas may be otherwise expressly provided in this Lease, Tenant may not terminatethis Lease for breach of Landlord’s obligations hereunder.

All obligations of Landlord under this Lease will bebinding upon Landlord only during the period of its ownership of the Premisesand not thereafter.  The term “**Landlord**” in this Lease shall mean only the owner for thetime being of the Premises.  Upon thetransfer by such owner of its interest in the Premises, such owner shallthereupon be released and discharged from all obligations of Landlordthereafter accruing, but such obligations shall be binding during the Term uponeach new owner for the duration of such owner’s ownership.

32.           **Inspection and Access**.  Landlord and its agents, representatives, andcontractors may enter the Premises at any reasonable time after notice toTenant (except in the event of an emergency when no notice shall be required)to inspect the Premises and to make such repairs as may be required orpermitted pursuant to this Lease and for any other business purpose.  Landlord and Landlord’s representatives mayenter the Premises during business hours on not less than 48 hours advancewritten notice (except in the case of emergencies in which case no such noticeshall be required and such entry may be at any time) for the purpose ofeffecting any such repairs, inspecting the Premises, showing the

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Premises to prospective purchasers and, during thelast year of the Term, to prospective tenants or for any other businesspurpose.  Landlord may erect a suitablesign on the Premises stating the Premises are available to let or that theProject is available for sale.  Landlordmay grant easements, make public dedications, designate Common Areas and createrestrictions on or about the Premises, provided that no such easement,dedication, designation or restriction materially, adversely affects Tenant’suse or occupancy of the Premises for the Permitted Use.  At Landlord’s request, Tenant shall executesuch instruments as may be necessary for such easements, dedications orrestrictions.  Tenant shall at all times,except in the case of emergencies, have the right to escort Landlord or itsagents, representatives, contractors or guests while the same are in thePremises, provided such escort does not materially and adversely affectLandlord’s access rights hereunder. Landlord shall use commercially reasonable efforts not to materiallyinterfere with the conduct of Tenant’s ordinary business operations in thePremises during any access of the Premises by Landlord.

33.           **Security**.  Tenant acknowledges and agrees that securitydevices and services, if any, while intended to deter crime may not in giveninstances prevent theft or other criminal acts and that Landlord is notproviding any security services with respect to the Premises.  Tenant agrees that Landlord shall not beliable to Tenant for, and Tenant waives any claim against Landlord with respectto, any loss by theft or any other damage suffered or incurred by Tenant inconnection with any unauthorized entry into the Premises or any other breach ofsecurity with respect to the Premises. Tenant shall be solely responsible for the personal safety of Tenant’sofficers, employees, agents, contractors, guests and invitees while any suchperson is in, on or about the Premises and/or the Project.  Tenant shall at Tenant’s cost obtaininsurance coverage to the extent Tenant desires protection against suchcriminal acts.

34.           **Force Majeure**.  Neither Landlord nor Tenant shall beresponsible or liable for delays in the performance of its obligationshereunder when caused by, related to, or arising out of acts of God, strikes,lockouts, or other labor disputes, embargoes, quarantines, weather, national,regional, or local disasters, calamities, or catastrophes, inability to obtainlabor or materials (or reasonable substitutes therefor) at reasonable costs orfailure of, or inability to obtain, utilities necessary for performance,governmental restrictions, orders, limitations, regulations, or controls,national emergencies, delay in issuance or revocation of permits, enemy orhostile governmental action, terrorism, insurrection, riots, civil disturbanceor commotion, fire or other casualty, and other causes or events beyond thereasonable control of Landlord (“**Force Majeure**”).  Notwithstanding the foregoing, financialdifficulty of Landlord or Tenant shall not be deemed to be Force Majeure andForce Majeure shall not apply to any obligation to pay money hereunder.

35.           **Brokers, Entire Agreement,Amendment**.  Landlord andTenant each represents and warrants that it has not dealt with any broker,agent or other person (collectively, “**Broker)**inconnection with this transaction and that no Broker brought about thistransaction, other than Richards Barry Joyce & Partners and Cushman & Wakefield.  Landlord and Tenant each hereby agreeto indemnify and hold the other harmless from and against any claims by anyBroker, other than the broker, if any named in this Section 35,claiming a commission or other form of compensation by virtue of having dealtwith Tenant or Landlord, as applicable, with regard to this leasingtransaction.  T**his Lease constitutes the entire agreementbetween Landlord and Tenant pertaining to the lease of the Premises andsupersedes all other agreements, whether oral or written, pertaining to thelease of the Premises, and no other agreements with respect thereto shallbe effective.  Any amendments or modifications of this Lease shall be inwriting and signed by both Landlord and Tenant, and any other attemptedamendment or modification of this Lease shall be void.**

36.           **Limitation on Landlord’sLiability.**  NOTWITHSTANDINGANYTHING SET FORTH HEREIN OR IN ANY OTHER AGREEMENT BETWEEN LANDLORD AND TENANTTO THE CONTRARY:  (A) LANDLORD SHALL NOTBE LIABLE TO TENANT OR ANY OTHER PERSON FOR (AND TENANT AND EACH SUCH OTHERPERSON ASSUME ALL RISK OF) LOSS, DAMAGE OR INJURY, WHETHER ACTUAL ORCONSEQUENTIAL TO:  TENANT’S PERSONALPROPERTY OF EVERY KIND AND DESCRIPTION, INCLUDING, WITHOUT LIMITATION TRADEFIXTURES, EQUIPMENT, INVENTORY, SCIENTIFIC RESEARCH, SCIENTIFIC EXPERIMENTS,LABORATORY

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ANIMALS, PRODUCT, SPECIMENS, SAMPLES, AND/ORSCIENTIFIC, BUSINESS, ACCOUNTING AND OTHER RECORDS OF EVERY KIND AND DESCRIPTIONKEPT AT THE PREMISES AND ANY AND ALL INCOME DERIVED OR DERIVABLE THEREFROM; (B)THERE SHALL BE NO PERSONAL RECOURSE TO LANDLORD FOR ANY ACT OR OCCURRENCE IN,ON OR ABOUT THE PREMISES OR ARISING IN ANY WAY UNDER THIS LEASE OR ANY OTHERAGREEMENT BETWEEN LANDLORD AND TENANT WITH RESPECT TO THE SUBJECT MATTER HEREOFAND ANY LIABILITY OF LANDLORD HEREUNDER SHALL BE STRICTLY LIMITED SOLELY TOLANDLORD’S INTEREST IN THE PROJECT OR ANY PROCEEDS FROM SALE OR CONDEMNATIONTHEREOF AND ANY INSURANCE PROCEEDS PAYABLE IN RESPECT OF LANDLORD’S INTEREST INTHE PROJECT OR IN CONNECTION WITH ANY SUCH LOSS; AND (C) IN NO EVENT SHALL ANYPERSONAL LIABILITY BE ASSERTED AGAINST ANY OF LANDLORD’S OFFICERS, DIRECTORS,EMPLOYEES, AGENTS OR CONTRACTORS.  UNDERNO CIRCUMSTANCES SHALL LANDLORD OR ANY OF LANDLORD’S OFFICERS, DIRECTORS,EMPLOYEES, AGENTS OR CONTRACTORS BE LIABLE FOR INJURY TO TENANT’S BUSINESS ORFOR ANY LOSS OF INCOME OR PROFIT THEREFROM.

37.           **Severability.**  If any clause or provision of this Lease isillegal, invalid or unenforceable under present or future laws, then and inthat event, it is the intention of the parties hereto that the remainder ofthis Lease shall not be affected thereby. It is also the intention of the parties to this Lease that in lieu ofeach clause or provision of this Lease that is illegal, invalid orunenforceable, there be added, as a part of this Lease, a clause or provisionas similar in effect to such illegal, invalid or unenforceable clause orprovision as shall be legal, valid and enforceable.

38.           **Signs; Exterior Appearance**.  Tenant shall not, without the prior writtenconsent of Landlord, which may be granted or withheld in Landlord’s solediscretion:  (i) attach any awnings,exterior lights, decorations, balloons, flags, pennants, banners, painting orother projection to any outside wall of the Project, (ii) use any curtains,blinds, shades or screens other than Landlord’s standard window coverings,(iii) coat or otherwise sunscreen the interior or exterior of any windows, (iv)place any bottles, parcels, or other articles on the window sills, (v) placeany equipment, furniture or other items of personal property on any exteriorbalcony, or (vi) paint, affix or exhibit on any part of the Premises or theProject any signs, notices, window or door lettering, placards, decorations, oradvertising media of any type which can be viewed from the exterior of thePremises.  Interior signs on doors andthe directory tablet shall be inscribed, painted or affixed for Tenant byLandlord at the sole cost and expense of Landlord, and shall be of a size,color and type acceptable to Landlord. Nothing may be placed on the exterior of corridor walls or corridordoors other than Landlord’s standard lettering. The directory tablet shall be provided exclusively for the display ofthe name and location of tenants. Provided each of the followingconditions is met and remains satisfied: (a) Tenant is in occupancy of at leastfour (4) entire floors of the Building under the Lease, and (b) Tenant is notin default of any of its obligations under the Lease beyond any applicablenotice and cure periods (the “**SignageConditions**”), then Tenant shall have the right to exterior signageat the Building in the form of 1 exterior Building sign at a single elevation (“**Tenant’s Exterior Sign**”).  The design, size, color, illumination (ifany), and location of Tenant’s Exterior Sign shall be subject to Landlord’sprior written approval, and shall comply with all applicable laws, and Tenant’sExterior Sign shall be installed by Landlord at Tenant’s sole cost andexpense.  Tenant shall, at its sole costand expense, obtain all permits and governmental approvals necessary for theinstallation of Tenant’s Exterior Sign, and shall provide a copies of all suchpermits and evidence of such governmental approvals to Landlord prior to thecommencement of any work related to the installation of such sign.  The contractor(s) hired to install Tenant’sExterior Sign shall be selected by Landlord, and Tenant shall be responsiblefor repairing any and all property damage relating to the installation orremoval of Tenant’s Exterior Sign.  If atany time during the Term of this Lease either or both of the Signage Conditionsis not satisfied, Landlord shall have the right to remove Tenant’s ExteriorSign at Tenant’s sole cost and expense.

