Document:

EX-10.15

 Exhibit 10.15 

INDEMNIFICATION AGREEMENT 

THIS AGREEMENT (the “Agreement”) is made and entered into as of
[                    ] between Arsanis, Inc., a Delaware corporation (the “Company,” which term shall include where appropriate, any Entity
(as hereinafter defined)), and [                    ] (“Indemnitee”). 

WHEREAS, it is essential to the Company that it be able to retain and attract as directors the most capable persons available; 

WHEREAS, increased corporate litigation has subjected directors to litigation risks and expenses, and the limitations on the availability of
directors’ and officers’ liability insurance has made it increasingly difficult for the Company to attract and retain such persons; 

WHEREAS, the Company desires to provide Indemnitee with specific contractual assurance of Indemnitee’s rights to indemnification against
litigation risks and expenses (regardless, among other things, of any amendment to or revocation of the Company’s Certificate of Incorporation or By-Laws, each as amended from time to time (the
“Charter Documents”), any change in the ownership of the Company or the composition of its Board of Directors) which indemnification is intended to be greater than that which is afforded by the Charter Documents; 

WHEREAS, in accordance with the authorization as provided by applicable law and the provisions of the certificate of incorporation and by-laws, the Company shall maintain a policy or policies of directors’ and officers’ liability insurance (“D & O Insurance”), covering certain liabilities which may be incurred by
its directors in the performance of their obligations to the Company; and 
 WHEREAS, in order to induce Indemnitee to serve as a director
of the Company, the Company has determined and agreed to enter into this Agreement with Indemnitee; 
 NOW, THEREFORE, in consideration of
Indemnitee’s service as a director, the parties hereto agree as follows: 
 1. Definitions. For purposes of this Agreement: 

(a) “Corporate Status” describes the status of a person who is serving or has served (i) as a director of the Company, including
as a member of any committee thereof, (ii) in any capacity with respect to any employee benefit plan of the Company, or (iii) as a director, partner, trustee, officer, employee, or agent of any other Entity (as defined below) at the
request of the Company. For purposes of subsection (iii) of this Section 1(a), a director of the Company who is serving or has served as a director, partner, trustee, officer, employee or agent of a Subsidiary (as defined below) shall be
deemed to be serving at the request of the Company. 
 (b) “Disinterested Director” means a director of the Company who is not and
was not a party to the Proceeding in respect of which indemnification is sought by Indemnitee. 

  
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 (c) “Entity” shall mean any corporation, partnership, limited liability company, joint
venture, trust, foundation, association, organization or other legal entity. 
 (d) “Expenses” shall mean all reasonable fees,
costs and expenses actually incurred in connection with any Proceeding (as defined below), including, without limitation, reasonable attorneys’ fees, disbursements and retainers, reasonable fees and disbursements of expert witnesses, private
investigators and professional advisors (including, without limitation, accountants and investment bankers), court costs, transcript costs, fees of experts, travel expenses, duplicating, printing and binding costs, telephone and fax transmission
charges, postage, delivery services, secretarial services and other reasonable disbursements and expenses. 
 (e) “Independent
Counsel” means a law firm, or a member of a law firm, that is experienced in matters of corporation law and neither presently is, nor in the past five years has been, retained to represent: (i) the Company or Indemnitee in any matter
material to either such party (other than with respect to matters concerning the Indemnitee under this Agreement, or of other indemnitees under similar indemnification agreements), or (ii) any other party to the Proceeding giving rise to a
claim for indemnification hereunder. Notwithstanding the foregoing, the term “Independent Counsel” shall not include any person who, under the applicable standards of professional conduct then prevailing, would have a conflict of interest
in representing either the Company or Indemnitee in an action to determine Indemnitee’s rights under this Agreement. The Company agrees to pay the reasonable fees of the Independent Counsel referred to above and to fully indemnify such counsel
against any and all Expenses and Liabilities (as defined below) arising out of or relating to this Agreement or its engagement pursuant hereto. 

(f) “Liabilities” shall mean judgments, damages, liabilities, losses, penalties, excise taxes, fines and amounts paid in settlement.

 (g) “Proceeding” shall mean any threatened, pending or completed claim, action, suit, arbitration, alternate dispute resolution
process, investigation, administrative hearing, appeal, or any other proceeding, whether civil, criminal, administrative, arbitrative or investigative, whether formal or informal, including a proceeding initiated by Indemnitee pursuant to
Section 10 of this Agreement to enforce Indemnitee’s rights hereunder, and shall include a Proceeding pending on or before the date of this Agreement. 

(h) “Subsidiary” shall mean any corporation, partnership, limited liability company, joint venture, trust or other Entity of which
the Company owns (either directly or through or together with another Subsidiary of the Company) either (i) a general partner, managing member or other similar interest or (ii) (A) more than 50% of the voting power of the voting capital
equity interests of such corporation, partnership, limited liability company, joint venture or other Entity, or (B) more than 50% of the outstanding voting capital stock or other voting equity interests of such corporation, partnership, limited
liability company, joint venture or other Entity. 

  
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 2. Agreement to Indemnify. 

(a) Proceedings Other Than Proceedings by or in the Right of the Company. Indemnitee shall be entitled to the rights of indemnification
provided in this Section 2(a) if, by reason of Indemnitee’s Corporate Status, Indemnitee is, or is threatened to be made, a party to or participant in any Proceeding other than a Proceeding by or in the right of the Company or a Proceeding
instituted by Indemnitee pursuant to Section 9 of this Agreement to enforce Indemnitee’s rights under this Agreement. Pursuant to this Section 2(a), Indemnitee shall be indemnified by the Company against all Expenses and Liabilities
incurred or paid by Indemnitee in connection with such Proceeding, if Indemnitee acted in good faith and in a manner Indemnitee reasonably believed to be in or not opposed to the best interests of the Company and, with respect to any criminal
Proceeding, had no reasonable cause to believe Indemnitee’s conduct was unlawful. 
 (b) Proceedings by or in the Right of the
Company. Indemnitee shall be entitled to the rights of indemnification provided in this Section 2(b) if, by reason of Indemnitee’s Corporate Status, Indemnitee is, or is threatened to be made, a party to or participant in any
Proceeding brought by or in the right of the Company. Pursuant to this Section 2(b), Indemnitee shall be indemnified by the Company against all Expenses incurred or paid by Indemnitee in connection with such Proceeding if Indemnitee acted in
good faith and in a manner Indemnitee reasonably believed to be in or not opposed to the best interests of the Company; provided, however, that, if applicable law so provides, no indemnification against such Expenses shall be made in
respect of any claim, issue or matter in such Proceeding as to which Indemnitee shall have been adjudged to be liable to the Company unless and to the extent that the Court of Chancery of the State of Delaware or other court of competent
jurisdiction shall determine that such indemnification may be made. 
 3. Indemnification for Expenses of a Party Who is Wholly or Partly
Successful. Notwithstanding any other provision of this Agreement, to the extent that Indemnitee is, by reason of Indemnitee’s Corporate Status, a party to and is successful, on the merits or otherwise, in any Proceeding, Indemnitee shall
be indemnified to the maximum extent permitted by applicable law against all Expenses and Liabilities incurred or paid by Indemnitee in connection therewith. If Indemnitee is not wholly successful in such Proceeding but is successful, on the merits
or otherwise, as to one or more but less than all claims, issues or matters in such Proceeding, the Company shall indemnify Indemnitee against all Expenses and Liabilities incurred or paid by Indemnitee in connection with each successfully resolved
claim, issue or matter. For purposes of this Section and without limitation, the termination of any claim, issue or matter in such a Proceeding by dismissal, with or without prejudice, shall be deemed to be a successful result as to such claim,
issue or matter. 
 4. Additional Indemnity. In addition to, and without regard to any limitations on, the indemnification provided
for in Section 2, the Company shall and hereby does indemnify and hold harmless Indemnitee against all Expenses and Liabilities incurred or paid by Indemnitee or on Indemnitee’s behalf if, by reason of Indemnitee’s Corporate Status,
Indemnitee is, or is threatened to be made, a party to or participant in any Proceeding (including a Proceeding by or in the right of the Company), including, without limitation, all liability arising out of the negligence or active or passive
wrongdoing of Indemnitee. The only limitation that shall exist upon the Company’s obligations pursuant to this Agreement shall be that the Company shall not be obligated to make any payment to Indemnitee that is finally determined (under the
procedures, and subject to the presumptions, set forth in Section 8 hereof) to be unlawful under applicable law. 

  
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 5. Contribution in the Event of Joint Liability. 

(a) Whether or not the indemnification provided in Sections 2 or 4 hereof is available, in respect of any threatened, pending or completed
action, suit or proceeding in which the Company is jointly liable with Indemnitee (or would be if joined in such action, suit or proceeding), the Company shall pay, in the first instance, the entire amount of any judgment or settlement of such
action, suit or proceeding without requiring Indemnitee to contribute to such payment and the Company hereby waives and relinquishes any right of contribution it may have against Indemnitee. The Company shall not enter into any settlement of any
action, suit or proceeding in which the Company is jointly liable with Indemnitee (or would be if joined in such action, suit or proceeding) unless such settlement provides for a full and final release of all claims asserted against Indemnitee. 

(b) Without diminishing or impairing the obligations of the Company set forth in the preceding subparagraph, if, for any reason, Indemnitee
shall elect or be required to pay all or any portion of any judgment or settlement in any threatened, pending or completed action, suit or proceeding in which the Company is jointly liable with Indemnitee (or would be if joined in such action, suit
or proceeding), the Company shall contribute to the amount of Expenses and Liabilities incurred and paid or payable by Indemnitee in proportion to the relative benefits received by the Company and all officers, directors or employees of the Company
other than Indemnitee who are jointly liable with Indemnitee (or would be if joined in such action, suit or proceeding), on the one hand, and Indemnitee, on the other hand, from the transaction from which such action, suit or proceeding arose;
provided, however, that the proportion determined on the basis of relative benefit may, to the extent necessary to conform to law, be further adjusted by reference to the relative fault of the Company and all officers, directors or
employees of the Company other than Indemnitee who are jointly liable with Indemnitee (or would be if joined in such action, suit or proceeding), on the one hand, and Indemnitee, on the other hand, in connection with the events that resulted in such
Expenses or Liabilities, as well as any other equitable considerations which the law may require to be considered. The relative fault of the Company and all officers, directors or employees of the Company other than Indemnitee who are jointly liable
with Indemnitee (or would be if joined in such action, suit or proceeding), on the one hand, and Indemnitee, on the other hand, shall be determined by reference to, among other things, the degree to which their actions were motivated by intent to
gain personal profit or advantage, the degree to which their liability is primary or secondary, and the degree to which their conduct is active or passive. 

(c) The Company hereby agrees to fully indemnify and hold Indemnitee harmless from any claims of contribution which may be brought by officers,
directors or employees of the Company other than Indemnitee who may be jointly liable with Indemnitee. 
 6. Indemnification for Expenses
of a Witness or in Response to a Subpoena. Notwithstanding any other provision of this Agreement, to the extent that Indemnitee, is by reason of Indemnitee’s Corporate Status, a witness in any Proceeding to which Indemnitee is not a party,
or receives a subpoena in any Proceeding to which Indemnitee is not a party, Indemnitee shall be indemnified against all Expenses paid or incurred by Indemnitee in connection therewith and in the manner set forth in this Agreement. 

  
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 7. Advancement of Expenses. Notwithstanding any other provision of this Agreement, the
Company shall advance all Expenses incurred by or on behalf of Indemnitee in connection with any Proceeding by reason of Indemnitee’s Corporate Status within thirty (30) days after the receipt by the Company of a statement or statements
from Indemnitee requesting such advance or advances from time to time, whether prior to or after final disposition of such Proceeding. Such statement or statements shall reasonably evidence the Expenses incurred by Indemnitee and shall include or be
preceded or accompanied by an undertaking by or on behalf of Indemnitee to repay any Expenses advanced if it shall ultimately be determined by a final, non-appealable order of the Court of Chancery of the
State of Delaware or other court of competent jurisdiction that Indemnitee is not entitled to be indemnified against such Expenses. Any advances and undertakings to repay pursuant to this Section 7 shall be unsecured and interest free and made
without regard to Indemnitee’s financial ability to repay such Expenses. 
 8. Procedures and Presumptions for Determination of
Entitlement to Indemnification. It is the intent of this Agreement to secure for Indemnitee rights of indemnity that are at least as favorable as may be permitted under applicable law and public policy of the State of Delaware. Accordingly, the
parties agree that the following procedures and presumptions shall apply in the event of any question as to whether Indemnitee is entitled to indemnification under this Agreement: 

(a) To obtain indemnification (including, but not limited to, the advancement of Expenses and contribution by the Company) under this
Agreement, Indemnitee shall submit to the Company a written request, including therein or therewith such documentation and information as is reasonably available to Indemnitee and is reasonably necessary to determine whether and to what extent
Indemnitee is entitled to indemnification. 
 (b) Upon written request by Indemnitee for indemnification pursuant to the first sentence of
Section 8(a) hereof, a determination, if required by applicable law, with respect to Indemnitee’s entitlement thereto shall be made in the specific case by one of the following three methods, which shall be at the sole election of
Indemnitee: (1) by a majority vote of the Disinterested Directors, even though less than a quorum, or (2) by Independent Counsel in a written opinion, or (3) by the stockholders of the Company. 

(c) If the determination of entitlement to indemnification is to be made by Independent Counsel pursuant to Section 8(b) hereof, the
Independent Counsel shall be selected as provided in this Section 8(c). The Independent Counsel shall be selected by Indemnitee (unless Indemnitee shall request that such selection be made by the Board of Directors). Indemnitee or the Company,
as the case may be, may, within 10 days after such written notice of selection shall have been given, deliver to the Company or to Indemnitee, as the case may be, a written objection to such selection; provided, however, that such
objection may be asserted only on the ground that the Independent Counsel so selected does not meet the requirements of “Independent Counsel” as defined in Section 1 of this Agreement, and the objection shall set forth with
particularity the factual basis of such assertion. Absent a proper and timely objection, the person so selected shall act as Independent Counsel. If a written objection is made and substantiated, the Independent Counsel selected may not serve as
Independent Counsel unless and until such objection is withdrawn or a court has determined that such objection is without merit. If, within 20 days after submission by Indemnitee of a written request for indemnification

  
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pursuant to Section 8(a) hereof, no Independent Counsel shall have been selected and not objected to, either the Company or Indemnitee may petition the Court of Chancery of the State of
Delaware or other court of competent jurisdiction for resolution of any objection which shall have been made by the Company or Indemnitee to the other’s selection of Independent Counsel and/or for the appointment as Independent Counsel of a
person selected by the court or by such other person as the court shall designate, and the person with respect to whom all objections are so resolved or the person so appointed shall act as Independent Counsel under Section 8(b) hereof. The
Company shall pay any and all reasonable fees and expenses of Independent Counsel incurred by such Independent Counsel in connection with acting pursuant to Section 8(b) hereof, and the Company shall pay all reasonable fees and expenses
incident to the procedures of this Section 8(c), regardless of the manner in which such Independent Counsel was selected or appointed. 

(d) In making a determination with respect to entitlement to indemnification hereunder, the person or persons or entity making such
determination shall presume that Indemnitee is entitled to indemnification under this Agreement if Indemnitee has submitted a request for indemnification in accordance with Section 8(a) of this Agreement. Anyone seeking to overcome this
presumption shall have the burden of proof and the burden of persuasion, by clear and convincing evidence. 
 (e) Indemnitee shall be deemed
to have acted in good faith for purposes of indemnification under this Agreement if Indemnitee’s actions are based on the records or books of account of the Company, including financial statements, or on information supplied to Indemnitee by
the directors, officers, agents or employees of the Company in the course of their duties, or on the advice of legal counsel for the Company or on information or records given or reports made to the Company by an independent certified public
accountant or by an appraiser or other expert selected by the Company. In addition, the knowledge and/or actions, or failure to act, of any director, officer, agent or employee of the Company shall not be imputed to Indemnitee for purposes of
determining the right to indemnification under this Agreement. Whether or not the foregoing provisions of this Section 8(e) are satisfied, it shall in any event be presumed that Indemnitee has at all times acted in good faith and in a manner
Indemnitee reasonably believed to be in or not opposed to the best interests of the Company. Anyone seeking to overcome this presumption shall have the burden of proof and the burden of persuasion, by clear and convincing evidence. 

(f) If the person, persons or entity empowered or selected under Section 8 to determine whether Indemnitee is entitled to indemnification
shall not have made a determination within forty-five (45) days after receipt by the Company of the request therefor, the requisite determination of entitlement to indemnification shall be deemed to have been made and Indemnitee shall be
entitled to such indemnification, absent (i) a misstatement by Indemnitee of a material fact, or an omission of a material fact necessary to make Indemnitee’s statement not materially misleading, in connection with the request for
indemnification, or (ii) a prohibition of such indemnification under applicable law; provided, however, that such forty-five day period may be extended for a reasonable time, not to exceed an additional fifteen (15) days, if
the person, persons or entity making the determination with respect to entitlement to indemnification in good faith requires such additional time for the obtaining or evaluating documentation and/or information relating thereto; and provided,
further, that the foregoing provisions of this 

  
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Section 8(f) shall not apply if the determination of entitlement to indemnification is to be made by the stockholders of the Company pursuant to Section 8(b) of this Agreement and if
(A) within fifteen (15) days after receipt by the Company of the request for such determination the Board of Directors or the Disinterested Directors, if appropriate, resolve to submit such determination to the stockholders for their
consideration at an annual meeting thereof to be held within seventy five (75) days after such receipt and such determination is made thereat, or (B) a special meeting of stockholders is called within fifteen (15) days after such
receipt for the purpose of making such determination, such meeting is held for such purpose within sixty (60) days after having been so called and such determination is made thereat. 

