Document:

EX-4.3

 Exhibit 4.3 

COMMON STOCK WARRANT 

THIS WARRANT AND THE SHARES OF COMMON STOCK WHICH MAY BE PURCHASED PURSUANT TO THE EXERCISE OF THIS WARRANT HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), AND NEITHER SUCH SECURITIES NOR ANY INTEREST THEREIN MAY BE SOLD, TRANSFERRED, PLEDGED OR OTHERWISE DISPOSED OF IN THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION UNDER THE ACT AND THE
RULES AND REGULATIONS THEREUNDER. 
  

			
	No. [    ]	  	Void After Expiration Date
		  	(as defined below)

 WARRANT 

TO PURCHASE [            ] SHARES OF COMMON STOCK OF TCR2 THERAPEUTICS INC. 
 Dated: [    ] (the “Warrant Date”)

 THIS WARRANT CERTIFIES THAT, for value received, [            ] (the
“Holder”) is entitled to purchase from TCR2 Therapeutics Inc., a Delaware corporation (the “Company”), up to
[            ] fully paid and nonassessable shares (the “Shares”) (as adjusted pursuant to Section 2 below) of Common Stock, $0.0001 par value (“Common Stock”), of
the Company, at the price of $[            ] per share (the “Exercise Price”) (as adjusted pursuant to Section 2 below), subject to the provisions and upon the terms and
conditions set forth below. This Warrant shall expire on [            ] (the “Expiration Date”). 

1. Exercise and Payment. 

(a) Exercise. This Warrant shall not be exercisable by Holder at any time except pursuant to Section 1(c). Subject to
Section 1(c), on or after the date of this Warrant, the purchase rights represented by this Warrant may be exercised by the Holder, in whole or in part, by the surrender of this Warrant (together with a duly executed exercise notice (the
“Notice of Exercise”) in the form attached hereto as Exhibit A) at the principal office of the Company, and by the payment to the Company, by wire transfer, of an amount equal to the aggregate Exercise Price of the Shares
being purchased. 

 (b) Stock Certificates. In the event of the exercise of all or any
portion of this Warrant, certificates for the shares of Common Stock so purchased shall be delivered to the Holder by the Company at its own expense (including the payment by the Company of any applicable issue taxes or governmental charges imposed
in connection with the issuance or delivery of the Common Stock) within a reasonable time, which shall in no event be later than ten (10) days thereafter and, unless this Warrant has been fully exercised or has expired, a new Warrant
representing the Shares with respect to which this Warrant shall not have been exercised shall also be issued to the Holder within such time. 

(c) Vesting. 
 (i) This
Warrant shall be immediately exercisable, regardless of whether the Shares are vested. 
 (ii) All of the Shares shall be deemed to be
unvested as of the Warrant Date. Except as otherwise set forth herein, and subject to the determination of the Board of Directors of the Company in its sole discretion to accelerate the vesting schedule hereunder, the Shares shall vest in 36 equal
monthly installments following [_____], until [_____], on which date, subject to the vesting conditions herein, all remaining Shares shall vest. Notwithstanding anything in the Warrant to the contrary, in the case of a Change of Control, the Warrant
and the Shares shall be treated as provided in Section 3 herein. 
 (iii) To the extent this Warrant is only partially exercised, such
exercise shall first be with respect to the Shares, if any, that have previously vested, and then with respect to the Shares that will next vest, with the Shares that vest at the latest date being exercised last. 

(iv) In the event that the Holder exercises a portion of this Warrant with respect to Shares that have not vested, the Holder shall also
deliver a Restricted Stock Agreement covering such unvested Shares in the form of Exhibit B hereto (the “Restricted Stock Agreement”) with the same vesting schedule for such Shares as set forth for such Shares herein. 

2. Adjustment of Exercise Price and Number of Shares. The number and kind of securities purchasable upon the exercise of this Warrant
and the Exercise Price therefor shall be subject to adjustment from time to time upon the occurrence of certain events, as follows: 
 (a)
Adjustments for Subdivisions of Common Stock. If the number of shares of Common Stock outstanding at any time is increased by a stock dividend payable in shares of Common Stock or by a subdivision or split up of stock, then concurrently with
the effectiveness of such dividend, subdivision or split up, (i) the Exercise Price then in effect shall be proportionately decreased and (ii) the number of shares of Common Stock issuable upon exercise of this Warrant shall be increased
in proportion to such increase of outstanding shares of Common Stock. 

  
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 (b) Adjustments for Combinations of Common Stock. If the number of shares of Common
Stock outstanding at any time is decreased by a combination of the outstanding shares of Common Stock, then concurrently with the effectiveness of such combination, (i) the Exercise Price then in effect shall be proportionately increased and
(ii) the number of shares of Common Stock issuable upon exercise of this Warrant shall be decreased in proportion to such decrease in outstanding shares of Common Stock. 

(c) Notification. Upon any increase or decrease in the number of Shares purchasable upon the exercise of this Warrant or the Exercise
Price, the Company shall, within a reasonable period thereafter, deliver written notice thereof to the Holder, which notice shall state the increased or decreased number of Shares purchasable upon the exercise of this Warrant and the adjusted
Exercise Price, setting forth in reasonable detail the method of calculation and the facts upon which such calculations are based. 
 3.
Merger, Consolidation, or Liquidation. If, prior to the exercise in full or expiration of this Warrant, (A) a Change of Control occurs, and (B) in connection therewith, shares of stock, other securities, property, or cash
(collectively, “Acquisition Consideration”) are issuable or deliverable in exchange for the Company’s capital stock, then (C) the Company shall give the Holder at least 10 days prior written notice of the consummation of such
Change of Control and (D) the Holder shall thereafter, at its option, either (i) exercise the Warrant with respect to the Shares that are vested or (ii) acquire in lieu of the shares of Common Stock issuable upon exercise of this
Warrant, upon the consummation of such Change of Control, the Acquisition Consideration which the Holder would have received had the Holder exercised this Warrant with respect to the Shares that are vested immediately prior to such Change of Control
(for clarity, such Acquisition Consideration to be reduced by the aggregate Exercise Price for the then-unexercised portion of the Warrant). For purposes of this Section 3, “Change of Control” shall mean each of (1) the sale or
other disposition of all or substantially all of the assets of the Company, (2) the sale or other disposition of all of the issued and outstanding stock of the Company, (3) the merger or consolidation of the Company with or into another
entity in which all of the issued and outstanding stock of the Company is converted into or exchanged for cash, securities of another entity, or other property, or (4) other reorganization of the Company (or a subsidiary) in which beneficial
ownership (as such term is used in Rule 13d-3 under the Securities Exchange Act of 1934, as amended) of a majority of the outstanding equity of the Company (or a subsidiary) is transferred to a third party;
provided, in each case, that the stockholders of the Company immediately before such transaction do not, immediately thereafter, beneficially own (as such term is used in Rule 13d-3 under the Securities
Exchange Act of 1934, as amended) a majority of the outstanding equity of the entity that acquires the Company’s assets or stock or of the surviving or resulting entity in such a merger or consolidation; provided further that none of the
following shall constitute a Change of Control for purposes of this Warrant: (x) a bona fide capital raise by the Company or (y) a reorganization, spin-out, merger, consolidation or recapitalization
undertaken solely for tax planning purposes not involving a party that is not a stockholder of the Company prior to such corporate action. 

  
 3 

 4. Miscellaneous. 

(a) No Rights of Stockholders. This Warrant does not entitle the Holder to any voting rights as a
stockholder of the Company prior to the exercise of the Warrant. 
 (b) Loss, Theft, Destruction or Mutilation of Warrant. Upon
receipt by the Company of evidence reasonably satisfactory to it of the loss, theft, destruction or mutilation of this Warrant, and in case of loss, theft or destruction, of indemnity or security reasonably satisfactory to it, and upon surrender and
cancellation of this Warrant, if mutilated, the Company will make and deliver a new Warrant of like tenor and dated as of such cancellation, in lieu of this Warrant. 

(c) Expiration of Warrant. Notwithstanding any other provision of this Warrant, this Warrant shall expire and shall no
longer be exercisable upon the sooner of (i) 12:00 a.m., New York time, on the Expiration Date or (ii) a Change of Control. 
 (d)
Governing Law. This Warrant shall be governed by and construed in all respects in accordance with the laws of the State of Delaware without giving effect to the conflicts of laws provisions thereof. 

(e) Entire Agreement; Amendment. This Warrant constitutes the full and entire understanding and agreement between the parties with
regard to the subjects hereof. Neither this Warrant nor any term hereof may be amended, waived, discharged, or terminated other than by a written instrument signed by the party against whom enforcement of any such amendment, waiver, discharge or
termination is sought. 
 (f) Successors and Assigns. The provisions hereof shall inure to the benefit of, and be binding upon, the
successors and assigns, heirs, executors, and administrators of the Company and the Holder. 
 (g) Notices, etc. All notices and other
communications required or permitted hereunder shall be in writing and shall be mailed by registered or certified mail, postage prepaid, by overnight courier, or otherwise delivered by hand or by messenger or sent by facsimile or e-mail and confirmed by mail, addressed (a) if to the Company, at its principal executive office, and (b) if to the Holder, at the address of the Holder set forth on the signature page of this Warrant.
Each such notice or other communication shall for all purposes of this Warrant be treated as effective or having been given when delivered if delivered personally, or, if sent by e-mail, facsimile, mail or by
Federal Express or other reputable overnight carrier, upon receipt. 
 [The remainder of this page has been intentionally left blank.]

  
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 Issued this [    ] day of
[            ], [            ] 
  

			
	TCR2 THERAPEUTICS INC.

 
			
		
	By:	 	  

 
			
	Name:
	Title:
	
	Address:

 WARRANT HOLDER: 

[            ] 
  

			
	By:	 	  

			
	Name:
	Title:
	
	Address:

 [Signature Page to Common Stock Warrant] 

  
 5 

 EXHIBIT A 

NOTICE OF EXERCISE 
  

					
	TO:	 	TCR2 THERAPEUTICS INC.
		 	  

		 	  

		 	Attention:	 	  

 The undersigned hereby elects to purchase
            shares of Common Stock of TCR2 Therapeutics Inc. pursuant to the terms of this Warrant, and tenders herewith payment of the
purchase price of such shares in full as follows: 
 [    ] check in the amount of
$             payable to order of the Company enclosed herewith 

[    ] Wire transfer of immediately available funds to the Company’s account 

[    ] Other [Describe]
                                         
                                    . 

Please issue a certificate or certificates representing said shares of Common Stock in the name of the undersigned or in such other name as is
specified below: 
  

                       
                                      

(Name) 

                       
                                      

 

                       
                                      

(Address) 
 The undersigned hereby
represents and warrants that the aforesaid shares of Common Stock are being acquired for the account of the undersigned for investment and not with a view to, or for resale, in connection with the distribution thereof, and that the undersigned has
no present intention of distributing or reselling such shares. 
  

			
	  

(Signature)

	Title:	 	  

  

	
	  
 (Date)

  
 6 

 EXHIBIT B 

RESTRICTED STOCK AGREEMENT 

For the avoidance of doubt, the Shares (as defined below) are not issued under TCR2
Therapeutics Inc.’s (the “Company”) 2015 Stock Option and Grant Plan, as amended (the “Plan”); however, for the purposes of interpreting the applicable provisions of this Restricted Stock Agreement (the
“RSA”), the terms and conditions of the Plan (other than those applicable to the share reserve) shall govern and apply to this RSA as if the Shares had been issued under the Plan. All capitalized terms used herein and not otherwise
defined shall have the respective meanings set forth in the Warrant or the Plan. 
 1. Purchase and Sale of Shares; Vesting. 

(a) Purchase and Sale. The Company hereby sells to the Holder, and the Holder hereby purchases from the Company, on
                    , 20    ,the number of Shares set forth in the Notice of Exercise
(             Shares) dated                 , pursuant to the Warrant, for the aggregate Exercise Price for
the Shares so purchased. 
 (b) Vesting. The risk of forfeiture shall lapse with respect to the Shares, and such Shares shall become
vested, on the respective dates indicated on the vesting schedule set forth in the Warrant. 
 2. Repurchase Right. Upon a Termination
Event, the Company shall have the right to repurchase Shares of Restricted Stock that are unvested as of the date of such Termination Event as set forth in Section 9(c) of the Plan. 

3. Restrictions on Transfer of Shares. The Shares (whether or not vested) shall be subject to certain transfer restrictions and other
limitations including, without limitation, the provisions contained in Section 9 of the Plan and the Warrant. 
 4. Miscellaneous
Provisions. 
 (a) Record Owner; Dividends. The Holder and any Permitted Transferees, during the duration of this RSA, shall be
considered the record owners of and shall be entitled to vote the Shares if and to the extent the Shares are entitled to voting rights. The Holder and any Permitted Transferees shall be entitled to receive all dividends and any other distributions
declared on the Shares; provided, however, that the Company is under no duty to declare any such dividends or to make any such distribution. 

(b) Section 83(b) Election. The Holder shall consult with the Holder’s tax advisor to determine whether it would
be appropriate for the Holder to make an election under Section 83(b) of the Code with respect to the Shares. Any such election must be filed with the Internal Revenue Service within 30 days of the date of exercise. If the Holder makes an
election under Section 83(b) of the Code, the Holder shall give prompt notice to the Company (and provide a copy of such election to the Company). 

  
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 (c) Equitable Relief. The parties hereto agree and declare that legal remedies may be
inadequate to enforce the provisions of this RSA and that equitable relief, including specific performance and injunctive relief, may be used to enforce the provisions of this RSA. 

(d) Change and Modifications. This RSA may not be orally changed, modified or terminated, nor shall any oral waiver of any of its terms
be effective. This RSA may be changed, modified or terminated only by an agreement in writing signed by the Company and the Holder. 
 (e)
Governing Law. This RSA shall be governed by and construed in accordance with the law of the State of Delaware without giving effect to the conflicts of laws provisions thereof. 

(f) Headings. The headings are intended only for convenience in finding the subject matter and do not constitute part of the text of
this RSA and shall not be considered in the interpretation of this RSA. 
 (g) Saving Clause. If any provision(s) of this RSA shall be
determined to be illegal or unenforceable, such determination shall in no manner affect the legality or enforceability of any other provision hereof. 

(h) Notices. All notices, requests, consents and other communications shall be in writing and be deemed given when delivered personally,
by telex or facsimile transmission or when received if mailed by first class registered or certified mail, postage prepaid. Notices to the Company or the RSA shall be addressed as set forth underneath their signatures below, or to such other address
or addresses as may have been furnished by such party in writing to the other. 
 (i) Benefit and Binding Effect. This RSA shall be
binding upon and shall inure to the benefit of the parties hereto, their respective successors, assigns, and legal representatives. The Company has the right to assign this RSA, and such assignee shall become entitled to all the rights of the
Company hereunder to the extent of such assignment. 
 (j) Counterparts. For the convenience of the parties and to facilitate
execution, this RSA may be executed in two or more counterparts, each of which shall be deemed an original, but all of which shall constitute one and the same document. 

5. Dispute Resolution. 

(a) Except as provided below, any dispute arising out of or relating to the Warrant or the Shares, this RSA, or the breach, termination or
validity of the Shares, the Warrant or this RSA, shall be finally settled by binding arbitration conducted expeditiously in accordance with the J.A.M.S./Endispute Comprehensive Arbitration Rules and Procedures (the “J.A.M.S. Rules”). The
arbitration shall be governed by the United States Arbitration Act, 9 U.S.C. Sections 1—16, and judgment upon the award rendered by the arbitrators may be entered by any court having jurisdiction thereof. The place of arbitration shall be
Boston, Massachusetts. 