39.           **Rightto Expand**.

(a)           **Expansion in the Building**.  Tenant shall have the right, but not theobligation, to expand the Premises (the “**Expansion Right**”)to include any Available Space located on the Fourth Floor

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of the Building upon the terms and conditions in thisSection.  For purposes of this Section39(a), “**Available Space**” shall mean anyspace located on the Fourth Floor of the Building which is not occupied by atenant or which is occupied by an existing tenant whose lease is expiringwithin 6 months or less and such tenant does not wish to renew (whether or notsuch tenant has a right to renew) its occupancy of such space.

(b)           **ExpansionPrior to Commencement Date**. From the date hereof until the Commencement Date, Tenant shall have theright, exercisable upon 30 days’ prior written notice to Landlord, to expandthe Premises to include all, but not less than all, of the Available Space uponall the same terms as conditions as are set forth in the Lease, except asotherwise set forth in this Section 39(b).  In the event Tenant elects to so expand thePremises to include the Available Space, (i) the Rent Commencement Date withrespect to the Available Space shall be the date that is 8 months after thedate on which Tenant exercises its Expansion Right, (ii) in lieu of the TIAllowance set forth in the Work Letter attached to this Lease, Tenant shallreceive a tenant improvement allowance for the improvement of the AvailableSpace in an amount equal to the product of (X) $180.00 per rentable square footof the Available Space and (Y) a fraction, the numerator of which is the numberof months remaining in the Base Term following the Rent Commencement Date forthe Available Space, and the denominator of which is 120, (iii) all initialimprovements to the Available Space shall be performed in accordance with theterms of the Work Letter attached to this Lease, provided however, that theamount of the TI Allowance shall be determined in accordance with subsection (ii)of this Section 39(b) and provided further that Sections 2(a), 2(b),2(c) and 3(a) of the Work Letter shall be deleted and replaced with Sections 2(a),2(b), 2(c) and 3(a) set forth on Exhibit G hereto, and (iv) Landlord andTenant shall promptly thereafter execute a mutually acceptable form ofamendment to the Lease memorializing the incorporation of the Available Spaceinto the Premises.  If:  (A) Tenant fails to timely deliver notice ofits election to expand the Premises to include all of the Available Space uponall the same terms as conditions as are set forth in the Lease, or (B) afterthe expiration of a period of 30 days from the date Tenant gives such notice,no lease amendment or lease agreement for the Available Space has beenexecuted, and Landlord tenders to Tenant an amendment to this Lease settingforth the terms for the rental of the Available Space consistent with this Section39(b) and otherwise consistent with the terms of this Lease, and Tenantfails to execute such Lease amendment within 10 business days following suchtender, Tenant shall be deemed to have waived its right to lease such AvailableSpace on the same terms and conditions as are set forth in the Lease (subjectto Tenant’s expansion right set forth in Section 39(c) below).

(c)             **ExpansionFollowing Commencement Date**. From and after the Commencement Date, if there is any Available Space,then prior to offering any Available Space to a third party, Landlord shall, atsuch time as Landlord shall elect so long as Tenant’s rights hereunder arepreserved, deliver to Tenant written notice (the “**ExpansionNotice**”) of such Available Space, together with the terms andconditions on which Landlord is prepared to lease Tenant such AvailableSpace.  Tenant shall have 10 businessdays following delivery of the Expansion Notice to deliver to Landlord writtennotification of Tenant’s exercise of the Expansion Right, in which event Tenant shall be entitled to lease such AvailableSpace upon the terms and conditions set forth in the Expansion Notice.  If: (i) Tenant fails to timely deliver notice accepting the terms of anExpansion Notice, or (ii) after the expiration of a period of 30 days from thedate Tenant gives notice accepting Landlord’s offer to lease such AvailableSpace, no lease amendment or lease agreement for the Available Space has beenexecuted, and Landlord tenders to Tenant an amendment to this Lease settingforth the terms for the rental of the Available Space consistent with those setforth in the Expansion Notice and otherwise consistent with the terms of thisLease and Tenant fails to execute such Lease amendment within 10 business daysfollowing such tender, Tenant shall be deemed to have waived its right to leasesuch Available Space; provided, however, if Landlord desires to lease theAvailable Space on economic terms more than 5% less favorable to Landlord (asreasonably determined by Landlord), it must first offer the Available Space toTenant pursuant to a subsequent Expansion Notice and the provisions of this Section39(c) shall apply to such subsequent Expansion Notice.

(d)           **Exceptions**.  Notwithstanding the above, the ExpansionRight shall not be in effect and may not be exercised by Tenant:

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(i)            during any period of time thatTenant is in Default under any provision of the Lease; or

(ii)           if Tenant has been in Default underany provision of the Lease 3 or more times, whether or not the Defaults arecured, during the 12 month period prior to the date on which Tenant seeks toexercise the Expansion Right.

(e)           **Termination.**  The Expansion Right shall terminate and be ofno further force or effect even after Tenant’s due and timely exercise of theExpansion Right, if, after such exercise, but prior to the commencement date ofthe lease of such Available Space, (i) Tenant fails to timely cure any defaultby Tenant under the Lease; or (ii) Tenant has Defaulted 3 or more times duringthe period from the date of the exercise of the Expansion Right to the date ofthe commencement of the lease of the Available Space, whether or not suchDefaults are cured.

(f)            **Rights Personal.**  Expansion Rights are personal to Tenant andare not assignable without Landlord’s consent, which may be granted or withheldin Landlord’s sole discretion separate and apart from any consent by Landlordto an assignment of Tenant’s interest in the Lease, except that they may beassigned in connection with any Permitted Assignment of this Lease.

(g)           **SecurityDeposit Increase**.  In theevent Tenant exercises its Expansion Right, the Security Deposit shall beincreased proportionately to reflect the increase in monthly Base Rentresulting from the expansion of the Premises. In such event, Tenant shall cause to be delivered to Landlord, prior tothe date on which an amendment to the Lease is executed memorializing such expansion,a replacement or supplementary letter of credit, in accordance with and subjectto the terms of Section 6, reflecting the increased amount of theSecurity Deposit.

(h)           **No Extensions**.  The period of time within which any ExpansionRights may be exercised shall not be extended or enlarged by reason of Tenant’sinability to exercise the Expansion Rights.

40.           **Right to Extend Term. **Tenant shall have the right toextend the Term of the Lease upon the following terms and conditions:

(a)           **ExtensionRights**.  Tenant shall have 2consecutive rights (each, an “**Extension Right**”)to extend the term of this Lease for 5 years each (each, an “**Extension Term**”) on the same terms and conditions as thisLease (other than Base Rent) by giving Landlord written notice of its electionto exercise each Extension Right at least 12 months prior, and no earlier than18 months prior, to the expiration of the Base Term of the Lease or theexpiration of any prior Extension Term. Base Rent shall be adjusted (i) first, on the commencement date of suchExtension Term to the  Market Rate (asdefined below), and (ii) thereafter, on each annual anniversary of thecommencement of such Extension Term by multiplying the Base Rent payableimmediately before such adjustment by the Rent Adjustment Percentage and addingthe resulting amount to the Base Rent payable immediately before suchadjustment.  As used herein, “**Market Rate**” shall mean the then market rental rate asdetermined by Landlord and agreed to by Tenant, for comparable first-classoffice and laboratory space in the Kendall Square, Cambridge, Massachusettsarea, which shall in no event be less than the Base Rent payable as of the dateimmediately preceding the commencement of such Extension Term.  In addition, Landlord may impose a marketrent for the parking rights provided hereunder. If, on or before the date which is 120 days prior to the expiration ofthe Base Term of this Lease, or the expiration of any prior Extension Term,Tenant has not agreed with Landlord’s determination of the Market Rate and therent escalations during such subsequent Extension Term after negotiating ingood faith, Tenant may by written notice to Landlord not later than 120 daysprior to the expiration of the Base Term of this Lease, or the expiration ofany then effective Extension Term, elect arbitration as described in Section40(b) below.  If Tenant does not elect such arbitration,Tenant shall be deemed to have waived any right to extend, or further extend,the Term of the Lease and all of the remaining Extension Rights shall terminate*.*

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(b)          **Arbitration.**

(i)            Within10 days of Tenant’s notice to Landlord of its election to arbitrate Market Rateand escalations, each party shall deliver to the other a proposal containingthe Market Rate and escalations that the submitting party believes to becorrect (“**Extension Proposal**”).  If either party fails to timely submit anExtension Proposal, the other party’s submitted proposal shall determine theBase Rent and escalations for the Extension Term.  If both parties submit Extension Proposals,then Landlord and Tenant shall meet within 7 days after delivery of the lastExtension Proposal and make a good faith attempt to mutually appoint a singleArbitrator (and defined below) to determine the Market Rate and escalations.  If Landlord and Tenant are unable to agreeupon a single Arbitrator, then each shall, by written notice delivered to theother within 10 days after the meeting, select an Arbitrator.  If either party fails to timely give noticeof its selection for an Arbitrator, the other party’s submitted proposal shalldetermine the Base Rent for the Extension Term. The 2 Arbitrators so appointed shall, within 5 business days after theirappointment, appoint a third Arbitrator. If the 2 Arbitrators so selected cannot agree on the selection of thethird Arbitrator within the time above specified, then either party, on behalfof both parties, may request such appointment of such third Arbitrator byapplication to any state court of general jurisdiction in the jurisdiction inwhich the Premises are located, upon 10 days prior written notice to the otherparty of such intent.