(g) Indemnitee shall cooperate with the person, persons or entity making such determination with respect to Indemnitee’s entitlement to
indemnification, including providing to such person, persons or entity upon reasonable advance request any documentation or information which is not privileged or otherwise protected from disclosure and which is reasonably available to Indemnitee
and reasonably necessary to such determination. Any Independent Counsel, member of the Board of Directors, or stockholder of the Company shall act reasonably and in good faith in making a determination under the Agreement of the Indemnitee’s
entitlement to indemnification. Any costs or expenses (including attorneys’ fees and disbursements) incurred by Indemnitee in so cooperating with the person, persons or entity making such determination shall be borne by the Company
(irrespective of the determination as to Indemnitee’s entitlement to indemnification) and the Company hereby indemnifies and agrees to hold Indemnitee harmless therefrom. 

(h) The Company acknowledges that a settlement or other disposition short of final judgment may be successful if it permits a party to avoid
expense, delay, distraction, disruption and uncertainty. In the event that any action, claim or proceeding to which Indemnitee is a party is resolved in any manner other than by adverse judgment against Indemnitee (including, without limitation,
settlement of such action, claim or proceeding with or without payment of money or other consideration) it shall be presumed that Indemnitee has been successful on the merits or otherwise in such action, suit or proceeding. Anyone seeking to
overcome this presumption shall have the burden of proof and the burden of persuasion, by clear and convincing evidence. 
 9. Remedies of
Indemnitee. 
 (a) In the event that (i) a determination is made pursuant to Section 8 of this Agreement that Indemnitee is not
entitled to indemnification under this Agreement, (ii) advancement of Expenses is not timely made pursuant to Section 7 of this Agreement, (iii) no determination of entitlement to indemnification shall have been timely made pursuant
to Section 8(b) of this Agreement after receipt by the Company of the request for indemnification, or (iv) payment of indemnification is not made within thirty (30) days after a determination has been made that Indemnitee is entitled
to indemnification or such determination is deemed to have been made pursuant to Section 8 of this Agreement, Indemnitee shall be entitled to an adjudication in the Chancery Court of the State of Delaware, or in any other court of competent
jurisdiction, of Indemnitee’s entitlement to such indemnification. The Company shall not oppose Indemnitee’s right to seek any such adjudication. 

  
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 (b) In the event that a determination shall have been made pursuant to Section 8(b) of this
Agreement that Indemnitee is not entitled to indemnification, any judicial proceeding commenced pursuant to this Section 9 shall be conducted in all respects as a de novo trial, on the merits and Indemnitee shall not be prejudiced by
reason of that adverse determination under Section 8(b). 
 (c) If a determination shall have been made pursuant to Section 8(b) of
this Agreement that Indemnitee is entitled to indemnification, the Company shall be bound by such determination in any judicial proceeding commenced pursuant to this Section 9, absent a prohibition of such indemnification under applicable law.

 (d) In the event that Indemnitee, pursuant to this Section 9, seeks a judicial adjudication of Indemnitee’s rights under, or to
recover damages for breach of, this Agreement, or to recover under any directors’ and officers’ liability insurance policies maintained by the Company, the Company shall pay on Indemnitee’s behalf, in advance, any and all Expenses
paid or incurred by him in such judicial adjudication, regardless of whether Indemnitee ultimately is determined to be entitled to such indemnification, advancement of expenses or insurance recovery. The Company shall, within thirty (30) days
after receipt by the Company of a written request therefor from Indemnitee, advance such Expenses to Indemnitee pursuant to comparable procedures as those set forth in Section 7 with respect to advancement of Expenses therein. 

(e) The Company shall be precluded from asserting in any judicial proceeding commenced pursuant to this Section 9 that the procedures and
presumptions of this Agreement are not valid, binding and enforceable and shall stipulate in any such court that the Company is bound by all the provisions of this Agreement. 

10. Non-Exclusivity; Survival of Rights; Insurance; Subrogation, Primacy of
Indemnification. 
 (a) The rights of indemnification as provided by this Agreement shall not be deemed exclusive of any other rights to
which Indemnitee may at any time be entitled under applicable law, the Charter Documents, a vote of stockholders or a resolution of directors, or otherwise. The Company shall not adopt any amendment to the Charter Documents the effect of which would
be to deny, diminish or encumber the Indemnitee’s rights to identification pursuant to this Agreement, the Charter Documents or applicable law prior to such amendment, alteration or repeal. To the extent that a change in applicable law, whether
by statute or judicial decision, permits greater indemnification than would be afforded currently under the Charter Documents and this Agreement, Indemnitee shall enjoy by this Agreement the greater benefits so afforded by such change. No right or
remedy herein conferred is intended to be exclusive of any other right or remedy, and every other right and remedy shall be cumulative and in addition to every other right and remedy given hereunder or now or hereafter existing at law or in equity
or otherwise. The assertion or employment of any right or remedy hereunder, or otherwise, shall not prevent the concurrent assertion or employment of any other right or remedy. 

(b) The Indemnitee shall be covered by the D & O Insurance and any other insurance policy or policies providing liability insurance
for directors, officers, employees, or agents or fiduciaries of the Company or of any other corporation, partnership, joint venture, trust, 

  
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employee benefit plan or other enterprise which such person serves at the request of the Company, and Indemnitee shall be covered by such policy or policies in accordance with its or their terms
to the maximum extent of the coverage available for any such director, officer, employee or agent under such policy or policies. 
 (c) In
the event of any payment under this Agreement, the Company shall be subrogated to the extent of such payment to all of the rights of recovery of Indemnitee, who shall execute all papers required and take all action necessary to secure such rights,
including execution of such documents as are necessary to enable the Company to bring suit to enforce such rights. 
 (d) The Company shall
not be liable under this Agreement to make any payment of amounts otherwise indemnifiable hereunder if and to the extent that Indemnitee has otherwise actually received such payment under any insurance policy, contract, agreement or otherwise. 

11. Exception to Right of Indemnification. Notwithstanding any other provision of this Agreement, Indemnitee shall not be entitled to
indemnification under this Agreement with respect to any Proceeding brought by Indemnitee, or any claim therein, unless (a) the bringing of such Proceeding or making of such claim shall have been approved by the Board of Directors of the
Company or (b) such Proceeding is being brought by the Indemnitee to assert, interpret or enforce Indemnitee’s rights under this Agreement. 

12. Duration of Agreement. All agreements and obligations of the Company contained herein shall continue during the period Indemnitee is
a director of the Company (or is or was serving at the request of the Company as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise) and shall continue thereafter so long as
Indemnitee shall be subject to any current or future Proceeding (or any proceeding commenced under Section 9) by reason of Indemnitee’s Corporate Status, whether or not Indemnitee is acting or serving in any such capacity at the time any
liability or expense is incurred for which indemnification can be provided under this Agreement. This Agreement shall be binding upon and inure to the benefit of and be enforceable by the parties hereto and their respective successors (including any
direct or indirect successor by purchase, merger, consolidation or otherwise to all or substantially all of the business or assets of the Company), assigns, spouses, heirs, executors and personal and legal representatives. This Agreement shall
continue in effect regardless of whether Indemnitee continues to serve as an officer or director of the Company or any other Entity at the Company’s request. 

13. Security. To the extent requested by the Indemnitee and approved by the Board of Directors of the Company, the Company may at any
time and from time to time provide security to the Indemnitee for the Company’s obligations hereunder through an irrevocable bank line of credit, funded trust or other collateral. Any such security, once provided to the Indemnitee, may not be
revoked or released without the prior written consent of the Indemnitee. 

  
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 14. Enforcement. 

(a) The Company expressly confirms and agrees that it has entered into this Agreement and assumed the obligations imposed on it hereby in order
to induce Indemnitee to serve as a director of the Company, and the Company acknowledges that Indemnitee is relying upon this Agreement in serving as a director of the Company. 

(b) This Agreement constitutes the entire agreement between the parties hereto with respect to the subject matter hereof and supersedes all
prior agreements and understandings, oral, written and implied, between the parties hereto with respect to the subject matter hereof. 
 15.
Fees and Expenses: During the term of the Indemnitee’s service as a director, the Company shall promptly reimburse the Indemnitee for all reasonable
out-of-pocket expenses incurred by him in connection with Indemnitee’s service as a director or member of any board committee or otherwise in connection with the
Company’s conduct of business. 
 16. Severability. If any provision or provisions of this Agreement shall be held by a court of
competent jurisdiction to be invalid, void, illegal or otherwise unenforceable for any reason whatsoever: (a) the validity, legality and enforceability of the remaining provisions of this Agreement (including without limitation, each portion of
any section of this Agreement containing any such provision held to be invalid, illegal or unenforceable, that is not itself invalid, illegal or unenforceable) shall not in any way be affected or impaired thereby and shall remain enforceable to the
fullest extent permitted by applicable law; and (b) to the fullest extent possible, the provisions of this Agreement (including, without limitation, each portion of any section of this Agreement containing any such provision held to be invalid,
illegal or unenforceable, that is not itself invalid, illegal or unenforceable) shall be construed so as to give effect to the intent manifested thereby. 

17. Modification and Waiver. Except as provided by Section 10(a) with respect to changes in applicable law that broaden the rights
of Indemnitee to be indemnified by the Company, no supplement, modification, termination or amendment of this Agreement shall be binding unless executed in writing by both of the parties hereto. No waiver of any of the provisions of this Agreement
shall be deemed or shall constitute a waiver of any other provisions hereof (whether or not similar) nor shall such waiver constitute a continuing waiver. 

18. Notice By Indemnitee. Indemnitee agrees promptly to notify the Company in writing upon being served with any summons, citation,
subpoena, complaint, indictment, information or other document relating to any Proceeding or matter which may be subject to indemnification covered hereunder. The failure to so notify the Company shall not relieve the Company of any obligation which
it may have to the Indemnitee under this Agreement or otherwise unless and only to the extent that such failure or delay materially prejudices the Company. 

19. Notices. All notices, requests, demands and other communications hereunder shall be in writing and shall be deemed to have been duly
given if (i) delivered by hand and receipted for by the party to whom said notice or other communication shall have been directed, or (ii) mailed by certified or registered mail with postage prepaid, on the second business day after the
date on which it is so mailed: 

  
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 (a) If to Indemnitee, to the address set forth below Indemnitee’s signature hereto. 

(b) If to the Company, to: 

Arsanis, Inc. 
 890 Winter
Street, Suite 230 
 Waltham, MA 02451 

Attn. President 
 with a copy
to: 
 [                    ] 

Email: [                    ] 

or to such other address as may have been furnished to Indemnitee by the Company or to the Company by Indemnitee, as the case may be. 

20. Identical Counterparts. This Agreement may be executed in one or more counterparts, each of which shall for all purposes be deemed
to be an original but all of which together shall constitute one and the same Agreement. Only one such counterpart signed by the party against whom enforceability is sought needs to be produced to evidence the existence of this Agreement. 

21. Headings. The headings of the paragraphs of this Agreement are inserted for convenience only and shall not be deemed to constitute
part of this Agreement or to affect the construction thereof. 
 22. Governing Law. The parties agree that this Agreement shall be
governed by, and construed and enforced in accordance with, the laws of the State of Delaware without application of the conflict of laws principles thereof. 

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

			
	ARSANIS, INC.
		
	By:	 	
                     
                               

	Name:
	Title:
	
	INDEMNITEE
	
	  

	Name:
	Address:

  
 -12-EX-10.16

 Exhibit 10.16 

EXECUTION COPY 
 LEASE

 LANDLORD: 
 WALTHAM
WINTER STREET 890 LP 
 TENANT: 

ARSANIS, INC. 
 Lease Dated:
October 30, 2015 

 ARTICLE I 

DEMISING CLAUSE AND DEFINED TERMS 
 1.1
Demising Clause. 
 This lease (this “Lease”) is made and entered into by and between the Landlord and the
Tenant, as defined below, as of the date set forth above. In consideration of the mutual covenants made herein, Landlord hereby leases to Tenant, and Tenant hereby leases from Landlord, the Premises as, defined below, on all of the terms and
conditions set forth herein. 
 1.2 Defined Terms. 

The terms listed below shall have the following meanings throughout this Lease: 

 

			
	LANDLORD:	  	Waltham Winter Street 890 LP, a
		  	Delaware limited partnership
		
	LANDLORD’S ORIGINAL ADDRESS:	  	c/o Clarion Partners, LLC
		  	101 Arch Street
		  	Boston, Massachusetts 02110
		
	TENANT:	  	Arsanis, Inc., a
		  	Delaware corporation
		
	TENANT’S ORIGINAL ADDRESS:	  	7 Lucent Drive
		  	Lebanon, New Hampshire 03766
		
	BUILDING:	  	The building located at 890 Winter Street, Waltham, Massachusetts, and located on the parcel of land (the “Lot”) described in Exhibit A.
		
	PROPERTY:	  	The Building and the Lot.
		
	TENANT’S SPACE:	  	7,814 rentable square feet (“RSF”) on the second (2nd) floor of the Building, as shown on Exhibit B.
		
	COMMENCEMENT DATE:	  	November 1, 2015.
		
	RENT COMMENCEMENT DATE:	  	February 1, 2016 (subject to extension
		  	pursuant to Section 2.6).
		
	TERM:	  	The term commencing on the Commencement Date and ending on the date which is three (3) years and three (3) months following the Commencement

  
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		  	Date.	  	
			
	FIXED RENT:	  	Per Annum	  	Per Month
			
	Commencing on the Rent Commencement Date through the last day immediately preceding the first anniversary of the Rent Commencement Date:	  	$300,839.00	  	$25,069.92
			
	Commencing on the first anniversary of the Rent Commencement Date through the last day immediately preceding the second anniversary of the Rent Commencement Date:	  	$308,653.00	  	$25,721.08
			
	Commencing on the second anniversary of the Rent Commencement Date through the last day of the Term:	  	$316,467.00	  	$26,372.25
		
	TENANT’S OPERATING EXPENSE BASE:	  	Tenant’s Proportionate Share of the total Operating Expenses for the Property incurred during calendar year 2016 (January 1, 2016 through December 31, 2016).
		
	TENANT’S TAX BASE:	  	Tenant’s Proportionate Share of the fiscal year 2016 Real Estate Taxes for the Property (July 1, 2015 through June 30, 2016), as adjusted by the results of any abatement, reassessment or litigation.
		
	TOTAL RENTABLE FLOOR AREA OF THE BUILDING:	  	173,070 rentable square feet.
		
	TENANT’S PROPORTIONATE SHARE:	  	Tenant’s Proportionate Share is based on a fraction, the total rentable square feet of the Building as the denominator (173,070 sq. ft.) and the total rentable square feet of the Premises as the numerator (7,814 sq.
ft.). Tenant’s Proportionate Share is four and fifty-one one hundredths percent (4.51%).
		
	PERMITTED USES:	  	General office use and uses ancillary thereto, and for no other purpose.
		
	SECURITY DEPOSIT:	  	See Section 8.17

  
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	BROKER:	  	Transwestern/RBJ and Jones Lang LaSalle (collectively, the “Broker”)

 1.3 Exhibits. 

There are incorporated as a part of this Lease: 
  

					
	EXHIBIT A	  	-  	  	Property Description
	EXHIBIT B	  	-  	  	Floor Plan
	EXHIBIT C	  	-  	  	Reserved
	EXHIBIT D	  	-  	  	Landlord’s Services
	EXHIBIT E	  	-  	  	Rules and Regulations
	EXHIBIT F	  	-  	  	Insurance Requirements

 1.4 Table of Contents 
  

							
	 ARTICLE I
	  			
			
		 	 DEMISING CLAUSE AND DEFINED TERMS
	  	 	1	 
	 1.1
	 	 Demising Clause
	  	 	1	 
	 1.2
	 	 Defined Terms
	  	 	1	 
	 1.3
	 	 Exhibits
	  	 	3	 
	 1.4
	 	 Table of Contents
	  	 	3	 
		
	 ARTICLE II
	  			
			
		 	 PREMISES, TERM AND RENT
	  	 	1	 
	 2.1
	 	 The Premises
	  	 	1	 
	 2.2
	 	 Parking
	  	 	1	 
	 2.3
	 	 Rights to Use Common Facilities
	  	 	1	 
	 2.4
	 	 Landlord’s Reservation
	  	 	1	 
	 2.5
	 	 Habendum: Commencement Date
	  	 	2	 
	 2.6
	 	 Monthly Fixed Rent Payments
	  	 	3	 
	 2.7
	 	 Adjustments for Operating Expenses
	  	 	3	 
	 2.8
	 	 Adjustments for Real Estate Taxes
	  	 	6	 
	 2.9
	 	 Electricity Charge
	  	 	7	 
	 2.10
	 	 Due Date of Additional Payments; No Offsets
	  	 	8	 
	 2.11
	 	 Late Payment of Rent
	  	 	8	 
	 2.12
	 	 Renewal Option
	  	 	8	 

  
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	 ARTICLE III
	  			
			
		 	 CONSTRUCTION
	  	 	10	 
	 3.1
	 	 Premises As Is
	  	 	10	 
	 3.2
	 	 Landlord’s Work
	  	 	10	 
	 3.3
	 	 General Provisions Applicable to Construction
	  	 	10	 
	 3.4
	 	 Liens
	  	 	10	 
		
	 ARTICLE IV
	  			
			
		 	 LANDLORD’S COVENANTS; INTERRUPTIONS AND DELAYS
	  	 	10	 
	 4.1
	 	 Services Furnished by Landlord
	  	 	10	 
	 4.2
	 	 Additional Services Available to Tenant
	  	 	11	 
	 4.3
	 	 Roof, Exterior Wall, Floor Slab and Common Facility Repair
	  	 	11	 
	 4.4
	 	 Quiet Enjoyment
	  	 	11	 
	 4.5
	 	 Interruptions and Delays in Service and Repairs, etc.
	  	 	11	 
	 4.6
	 	 Payment of Legal Expenses
	  	 	12	 
	 4.7
	 	 Landlord to Maintain Insurance; Waiver of Subrogation
	  	 	12	 
		