  
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 (b) The arbitration shall commence within 60 days of the date on which a written demand for
arbitration is filed by any party hereto. In connection with the arbitration proceeding, the arbitrator shall have the power to order the production of documents by each party and any third-party witnesses. In addition, each party may take up to
three depositions as of right, and the arbitrator may in his or her discretion allow additional depositions upon good cause shown by the moving party. However, the arbitrator shall not have the power to order the answering of interrogatories or the
response to requests for admission. In connection with any arbitration, each party to the arbitration shall provide to the other, no later than seven business days before the date of the arbitration, the identity of all persons that may testify at
the arbitration and a copy of all documents that may be introduced at the arbitration or considered or used by a party’s witness or expert. The arbitrator’s decision and award shall be made and delivered within six months of the selection
of the arbitrator. The arbitrator’s decision shall set forth a reasoned basis for any award of damages or finding of liability. The arbitrator shall not have power to award damages in excess of actual compensatory damages and shall not multiply
actual damages or award punitive damages, and each party hereby irrevocably waives any claim to such damages. 
 (c) The Company, the Holder,
each party to the RSA and any other holder of Shares issued pursuant to this RSA (each, a “Party”) covenants and agrees that such party will participate in the arbitration in good faith. This Section 5
applies equally to requests for temporary, preliminary or permanent injunctive relief, except that in the case of temporary or preliminary injunctive relief any party may proceed in court without prior arbitration for the limited purpose of avoiding
immediate and irreparable harm. 
 (d) Each Party (i) hereby irrevocably submits to the jurisdiction of any United States District Court
of competent jurisdiction for the purpose of enforcing the award or decision in any such proceeding, (ii) hereby waives, and agrees not to assert, by way of motion, as a defense, or otherwise, in any such suit, action or proceeding, any claim
that it is not subject personally to the jurisdiction of the above named courts, that its property is exempt or immune from attachment or execution (except as protected by applicable law), that the suit, action or proceeding is brought in an
inconvenient forum, that the venue of the suit, action or proceeding is improper or that this RSA or the subject matter hereof may not be enforced in or by such court, and (iii) hereby waives and agrees not to seek any review by any court of
any other jurisdiction which may be called upon to grant an enforcement of the judgment of any such court. Each Party hereby consents to service of process by registered mail at the address to which notices are to be given. Each Party agrees that
its, his or her submission to jurisdiction and its, his or her consent to service of process by mail is made for the express benefit of each other Party. Final judgment against any Party in any such action, suit or proceeding may be enforced in
other jurisdictions by suit, action or proceeding on the judgment, or in any other manner provided by or pursuant to the laws of such other jurisdiction. 

  
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 6. Waiver of Statutory Information Rights. The Holder understands and agrees that,
but for the waiver made herein, the Holder would be entitled, upon written demand under oath stating the purpose thereof, to inspect for any proper purpose, and to make copies and extracts from, the Company’s stock ledger, a list of its
stockholders, and its other books and records, and the books and records of subsidiaries of the Company, if any, under the circumstances and in the manner provided in Section 220 of the General Corporation Law of Delaware (any and all such
rights, and any and all such other rights of the Holder as may be provided for in Section 220, the “Inspection Rights”). In light of the foregoing, until the first sale of Stock of the Company to the general public pursuant to
a registration statement filed with and declared effective by the Securities and Exchange Commission under the Securities Act, the Holder hereby unconditionally and irrevocably waives the Inspection Rights, whether such Inspection Rights would be
exercised or pursued directly or indirectly pursuant to Section 220 or otherwise, and covenants and agrees never to directly or indirectly commence, voluntarily aid in any way, prosecute, assign, transfer, or cause to be commenced any claim,
action, cause of action, or other proceeding to pursue or exercise the Inspection Rights. The foregoing waiver shall not affect any rights of a director, in his or her capacity as such, under Section 220. The foregoing waiver shall not apply to
any contractual inspection rights of the Holder under any other written agreement between the Holder and the Company. 
 [SIGNATURE PAGE
FOLLOWS] 

  
 10 

 The foregoing Restricted Stock Agreement is hereby accepted and the terms and conditions
thereof are hereby agreed to by the undersigned as of the date written in Section 1(a) above. 
  

			
	TCR2 THERAPEUTICS INC.
		
	By:	 	  

		 	Name:
		 	Title:
	
	Address:

 The undersigned hereby acknowledges and understands that the Shares purchased hereby are subject to the terms of the
Warrant and this RSA. This RSA is hereby accepted, and the terms and conditions of the Warrant and the RSA, SPECIFICALLY INCLUDING THE ARBITRATION PROVISIONS SET FORTH IN SECTION 5 AND THE WAIVER OF STATUTORY INFORMATION RIGHTS SET FORTH IN SECTION
6 OF THIS RSA, are hereby agreed to, by the undersigned as of the date first above written. 
  

			
	HOLDER:
	
	[            ]
		
	By:	 	
             

 
			
	Name:	 	
	Title:	 	
		
	Address:	 	

  
 11EX-10.1

 Exhibit 10.1 

TCR2, INC. 

2015 STOCK OPTION AND GRANT PLAN 
 SECTION
1. GENERAL PURPOSE OF THE PLAN; DEFINITIONS 
 The name of the plan is the TCR2,
Inc. 2015 Stock Option and Grant Plan (the “Plan”). The purpose of the Plan is to encourage and enable the officers, employees, directors, Consultants and other key persons of
TCR2, Inc., a Delaware corporation (including any successor entity, the “Company”) and its Subsidiaries, upon whose judgment, initiative and efforts the Company largely depends
for the successful conduct of its business, to acquire a proprietary interest in the Company. 
 The following terms shall be defined as set
forth below: 
 “Affiliate” of any Person means a Person that directly or indirectly, through one or more intermediaries,
controls, is controlled by or is under common control with the first mentioned Person. A Person shall be deemed to control another Person if such first Person possesses directly or indirectly the power to direct, or cause the direction of, the
management and policies of the second Person, whether through the ownership of voting securities, by contract or otherwise. 

“Award” or “Awards,” except where referring to a particular category of grant under the Plan, shall include
Incentive Stock Options, Non-Qualified Stock Options, Restricted Stock Awards, Unrestricted Stock Awards, Restricted Stock Units or any combination of the foregoing. 

“Award Agreement” means a written or electronic agreement setting forth the terms and provisions applicable to
an Award granted under the Plan. Each Award Agreement may contain terms and conditions in addition to those set forth in the Plan; provided, however, in the event of any conflict in the terms of the Plan and the Award Agreement, the
terms of the Plan shall govern. 
 “Board” means the Board of Directors of the Company. 

“Cause” shall have the meaning as set forth in the Award Agreement(s). In the case that any Award Agreement does not contain
a definition of “Cause,” it shall mean (i) the grantee’s dishonest statements or acts with respect to the Company or any Affiliate of the Company, or any current or prospective customers, suppliers vendors or other third parties
with which such entity does business; (ii) the grantee’s commission of (A) a felony or (B) any misdemeanor involving moral turpitude, deceit, dishonesty or fraud; (iii) the grantee’s failure to perform his assigned
duties and responsibilities to the reasonable satisfaction of the Company which failure continues, in the reasonable judgment of the Company, after written notice given to the grantee by the Company; (iv) the grantee’s gross negligence,
willful misconduct or insubordination with respect to the Company or any Affiliate of the Company; or (v) the grantee’s material violation of any provision of any agreement(s) between the grantee and the Company relating to noncompetition,
nonsolicitation, nondisclosure and/or assignment of inventions. 

 “Chief Executive Officer” means the Chief Executive Officer of the Company
or, if there is no Chief Executive Officer, then the President of the Company. 
 “Code” means the Internal Revenue Code of
1986, as amended, and any successor Code, and related rules, regulations and interpretations. 
 “Committee” means the
Committee of the Board referred to in Section 2. 
 “Consultant” means any natural person that provides bona fide
services to the Company (including a Subsidiary), and such services are not in connection with the offer or sale of securities in a capital-raising transaction and do not directly or indirectly promote or maintain a market for the Company’s
securities. 
 “Disability” means “disability” as defined in Section 422(c) of the Code. 

“Effective Date” means the date on which the Plan is adopted as set forth on the final page of the Plan. 

“Exchange Act” means the Securities Exchange Act of 1934, as amended, and the rules and regulations thereunder. 

“Fair Market Value” of the Stock on any given date means the fair market value of the Stock determined in good faith by the
Committee based on the reasonable application of a reasonable valuation method not inconsistent with Section 409A of the Code. If the Stock is admitted to trade on a national securities exchange, the determination shall be made by reference to
the closing price reported on such exchange. If there is no closing price for such date, the determination shall be made by reference to the last date preceding such date for which there is a closing price. If the date for which Fair Market Value is
determined is the first day when trading prices for the Stock are reported on a national securities exchange, the Fair Market Value shall be the “Price to the Public” (or equivalent) set forth on the cover page for the final prospectus
relating to the Company’s Initial Public Offering. 
 “Good Reason” shall have the meaning as set forth in the Award
Agreement(s). In the case that any Award Agreement does not contain a definition of “Good Reason,” it shall mean (i) a material diminution in the grantee’s base salary except for across-the-board salary reductions similarly affecting all or substantially all similarly situated employees of the Company or (ii) a change of more than 50 miles in the geographic location at which the
grantee provides services to the Company, so long as the grantee provides at least 90 days notice to the Company following the initial occurrence of any such event and the Company fails to cure such event within 30 days thereafter. 

“Grant Date” means the date that the Committee designates in its approval of an Award in accordance with applicable law as
the date on which the Award is granted, which date may not precede the date of such Committee approval. 
 “Holder” means,
with respect to an Award or any Shares, the Person holding such Award or Shares, including the initial recipient of the Award or any Permitted Transferee. 

  
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 “Incentive Stock Option” means any Stock Option designated and qualified as
an “incentive stock option” as defined in Section 422 of the Code. 
 “Initial Public Offering” means the
consummation of the first firm commitment underwritten public offering pursuant to an effective registration statement under the Securities Act covering the offer and sale by the Company of its equity securities, as a result of or following which
the Stock shall be publicly held. 
 “Non-Qualified Stock Option” means any Stock
Option that is not an Incentive Stock Option. 
 “Option” or “Stock Option” means any option to purchase
shares of Stock granted pursuant to Section 5. 
 “Permitted Transferees” shall mean any of the following to whom a
Holder may transfer Shares hereunder (as set forth in Section 9(a)(ii)(A)): the Holder’s child, stepchild, grandchild, parent, stepparent, grandparent, spouse, former spouse, sibling, niece, nephew, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law, or sister-in-law, including adoptive relationships, any person sharing the Holder’s household (other than a tenant or employee), a trust in which these persons have more than fifty percent of the beneficial
interest, a foundation in which these persons control the management of assets, and any other entity in which these persons own more than fifty percent of the voting interests; provided, however, that any such trust does not require or permit
distribution of any Shares during the term of the Award Agreement unless subject to its terms. Upon the death of the Holder, the term Permitted Transferees shall also include such deceased Holder’s estate, executors, administrators, personal
representatives, heirs, legatees and distributees, as the case may be. 
 “Person” shall mean any individual, corporation,
partnership (limited or general), limited liability company, limited liability partnership, association, trust, joint venture, unincorporated organization or any similar entity. 

“Restricted Stock Award” means Awards granted pursuant to Section 6 and “Restricted Stock” means Shares
issued pursuant to such Awards. 
 “Restricted Stock Unit” means an Award of phantom stock units to a grantee, which may be
settled in cash or Shares as determined by the Committee, pursuant to Section 8. 
 “Sale Event” means the
consummation of (i) the dissolution or liquidation of the Company, (ii) the sale of all or substantially all of the assets of the Company on a consolidated basis to an unrelated person or entity, (iii) a merger, reorganization or
consolidation pursuant to which the holders of the Company’s outstanding voting power immediately prior to such transaction do not own a majority of the outstanding voting power of the surviving or resulting entity (or its ultimate parent, if
applicable), (iv) the acquisition of all or a majority of the outstanding voting stock of the Company in a single transaction or a series of related transactions by a Person or group of Persons, or (v) any other acquisition of the business of
the Company, as determined by the Board; provided, however, that the Company’s Initial Public Offering, any subsequent public offering or another capital raising event, or a merger effected solely to change the Company’s domicile
shall not constitute a “Sale Event.” 

  
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 “Section 409A” means Section 409A of the Code and
the regulations and other guidance promulgated thereunder. 
 “Securities Act” means the Securities Act of 1933, as
amended, and the rules and regulations thereunder. 
 “Service Relationship” means any relationship as a full-time
employee, part-time employee, director or other key person (including Consultants) of the Company or any Subsidiary or any successor entity (e.g., a Service Relationship shall be deemed to continue without interruption in the event an
individual’s status changes from full-time employee to part-time employee or Consultant). 
 “Shares” means shares of
Stock. 
 “Stock” means the Common Stock, par value $0.0001 per share, of the Company. 

“Subsidiary” means any corporation or other entity (other than the Company) in which the Company has more than a
50 percent interest, either directly or indirectly. 
 “Ten Percent Owner” means an employee who owns or is deemed to
own (by reason of the attribution rules of Section 424(d) of the Code) more than 10 percent of the combined voting power of all classes of stock of the Company or any parent of the Company or any Subsidiary. 

“Termination Event” means the termination of the Award recipient’s Service Relationship with the Company and its
Subsidiaries for any reason whatsoever, regardless of the circumstances thereof, and including, without limitation, upon death, disability, retirement, discharge or resignation for any reason, whether voluntarily or involuntarily. The following
shall not constitute a Termination Event: (i) a transfer to the service of the Company from a Subsidiary or from the Company to a Subsidiary, or from one Subsidiary to another Subsidiary or (ii) an approved leave of absence for military
service or sickness, or for any other purpose approved by the Committee, if the individual’s right to re-employment is guaranteed either by a statute or by contract or under the policy pursuant to which
the leave of absence was granted or if the Committee otherwise so provides in writing. 
 “Unrestricted Stock Award” means
any Award granted pursuant to Section 7 and “Unrestricted Stock” means Shares issued pursuant to such Awards. 
  

	SECTION 2.	 ADMINISTRATION OF PLAN; COMMITTEE AUTHORITY TO SELECT GRANTEES AND DETERMINE AWARDS

 (a) Administration of Plan. The Plan shall be administered by the Board, or at the discretion of the Board, by a
committee of the Board, comprised of not less than two directors. All references herein to the “Committee” shall be deemed to refer to the group then responsible for administration of the Plan at the relevant time (i.e., either the Board
of Directors or a committee or committees of the Board, as applicable). 

  
 4 

 (b) Powers of Committee. The Committee shall have the power and authority to grant
Awards consistent with the terms of the Plan, including the power and authority: 
 (i) to select the individuals to whom Awards may from
time to time be granted; 
 (ii) to determine the time or times of grant, and the amount, if any, of Incentive Stock Options, Non-Qualified Stock Options, Restricted Stock Awards, Unrestricted Stock Awards, Restricted Stock Units, or any combination of the foregoing, granted to any one or more grantees; 

(iii) to determine the number of Shares to be covered by any Award and, subject to the provisions of the Plan, the price, exercise price,
conversion ratio or other price relating thereto; 
 (iv) to determine and, subject to Section 12, to modify from time to time the terms
and conditions, including restrictions, not inconsistent with the terms of the Plan, of any Award, which terms and conditions may differ among individual Awards and grantees, and to approve the form of Award Agreements; 

(v) to accelerate at any time the exercisability or vesting of all or any portion of any Award; 

(vi) to impose any limitations on Awards, including limitations on transfers, repurchase provisions and the like, and to exercise repurchase
rights or obligations; 
 (vii) subject to Section 5(a)(ii) and any restrictions imposed by Section 409A, to extend at any time the
period in which Stock Options may be exercised; and 
 (viii) at any time to adopt, alter and repeal such rules, guidelines and practices for
administration of the Plan and for its own acts and proceedings as it shall deem advisable; to interpret the terms and provisions of the Plan and any Award (including Award Agreements); to make all determinations it deems advisable for the
administration of the Plan; to decide all disputes arising in connection with the Plan; and to otherwise supervise the administration of the Plan. 
 All
decisions and interpretations of the Committee shall be binding on all persons, including the Company and all Holders. 
 (c) Award
Agreement. Awards under the Plan shall be evidenced by Award Agreements that set forth the terms, conditions and limitations for each Award. 

(d) Indemnification. Neither the Board nor the Committee, nor any member of either or any delegate thereof, shall be liable for any act,
omission, interpretation, construction or determination made in good faith in connection with the Plan, and the members of the Board and the Committee (and any delegate thereof) shall be entitled in all cases to indemnification and reimbursement by
the Company in respect of any claim, loss, damage or expense (including, without limitation, reasonable attorneys’ fees) arising or resulting therefrom to the fullest extent permitted by law and/or under the Company’s governing documents,
including its certificate of incorporation or Bylaws, or any directors’ and officers’ liability insurance coverage which may be in effect from time to time and/or any indemnification agreement between such individual and the Company. 

  
 5 

 (e) Foreign Award Recipients. Notwithstanding any provision of the Plan to the
contrary, in order to comply with the laws in other countries in which the Company and any Subsidiary operate or have employees or other individuals eligible for Awards, the Committee, in its sole discretion, shall have the power and authority to:
(i) determine which Subsidiaries, if any, shall be covered by the Plan; (ii) determine which individuals, if any, outside the United States are eligible to participate in the Plan; (iii) modify the terms and conditions of any Award
granted to individuals outside the United States to comply with applicable foreign laws; (iv) establish subplans and modify exercise procedures and other terms and procedures, to the extent the Committee determines such actions to be necessary
or advisable (and such subplans and/or modifications shall be attached to the Plan as appendices); provided, however, that no such subplans and/or modifications shall increase the share limitation contained in Section 3(a) hereof;
and (v) take any action, before or after an Award is made, that the Committee determines to be necessary or advisable to obtain approval or comply with any local governmental regulatory exemptions or approvals. 

