EX-10.1





 Exhibit 10.1 

 

OMEGA THERAPEUTICS, INC. 

2017 EQUITY INCENTIVE PLAN 


ARTICLE I. 
 PURPOSE.

 The purpose of the Plan is to advance the interests of the Company’s stockholders by enhancing the Company’s ability to
attract, retain and motivate persons who make (or are expected to make) important contributions to the Company by providing such persons with equity ownership opportunities and thereby better aligning the interests of such persons with those of the
Company’s stockholders. Capitalized terms used in the Plan are defined in Article XI below. 
 ARTICLE II. 

ELIGIBILITY. 
 Service
Providers are eligible to be granted Awards under the Plan, subject to the limitations described herein. 
 ARTICLE III. 

ADMINISTRATION AND DELEGATION. 

3.1 Administration. The Plan will be administered by the Administrator. The Administrator shall have authority to determine which
Service Providers will receive Awards, to grant Awards and to set all terms and conditions of Awards (including, but not limited to, vesting, exercise and forfeiture provisions). In addition, the Administrator shall have the authority to take all
actions and make all determinations contemplated by the Plan and to adopt, amend and repeal such administrative rules, guidelines and practices relating to the Plan as it shall deem advisable. The Administrator may correct any defect or ambiguity,
supply any omission or reconcile any inconsistency in the Plan or any Award in the manner and to the extent it shall deem necessary or appropriate to carry the Plan and any Awards into effect, as determined by the Administrator. The Administrator
shall make all determinations under the Plan in the Administrator’s sole discretion and all such determinations shall be final and binding on all persons having or claiming any interest in the Plan or in any Award. 

3.2 Appointment of Committees. To the extent permitted by Applicable Laws, the Board may delegate any or all of its powers under
the Plan to one or more Committees. The Board may abolish any Committee at any time and re-vest in itself any previously delegated authority. 

ARTICLE IV. 
 STOCK
AVAILABLE FOR AWARDS. 
 4.1 Number of Shares. Subject to adjustment under Article VIII hereof, Awards may be made under
the Plan covering up to 24,200,000 shares of Common Stock. If any Award expires or lapses or is terminated, surrendered or canceled without having been fully exercised or is forfeited in whole or in part (including, without limitation, as the result
of shares of Common Stock subject to such Award being repurchased by the Company at or below the original issuance price), in any case in a manner that results in any shares of Common Stock covered by such Award not being issued or being so
reacquired by the Company, the unused Common Stock covered by such Award shall again be available for the grant of Awards under the Plan. Further, shares of Common Stock delivered (either by actual delivery or attestation) to the Company by a
Participant to satisfy the applicable exercise or purchase price of an Award and/or to satisfy any applicable tax withholding obligation (including, without limitation, shares retained by the 












 
Company from the Award being exercised or purchased and/or creating the tax obligation) shall be added to the number of shares of Common Stock available for the grant of Awards under the Plan.
However, in the case of Incentive Stock Options, the foregoing provisions shall be subject to any limitations under the Code. Shares of Common Stock issued under the Plan may consist in whole or in part of authorized but unissued shares, shares
purchased on the open market or treasury shares. 
 4.2 Substitute Awards. In connection with a merger or consolidation of an entity
with the Company or the acquisition by the Company of property or stock of an entity, the Administrator may grant Awards in substitution for any options or other stock or stock-based awards granted prior to such merger or consolidation by such
entity or an affiliate thereof. Substitute Awards may be granted on such terms as the Administrator deems appropriate in the circumstances, notwithstanding any limitations on Awards contained in the Plan. Substitute Awards shall not count against
the overall share limit set forth in Section 4.1 hereof, except as may be required by reason of Section 422 of the Code. 

ARTICLE V. 
 STOCK
OPTIONS. 
 5.1 General. The Administrator may grant Options to any Service Provider, subject to the limitations on Incentive
Stock Options described below. The Administrator shall determine the number of shares of Common Stock to be covered by each Option, the exercise price of each Option and the conditions and limitations applicable to the exercise of each Option,
including, without limitation, conditions relating to Applicable Laws, as it considers necessary or advisable. 
 5.2 Incentive Stock
Options. The Administrator may grant Options intended to qualify as Incentive Stock Options only to employees of the Company, any of the Company’s present or future “parent corporations” or “subsidiary corporations” as
defined in Sections 424(e) or (f) of the Code, respectively, and any other entities the employees of which are eligible to receive Incentive Stock Options under the Code. All Options intended to qualify as Incentive Stock Options shall be
subject to and shall be construed consistently with the requirements of Section 422 of the Code. Neither the Company nor the Administrator shall have any liability to a Participant, or any other party, (i) if an Option (or any part
thereof) which is intended to qualify as an Incentive Stock Option fails to qualify as an Incentive Stock Option or (ii) for any action or omission by the Administrator that causes an Option not to qualify as an Incentive Stock Option,
including, without limitation, the conversion of an Incentive Stock Option to a Non-Qualified Stock Option or the grant of an Option intended as an Incentive Stock Option that fails to satisfy the requirements
under the Code applicable to an Incentive Stock Option. Any Option that is intended to qualify as an Incentive Stock Option, but fails to so qualify for any reason, including, without limitation, the portion of any Option becoming exercisable in
excess of the $100,000 limitation described in Treasury Regulation Section 1.422-4, shall be treated as a Non-Qualified Stock Option for all purposes. 

5.3 Exercise Price. The Administrator shall establish the exercise price of each Option and specify the exercise price in the
applicable Award Agreement. The exercise price shall be not less than 100% of the Fair Market Value on the date the Option is granted. In the case of an Incentive Stock Option granted to an employee who, at the time of grant of the Option, owns (or
is treated as owning under Section 424 of the Code) stock representing more than 10% of the voting power of all classes of stock of the Company (or a “parent corporation” or “subsidiary corporation” thereof within the
meaning of Sections 424(e) or 424(f) of the Code, respectively), the per share exercise price shall be no less than 110% of the Fair Market Value on the date the Option is granted. 

  
 2 













 5.4 Duration of Options. Each Option shall be exercisable at such times and
subject to such terms and conditions as the Administrator may specify in the applicable Award Agreement, provided that the term of any Option shall not exceed ten years. In the case of an Incentive Stock Option granted to an employee who, at the
time of grant of the Option, owns (or is treated as owning under Section 424 of the Code) stock representing more than 10% of the voting power of all classes of stock of the Company (or a “parent corporation” or “subsidiary
corporation” thereof within the meaning of Sections 424(e) or 424(f) of the Code, respectively), the term of the Option shall not exceed five years. 

5.5 Exercise of Option; Notification of Disposition. Options may be exercised by delivery to the Company of a written notice of
exercise, in a form approved by the Administrator (which may be an electronic form), signed by the person authorized to exercise the Option, together with payment in full (i) as specified in Section 5.6 hereof for the number of shares for
which the Option is exercised and (ii) as specified in Section 9.5 hereof for any applicable withholding taxes. Unless otherwise determined by the Administrator, an Option may not be exercised for a fraction of a share of Common Stock. If
an Option is designated as an Incentive Stock Option, the Participant shall give prompt notice to the Company of any disposition or other transfer of any shares of Common Stock acquired from the Option if such disposition or transfer is made
(i) within two years from the grant date with respect to such Option or (ii) within one year after the transfer of such shares to the Participant (other than any such disposition made in connection with a Change in Control). Such notice
shall specify the date of such disposition or other transfer and the amount realized, in cash, other property, assumption of indebtedness or other consideration, by the Participant in such disposition or other transfer. 

5.6 Payment Upon Exercise. Common Stock purchased upon the exercise of an Option granted under the Plan shall be
paid for in cash, by wire transfer of immediately available funds or by check, payable to the order of the Company, or, subject to Section 10.8, any Company insider trading policy (including, without limitation, any blackout periods) and
Applicable Laws, by: 
 (a) If the Company is a Publicly Listed Company, unless the Administrator otherwise determines, (A) delivery of
an irrevocable and unconditional undertaking by a broker acceptable to the Company to deliver promptly to the Company sufficient funds to pay the exercise price, or (B) delivery by the Participant to the Company of a copy of irrevocable and
unconditional instructions to a broker acceptable to the Company to deliver promptly to the Company cash or a check sufficient to pay the exercise price, provided in either case, that such amount is paid to the Company at such time as may be
required by the Administrator; 
 (b) delivery (either by actual delivery or attestation) of shares of Common Stock owned by the Participant
valued at their Fair Market Value, provided (A) such method of payment is then permitted under Applicable Laws, (B) such Common Stock, if acquired directly from the Company, was owned by the Participant for such minimum period of time, if
any, as may be established by the Company at any time, and (C) such Common Stock is not subject to any repurchase, forfeiture, unfulfilled vesting or other similar requirements; 

(c) to the extent permitted by the Administrator, surrendering shares of Common Stock then issuable upon exercise of the Option valued at
their Fair Market Value on the date of exercise; 
 (d) to the extent permitted by the Administrator, delivery of a promissory note of the
Participant to the Company on terms determined by the Administrator; 
 (e) to the extent permitted by the Administrator, delivery of
property of any other kind which constitutes good and valuable consideration as determined by the Administrator; or 
 (f) any combination
of the above permitted forms of payment (including, without limitation, cash or check). 

  
 3 













 5.7 Early Exercise of Options. The Administrator may provide in the terms of an Award
Agreement that the Service Provider may exercise an Option in whole or in part prior to the full vesting of the Option in exchange for unvested shares of Restricted Stock with respect to any unvested portion of the Option so exercised. Shares of
Restricted Stock acquired upon the exercise of any unvested portion of an Option shall be subject to such terms and conditions as the Administrator shall determine. 

ARTICLE VI. 
 RESTRICTED
STOCK; RESTRICTED STOCK UNITS. 
 6.1 General. The Administrator may grant Restricted Stock, or the right to purchase Restricted
Stock, to any Service Provider, subject to the right of the Company to repurchase all or part of such shares at their issue price or other stated or formula price from the Participant (or to require forfeiture of such shares if issued at no cost) in
the event that conditions specified by the Administrator in the applicable Award Agreement are not satisfied prior to the end of the applicable restriction period or periods established by the Administrator for such Award. In addition, the
Administrator may grant to Service Providers Restricted Stock Units, which may be subject to vesting and forfeiture conditions during applicable restriction period or periods, as set forth in an applicable Award Agreement. 