	 ARTICLE V
	  			
			
		 	 TENANT’S COVENANTS
	  	 	13	 
	 5.1
	 	 Payments
	  	 	13	 
	 5.2
	 	 Repair and Yield Up
	  	 	13	 
	 5.3
	 	 Use
	  	 	14	 
	 5.4
	 	 Obstructions; Items Visible from Exterior; Rules and Regulations; Signs
	  	 	14	 
	 5.5
	 	 Safety Appliances; Hazardous Materials
	  	 	14	 
	 5.6
	 	 Assignment; Sublease
	  	 	15	 
	 5.7
	 	 Indemnity; Insurance; Waiver of Subrogation
	  	 	17	 
	 5.8
	 	 Personal Property at Tenant’s Risk
	  	 	20	 
	 5.9
	 	 Right of Entry
	  	 	21	 
	 5.10
	 	 Floor Load; Prevention of Vibration and Noise
	  	 	21	 
	 5.11
	 	 Personal Property Taxes
	  	 	21	 
	 5.12
	 	 Payment of Legal Expenses
	  	 	21	 
	 5.13
	 	 Compliance with Insurance Regulations
	  	 	21	 
		
	 ARTICLE VI
	  			
			
		 	 CASUALTY AND TAKING
	  	 	22	 
	 6.1
	 	 Termination or Restoration; Rent Adjustment
	  	 	22	 
	 6.2
	 	 Eminent Domain Award
	  	 	23	 
	 6.3
	 	 Temporary Taking
	  	 	23	 
		
	 ARTICLE VII
	  			
			
		 	 DEFAULT
	  	 	23	 
	 7.1
	 	 Events of Default
	  	 	23	 
	 7.2
	 	 Landlord’s Rights and Tenant’s Obligations after Termination
	  	 	24	 

  
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	 ARTICLE VIII
	  			
			
		 	 MISCELLANEOUS
	  	 	25	 
	 8.1
	 	 Notice of Lease; Consent and Approval; Notices; Bind and Inure
	  	 	25	 
	 8.2
	 	 Landlord’s Failure to Enforce
	  	 	26	 
	 8.3
	 	 Acceptance of Partial Payments of Rent; Delivery of Keys
	  	 	26	 
	 8.4
	 	 Cumulative Remedies
	  	 	26	 
	 8.5
	 	 Partial Invalidity
	  	 	26	 
	 8.6
	 	 Self-Help
	  	 	27	 
	 8.7
	 	 Estoppel Certificate
	  	 	27	 
	 8.8
	 	 Waiver of Subrogation
	  	 	27	 
	 8.9
	 	 All Agreements Contained; Independent Covenants; Construction
	  	 	28	 
	 8.10
	 	 Brokerage
	  	 	28	 
	 8.11
	 	 Submission Not an Option
	  	 	28	 
	 8.12
	 	 Applicable Law
	  	 	28	 
	 8.13
	 	 Waiver of Jury Trial
	  	 	28	 
	 8.14
	 	 Access and Security
	  	 	28	 
	 8.15
	 	 Holdover
	  	 	29	 
	 8.16
	 	 Limitation on Liability
	  	 	29	 
	 8.17
	 	 Security Deposit [AMOUNT UNDER REVIEW]
	  	 	29	 
	 8.18
	 	 Representations
	  	 	30	 
		
	 ARTICLE IX
	  			
			
		 	 RIGHTS OF PARTIES HOLDING PRIOR INTERESTS
	  	 	30	 
	 9.1
	 	 Lease Subordinate
	  	 	30	 
	 9.2
	 	 Rights of Holder of Mortgage to Notice of Defaults by Landlord and to Cure
	  			
		 	 Same
	  	 	31	 

  
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 ARTICLE II 

PREMISES, TERM AND RENT 
 2.1 The
Premises 
 Landlord hereby leases to Tenant and Tenant hereby hires from Landlord Tenant’s Space in the Building, excluding
exterior faces of exterior walls, the common stairways and stairwells, elevators and elevator shafts, the roof, storage areas, fan rooms, electric and telephone closets, janitor closets, freight elevator vestibules, and pipes, ducts, conduits, wires
and appurtenant fixtures serving exclusively or in common other parts of the Building, and if Tenant’s Space includes less than the entire rentable area of any floor, excluding the common corridors, elevator lobbies and toilets located on such
floor. Tenant’s Space with such exclusions is hereinafter referred to as the “Premises.” 
 2.2 Parking 

Tenant and its employees and visitors shall be permitted to use twenty six (26) parking spaces in the parking areas on a non-exclusive basis in common with other Building tenants on the Lot, without charge, including two (2) non-exclusive spaces in the parking areas beneath the Building.
Tenant shall not sublet, assign or otherwise transfer its right to use parking spaces in the garage beneath the Building without the prior written consent of Landlord except in connection with a sublease or assignment permitted under this Lease
(including a sublease or assignment to a Tenant Affiliate (as defined in Section 5.6 below)). 
 2.3 Rights to Use Common Facilities 

Tenant shall have, as appurtenant to the Premises, rights to use in common with others, subject to reasonable rules of general applicability to
tenants of the Building from time to time made by Landlord of which Tenant is given notice: (a) the common lobbies, corridors, stairways, elevators and the pipes, ducts, conduits, wires and appurtenant meters and equipment serving the Premises,
(b) common walkways and driveways necessary for access to the Building and the loading area in the rear of the Building, (c) to the extent made available for the general use of tenants and occupants of the Building, the Building conference
room, café, fitness center, and other common areas of the Building or the office park in which the Building is located, and (d) if the Premises include less than the entire rentable area of any floor, the common toilets, corridors and
elevator lobbies of such floor. 
 2.4 Landlord’s Reservation 

Landlord reserves the right from time to time, without unreasonable interference with Tenant’s Permitted Use and upon reasonable prior
notice: (a) to install, use, maintain, repair, replace and relocate for service to the Premises and other parts of the Building, or either, pipes, ducts, conduits, wires and appurtenant fixtures, wherever located in the Premises or Building,
and (b) to alter or relocate any other common facility, provided that substitutions are substantially equivalent or better. Installations, replacements and relocations referred to in clause (a) above shall be located so far as practicable
in the central core area of the Building, above ceiling surfaces, below floor surfaces or within perimeter walls of the Premises. 

  
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 2.5 Habendum: Commencement Date 

Tenant shall have and hold the Premises for a period commencing on the Commencement Date and continuing for the Term unless sooner terminated
as provided in Section 6.1 or ARTICLE VII or extended pursuant to Section 2.12. Notwithstanding the foregoing, Landlord, upon request by Tenant, shall grant to Tenant and Tenant’s agents a license to enter the Premises at any time
from and after the date which Landlord reasonably determines to be twenty-one (21) days prior to the date Landlord’s Work (as defined herein) will be substantially completed for the purposes of
installing Tenant’s furniture, fixtures, equipment and cabling in the Premises. It shall be a condition to the grant by Landlord and continued effectiveness of such license that: 

 

	 	(a)	Tenant’s request for such early access shall be accompanied by: (i) a description of and schedule for the work to be performed by those persons and entities for whom such access is being requested;
(ii) the names and addresses of all contractors for whom such early access is being requested and copies of all licenses and permits required in connection with the performance of the work for which such access is being requested; and (iii)
certificates of insurance (in amounts and with insured parties satisfactory to Landlord). All of the foregoing shall be subject to Landlord’s reasonable approval. 

 

	 	(b)	Such early access for installation purposes shall be subject to reasonable scheduling by Landlord. 

  

	 	(c)	Tenant’s agents, contractors, workmen, mechanics, suppliers and invitees shall work in harmony and not interfere with (i) Landlord and Landlord’s agents in performing Landlord’s Work or work by
Landlord or its agents in other premises or common areas of the Building, or (ii) the general operation of the Building. If at any time such entry shall cause or reasonably threaten to cause such disharmony or interference (including
introducing union labor to the Building), Landlord may withdraw such license if, upon written notice to Tenant, Tenant fails to correct such interference within 24 hours. 

Any such entry into and occupation of the Premises by Tenant shall be deemed to be under all of the terms, covenants, conditions and provisions
of the Lease (including, without limitation, the insurance and indemnity provisions therein), excluding only the covenant to pay Fixed Rent, additional rent or electricity; provided, however, that, notwithstanding the foregoing, Tenant’s
obligation to pay Fixed Rent, additional rent and electricity hereunder shall commence upon Tenant conducting any material and regular business activities at the Premises. Landlord shall not be liable for any injury, loss or damage which may occur
to any of Tenant’s work or installations made in the Premises or to property placed therein prior to the commencement of the Term, the same being at Tenant’s sole risk and liability. Tenant shall be liable to Landlord for any damage to the
Premises or to any portion of Landlord’s Work caused by Tenant or any of 

  
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 Tenant’s employees, agents, contractors, workmen or suppliers. In the event the performance of the work by
Tenant, its agents, employees or contractors causes material extra costs to Landlord, Tenant shall reimburse Landlord for the entire extra cost upon receipt of substantiating backup of such cost. 

2.6 Monthly Fixed Rent Payments 
 Tenant
shall pay, commencing on the Rent Commencement Date, without notice, demand, offset or deduction, monthly installments of Fixed Rent in advance on the first day of each month to such person and at such place as Landlord shall from time to time
designate by notice to Tenant. Landlord initially designates its address set forth in Section 1.2 for this purpose. 
 Fixed Rent for
any partial calendar month following the Rent Commencement Date shall be prorated on a daily basis, and shall be due and payable in advance on the Rent Commencement Date. 

If the Landlord’s Work is not substantially completed by November 15, 2015, then, excluding any delay caused by Tenant, the Rent
Commencement Date will be extended for a period of time equal to (i) the total number of days between November 15, 2015 and the day on which the Landlord’s Work is substantially completed. In such circumstances, at the request of
either Party, the Parties shall execute an amendment to the Lease solely for the purpose of implementing such modifications; provided, however, that such modifications shall be deemed to take effect immediately, whether or not such executed
amendment to the Lease has been executed. 
 2.7 Adjustments for Operating Expenses 

A. Terms used herein are defined as follows: 

(1) “Operating Expenses for the Property” means the cost of operation of the Property which shall exclude
costs of special services rendered to tenants (including Tenant) for which a separate charge is made and items of expense referred to in Section 2.8 hereof, but shall include, without limitation, the following: premiums
for insurance carried with respect to the Property; compensation and all fringe benefits, worker’s compensation insurance premiums and payroll taxes paid to, for or with respect to all persons engaged in directly operating, repairing,
maintaining, or cleaning of the Property; steam, water, sewer, electric, gas, oil and telephone and other utility charges; costs of building and cleaning supplies, materials and equipment; costs of maintenance, cleaning and repairs; costs of snow
removal and care of landscaping; fees, expenses and contributions for the Building and Property to the common expenses of the office park in which they are located; payments under service contracts for any of the foregoing services with independent
contractors or subsidiaries or affiliates of Landlord; management fees at reasonable rates consistent with the type of occupancy and the service rendered and all other reasonable and necessary expenses paid in connection with the operation, repair,
cleaning and maintenance of the Property. Any of the services may be performed by subsidiaries or affiliates of Landlord, provided that the contracts for the performance of such services shall be competitive with comparable first class office
buildings in the Boston metropolitan area. 

  
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 For purposes of the preceding definition, the Operating Expenses for the Property shall include
the cost (amortized with interest using generally accepted accounting principles) of any capital improvement (including, without limitation any equipment installed as a fixture) made by Landlord for the purpose of (a) reducing other operating
costs; or (b) complying with any governmental requirement (including, without limitation, any law, ordinance, code, regulation or bylaw) which shall first become applicable to the Property after the date of this Lease; or (c) such items as
are required to keep the Building and Property as a first quality office building in the Boston metropolitan area. 
 Notwithstanding the
foregoing, Operating Expenses for the Property shall exclude: 
 (a) Expenses for any item or service not provided to Tenant but
provided exclusively to another tenant in that tenant’s space within the Building; 
 (b) Expenses for any item or service which Tenant
pays directly to a third party or separately pays to Landlord (e.g., electricity); 
 (c) Landlord’s general corporate overhead and
administrative expenses; 
 (d) Expenses incurred by Landlord to resolve disputes, enforce or negotiate lease terms with prospective or
existing tenants or in connection with any financing, sale or syndication of the Property; 
 (e) Any cost incurred by the gross negligence
or willful misconduct of the Landlord, its agents and employees; 
 (f) Penalties, fines and other costs incurred due to violation by the
Landlord of any lease or any laws, rules, regulations or ordinances applicable to the Building and any interest or penalties due for late payment by Landlord of any of the Operating Expenses for the Property; 

(g) Expenses incurred by Landlord to (i) lease space to new tenants or to retain existing tenants including leasing commissions,
advertising and promotional expenditures, and (ii) prepare, renovate, repaint, redecorate or perform any other work in any space leased to an existing or prospective tenant or other occupant of the Building; 

(h) Depreciation and amortization, except to the extent provided above; 

(i) Interest, principal, points and fees, amortization or other costs and expenses associated with any debt or rent payable under any ground
lease; 
 (j) Real Estate Taxes for the Property; 

(k) Cost of alterations, capital improvements, equipment replacement and other items (including reserves for the same) which under generally
accepted accounting principles are properly classified as capital expenditures except for capital expenditures to the extent expressly permitted above; 

  
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 (l) Payments for rented equipment, the cost of which equipment would constitute a capital
expenditure if the equipment were purchased; 
 (m) Costs and expenses incurred by the Landlord in connection with the repair of damage to
the Building or Property caused by fire or other casualty, insured or required to be insured against hereunder; and 
 (n) Costs and expenses
of investigating, monitoring and remediating hazardous materials on, under or about the Building. 
 (2) The “Operating
Statement” shall mean a statement rendered to Tenant by Landlord within approximately one hundred twenty (120) days or as soon thereafter as reasonably possible after the end of each calendar year during the Term. The Operating
Statement shall be in reasonable detail, certified by Landlord’s representative, and show the amount of the Operating Expenses for the Property and the Operating Expenses Allocable to the Premises for the preceding calendar year or fraction
thereof, as the case may be. 
 (3) The phrase “Operating Expenses Allocable to the Premises” means Tenant’s
Proportionate Share of the Operating Expenses for the Property. 
 (4) In any calendar year when the Building has an average annual occupancy
rate of less than ninety-five percent (95%), then, for the purpose of this Section 2.7, items which are variable according to occupancy comprising the Operating Expenses for the Property shall be equitably adjusted as though the Building were
ninety-five percent (95%) occupied. In any calendar year when the Building has an average annual occupancy rate of ninety-five percent (95%) or more then the Operating Expenses for the Property shall be the actual Operating Expenses for the
Property. 
 B. If, with respect to any calendar year or fraction thereof ending within the Term, the Operating Expenses Allocable to the
Premises for a full calendar year exceed Tenant’s Operating Expense Base then, within thirty (30) days after receipt by Tenant of the Operating Statement, Tenant shall pay to Landlord, as additional rent, the amount of such excess, less
any amounts previously paid by Tenant pursuant to Paragraph C below. In the event the actual amounts due for the period encompassed by Landlord’s statement are less than the estimated amounts theretofore paid by Tenant with respect to such
period, Tenant shall receive a credit for the excess amounts paid, which credit may be applied against subsequent installments of additional rent due under this Section 2.7, or, if this Lease has already been terminated, Landlord shall refund
such amounts to Tenant within 15 business days. 
 C. Landlord shall have the right from time to time by notice to Tenant to estimate amounts
required to be paid by Tenant under this Section 2.7 to reflect Landlord’s latest reasonable estimate of the actual amounts which will be due from Tenant hereunder based upon then current budgets and expenditures incurred to date.
Following any notice by Landlord requesting that Tenant make estimated monthly payments toward its obligation under this Section 2.7, Tenant shall make such monthly payments in accordance with such notice, until 

  
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 further notice is given by Landlord. If the Term of this Lease expires prior to the determination by Landlord and
payment by or refund to Tenant of any amounts due hereunder, Tenant’s obligation to pay and Landlord’s obligation to refund such amounts for any portion of the Term of this Lease shall survive the termination of this Lease even though
determination of such amounts may not be made until after such termination. 
 D. Landlord agrees to keep books and records showing Operating
Expenses for the Property in accordance with a system of accounts and accounting practices consistently maintained. Tenant shall have the right, at its sole expense, upon reasonable prior notice to Landlord, to inspect such books and records at
Landlord’s office during business hours for ninety days following receipt of an annual Operating Statement; provided, however, that such right may not be exercised by an agent of Tenant whose fee is based on the success of the inspection.
Should such inspection reveal errors in excess of five percent (5%), Landlord shall reimburse Tenant for its reasonable out of pocket expenses of such inspection. 

2.8 Adjustments for Real Estate Taxes 
 A.
Terms used herein are defined as follows: 
 (1) “Tax Year” means the twelve-month period beginning July 1 each
year during the Term or if the appropriate governmental tax fiscal period shall begin on any date other than July 1, such other date. 

(2) “Landlord’s Tax Expenses” with respect to any Tax Year means the aggregate Real Estate Taxes for the Property
with respect to that Tax Year, reduced by any abatements actually received with respect to that Tax Year. 
 (3) “Real Estate
Taxes for the Property” means all taxes and special assessments of every kind and nature assessed by any governmental authority on the Lot or the Building or the Property which Landlord shall become obligated to pay because of or in
connection with the ownership, leasing and operation of the Lot, the Building and the Property and reasonable expenses of any proceedings for abatement of taxes. The amount of special taxes or special assessments to be included shall be limited to
the amount of the installment (plus any interest, other than penalty interest, payable thereon) of such special tax or special assessment required to be paid during the year in respect of which such taxes are being determined. There shall be
excluded from such taxes all income, estate, succession, inheritance and transfer taxes and interest and penalties assessed by reason of Landlord’s failure to pay such real estate taxes when due; provided, however, that if at any time during
the Term the present system of ad valorem tax of real property shall be changed so that in lieu of the whole or any part of the ad valorem tax on real property, there shall be assessed on Landlord a capital levy or other tax on the gross rents
received with respect to the Lot or Building or Property, or a federal, state, county, municipal, or other local income, franchise, excise or similar tax, assessment, levy or charge (distinct from any now in effect in Massachusetts) measured by or
based, in whole or in part, upon any such gross rents, then any and all of such taxes shall be included within the term “Real Estate Taxes for the Property.” 