 

	SECTION 3.	 STOCK ISSUABLE UNDER THE PLAN; MERGERS AND OTHER TRANSACTIONS; SUBSTITUTION 

(a) Stock Issuable. The maximum number of Shares reserved and available for issuance under the Plan shall be 7,088,040 Shares, subject
to adjustment as provided in Section 3(b). For purposes of this limitation, the Shares underlying any Awards that are forfeited, canceled, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or otherwise
terminated (other than by exercise) and Shares that are withheld upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding shall be added back to the Shares available for issuance under the Plan. Subject to
such overall limitations, Shares may be issued up to such maximum number pursuant to any type or types of Award, and no more than 30,000,000 Shares may be issued pursuant to Incentive Stock Options. The Shares available for issuance under the Plan
may be authorized but unissued Shares or Shares reacquired by the Company. Beginning on the date that the Company becomes subject to Section 162(m) of the Code, Options with respect to no more than 7,088,040 Shares shall be granted to any one
individual in any calendar year period. 
 (b) Changes in Stock. Subject to Section 3(c) hereof, if, as a result of any
reorganization, recapitalization, reclassification, stock dividend, stock split, reverse stock split or other similar change in the Company’s capital stock, the outstanding Shares are increased or decreased or are exchanged for a different
number or kind of shares or other securities of the Company, or additional Shares or new or different shares or other securities of the Company or other non-cash assets are distributed with respect to such
Shares or other securities, in each case, without the receipt of consideration by the Company, or, if, as a result of any merger or consolidation, or sale of all or substantially all of the assets of the Company, the outstanding Shares are converted
into or exchanged for other securities of the Company or any successor entity (or a parent or subsidiary thereof), the Committee shall make an appropriate and proportionate adjustment in (i) the maximum number of Shares reserved for issuance
under the Plan, (ii) the number and kind of Shares or other securities subject to any then outstanding 

  
 6 

 
Awards under the Plan, (iii) the repurchase price, if any, per Share subject to each outstanding Award, and (iv) the exercise price for each Share subject to any then outstanding Stock
Options under the Plan, without changing the aggregate exercise price (i.e., the exercise price multiplied by the number of Stock Options) as to which such Stock Options remain exercisable. The adjustment by the Committee shall be final, binding and
conclusive. No fractional Shares shall be issued under the Plan resulting from any such adjustment, but the Committee in its discretion may make a cash payment in lieu of fractional shares. 

(c) Sale Events. 
 (i)
Options. 
 (A) In the case of and subject to the consummation of a Sale Event, the Plan and all outstanding Options issued hereunder
shall terminate upon the effective time of any such Sale Event unless assumed or continued by the successor entity, or new stock options or other awards of the successor entity or parent thereof are substituted therefor, with an equitable or proportionate adjustment as to the number and kind of shares and, if appropriate, the per share exercise prices, as such parties shall agree (after taking into account any
acceleration hereunder and/or pursuant to the terms of any Award Agreement). 
 (B) In the event of the termination of the Plan and all
outstanding Options issued hereunder pursuant to Section 3(c), each Holder of Options shall be permitted, within a period of time prior to the consummation of the Sale Event as specified by the Committee, to exercise all such Options which are
then exercisable or will become exercisable as of the effective time of the Sale Event; provided, however, that the exercise of Options not exercisable prior to the Sale Event shall be subject to the consummation of the Sale Event. 

(C) Notwithstanding anything to the contrary in Section 3(c)(i)(A), in the event of a Sale Event, the Company shall have the right, but
not the obligation, to make or provide for a cash payment to the Holders of Options, without any consent of the Holders, in exchange for the cancellation thereof, in an amount equal to the difference between (A) the value as determined by the
Committee of the consideration payable per share of Stock pursuant to the Sale Event (the “Sale Price”) times the number of Shares subject to outstanding Options being cancelled (to the extent then vested and exercisable, including
by reason of acceleration in connection with such Sale Event, at prices not in excess of the Sale Price) and (B) the aggregate exercise price of all such outstanding vested and exercisable Options. 

(ii) Restricted Stock and Restricted Stock Unit Awards. 

(A) In the case of and subject to the consummation of a Sale Event, all unvested Restricted Stock and unvested Restricted Stock Unit Awards
(other than those becoming vested as a result of the Sale Event) issued hereunder shall be forfeited immediately prior to the effective time of any such Sale Event unless assumed or continued by the successor entity, or awards of the successor
entity or parent thereof are substituted therefor, with an equitable or proportionate adjustment as to the number and kind of shares subject to such awards as such parties shall agree (after taking into account any acceleration hereunder and/or
pursuant to the terms of any Award Agreement). 

  
 7 

 (B) In the event of the forfeiture of Restricted Stock pursuant to
Section 3(c)(ii)(A), such Restricted Stock shall be repurchased from the Holder thereof at a price per share equal to the original per share purchase price paid by the Holder (subject to adjustment as provided in Section 3(b)) for such
Shares. 
 (C) Notwithstanding anything to the contrary in Section 3(c)(ii)(A), in the event of a Sale Event, the Company shall have
the right, but not the obligation, to make or provide for a cash payment to the Holders of Restricted Stock or Restricted Stock Unit Awards, without consent of the Holders, in exchange for the cancellation thereof, in an amount equal to the Sale
Price times the number of Shares subject to such Awards, to be paid at the time of such Sale Event or upon the later vesting of such Awards. 
  

	SECTION 4.	 ELIGIBILITY 

Grantees under the Plan will be such full or part-time officers and other employees, directors, Consultants and key persons of the Company and
any Subsidiary who are selected from time to time by the Committee in its sole discretion; provided, however, that Awards shall be granted only to those individuals described in Rule 701(c) of the Securities Act. 

 

	SECTION 5.	 STOCK OPTIONS 

Upon the grant of a Stock Option, the Company and the grantee shall enter into an Award Agreement. The terms and conditions of each such Award
Agreement shall be determined by the Committee, and such terms and conditions may differ among individual Awards and grantees. 
 Stock
Options granted under the Plan may be either Incentive Stock Options or Non-Qualified Stock Options. Incentive Stock Options may be granted only to employees of the Company or any Subsidiary that is a
“subsidiary corporation” within the meaning of Section 424(f) of the Code. To the extent that any Option does not qualify as an Incentive Stock Option, it shall be deemed a Non-Qualified Stock
Option. 
 (a) Terms of Stock Options. The Committee in its discretion may grant Stock Options to those individuals who meet the
eligibility requirements of Section 4. Stock Options shall be subject to the following terms and conditions and shall contain such additional terms and conditions, not inconsistent with the terms of the Plan, as the Committee shall deem
desirable. 
 (i) Exercise Price. The exercise price per share for the Shares covered by a Stock Option shall be determined by the
Committee at the time of grant but shall not be less than 100 percent of the Fair Market Value on the Grant Date. In the case of an Incentive Stock Option that is granted to a Ten Percent Owner, the exercise price per share for the Shares
covered by such Incentive Stock Option shall not be less than 110 percent of the Fair Market Value on the Grant Date. 

  
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 (ii) Option Term. The term of each Stock Option shall be fixed by the Committee, but
no Stock Option shall be exercisable more than ten years from the Grant Date. In the case of an Incentive Stock Option that is granted to a Ten Percent Owner, the term of such Stock Option shall be no more than five years from the Grant Date. 

(iii) Exercisability; Rights of a Stockholder. Stock Options shall become exercisable and/or vested at such time or times, whether or
not in installments, as shall be determined by the Committee at or after the Grant Date. The Award Agreement may permit a grantee to exercise all or a portion of a Stock Option immediately at grant; provided that the Shares issued upon such exercise
shall be subject to restrictions and a vesting schedule identical to the vesting schedule of the related Stock Option, such Shares shall be deemed to be Restricted Stock for purposes of the Plan, and the optionee may be required to enter into an
additional or new Award Agreement as a condition to exercise of such Stock Option. An optionee shall have the rights of a stockholder only as to Shares acquired upon the exercise of a Stock Option and not as to unexercised Stock Options. An optionee
shall not be deemed to have acquired any Shares unless and until a Stock Option shall have been exercised pursuant to the terms of the Award Agreement and this Plan and the optionee’s name has been entered on the books of the Company as a
stockholder. 
 (iv) Method of Exercise. Stock Options may be exercised by an optionee in whole or in part, by the optionee giving
written or electronic notice of exercise to the Company, specifying the number of Shares to be purchased. Payment of the purchase price may be made by one or more of the following methods (or any combination thereof) to the extent provided in the
Award Agreement: 
 (A) In cash, by certified or bank check, by wire transfer of immediately available funds, or other
instrument acceptable to the Committee; 
 (B) If permitted by the Committee, by the optionee delivering to the Company a
promissory note, if the Board has expressly authorized the loan of funds to the optionee for the purpose of enabling or assisting the optionee to effect the exercise of his or her Stock Option; provided, that at least so much of the exercise
price as represents the par value of the Stock shall be paid in cash if required by state law; 
 (C) If permitted by the
Committee and the Initial Public Offering has occurred (or the Stock otherwise becomes publicly-traded), through the delivery (or attestation to the ownership) of Shares that have been purchased by the optionee on the open market or that are
beneficially owned by the optionee and are not then subject to restrictions under any Company plan. To the extent required to avoid variable accounting treatment under ASC 718 or other applicable accounting rules, such surrendered Shares if
originally purchased from the Company shall have been owned by the optionee for at least six months. Such surrendered Shares shall be valued at Fair Market Value on the exercise date; 

  
 9 

 (D) If permitted by the Committee and the Initial Public Offering has
occurred (or the Stock otherwise becomes publicly-traded), by the optionee delivering to the Company a properly executed exercise notice together with irrevocable instructions to a broker to promptly deliver to the Company cash or a check payable
and acceptable to the Company for the purchase price; provided that in the event the optionee chooses to pay the purchase price as so provided, the optionee and the broker shall comply with such procedures and enter into such agreements of
indemnity and other agreements as the Committee shall prescribe as a condition of such payment procedure; or 
 (E) If
permitted by the Committee, and only with respect to Stock Options that are not Incentive Stock Options, by a “net exercise” arrangement pursuant to which the Company will reduce the number of Shares issuable upon exercise by the largest
whole number of Shares with a Fair Market Value that does not exceed the aggregate exercise price. 
 Payment instruments will be received
subject to collection. No certificates for Shares so purchased will be issued to the optionee or, with respect to uncertificated Stock, no transfer to the optionee on the records of the Company will take place, until the Company has completed all
steps it has deemed necessary to satisfy legal requirements relating to the issuance and sale of the Shares, which steps may include, without limitation, (i) receipt of a representation from the optionee at the time of exercise of the Option
that the optionee is purchasing the Shares for the optionee’s own account and not with a view to any sale or distribution of the Shares or other representations relating to compliance with applicable law governing the issuance of securities,
(ii) the legending of the certificate (or notation on any book entry) representing the Shares to evidence the foregoing restrictions, and (iii) obtaining from optionee payment or provision for all withholding taxes due as a result of the
exercise of the Option. The delivery of certificates representing the shares of Stock (or the transfer to the optionee on the records of the Company with respect to uncertificated Stock) to be purchased pursuant to the exercise of a Stock Option
will be contingent upon (A) receipt from the optionee (or a purchaser acting in his or her stead in accordance with the provisions of the Stock Option) by the Company of the full purchase price for such Shares and the fulfillment of any other
requirements contained in the Award Agreement or applicable provisions of laws and (B) if required by the Company, the optionee shall have entered into any stockholders agreements or other agreements with the Company and/or certain other of the
Company’s stockholders relating to the Stock. In the event an optionee chooses to pay the purchase price by previously-owned Shares through the attestation method, the number of Shares transferred to the optionee upon the exercise of the Stock
Option shall be net of the number of Shares attested to. 
 (b) Annual Limit on Incentive Stock Options. To the extent required for
“incentive stock option” treatment under Section 422 of the Code, the aggregate Fair Market Value (determined as of the Grant Date) of the Shares with respect to which Incentive Stock Options granted under the Plan and any other plan
of the Company or its parent and any Subsidiary that become exercisable for the first time by an optionee during any calendar year shall not exceed $100,000 or such other limit as may be in effect from time to time under Section 422 of the
Code. To the extent that any Stock Option exceeds this limit, it shall constitute a Non-Qualified Stock Option. 

  
 10 

 (c) Termination. Any portion of a Stock Option that is not vested and exercisable on
the date of termination of an optionee’s Service Relationship shall immediately expire and be null and void. Once any portion of the Stock Option becomes vested and exercisable, the optionee’s right to exercise such portion of the Stock
Option (or the optionee’s representatives and legatees as applicable) in the event of a termination of the optionee’s Service Relationship shall continue until the earliest of: (i) the date which is: (A) 12 months following the date
on which the optionee’s Service Relationship terminates due to death or Disability (or such longer period of time as determined by the Committee and set forth in the applicable Award Agreement), or (B) three months following the date on
which the optionee’s Service Relationship terminates if the termination is due to any reason other than death or Disability (or such longer period of time as determined by the Committee and set forth in the applicable Award Agreement), or
(ii) the Expiration Date set forth in the Award Agreement; provided that notwithstanding the foregoing, an Award Agreement may provide that if the optionee’s Service Relationship is terminated for Cause, the Stock Option shall
terminate immediately and be null and void upon the date of the optionee’s termination and shall not thereafter be exercisable. 
 SECTION 6.
RESTRICTED STOCK AWARDS 
 (a) Nature of Restricted Stock Awards. The Committee may, in its sole discretion, grant (or sell at
par value or such other purchase price determined by the Committee) to an eligible individual under Section 4 hereof a Restricted Stock Award under the Plan. The Committee shall determine the restrictions and conditions applicable to each
Restricted Stock Award at the time of grant. Conditions may be based on continuing employment (or other Service Relationship), achievement of pre-established performance goals and objectives and/or such other
criteria as the Committee may determine. Upon the grant of a Restricted Stock Award, the Company and the grantee shall enter into an Award Agreement. The terms and conditions of each such Award Agreement shall be determined by the Committee, and
such terms and conditions may differ among individual Awards and grantees. 
 (b) Rights as a Stockholder. Upon the grant of the
Restricted Stock Award and payment of any applicable purchase price, a grantee of Restricted Stock shall be considered the record owner of and shall be entitled to vote the Restricted Stock if, and to the extent, such Shares are entitled to voting
rights, subject to such conditions contained in the Award Agreement. The grantee shall be entitled to receive all dividends and any other distributions declared on the Shares; provided, however, that the Company is under no duty to
declare any such dividends or to make any such distribution. Unless the Committee shall otherwise determine, certificates evidencing the Restricted Stock shall remain in the possession of the Company until such Restricted Stock is vested as provided
in subsection (d) below of this Section, and the grantee shall be required, as a condition of the grant, to deliver to the Company a stock power endorsed in blank and such other instruments of transfer as the Committee may prescribe. 

(c) Restrictions. Restricted Stock may not be sold, assigned, transferred, pledged or otherwise encumbered or disposed of except as
specifically provided herein or in the Award Agreement. Except as may otherwise be provided by the Committee either in the Award Agreement or, subject to Section 12 below, in writing after the Award Agreement is issued, if a grantee’s
Service Relationship with the Company and any Subsidiary terminates, the Company or its assigns shall have the right, as may be specified in the relevant instrument, to repurchase some or all of the Shares subject to the Award at such purchase price
as is set forth in the Award Agreement. 

  
 11 

 (d) Vesting of Restricted Stock. The Committee at the time of grant shall specify in
the Award Agreement the date or dates and/or the attainment of pre-established performance goals, objectives and other conditions on which the substantial risk of forfeiture imposed shall lapse and the
Restricted Stock shall become vested, subject to such further rights of the Company or its assigns as may be specified in the Award Agreement. 
 SECTION 7.
UNRESTRICTED STOCK AWARDS 
 The Committee may, in its sole discretion, grant (or sell at par value or such other purchase price
determined by the Committee) to an eligible person under Section 4 hereof an Unrestricted Stock Award under the Plan. Unrestricted Stock Awards may be granted in respect of past services or other valid consideration, or in lieu of cash
compensation due to such grantee. 
 SECTION 8. RESTRICTED STOCK UNITS 

(a) Nature of Restricted Stock Units. The Committee may, in its sole discretion, grant to an eligible person under Section 4 hereof
Restricted Stock Units under the Plan. The Committee shall determine the restrictions and conditions applicable to each Restricted Stock Unit at the time of grant. Vesting conditions may be based on continuing employment (or other Service
Relationship), achievement of pre-established performance goals and objectives and/or other such criteria as the Committee may determine. Upon the grant of Restricted Stock Units, the grantee and the Company
shall enter into an Award Agreement. The terms and conditions of each such Award Agreement shall be determined by the Committee and may differ among individual Awards and grantees. On or promptly following the vesting date or dates applicable to any
Restricted Stock Unit, but in no event later than March 15 of the year following the year in which such vesting occurs, such Restricted Stock Unit(s) shall be settled in the form of cash or shares of Stock, as specified in the Award Agreement.
Restricted Stock Units may not be sold, assigned, transferred, pledged, or otherwise encumbered or disposed of. 
 (b) Rights as a
Stockholder. A grantee shall have the rights of a stockholder only as to Shares, if any, acquired upon settlement of Restricted Stock Units. A grantee shall not be deemed to have acquired any such Shares unless and until the Restricted Stock
Units shall have been settled in Shares pursuant to the terms of the Plan and the Award Agreement, the Company shall have issued and delivered a certificate representing the Shares to the grantee (or transferred on the records of the Company with
respect to uncertificated stock), and the grantee’s name has been entered in the books of the Company as a stockholder. 
 (c)
Termination. Except as may otherwise be provided by the Committee either in the Award Agreement or in writing after the Award Agreement is issued, a grantee’s right in all Restricted Stock Units that have not vested shall automatically
terminate upon the grantee’s cessation of Service Relationship with the Company and any Subsidiary for any reason. 