6.2 Terms and Conditions for All Restricted Stock and Restricted Stock Unit Awards. The Administrator shall determine and set forth in
the applicable Award Agreement the terms and conditions applicable to each Restricted Stock and Restricted Stock Unit Award, including, without limitation, the conditions for vesting and repurchase (or forfeiture) and the issue price, in each case,
if any. 
 6.3 Additional Provisions Relating to Restricted Stock. 

(a) Dividends. Participants holding shares of Restricted Stock will be entitled to all ordinary cash dividends paid with respect to
such shares to the extent such dividends have a record date that is on or after the date on which the Participant to whom such Restricted Shares are granted becomes the record holder of such Restricted Shares, unless otherwise provided by the
Administrator in the applicable Award Agreement. In addition, unless otherwise provided by the Administrator, if any dividends or distributions are paid in shares, or consist of a dividend or distribution to holders of Common Stock of property
other than an ordinary cash dividend, the shares or other property will be subject to the same restrictions on transferability and forfeitability as the shares of Restricted Stock with respect to which they were paid. Each dividend payment will be
made as provided in the applicable Award Agreement, but in no event later than the end of the calendar year in which the dividends are paid to stockholders of that class of stock or, if later, the 15th day of the third month following the later of
(A) the date the dividends are paid to stockholders of that class of stock, and (B) the date the dividends are no longer subject to forfeiture.

(b) Stock Certificates. The Company may require that any stock certificates issued in respect of shares of Restricted Stock be
deposited in escrow by the Participant, together with a stock power endorsed in blank, with the Company (or its designee). 
 6.4
Additional Provisions Relating to Restricted Stock Units. 
 (a) Settlement. Upon the vesting of a Restricted Stock Unit, the
Participant shall be entitled to receive from the Company one share of Common Stock or an amount of cash or other property equal to the Fair Market Value of one share of Common Stock on the settlement date, as the Administrator shall determine and
as provided in the applicable Award Agreement. The Administrator may provide that settlement of Restricted Stock Units shall occur upon or as soon as reasonably practicable after the vesting of the Restricted Stock Units or shall instead be
deferred, on a mandatory basis or at the election of the Participant, in a manner that complies with Section 409A.

  
 4 













 (b) Voting Rights. A Participant shall have no voting rights with respect to any
Restricted Stock Units unless and until shares are delivered in settlement thereof.
 (c) Dividend Equivalents. To the extent
provided by the Administrator, a grant of Restricted Stock Units may provide a Participant with the right to receive Dividend Equivalents. Dividend Equivalents may be paid currently or credited to an account for the Participant, may be settled
in cash and/or shares of Common Stock and may be subject to the same restrictions on transfer and forfeitability as the Restricted Stock Units with respect to which the Dividend Equivalents are paid, as determined by the Administrator, subject, in
each case, to such terms and conditions as the Administrator shall establish and set forth in the applicable Award Agreement. 
 ARTICLE
VII. 
 OTHER STOCK-BASED AWARDS. 

Other Stock-Based Awards may be granted hereunder to Participants, including, without limitation, Awards entitling Participants to receive
shares of Common Stock to be delivered in the future. Such Other Stock-Based Awards shall also be available as a form of payment in the settlement of other Awards granted under the Plan, as stand-alone payments and/or as payment in lieu of
compensation to which a Participant is otherwise entitled. Other Stock-Based Awards may be paid in shares of Common Stock, cash or other property, as the Administrator shall determine. Subject to the provisions of the Plan, the
Administrator shall determine the terms and conditions of each Other Stock-Based Award, including, without limitation, any purchase price, transfer restrictions, vesting conditions and other terms and conditions applicable thereto, which shall be
set forth in the applicable Award Agreement. 
 ARTICLE VIII. 

ADJUSTMENTS FOR CHANGES IN COMMON STOCK AND CERTAIN OTHER EVENTS. 

8.1 Certain Transactions or Events. In the event that the Administrator determines that any dividend or other distribution (whether in
the form of cash, Common Stock, other securities, or other property), reorganization, merger, consolidation, combination, repurchase, recapitalization, liquidation, dissolution, or sale, transfer, exchange or other disposition of assets of the
Company, or sale or exchange of Common Stock or other securities of the Company, issuance of warrants or other rights to purchase Common Stock or other securities of the Company, or other similar corporate transaction or event, as determined by the
Administrator, affects the Common Stock such that an adjustment is determined by the Administrator to be appropriate in order to prevent dilution or enlargement of the benefits or potential benefits intended by the Company to be made available under
the Plan or with respect to any Award, then the Administrator may, in such manner as it may deem equitable, adjust any or all of: 
 (a) the
number and kind of shares of Common Stock (or other securities or property) with respect to which Awards may be granted or awarded (including, but not limited to, adjustments of the limitations in Section 4.1 hereof on the maximum number and
kind of shares which may be issued); 
 (b) the number and kind of shares of Common Stock (or other securities or property) subject to
outstanding Awards; 
 (c) the grant or exercise price with respect to any Award; and 

(d) the terms and conditions of any Awards (including, without limitation, any applicable financial or other performance “targets”
specified in an Award Agreement). 

  
 5 













 8.2 Additional Transactions or Events. In the event of any transaction or event
described in Section 8.1 hereof (including, without limitation any change in control) or any unusual or nonrecurring transaction or event affecting the Company or the financial statements or financial condition of the Company, or any change in
any Applicable Laws or accounting principles, the Administrator, on such terms and conditions as it deems appropriate, either by the terms of the Award or by action taken and either automatically or upon the Participant’s request, is hereby
authorized to take any one or more of the following actions whenever the Administrator determines that such action is appropriate in order to (x) prevent dilution or enlargement of the benefits or potential benefits intended by the Company to
be made available under the Plan or with respect to any Award granted or issued under the Plan, (y) to facilitate such transaction or event or (z) give effect to such changes in Applicable Laws or accounting principles: 

(a) To provide for the cancellation of any such Award in exchange for either an amount of cash or other property with a value equal to the
amount that could have been obtained upon the exercise or settlement of the vested portion of such Award or realization of the Participant’s rights under the vested portion of such Award, as applicable; provided that, if the amount that could
have been obtained upon the exercise or settlement of the vested portion of such Award or realization of the Participant’s rights, in any case, is equal to or less than zero, then the vested portion of such Award may be terminated without
payment; 
 (b) To provide that such Award shall vest and, to the extent applicable, be exercisable as to all shares covered thereby,
notwithstanding anything to the contrary in the Plan or the provisions of such Award; 
 (c) To provide that such Award be assumed by the
successor or survivor corporation, or a parent or subsidiary thereof, or shall be substituted for by awards covering the stock of the successor or survivor corporation, or a parent or subsidiary thereof, with appropriate adjustments as to the number
and kind of shares and applicable exercise or purchase price, in all cases, as determined by the Administrator; 
 (d) To make adjustments
in the number and type of shares of Common Stock (or other securities or property) subject to outstanding Awards, and/or in the terms and conditions of (including, without limitation, the grant or exercise price), and the criteria included in,
outstanding Awards; 
 (e) To replace such Award with other rights or property selected by the Administrator; and/or 

(f) To provide that the Award will terminate and cannot vest, be exercised or become payable after the applicable event. 

8.3 Equity Restructurings. In connection with the occurrence of any Equity Restructuring, and notwithstanding anything to the contrary
in this Article VIII, the Administrator will equitably adjust each outstanding Award, which adjustments may include adjustments to the number and type of securities subject to each outstanding Award and/or the exercise price or grant price thereof,
if applicable, the grant of new Awards to Participants, and/or the making of a cash payment to Participants, as the Administrator deems appropriate to reflect such Equity Restructuring. The adjustments provided under this Section shall be
nondiscretionary and shall be final and binding on the affected Participant and the Company; provided that whether an adjustment is equitable shall be determined by the Administrator. 

8.4 Administrative Stand Still. In the event of any pending stock dividend, stock split, combination or exchange of shares, merger,
consolidation or other distribution (other than normal cash dividends) of Company assets to stockholders, or any other change affecting the shares of Common Stock or the share price of the Common Stock, including, without limitation, any Equity
Restructuring, for reasons of administrative convenience the Administrator may refuse to permit the exercise of any Award during a period of up to thirty days prior to the consummation of any such transaction. 

  
 6 













 8.5 Miscellaneous. Except as expressly provided in the Plan or pursuant to action of
the Administrator under the Plan, no Participant shall have any rights by reason of any subdivision or consolidation of shares of stock of any class, the payment of any dividend, any increase or decrease in the number of shares of stock of any class
or any dissolution, liquidation, merger, or consolidation of the Company or any other corporation. Except as expressly provided in the Plan or pursuant to action of the Administrator under the Plan, 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 of shares of Common Stock subject to an Award or the grant or exercise price of any
Award. The existence of the Plan, any Award Agreements and the Awards granted hereunder shall not affect or restrict in any way the right or power of the Company to make or authorize (i) any adjustment, recapitalization, reorganization or other
change in the Company’s capital structure or its business, (ii) any merger, consolidation dissolution or liquidation of the Company or sale of Company assets or (iii) any sale or issuance of securities, including, without limitation,
securities with rights superior to those of the Common Stock or which are convertible into or exchangeable for Common Stock. The Administrator may treat Participants and Awards (or portions thereof) differently under this Article VIII. 

ARTICLE IX. 
 GENERAL
PROVISIONS APPLICABLE TO AWARDS. 
 9.1 Transferability. Except as the Administrator may otherwise determine or provide in an
Award Agreement or otherwise, in any case in accordance with Applicable Laws, neither Awards nor any interest therein shall not be sold, assigned, transferred, pledged or otherwise encumbered by the person to whom they are granted, either
voluntarily or by operation of law, except by will or the laws of descent and distribution, and, during the life of the Participant, shall be exercisable only by the Participant. References to a Participant, to the extent relevant in the context,
shall include references to authorized transferees. 
 9.2 Documentation. Each Award shall be evidenced in an Award Agreement, which
may be in such form (written, electronic or otherwise) as the Administrator shall determine. Each Award may contain terms and conditions in addition to those set forth in the Plan. 

9.3 Discretion. Except as otherwise provided by the Plan, each Award may be made alone or in addition or in relation to any other
Award. The terms of each Award to a Participant need not be identical, and the Administrator need not treat Participants or Awards (or portions thereof) uniformly. 