  
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 (4) The “Tax Statement” shall mean a statement rendered to Tenant by
Landlord within thirty (30) days or as soon thereafter as reasonably practical after receipt of the real estate tax bills for each Tax Year (or partial year, if applicable) during the Term and within ninety (90) days or as soon thereafter
as reasonably practical after Lease termination. The Tax Statement shall be in reasonable detail showing for the respective Tax Year or fraction thereof, as the case may be, Real Estate Taxes for the Property. 

(5) “Tax Expenses Allocable to the Premises” means Tenant’s Proportionate Share of Real Estate Taxes for the
Property. 
 B. If with respect to any Tax Year, Tax Expenses Allocable to the Premises exceed Tenant’s Tax Base, then within thirty
(30) days after receipt by Tenant of the Tax Statement, Tenant shall pay to Landlord, as additional rent, the amount of such excess, less any amounts previously paid by Tenant pursuant to Paragraph C below. In the event the actual amounts due
for the period encompassed by the Tax Statement are less than the estimated amounts theretofore paid by Tenant with respect to such period, Tenant shall receive a credit for the excess amounts paid, which credit may be applied against subsequent
installments of additional rent due under this Section 2.8, or, if this Lease has already been terminated, Landlord shall promptly refund such amounts to Tenant. Appropriate prorations shall be made for those periods at the beginning or end of
the Term which are less than a full Tax Year. 
 C. Landlord shall have the right from time to time by notice to Tenant to estimate amounts
required to be paid by Tenant under this Section 2.8 to reflect Landlord’s latest reasonable estimate of the actual amounts which will be due from Tenant hereunder. Following any notice by Landlord requesting that Tenant make estimated
monthly payments toward its obligation under this Section 2.8, Tenant shall make such monthly payments in accordance with such notice, until further notice is given by Landlord. If the Term of this Lease expires prior to the determination by
Landlord and payment by or refund to Tenant of any amounts due hereunder, Tenant’s obligation to pay and Landlord’s obligation to refund such amounts for any portion of the Term of this Lease shall survive the termination of this Lease
even though determination of such amounts may not be made until after such termination. 
 D. To the extent that Real Estate Taxes for the
Property shall be payable to the taxing authority in installments for periods less than a Tax Year, the foregoing statement shall be rendered and payments made on account of such installments with respect to such periods rather than with respect to
such full Tax Year. 
 E. No decrease in Real Estate Taxes for the Property with respect to any Tax Year shall result in a reduction of the
Fixed Rent payable by Tenant. 
 2.9 Electricity Charge 

Tenant shall initially pay $1.50 per rentable square foot per year for the estimated cost of electricity for lights and outlets within the
Premises (subject to adjustment pursuant to Section 2.7(C)), payable in equal monthly installments with the Fixed Rent and subject to the reconciliation process set forth in Section 2.7(B). The actual cost of Tenant’s share of
electricity within the Premises shall be included in the annual Operating Statement along with Tenant’s Proportionate Share of common area electricity. Tenant shall not exceed electrical usage of 6.5 watts per square foot included in the
Premises. 

  
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 2.10 Due Date of Additional Payments; No Offsets 

Except as otherwise specifically provided herein, any sum, amount, item or charge designated or considered as additional rent in this Lease
shall be paid by Tenant to Landlord on or before the tenth (10th) business day after Landlord notifies Tenant of the amount payable. Any such notice shall specify in reasonable detail the basis of such additional rent. Additional rent shall be paid
by Tenant to Landlord without offset or deduction. 
 2.11 Late Payment of Rent 

If any installment of Fixed Rent or payment of additional rent is paid after the date the same was due, it shall bear interest from the due
date at the rate published as the “prime rate” in The Wall Street Journal, as it may be adjusted from time to time, plus six percent (6%) per annum, but in no event more than the maximum rate of interest allowed by law, the payment
of which shall be additional rent. For any installment of Fixed Rent or additional rent paid after the date the same was due, Tenant shall pay to Landlord, as additional rent, an amount equal to five percent (5%) of the total amount of delinquent
rent (Fixed Rent plus additional rent) to offset Landlord’s administrative expenses resulting from Tenant’s delinquent payment. 
 2.12 Renewal
Option 
 A. Provided that (i) a default as described in Section 7.1 of the Lease shall not have occurred and be continuing on
the day on which Tenant purports to exercise the Renewal Option (defined below) or on the first day of the applicable Renewal Term (as defined below), and (ii) the Tenant named herein or a Tenant Affiliate is actually occupying at least 80% of
the Premises as of each of said dates, Tenant shall have the option (“Renewal Option”) to renew the Term of this Lease for one (1) additional periods of three (3) years (the “Renewal Term”),
unless sooner terminated as provided in this Lease, subject to all the terms of this Lease except for the change in Fixed Rent as provided below and there shall be no further Renewal Options. 

B. Tenant shall exercise the Renewal Option, if at all, by giving written notice (“Notice to Renew”) of exercise to
Landlord no later than nine (9) months prior to expiration of the Term. If Tenant fails to give such notice to Landlord within such time, Tenant shall be deemed to have waived the right to exercise the Renewal Option. Upon Tenant’s
exercise of each Renewal Option, the Term shall be deemed to include the applicable Renewal Term. 
 C. The annual Fixed Rent payable during
each Renewal Term shall be the fair market rent for comparable first class office space in effect in the 128 West office market on the commencement date of the applicable Renewal Term (the “Fair Market Rent”). The
determination of Fair Market Rent (whether such determination is made by Landlord and/or Tenant or the brokers referenced herein) shall take into account all relevant factors such as (but not limited to) the rental rate currently charged by Landlord
for space at the Property, the term of the lease, the base year for operating expenses and taxes, and brokerage commissions. The Fair Market Rent shall be determined as follows: 

  
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 (1) Within fifteen (15) calendar days after receipt of a Notice to Renew, Landlord shall
furnish Tenant with Landlord’s estimate of Fair Market Rent (“Landlord’s Rent Estimate”). 
 (2) Within
fifteen (15) calendar days after receipt of Landlord’s Rent Estimate, Tenant shall respond and specify whether and the extent to which Tenant disputes Landlord’s Rent Estimate. 

(3) If Tenant disputes Landlord’s Rent Estimate, Tenant and Landlord shall negotiate in good faith for an additional thirty
(30) calendar days to reach agreement on the Fair Market Rent. 
 (4) If Tenant and Landlord shall not have reached agreement as to the
Fair Market Rent after such additional thirty (30) calendar days, Landlord and Tenant, within ten (10) calendar days after the expiration of such thirty (30) calendar day period, shall each select a real estate broker affiliated with
a major Boston commercial real estate brokerage firm and having at least fifteen (15) years’ experience in the field with office properties similar to the Building in the Boston area to determine the Fair Market Rent. The two selected
brokers shall within fourteen (14) calendar days appoint a third broker having the qualifications described above (the “Third Broker”). Each party shall pay the fees and expenses of the broker it selected and the fees
and expenses of the Third Broker shall be borne equally by both parties. 
 (5) Within thirty (30) calendar days after the selection of
the Third Broker, the brokers shall determine the Fair Market Rent. In the event that the brokers have not agreed upon the Fair Market Rent within such thirty (30) day period, each broker shall simultaneously deliver, within ten
(10) calendar days thereafter, a written appraisal of the Fair Market Rent to Landlord and Tenant, and the Fair Market Rent shall be the average of the two closest appraisals. 

(6) If Landlord or Tenant shall have failed to designate a broker within the time period provided therefor above, then the broker which has
been designated, whether by Landlord or Tenant, shall alone make the determination of the Fair Market Rent. If Tenant and Landlord have both designated brokers but the two brokers so designated do not agree upon and designate the third broker
willing so to act within the time period provided therefor above, the Tenant, the Landlord or either broker previously designated may request the Greater Boston Real Estate Board, Inc. to designate the third broker willing so to act and a broker so
appointed shall, for all purposes, have the same standing and powers as though such broker had been seasonably appointed by the brokers first appointed. In case of the inability or refusal to serve of any person designated as a broker, or in case
any broker for any reason ceases to be such, a broker to fill such vacancy shall be appointed by the Tenant, the Landlord, the broker first appointed or the said Greater Boston Real Estate Board, Inc., as the case may be, whichever made the original
appointment. 

  
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 ARTICLE III 

CONSTRUCTION 
 3.1 Premises As Is

 THE PREMISES ARE LEASED “AS IS” AND “WHERE IS” AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTY WHATSOEVER, INCLUDING ANY
WARRANTY OF MERCHANTABILITY, HABITABILITY OR FITNESS FOR INTENDED USE. 
 3.2 Landlord’s Work 

Landlord shall prepare the Premises for Tenant’s use by painting and re-carpeting the Premises
with building standard materials and finishes (“Landlord’s Work”). Notwithstanding anything to the contrary, Tenant shall be responsible for all furniture, tel/data wiring, security, other specialty items for the
Premises (including dedicated HVAC units, if any) and any other improvements not part of Landlord’s Work at Tenant’s sole cost and expense. 
 3.3
General Provisions Applicable to Construction 
 All construction work required or permitted by this Lease, whether by Landlord or
Tenant, shall be done in a good and workmanlike manner and in compliance with all applicable laws and all lawful ordinances, regulations and orders of governmental authority and insurers of the Property. Each party may inspect the work of the other
at reasonable times and shall promptly give notice of observed defects. 
 3.4 Liens 

Tenant will not permit any mechanic’s lien or other liens to be placed upon the Premises or the Property as a result of any materials or
labor ordered by Tenant or any of Tenant’s agents, officers, or employees. If such a lien is filed, then within five (5) days after Landlord has delivered notice to Tenant, Tenant must either pay the amount of the lien or diligently
contest such lien and deliver to Landlord a bond or other security satisfactory to Landlord. If Tenant fails to comply with the foregoing provisions of this Section 3.4, Landlord may exercise its self-help rights set forth in Section 8.6
to discharge or bond over the lien at Tenant’s sole cost and expense in any manner deemed appropriate by Landlord in its sole discretion. 

ARTICLE IV 

LANDLORD’S COVENANTS; INTERRUPTIONS AND DELAYS 

Landlord covenants: 
 4.1 Services Furnished by Landlord

 To furnish, through Landlord’s employees or independent contractors, services, utilities, facilities and supplies set forth in
Exhibit D equal in quality to those customarily provided by landlords in similar office buildings in the vicinity of the Building. 
  

  
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 4.2 Additional Services Available to Tenant 

To furnish, through Landlord’s employees or independent contractors, at Tenant’s expense, reasonable additional building operation
services which are usual and customary additional services in similar office buildings in the vicinity of the Building upon reasonable advance request of Tenant at reasonable, equitable market rates from time to time established by Landlord. 

4.3 Roof, Exterior Wall, Floor Slab and Common Facility Repair 

Except as otherwise provided in ARTICLE VI, to make such repairs to the roof, exterior walls, other structural components, floor slabs,
exterior glass (except as set forth in Section 5.2) and common areas and facilities including all utilities and elevators, of the Property as may be necessary to keep them in good order, repair and condition, the expense of which shall be
charged in accordance with Section 2.7. 
 4.4 Quiet Enjoyment 

That Tenant on paying the Fixed Rent and additional rent and performing the obligations of Tenant in this Lease shall peacefully and quietly
have, hold and enjoy the Premises without interference from Landlord, or persons claiming by, through or under Landlord, subject to all of the terms and provisions hereof. 

4.5 Interruptions and Delays in Service and Repairs, etc. 

Landlord shall not be liable to Tenant for any compensation or reduction of rent by reason of inconvenience or annoyance or for loss of
business arising from the necessity of Landlord or its agents’ entering the Premises for any of the purposes in this Lease authorized, or for repairing the Premises or any portion of the Building however the necessity may occur. In case
Landlord is prevented or delayed from making any repairs, alterations or improvements, or furnishing any services or performing any other covenant or duty to be performed on Landlord’s part, by reason of any cause reasonably beyond
Landlord’s control, Landlord shall not be liable to Tenant therefor, nor except as expressly otherwise provided in this Section 4.5 or Section 6.1 shall Tenant be entitled to any abatement or reduction of rent by reason thereof, nor
shall the same give rise to a claim in Tenant’s favor that such failure constitutes actual or constructive, total or partial, eviction from the Premises. 

Landlord reserves the right to stop any service or utility system, when necessary by reason of accident or emergency, or until necessary
repairs have been completed; provided, however, that in each instance of stoppage Landlord shall exercise reasonable diligence to eliminate the cause thereof. Except in case of emergency repairs, Landlord will give Tenant reasonable advance notice
of any contemplated stoppage and will use reasonable efforts to avoid unnecessary inconvenience to Tenant by reason thereof. 

Notwithstanding anything to the contrary contained herein, if: (i) Landlord ceases to furnish any service in the Building for a period in
excess of five (5) consecutive days after Tenant notifies Landlord of such cessation (the “Interruption Notice”); (ii) such cessation results from an act or omission of Landlord; (iii) the restoration of such service is within
the reasonable 

  
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 control of Landlord; and (iv) as a result of such cessation, the Premises, or a material portion thereof, is
rendered untenantable and Tenant in fact ceases to use the Premises, or a material portion thereof (each such cessation, a “Material Service Interruption”), then Tenant, as its sole remedy, shall be entitled to receive an
abatement of Fixed Rent and additional rent during the period beginning on the sixth (6th) consecutive day after Landlord’s receipt of the Interruption Notice and ending on the day when the service in question has been restored. In the event
the entire Premises has not been rendered untenantable by the Material Service Interruption, the amount of abatement that Tenant is entitled to receive shall be prorated based upon the percentage of the Premises so rendered untenantable and not used
by Tenant. 
 4.6 Payment of Legal Expenses 

To pay all reasonable costs, counsel and other fees incurred by Tenant in connection with the successful enforcement by Tenant of any
obligations of Landlord under this Lease. 
 4.7 Landlord to Maintain Insurance; Waiver of Subrogation  

Landlord shall procure and maintain the following: 

(a) Property insurance “the equivalent of causes of loss – special form” on the Property. Landlord shall not be obligated to
insure any furniture, equipment, trade fixtures, machinery, goods, or supplies which Tenant may keep or maintain in the Premises or any alteration, addition, or improvement which Tenant may make upon the Premises. In addition, Landlord may elect to
secure and maintain rental income insurance. If the annual cost to Landlord for such property or rental income insurance exceeds the standard rates because of the nature of Tenant’s operations, Tenant shall, upon receipt of appropriate
invoices, reimburse Landlord for such increased cost. 
 (b) Commercial general liability insurance, which shall be in addition to, and not
in lieu of, insurance required to be maintained by Tenant. Tenant shall not be included as an additional insured on any policy of liability insurance maintained by Landlord. 

(c) Landlord waives any and all rights of recovery against Tenant for or arising out of damage to, or destruction of the Premises to the extent
(i) that Landlord’s property insurance policies then in force insure against such damage or destruction and permit such waiver and only to the extent of insurance proceeds actually received by Landlord for such damage or destruction; or
(ii) such damage or destruction would have been covered by insurance proceeds had Landlord maintained the insurance required hereunder. 

(d) Landlord will not be responsible for or liable to Tenant for any loss or damage that may be occasioned by or through the acts or omissions
of persons occupying adjoining premises or any part of the premises adjacent to or connected with the Premises or any part of the Building or for any loss or damage resulting to Tenant or its property from burst, stopped or leaking water, gas, sewer
or steam pipes or falling plaster, or electrical wiring or for any damage or loss of property within the Premises from any causes whatsoever, including but not limited to theft, and/or acts or threatened acts of terrorism, damage or injury due to
mold, excepting only losses or damages resulting from the gross negligence or willful misconduct of Landlord. Landlord will not be liable under any circumstances to Tenant for any incidental or consequential damages. 

  
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 (e) Landlord, its agents, servants, employees, invitees, or contractors (each an
“Indemnified Party”) shall not be liable to Tenant and Tenant hereby waives all claims against each Indemnified Party for any injury to or death of any person or damage to or destruction of property in or about the Premises
or the Property by or from any cause whatsoever, including, without limitation, gas, fire, oil, electricity or leakage of any character from the roof, walls, basement or other portion of the Premises or the Property, but excluding, however, the
gross negligence or willful misconduct of any Indemnified Party of which gross negligence or willful misconduct Landlord has knowledge and reasonable time to correct. Except as to injury to persons or damage to property to the extent caused by the
gross negligence or willful misconduct of an Indemnified Party, Tenant shall indemnify, defend and hold each Indemnified Party harmless from and against any and all expenses, including reasonable attorneys’ fees, in connection therewith,
arising out of any injury to or death of any person or damage to or destruction of property occurring in, on or about the Premises, or any part thereof, from any cause whatsoever. 

(f) To the maximum extent permitted by law, Tenant shall indemnify, defend and hold harmless the Indemnified Parties (including reasonable
attorneys’ fees, investigation costs and remediation costs) from and against any and all claims, demands, liabilities, damages, judgments, fines and penalties which in any manner whatsoever arise out of or are in any manner related to:
(i) Tenant’s failure to maintain the Premises pursuant to Section 5.2 of this Lease; or (ii) the presence of mold in the Premises or Building to the extent caused by, contributed to, or allowed by Tenant. 