  
 12 

	SECTION	 9. TRANSFER RESTRICTIONS; COMPANY RIGHT OF FIRST REFUSAL; COMPANY REPURCHASE RIGHTS

 (a) Restrictions on Transfer. 

(i) Non-Transferability of Stock Options. Stock Options and, prior to exercise, the Shares
issuable upon exercise of such Stock Option, shall not be transferable by the optionee otherwise than by will, or by the laws of descent and distribution, and all Stock Options shall be exercisable, during the optionee’s lifetime, only by the
optionee, or by the optionee’s legal representative or guardian in the event of the optionee’s incapacity. Notwithstanding the foregoing, the Committee, in its sole discretion, may provide in the Award Agreement regarding a given Stock
Option that the optionee may transfer by gift, without consideration for the transfer, his or her Non-Qualified Stock Options to his or her family members (as defined in Rule 701 of the Securities Act), to
trusts for the benefit of such family members, or to partnerships in which such family members are the only partners (to the extent such trusts or partnerships are considered “family members” for purposes of Rule 701 of the Securities
Act), provided that the transferee agrees in writing with the Company to be bound by all of the terms and conditions of this Plan and the applicable Award Agreement, including the execution of a stock power upon the issuance of Shares. Stock
Options, and the Shares issuable upon exercise of such Stock Options, shall be restricted as to any pledge, hypothecation, or other transfer, including any short position, any “put equivalent position” (as defined in the Exchange Act) or
any “call equivalent position” (as defined in the Exchange Act) prior to exercise. 
 (ii) Shares. No Shares shall be sold,
assigned, transferred, pledged, hypothecated, given away or in any other manner disposed of or encumbered, whether voluntarily or by operation of law, unless (i) the transfer is in compliance with the terms of the applicable Award Agreement,
all applicable securities laws (including, without limitation, the Securities Act), and with the terms and conditions of this Section 9, (ii) the transfer does not cause the Company to become subject to the reporting requirements of the
Exchange Act, and (iii) the transferee consents in writing to be bound by the provisions of the Plan and the Award Agreement, including this Section 9. In connection with any proposed transfer, the Committee may require the transferor to
provide at the transferor’s own expense an opinion of counsel to the transferor, satisfactory to the Committee, that such transfer is in compliance with all foreign, federal and state securities laws (including, without limitation, the
Securities Act). Any attempted transfer of Shares not in accordance with the terms and conditions of this Section 9 shall be null and void, and the Company shall not reflect on its records any change in record ownership of any Shares as a
result of any such transfer, shall otherwise refuse to recognize any such transfer and shall not in any way give effect to any such transfer of Shares. The Company shall be entitled to seek protective orders, injunctive relief and other remedies
available at law or in equity including, without limitation, seeking specific performance or the rescission of any transfer not made in strict compliance with the provisions of this Section 9. Subject to the foregoing general provisions, and
unless otherwise provided in the applicable Award Agreement, Shares may be transferred pursuant to the following specific terms and conditions (provided that with respect to any transfer of Restricted Stock, all vesting and forfeiture provisions
shall continue to apply with respect to the original recipient): 

  
 13 

 (A) Transfers to Permitted Transferees. The Holder may transfer any
or all of the Shares to one or more Permitted Transferees; provided, however, that following such transfer, such Shares shall continue to be subject to the terms of this Plan (including this Section 9) and such Permitted Transferee(s)
shall, as a condition to any such transfer, deliver a written acknowledgment to that effect to the Company and shall deliver a stock power to the Company with respect to the Shares. Notwithstanding the foregoing, the Holder may not transfer any of
the Shares to a Person whom the Company reasonably determines is a direct competitor or a potential competitor of the Company or any of its Subsidiaries. 

(B) Transfers Upon Death. Upon the death of the Holder, any Shares then held by the Holder at the time of such death and
any Shares acquired after the Holder’s death by the Holder’s legal representative shall be subject to the provisions of this Plan, and the Holder’s estate, executors, administrators, personal representatives, heirs, legatees and
distributees shall be obligated to convey such Shares to the Company or its assigns under the terms contemplated by the Plan and the Award Agreement. 

(b) Right of First Refusal. In the event that a Holder desires at any time to sell or otherwise transfer all or any part of his or her
Shares (other than shares of Restricted Stock which by their terms are not transferrable), the Holder first shall give written notice to the Company of the Holder’s intention to make such transfer. Such notice shall state the number of Shares
that the Holder proposes to sell (the “Offered Shares”), the price and the terms at which the proposed sale is to be made and the name and address of the proposed transferee. At any time within 30 days after the receipt of such
notice by the Company, the Company or its assigns may elect to purchase all or any portion of the Offered Shares at the price and on the terms offered by the proposed transferee and specified in the notice. The Company or its assigns shall exercise
this right by mailing or delivering written notice to the Holder within the foregoing 30-day period. If the Company or its assigns elect to exercise its purchase rights under this Section 9(b), the
closing for such purchase shall, in any event, take place within 45 days after the receipt by the Company of the initial notice from the Holder. In the event that the Company or its assigns do not elect to exercise such purchase right, or in the
event that the Company or its assigns do not pay the full purchase price within such 45-day period, the Holder shall be required to pay a transaction processing fee of $10,000 to the Company (unless waived by
the Committee) and then may, within 60 days thereafter, sell the Offered Shares to the proposed transferee and at the same price and on the same terms as specified in the Holder’s notice. Any Shares not sold to the proposed transferee shall
remain subject to the Plan. If the Holder is a party to any stockholders agreements or other agreements with the Company and/or certain other of the Company’s stockholders relating to the Shares, (i) the transferring Holder shall comply
with the requirements of such stockholders agreements or other agreements relating to any proposed transfer of the Offered Shares, and (ii) any proposed transferee that purchases Offered Shares shall enter into such stockholders agreements or
other agreements with the Company and/or certain of the Company’s stockholders relating to the Offered Shares on the same terms and in the same capacity as the transferring Holder. 

  
 14 

 (c) Company’s Right of Repurchase. 

(i) Right of Repurchase for Unvested Shares Issued Upon the Exercise of an Option. Upon a Termination Event, the Company or its assigns
shall have the right and option to repurchase from a Holder of Shares acquired upon exercise of a Stock Option which are still subject to a risk of forfeiture as of the Termination Event. Such repurchase rights may be exercised by the Company within
the later of (A) six months following the date of such Termination Event or (B) seven months after the acquisition of Shares upon exercise of a Stock Option. The repurchase price shall be equal to the lower of the original per share price
paid by the Holder, subject to adjustment as provided in Section 3(b) of the Plan, or the current Fair Market Value of such Shares as of the date the Company elects to exercise its repurchase rights. 

(ii) Right of Repurchase With Respect to Restricted Stock. Upon a Termination Event, the Company or its assigns shall have the right and
option to repurchase from a Holder of Shares received pursuant to a Restricted Stock Award any Shares that are still subject to a risk of forfeiture as of the Termination Event. Such repurchase right may be exercised by the Company within six months
following the date of such Termination Event. The repurchase price shall be the lower of the original per share purchase price paid by the Holder, subject to adjustment as provided in Section 3(b) of the Plan, or the current Fair Market Value
of such Shares as of the date the Company elects to exercise its repurchase rights. 
 (iii) Procedure. Any repurchase right of the
Company shall be exercised by the Company or its assigns by giving the Holder written notice on or before the last day of the repurchase period of its intention to exercise such repurchase right. Upon such notification, the Holder shall promptly
surrender to the Company, free and clear of any liens or encumbrances, any certificates representing the Shares being purchased, together with a duly executed stock power for the transfer of such Shares to the Company or the Company’s assignee
or assignees. Upon the Company’s or its assignee’s receipt of the certificates from the Holder, the Company or its assignee or assignees shall deliver to him, her or them a check for the applicable repurchase price; provided,
however, that the Company may pay the repurchase price by offsetting and canceling any indebtedness then owed by the Holder to the Company. 

(d) Drag Along Right. In the event the holders of a majority of the Company’s equity securities then outstanding (the
“Majority Shareholders”) determine to enter into a Sale Event in a bona fide negotiated transaction (a “Sale”), with any non-Affiliate of the Company or any majority
shareholder (in each case, the “Buyer”), a Holder of Shares, including any Permitted Transferee, shall be obligated to and shall upon the written request of the Majority Shareholders: (a) sell, transfer and deliver, or cause to
be sold, transferred and delivered, to the Buyer, his or her Shares (including for this purpose all of such Holder’s Shares that presently or as a result of any such transaction may be acquired upon the exercise of an Option (following the
payment of the exercise price therefor)) on substantially the same terms applicable to the Majority Shareholders (with appropriate adjustments to reflect the conversion of convertible securities, the redemption of redeemable securities and the
exercise of exercisable securities as well as the relative preferences and priorities of preferred stock); and (b) execute and deliver such instruments of conveyance and transfer and take such other action, including voting such Shares in favor
of any Sale proposed by the Majority Shareholders and executing any purchase agreements, merger agreements, indemnity agreements, escrow agreements or related documents as the Majority Shareholders or the Buyer may reasonably require in order to
carry out the terms and provisions of this Section 9(d). 

  
 15 

 (e) Escrow Arrangement. 

(i) Escrow. In order to carry out the provisions of this Section 9 of this Plan more effectively, the Company shall hold any Shares
issued pursuant to Awards granted under the Plan in escrow together with separate stock powers executed by the Holder in blank for transfer. The Company shall not dispose of the Shares except as otherwise provided in this Plan. In the event of any
repurchase by the Company (or any of its assigns), the Company is hereby authorized by the Holder, as the Holder’s attorney-in-fact, to date and complete the stock
powers necessary for the transfer of the Shares being purchased and to transfer such Shares in accordance with the terms hereof. At such time as any Shares are no longer subject to the Company’s repurchase and first refusal rights, the Company
shall, at the written request of the Holder, deliver to the Holder a certificate representing such Shares with the balance of the Shares to be held in escrow pursuant to this Section. 

(ii) Remedy. Without limitation of any other provision of this Plan or other rights, in the event that a Holder or any other Person is
required to sell a Holder’s Shares pursuant to the provisions of Sections 9(b) or (c) hereof and in the further event that he or she refuses or for any reason fails to deliver to the Company or its designated purchaser of such Shares the
certificate or certificates evidencing such Shares together with a related stock power, the Company or such designated purchaser may deposit the applicable purchase price for such Shares with a bank designated by the Company, or with the
Company’s independent public accounting firm, as agent or trustee, or in escrow, for such Holder or other Person, to be held by such bank or accounting firm for the benefit of and for delivery to him, her, them or it, and/or, in its discretion,
pay such purchase price by offsetting any indebtedness then owed by such Holder as provided above. Upon any such deposit and/or offset by the Company or its designated purchaser of such amount and upon notice to the Person who was required to sell
the Shares to be sold pursuant to the provisions of Sections 9(b) or (c), such Shares shall at such time be deemed to have been sold, assigned, transferred and conveyed to such purchaser, such Holder shall have no further rights thereto (other than
the right to withdraw the payment thereof held in escrow, if applicable), and the Company shall record such transfer in its stock transfer book or in any appropriate manner. 

(f) Lockup Provision. If requested by the Company, a Holder shall not sell or otherwise transfer or dispose of any Shares (including,
without limitation, pursuant to Rule 144 under the Securities Act) held by him or her for such period following the effective date of a public offering by the Company of Shares as the Company shall specify reasonably and in good faith. If requested
by the underwriter engaged by the Company, each Holder shall execute a separate letter confirming his or her agreement to comply with this Section. 

(g) Adjustments for Changes in Capital Structure. If, as a result of any reorganization, recapitalization, reclassification, stock
dividend, stock split, reverse stock split or other similar change in the Common Stock, the outstanding Shares are increased or decreased or are exchanged for a different number or kind of securities of the Company, the restrictions contained in
this Section 9 shall apply with equal force to additional and/or substitute securities, if any, received by Holder in exchange for, or by virtue of his or her ownership of, Shares. 

  
 16 

 (h) Termination. The terms and provisions of Section 9(b) and Section 9(c)
(except for the Company’s right to repurchase Shares still subject to a risk of forfeiture upon a Termination Event) shall terminate upon the closing of the Company’s Initial Public Offering or upon consummation of any Sale Event, in
either case as a result of which Shares are registered under Section 12 of the Exchange Act and publicly-traded on any national security exchange. 

SECTION 10. TAX WITHHOLDING 
 (a)
Payment by Grantee. Each grantee shall, no later than the date as of which the value of an Award or of any Shares or other amounts received thereunder first becomes includable in the gross income of the grantee for income tax purposes, pay to
the Company, or make arrangements satisfactory to the Committee regarding payment of, any Federal, state, or local taxes of any kind required by law to be withheld by the Company with respect to such income. The Company and any Subsidiary shall, to
the extent permitted by law, have the right to deduct any such taxes from any payment of any kind otherwise due to the grantee. The Company’s obligation to deliver stock certificates (or evidence of book entry) to any grantee is subject to and
conditioned on any such tax withholding obligations being satisfied by the grantee. 
 (b) Payment in Stock. The Company’s
minimum required tax withholding obligation may be satisfied, in whole or in part, by the Company withholding from Shares to be issued pursuant to an Award a number of Shares having an aggregate Fair Market Value (as of the date the withholding is
effected) that would satisfy the minimum withholding amount due. 
 SECTION 11. SECTION 409A AWARDS.  

To the extent that any Award is determined to constitute “nonqualified deferred compensation” within the meaning of Section 409A
(a “409A Award”), the Award shall be subject to such additional rules and requirements as may be specified by the Committee from time to time. In this regard, if any amount under a 409A Award is payable upon a “separation from
service” (within the meaning of Section 409A) to a grantee who is considered a “specified employee” (within the meaning of Section 409A), then no such payment shall be made prior to the date that is the earlier of
(i) six months and one day after the grantee’s separation from service, or (ii) the grantee’s death, but only to the extent such delay is necessary to prevent such payment from being subject to interest, penalties and/or
additional tax imposed pursuant to Section 409A. The Company makes no representation or warranty and shall have no liability to any grantee under the Plan or any other Person with respect to any penalties or taxes under Section 409A that
are, or may be, imposed with respect to any Award. 
 SECTION 12. AMENDMENTS AND TERMINATION 

The Board may, at any time, amend or discontinue the Plan and the Committee may, at any time, amend or cancel any outstanding Award for the
purpose of satisfying changes in law or for any other lawful purpose, but no such action shall adversely affect rights under any outstanding Award without the consent of the holder of the Award. The Committee may

  
 17 

 
exercise its discretion to reduce the exercise price of outstanding Stock Options or effect repricing through cancellation of outstanding Stock Options and by granting such holders new Awards in
replacement of the cancelled Stock Options. To the extent determined by the Committee to be required either by the Code to ensure that Incentive Stock Options granted under the Plan are qualified under Section 422 of the Code or otherwise, Plan
amendments shall be subject to approval by the Company stockholders entitled to vote at a meeting of stockholders. Nothing in this Section 12 shall limit the Board’s or Committee’s authority to take any action permitted pursuant to
Section 3(c). The Board reserves the right to amend the Plan and/or the terms of any outstanding Stock Options to the extent reasonably necessary to comply with the requirements of the exemption pursuant to paragraph (f)(4) of Rule 12h-1 of the Exchange Act. 
 SECTION 13. STATUS OF PLAN 

With respect to the portion of any Award that has not been exercised and any payments in cash, Stock or other consideration not received by a
grantee, a grantee shall have no rights greater than those of a general creditor of the Company unless the Committee shall otherwise expressly so determine in connection with any Award. 

