Document:

EX-10.1

 Exhibit 10.1 
 AMENDMENT TO THE GENETIX PHARMACEUTICALS INC. 
 2002 EMPLOYEE, DIRECTOR
AND CONSULTANT STOCK PLAN 
 This Amendment to the Genetix Pharmaceuticals Inc. 2002 Employee, Director and Consultant Stock
Plan, attached hereto as Exhibit A, (the “Plan”) is effective as of March 5, 2010. 
 1. Section 3(a) of the
Plan is hereby amended by deleting the first sentence thereof and replacing such sentence with the following: 
 “The number of Shares which
may be issued from time to time pursuant to this Plan shall be 33,520,333, or the equivalent of such number of Shares after the Administrator, in its sole discretion, has interpreted the effect of any stock split, stock dividend, combination,
recapitalization or similar transaction in accordance with Paragraph 23 of the Plan.” 
 2. Section 3(b) of the Plan
is hereby deleted and replaced in its entirety with the following: 
 “If an Option ceases to be “outstanding”, in whole or in
part (other than by exercise), or if the Company shall reacquire (at not more than its original issuance price) any Shares issued pursuant to a Stock Grant or Stock-Based Award, or if any Stock Right expires or is forfeited, cancelled, or otherwise
terminated or results in any Shares not being issued, the unissued or reacquired Shares which were subject to such Stock Right shall again be available for issuance from time to time pursuant to this Plan.” 

3. Except as expressly amended hereby, the Plan shall remain in full force and effect. 

IN WITNESS WHEREOF, the President and Chief Executive Officer of the Company has duly executed this Amendment to be effective as the date
first above written. 
  

			
	GENETIX PHARMACEUTICALS INC.
		
	By:	 	/s/ Alfred Slanetz
		 	 Alfred Slanetz
 President
and Chief Executive Officer

 Exhibit A 
 GENETIX PHARMACEUTICALS INC. 
 2002 EMPLOYEE, DIRECTOR AND CONSULTANT
STOCK PLAN 

  
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 As adopted by the Board of Directors on April 19, 2002 

As approved by the shareholders on April 19, 2002 
 As amended by the Board of Directors on May 11, 2004 
 As approved by the
shareholders on May 11, 2004 
 As amended by the Board of Directors on June 2, 2004 

As approved by the shareholders on June 2, 2004 
 GENETIX PHARMACEUTICALS INC. 
 SECOND AMENDED AND RESTATED 

2002 EMPLOYEE, DIRECTOR AND CONSULTANT STOCK PLAN 
  

	1.	DEFINITIONS. 

 Unless
otherwise specified or unless the context otherwise requires, the following terms, as used in this Genetix Pharmaceuticals Inc. 2002 Employee, Director and Consultant Stock Plan, have the following meanings: 

Administrator means the Board of Directors, unless it has delegated power to act on its behalf to the Committee, in which case the
Administrator means the Committee. 
 Affiliate means a corporation which, for purposes of Section 424 of the Code,
is a parent or subsidiary of the Company, direct or indirect. 
 Board of Directors means the Board of Directors of the
Company. 
 Code means the United States Internal Revenue Code of 1986, as amended. 

Committee means the committee of the Board of Directors to which the Board of Directors has delegated power to act under or
pursuant to the provisions of the Plan. 
 Common Stock means shares of the Company’s common stock, $.001 par value
per share. 
 Company means Genetix Pharmaceuticals Inc., a Delaware corporation. 

Disability or Disabled means permanent and total disability as defined in Section 22(e)(3) of the Code. 

Employee means any employee of the Company or of an Affiliate (including, without limitation, an employee who is also serving as an
officer or director of the Company or of an Affiliate), designated by the Administrator to be eligible to be granted one or more Stock Rights under the Plan. 

  
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 Fair Market Value of a Share of Common Stock means: 

(1) If the Common Stock is listed on a national securities exchange or traded in the over-the-counter market and sales prices are
regularly reported for the Common Stock, the closing or last price of the Common Stock on the Composite Tape or other comparable reporting system for the trading day immediately preceding the applicable date; 

(2) If the Common Stock is not traded on a national securities exchange but is traded on the over-the-counter market, if sales prices are
not regularly reported for the Common Stock for the trading day referred to in clause (1), and if bid and asked prices for the Common Stock are regularly reported, the mean between the bid and the asked price for the Common Stock at the close of
trading in the over-the-counter market for the trading day on which Common Stock was traded immediately preceding the applicable date; and 
 (3) If the Common Stock is neither listed on a national securities exchange nor traded in the over-the-counter market, such value as the Administrator, in good faith, shall determine. 

ISO means an option meant to qualify as an incentive stock option under Section 422 of the Code. 

Non-Qualified Option means an option which is not intended to qualify as an ISO. 

Option means an ISO or Non-Qualified Option granted under the Plan. 

Option Agreement means an agreement between the Company and a Participant delivered pursuant to the Plan, in such form as the
Administrator shall approve. 
 Participant means an Employee, director or consultant of the Company or an Affiliate to
whom one or more Stock Rights are granted under the Plan. As used herein, “Participant” shall include “Participant’s Survivors” where the context requires. 

Plan means this Genetix Pharmaceuticals Inc. 2002 Employee, Director and Consultant Stock Plan. 

Shares means shares of the Common Stock as to which Stock Rights have been or may be granted under the Plan or any shares of
capital stock into which the Shares are changed or for which they are exchanged within the provisions of Paragraph 3 of the Plan. The Shares issued under the Plan may be authorized and unissued shares or shares held by the Company in its treasury,
or both. 
 Stock Grant means a grant by the Company of Shares under the Plan. 

  
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 Stock Grant Agreement means an agreement between the Company and a Participant
delivered pursuant to the Plan, in such form as the Administrator shall approve. 
 Stock Right means a right to Shares of
the Company granted pursuant to the Plan — an ISO, a Non-Qualified Option or a Stock Grant. 
 Survivor means a
deceased Participant’s legal representatives and/or any person or persons who acquired the Participant’s rights to a Stock Right by will or by the laws of descent and distribution. 

 

	2.	PURPOSES OF THE PLAN. 

The Plan is intended to encourage ownership of Shares by Employees and directors of and certain consultants to the Company in order to
attract such people, to induce them to work for the benefit of the Company or of an Affiliate and to provide additional incentive for them to promote the success of the Company or of an Affiliate. The Plan provides for the granting of ISOs,
Non-Qualified Options and Stock Grants. 
  

	3.	SHARES SUBJECT TO THE PLAN. 

 (a) The number of Shares which may be issued from time to time pursuant to this Plan shall be 4,446,834, or the equivalent of such number of Shares after the Administrator, in its sole discretion, has
interpreted the effect of any stock split, stock dividend, combination, recapitalization or similar transaction in accordance with Paragraph 23 of the Plan. 
 (b) If an Option ceases to be “outstanding”, in whole or in part, or if the Company shall reacquire any Shares issued pursuant to a Stock Grant, the Shares which were subject to such Option and
any Shares so reacquired by the Company shall be available for the granting of other Stock Rights under the Plan. Any Option shall be treated as “outstanding” until such Option is exercised in full, or terminates or expires under the
provisions of the Plan, or by agreement of the parties to the pertinent Option Agreement. 
  

	4.	ADMINISTRATION OF THE PLAN. 

 The Administrator of the Plan will be the Board of Directors, except to the extent the Board of Directors delegates its authority to the Committee, in which case the Committee shall be the Administrator.
Subject to the provisions of the Plan, the Administrator is authorized to: 
  

	 	a.	Interpret the provisions of the Plan or of any Option or Stock Grant and to make all rules and determinations which it deems necessary or advisable for the
administration of the Plan; 

  

	 	b.	Determine which Employees, directors and consultants shall be granted Stock Rights; 

 

	 	c.	Determine the number of Shares for which a Stock Right or Stock Rights shall be granted; 

  
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	 	d.	Specify the terms and conditions upon which a Stock Right or Stock Rights may be granted; and 

 

	 	e.	Adopt any sub-plans applicable to residents of any specified jurisdiction as it deems necessary or appropriate in order to comply with or take advantage of any tax laws
applicable to the Company or to Plan Participants or to otherwise facilitate the administration of the Plan, which sub-plans may include additional restrictions or conditions applicable to Options or Shares acquired upon exercise of Options.

 provided, however, that all such interpretations, rules, determinations, terms and conditions shall be made and prescribed in
the context of preserving the tax status under Section 422 of the Code of those Options which are designated as ISOs. Subject to the foregoing, the interpretation and construction by the Administrator of any provisions of the Plan or of any
Stock Right granted under it shall be final, unless otherwise determined by the Board of Directors, if the Administrator is the Committee. In addition, if the Administrator is the Committee, the Board of Directors may take any action under the Plan
that would otherwise be the responsibility of the Committee. 
 If permissible under applicable law, the Board of Directors or
the Committee may allocate all or any portion of its responsibilities and powers to any one or more of its members and may delegate all or any portion of its responsibilities and powers to any other person selected by it. Any such allocation or
delegation may be revoked by the Board of Directors or the Committee at any time. 
  

	5.	ELIGIBILITY FOR PARTICIPATION. 

 The Administrator will, in its sole discretion, name the Participants in the Plan, provided, however, that each Participant must be an Employee, director or consultant of the Company or of an Affiliate at
the time a Stock Right is granted. Notwithstanding the foregoing, the Administrator may authorize the grant of a Stock Right to a person not then an Employee, director or consultant of the Company or of an Affiliate; provided, however, that the
actual grant of such Stock Right shall be conditioned upon such person becoming eligible to become a Participant at or prior to the time of the execution of the Agreement evidencing such Stock Right. ISOs may be granted only to Employees.
Non-Qualified Options and Stock Grants may be granted to any Employee, director or consultant of the Company or an Affiliate. The granting of any Stock Right to any individual shall neither entitle that individual to, nor disqualify him or her from,
participation in any other grant of Stock Rights. 
  

	6.	TERMS AND CONDITIONS OF OPTIONS. 

 Each Option shall be set forth in writing in an Option Agreement, duly executed by the Company and, to the extent required by law or requested by the Company, by the Participant. The Administrator may
provide that Options be granted subject to such terms and conditions, consistent with the terms and conditions specifically required under this Plan, as the Administrator may deem appropriate including, without limitation, subsequent approval by the
shareholders of the Company of this Plan or any amendments thereto. The Option Agreements, which may differ among recipients, shall be subject to at least the following terms and conditions: 

  
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	 	A.	Non-Qualified Options: Each Option intended to be a Non-Qualified Option shall be subject to the terms and conditions which the Administrator determines to be
appropriate and in the best interest of the Company, subject to the following minimum standards for any such Non-Qualified Option: 

  

	 	a.	Option Price: Each Option Agreement shall state the option price (per share) of the Shares covered by each Option, which option price shall be determined by the
Administrator but shall not be less than the par value per share of Common Stock; 

  

	 	b.	Each Option Agreement shall state the number of Shares to which it pertains; 

 

	 	c.	Each Option Agreement shall state the date or dates on which it first is exercisable and the date after which it may no longer be exercised, and may provide that the
Option rights accrue or become exercisable in installments over a period of months or years, or upon the occurrence of certain conditions or the attainment of stated goals or events; and 

 

	 	d.	Exercise of any Option may be conditioned upon the Participant’s execution of a Share purchase agreement in form satisfactory to the Administrator providing for
certain protections for the Company and its other shareholders, including requirements that: 

  

	 	i.	The Participant’s or the Participant’s Survivors’ right to sell or transfer the Shares may be restricted; and 

 

	 	ii.	The Participant or the Participant’s Survivors may be required to execute letters of investment intent and must also acknowledge that the Shares will bear legends
noting any applicable restrictions. 

  

	 	B.	ISOs: Each Option intended to be an ISO shall be issued only to an Employee and be subject to the following terms and conditions, with such additional
restrictions or changes as the Administrator determines are appropriate but not in conflict with Section 422 of the Code and relevant regulations and rulings of the Internal Revenue Service: 

 

	 	a.	Minimum standards: The ISO shall meet the minimum standards required of Non-Qualified Options, as described in Paragraph 6(A) above, except clause (a) thereunder.

  
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	 	b.	Option Price: Immediately before the ISO is granted, if the Participant owns, directly or by reason of the applicable attribution rules in Section 424(d) of the
Code: 

  

	 	i.	10% or less of the total combined voting power of all classes of stock of the Company or an Affiliate, the Option price per share of the Shares covered by each
ISO shall not be less than 100% of the Fair Market Value per share of the Shares on the date of the grant of the Option; or 

  

	 	ii.	More than 10% of the total combined voting power of all classes of stock of the Company or an Affiliate, the Option price per share of the Shares covered by each ISO
shall not be less than 110% of the said Fair Market Value on the date of grant. 

  

	 	c.	Term of Option: For Participants who own: 

  

	 	i.	10% or less of the total combined voting power of all classes of stock of the Company or an Affiliate, each ISO shall terminate not more than ten years from the
date of the grant or at such earlier time as the Option Agreement may provide; or 

  

	 	ii.	More than 10% of the total combined voting power of all classes of stock of the Company or an Affiliate, each ISO shall terminate not more than five years from the date
of the grant or at such earlier time as the Option Agreement may provide. 

  

	 	d.	Limitation on Yearly Exercise: The Option Agreements shall restrict the amount of ISOs which may become exercisable in any calendar year (under this or any other ISO
plan of the Company or an Affiliate) so that the aggregate Fair Market Value (determined at the time each ISO is granted) of the stock with respect to which ISOs are exercisable for the first time by the Participant in any calendar year does not
exceed $100,000. 

  

	7.	TERMS AND CONDITIONS OF STOCK GRANTS. 

 Each offer of a Stock Grant to a Participant shall state the date prior to which the Stock Grant must be accepted by the Participant, and the principal terms of each Stock Grant shall be set forth in a
Stock Grant Agreement, duly executed by the Company and, to the extent required by law or requested by the Company, by the Participant. The Stock Grant Agreement shall be in a form approved by the Administrator and shall contain terms and conditions
which the Administrator determines to be appropriate and in the best interest of the Company, subject to the following minimum standards: 
  

	 	(a)	Each Stock Grant Agreement shall state the purchase price (per share), if any, of the Shares covered by each Stock Grant, which purchase price shall be determined by
the Administrator but shall not be less than the minimum consideration required by the Delaware General Corporation Law on the date of the grant of the Stock Grant; 

  
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	 	(b)	Each Stock Grant Agreement shall state the number of Shares to which the Stock Grant pertains; and 

 

	 	(c)	Each Stock Grant Agreement shall include the terms of any right of the Company to restrict or reacquire the Shares subject to the Stock Grant, including the time and
events upon which such reacquisition rights shall accrue and the purchase price therefor, if any. 

  

	8.	EXERCISE OF OPTIONS AND ISSUE OF SHARES. 

 An Option (or any part or installment thereof) shall be exercised by giving written notice to the Company or its designee, together with provision for payment of the full purchase price in accordance with
this Paragraph for the Shares as to which the Option is being exercised, and upon compliance with any other condition(s) set forth in the Option Agreement. Such notice shall be signed by the person exercising the Option, shall state the number of
Shares with respect to which the Option is being exercised and shall contain any representation required by the Plan or the Option Agreement. Payment of the purchase price for the Shares as to which such Option is being exercised shall be made
(a) in United States dollars in cash or by check, or (b) at the discretion of the Administrator, through delivery of shares of Common Stock having a Fair Market Value equal as of the date of the exercise to the cash exercise price of the
Option and held for at least six months, or (c) at the discretion of the Administrator, by delivery of the grantee’s personal note, for full, partial or no recourse, bearing interest payable not less than annually at market rate on the
date of exercise and at no less than 100% of the applicable Federal rate, as defined in Section 1274(d) of the Code, with or without the pledge of such Shares as collateral, or (d) at the discretion of the Administrator, in accordance with
a cashless exercise program established with a securities brokerage firm, and approved by the Administrator, or (e) at the discretion of the Administrator, by any combination of (a), (b), (c) and (d) above. Notwithstanding the
foregoing, the Administrator shall accept only such payment on exercise of an ISO as is permitted by Section 422 of the Code. 
 The Company shall then reasonably promptly deliver the Shares as to which such Option was exercised to the Participant (or to the Participant’s Survivors, as the case may be). In determining what
constitutes “reasonably promptly,” it is expressly understood that the issuance and delivery of the Shares may be delayed by the Company in order to comply with any law or regulation (including, without limitation, state securities or
“blue sky” laws) which requires the Company to take any action with respect to the Shares prior to their issuance. The Shares shall, upon delivery, be fully paid, non-assessable Shares. 

The Administrator shall have the right to accelerate the date of exercise of any installment of any Option; provided that the
Administrator shall not accelerate the exercise date of any installment of any Option granted to an Employee as an ISO (and not previously converted into a Non-Qualified Option pursuant to Paragraph 26) if such acceleration would violate the annual
vesting limitation contained in Section 422(d) of the Code, as described in Paragraph 6.B.d. 

  
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 The Administrator may, in its discretion, amend any term or condition of an outstanding
Option provided (i) such term or condition as amended is permitted by the Plan, (ii) any such amendment shall be made only with the consent of the Participant to whom the Option was granted, or in the event of the death of the Participant,
the Participant’s Survivors, if the amendment is adverse to the Participant, and (iii) any such amendment of any ISO shall be made only after the Administrator determines whether such amendment would constitute a “modification”
of any Option which is an ISO (as that term is defined in Section 424(h) of the Code) or would cause any adverse tax consequences for the holder of such ISO. 
  

	9.	ACCEPTANCE OF STOCK GRANT AND ISSUE OF SHARES. 

 A Stock Grant (or any part or installment thereof) shall be accepted by executing the Stock Grant Agreement and delivering it to the Company or its designee, together with provision for payment of the
full purchase price, if any, in accordance with this Paragraph for the Shares as to which such Stock Grant is being accepted, and upon compliance with any other conditions set forth in the Stock Grant Agreement. Payment of the purchase price for the
Shares as to which such Stock Grant is being accepted shall be made (a) in United States dollars in cash or by check, or (b) at the discretion of the Administrator, through delivery of shares of Common Stock held for at least six months
and having a Fair Market Value equal as of the date of acceptance of the Stock Grant to the purchase price of the Stock Grant, or (c) at the discretion of the Administrator, by delivery of the grantee’s personal note, for full or partial
recourse as determined by the Administrator, bearing interest payable not less than annually at no less than 100% of the applicable Federal rate, as defined in Section 1274(d) of the Code, or (d) at the discretion of the Administrator, by
any combination of (a), (b) and (c) above. 
 The Company shall then reasonably promptly deliver the Shares as to
which such Stock Grant was accepted to the Participant (or to the Participant’s Survivors, as the case may be), subject to any escrow provision set forth in the Stock Grant Agreement. In determining what constitutes “reasonably
promptly,” it is expressly understood that the issuance and delivery of the Shares may be delayed by the Company in order to comply with any law or regulation (including, without limitation, state securities or “blue sky” laws) which
requires the Company to take any action with respect to the Shares prior to their issuance. 
 The Administrator may, in its
discretion, amend any term or condition of an outstanding Stock Grant or Stock Grant Agreement provided (i) such term or condition as amended is permitted by the Plan, and (ii) any such amendment shall be made only with the consent of the
Participant to whom the Stock Grant was made, if the amendment is adverse to the Participant. 
  

	10.	RIGHTS AS A SHAREHOLDER. 

No Participant to whom a Stock Right has been granted shall have rights as a shareholder with respect to any Shares covered by such Stock
Right, except after due exercise of the Option or acceptance of the Stock Grant and tender of the full purchase price, if any, for the Shares being purchased pursuant to such exercise or acceptance and registration of the Shares in the
Company’s share register in the name of the Participant. 

  
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	11.	ASSIGNABILITY AND TRANSFERABILITY OF STOCK RIGHTS. 

 By its terms, a Stock Right granted to a Participant shall not be transferable by the Participant other than (i) by will or by the laws of descent and distribution, or (ii) as approved by the
Administrator in its discretion and set forth in the applicable Option Agreement or Stock Grant Agreement. Notwithstanding the foregoing, an ISO transferred except in compliance with clause (i) above shall no longer qualify as an ISO. The
designation of a beneficiary of a Stock Right by a Participant, with the prior approval of the Administrator and in such form as the Administrator shall prescribe, shall not be deemed a transfer prohibited by this Paragraph. Except as provided
above, a Stock Right shall only be exercisable or may only be accepted, during the Participant’s lifetime, only by such Participant (or by his or her legal representative) and shall not be assigned, pledged or hypothecated in any way (whether
by operation of law or otherwise) and shall not be subject to execution, attachment or similar process. Any attempted transfer, assignment, pledge, hypothecation or other disposition of any Stock Right or of any rights granted thereunder contrary to
the provisions of this Plan, or the levy of any attachment or similar process upon a Stock Right, shall be null and void. 
  

	12.	EFFECT ON OPTIONS OF TERMINATION OF SERVICE OTHER THAN “FOR CAUSE” OR DEATH OR DISABILITY. 

Except as otherwise provided in a Participant’s Option Agreement, in the event of a termination of service (whether as an employee,
director or consultant) with the Company or an Affiliate before the Participant has exercised an Option, the following rules apply: 
  

	 	a.	A Participant who ceases to be an employee, director or consultant of the Company or of an Affiliate (for any reason other than termination “for cause”.
Disability, or death for which events there are special rules in Paragraphs 13, 14, and 15, respectively), may exercise any Option granted to him or her to the extent that the Option is exercisable on the date of such termination of service, but
only within such term as the Administrator has designated in a Participant’s Option Agreement. 

  

	 	b.	Except as provided in Subparagraph (c) below, or Paragraph 14 or 15, in no event may an Option intended to be an ISO, be exercised later than three months after
the Participant’s termination of employment. 

  

	 	c.	The provisions of this Paragraph, and not the provisions of Paragraph 14 or 15, shall apply to a Participant who subsequently becomes Disabled or dies after the
termination of employment, director status or consultancy, provided, however, in the case of a Participant’s Disability or death within three months after the termination of employment, director status or consultancy, the Participant or the
Participant’s Survivors may exercise the Option within one year after the date of the Participant’s termination of service, but in no event after the date of expiration of the term of the Option. 

 

	 	d.	Notwithstanding anything herein to the contrary, if subsequent to a Participant’s termination of employment, termination of director status or termination of
consultancy, but prior to the exercise of an Option, the Board of Directors determines that, either prior or subsequent to the Participant’s termination, the Participant engaged in conduct which would constitute “cause”, then such
Participant shall forthwith cease to have any right to exercise any Option. 