(g) Except for damages incurred by Landlord pursuant to Section 8.15 of this Lease, Tenant will not be liable under any circumstances to
Landlord for any incidental or consequential damages. 
 ARTICLE V 

TENANT’S COVENANTS 

Tenant covenants during the Term and such further time as Tenant occupies any part of the Premises: 

5.1 Payments 
 To pay when due all Fixed
Rent and additional rent and all charges for utility services rendered to the Premises and, as further additional rent, all charges for additional services and utilities rendered pursuant to Section 4.2. 

5.2 Repair and Yield Up 
 Except as
otherwise provided in ARTICLE VI and Section 4.3, at its sole cost and expense, to keep the Premises in good order, repair and condition, and all glass in windows 

  
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 (except uninsured glass in exterior walls of the Building unless the damage thereto is attributable to
Tenant’s negligence or misuse) and doors of the Premises whole and in good condition with glass of the same quality as that injured or broken, damage by fire and other casualty and reasonable wear only excepted, and at the expiration or
termination of this Lease peaceably to yield up the Premises and all alterations and additions thereto in good order, repair and condition, damage by fire and other casualty excepted, first removing all goods and effects of Tenant and, if identified
by Landlord for removal at the time that Tenant requested Landlord’s approval, all alterations and additions made by Tenant and all partitions, and repairing any damage caused by such removal and restoring the Premises and leaving them clean
and neat and in reasonably tenantable condition for office use. 
 5.3 Use 

To use and occupy the Premises for the Permitted Uses, and not to injure or deface the Premises, or the Property, nor to permit in the Premises
any auction sale, or inflammable fluids or chemicals (except that Tenant may keep and use in the Premises normal office supplies in full compliance with law), nor to permit any nuisance, or the emission from the Premises of any objectionable noise
or odor, nor to use or devote the Premises or any part thereof for any purpose other than the Permitted Uses, nor any use thereof which is contrary to law or ordinance or liable to invalidate or increase the premiums for any insurance on the
Building or liable to render necessary any alteration or addition to the Building. 
 5.4 Obstructions; Items Visible from Exterior; Rules and
Regulations; Signs 
 Not to obstruct in any manner any portion of the Building not hereby leased or any portion thereof or of the
Property; not without prior consent of Landlord to permit the painting or placing of any signs, curtains, blinds, shades, awnings, aerials or flagpoles, or the like, visible from outside the Premises; and to comply with Landlord’s Rules and
Regulations set forth in Exhibit E and all other reasonable Rules and Regulations now or hereafter made by Landlord, of which Tenant has been given notice, for the care and use of the Building and Lot and their facilities and approaches;
Landlord shall not be liable to Tenant for the failure of other occupants of the Building to conform to such Rules and Regulations, but Landlord shall use reasonable efforts to enforce the same in a
non-discriminatory manner against all tenants and occupants of the Building. Tenant’s name shall be displayed on the tenant directory within the Building and on the doors to the Premises in accordance
with Landlord’s standard graphics or such other graphics as Landlord shall approve in its sole discretion. Except on such directory and doors to the Premises and on floors of the Building occupied solely by Tenant, no other signs for Tenant on
the interior of the Building will be permitted without Landlord’s consent which will not be unreasonably withheld. 
 5.5 Safety Appliances;
Hazardous Materials 
 To keep the Premises equipped with all safety appliances required by law or ordinance or any other regulation of
any public authority because of any use made by Tenant or its employees, agents, officers, customers or clients other than normal office use, and to procure all licenses and permits so required because of such use and, if requested by Landlord, to
do any work so required because of such use, it being understood that the foregoing provisions shall not be construed to broaden in any way Tenant’s Permitted Uses. 

  
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 Tenant shall not cause, suffer or allow any hazardous materials to be used, generated, stored or
disposed of on, under or about the Premises except in accordance with applicable law. Tenant shall defend, indemnify and save harmless Landlord from and against any injuries, claims, accidents, damages, liabilities and expenses and any contamination
of or injury to the Premises or the Building or the Lot (including reasonable counsel fees) arising out of any breach of Tenant’s obligations under this Section 5.5 or any storage, use, disposal or release of the foregoing materials by
Tenant. 
 Tenant shall provide Landlord on February 1 and August 1 of each year of the Term with a list of the names and
quantities of all hazardous materials generated, stored or used at the Premises (other than reasonable quantities of cleaning and office supplies). Material Safety Data Sheets shall be provided for all such substances. Storage of all hazardous
materials shall be in accordance with applicable federal, state and local laws, regulations and ordinances. Tenant shall prepare and follow a spill prevention and countermeasure plan for such substances. Transfer and mixing of hazardous materials
shall be performed in a designated area designed and operated to prevent spilling, leakage or runoff from escaping from the Premises. Tenant shall comply with all applicable OSHA rules applicable to its business and the handling of hazardous
materials. 
 Tenant shall immediately notify Landlord both by telephone and in writing of any spill or unauthorized discharge or release of
hazardous materials. At the expiration or termination of this Lease, Tenant shall yield up the Premises free of all hazardous materials and contaminants of any kind resulting from Tenant’s use of the Premises or any action of Tenant, its
employees, agents, contractors and invitees. 
 For purposes of this paragraph the term hazardous material shall mean, (i) “hazardous
substances” or “toxic substances” or “oil” as those terms are defined by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 42 U.S.C. § 9601, et seq., or the Hazardous Materials
Transportation Act, 49 U.S.C. § 1801 or the Massachusetts Oil and Hazardous Material Release Prevention and Response Act, M.G.L. c. 21E; (ii) “hazardous wastes,” as that term is defined by the Resource Conservation and Recovery Act
(RCRA), 42 U.S.C. § 6901, et seq.; (iii) any pollutant or contaminant or hazardous, dangerous, or toxic chemicals, materials, or substances within the meaning of any other applicable federal, state, or local law, regulation, ordinance, or
requirement relating to or imposing liability or standards of conduct concerning any hazardous, toxic, or dangerous waste substance or material; (iv) any radioactive material, including any source, special nuclear or by-product material as defined at 42 U.S.C. § 2011, et seq.; (v) asbestos in any form or condition; and (vi) polychlorinated biphenyls (PCBs) or substances or compounds containing PCBs. 

5.6 Assignment; Sublease 
 (a) Without
prior written consent of Landlord, not to assign, mortgage, pledge or otherwise transfer (directly or indirectly) this Lease or its rights hereunder, or to make any sublease, or to permit occupancy of the Premises or any part thereof by anyone other
than 

  
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 Tenant, except that Tenant may assign this Lease without Landlord’s consent (but with at least thirty
(30) days’ prior written notice to Landlord) to (i) an entity controlling, controlled by or under common control with Tenant, or (ii) an entity purchasing all of Tenant’s business, assets and liabilities, or (iii) an
entity that succeeds to the interests of Tenant under this Lease by way of merger, consolidation, or corporate reorganization (each entity described in clauses (i), (ii) and (iii) of this sentence, a “Tenant Affiliate”), only if
such Tenant Affiliate has a net worth at least equal to that of Tenant as of the date of this Lease. In connection with any proposed assignment or subletting, Tenant shall submit to Landlord in writing (i) the name of the proposed assignee or
sublessee, (ii) such information as to its financial responsibility and standing as Landlord may reasonably require, (iii) all of the terms and provisions upon which the proposed assignment or subletting is to be made; and (iv) the
nature of its business and proposed use of the Premises. Tenant shall supply such additional information as Landlord reasonably requests. 

(b) Tenant shall not offer to make or enter into negotiations with respect to an assignment or sublease (i) to any tenant in the Building
or the adjacent building at 880 Winter Street, Waltham, Massachusetts, (ii) to any party with whom, to Tenant’s knowledge (after first consulting with Landlord), Landlord is then negotiating (or with which it has negotiated in the last six
months) with respect to space in the Building or such adjacent building, (iii) to any party which would be of such type, character or condition as to be inappropriate as a tenant for a comparable office building, or (iv) unless the
aggregate rent payable to Tenant equals or exceeds the then prevailing market rate rent for assigning or subleasing (as applicable) space comparable to the Premises in comparable office buildings in the Boston Metropolitan area. 

(c) If Tenant intends to assign this Lease or sublease all or any part of the Premises, it shall notify Landlord thereof together with
identification of the space involved and the contemplated economic terms, and Landlord shall have the option, exercisable by notice to Tenant (a “Termination Notice”) given within thirty (30) days after receipt of any
such notification and information, to terminate this Lease as of a date specified in such Termination Notice, which date shall not be less than thirty (30) or more than ninety (90) days after the date of such Termination Notice. If Tenant
does not thereafter notify Landlord within two (2) business days following Tenant’s receipt of such Termination Notice that Tenant no longer intends to assign this Lease or sublease all or any part of the Premises, as applicable, Landlord
may exercise its right to terminate this Lease pursuant to the applicable provisions of this paragraph. If Tenant does so notify Landlord, then Landlord’s Termination Notice shall be deemed waived and of no further force or effect, and this
Lease shall continue in accordance with its terms. In no event shall Landlord’s right of recapture apply in case of a sublease or assignment to a Tenant Affiliate. 

(d) If Landlord does not exercise its right to terminate this Lease pursuant to the foregoing provisions, Landlord shall not unreasonably
withhold or delay its consent to an assignment or subletting consistent with the information supplied by Tenant in its notification, provided that the terms and provisions of such assignment or subletting shall specifically make applicable to the
assignee or sublessee all of the provisions of this Section 5.6 so that Landlord shall have against the assignee or sublessee all rights with respect to any further assignment and subletting which are set forth herein; no assignment or
subletting shall affect the continuing primary liability of Tenant (which, following assignment, shall be joint and several with the assignee); no consent to any of the foregoing in a specific instance shall operate as a waiver in a 

  
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 subsequent instance; and no assignment shall be binding upon Landlord or any of Landlord’s mortgagees,
unless Tenant shall deliver to Landlord an instrument in recordable form which contains a covenant of assumption by the assignee running to Landlord and all persons claiming by, through or under Landlord and Landlord and all of its mortgagees
decide, in their sole discretion, to accept such assumption, but the failure or refusal of the assignee to execute such instrument of assumption shall not release or discharge assignee from its liability as Tenant hereunder. Should Landlord exercise
its right to terminate this Lease to only a portion of the Premises, Tenant shall be obligated to reimburse Landlord for the cost of demising walls, doors and partitions in compliance with applicable codes and at Building standard finishes. 

(e) It shall be reasonable for Landlord to refuse consent to any assignment or sublease to any governmental agency or to any entity which by
reputation or expected use is not comparable to other types of tenants in the Building or to an entity which is a tenant of the Property or the adjacent building at 890 Winter Street, Waltham, Massachusetts, or to an entity which does not have, in
Landlord’s sole good faith determination, a satisfactory financial condition in relation to the obligations to be assumed under the assignment or sublease or if the assignment or sublease would cause Landlord to be in violation or any laws or
any other lease, mortgage or other agreement. If Tenant disputes Landlord’s decision to deny consent to an assignment or sublease, Tenant’s sole remedy shall be to seek injunctive relief. 

Without limitation of the rights of Landlord hereunder, if there is an assignment of this Lease by Tenant or a subletting of the Premises by
Tenant to any person or entity other than a Tenant Affiliate at a rent which, in either case, exceeds the rent payable hereunder by Tenant, Tenant shall pay to Landlord, as additional rent, fifty percent (50%) of such excess rent (after deducting
therefrom any reasonable costs incurred by Tenant for brokerage commissions, legal fees or fit up work or allowances in connection with such assignment or subletting). For purposes of this Section 5.6, the term “rent” shall mean all
Fixed Rent, additional rent or other payment and/or consideration payable to Tenant. 
 The term “subletting” or
“sublease” shall not only mean a sublease, but also any license or concession agreement or agreement for the use, occupancy or utilization of the Premises. Tenant shall reimburse Landlord for its reasonable legal and other expenses in
connection with any request for consent under this Section. 
 5.7 Indemnity; Insurance; Waiver of Subrogation 

A. To defend with counsel first reasonably approved by Landlord, save harmless, and indemnify Landlord, its agents and employees, from any
liability for injury, loss, accident or damage to any person or property, and from any claims, actions, proceedings and expenses and costs in connection therewith (including without limitation reasonable counsel fees), (i) arising from (a) the
omission, fault, willful act, negligence or other misconduct of Tenant, its employees, agents or invitees, or (b) any use made or thing done or occurring on the Premises not due to the negligence or willful misconduct of Landlord or its agents
or employees, or (ii) resulting from the failure of Tenant to perform and discharge its covenants and obligations under this Lease; 

B. In the event that Tenant fails to provide evidence of insurance required to be provided by Tenant in this Lease in accordance with
Section 5.7E, Landlord shall be authorized (but not required) to procure such coverage in the amount stated with all costs thereof to be chargeable to Tenant and payable upon written invoice thereof. 

  
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 C. The limits of insurance required by this Lease, or as carried by Tenant, shall not limit the
liability of Tenant or relieve Tenant of any obligation thereunder, except to the extent provided for under Section 4.7(b) of this Lease. Any deductibles selected by Tenant shall be the sole responsibility of Tenant. 

D. Tenant, at Tenant’s expense, agrees to keep in force during the Term of this Lease: 

(i) Commercial general liability insurance which insures against claims for bodily injury, personal injury, advertising injury, and property
damage based upon, involving, or arising out of the use, occupancy, or maintenance of the Premises and the Property. Such insurance shall afford, at a minimum, the following limits: 

 

			
		
	Each Occurrence	  	$1,000,000
		
	General Aggregate	  	$2,000,000
		
	Products/Completed Operations Aggregate	  	$1,000,000
		
	Personal and Advertising Injury Liability	  	$1,000,000
		
	Fire Damage Legal Liability	  	$100,000
		
	Medical Payments	  	$5,000

 Any general aggregate limit shall apply on a per location basis. Tenant’s commercial general liability insurance
shall include Waltham Winter Street 880 LP and, Waltham Winter Street 890 LP and, Clarion Partners, LLC, and CB Richard Ellis – N.E. Partners, Limited Partnership, and their trustees, officers, directors, members, agents, and employees,
Landlord’s mortgagees, Landlord’s property manager, Landlord’s representatives and any other party reasonably requested by Landlord as additional insureds (the “Additional Insured Parties”). This coverage shall
be written on the most current ISO CGL form (or its equivalent), shall include contractual liability, premises-operations and products-completed operations and shall contain an exception to any pollution exclusion which insures damage or injury
arising out of heat, smoke, or fumes from a hostile fire. Such insurance shall be written on an occurrence basis and contain a standard separation of insureds provision. 

(ii) Business automobile liability insurance covering owned, hired and non-owned vehicles with minimum
limits of $1,000,000 combined single limit per occurrence. 
 (iii) Workers’ compensation insurance in accordance with the laws of the
state in which the Premises are located with employer’s liability insurance in an amount not less than $1,000,000. 

  
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 (iv) Umbrella/excess liability insurance, on an occurrence basis, that applies excess of the
required commercial general liability, business automobile liability, and employer’s liability policies with the following minimum limits: 

Each
Occurrence                                 $5,000,000 

Annual
Aggregate                               $5,000,000 

Umbrella/Excess liability policies shall contain an endorsement stating that any entity qualifying as an additional insured on the insurance stated in the
Schedule of Underlying Insurance shall be an additional insured on the umbrella/excess liability policies, and that they apply immediately upon exhaustion of the insurance stated in the Schedule of Underlying Insurance as respects the coverage
afforded to any additional insured. The umbrella/excess liability policies shall also provide that they apply before any other insurance, whether primary, excess, contingent or on any other basis, available to an additional insured on which the
additional insured is a named insured (which shall include any self-insurance), and that the insurer will not seek contribution from such insurance. 

(v) Property insurance “the equivalent of causes of loss – special form” including flood, earthquake, windstorm, theft,
sprinkler leakage and boiler and machinery coverage on all of Tenant’s trade fixtures, furniture, inventory and other personal property in the Premises, and on any alterations, additions, or improvements made by Tenant upon the Premises all for
the full replacement cost thereof. Tenant shall use the proceeds from such insurance for the replacement of trade fixtures, furniture, inventory and other personal property and for the restoration of Tenant’s improvements, alterations, and
additions to the Premises. Landlord shall be named as loss payee with respect to alterations, additions, or improvements of the Premises where the Tenant cannot remove at the end of the lease term wherein ownership then reverts to the Landlord. 

(vi) Business income and extra expense insurance with limits not less than one hundred percent (100%) of all rent and charges payable by Tenant
under this Lease for a period of twelve (12) months. 
 E. All policies required to be carried by Tenant hereunder shall be issued by an
insurance company licensed or authorized to do business in the state in which the Property is located with a rating of at least “A-: X” or better as set forth in the most current issue of Best’s
Insurance Reports, unless otherwise approved by Landlord. Tenant shall not do or permit anything to be done that would invalidate the insurance policies required herein. Liability insurance maintained by Tenant shall be primary coverage on behalf of
the Additional Insured Parties and any policies of the Additional Insured Parties shall be non-contributory. Certificates of insurance, acceptable to Landlord, evidencing the existence and amount of each
insurance policy required hereunder shall be delivered to Landlord prior to delivery or possession of the Premises and ten (10) days following each renewal date. Certificates of insurance shall evidence that the Additional Insured Parties are
included as additional insureds on liability policies and that Landlord is included as loss payee on the property insurance with respect to alterations, additions, or improvements of the Premises where the Tenant cannot remove at the end of the
lease term wherein ownership then reverts to the Landlord. Further, each policy shall contain provisions endeavoring to give Landlord and each of the other Additional Insured Parties at least thirty (30) days prior written notice of
cancellation or non-renewal of coverage. 

  
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 F. In the event that Tenant fails to provide evidence of insurance required to be provided by
Tenant in this Lease, prior to the Commencement Date and thereafter during the Term, within ten (10) days following Landlord’s request thereof, and thirty (30) days prior to the expiration of any such coverage, Landlord shall be
authorized (but not required) to procure such coverage in the amount stated with all costs thereof to be chargeable to Tenant and payable upon written invoice thereof. 