(ii)           The decision of the Arbitrator(s)shall be made within 30 days after the appointment of a single Arbitrator orthe third Arbitrator, as applicable.  Thedecision of the single Arbitrator shall be final and binding upon theparties.  The average of the two closestArbitrators in a three Arbitrator panel shall be final and binding upon theparties.  Each party shall pay the feesand expenses of the Arbitrator appointed by or on behalf of such party and thefees and expenses of the third Arbitrator shall be borne equally by bothparties.  If the Market Rate andescalations are not determined by the first day of the Extension Term, thenTenant shall pay Landlord Base Rent in an amount equal to the Base Rent ineffect immediately prior to the Extension Term. After the determination of the Market Rate and escalations, the partiesshall make any necessary adjustments to such payments made by Tenant.  Landlord and Tenant shall then execute anamendment recognizing the Market Rate and escalations for the Extension Term.

(iii)          An “**Arbitrator**”shall be any person appointed by or on behalf of either party or appointedpursuant to the provisions hereof and: (i) shall be (A) a member of the American Institute of Real EstateAppraisers with not less than 10 years of experience in the appraisal ofimproved office and high tech industrial real estate in the greater Bostonmetropolitan area, or (B) a licensed commercial real estate broker with notless than 15 years experience representing landlords and/or tenants in theleasing of high tech or life sciences space in the greater Boston metropolitanarea, (ii) devoting substantially all of their time to professional appraisalor brokerage work, as applicable, at the time of appointment and (iii) be inall respects impartial and disinterested.

(c)          **Rights Personal.**  Extension Rights are personal to Tenant andare not assignable without Landlord’s consent, which may be granted or withheldin Landlord’s sole discretion separate and apart from any consent by Landlordto an assignment of Tenant’s interest in the Premises, except that they may beassigned in connection with any Permitted Assignment of this.

(d)          **Exceptions**.  Notwithstanding anything set forth above tothe contrary, Extension Rights shall not be in effect and Tenant may notexercise any of the Extension Rights:

(i)            during any period of time thatTenant is in Default under any provision of this Lease; or

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(ii)           if Tenant has been in Default underany provision of this Lease 3 or more times, whether or not the Defaults arecured, during the 12 month period immediately prior to the date that Tenantintends to exercise an Extension Right, whether or not the Defaults are cured;or

(iii)          if Tenant is not in occupancy of theentire Premises demised hereunder both at the time of the exercise of any suchExtension Right and at the time of the commencement date of any such ExtensionTerm

(e)           **No Extensions**.  The period of time within which any ExtensionRights may be exercised shall not be extended or enlarged by reason of Tenant’sinability to exercise the Extension Rights.

(f)            **Termination**.  The Extension Rights shall terminate and beof no further force or effect even after Tenant’s due and timely exercise of anExtension Right, if, after such exercise, but prior to the commencement date ofan Extension Term, (i) Tenant fails to timely cure any default by Tenant underthis Lease; or (ii) Tenant has Defaulted 3 or more times during the period fromthe date of the exercise of an Extension Right to the date of the commencementof the Extension Term, whether or not such Defaults are cured.

41.           **Miscellaneous**.

(a)           **Notices**.  All notices or other communications betweenthe parties shall be in writing and shall be deemed duly given upon delivery orrefusal to accept delivery by the addressee thereof if delivered in person, orupon actual receipt if delivered by reputable overnight guaranty courier,addressed and sent to the parties at their addresses set forth above.  Landlord and Tenant may from time to time bywritten notice to the other designate another address for receipt of futurenotices.

(b)           **Joint and SeveralLiability**.  If and whenincluded within the term “**Tenant**,” as usedin this instrument, there is more than one person or entity, each shall bejointly and severally liable for the obligations of Tenant.

(c)           **Financial Information**.  If at any time during the Term of the Lease,Tenant is an entity other than a company the stock of which is publicly tradedon a nationally recognized stock exchange, Tenant shall furnish Landlord withtrue and complete copies of (i) Tenant’s most recent audited annual financialstatements within 180 days of the end of each of Tenant’s fiscal years duringthe Term, (ii) Tenant’s most recent unaudited quarterly financial statementswithin 45 days of the end of each of Tenant’s first three fiscal quarters ofeach of Tenant’s fiscal years during the Term, (iii) at Landlord’s request madenot more than once per calendar year, updated business plans, including cashflow projections and/or pro forma balance sheets and income statements, all ofwhich shall be treated by Landlord as confidential information belonging toTenant, (iv) at Landlord’s request made not more than once per calendar year,corporate brochures and/or profiles prepared by Tenant for prospectiveinvestors, if any and (v) at Landlord’s request made not more than once percalendar year, any other financial information or summaries that Tenanttypically provides to its lenders or shareholders, if any.

(d)           **Recordation**.  Except to the extent necessary to comply withthe requirements of law or the regulations or policies of any securitiesexchange (and then only after at least 10 business days’ prior notice toLandlord), neither this Lease nor a memorandum of lease shall be filed by or onbehalf of Tenant in any public record. Landlord may prepare and file, and upon request by Landlord Tenant willexecute, a memorandum of lease.  Uponrequest by Tenant, Landlord will execute and Tenant shall be permitted torecord a memorandum of lease.

(e)           **Interpretation**.  The normal rule of construction to the effectthat any ambiguities are to be resolved against the drafting party shall not beemployed in the interpretation of this Lease or any exhibits or amendmentshereto.  Words of any gender used in thisLease shall be held and construed to include any other gender, and words in thesingular number shall be held to include the plural, unless the contextotherwise requires.  The captionsinserted in this Lease are for convenience only and in no way

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define, limit or otherwise describe the scope orintent of this Lease, or any provision hereof, or in any way affect theinterpretation of this Lease.

(f)            **Not Binding Until Executed**.  The submission by Landlord to Tenant of thisLease shall have no binding force or effect, shall not constitute an option forthe leasing of the Premises, nor confer any right or impose any obligationsupon either party until execution of this Lease by both parties.

(g)           **Limitations on Interest**.  It is expressly the intent of Landlord andTenant at all times to comply with applicable law governing the maximum rate oramount of any interest payable on or in connection with this Lease.  If applicable law is ever judiciallyinterpreted so as to render usurious any interest called for under this Lease,or contracted for, charged, taken, reserved, or received with respect to thisLease, then it is Landlord’s and Tenant’s express intent that all excessamounts theretofore collected by Landlord be credited on the applicableobligation (or, if the obligation has been or would thereby be paid in full,refunded to Tenant), and the provisions of this Lease immediately shall bedeemed reformed and the amounts thereafter collectible hereunder reduced,without the necessity of the execution of any new document, so as to complywith the applicable law, but so as to permit the recovery of the fullest amountotherwise called for hereunder.

(h)           **Choice of Law**.  Construction and interpretation of this Leaseshall be governed by the internal laws of the state in which the Premises arelocated, excluding any principles of conflicts of laws.

(i)            **Time**.  Time is of the essence as to the performanceof Tenant’s obligations under this Lease.

(j)            **Incorporation by Reference**.  All exhibits and addenda attached hereto arehereby incorporated into this Lease and made a part hereof.  If there is any conflict between suchexhibits or addenda and the terms of this Lease, such exhibits or addenda shallcontrol.

(k)           **Change in Form ofOwnership**.  Pursuant to M.G.L.Chapter 183A, Section 19, Landlord reserves the right to remove all or part ofthe Condominium from the provisions of M.G.L. Chapter 183A.  In the event that Landlord does remove all orpart of the Condominium from the provisions of M.G.L. Chapter 183A, the amountspayable by Tenant pursuant to this Lease shall not be greater than the amountsthat would have been otherwise payable by Tenant if Landlord had not removedall or part of the Condominium from the provisions of M.G.L. Chapter 183A.

(l)            **Hazardous Activities**.  Notwithstanding any other provision of thisLease, Landlord, for itself and its employees, agents and contractors, reservesthe right to refuse to perform any repairs or services in any portion of thePremises which, pursuant to Tenant’s routine safety guidelines, practices orcustom or prudent industry practices, require any form of protective clothingor equipment other than safety glasses. In any such case, Tenant shall contract with parties who are acceptableto Landlord, in Landlord’s reasonable discretion, for all such repairs andservices, and Landlord shall, to the extent required, equitably adjust Tenant’sShare of Operating Expenses in respect of such repairs or services to reflectthat Landlord is not providing such repairs or services to Tenant.

**[ Signatures on next page]**

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IN WITNESS WHEREOF, Landlord and Tenant have executedthis Lease as of the day and year first above written.
| ** ** | **TENANT:**                                                 |
|------------|-------------------------------------------------------------|
| ** ** | ** **                                                  |   |
|       | SIRTRIS PHARMACEUTICALS, INC.,                              |
|       | a Delaware corporation                                      |
|       |                                                        |
|       | By:                                                         | /s/ GAREN BOHLIN |
|       | Its:                                                        | Chief Operating Officer |
|       |                                                        |   |
|       |                                                        |   |
| ** ** | **LANDLORD:**                                               |
| ** ** | ** **                                                  |
|       | ARE-TECH SQUARE, LLC, a Delaware limited liability  company |
|       |                                                        |
|       | By:                                                         | ARE-MA REGION NO. 31, LLC, a Delaware limited  liability company, its Member |
|       |                                                        |   |
|       |                                                        | By: | ALEXANDRIA REAL ESTATE EQUITIES, L.P.,  a Delaware limited partnership, its Member |
|       |                                                        |   |   |   |
|       |                                                        |   | By: | ARE-QRS CORP., a Maryland  corporation, its General Partner |
|       |                                                        |   |   |   |
|       |                                                        |   |   | By: |  /s/ Jackie Clem |
|       |                                                        |   |   |   Name: Jackie Clem |
|       |                                                        |   |   |   Title: Vice President |
|            |                                                             |  |  |  |  |  |  |

 

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**EXHIBIT A TO LEASE**

**DESCRIPTION OF PREMISES**

Exhibit A

200 Technology Square

First Floor

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Exhibit A

200 Technology Square

Second Floor

2

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Exhibit A

200 Technology Square

Third Floor

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Exhibit A

200 Technology Square

Fourth Floor

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Exhibit A

200 Technology Square

Basement Floor

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**EXHIBIT B TO LEASE**

**DESCRIPTION OF PROJECT**

The following parcels ofland in Cambridge, Middlesex County, Massachusetts:

The Registered Land shownas Lots 15, 16 and 19 on Land Court Plan No. 30711E, Lot 43 on Land Court PlanNo. 30711J and Lots 46 and 47 on Land Court Plan No. 30711K, and

The Unregistered Landshown as Area No. 1, Area No. 2, Area No. 3, Area No. 4, Area No. 5, Area No.6, Area No. 7, Area No. 8 and Area No. 9 on a plan entitled “Plan of Land andEasements, Cambridge, Mass.”  Prepared byRaymond C. Pressey, Inc., dated June 1970 and recorded with the Middlesex SouthRegistry of Deeds in Book 11879, Page 393, Plan 852 (A of 2) of 1970.