SECTION 14. GENERAL PROVISIONS 
 (a) No
Distribution; Compliance with Legal Requirements. The Committee may require each person acquiring Shares pursuant to an Award to represent to and agree with the Company in writing that such person is acquiring the Shares without a view to
distribution thereof. No Shares shall be issued pursuant to an Award until all applicable securities law and other legal and stock exchange or similar requirements have been satisfied. The Committee may require the placing of such stop-orders and
restrictive legends on certificates for Stock and Awards as it deems appropriate. 
 (b) Delivery of Stock Certificates. Stock
certificates to grantees under the Plan shall be deemed delivered for all purposes when the Company or a stock transfer agent of the Company shall have mailed such certificates in the United States mail, addressed to the grantee, at the
grantee’s last known address on file with the Company; provided that stock certificates to be held in escrow pursuant to Section 9 of the Plan shall be deemed delivered when the Company shall have recorded the issuance in its records.
Uncertificated Stock shall be deemed delivered for all purposes when the Company or a stock transfer agent of the Company shall have given to the grantee by electronic mail (with proof of receipt) or by United States mail, addressed to the grantee,
at the grantee’s last known address on file with the Company, notice of issuance and recorded the issuance in its records (which may include electronic “book entry” records). 

(c) No Employment Rights. The adoption of the Plan and the grant of Awards do not confer upon any Person any right to continued
employment or Service Relationship with the Company or any Subsidiary. 
 (d) Trading Policy Restrictions. Option exercises and other
Awards under the Plan shall be subject to the Company’s insider trading policy-related restrictions, terms and conditions as may be established by the Committee, or in accordance with policies set by the Committee, from time to time. 

  
 18 

 (e) Designation of Beneficiary. Each grantee to whom an Award has been made under the
Plan may designate a beneficiary or beneficiaries to exercise any Award on or after the grantee’s death or receive any payment under any Award payable on or after the grantee’s death. Any such designation shall be on a form provided for
that purpose by the Committee and shall not be effective until received by the Committee. If no beneficiary has been designated by a deceased grantee, or if the designated beneficiaries have predeceased the grantee, the beneficiary shall be the
grantee’s estate. 
 (f) Legend. Any certificate(s) representing the Shares shall carry substantially the following legend (and
with respect to uncertificated Stock, the book entries evidencing such shares shall contain the following notation): 
 The transferability
of this certificate and the shares of stock represented hereby are subject to the restrictions, terms and conditions (including repurchase and restrictions against transfers) contained in the
TCR2, Inc. 2015 Stock Option and Grant Plan and any agreements entered into thereunder by and between the company and the holder of this certificate (a copy of which is available at the
offices of the company for examination). 
 (g) Information to Holders of Options. In the event the Company is relying on the
exemption from the registration requirements of Section 12(g) of the Exchange Act contained in paragraph (f)(1) of Rule 12h-1 of the Exchange Act, the Company shall provide the information described in
Rule 701(e)(3), (4) and (5) of the Securities Act to all holders of Options in accordance with the requirements thereunder. The foregoing notwithstanding, the Company shall not be required to provide such information unless the optionholder has
agreed in writing, on a form prescribed by the Company, to keep such information confidential. 
 SECTION 15. EFFECTIVE DATE OF PLAN 

The Plan shall become effective upon adoption by the Board and shall be approved by stockholders in accordance with applicable state law and
the Company’s certificate of incorporation and Bylaws within 12 months thereafter. If the stockholders fail to approve the Plan within 12 months after its adoption by the Board of Directors, then any Awards granted or sold under the Plan shall
be rescinded and no additional grants or sales shall thereafter be made under the Plan. Subject to such approval by stockholders and to the requirement that no Shares may be issued hereunder prior to such approval, Stock Options and other Awards may
be granted hereunder on and after adoption of the Plan by the Board. No grants of Stock Options and other Awards may be made hereunder after the tenth anniversary of the date the Plan is adopted by the Board or the date the Plan is approved by the
Company’s stockholders, whichever is earlier. 

  
 19 

 SECTION 16. GOVERNING LAW 

This Plan, all Awards and any controversy arising out of or relating to this Plan and all Awards shall be governed by and construed in
accordance with the General Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts,
without regard to conflict of law principles that would result in the application of any law other than the law of the Commonwealth of Massachusetts. 
  

			
	DATE ADOPTED BY THE BOARD OF DIRECTORS:	  	October 16, 2015
		
	DATE APPROVED BY THE STOCKHOLDERS:	  	October 16, 2015

  
 20 

 TCR2, INC. 

AMENDMENT NO. 1 TO 
 2015
STOCK OPTION AND GRANT PLAN 
 The TCR2, Inc. 2015 Stock Option and Grant Plan (the
“Plan”) is hereby amended by the Board of Directors as follows: 
 Section 3(a) of the Plan is hereby amended to
decrease the total number of shares of Common Stock reserved and available for issuance under the Plan by 6,731,308 such that Section 3(a) of the Plan, as so amended, shall read in its entirety as follows: 

SECTION 3. STOCK ISSUABLE UNDER THE PLAN; MERGERS; SUBSTITUTION 

(a) Stock Issuable. The maximum number of Shares reserved and available for issuance under the Plan shall be 356,732 Shares,
subject to adjustment as provided in Section 3(b). For purposes of this limitation, the Shares underlying any Awards that are forfeited, canceled, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or
otherwise terminated (other than by exercise) and Shares that are withheld upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding shall be added back to the Shares available for issuance under the Plan.
Subject to such overall limitations, Shares may be issued up to such maximum number pursuant to any type or types of Award, and no more than 5,000,000 Shares may be issued pursuant to Incentive Stock Options. The Shares available for issuance under
the Plan may be authorized but unissued Shares or Shares reacquired by the Company. Beginning on the date that the Company becomes subject to Section 162(m) of the Code, Options with respect to no more than 356,732 Shares shall be granted to
any one individual in any calendar year period. 
  

			
	ADOPTED BY BOARD OF DIRECTORS:	  	May 26, 2016

  
 21 

 TCR2 THERAPEUTICS INC. 

AMENDMENT NO. 2 TO 
 2015
STOCK OPTION AND GRANT PLAN 
 The TCR2 Therapeutics Inc. 2015 Stock Option and
Grant Plan, as amended (the “Plan”) is hereby amended by the Board of Directors as follows: 
 Section 3(a) of the
Plan is hereby amended to increase the total number of Shares (as defined in the Plan) reserved and available for issuance under the Plan by 4,557,580 shares such that Section 3(a) of the Plan, as so amended, shall read in its entirety as
follows: 
 SECTION 3. STOCK ISSUABLE UNDER THE PLAN; MERGERS; SUBSTITUTION 

(a) Stock Issuable. The maximum number of Shares reserved and available for issuance under the Plan shall be 4,923,454 Shares,
subject to adjustment as provided in Section 3(b). For purposes of this limitation, the Shares underlying any Awards that are forfeited, canceled, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or
otherwise terminated (other than by exercise) and Shares that are withheld upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding shall be added back to the Shares available for issuance under the Plan.
Subject to such overall limitations, Shares may be issued up to such maximum number pursuant to any type or types of Award, and no more than 5,000,000 Shares may be issued pursuant to Incentive Stock Options. The Shares available for issuance under
the Plan may be authorized but unissued Shares or Shares reacquired by the Company. Beginning on the date that the Company becomes subject to Section 162(m) of the Code, Options with respect to no more than 4,923,454 Shares shall be granted to
any one individual in any calendar year period. 
  

			
	ADOPTED BY BOARD OF DIRECTORS:	  	December 13 2016
		
	ADOPTED BY STOCKHOLDERS:	  	December 19, 2016

  
 22 

 TCR2 THERAPEUTICS INC. 

AMENDMENT NO. 3 TO 
 2015
STOCK OPTION AND GRANT PLAN 
 The TCR2 Therapeutics Inc. 2015 Stock Option and
Grant Plan, as amended (the “Plan”) is hereby amended by the Board of Directors as follows: 
 Section 3(a) of the
Plan is hereby amended to increase the total number of Shares (as defined in the Plan) reserved and available for issuance under the Plan by 4,557,580 shares such that Section 3(a) of the Plan, as so amended, shall read in its entirety as
follows: 
 SECTION 3. STOCK ISSUABLE UNDER THE PLAN; MERGERS; SUBSTITUTION 

(a) Stock Issuable. The maximum number of Shares reserved and available for issuance under the Plan shall be 7,823,454 Shares,
subject to adjustment as provided in Section 3(b). For purposes of this limitation, the Shares underlying any Awards that are forfeited, canceled, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or
otherwise terminated (other than by exercise) and Shares that are withheld upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding shall be added back to the Shares available for issuance under the Plan.
Subject to such overall limitations, Shares may be issued up to such maximum number pursuant to any type or types of Award, and no more than 7,823,454 Shares may be issued pursuant to Incentive Stock Options. The Shares available for issuance under
the Plan may be authorized but unissued Shares or Shares reacquired by the Company. Beginning on the date that the Company becomes subject to Section 162(m) of the Code, Options with respect to no more than 7,823,454 Shares shall be granted to
any one individual in any calendar year period. 
  

			
	ADOPTED BY BOARD OF DIRECTORS:	  	December 6, 2017
		
	ADOPTED BY STOCKHOLDERS:	  	December 6, 2017

  
 23 

 TCR2 THERAPEUTICS INC. 

AMENDMENT NO. 4 TO 
 2015
STOCK OPTION AND GRANT PLAN 
 The TCR2 Therapeutics Inc. 2015 Stock Option and
Grant Plan, as amended (the “Plan”) is hereby amended by the Board of Directors as follows: 
 Section 3(a) of the
Plan is hereby amended to increase the total number of Shares (as defined in the Plan) reserved and available for issuance under the Plan by 5,000,000 shares such that Section 3(a) of the Plan, as so amended, shall read in its entirety as
follows: 
 SECTION 3. STOCK ISSUABLE UNDER THE PLAN; MERGERS; SUBSTITUTION 

(a) Stock Issuable. The maximum number of Shares reserved and available for issuance under the Plan shall be 12,823,454 Shares,
subject to adjustment as provided in Section 3(b). For purposes of this limitation, the Shares underlying any Awards that are forfeited, canceled, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or
otherwise terminated (other than by exercise) and Shares that are withheld upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding shall be added back to the Shares available for issuance under the Plan.
Subject to such overall limitations, Shares may be issued up to such maximum number pursuant to any type or types of Award, and no more than 12,823,454 Shares may be issued pursuant to Incentive Stock Options. The Shares available for issuance under
the Plan may be authorized but unissued Shares or Shares reacquired by the Company. Beginning on the date that the Company becomes subject to Section 162(m) of the Code, Options with respect to no more than 12,823,454 Shares shall be granted to
any one individual in any calendar year period. 
 ADOPTED BY BOARD OF DIRECTORS: February 28, 2018 

ADOPTED BY STOCKHOLDERS: February 28, 2018 

  
 24 

 TCR2 THERAPEUTICS INC. 

AMENDMENT NO. 5 TO 
 2015
STOCK OPTION AND GRANT PLAN 
 The TCR2 Therapeutics Inc. 2015 Stock Option and
Grant Plan, as amended (the “Plan”) is hereby amended by the Board of Directors as follows: 
 Section 3(a) of the
Plan is hereby amended to increase the total number of Shares (as defined in the Plan) reserved and available for issuance under the Plan by 3,000,000 shares such that Section 3(a) of the Plan, as so amended, shall read in its entirety as
follows: 
 SECTION 3. STOCK ISSUABLE UNDER THE PLAN; MERGERS; SUBSTITUTION 

(a) Stock Issuable. The maximum number of Shares reserved and available for issuance under the Plan shall be 15,823,454 Shares,
subject to adjustment as provided in Section 3(b). For purposes of this limitation, the Shares underlying any Awards that are forfeited, canceled, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or
otherwise terminated (other than by exercise) and Shares that are withheld upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding shall be added back to the Shares available for issuance under the Plan.
Subject to such overall limitations, Shares may be issued up to such maximum number pursuant to any type or types of Award, and no more than 15,823,454 Shares may be issued pursuant to Incentive Stock Options. The Shares available for issuance under
the Plan may be authorized but unissued Shares or Shares reacquired by the Company. Beginning on the date that the Company becomes subject to Section 162(m) of the Code, Options with respect to no more than 15,823,454 Shares shall be granted to
any one individual in any calendar year period. 
 ADOPTED BY BOARD OF DIRECTORS: July 26, 2018 

  
 25 

 INCENTIVE STOCK OPTION GRANT NOTICE 

UNDER THE TCR2 THERAPEUTICS INC. 

2015 STOCK OPTION AND GRANT PLAN 

Pursuant to the TCR2 Therapeutics Inc. 2015 Stock Option and Grant Plan (the
“Plan”), TCR2 Therapeutics Inc., a Delaware corporation (together with any successor, the “Company”), has granted to the individual named below, an option (the “Stock
Option”) to purchase on or prior to the Expiration Date, or such earlier date as is specified herein, all or any part of the number of shares of Common Stock, par value $0.0001 per share (“Common Stock”), of the Company indicated
below (the “Shares”), at the Option Exercise Price per share, subject to the terms and conditions set forth in this Incentive Stock Option Grant Notice (the “Grant Notice”), the attached Incentive Stock Option Agreement (the
“Agreement”) and the Plan. This Stock Option is intended to qualify as an “incentive stock option” as defined in Section 422(b) of the Internal Revenue Code of 1986, as amended from time to time (the “Code”). To
the extent that any portion of the Stock Option does not so qualify, it shall be deemed a non-qualified stock option. 
  

			
	Name of Optionee:	  	__________________ (the “Optionee”)
		
	No. of Shares:	  	__________ Shares of Common Stock
		
	Grant Date:	  	__________________
		
	Vesting Commencement Date:	  	__________________ (the “Vesting Commencement Date”)
		
	Expiration Date:	  	__________________ (the “Expiration Date”)
		
	Option Exercise Price/Share:	  	$_________________ (the “Option Exercise Price”)
		
	Vesting Schedule:	  	25 percent of the Shares shall vest and become exercisable on the first anniversary of the Vesting Commencement Date; provided that the Optionee continues to have a Service Relationship with the Company at such time.
Thereafter, the remaining 75 percent of the Shares shall vest and become exercisable in 36 equal monthly installments following the first anniversary of the Vesting Commencement Date until [_____________], on which date, subject to the vesting
conditions herein, all remaining Shares shall vest, provided the Optionee continues to have a Service Relationship with the Company on each vesting date. Notwithstanding anything in the Agreement to the contrary, in the case of a Sale Event, this
Stock Option and the Shares shall be treated as provided in Section 3(c) of the Plan.

 Attachments: Incentive Stock Option Agreement, 2015 Stock Option and Grant Plan 

  
 26 

 INCENTIVE STOCK OPTION AGREEMENT 

UNDER THE TCR2 THERAPEUTICS INC. 

2015 STOCK OPTION AND GRANT PLAN 

All capitalized terms used herein and not otherwise defined shall have the respective meanings set forth in the Grant Notice and the Plan.

 1. VESTING, EXERCISABILITY AND TERMINATION.  

(a) No portion of this Stock Option may be exercised until such portion shall have vested and become exercisable. 

(b) Except as set forth below, and subject to the determination of the Committee in its sole discretion to accelerate the vesting schedule
hereunder, this Stock Option shall be vested and exercisable on the respective dates indicated below: 
 (i) This Stock
Option shall initially be unvested and unexercisable. 
 (ii) This Stock Option shall vest and become exercisable in
accordance with the Vesting Schedule set forth in the Grant Notice. 
 (c) Termination. Except as may otherwise be provided by the
Committee, if the Optionee’s Service Relationship is terminated, the period within which to exercise this Stock Option will be subject to earlier termination as set forth below (and if not exercised within such period, shall thereafter
terminate subject, in each case, to Section 3(c) of the Plan): 
 (i) Termination Due to Death or Disability. If
the Optionee’s Service Relationship terminates by reason of such Optionee’s death or Disability, this Stock Option may be exercised, to the extent exercisable on the date of such termination, by the Optionee, the Optionee’s legal
representative or legatee for a period of 12 months from the date of death or Disability or until the Expiration Date, if earlier. 

(ii) Other Termination. If the Optionee’s Service Relationship terminates for any reason other than death or
Disability, and unless otherwise determined by the Committee, this Stock Option may be exercised, to the extent exercisable on the date of termination, for a period of 90 days from the date of termination or until the Expiration Date, if earlier;
provided however, if the Optionee’s Service Relationship is terminated for Cause, this Stock Option shall terminate immediately upon the date of such termination. 