G. The limits of insurance required by this Lease, or as carried by Tenant, shall not limit the liability of Tenant or relieve Tenant of any
obligation thereunder, except to the extent provided for under Section 4.7 above. Any deductibles selected by Tenant shall be the sole responsibility of Tenant. 

H. Tenant insurance requirements stipulated in Section 5.7(D)(i) are based upon current industry standards. Landlord reserves the right to
require additional coverage or to increase limits as industry standards change. 
 I. Should Tenant engage the services of any contractor to
perform work in the Premises, Tenant shall ensure that such contractor carries commercial general liability, business automobile liability, umbrella/excess liability, worker’s compensation and employers liability coverages in substantially the
same forms as required of the Tenant under this Lease and in amounts approved by landlord and/or landlord’s property manager. Contractor shall include Landlord and each of the other Additional Insured Parties as additional insureds on the
liability policies required hereunder. 
 All policies required to be carried by any contractor shall be issued by and binding upon an
insurance company licensed or authorized to do business in the state in which the Property is located with a rating of at least “A-: X” or better as set forth in the most current issue of Best’s
Insurance Reports, unless otherwise approved by Landlord. Certificates of insurance, acceptable to Landlord, evidencing the existence and amount of each insurance policy required hereunder shall be delivered to Landlord prior to the commencement of
any work in the Premises. Further, each policy will contain provisions giving Landlord and each of the other Additional Insured Parties with at least thirty (30) days’ prior written notice of any cancelation,
non-renewal or material change in coverage. The above requirements shall apply equally to any subcontractor engaged by contractor. 

J. Tenant waives any and all rights of recovery against Landlord for or arising out of damage to or destruction of any property of Tenant to
the extent that Tenant’s property insurance policies then in force or the policies required by this Lease, whichever is broader, insure against such damage or destruction. 

5.8 Personal Property at Tenant’s Risk 

That notwithstanding anything to the contrary, all of the furnishings, fixtures, equipment, effects and property of every kind, nature and
description of Tenant and all persons claiming by, through or under Tenant which, during the continuance of this Lease or any occupancy of the 

  
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 Premises by Tenant or anyone claiming under Tenant, may be on the Premises or elsewhere in the Building or on the
Lot shall be at the sole risk and hazard of Tenant, and if the whole or any part thereof shall be destroyed or damaged by fire, water or otherwise, or by the leakage or bursting of water pipes, steam pipes, or other pipes, by theft or from any other
cause, no part of said loss or damage is to be charged to or be borne by Landlord, except that Landlord shall in no event be indemnified or held harmless or exonerated from any liability to Tenant or to any person, for any injury, loss, damage or
liability to the extent such indemnity, hold harmless or exoneration is prohibited by law. 
 5.9 Right of Entry 

To permit Landlord and its agents after reasonable notice (which may be oral) except in the case of an emergency: to examine the Premises at
reasonable times and, if Landlord shall so elect, to make any repairs or replacements Landlord may deem necessary; to remove, at Tenant’s expense, any alterations, additions, signs, curtains, blinds, shades, awnings, aerials, flagpoles, or the
like not consented to in writing (where such consent is required under the terms of this Lease); and to show the Premises to prospective tenants and to prospective purchasers and mortgagees at all reasonable times. In exercising its rights under
this paragraph, Landlord shall use reasonable efforts to avoid interference with Tenant’s business. 
 5.10 Floor Load; Prevention of Vibration and
Noise 
 Not to place a load upon the Premises exceeding an average rate of eighty (80) pounds of live load per rentable square foot
of floor area (partitions shall be considered as part of the live load); Landlord reserves the right to prescribe the weight and position of all safes, files and heavy equipment which Tenant desires to place in the Premises so as properly to
distribute the weight thereof; Tenant’s business machines and mechanical equipment which cause vibration or noise that may be transmitted to the Building structure or to any other space in the Building shall be so installed, maintained and used
by Tenant as to eliminate such vibration or noise. 
 5.11 Personal Property Taxes 

To pay promptly when due all taxes which may be imposed upon personal property (including without limitation, fixtures and equipment) in the
Premises to whomever assessed if failure to pay would result in a lien on the Property. 
 5.12 Payment of Legal Expenses 

As additional rent, to pay all reasonable costs, counsel and other fees incurred by Landlord in connection with the successful enforcement by
Landlord of any obligations of Tenant under this Lease. 
 5.13 Compliance with Insurance Regulations 

Not to do or permit to be done any act or thing upon the Premises which will invalidate or be in conflict with the terms of the Massachusetts
standard form of fire, boiler, sprinkler, water damage or other insurance policies covering the Building and the fixtures and property therein; Tenant shall, at its own expense, comply with all rules, regulations, and requirements of the 

  
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 National Board of Fire Underwriters or any state or other similar body having jurisdiction, and shall not
knowingly do or permit anything to be done in or upon the Premises in a manner which increases the rate of fire insurance upon the Building or on any property or equipment located therein. If activity, use, or occupancy by Tenant, its employees,
agents or invitees in or upon the Premises results in the increase in the rate of fire insurance upon the Building, Landlord shall bill Tenant for such excess and Tenant shall promptly pay such excess insurance costs. Notwithstanding the foregoing,
such billing by Landlord and payment by Tenant shall not waive Landlord’s right to require such activity to cease. 
 ARTICLE VI

 CASUALTY AND TAKING 
 6.1
Termination or Restoration; Rent Adjustment 
 If during the Term all or any substantial part of the Premises or the Building or the
Lot are damaged materially by fire or other casualty or by action of public or other authority in consequence thereof, or are taken by eminent domain or Landlord receives compensable damage by reason of anything lawfully done in pursuance of public
or other authority, this Lease shall terminate at Landlord’s election, which may be made notwithstanding Landlord’s entire interest may have been divested, by notice given to Tenant within forty-five (45) days after the date of
casualty or taking specifying the effective date of termination. If this Lease is not so terminated by Landlord, Landlord shall provide to Tenant in writing within forty-five (45) days after the casualty or taking the estimate from a contractor
engaged by Landlord of the cost of repair and when the Premises or the Common Areas of the Building, as the case may be, could be restored to proper condition for occupancy by Tenant. If such estimate is nine (9) months or more after the date
of the casualty or taking, or if there is a taking of fifteen (15%) per cent or more of the area of the Premises or a taking of material portions of the Building or the Property providing access to the Premises or of a material portion of the
parking areas and Tenant certifies to Landlord that the remainder of the Premises is insufficient for the operations of Tenant’s business, then Tenant may terminate this Lease by written notice to Landlord within twenty (20) days after
receipt of such estimate or the date possession of the Premises is taken, as the case may be. The effective date of termination specified by either Landlord or Tenant shall not be less than fifteen (15) nor more than thirty (30) days after
the date of notice of such termination. Unless terminated pursuant to the foregoing provisions, this Lease shall remain in full force and effect following any such damage or taking, subject, however, to the following provisions. If in any such case
the Premises are rendered unfit for use and occupancy and this Lease is not so terminated, Landlord shall use due diligence (following the expiration of the period in which Landlord or Tenant may terminate this Lease pursuant to the foregoing
provisions of this Section 6.1) to put the Premises, or in case of taking what may remain thereof (excluding in case of both casualty and taking any items installed or paid for by Tenant which Tenant may be required to remove), into proper
condition for use and occupancy (in the case of a taking to the extent permitted by the net award of damages and in the case of a casualty, to the extent of the net insurance proceeds and any retained amount), and a just proportion of the Fixed Rent
and additional rent according to the nature and extent of the injury shall be abated from the date of such casualty or taking until the Premises or such remainder shall have been put by Landlord in such condition; and in case of taking which
permanently reduces the area of the Premises, a just 

  
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 proportion of the Fixed Rent and additional rent shall be abated for the remainder of the Term. In addition, if
neither Landlord nor Tenant terminate this Lease as permitted above, and Landlord does not complete restoration of the Premises within 270 days after the date of the casualty or taking, Tenant shall have the right to terminate this Lease by written
notice to Landlord. 
 6.2 Eminent Domain Award 

Landlord reserves to itself any and all rights to receive awards made for damages to the Premises and Building and Lot and the leasehold hereby
created, or any one or more of them, accruing by reason of exercise of eminent domain or by reason of anything lawfully done in pursuance of public or other authority. Tenant hereby releases and assigns to Landlord all Tenant’s rights to such
awards, and covenants to deliver such further assignments and assurances thereof as Landlord may from to time request. Tenant hereby irrevocably designates and appoints Landlord as its
attorney-in-fact to execute and deliver in Tenant’s name and on its behalf any such further assignments thereof. Notwithstanding the foregoing, Tenant shall be
entitled to any damages for personal property of Tenant and for reasonable relocation expenses which are available to Tenant in a separate action or separate award. 

6.3 Temporary Taking 
 In the event of
taking of the Premises or any part thereof for temporary use, (i) this Lease shall be and remain unaffected thereby and rent shall not abate, and (ii) Tenant shall be entitled to receive for itself such portion or portions of any award
made for such use with respect to the period of the taking which is within the Term, provided that if such taking shall remain in force at the expiration or earlier termination of this Lease, Tenant shall then pay to Landlord a sum equal to the
reasonable cost of performing Tenant’s obligations under Section 5.2 with respect to surrender of the Premises and upon such payment shall be excused from such obligations. 

ARTICLE VII 
 DEFAULT

 7.1 Events of Default 
 If any
default, breach or failure of performance by Tenant of any agreement, covenant, condition, provision, or warranty contained herein continues, in cases of failure to pay Fixed Rent or additional rent or other payments required hereunder
(i) within five (5) days after notice from Landlord to be given no more than two (2) times in any calendar year and otherwise (ii) on the date due, or in cases other than monetary defaults continuing for more than thirty
(30) days after notice from Landlord and such additional time, if any, as is reasonably necessary to cure the default if the default is of such a nature that it cannot reasonably be cured in thirty (30) days provided Tenant commences to
cure promptly and diligently pursues the cure to completion but in no case more than ninety (90) days after notice from Landlord; or if Tenant or any guarantor or any guarantors of any of Tenant’s obligations under this Lease is not paying
its debts as such debts become due, becomes insolvent, files or has filed against it (and in the case of an involuntary petition such is not dismissed within 30 days after the filing) a petition under any chapter of the U.S. Bankruptcy Code (or any
similar petition under any insolvency law of any 

  
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 jurisdiction), proposes any dissolution, liquidation, composition, financial reorganization or recapitalization
with creditors, makes an assignment or trust mortgage for the benefit of creditors, or if a receiver, trustee, custodian or similar agent is appointed or takes possession with respect to any property or business of Tenant or such guarantor, then in
any such case, whether or not the Term shall have begun, Landlord may immediately, or at any time while such default exists and without further notice, terminate this Lease by notice to Tenant, specifying the date on which this Lease shall terminate
and this Lease shall come to an end on the date specified therein as fully and completely as if such date were the date herein originally fixed for the expiration of the Term, and Tenant shall then quit and surrender the Premises to Landlord, but
Tenant shall remain liable as hereinafter provided. 
 7.2 Landlord’s Rights and Tenant’s Obligations after Termination 

In the event that this Lease is terminated under any of the provisions contained in Section 7.1, Tenant covenants to pay forthwith to
Landlord upon demand, as compensation, the excess of the total rent reserved for the residue of the Term over the fair market rental value of the Premises for said residue of the Term (after deduction of all anticipated expenses of reletting)
discounted to present value determined by reference to The Wall Street Journal listing of “Treasury Bonds, Notes, and Bills” (representative of New York, based on transactions of $1,000,000 or more), of the yield to maturity on
issues closest to the expiration of the Term of this Lease. In calculating the rent reserved there shall be included, in addition to the Fixed Rent and all additional rent, the value of all other considerations agreed to be paid or performed by
Tenant for said residue. For purposes of clarification, Landlord shall not be obligated to wait for the original expiration of the Term of the Lease or until the Premises have been relet to exercise the foregoing remedy. Landlord may exercise such
remedy immediately upon termination of the Lease, and Tenant shall be obligated to pay the applicable damages immediately upon Landlord’s demand. In no event shall Tenant be entitled to a credit if the excess of the fair market rental value of
the Premises for the residue of the Term exceeds the total rent reserved for the residue of the Term. 
 Tenant further covenants as an
additional and cumulative obligation after any such termination to pay punctually to Landlord all the sums and perform all the obligations which Tenant covenants in this Lease to pay and to perform in the same manner and to the same extent and at
the same time as if this Lease had not been terminated. In calculating the amounts to be paid by Tenant under the foregoing covenant Tenant shall be credited with any amount paid to Landlord as compensation as in this Section 7.2 provided and
also with the net proceeds of any rent obtained by Landlord by reletting the Premises, after deducting reasonable expenses in connection with such reletting, including, without limitation, repossession costs, brokerage commissions, fees for legal
services and expenses of preparing the Premises for such reletting, it being agreed by Tenant that Landlord may (but shall have no obligation to) (i) relet the Premises or any part or parts thereof, for a term or terms which may, at
Landlord’s option, be equal to or less than or exceed the period which would otherwise have constituted the balance of the Term and may grant such concessions and free rent as Landlord in its sole judgment considers advisable or necessary to
relet the same, and (ii) make such alterations, repairs and decorations in the Premises as Landlord in its sole judgment considers advisable or necessary to relet the same, and no action of Landlord in accordance with the foregoing or failure
to relet or to collect rent under reletting shall operate or be construed to release or reduce Tenant’s liability as aforesaid. 

  
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 In no event shall Tenant be entitled to a reletting credit that exceeds the amount due to Landlord under this
Section 7.2. 
 In lieu of any other damages or indemnity and in lieu of full recovery by Landlord of all sums payable under all the
foregoing provisions of this Section 7.2, Landlord may, by written notice to Tenant, at any time after this Lease is terminated under any of the provisions contained in Section 7.1 or is otherwise terminated for breach of any obligation of
Tenant and before such full recovery, elect to recover, and Tenant shall thereupon pay, as liquidated damages, an amount equal to the aggregate of the Fixed Rent and additional rent accrued under Sections 2.6, 2.7 and 2.8 in the twelve
(12) month period immediately prior to such termination plus the amount of Fixed Rent and additional rent of any kind accrued and unpaid at the time of termination and less the amount of any recovery by Landlord under the foregoing provisions
of this Section 7.2 up to the time of payment of such liquidated damages. Landlord and Tenant acknowledge that: (i) it would be impossible or impracticable to fix the actual damages suffered by Landlord as a result of termination of this
Lease pursuant to this Section 7.2; (ii) the amount of the liquidated damages represents a fair and reasonable compensation to Landlord for such damages; and (iii) the liquidated damages set forth in this Section 7.2 do not constitute
a penalty. 
 Nothing contained in this Lease shall limit or prejudice the right of Landlord to prove for and obtain in proceedings for
bankruptcy or insolvency by reason of the termination of this Lease, an amount equal to the maximum allowed by any statute or rule of law in effect at the time when, and governing the proceedings in which, the damages are to be proved. 

ARTICLE VIII 

MISCELLANEOUS 
 8.1 Notice of Lease;
Consent and Approval; Notices; Bind and Inure 
 The titles of the Articles are for convenience only and are not to be considered in
construing this Lease. Tenant agrees not to record this Lease, but upon request of either party both parties shall execute and deliver a notice of this Lease pursuant to M.G.L. c. 183 § 4, and if this Lease is terminated before the Term
expires, an instrument in such form acknowledging the date of termination. Whenever any notice, approval, consent, request or election is given or made pursuant to this Lease it shall be in writing. Communications and payments shall be addressed if
to Landlord at Landlord’s Original Address or at such other address as may have been specified by prior notice to Tenant, and if to Tenant, at Tenant’s Original Address or after the Commencement Date at the Premises, with a copy to Foley
Hoag LLP, 155 Seaport Boulevard, Boston, MA 02210, Attn: Robert L. Birnbaum, Esq., or at such other place as may have been specified by prior notice to Landlord. Any communication so addressed shall be deemed duly given upon delivery in hand or one
(1) business day after it is sent by overnight mail or by regularly recognized overnight courier which supplies a receipt therefor, or two (2) business days after it is mailed by registered or certified mail, return receipt requested. If
Landlord by notice to Tenant at any time designates some other person to receive payments or notices, all payments or notices thereafter by Tenant shall be paid or given to the person designated until notice to the contrary is received by Tenant
from Landlord. The obligations of this Lease shall run with the land, and this Lease shall be binding upon and inure to the benefit of the parties hereto and their respective successors and assigns, subject to the limitations set forth in
Section 0. 

  
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 8.2 Landlord’s Failure to Enforce 

The failure of Landlord to seek redress for violation of, or to insist upon strict performance of, any covenant or condition of this Lease,
shall not be deemed a waiver of such violation nor prevent a subsequent act which would have originally constituted a violation, from having all the force and effect of an original violation. The receipt by Landlord of Fixed Rent or additional rent
with knowledge of the breach of any covenant of this Lease shall not be deemed a waiver of such breach. No provision of this Lease shall be deemed to have been waived by Landlord or Tenant unless such waiver is in writing signed by the party to be
charged. No consent or waiver, express or implied, by Landlord or Tenant, to or of any breach of any agreement or duty shall be construed as a waiver or consent to or of any other breach of the same or any other agreement or duty. 