Excepting therefrom thatportion taken by the Cambridge Redevelopment Authority Eminent Domain Takingdated April 12, 1982 and recorded in Book 14590, Page 221 and that portiontaken by the Cambridge Redevelopment Authority Eminent Domain Taking datedJanuary 27, 1983 and recorded in Book 14891, Page 556.

Said parcels are alsodescribed as Units 100, 200, 300, 400, 500, 600 and 700 of that certaincondominium known as the Technology Square Condominium, as set forth in thatcertain Master Deed dated November 30, 2000, executed by Technology Square LLC,and recorded with the Registry in Book 32159, at Page 490, and registered withthe Land Court as Document No. 1158816, under Certificate of Title No.C404, as the same has been amended by that certain Amendment to Master Deeddated May 28, 2002, and recorded with the Registry as Instrument No. 690 onSeptember 6, 2002, and registered with the Land Court as Document No. 1226564,and as the same has been amended by that certain Second Amendment to MasterDeed dated as of November 15, 2002, and recorded with the Registry asInstrument No. 1617 on September 23, 2003, and registered with the Land Courtas Document No. 1293465.

Together with the benefitof the following:

**1.**              Terms and provisions of Reciprocal Easement Agreement dated April 18,2000 by and between Technology Square LLC and the Charles Stark DraperLaboratory, Inc. recorded in Book 31324, Page 262 and filed as Documents No.1137080.

**2.**              Terms and provisions of Foundation, Grade Beam and EncroachmentAgreement dated March 11, 1975, filed as Document No. 531493, as amended by anAmendment to Foundation Grade Beam and Encroachment Agreement, dated September1, 1976, filed as Document No. 547840, affecting Lots 19 and 20, as affected byReciprocal Easement Agreement dated April 18, 2000 recorded in Book 31324, Page262 and filed as Document No. 1137080.

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**EXHIBIT C TO LEASE**

**WORK LETTER**

THIS WORK LETTER (this “**Work Letter**”)is incorporated into that certain Lease (the “**Lease**”)dated as of June         , 2007 by andbetween ARE-TECH SQUARE, LLC, a Delaware limited liability company (“**Landlord**”), and SIRTRIS PHARMACEUTICALS, INC., a Delawarecorporation (“**Tenant**”).  Any initially capitalized terms used but notdefined herein shall have the meanings given them in the Lease.

1.             **General Requirements.**

(a)           **Tenant’s Authorized Representative**.  Tenant designates Peggy Romero and PaulBrannelly (either such individual acting alone, “Tenant’s Representative”) asthe only persons authorized to act for Tenant pursuant to this WorkLetter.  Landlord shall not be obligatedto respond to or act upon any request, approval, inquiry or other communication(“Communication”) from or on behalf of Tenant in connection with this WorkLetter unless such Communication is in writing from Tenant’sRepresentative.  Tenant may change eitherTenant’s Representative at any time upon not less than 5 business days advancewritten notice to Landlord.  NeitherTenant nor Tenant’s Representative shall be authorized to direct Landlord’scontractors in the performance of Landlord’s Work (as hereinafter defined).

(b)           **Landlord’s Authorized Representative**.  Landlord designates Tom Andrews and Tim White(either such individual acting alone, “Landlord’s Representative”) as the onlypersons authorized to act for Landlord pursuant to this Work Letter.  Tenant shall not be obligated to respond toor act upon any request, approval, inquiry or other Communication from or onbehalf of Landlord in connection with this Work Letter unless suchCommunication is in writing from Landlord’s Representative.  Landlord may change either Landlord’sRepresentative at any time upon not less than 5 business days advance writtennotice to Tenant. Landlord’s Representative shall be the sole personsauthorized to direct Landlord’s contractors in the performance of Landlord’sWork.

(c)           **Architects, Consultants and Contractors.**  Landlord and Tenant hereby acknowledge andagree that:  (i) the general contractorand any subcontractors for the Tenant Improvements shall be selected byLandlord, subject to Tenant’s approval, which approval shall not beunreasonably withheld, conditioned or delayed, and (ii) R.E. DineenAssociates shall be the architect (the “TI Architect”) for the TenantImprovements.

2.             **Tenant Improvements.**

(a)           **Tenant Improvements Defined.**  As used herein, “Tenant Improvements” shallmean all improvements to the Project of a fixed and permanent nature as shownon the TI Construction Drawings, as defined in Section 2(c) below.  Other than Landlord’s Work (as defined inSection 3(a) below, Landlord shall not have any obligation whatsoever withrespect to the finishing of the Premises for Tenant’s use and occupancy.

(b)           **Tenant’s Space Plans.**  Tenant’s schematic drawings and outlinespecifications (the “TI Design Drawings”) detailing Tenant’s requirements forthe Tenant Improvements are attached hereto as Exhibit 1.  Not more than 10 days after the date of theLease, Landlord shall deliver to Tenant the written objections, questions orcomments of Landlord and the TI Architect with regard to the TI DesignDrawings.  Tenant shall cause the TIDesign Drawings to be revised to address such written comments and shallresubmit said drawings to Landlord for approval within 10 days thereafter.  Such process shall continue until Landlordhas approved the TI Design Drawings.

(c)           **Working Drawings.**  Not Later than 10 business days following theapproval of the TI Design Drawings, Landlord shall cause the TI Architect toprepare and deliver to Tenant for review and

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comment constructionplans, specifications and drawings for the Tenant Improvements (the “TIConstruction Drawings”), which TI Construction Drawings shall be preparedsubstantially in accordance with the TI Design Drawings.  Tenant shall be solely responsible forensuring that the TI Construction Drawings reflect Tenant’s requirements forthe Tenant Improvements.  Tenant shalldeliver its written comments on the TI Construction Drawings to Landlord notlater than 10 business days after Tenant’s receipt of the same; provided,however, that Tenant may not disapprove any matter that is consistent with theTI Design Drawings without submitting a Change Request.  Landlord and the TI Architect shall considerall such comments in good faith and shall, within 10 business days afterreceipt, notify Tenant how Landlord proposes to respond to such comments, butTenant’s review rights pursuant to the foregoing sentence shall not delay thedesign or construction schedule for the Tenant Improvements.  Any disputes in connection with such commentsshall be resolved in accordance with Section 2(d) hereof.  Provided that the design reflected in the TI ConstructionDrawings is consistent with the TI Design Drawings, Tenant shall approve the TIConstruction Drawings submitted by Landlord, unless Tenant submits a ChangeRequest.  Once approved by Tenant,subject to the provisions of Section 4 below, Landlord shall not materiallymodify the TI Construction Drawings except as may be reasonably required inconnection with the issuance of the TI Permit (as defined in Section 3(b)below).

(d)           **Approval and Completion.**  It is hereby acknowledged by Landlord and Tenantthat the TI Construction Drawings must be completed and approved not later thanJune 15, 2007, in order for the Landlord’s Work to be Substantially Complete bythe Target Commencement Date (as defined in the Lease).  Upon any dispute regarding the design of theTenant Improvements, which is not settled within 10 business days after noticeof such dispute is delivered by one party to the other, Tenant may make thefinal decision regarding the design of the Tenant Improvements, provided (i)Tenant acts reasonably and such final decision is either consistent with or acompromise between Landlord’s and Tenant’s positions with respect to suchdispute, (ii) that all costs and expenses resulting from any such decision byTenant shall be payable out of the TI Fund (as defined in Section 5(d) below),and (iii) Tenant’s decision will not affect the base Building, structuralcomponents of the Building or any Building systems.  Any changes to the TI Construction Drawingsfollowing Landlord’s and Tenant’s approval of same requested by Tenant shall beprocessed as provided in Section 4 hereof.

3.             **Performance of Landlord’s Work.**

(a)           **Definition of Landlord’s Work.**  As used herein, “Landlord’s Work” shall meanthe work of constructing the Tenant Improvements and completing the basebuilding work for the Building in accordance with the Base Building descriptionattached hereto as Exhibit 2.

(b)           **Commencement and Permitting.**  Landlord shall commence construction of theTenant Improvements upon obtaining a building permit (the “TI Permit”)authorizing the construction of the Tenant Improvements consistent with the TIConstruction Drawings approved by Tenant. The cost of obtaining the TI Permit shall be payable from the TI Fund.  Tenant shall assist Landlord in obtaining theTI Permit.  If any Governmental Authorityhaving jurisdiction over the construction of Landlord’s Work or any portionthereof shall impose terms or conditions upon the construction thereofthat:  (i) are inconsistent with Landlord’sobligations hereunder, (ii) increase the cost of constructing Landlord’s Work,or (iii) will materially delay the construction of Landlord’s Work, Landlordand Tenant shall reasonably and in good faith seek means by which to mitigateor eliminate any such adverse terms and conditions.

