Document:

EX-10.34

 Exhibit 10.34 

CARIBOU BIOSCIENCES, INC. 

2013 EQUITY INCENTIVE PLAN 

(As amended and restated as of April 3, 2019) 

1. Purposes of the Plan. The purposes of this Plan are: 
  

	 	•	 	 to attract and retain the best available personnel for positions of substantial responsibility,

  

	 	•	 	 to provide additional incentive to Employees, Directors and Consultants, and 

 

	 	•	 	 to promote the success of the Company’s business. 

The Plan permits the grant of Incentive Stock Options, Nonstatutory Stock Options, Stock Appreciation Rights, Restricted Stock and Restricted
Stock Units. 
 2. Definitions. As used herein, the following definitions will apply: 

(a) “Administrator” means the Board or any of its Committees as will be administering the Plan, in accordance with
Section 4 of the Plan. 
 (b) “Applicable Laws” means all applicable laws, rules, regulations and requirements,
including, but not limited to, the requirements relating to the administration of equity-based awards under U.S. state corporate laws, U.S. federal and state securities laws, the Code, any stock exchange or quotation system on which the Common Stock
is listed or quoted and the applicable laws of any foreign country or jurisdiction where Awards are, or will be, granted under the Plan or Participants reside or provide services, as such laws, rules, and regulations shall be in effect from time to
time. 
 (c) “Award” means, individually or collectively, a grant under the Plan of Options, Stock Appreciation Rights,
Restricted Stock, or Restricted Stock Units. 
 (d) “Award Agreement” means the written or electronic agreement setting
forth the terms and provisions applicable to each Award granted under the Plan. The Award Agreement is subject to the terms and conditions of the Plan. 

(e) “Board” means the Board of Directors of the Company. 

(f) “Change in Control” means the occurrence of any of the following events: 

(i) Change in Ownership of the Company. A change in the ownership of the Company which occurs on the date that any one person, or more
than one person acting as a group (“Person”), acquires ownership of the stock of the Company that, together with the stock held by such Person, constitutes more than 50% of the total voting power of the stock of the Company, except that
any change in the ownership of the stock of the Company as a result of a private financing of the Company that is approved by the Board will not be considered a Change in Control and, if any Person is considered to be in effective control of the
Company, the acquisition of additional control of the Company by the same Person will not be considered a Change in Control; or 
 (ii)
Change in Effective Control of the Company. If the Company has a class of securities registered pursuant to Section 12 of the Exchange Act, a change in the effective control of the Company which occurs on the date that a majority of
members of the Board is replaced during any twelve (12) month period by Directors whose appointment or election is not endorsed by a majority of the members of the Board prior to the date of the appointment or election; or 

 (iii) Change in Ownership of a Substantial Portion of the Company’s Assets. A
change in the ownership of a substantial portion of the Company’s assets which occurs on the date that any Person acquires (or has acquired during the twelve (12) month period ending on the date of the most recent acquisition by such
person or persons) assets from the Company that have a total gross fair market value equal to or more than 50% of the total gross fair market value of all of the assets of the Company immediately prior to such acquisition or acquisitions. For
purposes of this subsection (iii), gross fair market value means the value of the assets of the Company, or the value of the assets being disposed of, determined without regard to any liabilities associated with such assets. 

For purposes of this Section 2(f), persons will be considered to be acting as a group if they are owners of a corporation that enters
into a merger, consolidation, purchase or acquisition of stock, or similar business transaction with the Company. 
 Notwithstanding the
foregoing, a transaction will not be deemed a Change in Control unless the transaction qualifies as a change in control event within the meaning of Code Section 409A, as it has been and may be amended from time to time, and any proposed or
final Treasury Regulations and Internal Revenue Service guidance that has been promulgated or may be promulgated thereunder from time to time. 

Further and for the avoidance of doubt, a transaction will not constitute a Change in Control if: (i) its sole purpose is to change the
jurisdiction of the Company’s incorporation, or (ii) its sole purpose is to create a holding company that will be owned in substantially the same proportions by the persons who held the Company’s securities immediately before such
transaction. 
 (g) “Code” means the Internal Revenue Code of 1986, as amended. Any reference to a section of the Code herein will
be a reference to any successor or amended section of the Code. 
 (h) “Committee” means a committee of Directors or of other
individuals appointed by the Board, or by the compensation committee of the Board, in compliance with Applicable Laws and in accordance with Section 4 hereof. 

(i) “Common Stock” means the common stock of the Company. -2- 

(j) “Company” means Caribou Biosciences, Inc., a Delaware corporation, or any successor thereto. 

(k) “Consultant” means any person or entity, including an advisor but not an Employee, that renders, or has rendered, services to
the Company or a Parent or Subsidiary and is compensated for such services. 
 (l) “Director” means a member of the Board. 