8.3 Acceptance of Partial Payments of Rent; Delivery of Keys 

No acceptance by Landlord of a lesser sum than the Fixed Rent and additional rent then due shall be deemed to be other than on account of the
earliest installment of such rent due, nor shall any endorsement or statement on any check or any letter accompanying any check or payment as rent be deemed an accord and satisfaction, and Landlord may accept such check or payment without prejudice
to Landlord’s right to recover the balance of such installment or pursue any other remedy in this Lease provided. The delivery of keys to any employee of Landlord or to Landlord’s agent or any employee or other party thereof shall not
operate as a termination of this Lease or surrender of the Premises. 
 8.4 Cumulative Remedies 

The specific remedies to which Landlord may resort under the terms of this Lease are cumulative and are not intended to be exclusive of any
other remedies or means of redress to which it may be lawfully entitled in case of any breach or threatened breach by Tenant of any provisions of this Lease. In addition to other remedies provided in this Lease, Landlord shall be entitled to the
restraint by injunction of the violation or attempted or threatened violation of any of the covenants, conditions or provisions of this Lease or to a decree compelling specific performance of any such covenants, conditions or provisions. 

8.5 Partial Invalidity 
 If any term of
this Lease, or the application thereof to any person or circumstances, shall to any extent be invalid or unenforceable, the remainder of this Lease, or the application of such term to persons or circumstances other than those as to which it is
invalid or unenforceable shall not be affected thereby, and each term of this Lease shall be valid and enforceable to the fullest extent permitted by law. 

  
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 8.6 Self-Help 

If Tenant shall at any time default in the performance of any obligation under this Lease and such default shall continue for more than five
(5) days after notice from Landlord plus such additional time, if any, as is reasonably necessary (but in no event to exceed thirty (30) additional days) to cure the default if the default is of such a nature that it cannot reasonably be
cured in five (5) days provided Tenant commences to cure promptly and diligently pursues the cure to completion (except in the case of emergencies when no notice shall be required), Landlord shall have the right, but shall not be obligated, to
enter upon the Premises and to perform such obligation notwithstanding the fact that no specific provision for such substituted performance by Landlord is made in this Lease with respect to such default. In performing such obligation, Landlord may
make any payment of money or perform any other act. All sums so paid by Landlord (together with interest at the rate of two and one-half (2.5%) percentage points over the then prevailing prime rate as
published in The Wall Street Journal) and all necessary incidental costs and expenses in connection with the performance of any such act by Landlord, shall be deemed to be additional rent under this Lease and shall be payable to Landlord
immediately on demand. Landlord may exercise the foregoing rights without waiving any other of its rights or releasing Tenant from any of its obligations under this Lease. 

8.7 Estoppel Certificate 
 Each party
agrees from time to time, upon not less than fifteen (15) business days’ prior written request by the other party, to execute, acknowledge and deliver to the requesting party a statement in writing certifying, to the extent the same are
accurate, that this Lease is unmodified and in full force and effect and that there are no uncured defaults of Landlord or Tenant under this Lease, and if Landlord is the requesting party that Tenant has no defenses, offsets or counterclaims against
its obligations to pay the Fixed Rent and additional rent and to perform its other covenants under this Lease (or, if there have been any modifications that the same is in full force and effect as modified and stating the modifications and, if there
are any defenses, offsets, counterclaims, or defaults, setting them forth in reasonable detail), the dates to which the Fixed Rent, additional rent and other charges have been paid and such other matters relating to the Lease as may be reasonably
requested. Any such statement delivered pursuant to this Section 8.7 may be relied upon by a prospective purchaser or mortgagee of the Property or any prospective assignee of any mortgagee of the Property, or by a prospective assignee of
Tenant’s interest in this Lease, as the case may be. 
 8.8 Waiver of Subrogation 

Any property damage insurance carried by either party with respect to the Premises or property therein shall include a clause or endorsement
denying to the insurer rights of subrogation against the other party. Each party, notwithstanding any provisions of this Lease to the contrary, hereby waives any rights of recovery against the other for injury or loss due to hazards covered by such
insurance to the extent of the indemnification received thereunder. 

  
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 8.9 All Agreements Contained; Independent Covenants; Construction 

This Lease contains all of the agreements of the parties with respect to the subject matter thereof and supersedes all prior dealings between
them with respect to such subject matter. Each term, covenant, agreement, obligation or other provision of this Lease on Tenant’s part to be performed shall be deemed and construed as a separate and independent covenant of Tenant, not dependent
upon any of the other terms of this Lease. This Lease shall be construed without regard to any presumption or other rule requiring construction against the party causing this Lease to be drafted. 

8.10 Brokerage 
 Each party represents
that it has had no dealings with any broker or agent other than the Broker(s) identified in Section 1.2 in connection with this Lease and covenants to defend, hold harmless and indemnify the other party and its agents from and against any and
all cost, expense or liability resulting from a breach of the foregoing representation. Landlord will pay the commissions due the aforesaid Broker in accordance with separate commission agreements. 

8.11 Submission Not an Option 
 The
submission of this Lease or a summary of some or all of its provisions for examination does not constitute a reservation of or option for the Premises or an offer to lease, and it is not effective as a lease or otherwise until the execution by and
delivery to both Landlord and Tenant. 
 8.12 Applicable Law 

This Lease, and the rights and obligations of the parties hereto, shall be construed and enforced in accordance with the laws of the
Commonwealth of Massachusetts. 
 8.13 Waiver of Jury Trial 

LANDLORD AND TENANT HEREBY WAIVE TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM BROUGHT BY EITHER OF THE PARTIES HERETO AGAINST THE
OTHER, ON OR IN RESPECT TO ANY MATTER WHATSOEVER ARISING OUT OF OR IN ANY WAY CONNECTED WITH THIS LEASE, THE RELATIONSHIP OF LANDLORD AND TENANT HEREUNDER, TENANT’S USE OR OCCUPANCY OF THE PREMISES, AND/OR CLAIM OF INJURY OR DAMAGES. 

8.14 Access and Security 
 Tenant shall
have access to the Premises at all times during the Term of this Lease, except in the event of an emergency or for safety precautions. The Building is accessed by an automated card key system. Landlord may require that parties desiring to enter the
Building after regular office hours must provide proper identification. Tenant shall be responsible for any security required for Tenant’s property in or around the Premises, including, but not limited to, the loading area. In connection with
the foregoing, Tenant shall have the right, subject to the prior written consent of Landlord, to install a security system for Premises at Tenant’s sole cost and expense. 

  
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 8.15 Holdover 

Should Tenant holdover in occupancy of the Premises after the expiration or other termination of the Term of this Lease, without the consent of
Landlord, such holding over shall be as a tenant at sufferance and Tenant shall be liable to Landlord for (i) use and occupancy equal to the greater of one hundred and fifty percent (150%) percent of then-current market value rent or the Fixed
Rent and additional rent in effect at the end of the Term, for the first month during such holding over, (ii) use and occupancy equal to the greater of two hundred percent (200%) percent of then-current market value rent or the Fixed Rent and
additional rent in effect at the end of the Term, for each month after the first month of such holding over, and (iii) all damages sustained by Landlord on account of such holding over. The provisions of this Section shall not operate as a
waiver of any right of reentry provided in this Lease. 
 8.16 Limitation on Liability 

In consideration of the benefits accruing hereunder, Tenant hereby covenants and agrees that, in the event of any actual or alleged failure,
breach or default hereunder by Landlord: 
 (a) The obligations of Landlord under this Lease do not constitute personal obligations of the
members, trustees, individual partners, directors, officers or shareholders of Landlord or any constituent entity of Landlord, and Tenant shall not seek recourse against the members, trustees, partners, directors, officers or shareholders of
Landlord or any constituent entity of Landlord, or any of their personal assets for satisfaction of any liability with respect to this Lease. 

(b) Tenant’s sole and exclusive remedy shall be against Landlord’s interest in the Property. 

(c) These covenants and agreements are enforceable by Landlord, and shall bind Tenant and its successors and assigns. 

8.17 Security Deposit 
 On or prior to the
date hereof, Tenant shall provide Landlord with a letter of credit in form and substance satisfactory to Landlord and from a financial institution satisfactory to Landlord in its reasonable judgment in the original amount of $77,163.25. Tenant shall
maintain such letter of credit until the date that is forty-five (45) days after expiration of the Term. Tenant may reduce the security deposit to $51,442.17 on the first anniversary of the Rent Commencement Date, provided that no defaults have
occurred under this Lease beyond applicable notice and grace periods, and further provided that upon any default by Tenant under the Lease beyond applicable notice and grace periods (even if occurring following such reduction), Tenant shall restore
any amount of the letter of credit drawn by the Landlord on account of such default and increase the letter of credit to its original amount of $77,163.25 for the duration of the Term of the Lease. Such letter of credit may be drawn from time to
time by Landlord upon Tenant’s default of its obligations under this Lease beyond applicable notice and 

  
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 grace periods, or if such letter of credit is about to expire and has not been renewed within thirty (30) days
preceding such expiration. Should Landlord draw down the letter of credit, Tenant shall be obligated to restore it to its original amount. Landlord may assign the security deposit to a successor or transferee and, following the assignment, Landlord
shall have no further liability with respect to the security deposit. If the letter of credit is drawn down and held by Landlord as a cash security deposit, Landlord (i) shall not be required to keep the security deposit separate from its other
accounts, and (ii) shall return any unapplied portion of the security deposit to Tenant within forty-five (45) days after the later to occur of the expiration of the Term or the date Tenant surrenders the Premises to Landlord in compliance
with Section 5.2. 
 8.18 Representations 

Tenant guarantees, warrants and represents that (a) Tenant is duly incorporated or otherwise established or formed and validly existing
under the laws of its state of incorporation, establishment or formation, (b)Tenant has and is duly qualified to do business in the state in which the Property is located, (c) Tenant has full corporate, partnership, trust, association or other
appropriate power and authority to enter into this Lease and to perform all Tenant’s obligations hereunder, (d) each person (and all of the persons if more than one signs) signing this Lease on behalf of Tenant is duly and validly
authorized to do so and (e) neither (i) the execution, delivery or performance of this Lease nor (ii) the consummation of the transactions contemplated hereby will violate or conflict with any provision of documents or instruments under
which Tenant is constituted or to which Tenant is a party. 
 Tenant guarantees, warrants and represents that none of (x) it, or
(y) to the best of its actual knowledge, its affiliates, partners, members, shareholders or other equity owners or any of their respective employees, officers, directors, representatives or agents is a person or entity with whom U.S. persons or
entities are restricted from doing business under regulations of the Office of Foreign Asset Control (“OFAC”) of the Department of the Treasury (including those named on OFAC’s Specially Designated and Blocked Persons
List) or under any statute, executive order (including the September 24, 2001, Executive Order Blocking Property and Prohibiting Transactions with Persons Who Commit, Threaten to Commit, or Support Terrorism) or other similar governmental
action. 
 ARTICLE IX 

RIGHTS OF PARTIES HOLDING PRIOR INTERESTS 

9.1 Lease Subordinate 
 This Lease shall
be subject and subordinate to any mortgage now or hereafter on the Property, and to each advance made or hereafter to be made under any mortgage, and to all renewals, modifications, consolidations, replacements and extensions thereof and all
substitutions therefor. Landlord represents that the Property is not presently encumbered by a mortgage. Tenant’s obligation to subordinate this Lease to a future mortgage is expressly conditioned upon Tenant receiving from the holder thereof
an agreement with Tenant in such holder’s standard form by the terms of which such holder will agree to recognize the rights of Tenant under this Lease and to accept Tenant as tenant of the Premises under the terms and 

  
 - 30 - 

 conditions of this Lease in the event of acquisition of title by such holder through foreclosure proceedings or
otherwise and Tenant will agree to recognize and attorn to the holder of such mortgage as Landlord in such event, which agreement shall be made expressly to bind and inure to the benefit of the successors and assigns of Tenant and of the holder and
upon anyone purchasing the Premises at any foreclosure sale. Notwithstanding the foregoing, any such holder may at its election subordinate its mortgage to this Lease without the consent or approval of Tenant. Tenant agrees to execute and deliver
any appropriate instruments containing terms and provisions commonly contained in such instruments necessary to carry out the agreements contained in this Section 9.1. 

9.2 Rights of Holder of Mortgage to Notice of Defaults by Landlord and to Cure Same 

No act or failure to act on the part of Landlord which would entitle Tenant under the terms of this Lease, or by law, to be relieved of
Tenant’s obligations hereunder or to terminate this Lease, shall result in a release or termination of such obligations or a termination of this Lease unless (i) Tenant shall have first given written notice of Landlord’s act or
failure to act to Landlord’s mortgagees of record of whom Landlord has given Tenant notice, if any, specifying the act or failure to act on the part of Landlord which could or would give basis to Tenant’s rights; and (ii) such
mortgagees after receipt of such notice, have failed or refused to correct or cure the condition complained of within a reasonable time thereafter; but nothing contained in this Section 9.2 shall be deemed to impose any obligation on any such
mortgagees to correct or cure any condition. “Reasonable time” as used above means and includes a reasonable time to obtain possession of the mortgaged premises if the mortgagee elects to do so and a reasonable time to correct or cure the
condition if such condition is determined to exist. 
 [Signatures on following page] 

  
 - 31 - 

 EXECUTED as a sealed instrument in two or more counterparts on the day first above written. 

 

	
	LANDLORD:
	
	WALTHAM WINTER STREET 890 LP, a
	Delaware limited partnership, doing business in Massachusetts as Waltham Winter Street 890 Limited Partnership
	
	By: Waltham Sub GP LLC, a Delaware limited         liability company, its General Partner
	
	          By: Clarion Partners, LLC, a New York
	                  limited liability company, its Manager
	
	                By: /s/ Brian
Collins                            
	                Name: Brian Collins
	                Title: Authorized Signatory
	
	TENANT:
	
	                ARSANSIS, INC., a Delaware corporation:
	
	                By: /s/ Noah
Oshry                            
	                Name: Noah Oshry
	                Title: Executive Director – U.S. Business Operations

 Signature Page to Lease 

S-1 

 EXHIBIT A 

Property Description 
 That certain parcel of
land situate in the City of Waltham in the County of Middlesex, Commonwealth of Massachusetts, described as follows: 
 Parcel 1: 

Lot 3 as shown on Land Court Plan No. 30618C. 
 Parcel 2: 

Lot N as shown on plan entitled “Plan of Land in Waltham, Massachusetts prepared for 880 Winter Street, L.L.C. and 890 Winter Street, L.L.C.” dated
May 19, 1998 by Martinage Engineering Associates, Inc. and recorded with the Middlesex South District Registry of Deeds as Plan No. 734 of 1998. 

  
 A-1 

 EXHIBIT B 

Floor Plan 
 [TO BE ATTACHED] 

  
 B-1 

 EXHIBIT C 

[RESERVED] 

  
 C-1 

 EXHIBIT D 

Landlord’s Services 
  

	I.	Cleaning 

 A. Office Area 

Daily on Business Days: 
  

	 	1.	Empty and clean all waste receptacles and ash trays and remove waste material from the Premises; wash receptacles as necessary. 

  

	 	2.	Sweep and dust mop all non-carpeted areas. 

  

	 	3.	Vacuum all rugs and carpeted areas. 

  

	 	4.	Hand dust and wipe clean with treated cloths all horizontal surfaces including furniture, office equipment, window sills, door ledges, chair rails, and convector tops, within normal reach. 

 

	 	5.	Wash clean all water fountains. 

  

	 	6.	Remove and dust under all desk equipment and telephones and replace same. 

  

	 	7.	Wipe clean all brass and other bright work. 

  

	 	8.	Hand dust all grill work within normal reach. 

  

	 	9.	Upon completion of cleaning, all lights will be turned off and doors locked, leaving the Premises in an orderly condition 

Weekly: 
  

	 	1.	Dust coat racks and the like. 

  

	 	2.	Remove all finger marks from private entrance doors, light switches and doorways. 

  

	 	3.	Clean all interior glass, including sidelights and conference room glass walls. 

 Monthly: 

 

	 	4.	All vinyl floor surfaces will be cleaned 

 Quarterly: 

Render high dusting not reached in daily cleaning to include: 
  

	 	5.	Dusting all pictures, frames, charts, graphs and similar wall hangings. 

  

	 	6.	Dusting all pipes, ducts and high moldings. 

  

	 	7.	Dusting all venetian blinds. 

  

	 	B.	Lavatories 

 Daily on Business Days: 

  
 D-1 

	 	1.	Sweep and damp mop floors. 

  

	 	2.	Clean all mirrors, powder shelves, dispensers and receptacles, bright work, flushometers, piping and toilet seat hinges. 

  

	 	3.	Wash both sides of toilet seats. 

  

	 	4.	Wash all basins, bowls and urinals. 

  

	 	5.	Dust and clean all powder room fixtures. 

  

	 	6.	Empty and clean paper towel and sanitary disposal receptacles. 

  

	 	7.	Remove waste paper and refuse. 

  

	 	8.	Refill tissue holders, soap dispensers, towel dispensers, vending sanitary dispensers; materials to be furnished by Landlord. 

  

	 	9.	A sanitizing solution will be used in all lavatory cleaning. 

 Monthly: 

 

	 	10.	Machines scrub lavatory floors. 

  

	 	11.	Wash all partitions and tile walls in lavatories. 

  

	 	C.	Main Lobby, Elevators, Building Exterior and Corridors 

 Daily on Business Days:

  

	 	1.	Sweep and wash all floors. 

  

	 	2.	Wash all rubber mats. 

  

	 	3.	Clean elevators, wash or vacuum floors, wipe down walls and corridors. 

  

	 	4.	Spot clean any metal work inside lobby. 

  

	 	5.	Spot clean any metal work surrounding Building entrance doors. 

  

	 	6.	Clean glass, where appropriate. 

 Monthly: 

All resilient tile floors in public areas to be treated equivalent to spray buffing. 

As Needed: 
 Ash urns in Building
exterior. 
  

	 	D.	Exterior Windows  

 Biannually: 

Wash exterior windows. 
  

	II.	Heating, Ventilating and Air Conditioning 

  
 D-2 

 A. Heating, ventilating, and air conditioning (“HVAC”) as required to provide
reasonably comfortable temperatures for normal business day occupancy (excepting holidays); Mondays through Fridays from 8:00 am to 6:00 pm and 9 am to 1 pm on Saturdays, provided that as part of Landlord’s environmental commitment, Saturday
morning’s HVAC services are provided only as requested by each tenant of the Building. HVAC provided during days or hours other than those described herein shall be provided to Tenant at the rate established by Landlord, currently $60 per hour.