(c)           **Completion of Landlord’s Work.**  On or before the Target Commencement Date(subject to Tenant Delays and Force-Majeure Delays), Landlord shallsubstantially complete or cause to be substantially completed Landlord’s Workin a good and workmanlike manner, in accordance with the TI Permit subject, ineach case, to Minor Variations and normal “punch list” items of a non-materialnature that do not interfere with the use of the Premises and obtain acertificate of occupancy or temporary certificate of occupancy from the officeof the Building Inspector of the City of Cambridge with respect to the Landlord’sWork (“Substantial Completion” or “Substantially Complete”).  Upon Substantial Completion of Landlord’sWork, Landlord shall require the TI Architect and the general contractor toexecute and deliver, for the benefit of Tenant and Landlord, a Certificate ofSubstantial Completion in the form of the American Institute of Architects (“AIA”)document G704.  For purposes of this WorkLetter,

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“Minor Variations” shallmean any modifications reasonably required: (i) to comply with all applicable Legal Requirements and/or to obtain orto comply with any required permit (including the TI Permit) provided that suchmodification is not likely to have a material adverse effect on Tenant’s use ofthe Premises or materially affect the ability to promptly obtain a permanentCertificate of Occupancy for the Premises; (ii) to comply with any request byTenant for modifications to Landlord’s Work; (iii) to comport with good design,engineering, and construction practices that are not material; or (iv) to makereasonable adjustments for field deviations or conditions encountered duringthe construction of Landlord’s Work.

(d)           **Selection of Materials.**  Where more than one type of material orstructure is indicated on the TI Construction Drawings approved by Landlord andTenant, the option will be selected at Landlord’s sole and absolute subjectivediscretion.  As to all building materialsand equipment that Landlord is obligated to supply under this Work Letter,Landlord shall select the manufacturer thereof in its sole and absolutesubjective discretion.

(e)           **Delivery of the Premises.**  When Landlord’s Work is SubstantiallyComplete, subject to the remaining terms and provisions of this Section 3(e),Tenant shall accept the Premises.  Tenant’staking possession and acceptance of the Premises shall not constitute a waiverof:  (i) any warranty with respect toworkmanship (including installation of equipment) or material (exclusive ofequipment provided directly by manufacturers), (ii) any non-compliance ofLandlord’s Work with applicable Legal Requirements, or (iii) any claim thatLandlord’s Work was not completed substantially in accordance with the TIConstruction Drawings (subject to Minor Variations and such other changes asare permitted hereunder) (collectively, a “Construction Defect”).  Tenant shall have one year after SubstantialCompletion within which to notify Landlord of any such Construction Defectdiscovered by Tenant, and Landlord shall use reasonable efforts to remedy orcause the responsible contractor to remedy any such Construction Defect within30 days thereafter.  Notwithstanding theforegoing, Landlord shall not be in default under the Lease if the applicablecontractor, despite Landlord’s reasonable efforts, fails to remedy suchConstruction Defect within such 30-day period, in which case Landlord shallhave no further obligation with respect to such Construction Defect other thanto cooperate, at no cost to Landlord, with Tenant should Tenant elect to pursuea claim against such contractor, provided that Tenant shall defend with counselreasonably acceptable to Landlord, indemnify and hold Landlord harmless fromand against any claims arising out of or in connection with any such claim.

Tenant shall be entitled to receive the benefit of allconstruction warranties and manufacturer’s equipment warranties relating toequipment installed in the Premises.  Ifrequested by Tenant, Landlord shall attempt to obtain extended warranties frommanufacturers and suppliers of such equipment, but the cost of any suchextended warranties shall be borne solely out of the TI Fund.  Landlord shall promptly undertake andcomplete, or cause to be completed, all punch list items.

(f)            **Commencement Date Delay.**  Except as otherwise provided in the Lease,Delivery of the Premises shall occur when Landlord’s Work has beenSubstantially Completed, except to the extent that completion of Landlord’sWork shall have been actually delayed by any one or more of the followingcauses (“Tenant Delay”):

(i)            Tenant’sRepresentative was not available to give or receive any Communication or totake any other action required to be taken by Tenant hereunder;

(ii)           Tenant’srequest for Change Requests (as defined in Section 4(a) below) whether or notany such Change Requests are actually performed;

(iii)          Constructionof any Change Requests;

(iv)          Tenant’srequest for materials, finishes or installations requiring unusually long leadtimes;

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(v)           Tenant’sdelay in reviewing, revising or approving plans and specifications beyond theperiods set forth herein;

(vi)          Tenant’sdelay in providing information critical to the normal progression of theProject.  Tenant shall provide suchinformation as soon as reasonably possible, but in no event longer than oneweek after receipt of any request for such information from Landlord;

(vii)         Tenant’sdelay in making payments to Landlord for Excess TI Costs (as defined in Section5(d) below); or

(viii)        Anyother act or omission by Tenant or any Tenant Party (as defined in the Lease),or persons employed by any of such persons.

If Delivery is delayed for any of the foregoingreasons, then Landlord shall cause the TI Architect to certify the date onwhich the Tenant Improvements would have been completed but for such TenantDelay and such certified date shall be the date of Delivery.

4.             **Changes.** Any changes requested by Tenant to the Tenant Improvements after thedelivery and approval by Landlord of the TI Design Drawings shall be requestedand instituted in accordance with the provisions of this Section 4 and shall besubject to the written approval of Landlord and the TI Architect, such approvalnot to be unreasonably withheld, conditioned or delayed.

(a)           **Tenant’s Request For Changes.**  If Tenant shall request changes to the TenantImprovements (“Changes”), Tenant shall request such Changes by notifyingLandlord in writing in substantially the same form as the AIA standard changeorder form (a “Change Request”), which Change Request shall detail the natureand extent of any such Change.  SuchChange Request must be signed by Tenant’s Representative.  Landlord shall, before proceeding with anyChange, use commercially reasonable efforts to respond to Tenant as soon as isreasonably possible with an estimate of: (i) the time it will take, and (ii) the architectural and engineeringfees and costs that will be incurred, to analyze such Change Request (whichcosts shall be paid from the TI Fund to the extent actually incurred, whether ornot such change is implemented). Landlord shall thereafter submit to Tenant in writing, within 5 businessdays of receipt of the Change Request (or such longer period of time as isreasonably required depending on the extent of the Change Request), an analysisof the additional cost or savings involved, including, without limitation,architectural and engineering costs and the period of time, if any, that theChange will extend the date on which Landlord’s Work will be SubstantiallyComplete.  Any such delay in thecompletion of Landlord’s Work caused by a Change, including any suspension ofLandlord’s Work while any such Change is being evaluated and/or designed, shallbe Tenant Delay.

(b)           **Implementation of Changes.**  If Tenant: (i) approves in writing the cost or savings and the estimated extensionin the time for completion of Landlord’s Work, if any, and (ii) deposits withLandlord any Excess TI Costs required in connection with such Change, Landlordshall cause the approved Change to be instituted.  Notwithstanding any approval or disapprovalby Tenant of any estimate of the delay caused by such proposed Change, the TIArchitect’s determination of the amount of Tenant Delay in connection with suchChange shall be final and binding on Landlord and Tenant.

5.             **Costs.**

(a)           **Budget For Tenant Improvements.**  Before the commencement of construction ofthe Tenant Improvements, Landlord shall obtain from The Richmond Group oranother contractor reasonably approved by Landlord and Tenant a detailedbreakdown by trade of the costs incurred or that will be incurred in connectionwith the design and construction of the Tenant Improvements (the “Budget”).  The Budget shall be based upon the TIConstruction Drawings approved by Tenant and shall include a payment to Landlordof administrative rent (“Administrative Rent”) equal to 3% of the TI Costs (netof soft costs, including architectural, consulting and engineering costs) formonitoring and inspecting the construction of the Tenant Improvements andChanges, which sum shall be payable from the TI Fund (as

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defined in Section5(d).  Administrative Rent shall include,without limitation, all out-of-pocket costs, expenses and fees incurred by oron behalf of Landlord arising from, out of, or in connection with monitoring theconstruction of the Tenant Improvements and Changes, and shall be payable outof the TI Fund.  If the Budget is greaterthan the TI Allowance, Tenant shall deposit with Landlord the difference, incash, prior to the commencement of construction of the Tenant Improvements orChanges, for disbursement by Landlord as described in Section 5(d).

(b)           **TI Allowance.**  Landlord shall provide to Tenant a tenantimprovement allowance (the “TI Allowance”) of $180.00 per rentable square footof the Premises (which, based on 44,084 rentable square feet initially demisedunder the Lease, equates to $7,935,120.00 in the aggregate).  Within 10 business days of receipt of theBudget from Landlord, Tenant shall notify Landlord how much of the TI AllowanceTenant has elected to receive from Landlord. Such election shall be final and binding on Tenant, and may notthereafter be modified without Landlord’s consent, which may be granted orwithheld in Landlord’s sole and absolute subjective discretion.  The TI Allowance shall be disbursed inaccordance with this Work Letter.  Tenantshall have no right to the use or benefit (including any reduction to orpayment of Base Rent) of any portion of the TI Allowance not required for TICosts (“Unrequired TI Allowance”), except that Tenant shall be entitled toreceive any Unrequired TI Allowance with respect to any space leased to Tenantdirectly by Landlord in the Building (pursuant to this Lease or otherwise), forAlterations thereto provided that (i) such Alterations are completed no laterthan twenty-four (24) months after the Commencement Date, (ii) thedisbursement of such Unrequired TI Allowance shall be subject to Landlord’sreasonable requirements consistent with the Lease and this Work Letter and(iii) a written request for such disbursement satisfying all suchrequirements shall have been received by Landlord no later than twenty-four(24) months after the Commencement Date.

(c)           **Costs Includable in TI Fund.** The TI Fund shall be used solely for thepayment of design, permits and construction costs in connection with theconstruction of the Tenant Improvements, including, without limitation, thecost of electrical power and other utilities used in connection with theconstruction of the Tenant Improvements, the cost of preparing the TI DesignDrawings and the TI Construction Drawings, all costs set forth in the Budget,including Landlord’s Administrative Rent, Landlord’s out-of-pocket expenses,costs resulting from Tenant Delays and the cost of Changes (collectively, “TICosts”), provided, however, that Tenant shall not be entitled to utilize anymore than 5% of the TI Allowance for architectural, consulting and engineeringcosts.  Notwithstanding anything to thecontrary contained herein, the TI Fund shall not be used to purchase anyfurniture, personal property or other non-Building system materials orequipment, including, but not limited to, Tenant’s voice or data cabling,non-ducted biological safety cabinets and other scientific equipment notincorporated into the Tenant Improvements.