9.4 Termination of Status. The Administrator shall determine the effect on an Award of the disability, death, retirement, authorized
leave of absence or any other change or purported change in a Participant’s Service Provider status and the extent to which, and the period during which, the Participant, the Participant’s legal representative, conservator, guardian or
Designated Beneficiary may exercise rights under the Award, if applicable. 
 9.5 Withholding. Each Participant shall pay to
the Company, or make provision satisfactory to the Administrator for payment of, any taxes required by law to be withheld in connection with Awards to such Participant no later than the date of the event creating the tax liability. Except as the
Administrator may otherwise determine, all such payments shall be made in cash, by wire transfer of immediately available funds or by certified check. Notwithstanding the foregoing, Participants may satisfy such tax obligations, subject to
Section 10.8, any Company insider trading policy (including blackout periods) and Applicable Laws, (i) to the extent permitted by the Administrator, in whole or in part by delivery of Shares, including Shares retained from the Award
creating the tax obligation, valued at their Fair Market Value, 

  
 7 













 
and (ii) if there is a public market for Shares at the time the tax obligations are satisfied, unless the Administrator otherwise determines, (A) delivery (including, without
limitation, telephonically to the extent permitted by the Company) of an irrevocable and unconditional undertaking by a broker acceptable to the Company to deliver promptly to the Company sufficient funds to satisfy the tax obligations, or
(B) delivery by the Participant to the Company of a copy of irrevocable and unconditional instructions to a broker acceptable to the Company to deliver promptly to the Company cash or a check sufficient to satisfy the tax withholding; provided
that such amount is paid to the Company at such time as may be required by the Administrator. The Company may, to the extent permitted by Applicable Laws, deduct any such tax obligations based on minimum statutory withholding rates from any payment
of any kind otherwise due to a Participant. 
 9.6 Amendment of Award. The Administrator may amend, modify or terminate any
outstanding Award, including but not limited to, substituting therefor another Award of the same or a different type, changing the date of exercise or settlement, and converting an Incentive Stock Option to a
Non-Qualified Stock Option. The Participant’s consent to such action shall be required unless (i) the Administrator determines that the action, taking into account any related action, would not
materially and adversely affect the Participant, or (ii) the change is permitted under Article VIII and Section 10.6 hereof. 

9.7 Conditions on Delivery of Stock. The Company will not be obligated to deliver any shares of Common Stock pursuant to the Plan or to
remove restrictions from shares previously delivered under the Plan until (i) all conditions of the Award have been met or removed to the satisfaction of the Company, (ii) in the opinion of the Company’s counsel, all other legal
matters in connection with the issuance and delivery of such shares have been satisfied, including, without limitation, any applicable securities laws and any applicable stock exchange or stock market rules and regulations, and (iii) the
Participant has executed and delivered to the Company such representations or agreements as the Administrator deems necessary or appropriate to satisfy the requirements of any Applicable Laws. The inability of the Company to obtain authority from
any regulatory body having jurisdiction, which authority is determined by the Administrator to be necessary to the lawful issuance and sale of any securities hereunder, shall relieve the Company of any liability in respect of the failure to issue or
sell such shares as to which such requisite authority shall not have been obtained. 
 9.8 Acceleration. The Administrator may at any
time provide that any Award shall become vested and/or exercisable in full or in part, free of some or all restrictions or conditions, or otherwise realizable in full or in part, as the case may be. 

ARTICLE X. 

MISCELLANEOUS. 
 10.1 No
Right To Employment or Other Status. No person shall have any claim or right to be granted an Award, and the grant of an Award shall not be construed as giving a Participant the right to continued employment or any other relationship with the
Company. The Company expressly reserves the right at any time to dismiss or otherwise terminate its relationship with a Participant free from any liability or claim under the Plan or any Award, except as expressly provided in an applicable Award
Agreement. 
 10.2 No Rights As Stockholder; Certificates. Subject to the provisions of the applicable Award Agreement, no
Participant or Designated Beneficiary shall have any rights as a stockholder with respect to any shares of Common Stock to be distributed with respect to an Award until becoming the record holder of such shares. Notwithstanding any other provision
of the Plan, unless otherwise determined by the Administrator or required by any Applicable Laws, the Company shall not be required to deliver to any Participant certificates evidencing shares of Common Stock issued in connection with any Award and
instead such shares of Common Stock may be recorded in the books of the Company (or, as applicable, its transfer agent or stock plan administrator). The Company may place legends on stock certificates issued under the Plan deemed necessary or
appropriate by the Administrator in order to comply with Applicable Laws. 

  
 8 













 10.3 Effective Date and Term of Plan. The Plan shall become effective on the date on
which it is adopted by the Board. No Awards shall be granted under the Plan after the completion of ten years from the earlier of (i) the date on which the Plan was adopted by the Board or (ii) the date the Plan was approved by the
Company’s stockholders, but Awards previously granted may extend beyond that date in accordance with the terms of the Plan. 
 10.4
Amendment of Plan. The Administrator may amend, suspend or terminate the Plan or any portion thereof at any time; provided that no amendment of the Plan shall materially and adversely affect (as determined by the Administrator) any Award
outstanding at the time of such amendment without the consent of the affected Participant. Awards outstanding under the Plan at the time of any suspension or termination of the Plan shall continue to be governed in accordance with the terms of the
Plan and the applicable Award Agreement, as in effect prior to such suspension or termination. The Board shall obtain stockholder approval of any Plan amendment to the extent necessary to comply with Applicable Laws. 

10.5 Provisions for Foreign Participants. The Administrator may modify Awards granted to Participants who are foreign nationals or
employed outside the United States or establish subplans or procedures under the Plan to address differences in laws, rules, regulations or customs of such foreign jurisdictions with respect to tax, securities, currency, employee benefit or other
matters. 
 10.6 Section 409A.

(a) General. The Company intends that all Awards be structured in compliance with, or to satisfy an exemption from, Section 409A,
such that no adverse tax consequences, interest, or penalties under Section 409A apply in connection with any Awards. Notwithstanding anything herein or in any Award Agreement to the contrary, the Administrator may, without a Participant’s
prior consent, amend this Plan and/or Awards, adopt policies and procedures, or take any other actions (including, without limitation, amendments, policies, procedures and actions with retroactive effect) as are necessary or appropriate to preserve
the intended tax treatment of Awards under the Plan, including, without limitation, any such actions intended to (A) exempt this Plan and/or any Award from the application of Section 409A, and/or (B) comply with the requirements of
Section 409A, including, without limitation any such regulations, guidance, compliance programs and other interpretative authority that may be issued after the date of grant of any Award. The Company makes no representations or warranties as to
the tax treatment of any Award under Section 409A or otherwise. The Company shall have no obligation under this Section 10(f) or otherwise to take any action (whether or not described herein) to avoid the imposition of taxes, penalties or
interest under Section 409A with respect to any Award and shall have no liability to any Participant or any other person if any Award, compensation or other benefits under the Plan are determined to constitute
non-compliant, “nonqualified deferred compensation” subject to the imposition of taxes, penalties and/or interest under Section 409A. 

(b) Separation from Service. With respect to any Award that constitutes “nonqualified deferred compensation” under
Section 409A, any payment or settlement of such Award that is to be made upon a termination of a Participant’s Service Provider relationship shall, to the extent necessary to avoid the imposition of taxes under Section 409A, be made
only upon the Participant’s “separation from service” (within the meaning of Section 409A), whether such “separation from service” occurs upon or subsequent to the termination of the Participant’s Service Provider
relationship. For purposes of any such provision of this Plan or any Award Agreement relating to any such payments or benefits, references to a “termination,” “termination of employment” or like terms shall mean “separation
from service.” 

  
 9 













 (c) Payments to Specified Employees. Notwithstanding any contrary provision in the
Plan or any Award Agreement, any payment(s) of “nonqualified deferred compensation” that are otherwise required to be made under an Award to a “specified employee” (as defined under Section 409A and determined by the
Administrator) as a result of his or her “separation from service” shall, to the extent necessary to avoid the imposition of taxes under Code Section 409A(a)(2)(B)(i), be delayed until the expiration of the six-month period immediately following such “separation from service” (or, if earlier, until the date of death of the specified employee) and shall instead be paid (in a manner set forth in the Award
agreement) on the day that immediately follows the end of such six-month period or as soon as administratively practicable thereafter (without interest). Any payments of “nonqualified deferred
compensation” under such Award that are, by their terms, payable more than six months following the Participant’s “separation from service” shall be paid at the time or times such payments are otherwise scheduled to be made. 

10.7 Limitations on Liability. Notwithstanding any other provisions of the Plan, no individual acting as a director, officer,
other employee or agent of the Company will be liable to any Participant, former Participant, spouse, beneficiary, or any other person for any claim, loss, liability, or expense incurred in connection with the Plan or any Award, nor will such
individual be personally liable with respect to the Plan because of any contract or other instrument he or she executes in his or her capacity as an Administrator, director, officer, other employee or agent of the Company. The Company will
indemnify and hold harmless each director, officer, other employee and agent of the Company to whom any duty or power relating to the administration or interpretation of the Plan has been or will be granted or delegated, against any cost or expense
(including, without limitation, attorneys’ fees) or liability (including, without limitation, any sum paid in settlement of a claim with the Administrator’s approval) arising out of any act or omission to act concerning this Plan unless
arising out of such person’s own fraud or bad faith.
 10.8 Lock-Up Period. By accepting
an Award, each Participant agrees that the Participant will not, without the prior written consent of the managing underwriter, during the period commencing on the date of the final prospectus relating to an initial public offering of any of the
Company’s securities and ending on the date specified by the Company and the managing underwriter (such period not to exceed one hundred eighty (180) days, or such other period as may be requested by the Company or an underwriter to
accommodate regulatory restrictions on (1) the publication or other distribution of research reports, and (2) analyst recommendations and opinions, including, but not limited to, the restrictions contained in FINRA Rule 2241 or NYSE Rule
472(f)(4)), (i) lend; offer; pledge; sell; contract to sell; sell any option or contract to purchase; purchase any option or contract to sell; grant any option, right, or warrant to purchase; or otherwise transfer or dispose of, directly or
indirectly, any shares of Common Stock or any securities convertible into or exercisable or exchangeable (directly or indirectly) for Common Stock held immediately before the effective date of the registration statement for such offering or
(ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of such securities, whether any such transaction described in clause (i) or (ii) above is to be
settled by delivery of Common Stock or other securities, in cash, or otherwise. The foregoing provisions of this Section shall apply only to an initial public offering of the Company’s securities and shall not apply to the sale of any shares to
an underwriter pursuant to an underwriting agreement for such initial public offering. The underwriters in connection with such registration are intended third-party beneficiaries of this Section and shall have the right, power, and authority to
enforce the provisions hereof as though they were a party hereto. Each Participant further agrees to execute such agreements as may be reasonably requested by the underwriters in connection with such registration that are consistent with this
Section or that are necessary to give further effect thereto. 