  
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	 	e.	A Participant to whom an Option has been granted under the Plan who is absent from work with the Company or with an Affiliate because of temporary disability (any
disability other than a permanent and total Disability as defined in Paragraph 1 hereof), or who is on leave of absence for any purpose, shall not, during the period of any such absence, be deemed, by virtue of such absence alone, to have terminated
such Participant’s employment, director status or consultancy with the Company or with an Affiliate, except as the Administrator may otherwise expressly provide. 

 

	 	f.	Except as required by law or as set forth in a Participant’s Option Agreement, Options granted under the Plan shall not be affected by any change of a
Participant’s status within or among the Company and any Affiliates, so long as the Participant continues to be an employee, director or consultant of the Company or any Affiliate. 

 

	13.	EFFECT ON OPTIONS OF TERMINATION OF SERVICE “FOR CAUSE”. 

 Except as otherwise provided in a Participant’s Option Agreement, the following rules apply if the Participant’s service (whether as an employee, director or consultant) with the Company or an
Affiliate is terminated “for cause” prior to the time that all his or her outstanding Options have been exercised: 
  

	 	a.	All outstanding and unexercised Options as of the time the Participant is notified his or her service is terminated “for cause” will immediately be forfeited.

  

	 	b.	For purposes of this Plan, “cause” shall include (and is not limited to) dishonesty with respect to the Company or any Affiliate, insubordination, substantial
malfeasance or non-feasance of duty, unauthorized disclosure of confidential information, breach by the Participant of any provision of any employment, consulting, advisory, nondisclosure, non-competition or similar agreement between the Participant
and the Company, and conduct substantially prejudicial to the business of the Company or any Affiliate. The determination of the Administrator as to the existence of “cause” will be conclusive on the Participant and the Company.

  

	 	c.	“Cause” is not limited to events which have occurred prior to a Participant’s termination of service, nor is it necessary that the Administrator’s
finding of “cause” occur prior to termination. If the Administrator determines, subsequent to a Participant’s termination of service but prior to the exercise of an Option, that either prior or subsequent to the Participant’s
termination the Participant engaged in conduct which would constitute “cause”, then the right to exercise any Option is forfeited. 

  

	 	d.	Any definition in an agreement between the Participant and the Company or an Affiliate, which contains a conflicting definition of “cause” for termination and
which is in effect at the time of such termination, shall supersede the definition in this Plan with respect to that Participant. 

  
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	14.	EFFECT ON OPTIONS OF TERMINATION OF SERVICE FOR DISABILITY. 

 Except as otherwise provided in a Participant’s Option Agreement, a Participant who ceases to be an employee, director or consultant of the Company or of an Affiliate by reason of Disability may
exercise any Option granted to such Participant: 
  

	 	a.	To the extent that the Option has become exercisable but has not been exercised on the date of Disability; and 

 

	 	b.	In the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of Disability of any additional vesting rights that
would have accrued on the next vesting date had the Participant not become Disabled. The proration shall be based upon the number of days accrued in the current vesting period prior to the date of Disability. 

A Disabled Participant may exercise such rights only within the period ending one year after the date of the Participant’s
termination of employment, directorship or consultancy, as the case may be, notwithstanding that the Participant might have been able to exercise the Option as to some or all of the Shares on a later date if the Participant had not become Disabled
and had continued to be an employee, director or consultant or, if earlier, within the originally prescribed term of the Option. 
 The Administrator shall make the determination both of whether Disability has occurred and the date of its occurrence (unless a procedure for such determination is set forth in another agreement between
the Company and such Participant, in which case such procedure shall be used for such determination). If requested, the Participant shall be examined by a physician selected or approved by the Administrator, the cost of which examination shall be
paid for by the Company. 
  

	15.	EFFECT ON OPTIONS OF DEATH WHILE AN EMPLOYEE, DIRECTOR OR CONSULTANT. 

 Except as otherwise provided in a Participant’s Option Agreement, in the event of the death of a Participant while the Participant is an employee, director or consultant of the Company or of an
Affiliate, such Option may be exercised by the Participant’s Survivors: 
  

	 	a.	To the extent that the Option has become exercisable but has not been exercised on the date of death; and 

 

	 	b.	In the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of death of any additional vesting rights that
would have accrued on the next vesting date had the Participant not died. The proration shall be based upon the number of days accrued in the current vesting period prior to the Participant’s date of death. 

If the Participant’s Survivors wish to exercise the Option, they must take all necessary steps to exercise the Option within one
year after the date of death of such Participant, notwithstanding that the decedent might have been able to exercise the Option as to some or all of the Shares on a later date if he or she had not died and had continued to be an employee, director
or consultant or, if earlier, within the originally prescribed term of the Option. 

  
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	16.	EFFECT OF TERMINATION OF SERVICE ON STOCK GRANTS. 

 In the event of a termination of service (whether as an employee, director or consultant) with the Company or an Affiliate for any reason before the Participant has accepted a Stock Grant, such offer
shall terminate. 
 For purposes of this Paragraph 16 and Paragraph 17 below, a Participant to whom a Stock Grant has been
offered and accepted under the Plan who is absent from work with the Company or with an Affiliate because of temporary disability (any disability other than a permanent and total Disability as defined in Paragraph 1 hereof), or who is on leave of
absence for any purpose, shall not, during the period of any such absence, be deemed, by virtue of such absence alone, to have terminated such Participant’s employment, director status or consultancy with the Company or with an Affiliate,
except as the Administrator may otherwise expressly provide. 
 In addition, for purposes of this Paragraph 16 and Paragraph 17
below, any change of employment or other service within or among the Company and any Affiliates shall not be treated as a termination of employment, director status or consultancy so long as the Participant continues to be an employee, director or
consultant of the Company or any Affiliate. 
  

	17.	EFFECT ON STOCK GRANTS OF TERMINATION OF SERVICE OTHER THAN “FOR CAUSE” OR DEATH OR DISABILITY. 

Except as otherwise provided in a Participant’s Stock Grant Agreement, in the event of a termination of service (whether as an
employee, director or consultant), other than termination “for cause,” Disability, or death for which events there are special rules in Paragraphs 18, 19, and 20, respectively, before all Company rights of repurchase shall have lapsed,
then the Company shall have the right to repurchase that number of Shares subject to a Stock Grant as to which the Company’s repurchase rights have not lapsed. 
  

	18.	EFFECT ON STOCK GRANTS OF TERMINATION OF SERVICE “FOR CAUSE”. 

 Except as otherwise provided in a Participant’s Stock Grant Agreement, the following rules apply if the Participant’s service (whether as an employee, director or consultant) with the Company or
an Affiliate is terminated “for cause”: 
  

	 	a.	AH Shares subject to any Stock Grant shall be immediately subject to repurchase by the Company at the purchase price, if any, thereof. 

 

	 	b.	For purposes of this Plan, “cause” shall include (and is not limited to) dishonesty with respect to the employer, insubordination, substantial malfeasance or
non-feasance of duty, unauthorized disclosure of confidential information, breach by the Participant of any provision of any employment, consulting, advisory, nondisclosure, non-competition or similar agreement between the Participant and the
Company, and conduct substantially prejudicial to the business of the Company or any Affiliate. The determination of the Administrator as to the existence of “cause” will be conclusive on the Participant and the Company.

  
 14 

	 	c.	“Cause” is not limited to events which have occurred prior to a Participant’s termination of service, nor is it necessary that the Administrator’s
finding of “cause” occur prior to termination. If the Administrator determines, subsequent to a Participant’s termination of service, that either prior or subsequent to the Participant’s termination the Participant engaged in
conduct which would constitute “cause,” then the Company’s right to repurchase all of such Participant’s Shares shall apply. 

  

	 	d.	Any definition in an agreement between the Participant and the Company or an Affiliate, which contains a conflicting definition of “cause” for termination and
which is in effect at the time of such termination, shall supersede the definition in this Plan with respect to that Participant. 

  

	19.	EFFECT ON STOCK GRANTS OF TERMINATION OF SERVICE FOR DISABILITY. 

 Except as otherwise provided in a Participant’s Stock Grant Agreement, the following rules apply if a Participant ceases to be an employee, director or consultant of the Company or of an Affiliate by
reason of Disability: to the extent the Company’s rights of repurchase have not lapsed on the date of Disability, they shall be exercisable; provided, however, that in the event such rights of repurchase lapse periodically, such rights shall
lapse to the extent of a pro rata portion of the Shares subject to such Stock Grant through the date of Disability as would have lapsed had the Participant not become Disabled. The proration shall be based upon the number of days accrued prior to
the date of Disability. 
 The Administrator shall make the determination both of whether Disability has occurred and the date
of its occurrence (unless a procedure for such determination is set forth in another agreement between the Company and such Participant, in which case such procedure shall be used for such determination). If requested, the Participant shall be
examined by a physician selected or approved by the Administrator, the cost of which examination shall be paid for by the Company. 
  

	20.	EFFECT ON STOCK GRANTS OF DEATH WHILE AN EMPLOYEE, DIRECTOR OR CONSULTANT. 

 Except as otherwise provided in a Participant’s Stock Grant Agreement, the following rules apply in the event of the death of a Participant while the Participant is an employee, director or
consultant of the Company or of an Affiliate: to the extent the Company’s rights of repurchase have not lapsed on the date of death, they shall be exercisable; provided, however, that in the event such rights of repurchase lapse periodically,
such rights shall lapse to the extent of a pro rata portion of the Shares subject to such Stock Grant through the date of death as would have lapsed had the Participant not died. The proration shall be based upon the number of days accrued prior to
the Participant’s death. 

  
 15 

	21.	PURCHASE FOR INVESTMENT. 

Unless the offering and sale of the Shares to be issued upon the particular exercise or acceptance of a Stock Right shall have been
effectively registered under the Securities Act of 1933, as now in force or hereafter amended (the “1933 Act”), the Company shall be under no obligation to issue the Shares covered by such exercise unless and until the following conditions
have been fulfilled: 
  

	 	a.	The person(s) who exercise(s) or accept(s) such Stock Right shall warrant to the Company, prior to the receipt of such Shares, that such person(s) are acquiring such
Shares for their own respective accounts, for investment, and not with a view to, or for sale in connection with, the distribution of any such Shares, in which event the person(s) acquiring such Shares shall be bound by the provisions of the
following legend which shall be endorsed upon the certificate(s) evidencing their Shares issued pursuant to such exercise or such grant: 

 “The shares represented by this certificate have been taken for investment and they may not be sold or otherwise transferred by any person, including a pledgee, unless (1) either (a) a
Registration Statement with respect to such shares shall be effective under the Securities Act of 1933, as amended, or (b) the Company shall have received an opinion of counsel satisfactory to it that an exemption from registration under such
Act is then available, and (2) there shall have been compliance with all applicable state securities laws.” 
  

	 	b.	At the discretion of the Administrator, the Company shall have received an opinion of its counsel that the Shares may be issued upon such particular exercise or
acceptance in compliance with the 1933 Act without registration thereunder. 

  

	22.	DISSOLUTION OR LIQUIDATION OF THE COMPANY. 

 Upon the dissolution or liquidation of the Company, all Options granted under this Plan which as of such date shall not have been exercised and all Stock Grants which have not been accepted will terminate
and become null and void; provided, however, that if the rights of a Participant or a Participant’s Survivors have not otherwise terminated and expired, the Participant or the Participant’s Survivors will have the right immediately prior
to such dissolution or liquidation to exercise or accept any Stock Right to the extent that the Stock Right is exercisable or subject to acceptance as of the date immediately prior to such dissolution or liquidation. 

 

	23.	ADJUSTMENTS. 

 Upon the
occurrence of any of the following events, a Participant’s rights with respect to any Stock Right granted to him or her hereunder shall be adjusted as hereinafter provided, unless otherwise specifically provided in a Participant’s Option
Agreement or Stock Grant Agreement: 
  

	 	A.	 Stock Dividends and Stock Splits. If (i) the shares of Common Stock shall be subdivided or combined into a greater or smaller number of
shares or if the Company shall issue any shares of Common Stock as a stock dividend on its 

  
 16 

	 	
outstanding Common Stock, or (ii) 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 of
Common Stock, the number of shares of Common Stock deliverable upon the exercise or acceptance of such Stock Right may be appropriately increased or decreased proportionately, and appropriate adjustments may be made including, in the purchase price
per share, to reflect such events. 

  

	 	B.	Corporate Transactions. If the Company is to be consolidated with or acquired by another entity in a merger, sale of all or substantially all of the
Company’s assets other than a transaction to merely change the state of incorporation (a “Corporate Transaction”), the Administrator or the board of directors of any entity assuming the obligations of the Company hereunder (the
“Successor Board”), shall, as to outstanding Options, either (i) make appropriate provision for the continuation of such Options by substituting on an equitable basis for the Shares then subject to such Options either the
consideration payable with respect to the outstanding shares of Common Stock in connection with the Corporate Transaction or securities of any successor or acquiring entity; or (ii) upon written notice to the Participants, provide that all
Options must be exercised (either to the extent then exercisable or, at the discretion of the Administrator, or, upon a change of control of the Company, all Options being made fully exercisable for purposes of this Subparagraph), within a specified
number of days of the date of such notice, at the end of which period the Options shall terminate; or (iii) terminate all Options in exchange for a cash payment equal to the excess of the Fair Market Value of the Shares subject to such Options
(either to the extent then exercisable or, at the discretion of the Administrator, all Options being made fully exercisable for purposes of this Subparagraph) over the exercise price thereof. 

With respect to outstanding Stock Grants, the Administrator or the Successor Board, shall either (i) make appropriate
provisions for the continuation of such Stock Grants by substituting on an equitable basis for the Shares then subject to such Stock Grants either the consideration payable with respect to the outstanding Shares of Common Stock in connection with
the Corporate Transaction or securities of any successor or acquiring entity; or (ii) upon written notice to the Participants, provide that all Stock Grants must be accepted (to the extent then subject to acceptance) within a specified number
of days of the date of such notice, at the end of which period the offer of the Stock Grants shall terminate; or (iii) terminate all Stock Grants in exchange for a cash payment equal to the excess of the Fair Market Value of the Shares subject
to such Stock Grants over the purchase price thereof, if any. In addition, in the event of a Corporate Transaction, the Administrator may waive any or all Company repurchase rights with respect to outstanding Stock Grants. 

 

	 	C.	 Recapitalization or Reorganization. In the event of a recapitalization or reorganization of the Company other than a Corporate Transaction
pursuant to which securities of the Company or of another corporation are issued with respect to the outstanding shares of Common Stock, a Participant upon exercising or accepting a Stock Right after the recapitalization or reorganization shall be

  
 17 

	 	
entitled to receive for the purchase price paid upon such exercise or acceptance the number of replacement securities which would have been received if such Stock Right had been exercised or
accepted prior to such recapitalization or reorganization. 

  

	 	D.	Modification of ISOs. Notwithstanding the foregoing, any adjustments made pursuant to Subparagraph A, B or C above with respect to ISOs shall be made only after
the Administrator determines whether such adjustments would constitute a “modification” of such ISOs (as that term is defined in Section 424(h) of the Code) or would cause any adverse tax consequences for the holders of such ISOs. If
the Administrator determines that such adjustments made with respect to ISOs would constitute a modification of such ISOs, it may refrain from making such adjustments, unless the holder of an ISO specifically requests in writing that such adjustment
be made and such writing indicates that the holder has full knowledge of the consequences of such “modification” on his or her income tax treatment with respect to the ISO. 

 

	24.	ISSUANCES OF SECURITIES. 

Except as expressly provided herein, no issuance by the Company of shares of stock of any class, or securities convertible into shares of
stock of any class, shall affect, and no adjustment by reason thereof shall be made with respect to, the number or price of shares subject to Stock Rights. Except as expressly provided herein, no adjustments shall be made for dividends paid in cash
or in property (including without limitation, securities) of the Company prior to any issuance of Shares pursuant to a Stock Right. 
  

	25.	FRACTIONAL SHARES. 

 No
fractional shares shall be issued under the Plan and the person exercising a Stock Right shall receive from the Company cash in lieu of such fractional shares equal to the Fair Market Value thereof. 

 

	26.	CONVERSION OF ISOs INTO NON-QUALIFIED OPTIONS: TERMINATION OF ISOs. 

 The Administrator, at the written request of any Participant, may in its discretion take such actions as may be necessary to convert such Participant’s ISOs (or any portions thereof) that have not
been exercised on the date of conversion into Non-Qualified Options at any time prior to the expiration of such ISOs, regardless of whether the Participant is an employee of the Company or an Affiliate at the time of such conversion. At the time of
such conversion, the Administrator (with the consent of the Participant) may impose such conditions on the exercise of the resulting Non-Qualified Options as the Administrator in its discretion may determine, provided that such conditions shall not
be inconsistent with this Plan. Nothing in the Plan shall be deemed to give any Participant the right to have such Participant’s ISOs converted into Non-Qualified Options, and no such conversion shall occur until and unless the Administrator
takes appropriate action. The Administrator, with the consent of the Participant, may also terminate any portion of any ISO that has not been exercised at the time of such conversion. 

  
 18 

	27.	WITHHOLDING. 

 In the
event that any federal, state, or local income taxes, employment taxes, Federal Insurance Contributions Act (“F.I.C.A.”) withholdings or other amounts are required by applicable law or governmental regulation to be withheld from the
Participant’s salary, wages or other remuneration in connection with the exercise or acceptance of a Stock Right or in connection with a Disqualifying Disposition (as defined in Paragraph 28) or upon the lapsing of any right of repurchase, the
Company may withhold from the Participant’s compensation, if any, or may require that the Participant advance in cash to the Company, or to any Affiliate of the Company which employs or employed the Participant, the statutory minimum amount of
such withholdings unless a different withholding arrangement, including the use of shares of the Company’s Common Stock or a promissory note, is authorized by the Administrator (and permitted by law). For purposes hereof, the fair market value
of the shares withheld for purposes of payroll withholding shall be determined in the manner provided in Paragraph 1 above, as of the most recent practicable date prior to the date of exercise. If the fair market value of the shares withheld is less
than the amount of payroll withholdings required, the Participant may be required to advance the difference in cash to the Company or the Affiliate employer. The Administrator in its discretion may condition the exercise of an Option for less than
the then Fair Market Value on the Participant’s payment of such additional withholding. 
  

	28.	NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION. 

 Each Employee who receives an ISO must agree to notify the Company in writing immediately after the Employee makes a Disqualifying Disposition of any shares acquired pursuant to the exercise of an ISO. A
Disqualifying Disposition is defined in Section 424(c) of the Code and includes any disposition (including any sale or gift) of such shares before the later of (a) two years after the date the Employee was granted the ISO, or (b) one
year after the date the Employee acquired Shares by exercising the ISO, except as otherwise provided in Section 424(c) of the Code. If the Employee has died before such stock is sold, these holding period requirements do not apply and no
Disqualifying Disposition can occur thereafter. 
  

	29.	TERMINATION OF THE PLAN. 

The Plan will terminate on April 19, 2012, the date which is ten years from the earlier of the date of its adoption by the Board of
Directors and the date of its approval by the shareholders. The Plan may be terminated at an earlier date by vote of the shareholders or the Board of Directors of the Company; provided, however, that any such earlier termination shall not affect any
Option Agreements or Stock Grant Agreements executed prior to the effective date of such termination. 
  

	30.	AMENDMENT OF THE PLAN AND AGREEMENTS. 

 The Plan may be amended by the shareholders of the Company. The Plan may also be amended by the Administrator, including, without limitation, to the extent necessary to qualify any or all outstanding
Stock Rights granted under the Plan or Stock Rights to be granted under the Plan for favorable federal income tax treatment (including deferral of taxation upon exercise) as may be afforded incentive stock options under Section 422 of the Code,
and to the extent 

  
 19 

 
necessary to qualify the shares issuable upon exercise or acceptance of any outstanding Stock Rights granted, or Stock Rights to be granted, under the Plan for listing on any national securities
exchange or quotation in any national automated quotation system of securities dealers. Any amendment approved by the Administrator which the Administrator determines is of a scope that requires shareholder approval shall be subject to obtaining
such shareholder approval. Any modification or amendment of the Plan shall not, without the consent of a Participant, adversely affect his or her rights under a Stock Right previously granted to him or her. With the consent of the Participant
affected, the Administrator may amend outstanding Option Agreements and Stock Grant Agreements in a manner which may be adverse to the Participant but which is not inconsistent with the Plan. In the discretion of the Administrator, outstanding
Option Agreements and Stock Grant Agreements may be amended by the Administrator in a manner which is not adverse to the Participant. 
  

	31.	EMPLOYMENT OR OTHER RELATIONSHIP. 

 Nothing in this Plan or any Option Agreement or Stock Grant Agreement shall be deemed to prevent the Company or an Affiliate from terminating the employment, consultancy or director status of a
Participant, nor to prevent a Participant from terminating his or her own employment, consultancy or director status or to give any Participant a right to be retained in employment or other service by the Company or any Affiliate for any period of
time. 
  

	32.	GOVERNING LAW. 

 This Plan
shall be construed and enforced in accordance with the law of the State of Delaware. 

  
 20 

 Exhibit A 

NON-QUALIFIED STOCK OPTION AGREEMENT 
 GENETIX PHARMACEUTICALS INC. 
 AGREEMENT made as of the
             day of                  20__, between Genetix Pharmaceuticals Inc. (the
“Company”), a Delaware corporation having a principal place of business in Cambridge, Massachusetts, and              of
            , (the “Participant”), for whom the Board of Directors has authorized that the Option granted herein shall begin vesting as of
                    , 20        (the “Vesting Date”). 

WHEREAS, the Company desires to grant to the Participant an Option to purchase shares of its common stock, $0.01 par value per share (the
“Shares”), under and for the purposes set forth in the Company’s 2002 Employee, Director and Consultant Stock Plan (the “Plan”); 
 WHEREAS, the Company and the Participant understand and agree that any terms used and not defined herein have the same meanings as in the Plan; and 

WHEREAS, the Company and the Participant each intend that the Option granted herein shall be a Non-Qualified Option. 

NOW, THEREFORE, in consideration of the mutual covenants hereinafter set forth and for other good and valuable consideration, the parties
hereto agree as follows: 
  

	 	1.	GRANT OF OPTION. 

 The
Company hereby grants to the Participant the right and option to purchase all or any part of an aggregate of              Shares, on the terms and conditions and subject to all the
limitations set forth herein, under United States securities and tax laws, and in the Plan, which is incorporated herein by reference. The Participant acknowledges receipt of a copy of the Plan. 