For purposes hereof, the Committee’s determination of the reason for termination of the Optionee’s Service Relationship shall be
conclusive and binding on the Optionee and his or her representatives or legatees. Any portion of this Stock Option that is not vested and exercisable on the date of termination of the Service Relationship shall terminate immediately and be null and
void. 

  
 27 

 (d) It is understood and intended that this Stock Option is intended to qualify as an
“incentive stock option” as defined in Section 422 of the Code to the extent permitted under applicable law. Accordingly, the Optionee understands that in order to obtain the benefits of an incentive stock option under
Section 422 of the Code, no sale or other disposition may be made of Shares for which incentive stock option treatment is desired within the one-year period beginning on the day after the day of the
transfer of such Shares to him or her, nor within the two-year period beginning on the day after Grant Date of this Stock Option and further that this Stock Option must be exercised within three months after
termination of employment as an employee (or 12 months in the case of death or disability) to qualify as an incentive stock option. If the Optionee disposes (whether by sale, gift, transfer or otherwise) of any such Shares within either of these
periods, he or she will notify the Company within 30 days after such disposition. The Optionee also agrees to provide the Company with any information concerning any such dispositions required by the Company for tax purposes. Further, to the extent
this Stock Option and any other incentive stock options of the Optionee having an aggregate Fair Market Value in excess of $100,000 (determined as of the Grant Date) first become exercisable in any year, such options will not qualify as incentive
stock options. 
 2. EXERCISE OF STOCK OPTION. 

(a) The Optionee may exercise this Stock Option only in the following manner: Prior to the Expiration Date, the Optionee may deliver a Stock
Option exercise notice (an “Exercise Notice”) in the form of Appendix A hereto indicating his or her election to purchase some or all of the Shares with respect to which this Stock Option is then exercisable. Such
notice shall specify the number of Shares to be purchased. Payment of the purchase price may be made by one or more of the methods described in Section 5 of the Plan, subject to the limitations contained in such Section of the Plan, including
the requirement that the Committee specifically approve in advance certain payment methods. 
 (b) Notwithstanding any other provision
hereof or of the Plan, no portion of this Stock Option shall be exercisable after the Expiration Date. 
 3. INCORPORATION OF PLAN.
Notwithstanding anything herein to the contrary, this stock option shall be subject to and governed by all the terms and conditions of the plan. 

4. TRANSFERABILITY OF STOCK OPTION. This stock option is personal to the optionee and is not transferable by the optionee in any manner
other than by will or by the laws of descent and distribution. The stock option may be exercised during the optionee’s lifetime only by the optionee (or by the optionee’s guardian or personal representative in the event of the
optionee’s incapacity). The optionee may elect to designate a beneficiary by providing written notice of the name of such beneficiary to the company, and may revoke or change such designation at any time by filing written notice of revocation
or change with the company; such beneficiary may exercise the optionee’s stock option in the event of the optionee’s death to the extent provided herein. If the optionee does not designate a beneficiary, or if the designated beneficiary
predeceases the optionee, the legal representative of the optionee may exercise this stock option to the extent provided herein in the event of the optionee’s death. 

  
 28 

 5. RESTRICTIONS ON TRANSFER OF SHARES. The shares acquired upon exercise of the stock
option shall be subject to certain transfer restrictions and other limitations including, without limitation, the provisions contained in section 9 of the plan. 

6. MISCELLANEOUS PROVISIONS. 

(a) Equitable Relief. The parties hereto agree and declare that legal remedies may be inadequate to enforce the provisions of this
Agreement and that equitable relief, including specific performance and injunctive relief, may be used to enforce the provisions of this Agreement. 

(b) Adjustments for Changes in Capital Structure. If, as a result of any reorganization, recapitalization, reincorporation,
reclassification, stock dividend, stock split, reverse stock split or other similar change in the Common Stock, the outstanding shares of Common Stock are increased or decreased or are exchanged for a different number or kind of securities of the
Company, the restrictions contained in this Agreement shall apply with equal force to additional and/or substitute securities, if any, received by the Optionee in exchange for, or by virtue of his or her ownership of, this Stock Option or Shares
acquired pursuant thereto. 
 (c) Change and Modifications. This Agreement may not be orally changed, modified or terminated, nor
shall any oral waiver of any of its terms be effective. This Agreement may be changed, modified or terminated only by an agreement in writing signed by the Company and the Optionee. 

(d) Governing Law. This Agreement shall be governed by and construed in accordance with the General Corporation Law of the State of
Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to conflict of law principles that would result
in the application of any law other than the law of the Commonwealth of Massachusetts. 
 (e) Headings. The headings are intended only
for convenience in finding the subject matter and do not constitute part of the text of this Agreement and shall not be considered in the interpretation of this Agreement. 

(f) Saving Clause. If any provision(s) of this Agreement shall be determined to be illegal or unenforceable, such determination shall in
no manner affect the legality or enforceability of any other provision hereof. 
 (g) Notices. All notices, requests, consents and
other communications shall be in writing and be deemed given when delivered personally, by telex or facsimile transmission or when received if mailed by first class registered or certified mail, postage prepaid. Notices to the Company or the
Optionee shall be addressed as set forth underneath their signatures below, or to such other address or addresses as may have been furnished by such party in writing to the other. 

  
 29 

 (h) Benefit and Binding Effect. This Agreement shall be binding upon and shall inure
to the benefit of the parties hereto, their respective successors, assigns, and legal representatives. The Company has the right to assign this Agreement, and such assignee shall become entitled to all the rights of the Company hereunder to the
extent of such assignment. 
 (i) Counterparts. For the convenience of the parties and to facilitate execution, this Agreement may be
executed in two or more counterparts, each of which shall be deemed an original, but all of which shall constitute one and the same document. 

(j) Integration. This Agreement constitutes the entire agreement between the parties with respect to this Stock Option and supersedes
all prior agreements and discussions between the parties concerning such subject matter. 
 7. DISPUTE RESOLUTION. 

(a) Except as provided below, any dispute arising out of or relating to the Plan or this Stock Option, this Agreement, or the breach,
termination or validity of the Plan, this Stock Option or this Agreement, shall be finally settled by binding arbitration conducted expeditiously in accordance with the J.A.M.S./Endispute Comprehensive Arbitration Rules and Procedures (the
“J.A.M.S. Rules”). The arbitration shall be governed by the United States Arbitration Act, 9 U.S.C. Sections 1 16, and judgment upon the award rendered by the arbitrators may be entered by any court having jurisdiction thereof. The place
of arbitration shall be Boston, Massachusetts. 
 (b) The arbitration shall commence within 60 days of the date on which a written demand for
arbitration is filed by any party hereto. In connection with the arbitration proceeding, the arbitrator shall have the power to order the production of documents by each party and any third-party witnesses. In addition, each party may take up to
three depositions as of right, and the arbitrator may in his or her discretion allow additional depositions upon good cause shown by the moving party. However, the arbitrator shall not have the power to order the answering of interrogatories or the
response to requests for admission. In connection with any arbitration, each party to the arbitration shall provide to the other, no later than seven business days before the date of the arbitration, the identity of all persons that may testify at
the arbitration and a copy of all documents that may be introduced at the arbitration or considered or used by a party’s witness or expert. The arbitrator’s decision and award shall be made and delivered within six months of the selection
of the arbitrator. The arbitrator’s decision shall set forth a reasoned basis for any award of damages or finding of liability. The arbitrator shall not have power to award damages in excess of actual compensatory damages and shall not multiply
actual damages or award punitive damages, and each party hereby irrevocably waives any claim to such damages. 
 (c) The Company, the
Optionee, each party to the Agreement and any other holder of Shares issued pursuant to this Agreement (each, a “Party”) covenants and agrees that such party will participate in the arbitration in good faith. This Section 7 applies
equally to requests for temporary, preliminary or permanent injunctive relief, except that in the case of temporary or preliminary injunctive relief any party may proceed in court without prior arbitration for the limited purpose of avoiding
immediate and irreparable harm. 

  
 30 

 (d) Each Party (i) hereby irrevocably submits to the jurisdiction of any United States
District Court of competent jurisdiction for the purpose of enforcing the award or decision in any such proceeding, (ii) hereby waives, and agrees not to assert, by way of motion, as a defense, or otherwise, in any such suit, action or
proceeding, any claim that it is not subject personally to the jurisdiction of the above named courts, that its property is exempt or immune from attachment or execution (except as protected by applicable law), that the suit, action or proceeding is
brought in an inconvenient forum, that the venue of the suit, action or proceeding is improper or that this Agreement or the subject matter hereof may not be enforced in or by such court, and (iii) hereby waives and agrees not to seek any
review by any court of any other jurisdiction which may be called upon to grant an enforcement of the judgment of any such court. Each Party hereby consents to service of process by registered mail at the address to which notices are to be given.
Each Party agrees that its, his or her submission to jurisdiction and its, his or her consent to service of process by mail is made for the express benefit of each other Party. Final judgment against any Party in any such action, suit or proceeding
may be enforced in other jurisdictions by suit, action or proceeding on the judgment, or in any other manner provided by or pursuant to the laws of such other jurisdiction. 

8. WAIVER OF STATUTORY INFORMATION RIGHTS. The optionee understands and agrees that, but for the waiver made herein, the optionee
would be entitled, upon written demand under oath stating the purpose thereof, to inspect for any proper purpose, and to make copies and extracts from, the company’s stock ledger, a list of its stockholders, and its other books and records, and
the books and records of subsidiaries of the company, if any, under the circumstances and in the manner provided in section 220 of the general corporation law of delaware (any and all such rights, and any and all such other rights of the optionee as
may be provided for in section 220, the “inspection rights”). In light of the foregoing, until the first sale of stock of the company to the general public pursuant to a registration statement filed with and declared effective by the
securities and exchange commission under the securities act, the optionee hereby unconditionally and irrevocably waives the inspection rights, whether such inspection rights would be exercised or pursued directly or indirectly pursuant to section
220 or otherwise, and covenants and agrees never to directly or indirectly commence, voluntarily aid in any way, prosecute, assign, transfer, or cause to be commenced any claim, action, cause of action, or other proceeding to pursue or exercise the
inspection rights. The foregoing waiver shall not affect any rights of a director, in his or her capacity as such, under section 220. The foregoing waiver shall not apply to any contractual inspection rights of the optionee under any other written
agreement between the optionee and the company. 
 [SIGNATURE PAGE FOLLOWS] 

  
 31 

 The foregoing Agreement is hereby accepted and the terms and conditions thereof hereby
agreed to by the undersigned as of the date first above written. 
  

			
	TCR2 Therapeutics Inc.
		
	By:	 	              

		 	Name:
		 	Title:
	
	Address:
	
	  

	
	  

	
	  

 The undersigned hereby acknowledges receiving and reviewing a copy of the Plan, including, without limitation,
Section 9 thereof, and understands that this Stock Option is subject to the terms of the Plan and of this Agreement. This Agreement is hereby accepted, and the terms and conditions of the Plan, the Grant Notice and this Agreement, SPECIFICALLY
INCLUDING THE ARBITRATION PROVISIONS SET FORTH IN SECTION 7 AND THE WAIVER OF STATUTORY INFORMATION RIGHTS SET FORTH IN SECTION 8 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 

 

	
	OPTIONEE:
	
	  

	Name:
	
	Address:
	
	  

	
	  

	
	  

  
 32 

 [SPOUSE’S CONSENT1 

I acknowledge that I have read the 
 foregoing Incentive Stock
Option Agreement 
 and understand the contents thereof. 

____________________________________] 
  

	1 	 A spouse’s consent is recommended only if the Optionee’s state of residence is one of the following
community property states: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington and Wisconsin. 

  
 33 

 
	
	DESIGNATED BENEFICIARY:
	
	  

	
	Beneficiary’s Address:
	
	  

	
	  

	
	  

  
 34 

 Appendix A 

STOCK OPTION EXERCISE NOTICE 
 TCR2 Therapeutics Inc. 
 Attention: Treasurer 

                          
                                         
  

                          
                                         
  
 Pursuant to the terms of the grant notice and stock option agreement between the undersigned and TCR2 Therapeutics Inc. (the “Company”) dated __________ (the “Agreement”) under the TCR2 Therapeutics Inc. 2015 Stock Option
and Grant Plan, I, [Insert Name] ________________, hereby [Circle One] partially/fully exercise such option by including herein payment in the amount of $______ representing the purchase price for [Fill in number of Shares] _______ Shares. I have
chosen the following form(s) of payment: 
  

					
	[ ]	  	1.	  	Cash
	[ ]	  	2.	  	Certified or bank check payable to TCR2 Therapeutics Inc.
	[ ]	  	3.	  	Other (as referenced in the Agreement and described in the Plan (please describe)) _____________________________________________________.

 In connection with my exercise of the option as set forth above, I hereby represent and warrant to the
Company as follows: 
 (i) I am purchasing the Shares for my own account for investment only, and not for resale or with a
view to the distribution thereof. 
 (ii) I have had such an opportunity as I have deemed adequate to obtain from the Company
such information as is necessary to permit me to evaluate the merits and risks of my investment in the Company and have consulted with my own advisers with respect to my investment in the Company. 

(iii) I have sufficient experience in business, financial and investment matters to be able to evaluate the risks involved in
the purchase of the Shares and to make an informed investment decision with respect to such purchase. 
 (iv) I can afford a
complete loss of the value of the Shares and am able to bear the economic risk of holding such Shares for an indefinite period of time. 

(v) I understand that the Shares may not be registered under the Securities Act of 1933 (it being understood that the Shares
are being issued and sold in reliance on the exemption provided in Rule 701 thereunder) or any applicable state securities or “blue sky” laws and may not be sold or otherwise transferred or disposed of in the absence of an effective
registration statement under the Securities Act of 1933 and under any applicable state securities or “blue sky” laws (or exemptions from the registration requirement thereof). I further acknowledge that certificates representing Shares
will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Shares will include similar restrictive notations. 

  
 35 

 (vi) I have read and understand the Plan and acknowledge and agree that the
Shares are subject to all of the relevant terms of the Plan, including without limitation, the transfer restrictions set forth in Section 9 of the Plan. 

(vii) I understand and agree that the Company has a right of first refusal with respect to the Shares pursuant to
Section 9(b) of the Plan. 
 (viii) I understand and agree that the Company has certain repurchase rights with respect
to the Shares pursuant to Section 9(c) of the Plan. 
 (ix) I understand and agree that I may not sell or otherwise
transfer or dispose of the Shares for a period of time following the effective date of a public offering by the Company as described in Section 9(f) of the Plan. 

(x) I waive any and all rights that I or my proxy may or do have under Section 220 of the General Corporation Law of
Delaware (“Section 220”) to inspect, make copies of, extract from, or obtain any information in any format regarding the Company’s or a subsidiary’s stock ledger, financial information, statements or audits, or other books
and records, whether or not for a legitimate financial planning or other proper purpose. I have had sufficient opportunity to consult with my own advisers with respect to the aforementioned waiver and understand and agree that the Company will not
be obligated to provide information requested pursuant to Section 220 unless it voluntarily chooses to do so or following the effective date of a public offering by the Company. 

(xi) I understand and agree that, if requested by the Company at its sole discretion, as a condition to the issuance of the
Shares hereunder, I will become a party to: 
 (A) that certain Right of First Refusal and
Co-Sale Agreement between the Company and certain of its stockholders dated as of October 16, 2015, for so long as such agreement is in effect and as the same may be amended or amended and restated from
time to time (the “Right of First Refusal and Co-Sale Agreement”), and I shall thereby be bound by, and subject to, all the terms and provisions of the Right of First Refusal and Co-Sale Agreement applicable to a Key Holder thereunder, and that I will execute a counterpart signature page thereto promptly upon such request; and 

(B) that certain Voting Agreement between the Company and certain of its stockholders dated as of October 16, 2015, for so
long as such agreement is in effect and as the same may be amended or amended and restated from time to time (the “Voting Agreement”), and I shall thereby be bound by, and subject to, all the terms and provisions of the Voting Agreement
applicable to a Key Holder thereunder, and that I will execute an Adoption Agreement thereto promptly upon such request. 

  
 36 

 
			
	Sincerely yours,
	
	  

	Name:
	
	Address:
	
	  

	
	  

	
	  

		
	Date:	 	              

  
 37 

 NON-QUALIFIED STOCK OPTION GRANT NOTICE 

UNDER THE TCR2 THERAPEUTICS INC. 

2015 STOCK OPTION AND GRANT PLAN 

Pursuant to the TCR2 Therapeutics Inc. 2015 Stock Option and Grant Plan (the
“Plan”), TCR2 Therapeutics Inc., a Delaware corporation (together with any successor, the “Company”), has granted to the individual named below, an option (the “Stock
Option”) to purchase on or prior to the Expiration Date, or such earlier date as is specified herein, all or any part of the number of shares of Common Stock, par value $0.0001 per share (“Common Stock”), of the Company indicated
below (the “Shares”), at the Option Exercise Price per share, subject to the terms and conditions set forth in this Non-Qualified Stock Option Grant Notice (the “Grant Notice”), the
attached Non-Qualified Stock Option Agreement (the “Agreement”) and the Plan. This Stock Option is not intended to qualify as an “incentive stock option” as defined in Section 422(b)
of the Internal Revenue Code of 1986, as amended from time to time (the “Code”). 
  