(m) “Disability” means total and permanent disability as defined in Code Section 22(e)(3), provided that in the case of Awards
other than Incentive Stock Options, the Administrator in its discretion may determine whether a permanent and total disability exists in accordance with uniform and non-discriminatory standards adopted by the
Administrator from time to time, provided, in making such determination, the Administrator shall do so in the manner required by, and consistent with, Section 25102(o) of the California Corporations Code to the extent the Company is relying
upon the exemption afforded thereby with respect to the Award. 
 (n) “Employee” means any person, including officers and
Directors, employed by the Company or any Parent or Subsidiary of the Company. Neither service as a Director nor payment of a director’s fee by the Company will be sufficient to constitute “employment” by the Company. 

(o) “Exchange Act” means the Securities Exchange Act of 1934, as amended. 

(p) “Exchange Program” means a program under which (i) outstanding Awards are surrendered or cancelled in exchange for Awards
of the same type (which may have higher or lower exercise prices and different terms), Awards of a different type, and/or cash, (ii) Participants would have the opportunity to transfer 

  
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any outstanding Awards to a financial institution or other person or entity selected by the Administrator, and/or (iii) the exercise price of an outstanding Award is reduced or increased.
The Administrator will determine the terms and conditions of any Exchange Program in its sole discretion. 
 (q) “Fair Market
Value” means, as of any date, the value of Common Stock determined as follows: 
 (i) If the Common Stock is listed on any established
stock exchange or a national market system, including without limitation the Nasdaq Global Select Market, the Nasdaq Global Market or the Nasdaq Capital Market of The Nasdaq Stock Market, its Fair Market Value will be the closing sales price for
such stock (or the closing bid, if no sales were reported) as quoted on such exchange or system on the day of determination, as reported in The Wall Street Journal or such other source as the Administrator deems reliable; 

(ii) If the Common Stock is regularly quoted by a recognized securities dealer but selling prices are not reported, the Fair Market Value of
a Share will be the mean between the high bid and low asked prices for the Common Stock on the day of determination (or, if no bids and asks were reported on that date, as applicable, on the last trading date such bids and asks were 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 will be determined in good faith by the Administrator. 
 (r) “Incentive
Stock Option” means an Option that by its terms qualifies and is otherwise intended to qualify as an incentive stock option within the meaning of Code Section 422 and the regulations promulgated thereunder. 

(s) “Nonstatutory Stock Option” means an Option that by its terms does not qualify or is not intended to qualify as an Incentive
Stock Option. 
 (t) “Option” means a stock option granted pursuant to the Plan. 

(u) “Parent” means a “parent corporation,” whether now or hereafter existing, as defined in Code Section 424(e). 

(v) “Participant” means the holder of an outstanding Award or Shares received pursuant to an Award. 

(w) “Period of Restriction” means the period during which the transfer of Shares of Restricted Stock are subject to
restrictions and therefore, the Shares are subject to a substantial risk of forfeiture. Such restrictions may be based on the passage of time, the achievement of target levels of performance, or the occurrence of other events as determined by the
Administrator. 
 (x) “Plan” means this Amended and Restated 2013 Equity Incentive Plan, as the same may be amended and/or
restated from time to time. 
 (y) “Restricted Stock” means Shares issued pursuant to an Award of Restricted Stock under
Section 8 of the Plan, or issued pursuant to the early exercise of an Option. 
 (z) “Restricted Stock Unit” means a
bookkeeping entry representing an amount equal to the Fair Market Value of one Share, granted pursuant to Section 9. Each Restricted Stock Unit represents an unfunded and unsecured obligation of the Company. 

(aa) “Service Provider” means an Employee, Director or Consultant. 