 

	 	2.	PURCHASE PRICE. 

 The
purchase price of the Shares covered by the Option shall be $             per Share, subject to adjustment, as provided in the Plan, in the event of a stock split, reverse stock
split or other events affecting the holders of Shares (the “Purchase Price”). Payment shall be made in accordance with Paragraph 8 of the Plan. 
  

	 	3.	EXERCISABILITY OF OPTION. 

Subject to the terms and conditions set forth in this Agreement and the Plan, the Option granted hereby shall become exercisable as
follows: 
  

							
		 	On the first day of the first month following the Vesting Date	  	up to _________ Shares	  	
		 	On the first day of each month for ____ months thereafter	  	an additional _________ Shares	  	

 The foregoing rights are cumulative and are subject to the other terms and conditions of
this Agreement and the Plan. 
  

	 	4.	TERM OF OPTION. 

 The
Option shall terminate ten years from the date of this Agreement, but shall be subject to earlier termination as provided herein or in the Plan but shall be subject to earlier termination as provided herein or in the Plan. 

If the Participant ceases to be an employee, director or consultant of the Company or of an Affiliate (for any reason other than the
death or Disability of the Participant or termination of the Participant for “cause” (as defined in the Plan), the Option may be exercised, if it has not previously terminated, within three months after the date the Participant ceases to
be an employee, director or consultant of the Company or an Affiliate, or within the originally prescribed term of the Option, whichever is earlier, but may not be exercised thereafter. In such event, the Option shall be exercisable only to the
extent that the Option has become exercisable and is in effect at the date of such cessation of employment, directorship or consultancy. 
 Notwithstanding the foregoing, in the event of the Participant’s Disability or death within three months after the termination of employment, directorship or consultancy, the Participant or the
Participant’s Survivors may exercise the Option within one year after the date of the Participant’s termination of employment, directorship or consultancy, but in no event after the date of expiration of the term of the Option. 

In the event the Participant’s employment, directorship or consultancy is terminated by the Company or an Affiliate for
“cause” (as defined in the Plan), the Participant’s right to exercise any unexercised portion of this Option shall cease immediately as of the time the Participant is notified his or her employment, directorship or consultancy is
terminated for “cause”, and this Option shall thereupon terminate. Notwithstanding anything herein to the contrary, if subsequent to the Participant’s termination, but prior to the exercise of the Option, the Board of Directors of the
Company determines that, either prior or subsequent to the Participant’s termination, the Participant engaged in conduct which would constitute “cause,” then the Participant shall immediately cease to have any right to exercise the
Option and this Option shall thereupon terminate. 
 In the event of the Disability of the Participant, as determined in
accordance with the Plan, the Option shall be exercisable within one year after the Participant’s termination of service or, if earlier, within the term originally prescribed by the Option. In such event, the Option shall be exercisable:

  

	 	(a)	to the extent that the Option has become exercisable but has not been exercised as of the date of Disability; and 

 

	 	(b)	in the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of Disability of any additional vesting rights that
would have accrued on the next vesting date had the Participant not become Disabled. The proration shall be based upon the number of days accrued in the current vesting period prior to the date of Disability. 

  
 2 

 In the event of the death of the Participant while an employee, director or consultant of
the Company or of an Affiliate, the Option shall be exercisable by the Participant’s Survivors within one year after the date of death of the Participant or, if earlier, within the originally prescribed term of the Option. In such event, the
Option shall be exercisable: 
  

	 	(x)	to the extent that the Option has become exercisable but has not been exercised as of the date of death; and 

 

	 	(y)	in the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of death of any additional vesting rights that
would have accrued on the next vesting date had the Participant not died. The proration shall be based upon the number of days accrued in the current vesting period prior to the Participant’s date of death. 

 

	 	5.	METHOD OF EXERCISING OPTION. 

 Subject to the terms and conditions of this Agreement, the Option may be exercised by written notice to the Company or its designee, in substantially the form of Exhibit A attached hereto. Such
notice shall state the number of Shares with respect to which the Option is being exercised and shall be signed by the person exercising the Option. Payment of the purchase price for such Shares shall be made in accordance with Paragraph 8 of the
Plan. The Company shall deliver a certificate or certificates representing such Shares as soon as practicable after the notice shall be received, provided, however, that the Company may delay issuance of such Shares until completion of any action or
obtaining of any consent, which the Company deems necessary under any applicable law (including, without limitation, state securities or “blue sky” laws). The certificate or certificates for the Shares as to which the Option shall have
been so exercised shall be registered in the Company’s share register in the name of the person so exercising the Option (or, if the Option shall be exercised by the Participant and if the Participant shall so request in the notice exercising
the Option, shall be registered in the name of the Participant and another person jointly, with right of survivorship) and shall be delivered as provided above to or upon the written order of the person exercising the Option. In the event the Option
shall be exercised, pursuant to Section 4 hereof, by any person other than the Participant, such notice shall be accompanied by appropriate proof of the right of such person to exercise the Option. All Shares that shall be purchased upon the
exercise of the Option as provided herein shall be fully paid and nonassessable. 
  

	 	6.	PARTIAL EXERCISE. 

Exercise of this Option to the extent above stated may be made in part at any time and from time to time within the above limits, except
that no fractional share shall be issued pursuant to this Option. 

  
 3 

	 	7.	NON-ASSIGNABILITY. 

 The
Option shall not be transferable by the Participant otherwise than by will or by the laws of descent and distribution or pursuant to a qualified domestic relations order as defined by the Code or Title I of the Employee Retirement Income Security
Act or the rules thereunder. However, the Participant, with the approval of the Administrator, may transfer the Option for no consideration to or for the benefit of the Participant’s Immediate Family (including, without limitation, to a trust
for the benefit of the Participant’s Immediate Family or to a partnership or limited liability company for one or more members of the Participant’s Immediate Family), subject to such limits as the Administrator may establish, and the
transferee shall remain subject to all the terms and conditions applicable to the Option prior to such transfer and each such transferee shall so acknowledge in writing as a condition precedent to the effectiveness of such transfer. The term
“Immediate Family” shall mean the Participant’s spouse, former spouse, parents, children, stepchildren, adoptive relationships, sisters, brothers, nieces, nephews and grandchildren (and, for this purpose, shall also include the
Participant). Except as provided in the previous sentence, the Option shall be exercisable, during the Participant’s lifetime, only by the Participant (or, in the event of legal incapacity or incompetency, by the Participant’s guardian or
representative) and shall not be assigned, pledged or hypothecated in any way (whether by operation of law or otherwise) and shall not be subject to execution, attachment or similar process. Any attempted transfer, assignment, pledge, hypothecation
or other disposition of the Option or of any rights granted hereunder contrary to the provisions of this Section 7, or the levy of any attachment or similar process upon the Option shall be null and void. 

 

	 	8.	NO RIGHTS AS STOCKHOLDER UNTIL EXERCISE. 

 The Participant shall have no rights as a stockholder with respect to Shares subject to this Agreement until registration of the Shares in the Company’s share register in the name of the Participant.
Except as is expressly provided in the Plan with respect to certain changes in the capitalization of the Company, no adjustment shall be made for dividends or similar rights for which the record date is prior to the date of such registration.

  

	 	9.	ADJUSTMENTS. 

 The Plan
contains provisions covering the treatment of Options in a number of contingencies such as stock splits and mergers. Provisions in the Plan for adjustment with respect to stock subject to Options and the related provisions with respect to successors
to the business of the Company are hereby made applicable hereunder and are incorporated herein by reference. 
  

	 	10.	TAXES. 

 The Participant
acknowledges that upon exercise of the Option the Participant will be deemed to have taxable income measured by the difference between the then fair market value of the Shares received upon exercise and the price paid for such Shares pursuant to
this Agreement. The Participant acknowledges that any income or other taxes due from him or her with respect to this Option or the Shares issuable pursuant to this Option shall be the Participant’s responsibility. 

  
 4 

 The Participant agrees that the Company may withhold from the Participant’s
remuneration, if any, the minimum statutory amount of federal, state and local withholding taxes attributable to such amount that is considered compensation includable in such person’s gross income. At the Company’s discretion, the amount
required to be withheld may be withheld in cash from such remuneration, or in kind from the Shares otherwise deliverable to the Participant on exercise of the Option. The Participant further agrees that, if the Company does not withhold an amount
from the Participant’s remuneration sufficient to satisfy the Company’s income tax withholding obligation, the Participant will reimburse the Company on demand, in cash, for the amount under-withheld. 

 

	 	11.	PURCHASE FOR INVESTMENT. 

 Unless the
offering and sale of the Shares to be issued upon the particular exercise of the Option shall have been effectively registered under the Securities Act of 1933, as now in force or hereafter amended (the “1933 Act”), the Company shall be
under no obligation to issue the Shares covered by such exercise unless and until the following conditions have been fulfilled: 
  

	 	(a)	The person(s) who exercise the Option shall warrant to the Company, at the time of such exercise, that such person(s) are acquiring such Shares for their own respective
accounts, for investment, and not with a view to, or for sale in connection with, the distribution of any such Shares, in which event the person(s) acquiring such Shares shall be bound by the provisions of the following legend which shall be
endorsed upon the certificate(s) evidencing the Shares issued pursuant to such exercise: 

 “The shares
represented by this certificate have been taken for investment and they may not be sold or otherwise transferred by any person, including a pledgee, unless (1) either (a) a Registration Statement with respect to such shares shall be
effective under the Securities Act of 1933, as amended, or (b) the Company shall have received an opinion of counsel satisfactory to it that an exemption from registration under such Act is then available, and (2) there shall have been
compliance with all applicable state securities laws;” and 
  

	 	(b)	If the Company so requires, the Company shall have received an opinion of its counsel that the Shares may be issued upon such particular exercise in compliance with the
1933 Act without registration thereunder. Without limiting the generality of the foregoing, the Company may delay issuance of the Shares until completion of any action or obtaining of any consent, which the Company deems necessary under any
applicable law (including without limitation state securities or “blue sky” laws). 

  

	 	12.	RESTRICTIONS ON TRANSFER OF SHARES. 

 12.1 The Shares acquired by the Participant pursuant to the exercise of the Option granted hereby shall not be transferred by the Participant except as permitted herein. 

  
 5 

 12.2 In the event of the Participant’s termination of service for any reason, the
Company shall have the option, but not the obligation, to repurchase all or any part of the Shares issued pursuant to this Agreement (including, without limitation, Shares purchased after termination of employment, Disability or death in accordance
with Section 4 hereof). In the event the Company does not, upon the termination of service of the Participant (as described above), exercise its option pursuant to this Section 12.2, the restrictions set forth in the balance of this
Agreement shall not thereby lapse, and the Participant for himself or herself, his or her heirs, legatees, executors, administrators and other successors in interest, agrees that the Shares shall remain subject to such restrictions. The following
provisions shall apply to a repurchase under this Section 12.2: 
  

	 	(i)	The per share repurchase price of the Shares to be sold to the Company upon exercise of its option under this Section 12.2 shall be equal to the Fair Market Value
of each such Share determined in accordance with the Plan as of the date of termination of service; provided, however, in the event of a termination by the Company for “cause” (as defined in the Plan), the per share repurchase price of the
Shares to be sold to the Company upon exercise of its option under this Section 12.2 shall be equal to the Purchase Price. 

  

	 	(ii)	The Company’s option to repurchase the Participant’s Shares in the event of termination of service shall be valid for a period of 18 months commencing with
the date of such termination of service. 

  

	 	(iii)	In the event the Company shall be entitled to and shall elect to exercise its option to repurchase the Participant’s Shares under this Section 12.2, the
Company shall notify the Participant, or in case of death, his or her Survivor, in writing of its intent to repurchase the Shares. Such written notice may be mailed by the Company up to and including the last day of the time period provided for in
Section 12.2(h) for exercise of the Company’s option to repurchase. 

  

	 	(iv)	The written notice to the Participant shall specify the address at, and the time and date on, which payment of the repurchase price is to be made (the
“Closing”). The date specified shall not be less than ten days nor more than 60 days from the date of the mailing of the notice, and the Participant or his or her successor in interest with respect to the Shares shall have no further
rights as the owner thereof from and after the date specified in the notice. At the Closing, the repurchase price shall be delivered to the Participant or his or her successor in interest and the Shares being purchased, duly endorsed for transfer,
shall, to the extent that they are not then in the possession of the Company, be delivered to the Company by the Participant or his or her successor in interest. 

  
 6 

 12.3 It shall be a condition precedent to the validity of any sale or other transfer of any
Shares by the Participant that the following restrictions be complied with (except as hereinafter otherwise provided): 
  

	 	(i)	No Shares owned by the Participant may be sold, pledged or otherwise transferred (including by gift or devise) to any person or entity, voluntarily, or by operation of
law, except in accordance with the terms and conditions hereinafter set forth. 

  

	 	(ii)	Before selling or otherwise transferring all or part of the Shares, the Participant shall give written notice of such intention to the Company, which notice shall
include the name of the proposed transferee, the proposed purchase price per share, the terms of payment of such purchase price and all other matters relating to such sale or transfer and shall be accompanied by a copy of the binding written
agreement of the proposed transferee to purchase the Shares of the Participant. Such notice shall constitute a binding offer by the Participant to sell to the Company such number of the Shares then held by the Participant as are proposed to be sold
in the notice at the monetary price per share designated in such notice, payable on the terms offered to the Participant by the proposed transferee (provided, however, that the Company shall not be required to meet any non-monetary terms of the
proposed transfer, including, without limitation, delivery of other securities in exchange for the Shares proposed to be sold). The Company shall give written notice to the Participant as to whether such offer has been accepted in whole by the
Company within sixty days after its receipt of written notice from the Participant. The Company may only accept such offer in whole and may not accept such offer in part. Such acceptance notice shall fix a time, location and date for the closing on
such purchase (“Closing Date”) which shall not be less than ten nor more than sixty days after the giving of the acceptance notice. The place for such closing shall be at the Company’s principal office. At such closing, the
Participant shall accept payment as set forth herein and shall deliver to the Company in exchange therefor certificates for the number of Shares stated in the notice accompanied by duly executed instruments of transfer. 

 

	 	(iii)	If the Company shall fail to accept any such offer, the Participant shall be free to sell all, but not less than all, of the Shares set forth in his or her notice to
the designated transferee at the price and terms designated in the Participant’s notice, provided that (i) such sale is consummated within six months after the giving of notice by the Participant to the Company as aforesaid, and
(ii) the transferee first agrees in writing to be bound by the provisions of this Section 12 so that such transferee (and all subsequent transferees) shall thereafter only be permitted to sell or transfer the Shares in accordance with the
terms hereof. After the expiration of such six months, the provisions of this Section 12.3 shall again apply with respect to any proposed voluntary transfer of the Participant’s Shares. 

  
 7 

	 	(iv)	The restrictions on transfer contained in this Section 12.3 shall not apply to (a) transfers by the Participant to his or her spouse or children or to a trust
for the benefit of his or her spouse or children, (b) transfers by the Participant to his or her guardian or conservator, and (c) or transfers by the Participant, in the event of his or her death, to his or her executor(s) or
administrator(s) or to trustee(s) under his or her will (collectively, “Permitted Transferees”); provided however, that in any such event the Shares so transferred in the hands of each such Permitted Transferee shall remain subject to this
Agreement, and each such Permitted Transferee shall so acknowledge in writing as a condition precedent to the effectiveness of such transfer. 

  

	 	(v)	The provisions of this Section 12.3 may be waived by the Company. Any such waiver may be unconditional or based upon such conditions as the Company may impose.

 12.4 In the event that the Participant or his or her successor in interest fails to deliver the Shares to be
repurchased by the Company under this Agreement, the Company may elect (a) to establish a segregated account in the amount of the repurchase price, such account to be turned over to the Participant or his or her successor in interest upon
delivery of such Shares, and (b) immediately to take such action as is appropriate to transfer record title of such Shares from the Participant to the Company and to treat the Participant and such Shares in all respects as if delivery of such
Shares had been made as required by this Agreement. The Participant hereby irrevocably grants the Company a power of attorney which shall be coupled with an interest for the purpose of effectuating the preceding sentence. 

12.5 If the Company shall pay a stock dividend or declare a stock split on or with respect to any of its Common Stock, or otherwise
distribute securities of the Company to the holders of its Common Stock, the number of shares of stock or other securities of the Company issued with respect to the shares then subject to the restrictions contained in this Agreement shall be added
to the Shares subject to the Company’s rights to repurchase pursuant to this Agreement. If the Company shall distribute to its stockholders shares of stock of another corporation, the shares of stock of such other corporation, distributed with
respect to the Shares then subject to the restrictions contained in this Agreement, shall be added to the Shares subject to the Company’s rights to repurchase pursuant to this Agreement. 

12.6 If the outstanding shares of Common Stock of the Company shall be subdivided into a greater number of shares or combined into a
smaller number of shares, or in the event of a reclassification of the outstanding shares of Common Stock of the Company, or if the Company shall be a party to a merger, consolidation or capital reorganization, there shall be substituted for the
Shares then subject to the restrictions contained in this Agreement such amount and kind of securities as are issued in such subdivision, combination, reclassification, merger, consolidation or capital reorganization in respect of the Shares subject
immediately prior thereto to the Company’s rights to repurchase pursuant to this Agreement. 
 12.7 The Company shall not
be required to transfer any Shares on its books which shall have been sold, assigned or otherwise transferred in violation of this Agreement, or to treat as owner of such Shares, or to accord the right to vote as such owner or to pay dividends to,
any person or organization to which any such Shares shall have been so sold, assigned or otherwise transferred, in violation of this Agreement. 

  
 8 

 12.8 The provisions of Sections 12.1, 12.2 and 12.3 shall terminate upon the effective date
of the registration of the Shares pursuant to the Securities Exchange Act of 1934. 
 12.9 If, in connection with a registration
statement filed by the Company pursuant to the 1933 Act, the Company or its underwriter so requests, the Participant will agree not to sell any Shares for a period not to exceed 180 days following the effectiveness of such registration. 

12.10 The Participant acknowledges and agrees that neither the Company, its shareholders nor its directors and officers, has any duty or
obligation to disclose to the Participant any material information regarding the business of the Company or affecting the value of the Shares before, at the time of, or following a termination of the employment of the Participant by the Company,
including, without limitation, any information concerning plans for the Company to make a public offering of its securities or to be acquired by or merged with or into another firm or entity. 

12.11 All certificates representing the Shares to be issued to the Participant pursuant to this Agreement shall have endorsed thereon a
legend substantially as follows: “The shares represented by this certificate are subject to restrictions set forth in a Non-Qualified Stock Option Agreement dated
                , 20         with this Company, a copy of which Agreement is available for inspection at the
offices of the Company or will be made available upon request.” 
  

	 	13.	NO OBLIGATION TO MAINTAIN RELATIONSHIP. 

 The Company is not by the Plan or this Option obligated to continue the Participant as an employee, director or consultant of the Company or an Affiliate. The Participant acknowledges: (i) that the
Plan is discretionary in nature and may be suspended or terminated by the Company at any time; (ii) that the grant of the Option is a one-time benefit which does not create any contractual or other right to receive future grants of options, or
benefits in lieu of options; (iii) that all determinations with respect to any such future grants, including, but not limited to, the times when options shall be granted, the number of shares subject to each option, the option price, and the
time or times when each option shall be exercisable, will be at the sole discretion of the Company; (iv) that the Participant’s participation in the Plan is voluntary; (v) that the value of the Option is an extraordinary item of
compensation which is outside the scope of the Participant’s employment contract, if any; and (vi) that the Option is not part of normal or expected compensation for purposes of calculating any severance, resignation, redundancy, end of
service payments, bonuses, long-service awards, pension or retirement benefits or similar payments. 
  

	 	14.	NOTICES. 

 Any notices
required or permitted by the terms of this Agreement or the Plan shall be given by recognized courier service, facsimile, registered or certified mail, return receipt requested, addressed as follows: 

					
			
		 	If to the Company:	  	 President
 Genetix
Pharmaceuticals Inc.
 840 Memorial Drive, 5th floor
 Cambridge, MA 02139

			
		 	If to the Participant:	  	At the address set forth on the first page of this Agreement.

  
 9 

 or to such other address or addresses of which notice in the same manner has previously been given. Any such
notice shall be deemed to have been given upon the earlier of receipt, one business day following delivery to a recognized courier service or three business days following mailing by registered or certified mail. 

 

	 	15.	GOVERNING LAW. 

 This
Agreement shall be construed and enforced in accordance with the law of the State of Delaware, without giving effect to the conflict of law principles thereof. Any controversy, dispute or claim arising out of or in connection with this Agreement, or
the breach, termination or validity hereof, shall be settled by final and binding arbitration to be conducted by an arbitration tribunal in Boston, Massachusetts, pursuant to the rules of the American Arbitration Association. The arbitration
tribunal shall consist of three arbitrators. The party initiating arbitration shall nominate one arbitrator in the request for arbitration and the other party shall nominate a second in the answer thereto within thirty (30) days of receipt of
the request. The two arbitrators so named will then jointly appoint the third arbitrator. If the answering party fails to nominate its arbitrator within the thirty (30) day period, or if the arbitrators named by the parties fail to agree on the
third arbitrator within sixty (60) days, the office of the American Arbitration Association in Boston, Massachusetts shall make the necessary appointments of such arbitrator(s). The decision or award of the arbitration tribunal (by a majority
determination, or if there is no majority, then by the determination of the third arbitrator, if any) shall be final, and judgment upon such decision or award may be entered in any competent court or application may be made to any competent court
for judicial acceptance of such decision or award and an order of enforcement. In the event of any procedural matter not covered by the aforesaid rules, the procedural law of Massachusetts shall govern. 

 

	 	16.	BENEFIT OF AGREEMENT. 

Subject to the provisions of the Plan and the other provisions hereof, this Agreement shall be for the benefit of and shall be binding
upon the heirs, executors, administrators, successors and assigns of the parties hereto. 
  

	 	17.	ENTIRE AGREEMENT. 

 This
Agreement, together with the Plan, embodies the entire agreement and understanding between the parties hereto with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject
matter hereof. No statement, representation, warranty, covenant or agreement not expressly set forth in this Agreement shall affect or be used to interpret, change or restrict, the express terms and provisions of this Agreement, provided, however,
in any event, this Agreement shall be subject to and governed by the Plan. 

  
 10 

	 	18.	MODIFICATIONS AND AMENDMENTS. 

 The terms and provisions of this Agreement may be modified or amended as provided in the Plan. 
  