 B. Maintenance and use of any additional or special air conditioning equipment and the associated operating cost will be at Tenant’s
expense. A 24-hour notice is needed to program additional comfort. 
 C. Holidays are defined for all
purposes of this Lease, as the following days: New Year’s Day, Martin Luther King Day, President’s Day, Patriot’s Day, Memorial Day, Independence Day, Labor Day, Columbus Day, Veteran’s Day, Thanksgiving Day and Christmas, and
other days defined as “legal holidays” for the entire state under the laws of the Commonwealth of Massachusetts. 
 III. Water 

Hot and cold water, in reasonable quantities, for lavatory, pantry, drinking and toilet purposes. 

IV. Elevators (Passenger and Freight) 
 A.
Passenger: Elevators for the use of all tenants and the general public for access to and from all floors of the Building. 
 B.
Freight: Elevators for use by all tenant deliveries for access to and from all floors of the Building. 
 C. Building
Directory: Landlord will furnish and install Building Directory tablets, at Landlord’s expense, and the number of listings thereon for Tenant and any permitted occupants of the Premises shall be at the discretion of Landlord. 

V. Electricity 
 A. Electricity to the
Premises as set forth in Section 2.9 of the Lease. Tenant’s use of electric energy in Tenant’s Space shall not at any time exceed the capacity of any of the 

electrical conductors or equipment in or otherwise serving Tenant’s Space. In order to ensure that such capacity is not exceeded and to
avert possible adverse effect upon the Building electric service, Tenant shall not, without prior written notice to Landlord in each instance, connect to the Building electric distribution system any fixtures, appliance or equipment which operate on
a voltage in excess of 120 volts nominal or make any material alteration or addition to the electrical system of Tenant’s Space. All additional risers or other equipment required by Tenant shall be provided by Landlord and the cost thereof
shall be paid by Tenant upon Landlord’s demand. 
 B. Lighting of the parking areas, walkways, Building entrance, lobbies, elevators and
other common areas of the Building. 

  
 D-3 

 VI. Lot. 

A. Snow and ice removal from the driveways, parking areas, walkways and Building entrance. 

B. Landscaping consistent with a first-class office park in the Route 128 West Office market. 

  
 D-4 

 EXHIBIT E 

Landlord’s Rules and Regulations 
 I. The following
regulations are generally applicable: 
 1. The public sidewalks, entrances, passages, courts, elevators, vestibules, stairways, corridors or
halls shall not be obstructed or encumbered by Tenant (except as necessary for deliveries) or used for any purpose other than ingress and egress to and from the Premises. 

2. Landlord shall furnish Building standard blinds for all exterior windows. No awnings, curtains, blinds, shades, screens or other projections
shall be attached to or hung in, or used in connection with, any exterior window of the Premises or any outside wall of the Building. Such awnings, curtains, blinds, shades, screens or other projections must be of a quality, type, design and color,
and attached in the manner, approved by Landlord. 
 3. No show cases or other articles shall be put in front of or affixed to any part of
the exterior of the Building, nor placed in the halls, corridors or vestibules. 
 4. The water and wash closets and other plumbing fixtures
shall not be used for any purposes other than those for which they were designed and constructed, and no sweepings, rubbish, rags, acids or like substances shall be deposited therein. All damages resulting from any misuse of the fixtures by Tenant
shall be borne by the Tenant. 
 5. Tenant shall not use the Premises or any part thereof, or permit the Premises or any part thereof to be
used, for manufacturing. Tenant shall not use the Premises or any part thereof or permit the Premises or any part thereof to be used as a public employment bureau or for the sale of property of any kind at auction, except in connection with
Tenant’s business. 
 6. Tenant must upon the termination of its tenancy, restore to the Landlord all locks, cylinders and keys to
offices and toilet rooms of the Premises. 
 7. The Landlord reserves the right to exclude from the Building between the hours of 6 p.m. and
8 a.m. and at all hours on Sunday and holidays all persons connected with or calling upon the Tenant who do not present a pass to the Building signed by the Tenant. Tenant shall be responsible for all persons for whom it issues any such pass and
shall be liable to the Landlord for all wrongful acts of such persons. 
 8. The requirements of Tenant will be attended to only upon
application at the Building Superintendent’s Office. Employees of Landlord shall not perform any work or do anything outside of their regular duties, unless under special instructions from the office of the Landlord. 

9. There shall not be used in any space, or in the public halls of the Building, either by Tenant or by jobbers or others, in the delivery or
receipt of merchandise, any hand trucks, except those equipped with rubber tires and side guards. 

  
 E-1 

 10. No bicycles, vehicles or animals of any kind shall be brought into or kept in or about the
Premises, except guide dogs where necessary. 
 11. No Tenant shall make, or permit to be made, any unseemly or disturbing noises or disturb
or interfere with occupants of this or neighboring building or premises or those having business with them whether by use of any musical instrument, radio, talking machine, unmusical noise, whistling, singing, or in any other way. No Tenant shall
throw anything out of the doors, windows or skylights or down the passageways. 
 12. The Premises shall not be used for lodging or sleeping
or for any immoral or illegal purpose. 
 13. No smoking shall be permitted in the Premises or the Building. Smoking shall only be permitted
in smoking areas outside of the Building which have been designated by the Landlord. 
 14. Tenants shall reasonably cooperate with Landlord
in obtaining maximum effectiveness of the cooling system by closing draperies when the sun’s rays fall directly on the windows of the Premises. 

15. Landlord shall have the right, exercisable without notice and without liability to any tenant, to change the name and street address of the
Building. Landlord shall promptly notify Tenant after any such changes have been made. 
 16. Any person desiring to use the health and
fitness facility shall first execute and deliver to the Landlord a liability waiver form prepared by the Landlord. 
  

	II.	The following regulations are applicable to any additions, alterations or improvements being undertaken by or for Tenant in the Premises: 

A. General 
 1. All
alterations to be made by Tenant in, to or about the Premises shall be subject to Landlord’s prior written approval and made in accordance with the requirements of this Exhibit and by contractors, subcontractors and/or mechanics approved by
Landlord, such approval not be unreasonably withheld or delayed; provided, however, Landlord’s consent shall not be required for alterations of a cosmetic nature (such as painting, carpeting, wall papering). 

2. Tenant shall, prior to the commencement of any work, submit for Landlord’s written approval, complete plans for the alterations except
that no plans or drawings shall be required for cosmetic alterations (such as painting, carpeting, wall papering). Drawings are to be complete with full details and specifications for all of the alterations. 

3. Alterations must comply with the Building Code applicable to the Property and the requirements, rules and regulations of any governmental
agencies having jurisdiction over the Property. 

  
 E-2 

 4. No work shall be permitted to commence without the Landlord being furnished with a valid
permit and all other necessary approvals from agencies having jurisdiction. 
 5. All demolition, removals or other categories of work that
may inconvenience other tenants or disturb Building operations, must be scheduled and performed before or after normal Business Hours and Tenant shall provide the Building manager with at least 24 hours’ notice prior to proceeding with such
work. 
 6. All inquiries, submissions, approvals and all other matters regarding alterations to the Premises shall be processed through the
Building manager. 
 B. Prior to Commencement of Work 

1. Tenant shall submit to the Building manager a request to perform the work. The request shall include the following enclosures: 

 

	 	(i)	A list of Tenant’s contractors and/or subcontractors for Landlord’s approval. 

  

	 	(ii)	Where appropriate, four complete sets of plans and specifications properly stamped by a registered architect or professional engineer. 

 

	 	(iii)	A properly executed building permit application form. 

  

	 	(iv)	Four executed copies of the Insurance Requirements agreement in the form attached to this Lease as Exhibit F from Tenant’s contractor and if requested by Landlord from the contractor’s subcontractors.

  

	 	(v)	Contractor’s and subcontractor’s insurance certificates including an indemnity in accordance with the Insurance Requirements agreement. 

 

	 	2.	Landlord will return the following to Tenant: 

  

	 	(i)	Two sets of plans approved or a disapproval with specific comments as to the reasons therefor (such approval or comments shall not constitute a waiver of approval of governmental agencies) along with Landlord’s
response to Tenant’s request for identification of alterations that will be required to be removed at the expiration of the Term, as more fully provided in Section 5.2 of the Lease. 

 

	 	(ii)	Two fully executed copies of the Insurance Requirements agreement. 

 3. Tenant shall obtain a
building permit from the Building Department and necessary permits from other governmental agencies. Tenant shall be responsible for keeping current all permits. Tenant shall submit copies of all approved plans and permits to Landlord and shall post
the original permit on the Premises prior to the commencement of any work. All work, if performed by a contractor or subcontractor, shall be subject to reasonable supervision and inspection by Landlord’s Construction Representative. Such
supervision and inspection shall be at Tenant’s sole expense and Tenant shall pay Landlord’s reasonable charges for such supervision and inspection. 

C. Requirements and Procedures 

  
 E-3 

 1. All structural and floor loading requirements shall be subject to the prior approval of
Landlord’s structural engineer. 
 2. All mechanical (HVAC, plumbing and sprinkler) and electrical requirements shall be subject to the
approval of Landlord’s mechanical and electrical engineers and all mechanical and electrical work shall be performed by contractors approved by Landlord, which approval shall not be unreasonably withheld or delayed. When necessary, Landlord
will require engineering and shop drawings, which drawings must be approved by Landlord before work is started, not to be unreasonably withheld or delayed. Drawings are to be prepared by Tenant and all approvals shall be obtained by Tenant. 

3. Elevator service for construction work shall be without charge to Tenant. Prior arrangements for elevator use shall be made with Building
manager by Tenant. No material or equipment shall be carried under or on top of elevators. If an operating engineer is required by any union regulations, such engineer shall be paid for by Tenant. 

4. If shutdown of risers and mains for electrical, HVAC, sprinkler and plumbing work is required, such work shall be supervised by
Landlord’s Construction Representative. No work will be performed in Building mechanical equipment rooms without Landlord’s approval and under Landlord’s supervision. 

5. Tenant’s contractor shall: 
  

	 	(i)	have a superintendent or foreman on the Premises at all times that construction is active; 

  

	 	(ii)	police the job at all times, continually keeping the Premises orderly; 

  

	 	(iii)	maintain cleanliness and protection of all areas, including elevators and lobbies; 

  

	 	(iv)	protect the front and top of all peripheral HVAC units and thoroughly clean them at the completion of work; 

  

	 	(v)	block off supply and return grills, diffusers and ducts to keep dust from entering into the Building air conditioning system; and 

  

	 	(vi)	avoid the disturbance of other tenants. 

 6. If Tenant’s contractor is negligent in any of
its responsibilities, Tenant shall be charged for corrective work. 
 7. All equipment and installations must be equal to the standards
generally in effect with respect to the remainder of the Building. Any deviation from such standards will be permitted only if indicated or specified on the plans and specifications and approved by Landlord. 

8. A properly executed air balancing report signed by a professional engineer shall be submitted to landlord upon the completion of all HVAC
work. 

  
 E-4 

 9. Upon completion of the alterations, Tenant shall submit to Landlord a permanent certificate of
occupancy and final approval by the other governmental agencies having jurisdiction, where required. 
 10. Where appropriate, Tenant shall
submit to Landlord a final “as-built” set of drawings showing all items of the alterations in full detail. 

11. Additional and differing provisions in the Lease, if any, will be applicable and will take precedence. 

 

	III.	The following regulations shall be effective with respect to any plans or specifications that Tenant is required to prepare under the Lease: 

Whenever Tenant shall be required by the terms of the Lease to submit plans to Landlord in connection with any improvement or alteration to
the Premises, such plans shall include at least the following: 
 1. Floor plan indicating location of partitions and doors (details required
of partition and door types). 
 2. Location of standard electrical convenience outlets and telephone outlets. 

3. Location and details of special electrical outlets: e.g., photocopiers, etc. 

4. Reflected ceiling plan showing layout of standard ceiling and lighting fixtures. Partitions to be shown lightly with switches located
indicating fixtures to be controlled. 
 5. Locations and details of special ceiling conditions, lighting fixtures, speakers, etc. 

6. Location and specifications of floor covering, paint, or paneling with paint colors referenced to standard color system. 

7. Finish schedule plan indicating wall covering, paint, or paneling with paint colors referenced to standard color system. 

8. Details and specifications of special millwork, glass partitions, rolling doors and grilles, blackboards, shelves, etc. 

9. Hardware schedule indicating door number keyed to plan, size, hardware required including butts, latchsets or locksets, closures, stops and
any special items such as thresholds, soundproofing, etc. Keying schedule is required. 
 10. Verified dimensions of all built-in equipment (file cabinets, lockers, plan files, etc.) 
 11. Location and weights of storage files.

 12. Location of any special soundproofing requirements. 

  
 E-5 

 13. Location and details of special floor areas exceeding 50 pounds of live load per square foot.

 14. All structural, mechanical, plumbing and electrical drawings, to be prepared by the base building consulting engineers, necessary to
complete the Premises in accordance with Tenant’s plans. 
 15. All drawings to be uniform size (30’ x 46’) and shall
incorporate the standard project electrical and plumbing symbols and be at a scale of 1/8” = 1’ or larger. 
 16. All drawings
shall be stamped by an architect (or, where applicable, an engineer) licensed in the jurisdiction in which the Property is located and without limiting the foregoing, shall be sufficient in all respects for submission to applicable governmental
authorities in connection with a building permit application. 
 17. Landlord’s approval of the plans, drawings, specifications or other
submissions in respect of any work, addition, alteration or improvement to be undertaken by or on behalf of Tenant shall create no liability or responsibility on the part of Landlord for their completeness, design sufficiency or compliance with
requirements of any applicable laws, rules or regulations of any governmental or quasi-governmental agency, board or authority. 

  
 E-6 

 EXHIBIT F 

CONTRACTOR’S INSURANCE 
 Building:
890 Winter Street, Waltham, MA 
 Tenant:
                                        
         
 Premises:
                     Rentable Square Feet of Space in the Building. 

The undersigned contractor or subcontractor (“Contractor”) has been hired by the tenant or occupant (hereinafter called
“Tenant”) of the Building named above or by Tenant’s contractor to perform certain work (“Work”) for Tenant in the Premises identified above. Contractor and Tenant have requested the undersigned
landlord (“Landlord”) to grant Contractor access to the Building and its facilities in connection with the performance of the Work and Landlord agrees to grant such access to Contractor upon and subject to the following terms
and conditions: 
 1. Contractor agrees to indemnify and save harmless the Landlord, Landlord’s affiliates and their respective officers, employees,
agents, members and partners and each of them, from and with respect to any claims, demands, suits, liabilities, losses and expenses, including reasonable attorneys’ fees, arising out of or in connection with the Work (and/or imposed by law
upon any or all of them) because of personal injuries, bodily injury (including death at any time resulting therefrom) and loss of or damage to property, whether such injuries to person or property are claimed to be due to negligence of the
Contractor, Tenant, Landlord or any other party entitled to be indemnified as aforesaid except to the extent specifically prohibited by law (and any such prohibition shall not void this Agreement but shall be applied only to the minimum extent
required by law). 
 2. Contractor shall provide and maintain at its own expense, until completion of the Work, the following insurance: 

 

	(a)	Worker’s Compensation (including coverage for Occupational Disease) and Employers Liability Insurance covering each and every workman employed in, about or upon the Work, as provided for in each and every statute
applicable to Workmen’s Compensation and Employers’ Liability Insurance. 

  

	(b)	Comprehensive General Liability Insurance including coverages for Protective and Contractual liability (to specifically include coverage for the indemnification clause of this Agreement) for not less than the following
limits: 

  

	(c)	Personal Injury: $3,000,000 per person, $5,000,000 per occurrence 

  

	(d)	Property Damage: $3,000,000 per occurrence $3,000,000 aggregate 

  
 F-1 

	(e)	Comprehensive Automobile Liability Insurance (covering all owned, non-owned and/or hired motor vehicles to be used in connection with the Work) for not less than the following
limits: 

  

	 	(i)	Bodily Injury: $1,000,000 per person, $1,000,000 per occurrence 

  

	 	(ii)	Property Damage: $1,000,000 per occurrence 

  

	(f)	Contractor shall furnish a certified from its insurance carrier or carriers to the Building office before commencing the Work, showing that it has complied with the above requirements regarding insurance and providing
that the insurer will endeavor to give Landlord ten (10) days’ prior written notice of the cancellation of any of the foregoing policies. 

  

	(g)	Contractor shall require all of its subcontractors engaged in the Work to provide the following insurance: 

  

	 	(i)	Comprehensive General Liability Insurance including Protective and Contractual Liability coverages with limits of liability at least equal to the limits stated in paragraph 2(b). 

 

	 	(ii)	Comprehensive Automobile Liability Insurance (covering all owned, non-owned and/or hired motor vehicles to be used in connection with the Work) with limits of liability at least
equal to the limits stated in paragraph 2(c). 

 [Remainder of Page Left Blank Intentionally] 

  
 F-2 

 Upon the request of Landlord, Contractor shall require all of its subcontractors engaged in the
Work to execute an Insurance Requirements Agreement in the same form as this Agreement. 
 Agreed to and executed this
                 day of                     , 20 . 

 

					
	LANDLORD:	 		 	
	
	Waltham Winter Street 890 LP, a Delaware limited partnership

 
					
		
	By:	 	Waltham Winter Street LLC, a Delaware limited liability company, its General Partner
		
		 	By: Clarion Partners LLC, a New York limited       liability company, its Manager
		
		 	
       By:                  
                                       

              Name:

		 	              Title:
		 		 	

  

			
	CONTRACTOR:
	
	  

		
	By:	 	  

		 	Name:
		 	Title:

  
 F-3

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