  
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 (bb) “Share” means a share of the Common Stock, as adjusted in accordance
with Section 14 of the Plan. 
 (cc) “Stock Appreciation Right” means an Award, granted alone or in connection with an
Option, that pursuant to Section 7 is designated as a Stock Appreciation Right. 
 (dd) “Subsidiary” means a
“subsidiary corporation,” whether now or hereafter existing, as defined in Code Section 424(f). 
 3. Stock Subject to the
Plan. 
 (a) Stock Subject to the Plan. Subject to the provisions of Section 14 of the Plan, the maximum aggregate number of
Shares that may be subject to Awards and sold under the Plan is equal to the aggregate of 4,005,903 Shares, plus up to 250,000 Shares subject to stock options or similar awards granted under the Company’s terminated 2012 Stock Option/Stock
Issuance Plan (the “2012 Plan”) that expire or otherwise terminate without having been exercised in full and Shares issued pursuant to awards granted under the 2012 Plan that are forfeited to or repurchased by the Company. The
Shares may be authorized but unissued, or reacquired Common Stock. 
 (b) Lapsed Awards. If an Award expires or becomes unexercisable
without having been exercised in full, is surrendered pursuant to an Exchange Program, or, with respect to Restricted Stock or Restricted Stock Units, is forfeited to or repurchased by the Company at cost due to the failure to vest, the unpurchased
Shares (or for Awards other than Options or Stock Appreciation Rights the forfeited or repurchased Shares) which were subject thereto will become available for future grant or sale under the Plan (unless the Plan has terminated). With respect to
Stock Appreciation Rights, only Shares actually issued pursuant to a Stock Appreciation Right will cease to be available under the Plan; all remaining Shares under Stock Appreciation Rights will remain available for future grant or sale under the
Plan (unless the Plan has terminated). Shares that have actually been issued under the Plan under any Award will not be returned to the Plan and will not become available for future distribution under the Plan; provided, however, that if Shares
issued pursuant to Awards of Restricted Stock or Restricted Stock Units are repurchased by the Company at cost or are forfeited to the Company due to the failure to vest, such Shares will become available for future grant under the Plan. Shares used
to pay the exercise price of an Award or to satisfy the tax withholding obligations related to an Award will become available for future grant or sale under the Plan. To the extent an Award under the Plan is paid out in cash rather than Shares, such
cash payment will not result in reducing the number of Shares available for issuance under the Plan. Notwithstanding the foregoing and, subject to adjustment as provided in Section 14, the maximum number of Shares that may be issued upon the
exercise of Incentive Stock Options will equal the aggregate Share number stated in Section 3, plus, to the extent allowable under Code Section 422 and the Treasury Regulations promulgated thereunder, any Shares that become available for
issuance under the Plan pursuant to Section 3(b). 
 (c) Share Reserve. The Company, during the term of this Plan, will at all
times reserve and keep available such number of Shares as will be sufficient to satisfy the requirements of the Plan. 
 4.
Administration of the Plan. 
 (a) Procedure. 

(i) Multiple Administrative Bodies. Different Committees with respect to different groups of Service Providers may administer the
Plan. 
 (ii) Other Administration. Other than as provided above, the Plan will be administered by (A) the Board or (B) a
Committee, which Committee will be constituted to satisfy Applicable Laws. 
 (b) Powers of the Administrator. Subject to the
provisions of the Plan, and in the case of a Committee, subject to the specific duties delegated by the Board to such Committee, the Administrator will have the authority, in its discretion: 

(i) to determine the Fair Market Value; 

  
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 (ii) to select the Service Providers to whom Awards may be granted hereunder; 

(iii) to determine the number of Shares to be covered by each Award granted hereunder; 

(iv) to approve forms of Award Agreements for use under the Plan; 

(v) to determine the terms and conditions, not inconsistent with the terms of the Plan, of any Award granted hereunder; such terms and
conditions include, but are not limited to, the exercise price, the time or times when Awards may be exercised (which may be based on performance criteria), any vesting acceleration or waiver of forfeiture restrictions, and any restriction or
limitation regarding any Award or the Shares relating thereto, based in each case on such factors as the Administrator will determine; 

(vi) to institute and determine the terms and conditions of an Exchange Program; 

(vii) to construe and interpret the terms of the Plan and Awards granted pursuant to the Plan; 

(viii) to prescribe, amend and rescind rules and regulations relating to the Plan; 

(ix) to approve addenda pursuant to Section 24 below or to grant Awards to, or to modify the terms of, any outstanding Award Agreement
or any agreement related to any Restricted Stock or other Shares issued under the Plan and held by Participants who are foreign nationals or employed outside of the U.S. with such terms and conditions as the Administrator deems necessary or
appropriate to accommodate differences in local law, tax policy or custom which deviate from the terms and conditions set forth in this Plan to the extent necessary or appropriate to accommodate such differences; and 

(x) to modify or amend each Award (subject to Section 19(c) of the Plan), including but not limited to the discretionary authority to
extend the post-termination exercisability period of Awards and to extend the maximum term of an Option (subject to Section 6(d)); 

(xi) to allow Participants to satisfy tax obligations in any manner prescribed in Section 15; 

(xii) to authorize any person to execute on behalf of the Company any instrument required to effect the grant of an Award previously granted
by the Administrator; 
 (xiii) to allow a Participant to defer the receipt of the payment of cash or the delivery of Shares that otherwise
would be due to such Participant under an Award; and 
 (xiv) to make all other determinations deemed necessary or advisable for
administering the Plan. 
 (c) Effect of Administrator’s Decision. The Administrator’s decisions, determinations and
interpretations will be final and binding on all Participants and any other holders of Awards. 
 5. Eligibility. Nonstatutory Stock
Options, Stock Appreciation Rights, Restricted Stock, and Restricted Stock Units may be granted to Service Providers. Incentive Stock Options may be granted only to Employees. 

  
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 6. Stock Options. 