	 	19.	WAIVERS AND CONSENTS. 

Except as provided in the Plan, the terms and provisions of this Agreement may be waived, or consent for the departure therefrom granted,
only by written document executed by the party entitled to the benefits of such terms or provisions. No such waiver or consent shall be deemed to be or shall constitute a waiver or consent with respect to any other terms or provisions of this
Agreement, whether or not similar. Each such waiver or consent shall be effective only in the specific instance and for the purpose for which it was given, and shall not constitute a continuing waiver or consent. 

 

	 	20.	DATA PRIVACY. 

 By
entering into this Agreement, the Participant: (i) authorizes the Company and each Affiliate, and any agent of the Company or any Affiliate administering the Plan or providing Plan record keeping services, to disclose to the Company or any of
its Affiliates such information and data as the Company or any such Affiliate shall request in order to facilitate the grant of options and the administration of the Plan; (ii) waives any data privacy rights he or she may have with respect to
such information; and (iii) authorizes the Company and each Affiliate to store and transmit such information in electronic form. 
  

	 	21.	CONSENT OF SPOUSE. 

 If
the Participant is married as of the date of this Agreement, the Participant’s spouse shall execute a Consent of Spouse in the form of Exhibit B hereto, effective as of the date hereof. Such consent shall not be deemed to confer or
convey to the spouse any rights in the Shares that do not otherwise exist by operation of law or the agreement of the parties. If the Participant marries or remarries subsequent to the date hereof, the Participant shall, not later than 60 days
thereafter, obtain his or her new spouse’s acknowledgement of and consent to the existence and binding effect of Section 12.2 of this Agreement by such spouse’s executing and delivering a Consent of Spouse in the form of Exhibit B.

 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK] 

  
 11 

 IN WITNESS WHEREOF, the Company has caused this Non-Qualified Stock Option Agreement to be
executed by its duly authorized officer, and the Participant has hereunto set his or her hand, all as of the day and year first above written. 
  

			
	GENETIX PHARMACEUTICALS INC.
		
	By:	 	 
		 	Name:
		 	Title:

  

	
	  
	Participant Name:

 Exhibit A 

NOTICE OF EXERCISE OF NON-QUALIFIED STOCK OPTION 
 [Form for Unregistered Shares] 
  

	To:	Genetix Pharmaceuticals Inc. 

 Ladies and
Gentlemen: 
 I hereby exercise my Non-Qualified Stock Option to purchase
             shares (the “Shares”) of the common stock, $0.01 par value, of Genetix Pharmaceuticals Inc. (the “Company”), at the exercise price of
$            per share, pursuant to and subject to the terms of that certain Non-Qualified Stock Option Agreement between the undersigned and the Company dated
                , 20__. 
 I am aware
that the Shares have not been registered under the Securities Act of 1933, as amended (the “1933 Act”), or any state securities laws. I understand that the reliance by the Company on exemptions under the 1933 Act is predicated in part upon
the truth and accuracy of the statements by me in this Notice of Exercise. 
 I hereby represent and warrant that (1) I
have been furnished with all information which I deem necessary to evaluate the merits and risks of the purchase of the Shares; (2) I have had the opportunity to ask questions concerning the Shares and the Company and all questions posed have
been answered to my satisfaction; (3) I have been given the opportunity to obtain any additional information I deem necessary to verify the accuracy of any information obtained concerning the Shares and the Company; and (4) I have such
knowledge and experience in financial and business matters that I am able to evaluate the merits and risks of purchasing the Shares and to make an informed investment decision relating thereto. 

I hereby represent and warrant that I am purchasing the Shares for my own personal account for investment and not with a view to the sale
or distribution of all or any part of the Shares. 
 I understand that because the Shares have not been registered under the
1933 Act, I must continue to bear the economic risk of the investment for an indefinite time and the Shares cannot be sold unless the Shares are subsequently registered under applicable federal and state securities laws or an exemption from such
registration requirements is available. 
 I agree that I will in no event sell or distribute or otherwise dispose of all or any
part of the Shares unless (1) there is an effective registration statement under the 1933 Act and applicable state securities laws covering any such transaction involving the Shares or (2) the Company receives an opinion of my legal
counsel (concurred in by legal counsel for the Company) stating that such transaction is exempt from registration or the Company otherwise satisfies itself that such transaction is exempt from registration. 

 I consent to the placing of a legend on my certificate for the Shares stating that the
Shares have not been registered and setting forth the restriction on transfer contemplated hereby and to the placing of a stop transfer order on the books of the Company and with any transfer agents against the Shares until the Shares may be legally
resold or distributed without restriction. 
 I understand that at the present time Rule 144 of the Securities and Exchange
Commission (the “SEC”) may not be relied on for the resale or distribution of the Shares by me. I understand that the Company has no obligation to me to register the sale of the Shares with the SEC and has not represented to me that it
will register the sale of the Shares. 
 I understand the terms and restrictions on the right to dispose of the Shares set forth
in the 2002 Employee, Director and Consultant Stock Plan and the Non-Qualified Option Agreement, both of which I have carefully reviewed. I consent to the placing of a legend on my certificate for the Shares referring to such restriction and the
placing of stop transfer orders until the Shares may be transferred in accordance with the terms of such restrictions. 
 I have
considered the Federal, state and local income tax implications of the exercise of my Option and the purchase and subsequent sale of the Shares. 
 I am paying the option exercise price for the Shares as follows: 
  

 
 Please issue the stock
certificate for the Shares (check one): 
  

	 	 ̈	to me; or 

  

	 	 ̈	to me and                     , as joint tenants with right
of survivorship and mail the certificate to me at the following address: 

	 	 	

  

 
  

 
  

 My mailing address for shareholder communications, if different from the address listed
above is: 
  
  

 
  

 
  

 

	
	Very truly yours.
	  
	Employee (signature)
	  
	Print Name
	  
	Date
	  
	Social Security Number

 Exhibit A 

(Form for Registered Shares) 
 NOTICE OF EXERCISE OF NON-QUALIFIED STOCK OPTION 
  

	TO:	Genetix Pharmaceuticals Inc. 

 IMPORTANT NOTICE:
This form of Notice of Exercise may only be used at such time as the Company has filed a Registration Statement with the Securities and Exchange Commission under which the issuance of the Shares for which this exercise is being made is registered
and such Registration Statement remains effective. 
 Ladies and Gentlemen: 

I hereby exercise my Non-Qualified Stock Option to purchase
            shares (the “Shares”) of the common stock, $0.01 par value, of Genetix Pharmaceuticals Inc. (the “Company”), at the exercise price of
$            per share, pursuant to and subject to the terms of that certain Non-Qualified Stock Option Agreement between the undersigned and the Company dated
                , 20__. 
 I understand
the nature of the investment I am making and the financial risks thereof. I am aware that it is my responsibility to have consulted with competent tax and legal advisors about the relevant national, state and local income tax and securities laws
affecting the exercise of the Option and the purchase and subsequent sale of the Shares. 
 I am paying the option exercise
price for the Shares as follows: 
 Please issue the Shares (check one): 

 

	 	 ̈	to me; or 

  

	 	 ̈	to me and                     , as joint tenants with right
of survivorship 

 at the following address: 
  

 
  

 
  

 

 My mailing address for shareholder communications, if different from the address listed
above is: 
  
  

 
  

 
  

 

	
	Very truly yours.
	  
	Employee (signature)
	  
	Print Name
	  
	Date
	  
	Social Security Number

 Exhibit B 

CONSENT OF SPOUSE 
 I,                                 ,
spouse of                         , acknowledge that I have read the Non-Qualified Stock Option Agreement dated as of
                    , 20        (the “Agreement”) to which this Consent is attached
as Exhibit B and that I know its contents. Capitalized terms used and not defined herein shall have the meanings assigned to such terms in the Agreement. I am aware that by its provisions the Shares granted to my spouse pursuant to the
Agreement are subject to a right of repurchase in favor of Genetix Pharmaceuticals Inc. (the “Company”) and that, accordingly, the Company has the right to repurchase up to all of the Shares of which I may become possessed as a result of a
gift from my spouse or a court decree and/or any property settlement in any domestic litigation. 
 I hereby agree that my
interest, if any, in the Shares subject to the Agreement shall be irrevocably bound by the Agreement and further understand and agree that any community property interest I may have in the Shares shall be similarly bound by the Agreement.

 I agree to the repurchase right described in Section 12.2 of the Agreement and I hereby consent to the repurchase of the
Shares by the Company and the sale of the Shares by my spouse or my spouse’s legal representative in accordance with the provisions of the Agreement. Further, as part of the consideration for the Agreement, I agree that at my death, if I have
not disposed of any interest of mine in the Shares by an outright bequest of the Shares to my spouse, then the Company shall have the same rights against my legal representative to exercise its rights of repurchase with respect to any interest of
mine in the Shares as it would have had pursuant to the Agreement if I had acquired the Shares pursuant to a court decree in domestic litigation. 
 I AM AWARE THAT THE LEGAL, FINANCIAL AND RELATED MATTERS CONTAINED IN THE AGREEMENT ARE COMPLEX AND THAT I AM FREE TO SEEK INDEPENDENT PROFESSIONAL GUIDANCE OR COUNSEL WITH RESPECT TO THIS CONSENT. I HAVE
EITHER SOUGHT SUCH GUIDANCE OR COUNSEL OR DETERMINED AFTER REVIEWING THE AGREEMENT CAREFULLY THAT I WILL WAIVE SUCH RIGHT. 

Dated as of the                 day of
                    , 20        . 

	
	
	  
	Print name:

 Exhibit B 
 NOTE: Unless approved by the Administrator (as defined in the Plan), delete Exhibit C hereto and the bold-faced and bracketed language in Section 3. 

FORM OF 

INCENTIVE STOCK OPTION AGREEMENT 
 GENETIX PHARMACEUTICALS INC. 
 AGREEMENT made as of the
            day of                 , 20__, between Genetix Pharmaceuticals Inc. (the
“Company”), a Delaware corporation having a principal place of business in Cambridge, Massachusetts, and             of
            , an employee of the Company (the “Employee”), for whom the Board of Directors has authorized that the Option granted herein shall begin vesting as of
                (the “Vesting Date”). 
 WHEREAS, the Company desires to grant to the Employee an Option to purchase shares of its common stock, $0.01 par value per share (the “Shares”), under and for the purposes set forth in the
Company’s 2002 Employee, Director and Consultant Stock Plan (the “Plan”); 
 WHEREAS, the Company and the
Employee understand and agree that any terms used and not defined herein have the same meanings as in the Plan; and 
 WHEREAS,
the Company and the Employee each intend that the Option granted herein qualify as an ISO. 
 NOW, THEREFORE, in consideration
of the mutual covenants hereinafter set forth and for other good and valuable consideration, the parties hereto agree as follows: 
  

	 	1.	GRANT OF OPTION. 

 The
Company hereby grants to the Employee the right and option to purchase all or any part of an aggregate of              Shares, on the terms and conditions and subject to all the
limitations set forth herein, under United States securities and tax laws, and in the Plan, which is incorporated herein by reference. The Employee acknowledges receipt of a copy of the Plan. 

 

	 	2.	PURCHASE PRICE. 

 The
purchase price of the Shares covered by the Option shall be $             per Share, subject to adjustment, as provided in the Plan, in the event of a stock split, reverse stock
split or other events affecting the holders of Shares (the “Purchase Price”). Payment shall be made in accordance with Paragraph 8 of the Plan. 

	 	3.	EXERCISABILITY OF OPTION. 

Subject to the terms and conditions set forth in this Agreement and the Plan, the Option granted hereby shall become exercisable as
follows: 
  

					
	 	  	On the first anniversary of the Vesting Date	  	up to _________ Shares
			
		  	On the last day of each month thereafter for 36 months	  	an additional ________ Shares

 The foregoing rights are cumulative and are subject to the other terms and conditions of this Agreement
and the Plan. 
 [Optional: Alternatively, at the election of the Employee, the Option may be
exercised in whole or in part at any time as to Shares which have not yet vested in accordance with the above schedule; provided however, as a condition to exercising the Option for such unvested Shares, the Employee shall execute a Restricted Stock
Agreement in the form attached hereto as Exhibit C.| 
 [Optional:
Notwithstanding the foregoing, in the event of a Change of Control (as defined below),         % of the Shares which would have vested in each vesting installment remaining under this Option will be
vested for purposes of Section 23(B) of the Plan unless this Option has otherwise expired or been terminated pursuant to its terms or the terms of the Plan. 
 Change of Control means the occurrence of any of the following events: 
  

	 	(i)	Ownership. Any “Person” (as such term is used in Sections 13(d) and 14(d) of the Securities Exchange Act of 1934, as amended) becomes the
“Beneficial Owner” (as defined in Rule 13d-3 under said Act), directly or indirectly, of securities of the Company representing 50% or more of the total voting power represented by the Company’s then outstanding voting securities
(excluding for this purpose the Company or its Affiliates or any employee benefit plan of the Company) pursuant to a transaction or a series of related transactions which the Board of Directors does not approve; or 

 

	 	(ii)	Merger/Sale of Assets. A merger or consolidation of the Company whether or not approved by the Board of Directors, other than a merger or consolidation which
would result in the voting securities of the Company outstanding immediately prior thereto continuing to represent (either by remaining outstanding or by being converted into voting securities of the surviving entity or the parent of such
corporation) at least 50% of the total voting power represented by the voting securities of the Company or such surviving entity or parent of such corporation outstanding immediately after such merger or consolidation, or the stockholders of the
Company approve an agreement for the sale or disposition by the Company of all or substantially all of the Company’s assets; or 

  
 B-2

	 	(iii)	Change in Board Composition. A change in the composition of the Board of Directors, as a result of which fewer than a majority of the directors are Incumbent
Directors. “Incumbent Directors” shall mean directors who either (A) are directors of the Company as of the date of this Agreement, or (B) are elected, or nominated for election, to the Board of Directors with the affirmative
votes of at least a majority of the Incumbent Directors at the time of such election or nomination (but shall not include an individual whose election or nomination is in connection with an actual or threatened proxy contest relating to the election
of directors to the Company).] 

  

	 	4.	TERM OF OPTION. 

 The
Option shall terminate ten years from the date of this Agreement, but shall be subject to earlier termination as provided herein or in the Plan or, if the Employee owns as of the date hereof more than 10% of the total combined voting power of all
classes of capital stock of the Company or an Affiliate, five years from the date of this Agreement, but shall be subject to earlier termination as provided herein or in the Plan. 

If the Employee ceases to be an employee of the Company or of an Affiliate (for any reason other than the death or Disability of the
Employee or termination of the Employee’s employment for “cause” (as defined in the Plan), the Option may be exercised, if it has not previously terminated, within three months after the date the Employee ceases to be an employee of
the Company or an Affiliate, or within the originally prescribed term of the Option, whichever is earlier, but may not be exercised thereafter. In such event, the Option shall be exercisable only to the extent that the Option has become exercisable
and is in effect at the date of such cessation of employment. 
 Notwithstanding the foregoing, in the event of the
Employee’s Disability or death within three months after the termination of employment, the Employee or the Employee’s Survivors may exercise the Option within one year after the date of the Employee’s termination of employment, but
in no event after the date of expiration of the term of the Option. 
 In the event the Employee’s employment is terminated
by the Employee’s employer for “cause” (as defined in the Plan), the Employee’s right to exercise any unexercised portion of this Option shall cease immediately as of the time the Employee is notified his or her employment is
terminated for ‘‘cause”, and this Option shall thereupon terminate. Notwithstanding anything herein to the contrary, if subsequent to the Employee’s termination as an employee, but prior to the exercise of the Option, the Board
of Directors of the Company determines that, either prior or subsequent to the Employee’s termination, the Employee engaged in conduct which would constitute “cause.” then the Employee shall immediately cease to have any right to
exercise the Option and this Option shall thereupon terminate. 

  
 B-3

 In the event of the Disability of the Employee, as determined in accordance with the Plan,
the Option shall be exercisable within one year after the Employee’s termination of employment or, if earlier, within the term originally prescribed by the Option. In such event, the Option shall be exercisable: 

 

	 	(a)	to the extent that the Option has become exercisable but has not been exercised as of the date of Disability; and 

 

	 	(b)	in the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of Disability of any additional vesting rights that
would have accrued on the next vesting date had the Employee not become Disabled. The proration shall be based upon the number of days accrued in the current vesting period prior to the date of Disability. 

In the event of the death of the Employee while an employee of the Company or of an Affiliate, the Option shall be exercisable by the
Employee’s Survivors within one year after the date of death of the Employee or, if earlier, within the originally prescribed term of the Option. In such event, the Option shall be exercisable: 

 

	 	(x)	to the extent that the Option has become exercisable but has not been exercised as of the date of death; and 

 

	 	(y)	in the event rights to exercise the Option accrue periodically, to the extent of a pro rata portion through the date of death of any additional vesting rights that
would have accrued on the next vesting date had the Employee not died. The proration shall be based upon the number of days accrued in the current vesting period prior to the Employee’s date of death. 

 

	 	5.	METHOD OF EXERCISING OPTION. 

 Subject to the terms and conditions of this Agreement, the Option may be exercised by written notice to the Company or its designee, in substantially the form of Exhibit A attached hereto. Such
notice shall state the number of Shares with respect to which the Option is being exercised and shall be signed by the person exercising the Option. Payment of the purchase price for such Shares shall be made in accordance with Paragraph 8 of the
Plan. The Company shall deliver a certificate or certificates representing such Shares as soon as practicable after the notice shall be received, provided, however, that the Company may delay issuance of such Shares until completion of any action or
obtaining of any consent, which the Company deems necessary under any applicable law (including, without limitation, state securities or “blue sky” laws). The certificate or certificates for the Shares as to which the Option shall have
been so exercised shall be registered in the Company’s share register in the name of the person so exercising the Option (or, if the Option shall be exercised by the Employee and if the Employee shall so request in the notice exercising the
Option, shall be registered in the name of the Employee and another person jointly, with right of survivorship) and shall be delivered as provided above to or upon the written order of the person exercising the Option. In the event the

  
 B-4

 
Option shall be exercised, pursuant to Section 4 hereof, by any person other than the Employee, such notice shall be accompanied by appropriate proof of the right of such person to exercise
the Option. All Shares that shall be purchased upon the exercise of the Option as provided herein shall be fully paid and nonassessable. 
  

	 	6.	PARTIAL EXERCISE. 

Exercise of this Option to the extent above stated may be made in part at any time and from time to time within the above limits, except
that no fractional share shall be issued pursuant to this Option. 
  

	 	7.	NON-ASSIGNABILITY. 

 The
Option shall not be transferable by the Employee otherwise than by will or by the laws of descent and distribution. The Option shall be exercisable, during the Employee’s lifetime, only by the Employee (or, in the event of legal incapacity or
incompetency, by the Employee’s guardian or representative) and shall not be assigned, pledged or hypothecated in any way (whether by operation of law or otherwise) and shall not be subject to execution, attachment or similar process. Any
attempted transfer, assignment, pledge, hypothecation or other disposition of the Option or of any rights granted hereunder contrary to the provisions of this Section 7, or the levy of any attachment or similar process upon the Option shall be
null and void. 
  

	 	8.	NO RIGHTS AS STOCKHOLDER UNTIL EXERCISE. 

 The Employee shall have no rights as a stockholder with respect to Shares subject to this Agreement until registration of the Shares in the Company’s share register in the name of the Employee.
Except as is expressly provided in the Plan with respect to certain changes in the capitalization of the Company, no adjustment shall be made for dividends or similar rights for which the record date is prior to the date of such registration.

  

	 	9.	ADJUSTMENTS. 

 The Plan
contains provisions covering the treatment of Options in a number of contingencies such as stock splits and mergers. Provisions in the Plan for adjustment with respect to stock subject to Options and the related provisions with respect to successors
to the business of the Company are hereby made applicable hereunder and are incorporated herein by reference. 
  

	 	10.	TAXES. 

 The Employee
acknowledges that any income or other taxes due from him or her with respect to this Option or the Shares issuable pursuant to this Option shall be the Employee’s responsibility. 

In the event of a Disqualifying Disposition (as defined in Section 15 below) or if the Option is converted into a Non-Qualified
Option and such Non-Qualified Option is exercised, the Employee agrees that the Company may withhold from the Employee’s remuneration, if any, 

  
 B-5

 
the minimum statutory amount of federal, state and local withholding taxes attributable to such amount that is considered compensation includable in such person’s gross income. At the
Company’s discretion, the amount required to be withheld may be withheld in cash from such remuneration, or in kind from the Shares otherwise deliverable to the Employee on exercise of the Option. The Employee further agrees that, if the
Company does not withhold an amount from the Employee’s remuneration sufficient to satisfy the Company’s income tax withholding obligation, the Employee will reimburse the Company on demand, in cash, for the amount under-withheld.

  

	 	11.	PURCHASE FOR INVESTMENT. 

Unless the offering and sale of the Shares to be issued upon the particular exercise of the Option shall have been effectively registered
under the Securities Act of 1933, as now in force or hereafter amended (the “1933 Act”), the Company shall be under no obligation to issue the Shares covered by such exercise unless and until the following conditions have been fulfilled:

  

	 	(a)	The person(s) who exercise the Option shall warrant to the Company, at the time of such exercise, that such person(s) are acquiring such Shares for their own respective
accounts, for investment, and not with a view to, or for sale in connection with, the distribution of any such Shares, in which event the person(s) acquiring such Shares shall be bound by the provisions of the following legend which shall be
endorsed upon the certificate(s) evidencing the Shares issued pursuant to such exercise: 

 “The shares
represented by this certificate have been taken for investment and they may not be sold or otherwise transferred by any person, including a pledgee, unless (1) either (a) a Registration Statement with respect to such shares shall be
effective under the Securities Act of 1933, as amended, or (b) the Company shall have received an opinion of counsel satisfactory to it that an exemption from registration under such Act is then available, and (2) there shall have been
compliance with all applicable state securities laws;” and 
  

	 	(b)	If the Company so requires, the Company shall have received an opinion of its counsel that the Shares may be issued upon such particular exercise in compliance with the
1933 Act without registration thereunder. Without limiting the generality of the foregoing, the Company may delay issuance of the Shares until completion of any action or obtaining of any consent, which the Company deems necessary under any
applicable law (including without limitation state securities or “blue sky” laws). 

  

	 	12.	RESTRICTIONS ON TRANSFER OF SHARES. 

 12.1 The Shares acquired by the Employee pursuant to the exercise of the Option granted hereby shall not be transferred by the Employee except as permitted herein. 