  
 10 













 10.9 Right of First Refusal. 

(a) Before any shares of Common Stock held by a Participant or any permitted transferee (each, a “Holder”) may be
sold, pledged, assigned, hypothecated, transferred, or otherwise disposed of (each, a “Transfer”), the Company or its assignee(s) shall have a right of first refusal to purchase the shares of Common Stock proposed to be
Transferred on the terms and conditions set forth in this Section 10.9 (the “Right of First Refusal”). In the event that the Company’s charter, bylaws and/or a stockholders’ agreement applicable to the shares
of Common Stock contain a right of first refusal with respect to the shares of Common Stock, such right of first refusal shall apply to the shares of Common Stock to the extent such provisions are more restrictive than the Right of First Refusal set
forth in this Section 10.9 and the Right of First Refusal set forth in this Section 10.9 shall not in any way restrict the operation of the Company’s charter, bylaws or the operation of any applicable stockholders’ agreement.

 (b) In the event any Holder desires to Transfer any shares of Common Stock, the Holder shall deliver to the Company a written notice (the
“Notice”) stating: (A) the Holder’s bona fide intention to sell or otherwise Transfer such shares of Common Stock; (B) the name of each proposed purchaser or other transferee (“Proposed
Transferee”); (C) the number of shares of Common Stock to be Transferred to each Proposed Transferee; and (D) the price for which the Holder proposes to Transfer the shares of Common Stock (the “Offered
Price”), and the Holder shall offer such shares of Common Stock at the Offered Price to the Company or its assignee(s). 
 (c)
Within twenty-five days after receipt of the Notice, the Company and/or its assignee(s) may elect in writing to purchase all, but not less than all, of the shares of Common Stock proposed to be Transferred to any one or more of the Proposed
Transferees by delivery of a written exercise notice to the Holder (a “Company Notice”). The purchase price (“Purchase Price”) for the shares of Common Stock repurchased under this Section 10.9
shall be the Offered Price. 
 (d) Payment of the Purchase Price shall be made, at the option of the Company or its assignee(s), in cash (by
check or wire transfer), by cancellation of all or a portion of any outstanding indebtedness of the Holder to the Company (or, in the case of repurchase by an assignee, to the assignee), or by any combination thereof, within five days after delivery
of the Company Notice or in the manner and at the times mutually agreed to by the Company and the Holder. Should the Offered Price specified in the Notice be payable in property other than cash, the Company or its assignee shall have the right to
pay the purchase price in the form of cash equal in amount to the value of such property, as determined by the Administrator. 
 (e) If all
or a portion of the shares of Common Stock proposed in the Notice to be Transferred are not purchased by the Company and/or its assignee(s) as provided in this Section 10.9, then the Holder may sell or otherwise Transfer such shares of Common
Stock to that Proposed Transferee at the Offered Price or at a higher price; provided that such sale or other Transfer is consummated within sixty days after the date of the Notice; and provided, further, that any such sale or other Transfer is
effected in accordance with any Applicable Laws and the Proposed Transferee agrees in writing that the provisions of this Plan and the applicable Award Agreement and any other applicable agreements governing the shares of Common Stock to be
Transferred shall continue to apply to the shares of Common Stock in the hands of such Proposed Transferee. If the shares of Common Stock described in the Notice are not Transferred to the Proposed Transferee within such sixty-day period, a new Notice shall be given to the Company, and the Company and/or its assignees shall again be offered the Right of First Refusal, as provided herein, before any shares of Common Stock held by the
Holder may be sold or otherwise Transferred. 

  
 11 













 (f) Anything to the contrary contained in this Section 10.9 notwithstanding and to the
extent permitted by the Administrator, the Transfer of any or all of the shares of Common Stock during a Participant’s lifetime or upon a Participant’s death by will or intestacy to the Participant’s Immediate Family or a trust for
the benefit of the Participant’s Immediate Family shall be exempt from the Right of First Refusal. As used herein, “Immediate Family” shall mean spouse, lineal descendant or antecedent, father, mother, brother or sister
or stepchild (whether or not adopted). In such case, the transferee or other recipient shall receive and hold the shares of Common Stock so Transferred subject to the provisions of this Plan (including, without limitation, the Right of First
Refusal), the applicable Award Agreement and any other applicable agreements governing the shares of Common Stock to be Transferred, and there shall be no further Transfer of such shares of Common Stock except in accordance with the terms of this
Section 10.9 (or otherwise as expressly provided under the Plan). 
 (g) The Right of First Refusal shall terminate as to all shares of
Common Stock if the Company becomes a Publicly Listed Company upon such occurrence. 
 10.10 Data Privacy. As a condition of receipt
of any Award, each Participant explicitly and unambiguously consents to the collection, use and transfer, in electronic or other form, of personal data as described in this paragraph by and among, as applicable, the Company and its subsidiaries and
affiliates for the exclusive purpose of implementing, administering and managing the Participant’s participation in the Plan. The Company and its subsidiaries and affiliates may hold certain personal information about a Participant, including
but not limited to, the Participant’s name, home address and telephone number, date of birth, social security or insurance number or other identification number, salary, nationality, job title(s), any shares of stock held in the Company or any
of its subsidiaries and affiliates, details of all Awards, in each case, for the purpose of implementing, managing and administering the Plan and Awards (the “Data”). The Company and its subsidiaries and affiliates may
transfer the Data amongst themselves as necessary for the purpose of implementation, administration and management of a Participant’s participation in the Plan, and the Company and its subsidiaries and affiliates may each further transfer the
Data to any third parties assisting the Company in the implementation, administration and management of the Plan. These recipients may be located in the Participant’s country, or elsewhere, and the Participant’s country may have different
data privacy laws and protections than the recipients’ country. Through acceptance of an Award, each Participant authorizes such recipients to receive, possess, use, retain and transfer the Data, in electronic or other form, for the purposes of
implementing, administering and managing the Participant’s participation in the Plan, including, without limitation, any requisite transfer of such Data as may be required to a broker or other third party with whom the Company or the
Participant may elect to deposit any shares of Common Stock. The Data related to a Participant will be held only as long as is necessary to implement, administer, and manage the Participant’s participation in the Plan. A Participant may, at any
time, view the Data held by the Company with respect to such Participant, request additional information about the storage and processing of the Data with respect to such Participant, recommend any necessary corrections to the Data with respect to
the Participant or refuse or withdraw the consents herein in writing, in any case without cost, by contacting his or her local human resources representative. The Company may cancel Participant’s ability to participate in the Plan and, in the
Administrator’s discretion, the Participant may forfeit any outstanding Awards if the Participant refuses or withdraws his or her consents as described herein. For more information on the consequences of refusal to consent or withdrawal of
consent, Participants may contact their local human resources representative. 
 10.11 Severability. In the event any portion of the
Plan or any action taken pursuant thereto shall be held illegal or invalid for any reason, the illegality or invalidity shall not affect the remaining parts of the Plan, and the Plan shall be construed and enforced as if the illegal or invalid
provisions had not been included, and the illegal or invalid action shall be null and void. 
 10.12 Governing Documents. In the
event of any contradiction between the Plan and any Award Agreement or any other written agreement between a Participant and the Company or any Subsidiary of the Company that has been approved by the Administrator, the terms of the Plan shall
govern, unless it is expressly specified in such Award Agreement or other written document that a specific provision of the Plan shall not apply. 

  
 12 













 10.13 Submission to Jurisdiction; Waiver of Jury Trial. By accepting an Award,
each Participant irrevocably and unconditionally consents to submit to the exclusive jurisdiction of the courts of the State of Delaware and of the United States of America, in each case located in the State of Delaware, for any action arising out
of or relating to the Plan (and agrees not to commence any litigation relating thereto except in such courts), and further agrees that service of any process, summons, notice or document by U.S. registered mail to the address contained in the
records of the Company shall be effective service of process for any litigation brought against it in any such court. By accepting an Award, each Participant irrevocably and unconditionally waives any objection to the laying of venue of any
litigation arising out of Plan or Award hereunder in the courts of the State of Delaware or the United States of America, in each case located in the State of Delaware, and further irrevocably and unconditionally waives and agrees not to plead or
claim in any such court that any such litigation brought in any such court has been brought in an inconvenient forum. By accepting an Award, each Participant irrevocably and unconditionally waives, to the fullest extent permitted by applicable law,
any and all rights to trial by jury in connection with any litigation arising out of or relating to the Plan or any Award hereunder. 

10.14 Governing Law. The provisions of the Plan and all Awards made hereunder shall be governed by and interpreted in accordance
with the laws of the State of Delaware, disregarding choice-of-law principles of the law of any state that would require the application of the laws of a jurisdiction
other than such state. 
 10.15 Restrictions on Shares; Claw-back Provisions. Shares of Common Stock acquired in respect of
Awards shall be subject to such terms and conditions as the Administrator shall determine, including, without limitation, restrictions on the transferability of shares of Common Stock, the right of the Company to repurchase shares of Common Stock,
the right of the Company to require that shares of Common Stock be transferred in the event of certain transactions, tag-along rights, bring-along rights, redemption and
co-sale rights and voting requirements. Such terms and conditions may be additional to those contained in the Plan and may, as determined by the Administrator, be contained in the applicable Award Agreement or
in an exercise notice, stockholders’ agreement or in such other agreement as the Administrator shall determine, in each case in a form determined by the Administrator. The issuance of such shares of Common Stock shall be conditioned on the
Participant’s consent to such terms and conditions and the Participant’s entering into such agreement or agreements. All Awards (including, without limitation, any proceeds, gains or other economic benefit actually or constructively
received by Participant upon any receipt or exercise of any Award or upon the receipt or resale of any shares of Common Stock underlying the Award) shall be subject to the provisions of any claw-back policy implemented by the Company, including,
without limitation, any claw-back policy adopted to comply with the requirements of the Dodd-Frank Wall Street Reform and Consumer Protection Act and any rules or regulations promulgated thereunder, to the extent set forth in such claw-back policy
and/or in the applicable Award Agreement. 
 10.16 Titles and Headings. The titles and headings of the Sections in the Plan are for
convenience of reference only and, in the event of any conflict, the text of the Plan, rather than such titles or headings, shall control. 

10.17 Conformity to Securities Laws. Participant acknowledges that the Plan is intended to conform to the extent necessary with all
provisions of the Securities Act and the Exchange Act and any and all regulations and rules promulgated by the Securities and Exchange Commission thereunder, and state securities laws and regulations. Notwithstanding anything herein to the contrary,
the Plan and all Awards granted hereunder shall be administered only in such a manner as to conform to such laws, rules and regulations. To the extent permitted by Applicable Laws, the Plan and all Award Agreements shall be deemed amended to the
extent necessary to conform to such laws, rules and regulations. 