(a) Grant of Options. Subject to the terms and provisions of the Plan, the Administrator, at any time and from time to time, may grant
Options in such amounts as the Administrator, in its sole discretion, will determine. 
 (b) Option Agreement. Each Award of an
Option will be evidenced by an Award Agreement that will specify the exercise price, the term of the Option, the number of Shares subject to the Option, the exercise restrictions, if any, applicable to the Option, and such other terms and conditions
as the Administrator, in its sole discretion, will determine. 
 (c) Limitations. Each Option will be designated in the Award
Agreement as either an Incentive Stock Option or a Nonstatutory Stock Option. Notwithstanding such designation, however, to the extent that the aggregate Fair Market Value of the Shares with respect to which Incentive Stock Options are exercisable
for the first time by the Participant during any calendar year (under all plans of the Company and any Parent or Subsidiary) exceeds one hundred thousand dollars ($100,000), such Options will be treated as Nonstatutory Stock Options. For purposes of
this Section 6(c), Incentive Stock Options will be taken into account in the order in which they were granted, the Fair Market Value of the Shares will be determined as of the time the Option with respect to such Shares is granted, and
calculation will be performed in accordance with Code Section 422 and Treasury Regulations promulgated thereunder. 
 (d) Term of
Option. The term of each Option will be stated in the Award Agreement; provided, however, that the term will be no more than ten (10) years from the date of grant thereof. In the case of an Incentive Stock Option granted to a Participant
who, at the time the Incentive Stock Option is granted, owns stock representing more than ten percent (10%) of the total combined voting power of all classes of stock of the Company or any Parent or Subsidiary, the term of the Incentive Stock Option
will be five (5) years from the date of grant or such shorter term as may be provided in the Award Agreement. 
 (e) Option Exercise
Price and Consideration. 
 (i) Exercise Price. The per Share exercise price for the Shares to be issued pursuant to the
exercise of an Option will be determined by the Administrator, but will be no less than one hundred percent (100%) of the Fair Market Value per Share on the date of grant. In addition, in the case of an Incentive Stock Option granted to an Employee
who owns stock representing more than ten percent (10%) of the voting power of all classes of stock of the Company or any Parent or Subsidiary, the per Share exercise price will be no less than one hundred ten percent (110%) of the Fair Market Value
per Share on the date of grant. Notwithstanding the foregoing provisions of this Section 6(e)(i), Options may be granted with a per Share exercise price of less than one hundred percent (100%) of the Fair Market Value per Share on the date of
grant pursuant to a transaction described in, and in a manner consistent with, Code Section 424(a). 
 (ii) Waiting Period and
Exercise Dates. At the time an Option is granted, the Administrator will fix the period within which the Option may be exercised and will determine any conditions that must be satisfied before the Option may be exercised. 

(iii) Form of Consideration. The Administrator will determine the acceptable form of consideration for exercising an Option, including
the method of payment. In the case of an Incentive Stock Option, the Administrator will determine the acceptable form of consideration at the time of grant. Such consideration may consist entirely of: (1) cash; (2) check; (3) promissory
note, to the extent permitted by Applicable Laws, (4) other Shares, provided that such Shares have a Fair Market Value on the date of surrender equal to the aggregate exercise price of the Shares as to which such Option will be exercised and
provided further that accepting such Shares will not result in any adverse accounting consequences to the Company, as the Administrator determines in its sole discretion; (5) consideration received by the Company under cashless exercise program
(whether through a broker or otherwise) implemented by the Company in connection with the Plan; (6) by net exercise, (7) such other consideration and method of payment for the issuance of Shares to the extent permitted by Applicable Laws,
or (8) any combination of the foregoing methods of payment. In making its determination as to the type of consideration to accept, the Administrator will consider if acceptance of such consideration may be reasonably expected to benefit the
Company. 

  
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 (f) Exercise of Option. 

(i) Procedure for Exercise; Rights as a Stockholder. Any Option granted hereunder will be exercisable according to the terms of the
Plan and at such times and under such conditions as determined by the Administrator and set forth in the Award Agreement. An Option may not be exercised for a fraction of a Share. 

An Option will be deemed exercised when the Company receives: (i) notice of exercise (in such form as the Administrator may specify from
time to time) from the person entitled to exercise the Option, and (ii) full payment for the Shares with respect to which the Option is exercised and full satisfaction of any applicable taxes, withholding, required deductions or other required
payments (or arrangements have been made to satisfy any such obligations), as determined by the Administrator, in its sole discretion. Full payment may consist of any consideration and method of payment authorized by the Administrator and permitted
by the Award Agreement and the Plan. Shares issued upon exercise of an Option will be issued in the name of the Participant or, if requested by the Participant, in the name of the Participant and his or her spouse. Until the Shares are issued (as
evidenced by the appropriate entry on the books of the Company or of a duly authorized transfer agent of the Company), no right to vote or receive dividends or any other rights as a stockholder will exist with respect to the Shares subject to an
Option, notwithstanding the exercise of the Option. The Company will issue (or cause to be issued) such Shares promptly after the Option is exercised. No adjustment will be made for a dividend or other right for which the record date is prior to the
date the Shares are issued, except as provided in Section 14 of the Plan. 
 Exercising an Option in any manner will decrease the
number of Shares thereafter available, both for purposes of the Plan and for sale under the Option, by the number of Shares as to which the Option is exercised. 