(d)           **Excess TI Costs.**  Landlord shall have no obligation to bear anyportion of the cost of any of the Tenant Improvements except to the extent ofthe TI Allowance, it being agreed that Landlord will enter into a so-called “openbook” construction contract for the Tenant Improvements with The Richmond Groupor such other contractor reasonably approved by Landlord and Tenant.  If at any time the remaining TI Costs underthe Budget exceed the remaining unexpended TI Allowance, Tenant shall depositwith Landlord, as a condition precedent to Landlord’s obligation to completethe Tenant Improvements, 100% of the then current TI Cost in excess of theremaining TI Allowance (“Excess TI Costs”). If Tenant fails to deposit any Excess TI Costs with Landlord, Landlordshall have all of the rights and remedies set forth in the Lease for nonpaymentof Rent (including, but not limited to, the right to interest at the DefaultRate and the right to assess a late charge). For purposes of any litigation instituted with regard to such amounts,those amounts will be deemed Rent under the Lease.  The TI Allowance and Excess TI Costs areherein referred to as the “TI Fund.” Funds deposited by Tenant shall be the first disbursed to pay TICosts.  Notwithstanding anything to thecontrary set forth in this Section 5(d), Tenant shall be fully and solelyliable for TI Costs and the cost of Minor Variations in excess of the TIAllowance.  If upon SubstantialCompletion of the Tenant Improvements and the payment of all sums due inconnection therewith there remains any undisbursed portion of the TI Fund,Tenant shall be entitled to such undisbursed TI Fund solely to the extent ofany Excess TI Costs deposit Tenant has actually made with Landlord.

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6.             **Tenant Access.**

(a)           **Tenant’s Access Rights.**  Landlord hereby agrees to permit Tenantaccess, at Tenant’s sole risk and expense, to the Building (i) subject toLandlord’s prior written consent, prior to the Commencement Date to perform anywork (“Tenant’s Work”) required by Tenant other than Landlord’s Work, providedthat such Tenant’s Work is coordinated with the TI Architect and the generalcontractor, and complies with the Lease and all other reasonable restrictionsand conditions Landlord may impose, and (ii) prior to the completion ofLandlord’s Work, to inspect and observe work in process; all such access shallbe during normal business hours or at such other times as are reasonablydesignated by Landlord.  Notwithstandingthe foregoing, Tenant shall have no right to enter onto the Premises or theProject unless and until Tenant shall deliver to Landlord evidence reasonablysatisfactory to Landlord demonstrating that any insurance reasonably requiredby Landlord in connection with such pre-commencement access (including, but notlimited to, any insurance that Landlord may require pursuant to the Lease) isin full force and effect.  Any entry byTenant shall comply with all established safety practices of Landlord’scontractor and Landlord until completion of Landlord’s Work and acceptancethereof by Tenant.

(b)           **No Interference.**  Neither Tenant nor any Tenant Party (asdefined in the Lease) shall interfere with the performance of Landlord’s Work,nor with any inspections or issuance of final approvals by applicableGovernmental Authorities, and upon any such interference, Landlord shall havethe right to exclude Tenant and any Tenant Party from the Premises and theProject until Substantial Completion of Landlord’s Work.

(c)           **No Acceptance of Premises.**  The fact that Tenant may, with Landlord’sconsent, enter into the Project prior to the date Landlord’s Work isSubstantially Complete for the purpose of performing Tenant’s Work shall not bedeemed an acceptance by Tenant of possession of the Premises, but in such eventTenant shall defend with counsel reasonably acceptable by Landlord, indemnifyand hold Landlord harmless from and against any loss of or damage to Tenant’sproperty, completed work, fixtures, equipment, materials or merchandise, andfrom liability for death of, or injury to, any person, caused by the act oromission of Tenant or any Tenant Party.

7.             **Miscellaneous.**

(a)           **Consents.** Whenever consent or approval of either party is required under this WorkLetter, that party shall not unreasonably withhold, condition or delay such consentor approval, unless expressly set forth herein to the contrary.

(b)           **Modification.**  No modification, waiver or amendment of thisWork Letter or of any of its conditions or provisions shall be binding uponLandlord or Tenant unless in writing signed by Landlord and Tenant.

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Exhibit 1 to WorkLetter

TI Design Drawings

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Exhibit

SirtrisPharmaceuticals, Inc.

Document List
| **No.**                                                                         | ** ** | **Title**                                                      | ** ** | **Date** | ** ** |
|---------------------------------------------------------------------------------|------------|----------------------------------------------------------------|------------|----------|------------|
|                                                                            |       |                                                           |       |     |       |
| Drawing prepared by R.E. Dinneen Architects &  Planners, Inc. of Boston, MA |       |                                                           |       |
|                                                                            |       |                                                           |       |     |       |
| T-0.1                                                                           |       | Title Sheet - Drawing List                                     |       | 5/18/07  |       |
| T-0.2                                                                           |       | Code Plans                                                     |       | 5/18/07  |       |
| T-0.3                                                                           |       | Partition Types, Misc.                                         |       | 5/18/07  |       |
| A-1.1                                                                           |       | First Floor Plan                                               |       | 5/18/07  |       |
| A-1.2                                                                           |       | Second Floor Construction Plan                                 |       | 5/18/07  |       |
| A-1.3                                                                           |       | Third Floor Construction Plan                                  |       | 5/18/07  |       |
| A-2.2                                                                           |       | Second Floor Reflected Ceiling Plan                            |       | 5/18/07  |       |
| A-2.3                                                                           |       | Third Floor Reflected Ceiling Plan                             |       | 5/18/07  |       |
| A-3.2                                                                           |       | Second Floor Furniture & Equipment Plan                    |       | 5/18/07  |       |
| A-3.3                                                                           |       | Third Floor Furniture & Equipment Plan                     |       | 5/18/07  |       |
| A-4.2                                                                           |       | Second Floor Finish Plan & Schedule                        |       | 5/18/07  |       |
| A-4.3                                                                           |       | Third Floor Finish Plan & Schedule                         |       | 5/18/07  |       |
| A-5.1                                                                           |       | Interior Elevations & Details                              |       | 5/18/07  |       |
| A-5.2                                                                           |       | Interior Elevations & Details                              |       | 5/18/07  |       |
| A-6.2                                                                           |       | Second Floor Sections & Details                            |       | 5/18/07  |       |
| A-6.3                                                                           |       | Third Floor Sections & Details                             |       | 5/18/07  |       |
| A-7.1                                                                           |       | Door Schedule                                                  |       | 5/18/07  |       |
| A-8.1                                                                           |       | Lab Casework Elevations                                        |       | 5/18/07  |       |
| A-8.2                                                                           |       | Lab Casework Elevations                                        |       | 5/18/07  |       |
| A-8.3                                                                           |       | Lab Casework Elevations                                        |       | 5/18/07  |       |
| A-8.4                                                                           |       | Lab Casework Elevations                                        |       | 5/18/07  |       |
|                                                                            |       |                                                           |       |     |       |
| Drawings prepared by AHA Consulting Engineering,  Inc. of Lexington, MA         |       |                                                           |       |
|                                                                            |       |                                                           |       |     |       |
| P001                                                                            |       | Plumbing Legend                                                |       | 5/18/07  |       |
| P100                                                                            |       | Plumbing Basement Plan                                         |       | 5/18/07  |       |
| P101                                                                            |       | Plumbing First Floor Plan                                      |       | 5/18/07  |       |
| P102                                                                            |       | Plumbing Preliminary Layout Lower Floor                        |       | 5/18/07  |       |
| P103                                                                            |       | Plumbing Preliminary Layout Upper Floor                        |       | 5/18/07  |       |
|                                                                            |       |                                                           |       |     |       |
| FA100                                                                           |       | Fire Alarm Legend, Details, Notes, &  Specifications       |       | 5/18/07  |       |
| FA101                                                                           |       | Fire Alarm Upper & Lower Floor Plans                       |       | 5/18/07  |       |
|                                                                            |       |                                                           |       |     |       |
| FP100                                                                           |       | Fire Protection Ledgend, Details, Notes, &  Specifications |       | 5/18/07  |       |
| FP101                                                                           |       | Fire Protection Upper & Lower Floor Plans                  |       | 5/18/07  |       |
|                                                                            |       |                                                           |       |     |       |
| H001                                                                            |       | HVAC Legend, Abbreviations & General Notes                 |       | 5/18/07  |       |
| H002                                                                            |       | HVAC Schedules                                                 |       | 5/18/07  |       |
| H003                                                                            |       | HVAC Details 1                                                 |       | 5/18/07  |       |
| H004                                                                            |       | HVAC Details 2                                                 |       | 5/18/07  |       |
| H101                                                                            |       | HVAC Second Floor Plan                                         |       | 5/18/07  |       |
| H102                                                                            |       | HVAC Third Floor Plan                                          |       | 5/18/07  |       |

 

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| E001                                                                          |   | Electrical Legend & Notes                          |   | 5/18/07     |   |
|-------------------------------------------------------------------------------|--------|--------------------------------------------------------|--------|-------------|--------|
| E002                                                                          |   | Electrical Riser Diagram                               |   | 5/18/07     |   |
| E102                                                                          |   | Electrical Second Floor Power Plan                     |   | 5/18/07     |   |
| E103                                                                          |   | Electrical Third Floor Power Plan                      |   | 5/18/07     |   |
| E202                                                                          |   | Electrical Second Floor Lighting Plan                  |   | 5/18/07     |   |
| E203                                                                          |   | Electrical Third Floor Lighting Plan                   |   | 5/18/07     |   |
|                                                                          |   |                                                   |   |        |   |
| Specifications prepared by AHA Consulting  Engineering, Inc. of Lexington, MA |   |                                                   |   |
|                                                                          |   |                                                   |   |        |   |
| 15300                                                                         |   | Fire Protection                                        |   | 5/18/07     |   |
| 15400                                                                         |   | Plumbing                                               |   | 5/18/07     |   |
| 15500                                                                         |   | Heating, Ventilating & Air Conditioning            |   | 5/18/07     |   |
|                                                                          |   |                                                   |   |        |   |
| 16000                                                                         |   | Electrical                                             |   | 5/18/07     |   |
| 16700                                                                         |   | Fire Alarm                                             |   | 5/18/07     |   |
|                                                                          |   |                                                   |   |        |   |
| Misc. Documents                                                               |   |                                                   |   |
| —                                                                        |   | Equipment Utility Matrix (The Richmond Group)          |   | 5/30/07     |   |
| —                                                                        |   | M/E/P/FP Basis of Design (AHA Consulting  Engineering) |   | rev 5/31/07 |   |