  
 13 













 ARTICLE XI. 

DEFINITIONS. AS USED IN THE PLAN, THE FOLLOWING WORDS AND PHRASES SHALL 

HAVE THE FOLLOWING MEANINGS: 

11.1 “Administrator” means the Board or a Committee to the extent that the Board’s powers or authority under the
Plan have been delegated to such Committee. 
 11.2 “Applicable Laws” means the requirements relating to the
administration of equity incentive plans under U.S. federal and state securities, tax and other applicable laws, rules and regulations, the applicable rules of any stock exchange or quotation system on which the Common Stock is listed or quoted and
the applicable laws and rules of any foreign country or other jurisdiction where Awards are granted or issued under the Plan. 
 11.3
“Award” means, individually or collectively, a grant under the Plan of Options, Restricted Stock, Restricted Stock Units or Other Stock-Based Awards. 

11.4 “Award Agreement” means a written agreement evidencing an Award, which agreements may be in electronic medium and
shall contain such terms and conditions with respect to an Award as the Administrator shall determine, consistent with and subject to the terms and conditions of the Plan. 

11.5 “Board” means the Board of Directors of the Company. 

11.6 “Change in Control” means (i) a merger or consolidation of the Company with or into any other corporation or
other entity or person, (ii) a sale, lease, exchange or other transfer in one transaction or a series of related transactions of all or substantially all of the Company’s assets, or (iii) any other transaction, including, without
limitation, the sale by the Company of new shares of its capital stock or a transfer of existing shares of capital stock of the Company, the result of which is that a third party that is not an affiliate of the Company or its stockholders (or a
group of third parties not affiliated with the Company or its stockholders) immediately prior to such transaction acquires or holds capital stock of the Company representing a majority of the Company’s outstanding voting power immediately
following such transaction; provided that the following events shall not constitute a “Change in Control”: (A) a transaction (other than a sale of all or substantially all of the Company’s assets) in which the holders of the voting
securities of the Company immediately prior to the merger or consolidation hold, directly or indirectly, a majority of the voting securities in the successor corporation or its parent immediately after the merger or consolidation; (B) a sale,
lease, exchange or other transaction in one transaction or a series of related transactions of all or substantially all of the Company’s assets to an affiliate of the Company; (C) an initial public offering of any of the Company’s
securities or any other transaction or series of related transactions principally for bona fide equity financing purposes; (D) a reincorporation of the Company solely to change its jurisdiction; or (E) a transaction undertaken for the
primary purpose of creating a holding company that will be owned in substantially the same proportion by the persons who held the Company’s securities immediately before such transaction. Notwithstanding the foregoing, if a Change in Control
would give rise to a payment or settlement event with respect to any Award that constitutes “nonqualified deferred compensation,” the transaction or event constituting the Change in Control must also constitute a “change in control
event” (as defined in Treasury Regulation Section 1.409A-3(i)(5)) in order to give rise to the payment or settlement event for such Award, to the extent required by Section 409A. 

11.7 “Code” means the Internal Revenue Code of 1986, as amended, and the regulations issued thereunder. 

  
 14 













 11.8 “Committee” means one or more committees or subcommittees of
the Board or the Company, which may be comprised of one or more directors and/or executive officers of the Company, in either case, to the extent permitted in accordance with Applicable Laws. 

11.9 “Common Stock” means the common stock of the Company.  

11.10 “Company” means Omega Therapeutics, Inc., a Delaware corporation, or any successor thereto. Except where the
context otherwise requires, the term “Company” includes any of the Company’s present or future parent or subsidiary corporations as defined in Sections 424(e) or (f) of the Code and any other business venture (including,
without limitation, joint venture or limited liability company) in which the Company has a significant interest, as determined by the Administrator. 

11.11 “Consultant” means any person, including, without limitation, any advisor, engaged by the Company
or a parent or subsidiary of the Company to render services to such entity if: (i) the consultant or adviser renders bona fide services to the Company; (ii) the services rendered by the consultant or advisor 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; and (iii) the consultant or advisor is a natural person, or such other
advisor or consultant as is approved by the Administrator. 
 11.12 “Designated Beneficiary” means the
beneficiary or beneficiaries designated, in a manner determined by the Administrator, by a Participant to receive amounts due or exercise rights of the Participant in the event of the Participant’s death or incapacity    In
the absence of an effective designation by a Participant, “Designated Beneficiary” shall mean the Participant’s estate. 

11.13 “Director” means a member of the Board. 

11.14 “Disability” means a permanent and total disability within the meaning of Section 22(e)(3) of the
Code, as it may be amended from time to time. 
 11.15 “Dividend Equivalents” means a right granted to a Participant
pursuant to Section 6.4(c) hereof to receive the equivalent value (in cash or shares of Common Stock) of dividends paid on shares of Common Stock. 

11.16 “Employee” means any person, including, without limitation, officers and Directors, employed by the Company
(within the meaning of Section 3401(c) of the Code) or any parent or subsidiary of the Company. 
 11.17 “Equity
Restructuring” means, as determined by the Administrator, a non-reciprocal transaction between the Company and its stockholders, such as a stock dividend, stock split, spin-off or recapitalization through a large, nonrecurring cash dividend, that affects the shares of Common Stock (or other securities of the Company) or the share price of Common Stock (or other securities of the
Company) and causes a change in the per share value of the Common Stock underlying outstanding Awards. 
 11.18 “Exchange
Act” means the Securities Exchange Act of 1934, as amended. 
 11.19 “Fair Market Value” means, as of
any date, the value of Stock determined as follows: (i) if the Common Stock is listed on any established stock exchange, its Fair Market Value shall be the closing sales price for such Common Stock as quoted on such exchange for such date, or
if no sale occurred on such date, the first market trading day immediately prior to such date during which a sale occurred, as reported in The Wall Street Journal or such other source as the Administrator deems reliable; (ii) if the
Common Stock is not traded on a stock exchange but is quoted on a national market or other quotation 

  
 15 













 
system, the last sales price on such date, or if no sales occurred on such date, then on the date immediately prior to such date on which sales prices are reported, as reported in The Wall
Street Journal or such other source as the Administrator deems reliable; or (iii) in the absence of an established market for the Common Stock, the Fair Market Value thereof shall be determined by the Administrator in its sole discretion.

 11.20 “Incentive Stock Option” means an “incentive stock option” as defined in Section 422 of the
Code. 
 11.21 “Non-Qualified Stock Option” means an Option that is
not intended to be or otherwise does not qualify as an Incentive Stock Option. 
 11.22 “Option” means an option to
purchase Common Stock. 
 11.23 “Other Stock-Based Awards” means other Awards of shares of Common Stock, and other
Awards that are valued in whole or in part by reference to, or are otherwise based on, shares of Common Stock or other property. 
 11.24
“Participant” means a Service Provider who has been granted an Award under the Plan. 
 11.25
“Plan” means this 2017 Equity Incentive Plan. 
 11.26 “Publicly Listed Company” means that
the Company or its successor (i) is required to file periodic reports pursuant to Section 12 of the Exchange Act and (ii) the Common Stock is listed on one or more National Securities Exchanges (within the meaning of the Exchange Act)
or is quoted on NASDAQ or a successor interdealer quotation system. 
 11.27 “Restricted Stock” means Common Stock
awarded to a Participant pursuant to Section 6.1 hereof that is subject to certain vesting conditions and other restrictions. 
 11.28
“Restricted Stock Unit” means an unfunded, unsecured right to receive, on the applicable settlement date, one share of Common Stock or an amount in cash or other consideration determined by the Administrator equal to
the value thereof as of such payment date, which right may be subject to certain vesting conditions and other restrictions. 
 11.29
“Section 409A” means Section 409A of the Code and all regulations, guidance, compliance programs and other interpretative authority thereunder. 

11.30 “Securities Act” means the Securities Act of 1933, as amended from time to time. 

11.31 “Service Provider” means an Employee, Consultant or Director. 

11.32 “Termination of Service” means the date the Participant ceases to be a Service Provider. 

* * * * * 

  
 16 













 
OMEGA THERAPEUTICS, INC. 

2017 EQUITY INCENTIVE PLAN 


CALIFORNIA SUPPLEMENT 

This supplement is intended to satisfy the requirements of Section 25102(o) of the California Corporations Code and the regulations
issued thereunder (“Section 25102(o)”). Notwithstanding anything to the contrary contained in the Plan and except as otherwise determined by the Administrator, the provisions set forth in this
supplement shall apply to all Awards granted under the Plan to a Participant who is a resident of the State of California on the date of grant (a “California Participant”) and which are intended to be exempt from registration
in California pursuant to Section 25102(o), and otherwise to the extent required to comply with applicable law (but only to such extent). Definitions in the Plan are applicable to this supplement. 

1. Limitation on Securities Issuable under the Plan. The amount of securities issued pursuant to the Plan shall not exceed the amounts
permitted under section 260.140.45 of the California code of regulations to the extent applicable. 
 2. Additional Limitations For
Grants. The terms of all Awards shall comply, to the extent applicable, with Section 260.140.41 and 260.140.42 of the California code of regulations. 

3. Additional Requirement to Provide Information to California Participants. The Company shall provide to each California
Participant, not less frequently than annually, copies of annual financial statements (which need not be audited). The company shall not be required to provide such statements to key persons whose duties in connection with the company assure their
access to equivalent information. In addition, this information requirement shall not apply to any plan or agreement that complies with all conditions of Rule 701 of the Securities Act of 1933, as amended; provided that for purposes of determining
such compliance, any registered domestic partner shall be considered a “family member” as that term is defined in Rule 701.  

* * * * * 












 
OMEGA THERAPEUTICS, INC. 

2017 EQUITY INCENTIVE PLAN 


STOCK OPTION GRANT NOTICE 

Omega Therapeutics, Inc. (the “Company”), pursuant to its 2017 Equity Incentive Plan, as amended from time to time
(the “Plan”), has granted to the participant set forth below (“Participant”), an Option to purchase the number of shares of the Company’s Common Stock (referred to herein as
“Shares”) set forth below. The Option is subject to all of the terms and conditions as set forth herein and in the Stock Option Agreement attached hereto as Exhibit A (the “Stock Option
Agreement”) and the Plan, each of which is incorporated herein by reference. Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Stock Option Grant Notice and the Stock Option
Agreement. 
  