  
 B-6

 12.2 In the event of the Employee’s termination of employment for any reason, the
Company shall have the option, but not the obligation, to repurchase all or any part of the Shares issued pursuant to this Agreement (including, without limitation, Shares purchased after termination of employment, Disability or death in accordance
with Section 4 hereof). In the event the Company does not, upon the termination of employment of the Employee (as described above), exercise its option pursuant to this Section 12.2, the restrictions set forth in the balance of this
Agreement shall not thereby lapse, and the Employee for himself or herself, his or her heirs, legatees, executors, administrators and other successors in interest, agrees that the Shares shall remain subject to such restrictions. The following
provisions shall apply to a repurchase under this Section 12.2: 
  

	 	(i)	The per share repurchase price of the Shares to be sold to the Company upon exercise of its option under this Section 12.2 shall be equal to the Fair Market Value
of each such Share determined in accordance with the Plan as of the date of termination of employment; provided, however, in the event of a termination by the Company for “cause” (as defined in the Plan), the per share repurchase price of
the Shares to be sold to the Company upon exercise of its option under this Section 12.2 shall be equal to the Purchase Price. 

  

	 	(ii)	The Company’s option to repurchase the Employee’s Shares in the event of termination of service shall be valid for a period of 18 months commencing with the
date of such termination of service. 

  

	 	(iii)	In the event the Company shall be entitled to and shall elect to exercise its option to repurchase the Employee’s Shares under this Section 12.2, the Company
shall notify the Employee, or in case of death, his or her Survivor, in writing of its intent to repurchase the Shares. Such written notice may be mailed by the Company up to and including the last day of the time period provided for in
Section 12.2(h) for exercise of the Company’s option to repurchase. 

  

	 	(iv)	The written notice to the Employee shall specify the address at, and the time and date on, which payment of the repurchase price is to be made (the
“Closing”). The date specified shall not be less than ten days nor more than 60 days from the date of the mailing of the notice, and the Employee or his or her successor in interest with respect to the Shares shall have no further rights
as the owner thereof from and after the date specified in the notice. At the Closing, the repurchase price shall be delivered to the Employee or his or her successor in interest and the Shares being purchased, duly endorsed for transfer, shall, to
the extent that they are not then in the possession of the Company, be delivered to the Company by the Employee or his or her successor in interest. 

  
 B-7

 12.3 It shall be a condition precedent to the validity of any sale or other transfer of any
Shares by the Employee that the following restrictions be complied with (except as hereinafter otherwise provided): 
  

	 	(i)	No Shares owned by the Employee may be sold, pledged or otherwise transferred (including by gift or devise) to any person or entity, voluntarily, or by operation of
law, except in accordance with the terms and conditions hereinafter set forth. 

  

	 	(ii)	Before selling or otherwise transferring all or part of the Shares, the Employee shall give written notice of such intention to the Company, which notice shall include
the name of the proposed transferee, the proposed purchase price per share, the terms of payment of such purchase price and all other matters relating to such sale or transfer and shall be accompanied by a copy of the binding written agreement of
the proposed transferee to purchase the Shares of the Employee. Such notice shall constitute a binding offer by the Employee to sell to the Company such number of the Shares then held by the Employee as are proposed to be sold in the notice at the
monetary price per share designated in such notice, payable on the terms offered to the Employee by the proposed transferee (provided, however, that the Company shall not be required to meet any non-monetary terms of the proposed transfer,
including, without limitation, delivery of other securities in exchange for the Shares proposed to be sold). The Company shall give written notice to the Employee as to whether such offer has been accepted in whole by the Company within sixty days
after its receipt of written notice from the Employee. The Company may only accept such offer in whole and may not accept such offer in part. Such acceptance notice shall fix a time, location and date for the closing on such purchase (“Closing
Date”) which shall not be less than ten nor more than sixty days after the giving of the acceptance notice. The place for such closing shall be at the Company’s principal office. At such closing, the Employee shall accept payment as set
forth herein and shall deliver to the Company in exchange therefor certificates for the number of Shares stated in the notice accompanied by duly executed instruments of transfer. 

 

	 	(iii)	 If the Company shall fail to accept any such offer, the Employee shall be free to sell all, but not less than all, of the Shares set forth in his or
her notice to the designated transferee at the price and terms designated in the Employee’s notice, provided that (i) such sale is consummated within six months after the giving of notice by the Employee to the Company as aforesaid, and
(ii) the transferee first agrees in writing to be bound by the provisions of this Section 12 so that such transferee (and all subsequent 

  
 B-8

	 	
transferees) shall thereafter only be permitted to sell or transfer the Shares in accordance with the terms hereof. After the expiration of such six months, the provisions of this
Section 12.3 shall again apply with respect to any proposed voluntary transfer of the Employee’s Shares. 

  

	 	(iv)	The restrictions on transfer contained in this Section 12.3 shall not apply to (a) transfers by the Employee to his or her spouse or children or to a trust
for the benefit of his or her spouse or children, (b) transfers by the Employee to his or her guardian or conservator, and (c) or transfers by the Employee, in the event of his or her death, to his or her executor(s) or administrator(s) or
to trustee(s) under his or her will (collectively, “Permitted Transferees”); provided however, that in any such event the Shares so transferred in the hands of each such Permitted Transferee shall remain subject to this Agreement, and each
such Permitted Transferee shall so acknowledge in writing as a condition precedent to the effectiveness of such transfer. 

  

	 	(v)	The provisions of this Section 12.3 may be waived by the Company. Any such waiver may be unconditional or based upon such conditions as the Company may impose.

 12.4 In the event that the Employee or his or her successor in interest fails to deliver the Shares to be
repurchased by the Company under this Agreement, the Company may elect (a) to establish a segregated account in the amount of the repurchase price, such account to be turned over to the Employee or his or her successor in interest upon delivery
of such Shares, and (b) immediately to take such action as is appropriate to transfer record title of such Shares from the Employee to the Company and to treat the Employee and such Shares in all respects as if delivery of such Shares had been
made as required by this Agreement. The Employee hereby irrevocably grants the Company a power of attorney which shall be coupled with an interest for the purpose of effectuating the preceding sentence. 

12.5 If the Company shall pay a stock dividend or declare a stock split on or with respect to any of its Common Stock, or otherwise
distribute securities of the Company to the holders of its Common Stock, the number of shares of stock or other securities of the Company issued with respect to the shares then subject to the restrictions contained in this Agreement shall be added
to the Shares subject to the Company’s rights to repurchase pursuant to this Agreement. If the Company shall distribute to its stockholders shares of stock of another corporation, the shares of stock of such other corporation, distributed with
respect to the Shares then subject to the restrictions contained in this Agreement, shall be added to the Shares subject to the Company’s rights to repurchase pursuant to this Agreement. 

12.6 If the outstanding shares of Common Stock of the Company shall be subdivided into a greater number of shares or combined into a
smaller number of shares, or in the event of a reclassification of the outstanding shares of Common Stock of the Company, or if the Company shall be a party to a merger, consolidation or capital reorganization, there shall be

  
 B-9

 
substituted for the Shares then subject to the restrictions contained in this Agreement such amount and kind of securities as are issued in such subdivision, combination, reclassification,
merger, consolidation or capital reorganization in respect of the Shares subject immediately prior thereto to the Company’s rights to repurchase pursuant to this Agreement. 

12.7 The Company shall not be required to transfer any Shares on its books which shall have been sold, assigned or otherwise transferred
in violation of this Agreement, or to treat as owner of such Shares, or to accord the right to vote as such owner or to pay dividends to, any person or organization to which any such Shares shall have been so sold, assigned or otherwise transferred,
in violation of this Agreement. 
 12.8 The provisions of Sections 12.1, 12.2 and 12.3 shall terminate upon the effective date
of the registration of the Shares pursuant to the Securities Exchange Act of 1934. 
 12.9 If, in connection with a registration
statement filed by the Company pursuant to the 1933 Act, the Company or its underwriter so requests, the Employee will agree not to sell any Shares for a period not to exceed 180 days following the effectiveness of such registration. 

12.10 The Employee acknowledges and agrees that neither the Company, its shareholders nor its directors and officers, has any duty or
obligation to disclose to the Employee any material information regarding the business of the Company or affecting the value of the Shares before, at the time of, or following a termination of the employment of the Employee by the Company,
including, without limitation, any information concerning plans for the Company to make a public offering of its securities or to be acquired by or merged with or into another firm or entity. 

12.11 All certificates representing the Shares to be issued to the Employee pursuant to this Agreement shall have endorsed thereon a
legend substantially as follows: “The shares represented by this certificate are subject to restrictions set forth in a Incentive Stock Option Agreement dated
                    with this Company, a copy of which Agreement is available for inspection at the offices of the Company or will be made
available upon request.” 
  

	 	13.	NO OBLIGATION TO EMPLOY. 

The Company is not by the Plan or this Option obligated to continue the Employee as an employee of the Company or an Affiliate. The
Employee acknowledges: (i) that the Plan is discretionary in nature and may be suspended or terminated by the Company at any time; (ii) that the grant of the Option is a one-time benefit which does not create any contractual or other right
to receive future grants of options, or benefits in lieu of options; (iii) that all determinations with respect to any such future grants, including, but not limited to, the times when options shall be granted, the number of shares subject to
each option, the option price, and the time or times when each option shall be exercisable, will be at the sole discretion of the Company; (iv) that the Employee’s participation in the Plan is voluntary; (v) that the value of the
Option is an extraordinary item of compensation which is outside the scope of the Employee’s employment contract, if any; and (vi) that the Option is not part of normal or expected compensation for purposes of calculating any severance,
resignation, redundancy, end of service payments, bonuses, long-service awards, pension or retirement benefits or similar payments. 

  
 B-10

	 	14.	OPTION IS INTENDED TO BE AN ISO. 

 The parties each intend that the Option be an ISO so that the Employee (or the Employee’s Survivors) may qualify for the favorable tax treatment provided to holders of Options that meet the standards
of Section 422 of the Code. Any provision of this Agreement or the Plan which conflicts with the Code so that this Option would not be deemed an ISO is null and void and any ambiguities shall be resolved so that the Option qualifies as an ISO.
Nonetheless, if the Option is determined not to be an ISO, the Employee understands that neither the Company nor any Affiliate is responsible to compensate him or her or otherwise make up for the treatment of the Option as a Non-qualified Option and
not as an ISO. The Employee should consult with the Employee’s own tax advisors regarding the tax effects of the Option and the requirements necessary to obtain favorable tax treatment under Section 422 of the Code, including, but not
limited to, holding period requirements. 
  

	 	15.	NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION. 

 The Employee agrees to notify the Company in writing immediately after the Employee makes a Disqualifying Disposition of any of the Shares acquired pursuant to the exercise of the Option. A Disqualifying
Disposition is defined in Section 424(c) of the Code and includes any disposition (including any sale) of such Shares before the later of (a) two years after the date the Employee was granted the Option or (b) one year after the date
the Employee acquired Shares by exercising the Option, except as otherwise provided in Section 424(c) of the Code. If the Employee has died before the Shares are sold, these holding period requirements do not apply and no Disqualifying
Disposition can occur thereafter. 
  

	 	16.	NOTICES. 

 Any notices
required or permitted by the terms of this Agreement or the Plan shall be given by recognized courier service, facsimile, registered or certified mail, return receipt requested, addressed as follows: 

 

					
	 	  	If to the Company:	  	 President
 Genetix
Pharmaceuticals Inc.
 840 Memorial Drive, 5th floor
 Cambridge, MA 02139

			
		  	If to the Employee:	  	At the address set forth on the first page of this Agreement.

 or to such other address or addresses of which notice in the same manner has previously been given. Any such notice shall
be deemed to have been given upon the earlier of receipt, one business day following delivery to a recognized courier service or three business days following mailing by registered or certified mail. 

  
 B-11

	 	17.	GOVERNING LAW. 

 This
Agreement shall be construed and enforced in accordance with the law of the State of Delaware, without giving effect to the conflict of law principles thereof. For the purpose of litigating any dispute that arises under this Agreement, the parties
hereby consent to exclusive jurisdiction in Massachusetts and agree that such litigation shall be conducted in the courts of Middlesex County, Massachusetts or the federal courts of the United States for the District of Massachusetts, sitting in
Boston, Massachusetts. 
  

	 	18.	BENEFIT OF AGREEMENT. 

Subject to the provisions of the Plan and the other provisions hereof, this Agreement shall be for the benefit of and shall be binding
upon the heirs, executors, administrators, successors and assigns of the parties hereto. 
  

	 	19.	ENTIRE AGREEMENT. 

 This
Agreement, together with the Plan, embodies the entire agreement and understanding between the parties hereto with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject
matter hereof. No statement, representation, warranty, covenant or agreement not expressly set forth in this Agreement shall affect or be used to interpret, change or restrict, the express terms and provisions of this Agreement, provided, however,
in any event, this Agreement shall be subject to and governed by the Plan. 
  

	 	20.	MODIFICATIONS AND AMENDMENTS. 

 The terms and provisions of this Agreement may be modified or amended as provided in the Plan. 
  

	 	21.	WAIVERS AND CONSENTS. 

Except as provided in the Plan, the terms and provisions of this Agreement may be waived, or consent for the departure therefrom granted,
only by written document executed by the party entitled to the benefits of such terms or provisions. No such waiver or consent shall be deemed to be or shall constitute a waiver or consent with respect to any other terms or provisions of this
Agreement, whether or not similar. Each such waiver or consent shall be effective only in the specific instance and for the purpose for which it was given, and shall not constitute a continuing waiver or consent. 

 

	 	22.	DATA PRIVACY. 

 By
entering into this Agreement, the Employee: (i) authorizes the Company and each Affiliate, and any agent of the Company or any Affiliate administering the Plan or providing Plan record keeping services, to disclose to the Company or any of its
Affiliates such information and data as the Company or any such Affiliate shall request in order to facilitate the grant of options and the administration of the Plan; (ii) waives any data privacy rights he or she may have with respect to such
information; and (iii) authorizes the Company and each Affiliate to store and transmit such information in electronic form. 

  
 B-12

	 	23.	CONSENT OF SPOUSE. 

 If
the Employee is married as of the date of this Agreement, the Employee’s spouse shall execute a Consent of Spouse in the form of Exhibit B hereto, effective as of the date hereof. Such consent shall not be deemed to confer or convey to
the spouse any rights in the Shares that do not otherwise exist by operation of law or the agreement of the parties. If the Employee marries or remarries subsequent to the date hereof, the Employee shall, not later than 60 days thereafter, obtain
his or her new spouse’s acknowledgement of and consent to the existence and binding effect of Section 12.2 of this Agreement by such spouse’s executing and delivering a Consent of Spouse in the form of Exhibit B. 

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK] 

  
 B-13

 IN WITNESS WHEREOF, the Company has caused this Incentive Stock Option Agreement to be
executed by its duly authorized officer, and the Employee has hereunto set his or her hand, all as of the day and year first above written. 
  

			
	GENETIX PHARMACEUTICALS INC.
		
	By:	 	 
		 	 Name:

Title:

 
	
	
	  
	Employee Name:

  
 B-14

 Exhibit A 

NOTICE OF EXERCISE OF INCENTIVE STOCK OPTION 

[Form for Unregistered Shares] 

 

	To:	Genetix Pharmaceuticals Inc. 

 Ladies and
Gentlemen: 
 I hereby exercise my Incentive Stock Option to purchase
                shares (the “Shares”) of the common stock, $0.01 par value, of Genetix Pharmaceuticals Inc. (the “Company”), at the exercise
price of $                per share, pursuant to and subject to the terms of that certain Incentive Stock Option Agreement between the undersigned and the Company
dated                 , 20__. 
 I am
aware that the Shares have not been registered under the Securities Act of 1933, as amended (the “1933 Act”), or any state securities laws. I understand that the reliance by the Company on exemptions under the 1933 Act is predicated in
part upon the truth and accuracy of the statements by me in this Notice of Exercise. 
 I hereby represent and warrant that
(1) I have been furnished with all information which I deem necessary to evaluate the merits and risks of the purchase of the Shares; (2) I have had the opportunity to ask questions concerning the Shares and the Company and all questions
posed have been answered to my satisfaction; (3) I have been given the opportunity to obtain any additional information I deem necessary to verify the accuracy of any information obtained concerning the Shares and the Company; and (4) I
have such knowledge and experience in financial and business matters that I am able to evaluate the merits and risks of purchasing the Shares and to make an informed investment decision relating thereto. 

I hereby represent and warrant that I am purchasing the Shares for my own personal account for investment and not with a view to the sale
or distribution of all or any part of the Shares. 
 I understand that because the Shares have not been registered under the
1933 Act, I must continue to bear the economic risk of the investment for an indefinite time and the Shares cannot be sold unless the Shares are subsequently registered under applicable federal and state securities laws or an exemption from such
registration requirements is available. 
 I agree that I will in no event sell or distribute or otherwise dispose of all or any
part of the Shares unless (1) there is an effective registration statement under the 1933 Act and applicable state securities laws covering any such transaction involving the Shares or (2) the Company receives an opinion of my legal
counsel (concurred in by legal counsel for the Company) stating that such transaction is exempt from registration or the Company otherwise satisfies itself that such transaction is exempt from registration. 

 I consent to the placing of a legend on my certificate for the Shares stating that the
Shares have not been registered and setting forth the restriction on transfer contemplated hereby and to the placing of a stop transfer order on the books of the Company and with any transfer agents against the Shares until the Shares may be legally
resold or distributed without restriction. 
 I understand that at the present time Rule 144 of the Securities and Exchange
Commission (the “SEC”) may not be relied on for the resale or distribution of the Shares by me. I understand that the Company has no obligation to me to register the sale of the Shares with the SEC and has not represented to me that it
will register the sale of the Shares. 
 I understand the terms and restrictions on the right to dispose of the Shares set forth
in the 2002 Employee, Director and Consultant Stock Plan and the Incentive Stock Option Agreement, both of which I have carefully reviewed. I consent to the placing of a legend on my certificate for the Shares referring to such restriction and the
placing of stop transfer orders until the Shares may be transferred in accordance with the terms of such restrictions. 
 I have
considered the Federal, state and local income tax implications of the exercise of my Option and the purchase and subsequent sale of the Shares. 
 I am paying the option exercise price for the Shares as follows: 
  

 
 Please issue the stock
certificate for the Shares (check one): 
  

	 	 ̈	to me; or 

  

	 	 ̈	to me and                     , as joint tenants with right
of survivorship and mail the certificate to me at the following address: 

  

 
  

 
  

 

 My mailing address for shareholder communications, if different from the address listed
above is: 
  
  

 
  

 
  

 

	
	 Very truly yours.
  

	 Employee (signature)
  

	 Print Name

 

	 Date

 

	Social Security Number

 Exhibit A 

[Form for Registered Shares] 
 NOTICE OF EXERCISE OF INCENTIVE STOCK OPTION 
  

	TO:	Genetix Pharmaceuticals Inc. 

IMPORTANT NOTICE: This form of Notice of Exercise may only be used at such time as the Company has filed a Registration Statement with the Securities and
Exchange Commission under which the issuance of the Shares for which this exercise is being made is registered and such Registration Statement remains effective. 
 Ladies and Gentlemen: 
 I hereby exercise my Incentive Stock Option to purchase
                 shares (the “Shares”) of the common stock, $0.01 par value, of Genetix Pharmaceuticals Inc. (the “Company”), at the exercise
price of $                 per share, pursuant to and subject to the terms of that certain Incentive Stock Option Agreement between the undersigned and the
Company dated                 , 20__. 

I understand the nature of the investment I am making and the financial risks thereof. I am aware that it is my responsibility to have
consulted with competent tax and legal advisors about the relevant national, state and local income tax and securities laws affecting the exercise of the Option and the purchase and subsequent sale of the Shares. 

I am paying the option exercise price for the Shares as follows: 
 Please issue the Shares (check one): 
  

	 	 ̈	to me; or 

  

	 	 ̈	to me and                     , as joint tenants with right
of survivorship 

 at the following address: 
  

 
  

 
  

 

 My mailing address for shareholder communications, if different from the address listed
above is: 
  

	
	 Very truly yours.
  

	 Employee (signature)
  

	 Print Name

 

	 Date

 

	Social Security Number

 Exhibit B 

CONSENT OF SPOUSE 
 I,                         , spouse of
                        , acknowledge that I have read the Incentive Stock Option Agreement dated as of
                , 20         (the “Agreement”) to which this Consent is attached as Exhibit B and
that I know its contents. Capitalized terms used and not defined herein shall have the meanings assigned to such terms in the Agreement. I am aware that by its provisions the Shares granted to my spouse pursuant to the Agreement are subject to a
right of repurchase in favor of Genetix Pharmaceuticals Inc. (the “Company”) and that, accordingly, the Company has the right to repurchase up to all of the Shares of which I may become possessed as a result of a gift from my spouse or a
court decree and/or any property settlement in any domestic litigation. 
 I hereby agree that my interest, if any, in the
Shares subject to the Agreement shall be irrevocably bound by the Agreement and further understand and agree that any community property interest I may have in the Shares shall be similarly bound by the Agreement. 

I agree to the repurchase right described in Section 12.2 of the Agreement and I hereby consent to the repurchase of the Shares by
the Company and the sale of the Shares by my spouse or my spouse’s legal representative in accordance with the provisions of the Agreement. Further, as part of the consideration for the Agreement, I agree that at my death, if I have not
disposed of any interest of mine in the Shares by an outright bequest of the Shares to my spouse, then the Company shall have the same rights against my legal representative to exercise its rights of repurchase with respect to any interest of mine
in the Shares as it would have had pursuant to the Agreement if I had acquired the Shares pursuant to a court decree in domestic litigation. 
 I AM AWARE THAT THE LEGAL, FINANCIAL AND RELATED MATTERS CONTAINED IN THE AGREEMENT ARE COMPLEX AND THAT I AM FREE TO SEEK INDEPENDENT PROFESSIONAL GUIDANCE OR COUNSEL WITH RESPECT TO THIS CONSENT. I HAVE
EITHER SOUGHT SUCH GUIDANCE OR COUNSEL OR DETERMINED AFTER REVIEWING THE AGREEMENT CAREFULLY THAT I WILL WAIVE SUCH RIGHT. 

Dated as of the              day of
                    , 20        . 