 

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Exhibit2 to Work Letter

Landlord’sWork

Landlord’s Work

**200Technology Square – Core and Shell UpgradeRichmond Project No. 120006Drawing ListMarch 30, 2007**
| **Document  Number** | ** ** | **Drawing Title**                                                 | ** ** | **Drawing Date**  |
|----------------------|------------|-------------------------------------------------------------------|------------|-------------------|
| A-0                  |       | Cover Sheet                                                       |       |              |
| A-0.1                |       | LEED Notes                                                        |       | February 23, 2007 |
|                 |       |                                                              |       |              |
| C1.1                 |       | Site Preparation Plan                                             |       | January 26, 2007  |
| C2.1                 |       | Grading & Layout Plan                                         |       | February 23, 2007 |
| C3.1                 |       | Utilities Plan                                                    |       | February 23, 2007 |
| C4.1                 |       | Civil Details                                                     |       | January 26, 2007  |
|                 |       |                                                              |       |              |
| D1.0                 |       | Ground Floor Demolition Plan                                      |       | January 26, 2007  |
| A2.0                 |       | Basement Plan                                                     |       | February 23, 2007 |
| A2.1                 |       | Ground Floor Plan                                                 |       | February 23, 2007 |
| A2.2                 |       | Typical Floor Plan (Floors 2-9)                                   |       | January 26, 2007  |
| A2.3                 |       | Tenth Floor Plan                                                  |       | February 23, 2007 |
| A2.4                 |       | Penthouse / Roof Plan                                             |       | February 23, 2007 |
| A2.5                 |       | Doors / Partition Types & Schedules                           |       | February 23, 2007 |
|                 |       |                                                              |       |              |
| A3.1                 |       | Loading Dock / Ramp Plan & Section                            |       | February 23, 2007 |
| A3.2                 |       | Loading Dock / Ramp Details                                       |       | January 26, 2007  |
|                 |       |                                                              |       |              |
| A6.0                 |       | Basement Reflected Ceiling Plan                                   |       | February 23, 2007 |
| A6.1                 |       | Ground Floor Reflected Ceiling Plan                               |       | February 23, 2007 |
| A6.2                 |       | Tenth Floor Reflected Ceiling Plan                                |       | January 26, 2007  |
|                 |       |                                                              |       |              |
| S1.0                 |       | General Notes                                                     |       | January 26, 2007  |
| S2.0                 |       | First Floor / Foundation Framing Plan                             |       | January 26, 2007  |
| S2.1                 |       | Existing Second Floor Framing Plan                                |       | January 26, 2007  |
| S2.2                 |       | Existing 10th Floor and Roof Framing Plan                    |       | February 23, 2007 |
| S2.3                 |       | New Roof Grillage Framing Plan                                    |       | February 23, 2007 |
| S3.0                 |       | Sections & Details Sheet One                                  |       | January 26, 2007  |
| S3.1                 |       | Sections & Details Sheet Two                                  |       | January 26, 2007  |
| S3.2                 |       | Sections & Details Sheet Three                                |       | February 23, 2007 |
|                 |       |                                                              |       |              |
| FA1.0                |       | Fire Alarm Legend, Details, Basement & First  Floor Plans     |       | January 26, 2007  |
| FA1.1                |       | Fire Alarm Typical & Tenth Floor Plans                        |       | January 26, 2007  |
|                 |       |                                                              |       |              |
| FP1.0                |       | Fire Protection Legend, Details Basement & First  Floor Plans |       | January 26, 2007  |
| FP1.1                |       | Fire Protection Typical & Tenth Floor Plans                   |       | January 26, 2007  |

 

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| P0.1   |   | Plumbing Legend, Diagrams & Schedules                          |   | January 26, 2007  |
|--------|--------|--------------------------------------------------------------------|--------|-------------------|
| P0.2   |   | Plumbing Riser Diagrams                                            |   | February 23, 2007 |
| P1.0   |   | Plumbing Basement Plan                                             |   | January 26, 2007  |
| P1.1   |   | Plumbing First Floor Plan                                          |   | January 26, 2007  |
| P1.2   |   | Plumbing Typical Floors 2nd Thru 9th Plan                          |   | February 23, 2007 |
|   |   |                                                               |   |              |
| P1.3   |   | Plumbing Tenth Floor Plan                                          |   | February 23, 2007 |
| P1.4   |   | Plumbing Roof Plan                                                 |   | February 23, 2007 |
|   |   |                                                               |   |              |
| H0.1   |   | HVAC Legend, Abbreviations & General Notes                     |   | January 26, 2007  |
| H0.2   |   | HVAC Schedules                                                     |   | February 23, 2007 |
| H0.3D  |   | HVAC CHW Piping Schematic Demolition                               |   | February 23, 2007 |
| H0.3   |   | HVAC CHW & CW Piping Schematics                                |   | January 26, 2007  |
| H0.4   |   | HVAC HW Piping Schematic                                           |   | January 26, 2007  |
| H0.5D  |   | HVAC Air Riser Diagrams Demolition                                 |   | January 26, 2007  |
| H0.5   |   | HVAC Air Riser Diagram                                             |   | January 26, 2007  |
| H0.6   |   | HVAC Custom Air Handling Units                                     |   | January 26, 2007  |
| H0.7   |   | HVAC Details 1                                                     |   | January 26, 2007  |
| H0.8   |   | HVAC Details 2                                                     |   | January 26, 2007  |
| H0.9   |   | HVAC Details 3                                                     |   | January 26, 2007  |
| H1.0D  |   | HVAC Basement Floor Plan Demolition                                |   | January 26, 2007  |
| H1.0   |   | HVAC Basement Floor Plan                                           |   | January 26, 2007  |
| H1.1D  |   | HVAC Ground Floor Plan Demolition                                  |   | January 26, 2007  |
| H1.1   |   | HVAC Ground Floor Plan                                             |   | February 23, 2007 |
| H1.2D  |   | HVAC Typical Floor Plan Demolition                                 |   | January 26, 2007  |
| H1.2   |   | HVAC Typical Floor Plan                                            |   | February 23, 2007 |
| H1.3D  |   | HVAC Tenth Floor Plan Demolition                                   |   | January 26, 2007  |
| H1.3   |   | HVAC Tenth Floor Plan                                              |   | February 23, 2007 |
| H1.4D  |   | HVAC Roof Plan Demolition                                          |   | January 26, 2007  |
| H1.4   |   | HVAC Roof Plan                                                     |   | February 23, 2007 |
| H2.1   |   | HVAC Part Plans                                                    |   | January 26, 2007  |
| H2.2   |   | HVAC 100 Tech Square First Floor Part Plan                         |   | January 26, 2007  |
| H2.3   |   | HVAC 100 Tech Square Penthouse Part Plan                           |   | January 26, 2007  |
|   |   |                                                               |   |              |
| E0.1   |   | Electrical Legend                                                  |   | February 23, 2007 |
| E1.0   |   | Electrical Basement Power Plan                                     |   | February 23, 2007 |
| E1.1   |   | Electrical First Floor Power Plan                                  |   | February 23, 2007 |
| E1.2   |   | Electrical 2nd thru 9th Floor Demo, New Lighting  & Power Plan |   | January 26, 2007  |
| E1.3   |   | Electrical 10th Floor Demolition & New Power  Plans            |   | January 26, 2007  |
| E1.4   |   | Electrical Penthouse Demo & New Power Plans                    |   | January 26, 2007  |
| E2.0   |   | Electrical Basement Demo & New Lighting Plans                  |   | February 23, 2007 |
| E2.1   |   | Electrical First Floor Demo & New Power Plans                  |   | February 23, 2007 |
| E2.2   |   | Electrical Building 100 Part Plans                                 |   | January 26, 2007  |
| E3.1   |   | Electrical Riser Diagram                                           |   | January 26, 2007  |
| E3.2   |   | Electrical Schedules                                               |   | February 23, 2007 |
|   |   |                                                               |   |              |
| 15300  |   | Fire Protection Specification                                      |   | January 5, 2007   |
| 15400  |   | Plumbing Specification                                             |   | January 5, 2007   |

 

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| 15500 |   | Heating, Ventilation, and Air Conditioning  Specification |   | February 23, 2007 |
|-------|--------|-----------------------------------------------------------|--------|-------------------|
| 16000 |   | Electrical Specification                                  |   | January 5, 2007   |
| 16700 |   | Fire Alarm Specification                                  |   | January 5, 2007   |

 

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**EXHIBIT D TO LEASE**

**ACKNOWLEDGMENT OFCOMMENCEMENT DATE**

This **ACKNOWLEDGMENT OFCOMMENCEMENT DATE** is made as of this           day of                           ,2007, between ARE-TECH SQUARE, LLC, a Delaware limited liability company (“**Landlord**”), and SIRTRIS PHARMACEUTICALS, a Delawarecorporation  (“**Tenant**”),and is attached to and made a part of the Lease dated as of March         ,2007 (the “**Lease**”), by and betweenLandlord and Tenant.  Any initiallycapitalized terms used but not defined herein shall have the meanings giventhem in the Lease.