(ii) Termination of Relationship as a Service Provider. If a Participant ceases to be a Service Provider, other than upon the
Participant’s termination as the result of the Participant’s death or Disability, the Participant may exercise his or her Option within thirty (30) days of termination, or such longer period of time as is specified in the Award
Agreement (but in no event later than the expiration of the term of such Option as set forth in the Award Agreement) to the extent that the Option is vested. If after termination the Participant does not exercise his or her Option within the
applicable time period, the Option will terminate, and any then vested or unvested Shares covered by such Option will revert to the Plan. 

(iii) Disability of Participant. If a Participant ceases to be a Service Provider as a result of the Participant’s Disability,
the Participant may exercise his or her Option within six (6) months of termination, or such longer period of time as is specified in the Award Agreement (but in no event later than the expiration of the term of such Option as set forth in the
Award Agreement) to the extent the Option is vested. If after termination the Participant does not exercise his or her Option within the applicable time period, the Option will terminate, and any then vested or unvested Shares covered by such Option
will revert to the Plan. 
 (iv) Death of Participant. If a Participant dies while a Service Provider, the Option may be exercised
within six (6) months following the Participant’s death, or within such longer period of time as is specified in the Award Agreement (but in no event later than the expiration of the term of such Option as set forth in the Award Agreement)
to the extent that the Option is vested, by the Participant’s designated beneficiary, provided such beneficiary has been designated prior to the Participant’s death in a form acceptable to the Administrator. If no such beneficiary has been
designated by the Participant, then such Option may be exercised by the personal representative of the Participant’s estate or by the person(s) to whom the Option is transferred pursuant to the Participant’s will or in accordance with the
laws of descent and distribution. If the Option is not so exercised within the applicable time period, the Option will terminate, and any then vested or unvested Shares covered by such Option will revert to the Plan. 

7. Stock Appreciation Rights. 

(a) Grant of Stock Appreciation Rights. Subject to the terms and conditions of the Plan, a Stock Appreciation Right may be granted to
Service Providers at any time and from time to time as will be determined by the Administrator, in its sole discretion. 
 (b) Number of
Shares. The Administrator will have complete discretion to determine the number of Shares subject to any Award of Stock Appreciation Rights. 

  
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 (c) Exercise Price and Other Terms. The per Share exercise price for the Shares that
will determine the amount of the payment to be received upon exercise of a Stock Appreciation Right as set forth in Section 7(f) will be determined by the Administrator and will be no less than one hundred percent (100%) of the Fair Market
Value per Share on the date of grant. Otherwise, the Administrator, subject to the provisions of the Plan, will have complete discretion to determine the terms and conditions of Stock Appreciation Rights granted under the Plan. 

(d) Stock Appreciation Right Agreement. Each Stock Appreciation Right grant will be evidenced by an Award Agreement that will specify
the exercise price, the term of the Stock Appreciation Right, the conditions of exercise, and such other terms and conditions as the Administrator, in its sole discretion, will determine. 

(e) Expiration of Stock Appreciation Rights. A Stock Appreciation Right granted under the Plan will expire upon the date determined by
the Administrator, in its sole discretion, and set forth in the Award Agreement. Notwithstanding the foregoing, the rules of Section 6(d) relating to the maximum term and Section 6(f) relating to exercise also will apply to Stock
Appreciation Rights. 
 (f) Payment of Stock Appreciation Right Amount. Upon exercise of a Stock Appreciation Right, a Participant
will be entitled to receive payment from the Company in an amount determined by multiplying: 
 (i) The difference between the Fair Market
Value of a Share on the date of exercise over the exercise price; times 
 (ii) The number of Shares with respect to which the Stock
Appreciation Right is exercised. 
 At the discretion of the Administrator, the payment upon Stock Appreciation Right exercise may be in
cash, in Shares of equivalent value, or in some combination thereof. 
 8. Restricted Stock. 

(a) Grant of Restricted Stock. Subject to the terms and provisions of the Plan, the Administrator, at any time and from time to time,
may grant Shares of Restricted Stock to Service Providers in such amounts as the Administrator, in its sole discretion, will determine. 

(b) Restricted Stock Agreement. Each Award of Restricted Stock will be evidenced by an Award Agreement that will specify the Period of
Restriction, the number of Shares granted, and such other terms and conditions as the Administrator, in its sole discretion, will determine. Unless the Administrator determines otherwise, the Company as escrow agent will hold Shares of Restricted
Stock until the restrictions on such Shares have lapsed. 
 (c) Transferability. Except as provided in this Section 8 or as the
Administrator determines and subject to Section 13, Shares of Restricted Stock may not be sold, transferred, pledged, assigned, or otherwise alienated or hypothecated until the end of the applicable Period of Restriction. 