			
	Participant:	  	
		
	Grant Date:	  	
		
	Vesting Commencement Date:	  	
		
	Exercise Price per Share:	  	
		
	Total Exercise Price:	  	
		
	Total Number of Shares Subject to Option:	  	
		
	Expiration Date:	  	
		
	Type of Option	  	 [Incentive Stock Option/Non-Qualified Stock
Option]

		
	Vesting Schedule:	  	

 By his or her signature and the Company’s signature below, Participant agrees to be bound by the terms
and conditions of the Plan, the Stock Option Agreement and this Grant Notice. Participant has reviewed the Stock Option Agreement, the Plan and this Grant Notice in their entirety, has had an opportunity to obtain the advice of counsel prior to
executing this Grant Notice and fully understands all provisions of this Grant Notice, the Stock Option Agreement and the Plan. Participant hereby agrees to accept as binding, conclusive and final all decisions or interpretations of the
Administrator of the Plan upon any questions arising under the Plan or the Option. 
  

			
	OMEGA THERAPEUTICS, INC.	  	PARTICIPANT
		
	By:      ____________________________________	  	_____________________________________
	Name: ____________________________________	  	[Participant Name]
	Title:  ____________________________________	  	


  
 A- 













 Exhibit A 

STOCK OPTION AGREEMENT 

Omega Therapeutics, Inc. (the “Company”) has granted to Participant an Option under the Company’s 2017 Equity
Incentive Plan, as amended from time to time (the “Plan”), to purchase the number of Shares indicated in the Stock Option Grant Notice (“Grant Notice”) to which this Stock Option Agreement (this
“Agreement”) is attached. 
 ARTICLE I. 

GENERAL 
 1.2 Defined
Terms. Capitalized terms not specifically defined herein shall have the meanings specified in the Plan and the Grant Notice. 
 1.3
Incorporation of Terms of Plan. The Option is subject to the terms and conditions of the Plan which are incorporated herein by reference. In the event of a conflict between the terms of the Agreement and the Plan, the terms of the Plan shall
control. 
 1.4 Grant of Option. In consideration of Participant’s past and/or continued employment with or service to the
Company or a parent or subsidiary and for other good and valuable consideration, effective as of the grant date set forth in the Grant Notice (the “Grant Date”), the Company irrevocably grants to Participant an Option to
purchase any part or all of an aggregate of the number of Shares set forth in the Grant Notice, upon the terms and conditions set forth in the Plan and this Agreement. Unless designated as a Non-Qualified
Stock Option in the Grant Notice, the Option shall be an Incentive Stock Option to the maximum extent permitted by law. 
 ARTICLE II.

 PERIOD OF EXERCISABILITY 

2.1 Vesting; Commencement of Exercisability. 

(a) Subject to Sections 2.1(b) and 2.3, the Option shall become vested and exercisable in such amounts and at such times as are set forth in
the vesting schedule in the Grant Notice (the “Vesting Schedule”), except that any Share as to which the Option would be fractionally vested will be accumulated and will vest and become exercisable only when a whole Share has
accumulated. 
 (b) Unless otherwise determined by the Administrator, any portion of the Option that has not become vested and exercisable
on or prior to the date of Participant’s Termination of Service shall be forfeited on the date of Participant’s Termination of Service and shall not thereafter become vested or exercisable. 

2.2 Duration of Exercisability. The installments provided for in the Vesting Schedule are cumulative. Each such installment which
becomes vested and exercisable pursuant to the Vesting Schedule shall remain vested and exercisable until it becomes unexercisable under Section 2.3 or pursuant to the terms of the Plan. Once the Option becomes unexercisable, it shall be
forfeited immediately. 
 2.3 Expiration of Option. The Option may not be exercised to any extent by anyone after the first to occur
of the following events: 
 (a) The Expiration Date set forth in the Grant Notice; 

  
 A-1 













 (b) The expiration of three months following the date of Participant’s Termination of
Service, unless such Termination of Service occurs by reason of Participant’s death, Disability or Cause; 
 (c) The expiration of one
year following the date of Participant’s Termination of Service by reason of Participant’s death or Disability; or 
 (d) The date
of Participant’s Termination of Service for Cause. 
 Participant acknowledges that an Incentive Stock Option exercised more than three
months after Participant’s termination of status as an Employee, other than by reason of death or Disability, will be taxed as a Non-Qualified Stock Option. 

“Cause,” means “Cause” (or any term of similar effect) as defined in Participant’s employment agreement with the
Company if such an agreement exists and contains a definition of Cause (or term of similar effect), or, if no such agreement exists or such agreement does not contain a definition of Cause (or term of similar effect), then Cause shall include, but
not be limited to: (i) Participant’s unauthorized use or disclosure of confidential information or trade secrets of the Company or any material breach of a written agreement between Participant and the Company, including without limitation
a material breach of any employment, confidentiality, non-compete, non-solicit or similar agreement; (ii) Participant’s commission of, indictment for or the
entry of a plea of guilty or nolo contendere by Participant to, a felony under the laws of the United States or any state thereof or any crime involving dishonesty or moral turpitude (or any similar crime in any jurisdiction outside the
United States); (iii) Participant’s negligence or willful misconduct in the performance of Participant’s duties or Participant’s willful or repeated failure or refusal to substantially perform assigned duties; (iv) any act of
fraud, embezzlement, material misappropriation or dishonesty committed by Participant against the Company; or (v) any acts, omissions or statements by Participant which the Company determines to be materially detrimental or damaging to the
reputation, operations, prospects or business relations of the Company. 
 2.4 Special Tax Consequences. If the Option is intended to
be an Incentive Stock Option, Participant acknowledges that, to the extent that the aggregate fair market value (determined as of the time the Option is granted) of all Shares with respect to which Incentive Stock Options, including, without
limitation, the Option, are first exercisable for the first time by Participant in any calendar year exceeds $100,000 (or such other limitation as imposed by Section 422(d) of the Code), the Option and such other options (or the applicable
portion thereof) shall be treated as not qualifying under Section 422 of the Code but rather shall be considered Non-Qualified Stock Options. Participant further acknowledges that the rule set forth in
the preceding sentence shall be applied by taking Options and other “incentive stock options” into account in the order in which they were granted. 

ARTICLE III. 
 EXERCISE
OF OPTION 
 3.1 Person Eligible to Exercise. During the lifetime of Participant, only Participant may exercise the Option or any
portion thereof. After the death of Participant, any exercisable portion of the Option may, prior to the time when the Option becomes unexercisable under Section 2.3, be exercised by Participant’s personal representative or by any person
empowered to do so under the deceased Participant’s will or under the then applicable laws of descent and distribution. 
 3.2
Partial Exercise. Any exercisable portion of the Option or the entire Option, if then wholly exercisable, may be exercised in whole or in part at any time prior to the time when the Option or portion thereof becomes unexercisable under
Section 2.3. 

  
 A-2 













 3.3 Manner of Exercise. The Option, or any exercisable portion thereof, may be
exercised solely by delivery to the Secretary of the Company or the Secretary’s office, or such other place as may be determined by the Administrator, of all of the following prior to the time when the Option or such portion thereof becomes
unexercisable under Section 2.3: 
 (a) An exercise notice in substantially in the form attached as Exhibit B to the Grant Notice (or
such other form as is prescribed by the Administrator) (the “Exercise Notice”) in writing signed by Participant or any other person then entitled to exercise the Option or portion thereof, stating that the Option or portion
thereof is thereby exercised, such notice complying with all applicable rules established by the Administrator; and 
 (b) Full payment for
Shares with respect to which the Option or portion thereof is exercised in accordance with Section 5.6 of the Plan; and 
 (c) The
receipt by the Company of full payment for any applicable withholding tax in cash, by wire transfer of immediately available funds, by check or in such other form as is permitted by the Plan; and 

(d) In the event the Option or portion thereof shall be exercised pursuant to Section 3.1 by any person or persons other than
Participant, appropriate proof of the right of such person or persons to exercise the Option. 
 ARTICLE IV. 

OTHER PROVISIONS 
 4.1
Restrictive Legends and Stop-Transfer Orders. 
 (a) Participant agrees that, in order to ensure compliance with the restrictions
referred to herein, the Company may issue appropriate “stop transfer” instructions to its transfer agent, if any, and that, if the Company transfers its own securities, it may make appropriate notations to the same effect in its own
records. 
 (b) The Company shall not be required: (i) to transfer on its books any Shares that have been sold or otherwise transferred
in violation of any of the provisions of this Agreement, or (ii) to treat as owner of such Shares or to accord the right to vote or pay dividends to any purchaser or other transferee to whom such shares shall have been so transferred. 

4.2 Notices. Any notice to be given under the terms of this Agreement to the Company shall be addressed to the Company at its principal
executive offices in care of the Secretary of the Company, and any notice to be given to Participant shall be addressed to Participant at the most recent address for Participant shown in the Company’s records. By a notice given pursuant to this
Section 4.2, either party may hereafter designate a different address for notices to be given to that party. Any notice which is required to be given to Participant shall, if Participant is then deceased, be given to the person entitled to
exercise his or her Option by written notice under this Section 4.2. Any notice shall be deemed duly given when sent via email or when sent by certified mail (return receipt requested) and deposited (with postage prepaid) in a post office or
branch post office regularly maintained by the United States Postal Service. 
 4.3 Titles. Titles are provided herein for
convenience only and are not to serve as a basis for interpretation or construction of this Agreement. 

  
 A-3 













 4.4 Governing Law; Severability. This Agreement and the Exercise Notice shall be
administered, interpreted and enforced under the laws of the State of Delaware, without regard to the conflicts of law principles thereof. Should any provision of this Agreement be determined by a court of law to be illegal or unenforceable, the
other provisions shall nevertheless remain effective and shall remain enforceable. 
 4.5 Conformity to Securities Laws. Participant
acknowledges that the Plan is intended to conform to the extent necessary with all provisions of the Securities Act and the Exchange Act and any and all regulations and rules promulgated by the Securities and Exchange Commission thereunder, and
state securities laws and regulations. Notwithstanding anything herein to the contrary, the Plan shall be administered, and the Option is granted and may be exercised, only in such a manner as to conform to such laws, rules and regulations. To the
extent permitted by applicable law, the Plan and this Agreement shall be deemed amended to the extent necessary to conform to such laws, rules and regulations. 