			
	Name of Optionee:	  	__________________ (the “Optionee”)
		
	No. of Shares:	  	__________ Shares of Common Stock
		
	Grant Date:	  	__________________
		
	Vesting Commencement Date:	  	__________________ (the “Vesting Commencement Date”)
		
	Expiration Date:	  	__________________ (the “Expiration Date”)
		
	Option Exercise Price/Share:	  	$_________________ (the “Option Exercise Price”)
		
	Vesting Schedule:	  	25 percent of the Shares shall vest and become exercisable on the first anniversary of the Vesting Commencement Date; provided that the Optionee continues to have a Service Relationship with the Company at such time.
Thereafter, the remaining 75 percent of the Shares shall vest and become exercisable in 36 equal monthly installments following the first anniversary of the Vesting Commencement Date until [____________], on which date, subject to the vesting
conditions herein, all remaining Shares shall vest and become exerciseable, provided the Optionee continues to have a Service Relationship with the Company on each vesting date. Notwithstanding anything in the Agreement to the contrary, in the case
of a Sale Event, this Stock Option and the Shares shall be treated as provided in Section 3(c) of the Plan.

 Attachments: Non-Qualified Stock Option Agreement, 2015 Stock Option and Grant
Plan 

  
 38 

 NON-QUALIFIED STOCK OPTION AGREEMENT 

UNDER THE TCR2 THERAPEUTICS INC. 

2015 STOCK OPTION AND GRANT PLAN 

All capitalized terms used herein and not otherwise defined shall have the respective meanings set forth in the Grant Notice and the Plan.

 SECTION 1. VESTING, EXERCISABILITY AND TERMINATION.  

(a) No portion of this Stock Option may be exercised until such portion shall have vested and become exercisable. 

(b) Except as set forth below, and subject to the determination of the Committee in its sole discretion to accelerate the vesting schedule
hereunder, this Stock Option shall be vested and exercisable on the respective dates indicated below: 
 (i) This Stock Option shall
initially be unvested and unexercisable. 
 (ii) This Stock Option shall vest and become exercisable in accordance with the Vesting Schedule
set forth in the Grant Notice. 
 (c) Termination. Except as may otherwise be provided by the Committee, if the Optionee’s
Service Relationship is terminated, the period within which to exercise this Stock Option will be subject to earlier termination as set forth below (and if not exercised within such period, shall thereafter terminate subject, in each case, to
Section 3(c) of the Plan): 
 (i) Termination Due to Death or Disability. If the Optionee’s Service Relationship terminates
by reason of such Optionee’s death or Disability, this Stock Option may be exercised, to the extent exercisable on the date of such termination, by the Optionee, the Optionee’s legal representative or legatee for a period of 12 months from
the date of death or Disability or until the Expiration Date, if earlier. 
 (ii) Other Termination. If the Optionee’s Service
Relationship terminates for any reason other than death or Disability, and unless otherwise determined by the Committee, this Stock Option may be exercised, to the extent exercisable on the date of termination, for a period of 90 days from the date
of termination or until the Expiration Date, if earlier; provided however, if the Optionee’s Service Relationship is terminated for Cause, this Stock Option shall terminate immediately upon the date of such termination. 

For purposes hereof, the Committee’s determination of the reason for termination of the Optionee’s Service Relationship shall be
conclusive and binding on the Optionee and his or her representatives or legatees and any Permitted Transferee. Any portion of this Stock Option that is not vested and exercisable on the date of termination of the Service Relationship shall
terminate immediately and be null and void. 

  
 39 

 SECTION 2. EXERCISE OF STOCK OPTION. 

(a) The Optionee may exercise this Stock Option only in the following manner: Prior to the Expiration Date, the Optionee may deliver a Stock
Option exercise notice (an “Exercise Notice”) in the form of Appendix A hereto indicating his or her election to purchase some or all of the Shares with respect to which this Stock Option is then exercisable. Such
notice shall specify the number of Shares to be purchased. Payment of the purchase price may be made by one or more of the methods described in Section 5 of the Plan, subject to the limitations contained in such Section of the Plan, including
the requirement that the Committee specifically approve in advance certain payment methods. 
 (b) Notwithstanding any other provision hereof
or of the Plan, no portion of this Stock Option shall be exercisable after the Expiration Date. 
 SECTION 3. INCORPORATION OF PLAN. Notwithstanding
anything herein to the contrary, this stock option shall be subject to and governed by all the terms and conditions of the plan. 
 SECTION 4.
TRANSFERABILITY OF STOCK OPTION. This stock option is personal to the optionee and is not transferable by the optionee in any manner other than by will or by the laws of descent and distribution. The stock option may be exercised during the
optionee’s lifetime only by the optionee (or by the optionee’s guardian or personal representative in the event of the optionee’s incapacity). The optionee may elect to designate a beneficiary by providing written notice of the name
of such beneficiary to the company, and may revoke or change such designation at any time by filing written notice of revocation or change with the company; such beneficiary may exercise the optionee’s stock option in the event of the
optionee’s death to the extent provided herein. If the optionee does not designate a beneficiary, or if the designated beneficiary predeceases the optionee, the legal representative of the optionee may exercise this stock option to the extent
provided herein in the event of the optionee’s death. 
 SECTION 5. RESTRICTIONS ON TRANSFER OF SHARES. The shares acquired upon exercise of the
stock option shall be subject to certain transfer restrictions and other limitations including, without limitation, the provisions contained in section 9 of the plan. 

SECTION 6. MISCELLANEOUS PROVISIONS. 
 (a)
Equitable Relief. The parties hereto agree and declare that legal remedies may be inadequate to enforce the provisions of this Agreement and that equitable relief, including specific performance and injunctive relief, may be used to enforce
the provisions of this Agreement. 
 (b) Adjustments for Changes in Capital Structure. If, as a result of any reorganization,
recapitalization, reincorporation, reclassification, stock dividend, stock split, reverse stock split or other similar change in the Common Stock, the outstanding shares of Common Stock are increased or decreased or are exchanged for a different
number or kind of securities of the Company, the restrictions contained in this Agreement shall apply with equal force to additional and/or substitute securities, if any, received by the Optionee in exchange for, or by virtue of his or her ownership
of, this Stock Option or Shares acquired pursuant thereto. 

  
 40 

 (c) Change and Modifications. This Agreement may not be orally changed, modified or
terminated, nor shall any oral waiver of any of its terms be effective. This Agreement may be changed, modified or terminated only by an agreement in writing signed by the Company and the Optionee. 

(d) Governing Law. This Agreement shall be governed by and construed in accordance with the General Corporation Law of the State of
Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to conflict of law principles that would result
in the application of any law other than the law of the Commonwealth of Massachusetts. 
 (e) Headings. The headings are intended only
for convenience in finding the subject matter and do not constitute part of the text of this Agreement and shall not be considered in the interpretation of this Agreement. 

(f) Saving Clause. If any provision(s) of this Agreement shall be determined to be illegal or unenforceable, such determination shall in
no manner affect the legality or enforceability of any other provision hereof. 
 (g) Notices. All notices, requests, consents and
other communications shall be in writing and be deemed given when delivered personally, by telex or facsimile transmission or when received if mailed by first class registered or certified mail, postage prepaid. Notices to the Company or the
Optionee shall be addressed as set forth underneath their signatures below, or to such other address or addresses as may have been furnished by such party in writing to the other. 

(h) Benefit and Binding Effect. This Agreement shall be binding upon and shall inure to the benefit of the parties hereto, their
respective successors, assigns, and legal representatives. The Company has the right to assign this Agreement, and such assignee shall become entitled to all the rights of the Company hereunder to the extent of such assignment. 

(i) Counterparts. For the convenience of the parties and to facilitate execution, this Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which shall constitute one and the same document. 
 (j)
Integration. This Agreement constitutes the entire agreement between the parties with respect to this Stock Option and supersedes all prior agreements and discussions between the parties concerning such subject matter. 

SECTION 7. DISPUTE RESOLUTION. 
 (a)
Except as provided below, any dispute arising out of or relating to the Plan or this Stock Option, this Agreement, or the breach, termination or validity of the Plan, this Stock Option or this Agreement, shall be finally settled by binding
arbitration conducted expeditiously in accordance with the J.A.M.S./Endispute Comprehensive Arbitration Rules and Procedures (the “J.A.M.S. Rules”). The arbitration shall be governed by the United States Arbitration Act, 9 U.S.C. Sections 1-16, and judgment upon the award rendered by the arbitrators may be entered by any court having jurisdiction thereof. The place of arbitration shall be Boston, Massachusetts. 

  
 41 

 (b) The arbitration shall commence within 60 days of the date on which a written demand for
arbitration is filed by any party hereto. In connection with the arbitration proceeding, the arbitrator shall have the power to order the production of documents by each party and any third-party witnesses. In addition, each party may take up to
three depositions as of right, and the arbitrator may in his or her discretion allow additional depositions upon good cause shown by the moving party. However, the arbitrator shall not have the power to order the answering of interrogatories or the
response to requests for admission. In connection with any arbitration, each party to the arbitration shall provide to the other, no later than seven business days before the date of the arbitration, the identity of all persons that may testify at
the arbitration and a copy of all documents that may be introduced at the arbitration or considered or used by a party’s witness or expert. The arbitrator’s decision and award shall be made and delivered within six months of the selection
of the arbitrator. The arbitrator’s decision shall set forth a reasoned basis for any award of damages or finding of liability. The arbitrator shall not have power to award damages in excess of actual compensatory damages and shall not multiply
actual damages or award punitive damages, and each party hereby irrevocably waives any claim to such damages. 
 (c) The Company, the
Optionee, each party to the Agreement and any other holder of Shares issued pursuant to this Agreement (each, a “Party”) covenants and agrees that such party will participate in the arbitration in good faith. This Section 7 applies
equally to requests for temporary, preliminary or permanent injunctive relief, except that in the case of temporary or preliminary injunctive relief any party may proceed in court without prior arbitration for the limited purpose of avoiding
immediate and irreparable harm. 
 (d) Each Party (i) hereby irrevocably submits to the jurisdiction of any United States District Court
of competent jurisdiction for the purpose of enforcing the award or decision in any such proceeding, (ii) hereby waives, and agrees not to assert, by way of motion, as a defense, or otherwise, in any such suit, action or proceeding, any claim
that it is not subject personally to the jurisdiction of the above named courts, that its property is exempt or immune from attachment or execution (except as protected by applicable law), that the suit, action or proceeding is brought in an
inconvenient forum, that the venue of the suit, action or proceeding is improper or that this Agreement or the subject matter hereof may not be enforced in or by such court, and (iii) hereby waives and agrees not to seek any review by any court
of any other jurisdiction which may be called upon to grant an enforcement of the judgment of any such court. Each Party hereby consents to service of process by registered mail at the address to which notices are to be given. Each Party agrees that
its, his or her submission to jurisdiction and its, his or her consent to service of process by mail is made for the express benefit of each other Party. Final judgment against any Party in any such action, suit or proceeding may be enforced in
other jurisdictions by suit, action or proceeding on the judgment, or in any other manner provided by or pursuant to the laws of such other jurisdiction. 

SECTION 8. WAIVER OF STATUTORY INFORMATION RIGHTS. The optionee understands and agrees that, but for the waiver made herein, the optionee would be
entitled, upon written demand under oath stating the purpose thereof, to inspect for any proper purpose, and to make copies and extracts from, the company’s stock ledger, a list of its stockholders, and its other books and records, and the
books and records of subsidiaries of the company, if any, under the circumstances and in the manner provided in section 220 of the general corporation law of 

  
 42 

 
delaware (any and all such rights, and any and all such other rights of the optionee as may be provided for in section 220, the “inspection rights”). In light of the foregoing, until
the first sale of stock of the company to the general public pursuant to a registration statement filed with and declared effective by the securities and exchange commission under the securities act, the optionee hereby unconditionally and
irrevocably waives the inspection rights, whether such inspection rights would be exercised or pursued directly or indirectly pursuant to section 220 or otherwise, and covenants and agrees never to directly or indirectly commence, voluntarily aid in
any way, prosecute, assign, transfer, or cause to be commenced any claim, action, cause of action, or other proceeding to pursue or exercise the inspection rights. The foregoing waiver shall not affect any rights of a director, in his or her
capacity as such, under section 220. The foregoing waiver shall not apply to any contractual inspection rights of the optionee under any other written agreement between the optionee and the company. 

[SIGNATURE PAGE FOLLOWS] 

  
 43 

 The foregoing Agreement is hereby accepted and the terms and conditions thereof hereby
agreed to by the undersigned as of the date first above written. 
  

			
	TCR2 Therapeutics Inc.
		
	By:	 	 
		 	Name:
		 	Title:
	
	Address:
	
	  

	
	  

	
	  

 The undersigned hereby acknowledges receiving and reviewing a copy of the Plan, including, without limitation,
Section 9 thereof, and understands that this Stock Option is subject to the terms of the Plan and of this Agreement. This Agreement is hereby accepted, and the terms and conditions of the Plan, the Grant Notice and this Agreement, SPECIFICALLY
INCLUDING THE ARBITRATION PROVISIONS SET FORTH IN SECTION 7 AND THE WAIVER OF STATUTORY INFORMATION RIGHTS SET FORTH IN SECTION 8 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 

 

	
	OPTIONEE:
	
	  

	Name:
	
	Address:
	
	  

	
	  

	
	  

  
 44 

 [SPOUSE’S CONSENT2 

I acknowledge that I have read the 
 foregoing Non-Qualified Stock Option Agreement 
 and understand the contents thereof. 

____________________________________] 
  

 

	2 	 A spouse’s consent is recommended only if the Optionee’s state of residence is one of the following
community property states: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington and Wisconsin. 

  
 45 

 
	
	DESIGNATED BENEFICIARY:
	
	  

	
	Beneficiary’s Address:
	
	  

	
	  

	
	  

  
 46 

 Appendix A 

STOCK OPTION EXERCISE NOTICE 
 TCR2 Therapeutics Inc. 
 Attention: Treasurer 

 
  

 
  

Pursuant to the terms of the grant notice and stock option agreement between the undersigned and TCR2 Therapeutics Inc. (the “Company”) dated              (the “Agreement”) under the TCR2 Therapeutics Inc. 2015 Stock Option and Grant Plan, I, [Insert Name]                     ,
hereby [Circle One] partially/fully exercise such option by including herein payment in the amount of $             representing the purchase price for [Fill in number of Shares]
             Shares. I have chosen the following form(s) of payment: 
  

							
		  	[ ]	  	1.	  	Cash
		  	[ ]	  	2.	  	Certified or bank check payable to TCR2 Therapeutics Inc.
		  	[ ]	  	3.	  	Other (as referenced in the Agreement and described in the Plan (please describe)) _____________________________________________________.

 In connection with my exercise of the option as set forth above, I hereby represent and warrant to the Company
as follows: 
 (i) I am purchasing the Shares for my own account for investment only, and not for resale or with a view to the distribution
thereof. 
 (ii) I have had such an opportunity as I have deemed adequate to obtain from the Company such information as is necessary to
permit me to evaluate the merits and risks of my investment in the Company and have consulted with my own advisers with respect to my investment in the Company. 

(iii) I have sufficient experience in business, financial and investment matters to be able to evaluate the risks involved in the purchase of
the Shares and to make an informed investment decision with respect to such purchase. 
 (iv) I can afford a complete loss of the value of
the Shares and am able to bear the economic risk of holding such Shares for an indefinite period of time. 
 (v) I understand that the Shares
may not be registered under the Securities Act of 1933 (it being understood that the Shares are being issued and sold in reliance on the exemption provided in Rule 701 thereunder) or any applicable state securities or “blue sky” laws and
may not be sold or otherwise transferred or disposed of in the absence of an effective registration statement under the Securities Act of 1933 and under any applicable state securities or “blue sky” laws (or exemptions from the
registration requirement thereof). I further acknowledge that certificates representing Shares will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Shares will include similar restrictive notations. 

  
 47 

 (vi) I have read and understand the Plan and acknowledge and agree that the Shares are
subject to all of the relevant terms of the Plan, including without limitation, the transfer restrictions set forth in Section 9 of the Plan. 