	
	
	  
	Print name:

 Exhibit C 

RESTRICTED STOCK AGREEMENT 
 GENETIX PHARMACEUTICALS INC. 
 AGREEMENT made as of the
            day of                 , 200_ (the “Grant Date”), between Genetix
Pharmaceuticals Inc. (the “Company”), a Delaware corporation having its principal place of business in Cambridge, Massachusetts, and
                    of
                    , (the “Employee”). 
 WHEREAS, the Company has adopted the Genetix Pharmaceuticals Inc. 2002 Employee, Director and Consultant Stock Plan (the “Plan”) to promote the interests of the Company by
providing an incentive for employees, directors and consultants of the Company or its Affiliates; 
 WHEREAS, the parties
hereto understand and agree that any terms used and not defined herein have the meanings ascribed to such terms in the Plan and that any and all references herein to employment of the Employee by the Company shall include the Employee’s
employment of the Company or any Affiliate; 
 WHEREAS, pursuant to the exercise of an option granted to the Employee
pursuant to a Incentive Stock Option Agreement dated                 by and between the Company and the Employee issued under the Plan (the “Option
Agreement”), which Option Agreement and Plan are hereby incorporated herein by reference, the Employee has elected to purchase                 shares of
the Company’s common stock, $.001 par value per share (“Common Stock”), which have not become vested under the vesting schedule set forth in the Option Agreement (the “Unvested Shares”). The Unvested Shares and
the Shares subject to the Option Agreement that have become vested are sometimes collectively referred to herein as the “Shares.” 
 WHEREAS, as required by the Option Agreement, as a condition to the Employee’s election to exercise the option, the Employee must execute this Agreement, which sets forth the rights and
obligations of the parties with respect to the Unvested Shares acquired upon exercise of the option pursuant to the Option Agreement; and 
 WHEREAS, Employee wishes to accept said offer in accordance with the provisions of the Plan, all on the terms and conditions hereinafter set forth. 

NOW, THEREFORE, in consideration of the premises and the mutual covenants contained herein and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto hereby agree as follows: 
  

	 	1.	Company’s Lapsing Repurchase Right. 

 (a) Lapsing Repurchase Right. Except as set forth in Subsection 1(b) hereof, in the event that for any reason the Employee no longer is an employee of the Company, the Company (or its
designee) shall have the option, but not the obligation, to purchase from the Employee (or the Employee’s Survivor), and, in the event the Company exercises such option, 

  
 C-1

 
the Employee (or the Employee’s Survivor) shall be obligated to sell to the Company (or its designee), at a price per share equal to the Purchase Price, all or any part of the Unvested
Shares determined as of the date of such termination of employment (the “Lapsing Repurchase Right”). The Lapsing Repurchase Right with respect to the Unvested Shares shall terminate as to such Unvested Shares in accordance with the
vesting schedule set forth in Section 3 of the Option Agreement. The Company’s Lapsing Repurchase Right shall be valid for a period of one year commencing with the date of such termination of employment or service. Notwithstanding any
other provision hereof, in the event the Company is prohibited during such one year period from exercising its Lapsing Repurchase Right by applicable law, then the time period during which such Lapsing Repurchase Right may be exercised shall be
extended until 30 days after the Company is first not so prohibited. 
 (b) Effect of Termination for
Cause. Notwithstanding anything to the contrary contained in this Agreement, in the event the Company terminates the Employee’s employment for “cause” (as defined in the Plan) or in the event the Administrator determines,
within 90 days after the Employee’s termination, that either prior or subsequent to the Employee’s termination the Employee engaged in conduct that would constitute “cause,” the Company shall have the option to repurchase all of
the Unvested Shares acquired by the Employee hereunder at the Purchase Price irrespective of whether the Lapsing Repurchase Right has lapsed in accordance with the vesting schedule set forth in Section 3 of the Option Agreement. 

(c) Effect of Termination for Disability or upon Death. Except as otherwise provided in Subsection 1(b) above,
the following rules apply if the Employee ceases to be an employee of the Company by reason of Disability or death: to the extent the Company’s Lapsing Repurchase Right has not lapsed as of the date of Disability or death, as case may be, the
Company may exercise such Lapsing Repurchase Right; provided, however, that the Company’s Lapsing Repurchase Right shall be deemed to have lapsed to the extent of a pro rata portion of the Unvested Shares through the date of Disability or
death, as would have lapsed had the Employee not become Disabled or died, as the case may be. The proration shall be based upon the number of days accrued in such current vesting period prior to the Employee’s date of Disability or death, as
the case may be. 
 (d) Closing. In the event that the Company exercises the Lapsing Repurchase Right, the
Company shall notify the Employee, or, in the case of the Employee’s death, his or her Survivor, in writing of its intent to repurchase the Unvested Shares. Such notice may be mailed by the Company up to and including the last day of the time
period provided for above for exercise of the Lapsing Repurchase Right. The notice shall specify the place, time and date for payment of the repurchase price (the “Closing”) and the number of Unvested Shares with respect to which
the Company is exercising the Lapsing Repurchase Right. The Closing shall be not less than ten days nor 

  
 C-2

 
more than 60 days from the date of mailing of the notice, and the Employee or the Employee’s Survivor with respect to the Unvested Shares which the Company elects to repurchase shall have no
further rights as the owner thereof from and after the date specified in the notice. At the Closing, the repurchase price shall be delivered to the Employee or the Employee’s Survivor and the Unvested Shares being repurchased, duly endorsed for
transfer, shall, to the extent that they are not then in the possession of the Company, be delivered to the Company by the Employee or the Employee’s Survivor. 

(e) Escrow. The certificates representing all Unvested Shares acquired by the Employee hereunder which from time to
time are subject to the Lapsing Repurchase Right shall be delivered to the Company and the Company shall hold such Unvested Shares in escrow as provided in this Subsection 1(e). Promptly following receipt by the Company of a written request
from the Employee, the Company shall release from escrow and deliver to the Employee a certificate for the whole number of Unvested Shares, if any, as to which the Company’s Lapsing Repurchase Right has lapsed. In the event of a repurchase by
the Company of Unvested Shares subject to the Lapsing Repurchase Right, the Company shall release from escrow and cancel a certificate for the number of Unvested Shares so repurchased. Any securities distributed in respect of the Unvested Shares
held in escrow, including, without limitation, shares issued as a result of stock splits, stock dividends or other recapitalizations, shall also be held in escrow in the same manner as the Unvested Shares. 

(f) Prohibition on Transfer. The Employee recognizes and agrees that all Unvested Shares which are subject to the
Lapsing Repurchase Right may not be sold, transferred, assigned, hypothecated, pledged, encumbered or otherwise disposed of, whether voluntarily or by operation of law, other than to the Company (or its designee). However, the Employee, with the
approval of the Administrator, may transfer the Unvested Shares for no consideration to or for the benefit of the Employee’s Immediate Family (including, without limitation, to a trust for the benefit of the Employee’s Immediate Family or
to a partnership or limited liability company for one or more members of the Employee’s Immediate Family), subject to such limits as the Administrator may establish, and the transferee shall remain subject to all the terms and conditions
applicable to this Agreement prior to such transfer and each such transferee shall so acknowledge in writing as a condition precedent to the effectiveness of such transfer. The term “Immediate Family” shall mean the Employee’s
spouse, former spouse, parents, children, stepchildren, adoptive relationships, sisters, brothers, nieces and nephews and grandchildren (and, for this purpose, shall also include the Employee. The Company shall not be required to transfer any
Unvested Shares on its books which shall have been sold, assigned or otherwise transferred in violation of this Subsection 1(f), or to treat as the owner of such Unvested Shares, or to accord the right to vote as such owner or to pay dividends
to, any person or organization to which any such Unvested Shares shall have been so sold, 

  
 C-3

 
assigned or otherwise transferred, in violation of this Subsection 1(f). The Employee further recognizes and agrees that all Shares remain subject to Section 12 of the Option Agreement,
except that with respect to the Unvested Shares subject to the Lapsing Repurchase Right, this Agreement will supercede Section 12.2 of the Option Agreement. 

(g) Failure to Deliver Unvested Shares to be Repurchased. In the event that the Unvested Shares to be repurchased
by the Company under this Agreement are not in the Company’s possession pursuant to Subsection 1(e) above or otherwise and the Employee or the Employee’s Survivor fails to deliver such Unvested Shares to the Company (or its designee),
the Company may elect (i) to establish a segregated account in the amount of the repurchase price, such account to be turned over to the Employee or the Employee’s Survivor upon delivery of such Unvested Shares, and (ii) immediately
to take such action as is appropriate to transfer record title of such Unvested Shares from the Employee to the Company (or its designee) and to treat the Employee and such Unvested Shares in all respects as if delivery of such Unvested Shares had
been made as required by this Agreement. The Employee hereby irrevocably grants the Company a power of attorney which shall be coupled with an interest for the purpose of effectuating the preceding sentence. 

(h) Additional Securities. If the Company shall pay a stock dividend or declare a stock split on or with respect to
any of its Common Stock, or otherwise distribute securities of the Company to the holders of its Common Stock, the number of shares of stock or other securities of the Company issued with respect to the Unvested Shares then subject to the
restrictions contained in this Agreement shall be added to the Unvested Shares subject to the Company’s rights of repurchase pursuant to this Agreement. If the Company shall distribute to its stockholders securities of another corporation, the
securities of such other corporation, distributed with respect to the Unvested Shares then subject to the restrictions contained in this Agreement, shall be added to the Unvested Shares subject to the Company’s rights of repurchase pursuant to
this Agreement. 
 If the outstanding shares of the Company’s Common Stock shall be subdivided into a greater number of
shares or combined into a smaller number of shares, or in the event of a reclassification of the outstanding shares of the Company’s Common Stock, or if the Company shall be a party to a merger, consolidation or capital reorganization, there
shall be substituted for the Unvested Shares then subject to the restrictions contained in this Agreement such amount and kind of securities as are issued in such subdivision, combination, reclassification, merger, consolidation or capital
reorganization in respect of the Unvested Shares subject immediately prior thereto to the Company’s rights of repurchase pursuant to this Agreement. 

  
 C-4

 2. Legend. In addition to any legend required pursuant to the Plan, all certificates
representing the Unvested Shares to be issued to the Employee pursuant to this Agreement shall have endorsed thereon a legend substantially as follows: 
 “The shares represented by this certificate are subject to restrictions set forth in a Restricted Stock Agreement dated as of
                , 200_ with this Company, a copy of which Agreement is available for inspection at the offices of the Company or will be made available upon
request.” 
 3. Purchase for Investment. If the offering and sale of the Unvested Shares have not been effectively
registered under the Securities Act of 1933, as amended, the Employee hereby represents and warrants that he or she is acquiring the Unvested Shares for his or her own account, for investment, and not with a view to, or for sale in connection with,
the distribution of any such Unvested Shares. 
 4. Provisions of Agreement Controlling. The Employee specifically
understands and agrees that the Unvested Shares issued under the Plan are being sold to the Employee pursuant to the Plan and the Option Agreement, a copy of which Plan and Option Agreement the Employee acknowledges he or she has read and
understands and by which Plan and Option Agreement he or she agrees to be bound. The provisions of the Plan and the Option Agreement are incorporated herein by reference. In the event of a conflict between the terms and conditions of the Plan, this
Agreement and the Option Agreement, the provisions of this Agreement will control. 
 5. Tax Liability of the Employee and
Payment of Taxes. The Employee acknowledges and agrees that any income or other taxes due from the Employee with respect to the Unvested Shares issued pursuant to this Agreement, including, without limitation, the Lapsing Repurchase Right, shall
be the Employee’s responsibility. Without limiting the foregoing, the Employee agrees that, to the extent that the lapsing of restrictions on disposition of any of the Unvested Shares or the declaration of dividends on any such shares before
the lapse of such restrictions on disposition results in the Employee’s being deemed to be in receipt of earned income under the provisions of the Code, the Company shall be entitled to immediate payment from the Employee of the amount of any
tax required to be withheld by the Company. 
 Upon execution of this Agreement, the Employee may file an election under
Section 83 of the Code in substantially the form attached as Attachment I. The Employee acknowledges that if she does not file such an election within 30 days of the date of this Agreement, as the Unvested Shares are released from
the Lapsing Repurchase Right in accordance with Section 1, the Employee will have income for tax purposes equal to the fair market value of the Unvested Shares at such date, less the price paid for the Unvested Shares by the Employee.

 6. Securities Law Compliance. The Employee specifically acknowledges and agrees that any sales of Unvested Shares
shall be made in accordance with the requirements of the Securities Act of 1933, as amended, in a transaction as to which the Company shall have received an opinion of counsel satisfactory to it confirming such compliance. 

7. Equitable Relief. The Employee specifically acknowledges and agrees that in the event of a breach or threatened breach of the
provisions of this Agreement, the Option Agreement or the Plan, including the attempted transfer of the Unvested Shares by the Employee in violation of this Agreement or the Option Agreement, monetary damages may not be adequate

  
 C-5

 
to compensate the Company, and, therefore, in the event of such a breach or threatened breach, in addition to any right to damages, the Company shall be entitled to equitable relief in any court
having competent jurisdiction. Nothing herein shall be construed as prohibiting the Company from pursuing any other remedies available to it for any such breach or threatened breach. 

8. No Obligation to Employ. The Company is not by the Plan, the Option Agreement or this Agreement obligated to continue the
Employee as an employee of the Company or an Affiliate. 
 9. Notices. Any notices required or permitted by the terms of
this Agreement, the Option Agreement or the Plan shall be given by recognized courier service, facsimile, registered or certified mail, return receipt requested, addressed as follows: 

 

					
		 	If to the Company:	  	 President
 Genetix
Pharmaceuticals Inc.
 840 Memorial Drive, 5th floor

Cambridge, MA 02139

			
		 	If to the Employee:	  	At the address set forth on the first page of this Agreement

 or to such other address or addresses of which notice in the same manner has previously been given. Any such notice shall
be deemed to have been given on the earliest of receipt, one business day following delivery by the sender to a recognized courier service, or three business days following mailing by registered or certified mail. 

10. Binding Effect. This Agreement shall be for the benefit of and shall be binding upon the parties hereto, upon their respective
successors and assigns and upon the Employee’s heirs, executors, administrators. 
 11. Governing Law. This
Agreement shall be construed and enforced in accordance with the law of the State of Delaware, without giving effect to the conflict of law principles thereof. For the purpose of litigating any dispute that arises under this Agreement, the parties
hereby consent to exclusive jurisdiction in Massachusetts and agree that such litigation shall be conducted in the courts of Middlesex County, Massachusetts or the federal courts of the United States for the District of Massachusetts, sitting in
Boston, Massachusetts. 
 12. Severability. If any provision of this Agreement is held to be invalid or unenforceable by
a court of competent jurisdiction, then such provision or provisions shall be modified to the extent necessary to make such provision valid and enforceable, and to the extent that this is impossible, then such provision shall be deemed to be excised
from this Agreement, and the validity, legality and enforceability of the rest of this Agreement shall not be affected thereby. 

13. Entire Agreement. This Agreement, together with the Plan and the Option Agreement, constitutes the entire agreement and
understanding between the parties hereto with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject matter hereof. No statement, representation, warranty, covenant or
agreement not expressly set forth in this Agreement, the Option Agreement or the Plan shall affect or be used to interpret, change or restrict the express terms and provisions of this Agreement provided, however, in any event, this Agreement shall
be subject to and governed by the Plan. 

  
 C-6

 14. Modifications and Amendments; Waivers and Consents. The terms and provisions of
this Agreement may be modified or amended as provided in the Plan. Except as provided in the Plan, the terms and provisions of this Agreement may be waived, or consent for the departure therefrom granted, only by written document executed by the
party entitled to the benefits of such terms or provisions. No such waiver or consent shall be deemed to be or shall constitute a waiver or consent with respect to any other terms or provisions of this Agreement, whether or not similar. Each such
waiver or consent shall be effective only in the specific instance and for the purpose for which it was given, and shall not constitute a continuing waiver or consent. 
 15. Consent of Spouse. If the Employee is married as of the date of this Agreement, the Employee’s spouse shall execute a Consent of Spouse in the form of Attachment II hereto,
effective as of the date hereof. Such consent shall not be deemed to confer or convey to the spouse any rights in the Unvested Shares that do not otherwise exist by operation of law or the agreement of the parties. If the Employee marries or
remarries subsequent to the date hereof, the Employee shall, not later than 60 days thereafter, obtain his or her new spouse’s acknowledgement of and consent to the existence and binding effect of all restrictions contained in this Agreement by
such spouse’s executing and delivering a Consent of Spouse in the form of Exhibit A. 
 16.
Counterparts. This Agreement may be executed in one or more counterparts, and by different parties hereto on separate counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same
instrument. 
 [THE NEXT PAGE IS THE SIGNATURE PAGE] 

  
 C-7

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

			
	GENETIX PHARMACEUTICALS INC.
		
	By:	 	 
	Name:	 	
	Title:	 	

 
	
	
	EMPLOYEE:
	
	  
	Print name:

  
 C-8

 Attachment I 
 Election to Include Gross Income in Year 
 of Transfer Pursuant to
Section 83(b) 
 of the Internal Revenue Code of 1986, as amended 

In accordance with Section 83(b) of the Internal Revenue Code of 1986, as amended (the “Code”), the undersigned
hereby elects to include in his gross income as compensation for services the excess, if any, of the fair market value of the property (described below) at the time of transfer over the amount paid for such property. 

The following sets for the information required in accordance with the Code and the regulations promulgated hereunder: 

 

	1.	The name, address and social security number of the undersigned are: 

 Name: 
 Address: 

Social Security No.: 
  

	2.	The description of the property with respect to which the election is being made is as follows: 

 

	            (            
)	shares (the “Shares”) of Common Stock, $.001 par value per share, of Genetix Pharmaceuticals Inc., a Delaware corporation (the
“Company”). 

  

	3.	This election is made for the calendar year             , with respect to the transfer of the
property to the Taxpayer on                 . 

  

	4.	Description of restrictions: The property is subject to the following restrictions: 

In the event taxpayer’s employment with the Company or an Affiliate is terminated, the Company may repurchase all or any portion of
the Shares determined as set forth below at the acquisition price paid by the taxpayer: 
  

	 	A.	If the termination takes place on or prior to             , the Purchase Option will apply to all of
the Shares. 

  

	 	B.	If the termination takes place after                     ,
200_, the number of Shares to which the Purchase Option applies shall be
                    (            ) Shares less
                    (        ) Shares for each month elapsed after
                    , 200_ if the taxpayer is employed by the Company or an Affiliate. 

 

	5.	The fair market value at time of transfer (determined without regard to any restrictions other than restrictions which by their terms will never lapse) of the property
with respect to which this election is being made was not more than $             per Share. 

 

	6.	The amount paid by taxpayer for said property was $             per Share. 

  
 I-1

	7.	A copy of this statement has been furnished to the Company. 

 Signed this             day of
                    , 200_. 
  

	
	
	  
	Print name:

  
 I-2

 Attachment II 
 CONSENT OF SPOUSE 
 I,
                    , spouse of
                    , acknowledge that I have read the RESTRICTED STOCK AGREEMENT dated as of
                , 200_ (the “Agreement”) to which this Consent is attached as Attachment II and that I know its contents. Capitalized
terms used and not defined herein shall have the meanings assigned to such terms in the Agreement. I am aware that by its provisions the Unvested Shares granted to my spouse pursuant to the Agreement are subject to a Lapsing Repurchase Right in
favor of Genetix Pharmaceuticals Inc. (the “Company”) and that, accordingly, the Company has the right to repurchase up to all of the Unvested Shares of which I may become possessed as a result of a gift from my spouse or a court
decree and/or any property settlement in any domestic litigation. 
 I hereby agree that my interest, if any, in the Unvested
Shares subject to the Agreement shall be irrevocably bound by the Agreement and further understand and agree that any community property interest I may have in the Invested Shares shall be similarly bound by the Agreement. 

I agree to the Lapsing Repurchase Right described in the Agreement and I hereby consent to the repurchase of the Unvested Shares by the
Company and the sale of the Unvested Shares by my spouse or my spouse’s legal representative in accordance with the provisions of the Agreement. Further, as part of the consideration for the Agreement, I agree that at my death, if I have not
disposed of any interest of mine in the Unvested Shares by an outright bequest of the Unvested Shares to my spouse, then the Company shall have the same rights against my legal representative to exercise its rights of repurchase with respect to any
interest of mine in the Unvested Shares as it would have had pursuant to the Agreement if I had acquired the Unvested Shares pursuant to a court decree in domestic litigation. 
 I AM AWARE THAT THE LEGAL, FINANCIAL AND RELATED MATTERS CONTAINED IN THE AGREEMENT ARE COMPLEX AND THAT I AM FREE TO SEEK INDEPENDENT PROFESSIONAL GUIDANCE OR COUNSEL WITH RESPECT TO THIS CONSENT. I HAVE
EITHER SOUGHT SUCH GUIDANCE OR COUNSEL OR DETERMINED AFTER REVIEWING THE AGREEMENT CAREFULLY THAT I WILL WAIVE SUCH RIGHT. 

Dated as of the             day of
                    , 200_. 

	
	  
	Print name:EX-10.2

 Exhibit 10.2 
 BLUEBIRD BIO, INC. 
 FOURTH AMENDMENT TO THE 

2010 STOCK OPTION AND GRANT PLAN 
 The bluebird bio, Inc. 2010 Stock Option and Grant Plan (the “Plan”) is hereby amended by the Board of Directors and stockholders of bluebird bio, Inc., a Delaware corporation, as
follows: 
 Section 3(a) of the Plan is hereby amended by deleting the first sentence of Section 3(a) and substituting
therefor the following: 
 “The maximum number of shares of Stock reserved and available for issuance under the Plan shall
be the sum of (i) 81,953,382 shares and (ii) such number of shares as equals that number of stock options or awards returned to the Company’s 2002 Employee, Director and Consultant Stock Plan, as amended and in effect from time to
time, after January 16, 2013 as a result of the expiration, cancellation or termination of such stock options or awards, subject to adjustment as provided in Section 3(b).” 
 ADOPTED BY BOARD OF DIRECTORS: January 16, 2013 
 ADOPTED BY STOCKHOLDERS: January 16,
2013 

 BLUEBIRD BIO, INC. 