(d) Other Restrictions. The Administrator, in its sole discretion, may impose such other restrictions on Shares of Restricted Stock as
it may deem advisable or appropriate. 
 (e) Removal of Restrictions. Except as otherwise provided in this Section 8, Shares of
Restricted Stock covered by each Restricted Stock grant made under the Plan will be released from escrow as soon as practicable after the last day of the Period of Restriction or at such other time as the Administrator may determine. The
Administrator, in its discretion, may accelerate the time at which any restrictions will lapse or be removed. 
 (f) Voting Rights.
During the Period of Restriction, Service Providers holding Shares of Restricted Stock granted hereunder may exercise full voting rights with respect to those Shares, unless the Administrator determines otherwise. 

  
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 (g) Dividends and Other Distributions. During the Period of Restriction, Service
Providers holding Shares of Restricted Stock will be entitled to receive all dividends and other distributions paid with respect to such Shares, unless the Administrator provides otherwise. If any such dividends or distributions are paid in Shares,
the Shares will be subject to the same restrictions on transferability and forfeitability as the Shares of Restricted Stock with respect to which they were paid. 

(h) Return of Restricted Stock to Company. On the date set forth in the Award Agreement, the Restricted Stock for which restrictions
have not lapsed will revert to the Company and again will become available for grant under the Plan. 
 9. Restricted Stock Units.

 (a) Grant. Restricted Stock Units may be granted at any time and from time to time as determined by the Administrator. After the
Administrator determines that it will grant Restricted Stock Units, it will advise the Participant in an Award Agreement of the terms, conditions, and restrictions related to the grant, including the number of Restricted Stock Units. 

(b) Vesting Criteria and Other Terms. The Administrator will set vesting criteria in its discretion, which, depending on the extent to
which the criteria are met, will determine the number of Restricted Stock Units that will be paid out to the Participant. The Administrator may set vesting criteria based upon the achievement of Company-wide, business unit, or individual goals
(including, but not limited to, continued employment or service), or any other basis determined by the Administrator in its discretion. 

(c) Earning Restricted Stock Units. Upon meeting the applicable vesting criteria, the Participant will be entitled to receive a payout
as determined by the Administrator. Notwithstanding the foregoing, at any time after the grant of Restricted Stock Units, the Administrator, in its sole discretion, may reduce or waive any vesting criteria that must be met to receive a payout. 

(d) Form and Timing of Payment. Payment of earned Restricted Stock Units will be made as soon as practicable after the date(s)
determined by the Administrator and set forth in the Award Agreement. The Administrator, in its sole discretion, may settle earned Restricted Stock Units in cash, Shares, or a combination of both. 

(e) Cancellation. On the date set forth in the Award Agreement, all unearned Restricted Stock Units will be forfeited to the Company.

 10. Compliance With Code Section 409A. Awards will be designed and operated in such a manner that they are
either exempt from the application of, or comply with, the requirements of Code Section 409A, except as otherwise determined in the sole discretion of the Administrator. The Plan and each Award Agreement under the Plan is intended to meet, or
be exempt from, the requirements of Code Section 409A and will be construed and interpreted in accordance with such intent, except as otherwise determined in the sole discretion of the Administrator. 

11. Leaves of Absence/Transfer Between Locations. Unless the Administrator provides otherwise, vesting of Awards granted hereunder will
be suspended during any unpaid leave of absence. A Participant will not cease to be an Employee in the case of (i) any leave of absence approved by the Company or (ii) transfers between locations of the Company or between the Company, its
Parent, or any Subsidiary. For purposes of Incentive Stock Options, no such leave may exceed three (3) months, unless reemployment upon expiration of such leave is guaranteed by statute or contract. If reemployment upon expiration of a leave of
absence approved by the Company is not so guaranteed, then six (6) months following the first (1st) day of such leave, any Incentive Stock Option held by the Participant will cease to be
treated as an Incentive Stock Option and will be treated for tax purposes as a Nonstatutory Stock Option. 

  
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 12. Limited Transferability of Awards. 

(a) Unless determined otherwise by the Administrator, Awards may not be sold, pledged, assigned, hypothecated, or otherwise transferred in any
manner other than by will or by the laws of descent and distribution, and may be exercised, during the lifetime of the Participant, only by the Participant. . 

(b) Further, until the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the Exchange Act, or after the
Administrator determines that it is, will, or may no longer be relying upon the exemption from registration under the Exchange Act as set forth in Rule 12h-1(f) promulgated under the Exchange Act, an Option,
or prior to exercise, the Shares subject to the Option, may not be pledged, hypothecated or otherwise transferred or disposed of, in any manner, including by entering into any short position, any “put equivalent position” or any “call
equivalent position” (as defined in Rule 16a-1(h) and Rule 16a-1(b) of the Exchange Act, respectively), other than to (i) persons who are “family
members” (as defined in Rule 701(c)(3) of the Securities Act) through gifts or domestic relations orders, or (ii) to an executor or guardian of the Participant upon the death or disability of the Participant. Notwithstanding the foregoing
sentence, the Administrator, in its sole discretion, may determine to permit transfers to the Company or in connection with a Change in Control or other acquisition transactions involving the Company to the extent permitted by Rule 12h-1(f). 
 13. Limited Transferability of Shares Underlying Awards 