Landlord and Tenant hereby acknowledge and agree, forall purposes of the Lease, that the Commencement Date of the Base Term of theLease is                         ,                          [, the “Rent Commencement Date [for Base Rent] [Operating Expenses] is                                 ,                    ]and the expiration date of the Base Term of the Lease shall be midnight on                             ,                    . In case of a conflict between the terms of the Lease and the terms of thisAcknowledgement of Commencement Date, this Acknowledgement of Commencement Dateshall control for all purposes.

IN WITNESS WHEREOF, Landlord and Tenant have executedthis ACKNOWLEDGMENT OF COMMENCEMENT DATE to be effective on the date firstabove written.

 
| ** ** |   | **TENANT:**                                                 |
|------------|--------|-------------------------------------------------------------|
| ** ** |   | ** **                                                  |
|       |   | SIRTRIS PHARMACEUTICALS, INC.,                              |
|       |   | a Delaware corporation                                      |
|       |   |                                                        |
|       |   | By:                                                         |   |   |
|       |   | Name:                                                       |
|       |   | Title:                                                      |
|       |   |                                                        |
|       |   |                                                        |
| ** ** |   | **LANDLORD**                                                |
| ** ** |   | ** **                                                  |
|       |   | ARE-TECH SQUARE, LLC, a Delaware limited liability  company |
|       |   |                                                        |
|       |   | By:                                                         | ARE-MA REGION NO. 31, LLC, a Delaware limited  liability  company, its Member |
|       |   |                                                        |   |
|       |   |                                                        | By: | ALEXANDRIA REAL ESTATE EQUITIES, L.P., |
|       |   |                                                        |   | a Delaware limited partnership, its Member |
|       |   |                                                        |   |   |
|       |   |                                                        |   | By: | ARE-QRS CORP., a Maryland corporation, |
|       |   |                                                        |   |   | its General Partner |
|       |   |                                                        |   |   |   |
|       |   |                                                        |   |   | By: |   |
|       |   |                                                        |   |   |   | Name: |
|       |   |                                                        |   |   |   | Title: |
|            |        |                                                             |  |  |  |  |  |  |

 

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**EXHIBIT E TO LEASE**

**Rules and Regulations**

1.             The sidewalk, entries, and driveways of the Projectshall not be obstructed by Tenant, or any Tenant Party, or used by them for anypurpose other than ingress and egress to and from the Premises.

2.             Tenant shall not place any objects, including antennas,outdoor furniture, etc., in the parking areas, landscaped areas or other areasoutside of its Premises, or on the roof of the Project.

3.             Except for animals assisting the disabled, no animalsshall be allowed in the offices, halls, or corridors in the Project.

4.             Tenant shall not disturb the occupants of the Project oradjoining buildings by the use of any radio or musical instrument or by themaking of loud or improper noises.

5.             If Tenant desires telegraphic, telephonic or otherelectric connections in the Premises, Landlord or its agent will direct theelectrician as to where and how the wires may be introduced; and, without suchdirection, no boring or cutting of wires will be permitted.  Any such installation or connection shall bemade at Tenant’s expense.

6.             Tenant shall not install or operate any steam or gasengine or boiler, or other mechanical apparatus in the Premises, except asspecifically approved in the Lease.  Theuse of oil, gas or inflammable liquids for heating, lighting or any otherpurpose is expressly prohibited. Explosives or other articles deemed extra hazardous shall not be broughtinto the Project.

7.             Parking any type of recreational vehicles isspecifically prohibited on or about the Project.  Except for the overnight parking of operativevehicles, no vehicle of any type shall be stored in the parking areas at anytime.  In the event that a vehicle isdisabled, it shall be removed within 48 hours. There shall be no “For Sale” or other advertising signs on or about anyparked vehicle.  All vehicles shall beparked in the designated parking areas in conformity with all signs and othermarkings.  All parking will be openparking, and no reserved parking, numbering or lettering of individual spaceswill be permitted except as specified by Landlord.

8.             Tenant shall maintain the Premises free from rodents,insects and other pests.

9.             Landlord reserves the right to exclude or expel from theProject any person who, in the judgment of Landlord, is intoxicated or underthe influence of liquor or drugs or who shall in any manner do any act inviolation of the Rules and Regulations of the Project.

10.           Tenant shall not cause anyunnecessary labor by reason of Tenant’s carelessness or indifference in the preservationof good order and cleanliness.  Landlordshall not be responsible to Tenant for any loss of property on the Premises,however occurring, or for any damage done to the effects of Tenant by thejanitors or any other employee or person.

11.           Tenant shall give Landlord promptnotice of any defects in the water, lawn sprinkler, sewage, gas pipes,electrical lights and fixtures, heating apparatus, or any other serviceequipment affecting the Premises.

12.           Tenant shall not permit storageoutside the Premises, including without limitation, outside storage of trucksand other vehicles, or dumping of waste or refuse or permit any harmfulmaterials to be placed in any drainage system or sanitary system in or aboutthe Premises.

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13.           All moveable trash receptaclesprovided by the trash disposal firm for the Premises must be kept in the trashenclosure areas, if any, provided for that purpose.

14.           No auction, public or private, willbe permitted on the Premises or the Project.

15.           No awnings shall be placed over thewindows in the Premises except with the prior written consent of Landlord.

16.           The Premises shall not be used forlodging, sleeping or cooking or for any immoral or illegal purposes or for anypurpose other than that specified in the Lease. No gaming devices shall be operated in the Premises.

17.           Tenant shall ascertain from Landlordthe maximum amount of electrical current which can safely be used in thePremises, taking into account the capacity of the electrical wiring in theProject and the Premises and the needs of other tenants, and shall not use morethan such safe capacity.  Landlord’sconsent to the installation of electric equipment shall not relieve Tenant fromthe obligation not to use more electricity than such safe capacity.

18.           Tenant assumes full responsibilityfor protecting the Premises from theft, robbery and pilferage.

19.           Tenant shall not install or operateon the Premises any machinery or mechanical devices of a nature not directlyrelated to Tenant’s ordinary use of the Premises and shall keep all suchmachinery free of vibration, noise and air waves which may be transmittedbeyond the Premises.

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**EXHIBIT F TO LEASE**

**TENANT’S PERSONALPROPERTY**

None.

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**EXHIBIT G TO LEASE**

**Replacement Sections2(a), 2(b), 2(c) and 3(a) of Work Letter for Available Space (per Section 39(b) of Lease)**

2.             **Tenant Improvements.**

(a)           **Tenant Improvements Defined.**  As used herein, “Tenant Improvements” shallmean all improvements to the Project of a fixed and permanent nature as shownon the TI Construction Drawings, as defined in Section 2(c) below.  Other than Landlord’s Work (as defined inSection 3(a) below, Landlord shall not have any obligation whatsoever withrespect to the finishing of the Available Space for Tenant’s use and occupancy.

(b)           **Tenant’s Space Plans.**  Tenant shall deliver to Landlord and the TIArchitect schematic drawings and outline specifications (the “TI DesignDrawings”) detailing Tenant’s requirements for the Tenant Improvements within10 business days of the date on which Tenant Exercises its ExpansionRight.  Not more than 10 days thereafter,Landlord shall deliver to Tenant the written objections, questions or commentsof Landlord and the TI Architect with regard to the TI Design Drawings.  Tenant shall cause the TI Design Drawings tobe revised to address such written comments and shall resubmit said drawings toLandlord for approval within 10 days thereafter.  Such process shall continue until Landlord hasapproved the TI Design Drawings.

(c)           **WorkingDrawings.**  Not later than 10business days following the approval of the TI Design Drawings, Landlord shallcause the TI Architect to prepare and deliver to Tenant for review and commentconstruction plans, specifications and drawings for the Tenant Improvements (“TIConstruction Drawings”), which TI Construction Drawings shall be preparedsubstantially in accordance with the TI Design Drawings.  Tenant shall be solely responsible forensuring that the TI Construction Drawings reflect Tenant’s requirements forthe Tenant Improvements.  Tenant shalldeliver its written comments on the TI Construction Drawings to Landlord notlater than 10 business days after Tenant’s receipt of the same; provided,however, that Tenant may not disapprove any matter that is consistent with theTI Design Drawings without submitting a Change Request.  Landlord and the TI Architect shall considerall such comments in good faith and shall, within 10 business days afterreceipt, notify Tenant how Landlord proposes to respond to such comments, butTenant’s review rights pursuant to the foregoing sentence shall not delay thedesign or construction schedule for the Tenant Improvements.  Any disputes in connection with such commentsshall be resolved in accordance with Section 2(d) hereof.  Provided that the design reflected in the TIConstruction Drawings is consistent with the TI Design Drawings, Tenant shallapprove the TI Construction Drawings submitted by Landlord, unless Tenantsubmits a Change Request.  Once approvedby Tenant, subject to the provisions of Section 4 below, Landlord shall notmaterially modify the TI Construction Drawings except as may be reasonablyrequired in connection with the issuance of the TI Permit (as defined in Section3(b) below).

(d)           **Approvaland Completion.**  Upon anydispute regarding the design of the Tenant Improvements, which is not settledwithin 10 business days after notice of such dispute is delivered by one partyto the other, Tenant may make the final decision regarding the design of theTenant Improvements, provided (i) Tenant acts reasonably and such finaldecision is either consistent with or a compromise between Landlord’s andTenant’s positions with respect to such dispute, (ii) that all costs andexpenses resulting from any such decision by Tenant shall be payable out of theTI Fund (as defined in Section 5(d) below), and (iii) Tenant’s decision willnot affect the base Building, structural components of the Building or anyBuilding systems.  Any changes to the TIConstruction Drawings following Landlord’s and Tenant’s approval of samerequested by Tenant shall be processed as provided in Section 4 hereof.

3.             **Performance ofLandlord’s Work.**

(a)           **Definitionof Landlord’s Work.**  As usedherein, “Landlord’s Work” shall mean the work of constructing the TenantImprovements.

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**EXHIBIT H TO LEASE**

**ROOFTOP EQUIPMENTLOCATION**

200 Technology Square

Roof Plan

****

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