THIRD AMENDMENT TO THE 
 2010 STOCK OPTION AND GRANT PLAN 
 The bluebird bio, Inc. 2010 Stock Option
and Grant Plan (the “Plan”) is hereby amended by the Board of Directors and stockholders of bluebird bio, Inc., a Delaware corporation, as follows: 
 Section 3(a) of the Plan is hereby amended by deleting the first sentence of Section 3(a) and substituting therefor the following: 

“The maximum number of shares of Stock reserved and available for issuance under the Plan shall be the sum of (i) 65,322,771
shares and (ii) such number of shares as equals that number of stock options or awards returned to the Company’s 2002 Employee, Director and Consultant Stock Plan, as amended and in effect from time to time, after July 23, 2012 as a
result of the expiration, cancellation or termination of such stock options or awards, subject to adjustment as provided in Section 3(b).” 
 ADOPTED BY BOARD OF DIRECTORS: July 23, 2012 
 ADOPTED BY STOCKHOLDERS: July 23, 2012

 BLUEBIRD BIO, INC. 

SECOND AMENDMENT TO THE 
 2010 STOCK OPTION AND GRANT PLAN 
 The bluebird bio, Inc. 2010 Stock Option
and Grant Plan, as amended (the “Plan”), is hereby amended by the Board of Directors and stockholders of bluebird bio, Inc., a Delaware corporation, as follows: 

Section 3(a) of the Plan is hereby amended by deleting the first sentence of Section 3(a) and substituting therefor the following:

 “The maximum number of shares of Stock reserved and available for issuance under the Plan shall be the sum of
(i) 46,136,871 shares and (ii) such number of shares as equals that number of stock options or awards returned to the Company’s 2002 Employee, Director and Consultant Stock Plan, as amended and in effect from time to time, after the
Effective Date (September 10, 2010) as a result of the expiration, cancellation or termination of such stock options or awards, subject to adjustment as provided in Section 3(b).” 
 ADOPTED BY BOARD OF DIRECTORS: April 24, 2012 
 ADOPTED BY STOCKHOLDERS: May 7, 2012

 BLUEBIRD BIO, INC. 

FIRST AMENDMENT TO THE 
 2010 STOCK OPTION AND GRANT PLAN 
 The bluebird bio, Inc. 2010 Stock Option
and Grant Plan (the “Plan”) is hereby amended by the Board of Directors and stockholders of bluebird bio, Inc., a Delaware corporation, as follows: 
 Section 3(a) of the Plan is hereby amended by deleting the first sentence of Section 3(a) and substituting therefor the following: 

“The maximum number of shares of Stock reserved and available for issuance under the Plan shall be the sum of (i) 41,636,871
shares and (ii) such number of shares as equals that number of stock options or awards returned to the Company’s 2002 Employee, Director and Consultant Stock Plan, as amended and in effect from time to time, after the Effective Date as a
result of the expiration, cancellation or termination of such stock options or awards, subject to adjustment as provided in Section 3(b).” 
 ADOPTED BY BOARD OF DIRECTORS: April 15, 2011 
 ADOPTED BY STOCKHOLDERS: April 15, 2011

  

 BLUEBIRD BIO, INC. 

2010 STOCK OPTION AND GRANT PLAN 
 SECTION 1. GENERAL PURPOSE OF THE PLAN; DEFINITIONS 
 The name of the plan
is the bluebird bio, Inc. 2010 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 (including prospective employees, but
conditioned on their employment) of bluebird bio, Inc. (f/k/a Genetix Pharmaceuticals, Inc.), a Delaware corporation (including any successor entity, the “Company”) and any Subsidiary, 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, that except to the extent explicitly provided to the contrary, in the event of any conflict in the
terms of the Plan and the Award Agreement, the terms of the Plan shall govern. 
 “Bankruptcy” shall mean
(i) the filing of a voluntary petition under any bankruptcy or insolvency law, or a petition for the appointment of a receiver or the making of an assignment for the benefit of creditors, with respect to the Holder, (ii) the Holder being
subjected involuntarily to such a petition or assignment or to an attachment or other legal or equitable interest with respect to the Holder’ s assets, which involuntary petition or assignment or attachment is not discharged within 60 days
after its date, or (iii) the Holder being subject to a transfer of its Issued Shares or Award(s) by operation of law (including by divorce, even if not insolvent), except by reason of death. 

“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 

  
 1 

 
any of the Company’s 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 violation of any provision of any agreement(s) between the grantee and the Company relating to noncompetition, 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.

 “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. 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. 
 “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 Issued Shares,
the Person holding such Award or Issued Shares, including the initial recipient of the Award or any Permitted Transferee. 

“Incentive Stock Option” means any Stock Option designated and qualified as an “incentive stock option” as
defined in Section 422 of the Code. 

  
 2 

 “Incumbent Directors” shall mean directors who either (A) are
directors of the Company as of the date this Plan is first adopted by the Board, or (B) are elected, or nominated for election, to the Board with the affirmative votes of at least a majority of the Incumbent Directors at the time of such
election or nomination (but shall not include an individual whose election or nomination is in connection with an actual or threatened proxy contest relating to the election of directors to the Company). 

“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. 

“Issued Shares” means, collectively, all outstanding Shares issued pursuant to Restricted Stock Awards, Unrestricted
Stock Awards and Restricted Stock Units and all Option Shares. 
 “NASDAQ” means the NASDAQ Stock Market LLC.

 “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. 
 “Option Shares” means outstanding shares of Stock that were issued to a Holder upon the
exercise of a Stock Option. 
 “Permitted Transferees” shall mean any of the following to whom a Holder may
transfer Issued 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 Issued 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. 

“Repurchase Event” means (i) a Sale Event or (ii) the Holder’s Bankruptcy. 

“Restricted Stock Award” means Awards granted pursuant to Section 6 and “Restricted Stock” means
Shares granted pursuant to such Awards. 

  
 3 

 “Restricted Stock Unit” means an Award of phantom stock units to a grantee,
which may be settled in cash or stock 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 involving the Company in which the shares of voting stock of the Company outstanding immediately prior to such transaction represent or are converted into or exchanged for securities of the surviving or
resulting entity immediately upon completion of such transaction which represent less than 50 percent of the outstanding voting power of such surviving or resulting entity, (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, (v) a change in the composition of the Board, as a result of which fewer than a majority of the directors are Incumbent Directors,
or (vi) 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.” 
 “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; provided that a change in status (e.g., from full-time employee to part-time employee or from full-time employee to Consultant or otherwise) shall, unless otherwise
provided in the Award Agreement, constitute a termination of the Award recipient’s Service Relationship with the Company and its Subsidiaries. 
 “Shares” means shares of Stock. 
 “Stock” means
the Common Stock, par value $0.01 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 

  
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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 granted 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). 
 (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 of Stock to be covered by any Award and, subject to the provisions of Section 5(a)(i) below,
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 granted under the Plan, including limitations on transfers, repurchase provisions
and the like, and to exercise repurchase rights or obligations; 
 (vii) subject to any restrictions imposed by
Section 409A, to extend at any time the period in which Stock Options may be exercised; and 

  
 5 

 (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 related written instruments); 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 Plan grantees. 
 (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. 
 (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 of Stock reserved and available for issuance under the Plan shall be the sum of
(i) 26,436,861 shares and (ii) such number of shares as equals that number of stock options or awards returned to the Company’s 2002 Employee, Director and Consultant Stock Plan, as amended and in effect from time to time, after the
Effective Date as a result of the expiration, cancellation or termination of such stock options 

  
 6 

 
or awards, subject to adjustment as provided in Section 3(b). For purposes of this limitation, the shares of Stock underlying any Awards that are forfeited, canceled, withheld upon exercise
of an Option or settlement of an Award to cover the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or otherwise terminated (other than by exercise), in each case shall be added
back to the shares of Stock available for issuance under the Plan. Subject to such overall limitations, shares of Stock may be issued up to such maximum number pursuant to any type or types of Award. The shares available for issuance under the Plan
may be authorized but unissued shares of Stock or shares of Stock reacquired by the Company. 
 (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 of
Stock 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 of Stock or other securities, 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 of Stock are converted into or
exchanged for securities of the Company or any successor entity (or a parent or subsidiary thereof), the Committee shall make an appropriate and equitable or 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 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 of Stock 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 Options issued hereunder shall terminate upon the effective time of any such Sale Event unless provision is made in connection with the Sale Event for the assumption or continuation of Options
theretofore granted by the successor entity, or the substitution of such Options with new Options of the successor entity or parent thereof, 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). 

  
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 (B) In the event of the termination of the Plan and all Options issued
hereunder pursuant to Section 3(c), each Holder of Options shall be permitted, within a specified period of time prior to the consummation of the Sale Event as determined 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 grantees holding Options 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 of Stock subject to outstanding Options (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 Options. 
 (ii) Option Shares. Unless otherwise provided in an Award Agreement, in the case of and subject to the consummation of a Sale Event, Option Shares shall be subject to the repurchase right set forth
in Section 9(c)(i). 
 (iii) Restricted Stock and Restricted Stock Unit Awards. 

(A) In the case of and subject to the consummation of a Sale Event, all Restricted Stock and Restricted Stock Unit Awards
issued hereunder shall be forfeited immediately prior to the effective time of any such Sale Event unless provision is made in connection with the Sale Event for the assumption or continuation of such Awards by the successor entity, or the
substitution of such Awards with new Awards of the successor entity or parent thereof, 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). 
 (B) In the event of the
forfeiture of shares of Restricted Stock issued hereunder pursuant to Section 3(c)(iii)(A), such shares of Restricted Stock shall be repurchased from the Holder thereof at a price per share equal to the lower of the original per share purchase
price paid by the recipient (subject to adjustment as provided in Section 3(b)) or the current Fair Market Value of such shares, determined immediately prior to the effective time of the Sale Event. 

(C) Notwithstanding anything to the contrary in Section 3(c)(iii)(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 grantees holding Restricted Stock or Restricted Stock Unit Awards in exchange for the cancellation thereof, in an amount equal to the Sale Price times the number of
shares of Stock subject to such Awards, to be paid at the time of such Sale Event or upon the later vesting of such Awards. 

  
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 (iv) Unrestricted Stock Awards. Unless otherwise provided in an Award Agreement, any
shares of Unrestricted Stock shall be treated in a Sale Event the same as all other Shares then outstanding. 
 SECTION 4. ELIGIBILITY

 Grantees under the Plan will be such full or part-time officers and other employees, directors, Consultants and key persons
(including prospective employees, but conditioned on their employment) of the Company and any Subsidiary who are selected from time to time by the Committee in its sole discretion; provided, however, that an Incentive Stock Option may
be granted only to a person who, at the time the Incentive Stock Option is granted, is an employee of the Company or any Subsidiary. 

SECTION 5. STOCK OPTIONS 
 Upon the grant of a Stock Option, the Company and the grantee shall enter into a Stock Option Award Agreement. The terms and conditions of each such Stock Option 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 eligible officers, employees, directors, Consultants and key persons of the Company or any Subsidiary. Stock
Options granted pursuant to this Section 5(a) 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 Stock covered by a Stock Option granted pursuant to
Section 5(a) 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
option price of such Incentive Stock Option shall not be less than 110 percent of the Fair Market Value on the Grant Date. 

(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 after the date the Stock Option is granted. 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 an optionee to exercise all or a portion of a Stock Option immediately at grant; provided that the

  
 9 

 
Option Shares issued upon such exercise shall be subject to restrictions and a vesting schedule identical to the vesting schedule of the related Stock Option and the optionee shall be required to
enter into a Restricted Stock Award Agreement and any other similar documentation required by the Company 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 such shares unless and until a Stock Option shall have been exercised pursuant to the terms hereof and the optionee’s name
shall have 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 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 Option 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 other than with a promissory note 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 of Stock 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 FAS 123R 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; 

(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; and 
 (E) If permitted by the Committee,
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 of Stock issuable upon exercise by the largest whole number of shares with a
Fair Market Value that does not exceed the aggregate exercise price. 

  
 10 

 Payment instruments will be received subject to collection. No certificates for shares of
Stock 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 required by law to be taken in
connection with 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 thereof, (ii) the legending of any certificate (or notation on any book entry) representing the shares to evidence the foregoing restrictions, (iii) obtaining from
optionee payment or provision for all withholding taxes due as a result of the exercise of the Option, and (iv) 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 shares of the Stock. 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 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 Option Award Agreement or applicable provisions of laws. In the event an optionee chooses to pay the purchase price by previously-owned shares of Stock through the
attestation method, the number of shares of Stock 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 time of grant) of the shares of Stock 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.

 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 person 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. The grant of a Restricted Stock Award is contingent on the grantee executing a Restricted Stock 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, all of whom must be eligible persons under Section 4 hereof.

  
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 (b) Rights as a Stockholder. Upon execution of a Restricted Stock Award Agreement 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 Shares of Restricted Stock if, and to the extent, such Shares are entitled to voting rights, subject to
such conditions contained in the Restricted Stock 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. The Restricted Stock Award Agreement may require or permit the immediate payment, waiver, deferral or investment of dividends paid on the Restricted Stock. 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 Restricted Stock 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 any, if a grantee’s employment (or other 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 Restricted Stock Award Agreement. 
 (d) Vesting of Restricted Stock. The Committee at the time of grant
shall specify 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 Restricted Stock 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 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. The grant of Restricted Stock Unit(s) is contingent on the grantee
executing a Restricted Stock Unit 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. 

  
 12 

 (b) Rights as a Stockholder. A grantee shall have the rights of a stockholder only as
to shares of Stock, if any, acquired upon settlement of a Restricted Stock Unit. A grantee shall not be deemed to have acquired any such shares unless and until a Restricted Stock Unit shall have been settled in Stock pursuant to the terms hereof,
the Company shall have issued and delivered a certificate representing the shares to the grantee, and the grantee’s name shall have 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 termination of employment (or cessation of Service Relationship) with the Company and any Subsidiary
for any reason. 
 SECTION 9. TRANSFER RESTRICTIONS; COMPANY RIGHT OF FIRST REFUSAL; COMPANY REPURCHASE RIGHTS 

(a) Restrictions on Transfer. 
 (i) Non-Transferability of Stock Options. No Stock Option shall 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, without consideration for the transfer, his or her Non-Qualified Stock Options to members of his or her immediate family, to trusts for the benefit of
such family members, or to partnerships in which such family members are the only partners, 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 Option.

 (ii) Issued Shares. No Issued 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) such 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) such 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, 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 disposition of Issued 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 Issued Shares as a result of any such disposition, shall otherwise refuse to recognize any such
disposition and shall not in any way give effect to any such disposition of Issued Shares. Subject 

  
 13 

 
to the foregoing general provisions, and unless otherwise provided in the applicable Award Agreement, Issued 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 only with respect to the original recipient): 

(A) Transfers to Permitted Transferees. The Holder may sell, assign, transfer or give away any or all of the Issued
Shares to Permitted Transferees; provided, however, that following such sale, assignment, transfer or gift, such Issued 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. Notwithstanding the foregoing, the Holder may not sell, assign, transfer or give any or all of the Issued Shares to any 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 Issued Shares then held by the Holder at the time of such death and any Issued Shares acquired thereafter 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 Issued Shares to the Company or its
assigns under the terms contemplated hereby. 
 (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 such Holder’s Issued 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 Issued Shares which 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 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 purchased by such proposed transferee shall no longer be subject to the terms of the Plan. 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 shares of the Stock, (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 other 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 Option Shares. The Company or its assigns shall have the right and option upon a Repurchase Event to
repurchase from a Holder of Option Shares some or all (as determined by the Company) of the Option Shares held or subsequently acquired upon exercise of a Stock Option by such Holder at the price per share specified below. Such repurchase right may
be exercised by the Company within the later of (A) six months following the date of such Repurchase Event or (B) seven months after the acquisition of such Option Shares upon exercise of a Stock Option (the “Option Shares Repurchase
Period”). The “Option Shares Repurchase Price” shall be equal to the Fair Market Value of the Option Shares, determined as of the date the Committee elects to exercise its repurchase rights in connection with a Repurchase Event.

 (ii) Right of Repurchase With Respect to Restricted Stock and Shares issued pursuant to an Unrestricted Stock Award or
Restricted Stock Unit Award. Unless otherwise set forth in the agreement entered into by the recipient and the Company in connection with a Restricted Stock Award, Unrestricted Stock Award or Restricted Stock Unit Award, the Company or its
assigns shall have the right and option upon a Repurchase Event to repurchase from a Holder of Issued Shares received pursuant to a Restricted Stock Award, Unrestricted Stock Award or Restricted Stock Unit Award some or all (as determined by the
Company) of such Issued Shares at the price per share specified below. In addition, upon a Termination Event, the Company or its assigns shall have the right and option to repurchase from a Holder of Issued Shares received pursuant to a Restricted
Stock Award any Issued Shares which have not vested as of the Termination Event. Such repurchase right may be exercised by the Company within six months following the date of such Repurchase Event or Termination Event as applicable (the
“Non-Option Shares Repurchase Period”). The “Non-Option Shares Repurchase Price” shall be (i) in the case of Issued Shares which are vested as of the date of the Repurchase Event, the Fair Market Value of such Issued Shares
as of the date the Company elects to exercise its repurchase rights in connection with a Repurchase Event and (ii) in the case of Issued Shares which have not vested as of the date of the Repurchase Event or Termination Event (as applicable),
the lower of the original per share purchase price paid by the recipient subject to adjustment as provided in Section 3(b) or the current Fair Market Value of such Issued Shares as of the date the Company elects to exercise its repurchase
rights in connection with a Repurchase Event or Termination Event (as applicable). 
 (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 Option Shares Repurchase Period or Non-Option Shares Repurchase Period, as applicable, 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 Option Shares Repurchase 

  
 15 

 
Price or the Non-Option Shares Repurchase Price, as applicable; provided, however, that the Company may pay the Option Shares Repurchase Price or Non-Option Shares Repurchase Price, as
applicable, 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 Issued Shares, including any Permitted Transferees, 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 Issued Shares (including for this purpose all of such Holder’s or his or her Permitted Transferee’s Issued 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 Issued 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). 
 (e) Escrow Arrangement. 
 (i) Escrow. In order to carry out the
provisions of Sections 9(b), (c), and (d) of this Agreement more effectively, the Company shall hold any Issued Shares in escrow together with separate stock powers executed by the Holder in blank for transfer, and any Permitted Transferee
shall, as an additional condition to any transfer of Issued Shares, execute a like stock power as to such Issued Shares. The Company shall not dispose of the Issued Shares except as otherwise provided in this Agreement. In the event of any
repurchase by the Company (or any of its assigns), the Company is hereby authorized by the Holder and any Permitted Transferee, as the Holder’s and each such Permitted Transferee’s attorney-in-fact, to date and complete the stock powers
necessary for the transfer of the Issued Shares being purchased and to transfer such Issued Shares in accordance with the terms hereof. At such time as any Issued Shares are no longer subject to the Company’s repurchase, first refusal and drag
along rights, the Company shall, at the written request of the Holder, deliver to the Holder (or the relevant Permitted Transferee) a certificate representing such Issued Shares with the balance of the Issued Shares to be held in escrow pursuant to
this Section 9(e). 
 (ii) Remedy. Without limitation of any other provision of this Agreement or other rights, in
the event that a Holder, any Permitted Transferees or any other Person is required to sell a Holder’s Issued Shares pursuant to the provisions of Sections 9(b), (c), or (d) 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 Issued Shares the certificate or certificates evidencing such Issued Shares together with a related stock power, the Company or such designated purchaser may

  
 16 

 
deposit the applicable purchase price for such Issued 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, any Permitted Transferees 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 Issued Shares to be sold pursuant to
the provisions of Sections 9(b), (c), or (d), such Issued 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. A Holder agrees, if requested by the Company and any underwriter engaged by the Company, not to sell or otherwise transfer or dispose of any Issued 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 any registration statement of the Company filed under the Securities Act as the Company or such underwriter shall
specify reasonably and in good faith. If requested by the underwriter engaged by the Company, each Holder shall execute a separate letter reflecting the agreement set forth in this Section 9(f). 

(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 of Common Stock are increased or decreased or are exchanged for a different number or kind of shares of the Company’s Stock, 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, Issued Shares. 

(h) Termination. The terms and provisions of Section 9(b), Section 9(c) (except for the Company’s right to
repurchase unvested Restricted Stock Awards upon a Termination Event) and Section 9(d) 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 of the Company (or a successor entity) of the same class as the Issued Shares are registered under Section 12 of the Exchange Act and publicly-traded on NASDAQ or 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 Stock or other amounts received thereunder first becomes includable in the gross
income of the grantee for Federal 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. 

  
 17 

 (b) Payment in Stock. Subject to approval by the Committee, the Company’s
minimum required tax withholding obligation may be satisfied, in whole or in part, by the Company withholding from shares of Stock to be issued pursuant to any Award a number of shares with 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 specified by the Committee from time to time in order to comply with Section 409A. 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. 
 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 exercise its discretion to reduce the exercise price of outstanding Stock Options or effect repricing through cancellation of outstanding Awards and by granting such holders new Awards in replacement of the cancelled Awards. 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). 

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 or Awards. 

  
 18 

 SECTION 14. GENERAL PROVISIONS 

(a) No Distribution; Compliance with Legal Requirements. The Committee may require each person acquiring Stock pursuant to an
Award to represent to and agree with the Company in writing that such person is acquiring the shares of Stock without a view to distribution thereof. No shares of Stock 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(e) 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. 
 (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 Issued 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 bluebird bio, Inc. 2010 Stock Option and Grant Plan and any agreement 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). 

  
 19 

 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 articles of incorporation and bylaws within 12 months thereafter. Subject to such approval by stockholders and to the requirement that no Stock 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 Effective Date. 
 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: September 15, 2010 
 DATE APPROVED BY THE STOCKHOLDERS: October 4, 2010 

  
 20 

 INCENTIVE STOCK OPTION AGREEMENT 

UNDER THE BLUEBIRD BIO, INC. 
 2010 STOCK OPTION AND GRANT PLAN 
  

			
	Name of Optionee:	 	                         (the
“Optionee”)
		
	No. of Underlying 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”)

 Pursuant to the bluebird bio, Inc. 2010 Stock Option and Grant Plan (the “Plan”), bluebird bio,
Inc., a Delaware corporation (together with any successor thereto, the “Company”), hereby grants to the Optionee, who is an employee of the Company or any of its Subsidiaries, 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 $0.01 per share (“Common Stock”), of the Company indicated above (the “Underlying
Shares,” and such shares once issued shall be referred to as the “Option Shares”), at the Option Exercise Price per share, subject to the terms and conditions set forth in this Incentive Stock Option Agreement (this
“Agreement”) and in 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. 
 All
capitalized terms used herein and not otherwise defined shall have the respective meanings set forth in 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 with respect to the Underlying Shares on the respective dates indicated below: 

(i) All Underlying Shares shall initially be unvested and unexercisable. 