4.6 Successors and Assigns. The Company may assign any of its rights under this Agreement and the Exercise Notice to single or multiple
assignees, and this Agreement shall inure to the benefit of the successors and assigns of the Company. Subject to the restrictions on transfer herein set forth, this Agreement shall be binding upon Participant and his or her heirs, executors,
administrators, successors and assigns. 
 4.7 Entire Agreement. The Plan and this Agreement (including, without limitation, all
Exhibits hereto) constitute the entire agreement of the parties and supersede in their entirety all prior undertakings and agreements of the Company and Participant with respect to the subject matter hereof. 

4.8 Lock-Up Period. Participant agrees that Participant will not, without the prior written
consent of the managing underwriter, during the period commencing on the date of the final prospectus relating to an initial public offering of any of the Company’s securities and ending on the date specified by the Company and the managing
underwriter (such period not to exceed one hundred eighty (180) days, or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (1) the publication or other distribution of research
reports, and (2) analyst recommendations and opinions, including, but not limited to, the restrictions contained in FINRA Rule 2241 or NYSE Rule 472(f)(4)), (i) lend; offer; pledge; sell; contract to sell; sell any option or contract to
purchase; purchase any option or contract to sell; grant any option, right, or warrant to purchase; or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or exercisable or
exchangeable (directly or indirectly) for Common Stock held immediately before the effective date of the registration statement for such offering or (ii) enter into any swap or other arrangement that transfers to another, in whole or in part,
any of the economic consequences of ownership of such securities, whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of Common Stock or other securities, in cash, or otherwise. The foregoing
provisions of this Section shall apply only to an initial public offering of the Company’s securities and shall not apply to the sale of any shares to an underwriter pursuant to an underwriting agreement for such initial public offering. The
underwriters in connection with such registration are intended third-party beneficiaries of this Section and shall have the right, power, and authority to enforce the provisions hereof as though they were a party hereto. Participant further agrees
to execute such agreements as may be reasonably requested by the underwriters in connection with such registration that are consistent with this Section or that are necessary to give further effect thereto. 

* * * * * 

  
 A-4 













 TO STOCK OPTION AGREEMENT 

FORM OF EXERCISE NOTICE 

Effective as of today,
                ,
                , the undersigned (“Participant”) hereby elects to exercise Participant’s option to
purchase                  Shares of Omega Therapeutics, Inc. (the “Company”) under and pursuant to the
Omega Therapeutics, Inc. 2017 Equity Incentive Plan (the “Plan”) and the Stock Option Agreement dated
                , ____ (the “Option Agreement”). Capitalized terms used herein without definition shall
have the meanings given in the Option Agreement. 
  

			
	 Grant Date:
	  	__________________________________
		
	Number of Shares as to which Option is Exercised:	  	________________________________________
		
	 Exercise Price per Share:
	  	$____________
		
	 Total Exercise Price:
	  	$____________
		
	 Certificate to be issued in name of:
	  	_________________________________
		
	 Cash Payment delivered herewith:
	  	$______________ (Representing the full Exercise Price for the Shares, as well as any applicable withholding tax)
		
	 Type of Option:
	  	☐ Incentive Stock Option         ☐ Non-Qualified Stock Option

 1. Representations of Participant. 

(a) Participant acknowledges that Participant has received, read and understood the Plan and the Option Agreement. Participant agrees to abide
by and be bound by their terms and conditions. 
 (b) Participant acknowledges that Participant is purchasing the Shares for
Participant’s own account for investment only, and not with a view to, or for sale in connection with, any distribution of the Shares in violation of the Securities Act of 1933, as amended (the “Securities Act”), or any
rule or regulation under the Securities Act. 
 (c) Participant has had such opportunity as Participant has deemed adequate to obtain from
representatives of the Company such information as is necessary to permit Participant to evaluate the merits and risks of Participant’s investment in the Company. 

(d) Participant 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. 
 (e) Participant 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. 
 (f) Participant
understands that (i) the Shares have not been registered under the Securities Act and are “restricted securities” within the meaning of Rule 144 under the Securities Act, (ii) the Shares cannot be sold, transferred or otherwise
disposed of unless they are subsequently registered under the Securities Act or an exemption from registration is then available; (iii) in any event, the exemption from registration under Rule 144 will not be available for at least one year and
even then will not be available unless a public market then exists for the Common Stock, adequate information concerning the Company is then available to the public, and other terms and conditions of Rule 144 are complied with; and (iv) there
is now no registration statement on file with the Securities and Exchange Commission with respect to any stock of the Company and the Company has no obligation or current intention to register the Shares under the Securities Act. 

  
 A-5 













 2. Tax Consultation. Participant understands that Participant may suffer adverse tax
consequences as a result of Participant’s purchase or disposition of the Shares. Participant represents that Participant has consulted with any tax consultants Participant deems advisable in connection with the purchase or disposition of the
Shares and that Participant is not relying on the Company for any tax advice. Participant is relying solely on such advisors and not on any statements or representations of the Company or any of its agents. Participant understands that Participant
(and not the Company) shall be responsible for Participant’s tax liability that may arise as a result of this investment or the transactions contemplated by this Agreement. 

3. Restrictive Legends and Stop-Transfer Orders. 

(a) Legends. Participant understands and agrees that the Company shall cause any certificates issued evidencing the Shares to have the
legends set forth below or legends substantially equivalent thereto, together with any other legends that may be required by state or federal securities laws: 

THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (“ACT”), NOR HAVE THEY BEEN
REGISTERED OR QUALIFIED UNDER THE SECURITIES LAWS OF ANY STATE. NO TRANSFER OF SUCH SECURITIES WILL BE PERMITTED UNLESS A REGISTRATION STATEMENT UNDER THE ACT IS IN EFFECT AS TO SUCH TRANSFER, THE TRANSFER IS MADE IN ACCORDANCE WITH RULE 144 UNDER
THE ACT, OR IN THE OPINION OF COUNSEL (WHICH MAY BE COUNSEL FOR THE COMPANY) REGISTRATION UNDER THE ACT IS UNNECESSARY IN ORDER FOR SUCH TRANSFER TO COMPLY WITH THE ACT AND WITH APPLICABLE STATE SECURITIES LAWS. 

THE SHARES REPRESENTED BY THIS CERTIFICATE MAY BE TRANSFERRED ONLY IN ACCORDANCE WITH THE TERMS OF AN AGREEMENT BETWEEN THE COMPANY AND THE
STOCKHOLDER, A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY. SUCH TRANSFER RESTRICTIONS ARE BINDING ON TRANSFEREES OF THESE SHARES. 

(b) Participant agrees that, in order to ensure compliance with the restrictions referred to herein, the Company may issue appropriate
“stop transfer” instructions to its transfer agent, if any, and that, if the Company transfers its own securities, it may make appropriate notations to the same effect in its own records. 

(c) The Company shall not be required (i) to transfer on its books any Shares that have been sold or otherwise transferred in violation
of any of the provisions of this Agreement or (ii) to treat as owner of such Shares or to accord the right to vote or pay dividends to any purchaser or other transferee to whom such Shares shall have been so transferred. 

  
 A-6 













 4. Notices. Any notice required or permitted hereunder shall be given in accordance
with the provisions set forth in Section 4.2 of the Option Agreement. 
 5. Further Instruments. Participant hereby agrees to
execute such further instruments and to take such further action as the Company requests to carry out the purposes and intent of this Agreement and the Plan, including, without limitation, restrictions on the transferability of shares of Common
Stock, the right of the Company to repurchase shares of Common Stock, the right of the Company to require that shares of Common Stock be transferred in the event of certain transactions, tag-along rights,
bring-along rights, redemption and co-sale rights and voting requirements in accordance with Section 10.15 of the Plan. 

6. Entire Agreement. The Plan and Option Agreement are incorporated herein by reference. This Agreement, the Plan and the Option
Agreement constitute the entire agreement of the parties and supersede in their entirety all prior undertakings and agreements of the Company and Participant with respect to the subject matter hereof. 

 

			
	 ACCEPTED BY:
 OMEGA THERAPEUTICS,
INC.
	  	 SUBMITTED BY:

PARTICIPANT

		
	By:        __________________________________________	  	__________________________________________
	Name:  __________________________________________	  	[Participant Name]
	Title:    __________________________________________	  	


  
 A-7 













 
OMEGA THERAPEUTICS, INC. 

2017 EQUITY INCENTIVE PLAN 


RESTRICTED STOCK GRANT NOTICE 

The participant set forth below (“Participant”) has been granted Restricted Stock, subject to the terms and conditions
of the Omega Therapeutics, Inc. 2017 Equity Incentive Plan, as amended from time to time (the “Plan”), and this Restricted Stock Agreement, which includes the terms in this Grant Notice (the “Grant
Notice”) and Exhibit A attached hereto (collectively, this “Agreement”). Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Agreement. 

 

			
	Participant:	  	
		
	Grant Date:	  	
		
	Vesting Commencement Date:	  	
		
	Total Number of Shares of Restricted Stock:	  	
		
	Type of Restricted Stock:	  	Common Stock
		
	Vesting Schedule:	  	

 Both the Company and Participant acknowledge and agree that this Agreement and the Plan constitute the entire
agreement between the Company and Participant regarding the terms and conditions of the Restricted Stock awarded hereunder, and that the foregoing supersede all prior communications, agreements, and understandings, written or oral, with respect to
the terms and conditions of such Restricted Stock. ACCORDINGLY, PLEASE BE SURE TO READ ALL OF THIS AGREEMENT (INCLUDING THE GRANT NOTICE AND APPENDIX A) AND THE PLAN. 
  

									
	OMEGA THERAPEUTICS, INC.:	 		 	 PARTICIPANT



									
				
	By:	 	  
	 		 	  

				
	Name:	 	  
	 		 	[Participant Name]
				
	Title:	 	  
	 		 	













 Exhibit A 

RESTRICTED STOCK AGREEMENT 

As evidenced by this Agreement, the Company has awarded to Participant the number of shares of Restricted Stock under the Plan set forth in
the Grant Notice. 
 ARTICLE I. 

GENERAL 
 1.1
Definitions. All capitalized terms used in this Agreement without definition shall have the meanings ascribed in the Plan and the Grant Notice.  

1.2 Incorporation of Terms. The Restricted Stock is subject to the terms and conditions of the Plan, which are incorporated herein by
reference. In the event of any inconsistency between the Plan and this Agreement, the terms of the Plan shall control. Participant hereby acknowledges receipt of a copy of the Plan and agrees to execute such further documents as may from time to
time be requested by the Company to implement the terms of the Plan, including, without limitation, restrictions on the transferability of shares of Common Stock, the right of the Company to repurchase shares of Common Stock, the right of the
Company to require that shares of Common Stock be transferred in the event of certain transactions, tag-along rights, bring-along rights, redemption and co-sale rights
and voting requirements in accordance with Section 10.15 of the Plan. 
 ARTICLE II. 