(a) General. Notwithstanding anything to the contrary, no Participant or other stockholder shall Transfer (as such term is defined
below) any Shares (or any rights of or interests in such Shares) acquired pursuant to the Plan and/or any Award to any person or entity unless such Transfer is approved by the Company prior to such Transfer, which approval may be granted or withheld
in the Company’s sole and absolute discretion. “Transfer” shall mean, with respect to any security, the direct or indirect assignment, sale, transfer, tender, pledge, hypothecation, or the grant, creation or suffrage of a lien or
encumbrance in or upon, or the gift, placement in trust, or the Constructive Sale (as such term is defined below) or other disposition of such security (including transfer by testamentary or intestate succession, merger or otherwise by operation of
law) or any right, title or interest therein (including, but not limited to, any right or power to vote to which the holder thereof may be entitled, whether such right or power is granted by proxy or otherwise), or the record or beneficial ownership
thereof, the offer to make such a sale, transfer, Constructive Sale or other disposition, and each agreement, arrangement or understanding, whether or not in writing, to effect any of the foregoing. “Constructive Sale” shall mean, with
respect to any security, a short sale with respect to such security, entering into or acquiring an offsetting derivative contract with respect to such security, entering into or acquiring a futures or forward contract to deliver such security, or
entering into any other hedging or other derivative transaction that has the effect of materially changing the economic benefits and risks of ownership. Any purported Transfer effected in violation of this Section 13 shall be null and void and
shall have no force or effect and 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 the Plan 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. 

(b) Approval Process. Any Participant or stockholder seeking the approval of the Company to Transfer some or all of its Shares shall
give written notice thereof to the Secretary of the Company that shall include: (1) the name of the stockholder; (2) the proposed transferee; (3) the number of shares of the Transfer of which approval is thereby requested; and
(4) the purchase price, if any, of the shares proposed for Transfer. The Company may require the Participant to supplement its notice with such additional information as the Company may request or as may otherwise be required by the applicable
Award Agreement or other applicable written agreement. In addition, such request for Transfer shall be subject to such right of first refusal, transfer provisions and any other terms and conditions as may be set forth in the applicable Award
Agreement or other applicable written agreement. 
 14. Adjustments; Dissolution or Liquidation; Merger or Change in Control. 

(a) Adjustments. In the event that any dividend or other distribution (whether in the form of cash, Shares, other securities, or other
property), recapitalization, stock split, reverse stock split, reorganization, merger, consolidation, split-up, spin-off, combination, repurchase, or exchange of Shares
or other securities of the Company, or other change in the corporate structure of the Company affecting the Shares occurs, the Administrator, in order to prevent diminution or enlargement of the benefits or potential benefits intended to be made
available under the Plan, will adjust the number and class of shares of stock that may be delivered under the Plan and/or the number, class, and price of shares of stock covered by each outstanding Award; provided, however, that the Administrator
will make such adjustments to an Award required by Section 25102(o) of the California Corporations Code to the extent the Company is relying upon the exemption afforded thereby with respect to the Award. 

  
 - 10 - 

 (b) Dissolution or Liquidation. In the event of the proposed dissolution or
liquidation of the Company, the Administrator will notify each Participant as soon as practicable prior to the effective date of such proposed transaction. To the extent it has not been previously exercised, an Award will terminate immediately prior
to the consummation of such proposed action. 
 (c) Merger or Change in Control. In the event of a merger, consolidation or other
capital reorganization or business combination transaction of the Company with or into another corporation, entity or person, or a Change in Control, each outstanding Award will be treated as the Administrator determines without a Participant’s
consent, including, without limitation, that (i) Awards will be assumed, or substantially equivalent Awards will be substituted, by the acquiring or succeeding corporation (or an affiliate thereof) with appropriate adjustments as to the number
and kind of shares and prices; (ii) the Participant’s Awards (other than Awards of Restricted Stock) will terminate upon or immediately prior to the consummation of such merger or Change in Control for no consideration;
(iii) outstanding Awards will vest and become exercisable, realizable, or payable, or restrictions applicable to an Award will lapse, in whole or in part prior to or upon consummation of such merger or Change in Control, and, to the extent the
Administrator determines, terminate upon or immediately prior to the effectiveness of such merger or Change in Control; (iv) the termination of an Award or forfeiture of Shares of Restricted Stock that are unvested at the time of the
transaction in exchange for an amount of cash and/or property, if any, equal to the excess of (1) the Fair Market Value of the Shares subject to the Awards or Restricted Stock as of the date of the occurrence of the transaction over
(2) the exercise price or purchase price paid or to be paid for the Shares subject to the Awards or Restricted Stock; (v) the continuation of such outstanding Awards by the Company (if the Company is the surviving corporation; or
(vi) any combination of the foregoing. In taking any of the actions permitted under this subsection 14(c), the Administrator will not be obligated to treat all outstanding Awards (or potion thereof), all Awards (or portion thereof) held by a
Participant, or all Awards (or portion thereof) of the same type, similarly. 
 Notwithstanding anything in this Section 14(c) to the
contrary, if a payment under an Award Agreement is subject to Code Section 409A and if the change in control definition contained in the Award Agreement does not comply with the definition of “change of control” for purposes of a
distribution under Code Section 409A, then any payment of an amount that is otherwise accelerated under this Section will be delayed until the earliest time that such payment would be permissible under Code Section 409A without triggering
any penalties applicable under Code Section 409A. 
 15. Taxes. 