(vii) I understand and agree that the Company has a right of first refusal with respect to the Shares pursuant to Section 9(b) of the
Plan. 
 (viii) I understand and agree that the Company has certain repurchase rights with respect to the Shares pursuant to
Section 9(c) of the Plan. 
 (ix) I understand and agree that I may not sell or otherwise transfer or dispose of the Shares for a period
of time following the effective date of a public offering by the Company as described in Section 9(f) of the Plan. 
 (x) I waive any
and all rights that I or my proxy may or do have under Section 220 of the General Corporation Law of Delaware (“Section 220”) to inspect, make copies of, extract from, or obtain any information in any format regarding the
Company’s or a subsidiary’s stock ledger, financial information, statements or audits, or other books and records, whether or not for a legitimate financial planning or other proper purpose. I have had sufficient opportunity to consult
with my own advisers with respect to the aforementioned waiver and understand and agree that the Company will not be obligated to provide information requested pursuant to Section 220 unless it voluntarily chooses to do so or following the
effective date of a public offering by the Company. 
 (xi) I understand and agree that, if requested by the Company at its sole discretion,
as a condition to the issuance of the Shares hereunder, I will become a party to: 
 (A) that certain Right of First Refusal
and Co-Sale Agreement between the Company and certain of its stockholders dated as of October 16, 2015, for so long as such agreement is in effect and as the same may be amended or amended and restated
from time to time (the “Right of First Refusal and Co-Sale Agreement”), and I shall thereby be bound by, and subject to, all the terms and provisions of the Right of First Refusal and Co-Sale Agreement applicable to a Key Holder thereunder, and that I will execute a counterpart signature page thereto promptly upon such request; and 

(B) that certain Voting Agreement between the Company and certain of its stockholders dated as of October 16, 2015, for so
long as such agreement is in effect and as the same may be amended or amended and restated from time to time (the “Voting Agreement”), and I shall thereby be bound by, and subject to, all the terms and provisions of the Voting Agreement
applicable to a Key Holder thereunder, and that I will execute an Adoption Agreement thereto promptly upon such request. 

  
 48 

 
	
	Sincerely yours,
	
	  

	Name:
	
	Address:
	
	  

	
	  

	
	  

	
	Date:                                     
                                       

  
 49 

 RESTRICTED STOCK AWARD NOTICE 

UNDER THE TCR2 THERAPEUTICS INC. 

2015 STOCK OPTION AND GRANT PLAN 

Pursuant to the TCR2 Therapeutics Inc. 2015 Stock Option and Grant Plan (the
“Plan”), TCR2 Therapeutics Inc., a Delaware corporation (together with any successor, the “Company”), hereby grants, sells and issues to the individual named below, the Shares
at the Per Share Purchase Price, subject to the terms and conditions set forth in this Restricted Stock Award Notice (the “Award Notice”), the attached Restricted Stock Agreement (the “Agreement”) and the Plan. The Grantee agrees
to the provisions set forth herein and acknowledges that each such provision is a material condition of the Company’s agreement to issue and sell the Shares to him or her. The Company hereby acknowledges receipt of
$[            ] in full payment for the Shares. All references to share prices and amounts herein shall be equitably adjusted to reflect stock splits, stock dividends,
recapitalizations, mergers, reorganizations and similar changes affecting the capital stock of the Company, and any shares of capital stock of the Company received on or in respect of Shares in connection with any such event (including any shares of
capital stock or any right, option or warrant to receive the same or any security convertible into or exchangeable for any such shares or received upon conversion of any such shares) shall be subject to this Agreement on the same basis and extent at
the relevant time as the Shares in respect of which they were issued, and shall be deemed Shares as if and to the same extent they were issued at the date hereof. 
  

			
	Name of Grantee:	  	_________________ (the “Grantee”)
		
	No. of Shares:	  	_________ Shares of Common Stock (the “Shares”)
		
	Grant Date:	  	____________ __, ____3
		
	Date of Purchase of Shares:	  	____________ __, ____
		
	Vesting Commencement Date:	  	____________ __, ____ (the “Vesting Commencement Date”)
		
	Per Share Purchase Price:	  	$________ (the “Per Share Purchase Price”)
		
	Vesting Schedule:	  	25 percent of the Shares shall vest on the first anniversary of the Vesting Commencement Date; provided that the Grantee continues to have a Service Relationship with the Company at such time. Thereafter, the remaining
75 percent of the Shares shall vest in 36 equal monthly installments following the first anniversary of the Vesting Commencement Date until [            ], on which date, subject to
the vesting conditions herein, all remaining Shares shall vest, provided the Grantee continues to have a Service Relationship with the Company at such time. Notwithstanding anything in the Agreement to the contrary in the case of a Sale Event, the
Shares of Restricted Stock shall be treated as provided in Section 3(c) of the Plan.

  

	3 	 83(b) Election must be made within 30 days of the date of sale or grant.

  
 50 

 Attachments: Restricted Stock Agreement, 2015 Stock Option and Grant Plan  

  
 51 

 RESTRICTED STOCK AGREEMENT 

UNDER THE TCR2 THERAPEUTICS INC. 

2015 STOCK OPTION AND GRANT PLAN 

All capitalized terms used herein and not otherwise defined shall have the respective meanings set forth in the Award Notice and the Plan.

 SECTION 1. PURCHASE AND SALE OF SHARES; VESTING; INVESTMENT REPRESENTATIONS. 

(a) Purchase and Sale. The Company hereby sells to the Grantee, and the Grantee hereby purchases from the Company, the number of Shares
set forth in the Award Notice for the Per Share Purchase Price. 
 (b) Vesting. Initially, all of the Shares are non-transferable and subject to a substantial risk of forfeiture and are Shares of Restricted Stock. The risk of forfeiture shall lapse with respect to the Shares on the respective dates indicated on the Vesting
Schedule set forth in the Award Notice. 
 (c) Investment Representations. In connection with the purchase and sale of the Shares
contemplated by Section 1(a) above, the Grantee hereby represents and warrants to the Company as follows: 
 (i) The Grantee is
purchasing the Shares for the Grantee’s own account for investment only, and not for resale or with a view to the distribution thereof. 

(ii) The Grantee has had such an opportunity as he or she has deemed adequate to obtain from the Company such information as is necessary to
permit him or her to evaluate the merits and risks of the Grantee’s investment in the Company and has consulted with the Grantee’s own advisers with respect to the Grantee’s investment in the Company. 

(iii) The Grantee has sufficient experience in business, financial and investment matters to be able to evaluate the risks involved in the
purchase of the Shares and to make an informed investment decision with respect to such purchase. 
 (iv) The Grantee can afford a complete
loss of the value of the Shares and is able to bear the economic risk of holding such Shares for an indefinite period. 
 (v) The Grantee
understands that the Shares are not registered under the Act (it being understood that the Shares are being issued and sold in reliance on the exemption provided in Rule 701 thereunder) or any applicable state securities or “blue sky” laws
and may not be sold or otherwise transferred or disposed of in the absence of an effective registration statement under the Act and under any applicable state securities or “blue sky” laws (or exemptions from the registration requirements
thereof). The Grantee further acknowledges that certificates representing the Shares will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Shares will include similar restrictive notations. 

  
 52 

 (vi) The Grantee has read and understands the Plan and acknowledges and agrees that the
Shares are subject to all of the relevant terms of the Plan, including without limitation, the transfer restrictions set forth in Section 9 of the Plan. 

(vii) The Grantee understands and agrees that the Company has a right of first refusal with respect to the Shares pursuant to Section 9(b)
of the Plan. 
 (viii) The Grantee understands and agree that the Company has certain repurchase rights with respect to the Shares pursuant
to Section 9(c) of the Plan. 
 (ix) The Grantee understands and agrees that the Grantee may not sell or otherwise transfer or dispose
of the Shares for a period of time following the effective date of a public offering by the Company as described in Section 9(f) of the Plan. 

SECTION 2. REPURCHASE RIGHT. Upon a termination event, the company shall have the right to repurchase shares of restricted stock that are unvested as
of the date of such termination event as set forth in section 9(c) of the plan. 
 SECTION 3. RESTRICTIONS ON TRANSFER OF SHARES. The shares (whether
or not vested) shall be subject to certain transfer restrictions and other limitations including, without limitation, the provisions contained in section 9 of the plan. 

SECTION 4. INCORPORATION OF PLAN. Notwithstanding anything herein to the contrary, this restricted stock award shall be subject to and governed by all
the terms and conditions of the plan. 
 SECTION 5. MISCELLANEOUS PROVISIONS. 

(a) Record Owner; Dividends. The Grantee and any Permitted Transferees, during the duration of this Agreement, shall be considered the
record owners of and shall be entitled to vote the Shares if and to the extent the Shares are entitled to voting rights. The Grantee and any Permitted Transferees shall be entitled to receive all dividends and any other distributions declared on the
Shares; provided, however, that the Company is under no duty to declare any such dividends or to make any such distribution. 

(b) Section 83(b) Election. The Grantee shall consult with the Grantee’s tax advisor to determine whether it would be appropriate
for the Grantee to make an election under Section 83(b) of the Code with respect to this Award. Any such election must be filed with the Internal Revenue Service within 30 days of the date of this Award. If the Grantee makes an election under
Section 83(b) of the Code, the Grantee shall give prompt notice to the Company (and provide a copy of such election to the Company). 

(c) Equitable Relief. The parties hereto agree and declare that legal remedies may be inadequate to enforce the provisions of this
Agreement and that equitable relief, including specific performance and injunctive relief, may be used to enforce the provisions of this Agreement. 

  
 53 

 (d) Change and Modifications. This Agreement may not be orally changed, modified or
terminated, nor shall any oral waiver of any of its terms be effective. This Agreement may be changed, modified or terminated only by an agreement in writing signed by the Company and the Grantee. 

(e) Governing Law. This Agreement shall be governed by and construed in accordance with the General Corporation Law of the State of
Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to conflict of law principles that would result
in the application of any law other than the law of the Commonwealth of Massachusetts. 
 (f) Headings. The headings are intended only
for convenience in finding the subject matter and do not constitute part of the text of this Agreement and shall not be considered in the interpretation of this Agreement. 

(g) Saving Clause. If any provision(s) of this Agreement shall be determined to be illegal or unenforceable, such determination shall in
no manner affect the legality or enforceability of any other provision hereof. 
 (h) Notices. All notices, requests, consents and
other communications shall be in writing and be deemed given when delivered personally, by telex or facsimile transmission or when received if mailed by first class registered or certified mail, postage prepaid. Notices to the Company or the Grantee
shall be addressed as set forth underneath their signatures below, or to such other address or addresses as may have been furnished by such party in writing to the other. 

(i) Benefit and Binding Effect. This Agreement shall be binding upon and shall inure to the benefit of the parties hereto, their
respective successors, assigns, and legal representatives. The Company has the right to assign this Agreement, and such assignee shall become entitled to all the rights of the Company hereunder to the extent of such assignment. 

(j) Counterparts. For the convenience of the parties and to facilitate execution, this Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which shall constitute one and the same document. 
 (k)
Integration. This Agreement constitutes the entire agreement between the parties with respect to this Award and supersedes all prior agreements and discussions between the parties concerning such subject matter. 

SECTION 6. DISPUTE RESOLUTION. 
 (a)
Except as provided below, any dispute arising out of or relating to the Plan or the Shares, this Agreement, or the breach, termination or validity of the Plan, the Shares or this Agreement, shall be finally settled by binding arbitration conducted
expeditiously in accordance with the J.A.M.S./Endispute Comprehensive Arbitration Rules and Procedures (the “J.A.M.S. Rules”). The arbitration shall be governed by the United States Arbitration Act, 9 U.S.C. Sections 1—16, and
judgment upon the award rendered by the arbitrators may be entered by any court having jurisdiction thereof. The place of arbitration shall be Boston, Massachusetts. 

  
 54 

 (b) The arbitration shall commence within 60 days of the date on which a written demand for
arbitration is filed by any party hereto. In connection with the arbitration proceeding, the arbitrator shall have the power to order the production of documents by each party and any third-party witnesses. In addition, each party may take up to
three depositions as of right, and the arbitrator may in his or her discretion allow additional depositions upon good cause shown by the moving party. However, the arbitrator shall not have the power to order the answering of interrogatories or the
response to requests for admission. In connection with any arbitration, each party to the arbitration shall provide to the other, no later than seven business days before the date of the arbitration, the identity of all persons that may testify at
the arbitration and a copy of all documents that may be introduced at the arbitration or considered or used by a party’s witness or expert. The arbitrator’s decision and award shall be made and delivered within six months of the selection
of the arbitrator. The arbitrator’s decision shall set forth a reasoned basis for any award of damages or finding of liability. The arbitrator shall not have power to award damages in excess of actual compensatory damages and shall not multiply
actual damages or award punitive damages, and each party hereby irrevocably waives any claim to such damages. 
 (c) The Company, the
Grantee, each party to the Agreement and any other holder of Shares issued pursuant to this Agreement (each, a “Party”) covenants and agrees that such party will participate in the arbitration in good faith. This Section 6 applies
equally to requests for temporary, preliminary or permanent injunctive relief, except that in the case of temporary or preliminary injunctive relief any party may proceed in court without prior arbitration for the limited purpose of avoiding
immediate and irreparable harm. 
 (d) Each Party (i) hereby irrevocably submits to the jurisdiction of any United States District Court
of competent jurisdiction for the purpose of enforcing the award or decision in any such proceeding, (ii) hereby waives, and agrees not to assert, by way of motion, as a defense, or otherwise, in any such suit, action or proceeding, any claim
that it is not subject personally to the jurisdiction of the above named courts, that its property is exempt or immune from attachment or execution (except as protected by applicable law), that the suit, action or proceeding is brought in an
inconvenient forum, that the venue of the suit, action or proceeding is improper or that this Agreement or the subject matter hereof may not be enforced in or by such court, and (iii) hereby waives and agrees not to seek any review by any court
of any other jurisdiction which may be called upon to grant an enforcement of the judgment of any such court. Each Party hereby consents to service of process by registered mail at the address to which notices are to be given. Each Party agrees that
its, his or her submission to jurisdiction and its, his or her consent to service of process by mail is made for the express benefit of each other Party. Final judgment against any Party in any such action, suit or proceeding may be enforced in
other jurisdictions by suit, action or proceeding on the judgment, or in any other manner provided by or pursuant to the laws of such other jurisdiction. 

SECTION 7. WAIVER OF STATUTORY INFORMATION RIGHTS. The grantee understands and agrees that, but for the waiver made herein, the grantee would be
entitled, upon written demand under oath stating the purpose thereof, to inspect for any proper purpose, and to make copies and extracts from, the company’s stock ledger, a list of its stockholders, and its other books and records, and the
books and records of subsidiaries of the company, if any, under the circumstances and in the manner provided in section 220 of the general corporation law of 

  
 55 

 
delaware (any and all such rights, and any and all such other rights of the grantee as may be provided for in section 220, the “inspection rights”). In light of the foregoing, until the
first sale of stock of the company to the general public pursuant to a registration statement filed with and declared effective by the securities and exchange commission under the securities act, the grantee hereby unconditionally and irrevocably
waives the inspection rights, whether such inspection rights would be exercised or pursued directly or indirectly pursuant to section 220 or otherwise, and covenants and agrees never to directly or indirectly commence, voluntarily aid in any way,
prosecute, assign, transfer, or cause to be commenced any claim, action, cause of action, or other proceeding to pursue or exercise the inspection rights. The foregoing waiver shall not affect any rights of a director, in his or her capacity as
such, under section 220. The foregoing waiver shall not apply to any contractual inspection rights of the grantee under any other written agreement between the grantee and the company. 

[SIGNATURE PAGE FOLLOWS] 

  
 56 

 The foregoing Restricted Stock Agreement is hereby accepted and the terms and conditions
thereof are hereby agreed to by the undersigned as of the date of purchase of Shares above written. 
  

			
	TCR2 Therapeutics Inc.
		
	By:	 	 
		 	Name:
		 	Title:
	
	Address:
	
	  

	
	  

	
	  

 The undersigned hereby acknowledges receiving and reviewing a copy of the Plan, including, without limitation,
Section 9 thereof and understands that the Shares granted hereby are subject to the terms of the Plan and of this Agreement. This Agreement is hereby accepted, and the terms and conditions of the Plan, the Award Notice and this Agreement,
SPECIFICALLY INCLUDING THE ARBITRATION PROVISIONS SET FORTH IN SECTION 6 AND THE WAIVER OF STATUTORY INFORMATION RIGHTS SET FORTH IN SECTION 7 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 

 

	
	GRANTEE:
	
	  

	Name:
	
	Address:
	
	  

	
	  

	
	  

  
 57 

 [SPOUSE’S CONSENT4 

I acknowledge that I have read the 
 foregoing Restricted Stock
Agreement 
 and understand the contents thereof. 

____________________________________] 
  

 

	4 	 A spouse’s consent is required only if the Grantee’s state of residence is one of the following
community property states: Arizona, California, Idaho, Louisiana, New Mexico, Nevada, Texas, Washington and Wisconsin. 

  
 58

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