AWARD OF RESTRICTED STOCK 

2.1 Award of Restricted Stock. 

(a) Award. On the Grant Date, the Company issued to Participant the number of shares of Restricted Stock set forth in the Grant Notice
in consideration of Participant’s agreement to remain in the service or employ of the Company or one of its subsidiaries, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged. Such shares
of Restricted Stock and any dividends and distributions made or declared with respect to such shares, in each case, whether vested or unvested shall sometimes be referred to herein as “Shares.” 

(b) Book Entry Form; Certificates. At the sole discretion of the Administrator, the Shares will be issued in either
(i) uncertificated form, with the Shares recorded in the name of Participant in the books and records of the Company’s transfer agent with appropriate notations regarding the Restrictions; or (ii) certificate form subject to the terms
of Section 2.1(c). For purposes of this Agreement, “Restrictions” shall mean the forfeiture provision in Section 2.2 and the other restrictions set forth in this Agreement or the Plan. 

(c) Legend. Shares issued pursuant to this Agreement shall bear such legend or legends as shall be determined by the Administrator.

 (d) Escrow. The Secretary of the Company or such other escrow holder as the Company may appoint may retain physical custody of any
certificates representing the Shares until all of the Restrictions lapse or shall have been removed. 
 2.2 Restrictions. 

(a) Forfeiture. The Restricted Stock shall vest in accordance with the vesting schedule set forth on the Grant Notice. Except as
otherwise determined by the Administrator, any portion 

  
 A-1 













 
of the Restricted Stock which is not vested pursuant to the Grant Notice as of the date Participant incurs a Termination of Service shall automatically be forfeited by Participant on the date of
such Termination of Service without any additional consideration therefore and without any further action by the Company. 
 (b) Tax
Withholding; Conditions to Issuance of Certificates. Notwithstanding any other provision of this Agreement: 
 (i) Participant is
ultimately liable and responsible for all taxes owed in connection with the Restricted Stock, regardless of any action the Company or any of its subsidiaries takes with respect to any tax withholding obligations that arise in connection with the
Restricted Stock. Neither the Company nor any of its subsidiaries makes any representation or undertaking regarding the treatment of any tax withholding in connection with the awarding or vesting of the Restricted Stock or the subsequent sale of
shares. The Company and its subsidiaries do not commit and are under no obligation to structure the Restricted Stock to reduce or eliminate Participant’s tax liability. 

(ii) Prior to any tax withholding becoming due, Participant must make arrangements acceptable to the Administrator to satisfy such
withholding and must satisfy such tax withholdings when due. To the extent permitted by the Administrator, the Company (or the employing subsidiary) will withhold a portion of the shares of Restricted Stock that have an aggregate fair market value
sufficient to pay the minimum federal, state and local income, employment and any other applicable taxes required to withheld by the Company or the employing subsidiary with respect to the shares. Notwithstanding any contrary provision of this
Agreement, no vested Shares will be released from the Company unless and until satisfactory arrangements (as determined by the Administrator) will have been made by Participant with respect to the payment of any income and other taxes which the
Company determines must be withheld or collected as of the vesting date with respect to such Shares. In addition and to the maximum extent permitted by Applicable Law, the Company (or the employing subsidiary) has the right to retain from salary or
other amounts payable to Participant, cash having a value sufficient to satisfy any tax withholding obligations (based on minimum statutory rates) that are not satisfied by the withholding of otherwise deliverable Shares or any other arrangements
made by Participant. 
 2.2 Rights as Stockholder. Except as otherwise provided herein, upon the Grant Date, Participant shall have
all the rights of a stockholder with respect to the Shares, including without limitation the right to receive any cash or stock dividends or other distributions paid to or made with respect to the Shares, subject to the Restrictions herein. 

2.3 Retained Distributions. The Company will retain custody of all cash dividends (without interest) and other distributions
(“Retained Distributions”) made or declared with respect to the Restricted Stock (and such Retained Distributions will be subject to the Restrictions and the other terms and conditions under this Agreement that are applicable
to the Restricted Stock) until such time, if ever, as the Restricted Stock with respect to which such Retained Distributions shall have been made, paid or declared shall have become vested pursuant to the Grant Notice or, if earlier, tax withholding
is otherwise due with respect to such Restricted Stock. Retained Distributions will automatically be forfeited upon forfeiture of the share of Restricted Stock with respect to which the Retained Distributions were paid or declared. 

ARTICLE III. 
 OTHER
PROVISIONS 
 3.1 Section 83(b) Election. Participant understands that Section 83(a) of the Code taxes as ordinary income
the difference between the amount, if any, paid for the Shares and the fair market value of such Shares at the time the forfeiture provision on such Shares lapse or such Shares become 

  
 A-2 













 
transferable. Participant understands that, notwithstanding the preceding sentence, Participant may elect to be taxed at the time of the Grant Date, rather than at the time the forfeiture
provision or transferability restriction lapses, by filing an election under Section 83(b) of the Code (an “83(b) Election”) with the Internal Revenue Service within 30 days after the Grant Date. In the event Participant
files an 83(b) Election, Participant will recognize ordinary income in an amount equal to the difference between the amount, if any, paid for the Shares and the Fair Market Value of such Shares as of the Grant Date. Participant acknowledges that the
foregoing is only a summary of the effect of United States federal income taxation with respect to the Shares awarded hereunder, and does not purport to be complete. PARTICIPANT FURTHER ACKNOWLEDGES THAT THE COMPANY IS NOT RESPONSIBLE FOR FILING
PARTICIPANT’S 83(b) ELECTION, AND THE COMPANY HAS DIRECTED PARTICIPANT TO SEEK INDEPENDENT ADVICE REGARDING THE APPLICABLE PROVISIONS OF THE INTERNAL REVENUE CODE, THE INCOME TAX LAWS OF ANY MUNICIPALITY, STATE OR FOREIGN COUNTRY IN WHICH
PARTICIPANT MAY RESIDE, AND THE TAX CONSEQUENCES OF THIS AWARD AND PARTICIPANT’S PARTICIPATION IN THE PLAN. A sample 83(b) Election is attached hereto. 

3.2 Governing Law; Severability. This Agreement shall be administered, interpreted and enforced under the laws of the State of
Delaware, without regard to the conflicts of law principles thereof. Should any provision of this Agreement be determined by a court of law to be illegal or unenforceable, the other provisions shall nevertheless remain effective and shall remain
enforceable. 
 3.3 Notices. Any notice to be given under the terms of this Agreement to the Company shall be addressed to the
Company at its principal executive offices in care of the Secretary of the Company, and any notice to be given to Participant shall be addressed to Participant at the most recent address for Participant shown in the Company’s records. By a
notice given pursuant to this Section 3.3, either party may hereafter designate a different address for notices to be given to that party. Any notice shall be deemed duly given when sent via email or when sent by certified mail (return receipt
requested) and deposited (with postage prepaid) in a post office or branch post office regularly maintained by the United States Postal Service. 

3.4 Successors and Assigns. The Company may assign any of its rights under this Agreement to single or multiple assignees, and this
Agreement shall inure to the benefit of the successors and assigns of the Company. Subject to the restrictions on transfer herein set forth, this Agreement shall be binding upon Participant and his heirs, executors, administrators, successors and
assigns. 
 3.5 Lock-Up Period. Participant agrees that Participant will not, without the
prior written consent of the managing underwriter, during the period commencing on the date of the final prospectus relating to an initial public offering of any of the Company’s securities and ending on the date specified by the Company and
the managing underwriter (such period not to exceed one hundred eighty (180) days, or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (1) the publication or other
distribution of research reports, and (2) analyst recommendations and opinions, including, but not limited to, the restrictions contained in FINRA Rule 2241 or NYSE Rule 472(f)(4)), (i) lend; offer; pledge; sell; contract to sell; sell any
option or contract to purchase; purchase any option or contract to sell; grant any option, right, or warrant to purchase; or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or
exercisable or exchangeable (directly or indirectly) for Common Stock held immediately before the effective date of the registration statement for such offering or (ii) enter into any swap or other arrangement that transfers to another, in
whole or in part, any of the economic consequences of ownership of such securities, whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of Common Stock or other securities, in cash, or otherwise. The
foregoing provisions of this Section shall apply only to an initial public offering of the Company’s 

  
 A-3 













 
securities and shall not apply to the sale of any shares to an underwriter pursuant to an underwriting agreement for such initial public offering. The underwriters in connection with such
registration are intended third-party beneficiaries of this Section and shall have the right, power, and authority to enforce the provisions hereof as though they were a party hereto. Participant further agrees to execute such agreements as may be
reasonably requested by the underwriters in connection with such registration that are consistent with this Section or that are necessary to give further effect thereto. 

* * * * * 

  
 A-4 













 ELECTION UNDER SECTION 83(B) 

OF THE INTERNAL REVENUE CODE OF 1986 

The undersigned taxpayer hereby elects, pursuant to Section 83(b) of the Internal Revenue Code of 1986, as amended, to include in
taxpayer’s gross income for the current taxable year the amount of any compensation taxable to taxpayer in connection with taxpayer’s receipt of the property described below 

 

	1.	 The name, address, taxpayer identification number and taxable year of the undersigned are as follows:



  

	 	NAME:	 


  

	 	ADDRESS:	 


  

	 	SOCIAL	 SECURITY NO.: 


  

	 	TAXABLE	
YEAR:                    201  
   


  

	2.	 The property with respect to which the election is made is described as follows:
                 shares (the “Shares”) of the common stock of Omega Therapeutics, Inc. (the “Company”). 



 

	3.	 The date on which the property was transferred is:
                    , 201    . 


  

	4.	 The property is subject to the following restrictions: 



The Shares may not be transferred and are subject to forfeiture under the terms of an agreement between the taxpayer and the Company. These
restrictions lapse upon the satisfaction of certain conditions contained in such agreement. 
  

	5.	 The fair market value at the time of transfer, determined without regard to any restriction other than a
restriction which by its terms will never lapse, of the transferred property is: $                    . 



 

	6.	 The amount (if any) paid for such property is:
$                    . 



The undersigned has submitted a copy of this statement to the person for whom the services were performed in connection with the
undersigned’s receipt of the above-described property. The transferee of such property is the person performing the services in connection with the transfer of said property. 

The undersigned understands that the foregoing election may not be revoked except with the consent of the Commissioner. 

 

			
	Dated:                     ,         	 	  

		 	Taxpayer