  
 1 

 (ii) [25] percent of the Underlying 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. 
 (iii) Thereafter, the remaining [75] percent of the Underlying Shares shall vest and become exercisable in [36] equal monthly installments at the end of each month following the first anniversary of the
Vesting Commencement Date, provided the Optionee continues to have a Service Relationship with the Company at such time. 

Notwithstanding anything herein to the contrary in the case of a Sale Event, this Stock Option shall be treated as provided in
Section 3(c) of the Plan. 
 (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 (as defined in Section 422(c) of the Code), 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 (as defined in Section 422(c) of the Code), 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 or other termination 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 exercisable on the date of termination of the Service Relationship shall terminate
immediately and be null and void. 
 (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 Option 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 Option 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 

  
 2 

 
any such Option 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 the Underlying Shares 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 Underlying Shares with respect to which this Stock Option is exercisable at the time of such notice. Such notice shall specify the number of Underlying Shares to be purchased. Payment of the purchase price may be made by one or more of
the methods described in Sections 5(a)(iv)(A), (B), (C) or (D) of the Plan, subject to the limitations contained in such Sections 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 Agreement 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. 
 5. Restrictions on Transfer of Option Shares. The Option 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.

  
 3 

 (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 shares of the Company’s stock, 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, Option Shares. 
 (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 hereof, 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, permitted 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. 

  
 4 

 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, MA. 
 (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 Stock 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. 

[SIGNATURE PAGE FOLLOWS] 

  
 5 

 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. 
  

			
	BLUEBIRD BIO, INC.
		
	By:	 	 
		 	Name:
		 	Title:
		
		 	Address:
		
		 	 840 Memorial Drive

Cambridge, MA 02139

 The undersigned hereby acknowledges receiving and reviewing a copy of the Plan, including, without limitation,
Section 9 thereof, and understands that the Stock Option granted hereby 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 and this Agreement, SPECIFICALLY
INCLUDING THE ARBITRATION PROVISIONS IN SECTION 7 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 
  

	
	OPTIONEE:
	
	  
	Name:
	
	Address:
	
	 
	
	 
	
	 

 [SPOUSE’S CONSENT 
 I acknowledge that I have read the 
 foregoing Incentive Stock Option Agreement 

and understand the contents thereof. 

                         
                                         
  ] 

 
	
	DESIGNATED BENEFICIARY:
	
	  
	

  

	
	Beneficiary’s Address:
	
	  
	
	  
	
	  

 Appendix A 

STOCK OPTION EXERCISE NOTICE 
 BLUEBIRD BIO, INC. 
 Attention:
[                            ] 
 840 Memorial Drive 
 Cambridge, MA 02139 

Pursuant to the terms of the stock option agreement between the undersigned and bluebird bio, Inc. (the “Company”) dated
                     (the “Agreement”) under the bluebird bio, Inc. 2010 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 Underlying Shares]
                     Underlying Shares. I have chosen the following form(s) of payment: 

 

	 	[  ]	1. Cash 

  

	 	[  ]	2. Certified or bank check payable to “bluebird bio, 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 Underlying 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 Underlying 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 Option Shares and am able to bear the economic risk of holding such Option Shares for an indefinite period of time. 

(v) I understand that the Option Shares may not be registered under the Securities Act of 1933 (it being understood that
the Option 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
Option Shares will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Option Shares will include similar restrictive notations. 

 

	
	Sincerely yours,
	
	  
	Name:
	
	Address:
	
	  
	
	  
	
	  

 EARLY EXERCISE 
 INCENTIVE STOCK OPTION AGREEMENT 
 UNDER THE BLUEBIRD BIO, INC.

 2010 STOCK OPTION AND GRANT PLAN 
  

			
	Name of Optionee:	 	                         (the
“Optionee”)
		
	No. of Option 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”)

 Pursuant to the bluebird bio, Inc. 2010 Stock Option and Grant Plan (the “Plan”), bluebird bio,
Inc., a Delaware corporation (together with any successor thereto, the “Company”), hereby grants to the Optionee, who is an employee of the Company or any of its Subsidiaries, 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 $0.01 per share (“Common Stock”), of the Company indicated above (the “Option Shares”),
at the Option Exercise Price per share, subject to the terms and conditions set forth in this Early Exercise Incentive Stock Option Agreement (this “Agreement”) and in 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. 
 All capitalized terms used herein and not otherwise defined shall have the respective
meanings set forth in the Plan. 
 1. Vesting, Exercisability and Termination. 

(a) This Stock Option shall be immediately exercisable, regardless of whether the Option Shares are vested. 

(b) Except as set forth below, and subject to the determination of the Committee in its sole discretion to accelerate the vesting
schedule hereunder, the Option Shares shall be vested on the respective dates indicated below: 
 (i) All Option
Shares shall initially be unvested. 
 (ii) [25] percent of the Option Shares shall vest 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. 

  
 1 

 (iii) Thereafter, the remaining [75] percent of the Option Shares shall vest
in [36] equal monthly installments at the end of each month following the first anniversary of the Vesting Commencement Date, provided the Optionee continues to have a Service Relationship with the Company at such time. 

Notwithstanding anything herein to the contrary in the case of a Sale Event, this Stock Option and the Option Shares shall be treated as
provided in Section 3(c) of the Plan. 
 (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 (as defined in Section 422(c) of the Code), this Stock Option may continue to be exercised, to the extent the Option Shares are vested on the
date of 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 (as defined in Section 422(c) of the Code), and unless otherwise determined by the Committee, this Stock Option may continue to be exercised, to the extent the Option Shares are vested on the date of termination, for a period of 90
days from the date of termination or until the Expiration Date or other termination 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[, such termination shall be treated as a “Repurchase Event” and the Company shall have the right to repurchase the Shares as set forth in Section 9(c) of the Plan]. 

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 with respect to Option Shares that are not vested on the date of termination of the Service Relationship shall terminate
immediately and be null and void. 
 (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 Option 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 Option 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 

  
 2 

 
any such Option 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 the Option Shares 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 Option Shares. Such notice shall specify the number of Option Shares to be purchased. To the extent this Stock Option is only partially exercised, such exercise shall first be with respect to the Option Shares, if any, that have
previously vested, and then with respect to the Option Shares that will next vest, with the Option Shares that vest at the latest date being exercised last. Payment of the purchase price may be made by one or more of the methods described in
Sections 5(a)(iv)(A), (B), (C) or (D) of the Plan, subject to the limitations contained in such Sections of the Plan, including the requirement that the Committee specifically approve in advance certain payment methods. 

(b) In the event the Optionee exercises a portion of this Stock Option with respect to Option Shares that have not vested, the Optionee
shall also deliver a Restricted Stock Agreement covering such unvested Option Shares in the form of Appendix B hereto (the “Restricted Stock Agreement”) with the same vesting schedule for such Option Shares as set forth for such
Option Shares herein. 
 (c) 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 Agreement 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. 
 5. Restrictions on Transfer of Option Shares. The Option 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 and, if applicable, the Restricted Stock Agreement. 

  
 3 

 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 shares of the Company’s stock, 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, Option Shares. 
 (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 hereof, 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, permitted 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. 

  
 4 

 (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. 
 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, MA. 
 (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 Stock 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 

  
 5 

 
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.

 [SIGNATURE PAGE FOLLOWS] 

  
 6 

 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. 
  

			
	BLUEBIRD BIO, INC.
		
	By:	 	 
		 	Name:
		 	Title:
		
		 	Address:
		 	 840 Memorial Drive

Cambridge, MA 02139

 The undersigned hereby acknowledges receiving and reviewing a copy of the Plan, including, without limitation,
Section 9 thereof, and understands that the Stock Option granted hereby 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 and this Agreement, SPECIFICALLY
INCLUDING THE ARBITRATION PROVISIONS IN SECTION 7 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 
  

	
	OPTIONEE:
	
	  
	Name:
	
	Address:
	
	  
	
	  
	
	  

 [SPOUSE’S CONSENT 
 I acknowledge that I have read the 
 foregoing Incentive Stock Option Agreement 

and understand the contents thereof. 

                         
                                         
      ] 

 
	
	DESIGNATED BENEFICIARY:
	
	  
	

  

	
	Beneficiary’s Address:
	
	  
	
	  
	
	  

 Appendix A 

STOCK OPTION EXERCISE NOTICE 
 BLUEBIRD BIO, INC. 
 Attention: Office Manager 

840 Memorial Drive 
 Cambridge, MA 02139

 Pursuant to the terms of the stock option agreement between the undersigned and bluebird bio, Inc. (the “Company”)
dated                      (the “Agreement”) under the bluebird bio, Inc. 2010 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 Option Shares]
                     Option Shares. I have chosen the following form(s) of payment: 

 

	 	[  ]	1. Cash 

  

	 	[  ]	2. Certified or bank check payable to “bluebird bio, 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 Option 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 Option 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 Option Shares and am able to bear the economic risk of holding such
Option Shares for an indefinite period of time. 
 (v) I understand that the Option Shares may not be registered
under the Securities Act of 1933 (it being understood that the Option 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
Option Shares will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Option Shares will include similar restrictive notations. 

(vi) To the extent required, I have executed and delivered to the Company the Restricted Stock Agreement attached as
Appendix B to the Agreement. 
  

	
	Sincerely yours,
	
	  
	Name:
	
	Address:
	
	  
	
	  

 Appendix B 

RESTRICTED STOCK AGREEMENT 

 NON-QUALIFIED STOCK OPTION AGREEMENT 

UNDER THE BLUEBIRD BIO, INC. 
 2010 STOCK OPTION AND GRANT PLAN 
  

			
	Name of Optionee:	 	                         (the
“Optionee”)
		
	No. of Underlying 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”)

 Pursuant to the bluebird bio, Inc. 2010 Stock Option and Grant Plan (the “Plan”), bluebird bio,
Inc., a Delaware corporation (together with any successor thereto, the “Company”), hereby grants to the Optionee, who is an officer, employee, director, Consultant or other key person of the Company or any of its Subsidiaries, 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 $0.01 per share (“Common Stock”), of the Company
indicated above (the “Underlying Shares,” and such shares once issued shall be referred to as the “Option Shares”), at the Option Exercise Price per share, subject to the terms and conditions set forth in this Non-Qualified Stock
Option Agreement (this “Agreement”) and in 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”). 
 All capitalized terms used herein and not otherwise defined shall have the respective meanings set
forth in 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 with respect to the Underlying Shares on the respective dates indicated below: 
 (i) All Underlying Shares shall initially be unvested and unexercisable. 

 (ii) [25] percent of the Underlying 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. 
 (iii) Thereafter, the remaining [75] percent of the Underlying Shares shall vest and become exercisable in [36] equal monthly installments at the end of each month following the first anniversary of the
Vesting Commencement Date, provided the Optionee continues to have a Service Relationship with the Company at such time. 

Notwithstanding anything herein to the contrary in the case of a Sale Event, this Stock Option shall be treated as provided in
Section 3(c) of the Plan. 
 (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 (as defined in Section 422(c) of the Code), 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 (as defined in Section 422(c) of the Code), 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 or other termination 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[, such termination shall be treated as a “Repurchase Event” and the Company shall have the right to repurchase the Shares as set forth in Section 9(c) of the Plan]. 

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 exercisable on the date of termination of the Service Relationship shall terminate
immediately and be null and void. 
 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 Underlying Shares with respect to which this Stock Option is exercisable at the
time of such notice. Such notice shall specify the number of Underlying Shares to be purchased. Payment of the purchase price may be made by one or more of the methods described in Sections 5(a)(iv)(A), (B), (C), (D) or (E) of the Plan,
subject to the limitations contained in such Sections of the Plan, including the requirement that the Committee specifically approve in advance certain payment methods. 

  
 2 

 (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 Agreement 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. 
 5. Restrictions on Transfer of Option Shares. The Option
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 shares of the Company’s stock, 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, Option Shares. 
 (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. 

  
 3 

 (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 hereof, 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, permitted 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. 
 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, MA. 
 (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

  
 4 

 
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 Stock 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. 
 [SIGNATURE PAGE FOLLOWS] 

  
 5 

 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. 
  

			
	BLUEBIRD BIO, INC.
		
	By:	 	 
		 	Name:
		 	Title:
		
		 	 Address:
 840 Memorial
Drive
 Cambridge, MA 02139

 The undersigned hereby acknowledges receiving and reviewing a copy of the Plan, including, without limitation,
Section 9 thereof, and understands that the Stock Option granted hereby 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 and this Agreement, SPECIFICALLY
INCLUDING THE ARBITRATION PROVISIONS IN SECTION 7 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 
  

	
	OPTIONEE:
	
	  
	Name:
	
	Address:
	
	  
	
	  
	
	  

 [SPOUSE’S CONSENT 
 I acknowledge that I have read the 
 foregoing Non-Qualified Stock Option Agreement 

and understand the contents thereof. 

                         
                                         
              ] 

 
	
	DESIGNATED BENEFICIARY:
	
	  
	

  

	
	Beneficiary’s Address:
	
	  
	
	  
	
	  
	

 Appendix A 

STOCK OPTION EXERCISE NOTICE 
 BLUEBIRD BIO, INC. 
 Attention: Office Manager 

840 Memorial Drive 
 Cambridge, MA 02139

 Pursuant to the terms of the stock option agreement between the undersigned and bluebird bio, Inc. (the “Company”)
dated                      (the “Agreement”) under the bluebird bio, Inc. 2010 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 Underlying Shares]
                     Underlying Shares. I have chosen the following form(s) of payment: 

 

	 	[  ]	1. Cash 

  

	 	[  ]	2. Certified or bank check payable to “bluebird bio, 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 Underlying 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 Underlying 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 Option Shares and am able to bear the economic risk of holding such Option Shares for an indefinite period of time. 

(v) I understand that the Option Shares may not be registered under the Securities Act of 1933 (it being understood that
the Option 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
Option Shares will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Option Shares will include similar restrictive notations. 

 

	
	Sincerely yours,
	
	  
	Name:
	
	Address:
	
	  
	
	  
	
	  

 EARLY EXERCISE 
 NON-QUALIFIED STOCK OPTION AGREEMENT 
 UNDER THE BLUEBIRD BIO, INC.

 2010 STOCK OPTION AND GRANT PLAN 
  

			
	Name of Optionee:	 	                         (the
“Optionee”)
		
	No. of Option 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”)

 Pursuant to the bluebird bio, Inc. 2010 Stock Option and Grant Plan (the “Plan”), bluebird bio,
Inc., a Delaware corporation (together with any successor thereto, the “Company”), hereby grants to the Optionee, who is an officer, employee, director, Consultant or other key person of the Company or any of its Subsidiaries, 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 $0.01 per share (“Common Stock”), of the Company
indicated above (the “Option Shares”), at the Option Exercise Price per share, subject to the terms and conditions set forth in this Early Exercise Non-Qualified Stock Option Agreement (this “Agreement”) and in 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”). 

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

1. Vesting, Exercisability and Termination. 
 (a) This Stock Option shall be immediately exercisable, regardless of whether the Option Shares are vested. 
 (b) Except as set forth below, and subject to the determination of the Committee in its sole discretion to accelerate the vesting schedule hereunder, the Option Shares shall be vested on the respective
dates indicated below: 
 (i) All Option Shares shall initially be unvested. 

(ii) [25] percent of the Option Shares shall vest 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. 

  
 1 

 (iii) Thereafter, the remaining [75] percent of the Option Shares shall vest
in [36] equal monthly installments at the end of each month following the first anniversary of the Vesting Commencement Date, provided the Optionee continues to have a Service Relationship with the Company at such time. 

Notwithstanding anything herein to the contrary, in the case of a Sale Event, this Stock Option and the Option Shares shall be treated as
provided in Section 3(c) of the Plan. 
 (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 (as defined in Section 422(c) of the Code), this Stock Option may continue to be exercised, to the extent the Option Shares are vested on the
date of 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 (as defined in Section 422(c) of the Code), and unless otherwise determined by the Committee, this Stock Option may continue to be exercised, to the extent the Option Shares are vested on the date of termination, for a period of 90
days from the date of termination or until the Expiration Date or other termination 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 with respect to Option Shares that are not vested on
the date of termination of the Service Relationship shall terminate immediately and be null and void. 
 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 Option Shares. Such notice shall specify the number of
Option Shares to be purchased. To the extent this Stock Option is only partially exercised, such exercise shall first be with respect to the Option Shares, if any, that have previously vested, and then with respect to the Option Shares that will
next vest, with the Option Shares that vest at the latest date being exercised last. Payment of the purchase price may be made by one or more of the methods described in Sections 5(a)(iv)(A), (B), (C), (D) or (E) of the Plan, subject to
the limitations contained in such Sections of the Plan, including the requirement that the Committee specifically approve in advance certain payment methods. 

  
 2 

 (b) In the event the Optionee exercises a portion of this Stock Option with respect to
Option Shares that have not vested, the Optionee shall also deliver a Restricted Stock Agreement covering such unvested Option Shares in the form of Appendix B hereto (the “Restricted Stock Agreement”) with the same vesting schedule
for such Option Shares as set forth for such Option Shares herein. 
 (c) 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 Agreement 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. 
 5.
Restrictions on Transfer of Option Shares. The Option 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 and, if applicable, the Restricted Stock Agreement. 
 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 shares of the Company’s stock, 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, Option Shares. 

  
 3 

 (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 hereof, 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, permitted 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. 
 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, MA. 

  
 4 

 (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 Stock 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. 

[SIGNATURE PAGE FOLLOWS] 

  
 5 

 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. 
  

			
	BLUEBIRD BIO, 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 Stock Option granted hereby 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 and this Agreement, SPECIFICALLY
INCLUDING THE ARBITRATION PROVISIONS IN SECTION 7 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 
  

	
	OPTIONEE:
	
	  
	Name:
	
	Address:
	
	  
	
	  
	
	  

 [SPOUSE’S CONSENT 
 I acknowledge that I have read the 
 foregoing Non-Qualified Stock Option Agreement 

and understand the contents thereof. 

                         
                                         
                  ] 

 
	
	DESIGNATED BENEFICIARY:
	
	  
	

  

	
	Beneficiary’s Address:
	
	  
	
	  
	
	  
	

 Appendix A 

STOCK OPTION EXERCISE NOTICE 
 BLUEBIRD BIO, INC. 
 Attention:
[                    ] 
  

 
  

 
 Pursuant to the terms
of the stock option agreement between the undersigned and bluebird bio, Inc. (the “Company”) dated                      (the
“Agreement”) under the bluebird bio, Inc. 2010 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 Option Shares]                      Option Shares. I have chosen the following form(s) of payment: 

 

	 	[  ]	1. Cash 

  

	 	[  ]	2. Certified or bank check payable to “bluebird bio, 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 Option 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 Option 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 Option Shares and am able to bear the economic risk of holding such
Option Shares for an indefinite period of time. 
 (v) I understand that the Option Shares may not be registered
under the Securities Act of 1933 (it being understood that the Option 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
Option Shares will bear restrictive legends reflecting the foregoing and/or that book entries for uncertificated Option Shares will include similar restrictive notations. 

(vi) To the extent required, I have executed and delivered to the Company the Restricted Stock Agreement attached as
Appendix B to the Agreement. 
  

	
	Sincerely yours,
	
	  
	Name:
	
	Address:
	
	  
	
	  
	
	  

 Appendix B 

RESTRICTED STOCK AGREEMENT 

 RESTRICTED STOCK AGREEMENT 

UNDER THE BLUEBIRD BIO, INC. 
 2010 STOCK OPTION AND GRANT PLAN 
  

			
	Name of Grantee:	  	                    (the “Grantee”)
		
	No. of Shares:	  	                     Shares of Common Stock (the
“Shares”)
		
	Grant Date:	  	 __________

		
	Vesting Commencement Date:	  	                     (the “Vesting Commencement
Date”)
		
	Per Share Purchase Price:	  	$                     (the “Per Share Purchase
Price”)

 Pursuant to the bluebird bio, Inc. 2010 Stock Option and Grant Plan (the “Plan”), bluebird bio,
Inc., a Delaware corporation (together with any successor entity, the “Company”), hereby grants, sells and issues to the individual named above, who is an officer, employee, director, Consultant or other key person of the Company or any of
the Subsidiaries, the Shares at the Per Share Purchase Price, which represents the fair market value per share on the Grant Date, subject to the terms and conditions set forth herein and in 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. 
 All capitalized terms used herein and not otherwise defined shall have the respective meanings set forth in the Plan. 
 1. Purchase and Sale of Shares; Vesting; Investment Representations. 
 (a)
Purchase and Sale. On the date hereof, the Company hereby sells to the Grantee, and the Grantee hereby purchases from the Company, the number of Shares set forth above for the Per Share Purchase Price. 

  
 1 

 (b) Vesting. On the date of this Agreement, all of the Shares are non-transferable
and subject to a substantial risk of forfeiture and are Shares of Restricted Stock. Except as set forth below, and subject to the determination of the Committee in its sole discretion to accelerate the vesting schedule hereunder, the risk of
forfeiture shall lapse with respect to the Shares on the respective dates indicated below and such Shares shall become vested as follows: 
 (i) All of the Shares shall be vested as of the Vesting Commencement Date. 
 (ii) Notwithstanding anything herein 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. 

(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. 

2. Repurchase Right. Upon a Termination Event or other Repurchase Event, the Company shall have the right to repurchase the Shares
as set forth in Section 9(c) of the Plan; provided, however, that in the case of a Termination Event, the Company shall only have the right to repurchase Shares of Restricted Stock which are unvested as of the date of such Termination Event.

 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 

  
 2 

 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. 
 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 are 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. 
 (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 

  
 3 

 
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. Notices to any holder of the Shares other than the Grantee shall be addressed to the address furnished by such holder to the Company. 
 (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. 
 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, MA. 
 (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 or Stock 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. 

  
 4 

 (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. 
 [SIGNATURE PAGE FOLLOWS] 

  
 5 

 IN WITNESS WHEREOF, the Company and the Grantee have executed this Restricted Stock
Agreement as of the date first above written. 
  

			
	BLUEBIRD BIO, INC.
		
	By:	 	  

		 	Name:
		 	Title:

 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 and this Agreement, SPECIFICALLY INCLUDING
THE ARBITRATION PROVISIONS IN SECTION 6 OF THIS AGREEMENT, are hereby agreed to, by the undersigned as of the date first above written. 
  

	
	GRANTEE:
	
	  
	Name:
	
	Address:
	
	
	

  

	
	[SPOUSE’S CONSENT
	 I acknowledge that I have read the
 foregoing Restricted Stock Agreement
 and understand the contents thereof.

                         
                                         
      ]

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