Tenant’s Authorized Representative. Tenant designates, as Tenant’s authorized representative (“Tenant’s Authorized Representative”), Chris Hill as the individual authorized by Tenant to initial and sign all plans, drawings, change orders and approvals pursuant to this ES Work Letter. Landlord shall not be obligated to respond to or act upon any such item until such item has been initialed or signed or submitted in writing (as applicable) by Tenant’s Authorized Representative. Tenant may change Tenant’s Authorized Representative and/or name additional persons to serve as Tenant’s Authorized Representative (provided that Landlord may rely upon the authorization of any one of such persons) upon one (1) business day’s prior written notice to Landlord. Tenant agrees that Tenant’s Authorized Representative shall be reasonably available to meet and consult with Landlord’s Authorized Representative in person (in the vicinity of the Property) or by phone (at the election of Tenant’s Authorized Representative) as and when needed, upon reasonable prior notice by Landlord.

Tenant’s Proportionate Share. The parties hereby agree that the Building has been remeasured and now constitutes 126,124 rentable square feet. Accordingly, Tenant’s Proportionate Share of Building costs shall be 112,298/126,124=89%, and Tenant’s Proportionate Share of Project costs shall be 112,298/208,922=54%.

Tenant’s Obligations upon Surrender. At the expiration or earlier termination of the Lease Term, Tenant, at Tenant’s sole cost and expense, shall: # cause an Environmental Assessment of the Premises to be conducted in accordance with Section 15.3; # cause all Hazardous Materials to be removed from the Premises and disposed of in accordance with all Environmental Laws and as necessary to allow the Premises to be used for any purpose to the extent such Hazardous Materials were not disclosed in the Existing Condition Environmental Report (hereinafter defined); and # cause to be removed all containers installed or used by Tenant or Tenant’s Agents to store any Hazardous Materials on the Premises, and cause to be repaired any damage to the Premises caused by such removal.

Tenant shall be solely responsible for the payment of any and all taxes levied upon # personal property and trade fixtures located at the Premises and # any gross or net receipts of or sales by Tenant, and shall pay the same at least twenty (20) days prior to delinquency.

Cost of Tenant’s ES Fitout. Except for the ES Allowance (hereinafter defined), all of Tenant’s ES Fitout shall be performed at Tenant’s sole cost and expense, and shall be performed in accordance with the provisions of the Lease (including, without limitation, [Article 11]). Tenant shall pay to Landlord, as additional rent, within ten (10) days after demand therefor, any costs or expenses incurred by Landlord (which shall be reasonably based on Tenant's usage) for the use of elevators and/or hoisting in connection with the performance of Tenant’s ES Fitout.

Substantial Completion of Tenant’s ES Fitout. Tenant shall Substantially Complete (hereinafter defined) Tenant’s ES Fitout on or before the date that is twelve (12) months after the ES Commencement Date (the “Outside ES Completion Date”), provided that if Tenant is delayed in the performance of Tenant’s ES Fitout by reason of a Landlord Delay or other causes beyond Tenant’s reasonable control, the Outside ES Completion Date shall be extended by the period of time which Tenant is so delayed. For purposes hereof, Tenant’s ES Fitout shall be deemed “Substantially Complete” and “Substantial Completion” shall be deemed to have occurred if Tenant has substantially completed Tenant’s ES Fitout in accordance with the approved Final ES Construction Drawings and Tenant has delivered to Landlord a copy of # a certificate of substantial completion from Tenant’s architect for Tenant’s ES Fitout, and # a temporary or permanent certificate of occupancy for the Expansion Space from the City of Cambridge, Massachusetts; provided, however, if a temporary certificate of occupancy is issued with respect to the Expansion Space, then Tenant shall obtain a permanent certificate of occupancy for the Expansion Space within sixty (60) days after issuance of such temporary certificate of occupancy.

Tenant hereby appoints the following person(s) as Tenant’s representative (“Tenant’s Representative”)

Broker shall pay a part of such commission to Tenant’s Broker pursuant to a separate agreement between Landlord, Landlord’s Broker and Tenant’s Broker.

Tenant’s Initials: DLL

at the Landlord’s request, reimburse the Landlord for the cost of any repairs to the Premises necessitated by the Tenant’s or the Tenant’s guests or invitees misuse or neglect.