(a) Taxes and Similar Obligations. As a condition of the grant, vesting and exercise of an Award, the Participant (or in the case of
the Participant’s death or a permitted transferee, the person holding or exercising the Award) shall make such arrangements as the Administrator may require for the satisfaction of any applicable U.S. federal, state, local or foreign tax,
withholding, and any other required deductions or payments that may arise in connection with such Award. The Company shall not be required to issue any Shares under the Plan until such obligations are satisfied. 

(b) Satisfaction of Obligations. To the extent permitted by Applicable Laws, the Administrator, in its sole discretion and pursuant to
such procedures as it may specify from time to time, may permit a Participant to satisfy such taxes and other similar obligations, in whole or in part by (without limitation) (i) paying cash, (ii) electing to have the Company withhold
otherwise deliverable Shares having a Fair Market Value equal to the minimum statutory amount required to be withheld, (iii) delivering to the Company already-owned Shares having a Fair Market Value equal to the statutory amount required to be
withheld, provided the delivery of such Shares will not result in any adverse accounting consequences, as the Administrator determines in its sole discretion, or (iv) selling a sufficient number of Shares otherwise deliverable to the
Participant through such means as the Administrator may determine in its sole discretion (whether through a broker or otherwise) equal to the amount required to be withheld. Unless specifically permitted by the Administrator, any Shares
withheld must be limited to avoid financial accounting charges under applicable accounting guidance, and any surrendered Shares must have been previously held for any minimum duration required to avoid financial accounting charges under applicable
accounting guidance. Further, any surrender of Shares to the Company may be subject to restrictions, including, but not limited to, any restrictions required by rules of the Securities and Exchange Commission. The Fair Market Value of the Shares to
be withheld or delivered will be determined as of the date that the obligations are required to be satisfied. 

  
 - 11 - 

 16. No Effect on Employment or Service. Neither the Plan nor any Award will confer
upon a Participant any right with respect to continuing the Participant’s relationship as a Service Provider with the Company, nor will they interfere in any way with the Participant’s right or the Company’s right to terminate such
relationship at any time, with or without cause, to the extent permitted by Applicable Laws. 
 17. Date of Grant. The date of grant
of an Award will be, for all purposes, the date on which the Administrator makes the determination granting such Award, or such other later date as is determined by the Administrator. 

18. Term of Plan. The Plan will become effective upon its adoption by the Board. Unless sooner terminated under Section 19, it
will continue in effect through and until April 3, 2029 unless terminated sooner under Section 19 below. 
 19. Amendment and
Termination of the Plan. 
 (a) Amendment and Termination. The Board may at any time amend, alter, suspend or terminate the Plan.

 (b) Stockholder Approval. The Company will obtain stockholder approval of any Plan amendment to the extent necessary and desirable
to comply with Applicable Laws. 
 (c) Effect of Amendment or Termination. No amendment, alteration, suspension or termination of the
Plan will impair the rights of any Participant, unless mutually agreed otherwise between the Participant and the Administrator. Termination of the Plan will not affect the Administrator’s ability to exercise the powers granted to it hereunder
with respect to Awards granted under the Plan prior to the date of such termination. 
 20. Conditions Upon Issuance of Shares. 

(a) Legal Compliance. Shares will not be issued pursuant to the exercise of an Award unless the exercise of such Award and the issuance
and delivery of such Shares will comply with Applicable Laws and will be further subject to the approval of counsel for the Company with respect to such compliance. 

(b) Investment Representations. As a condition to the exercise of an Award, the Company may require the person exercising such Award to
represent and warrant at the time of any such exercise that the Shares are being purchased only for investment and without any present intention to sell or distribute such Shares if, in the opinion of counsel for the Company, such a representation
is required. 
 21. Inability to Obtain Authority. The inability of the Company to obtain authority from any regulatory body having
jurisdiction, which authority is deemed by the Company’s counsel to be necessary to the lawful issuance and sale of any Shares hereunder, will relieve the Company of any liability in respect of the failure to issue or sell such Shares as to
which such requisite authority will not have been obtained. 
 22. Stockholder Approval. The Plan will be subject to approval by the
stockholders of the Company within twelve (12) months after the date the Plan is adopted by the Board. Such stockholder approval will be obtained in the manner and to the degree required under Applicable Laws. 

23. Information to Participants. 

(a) In the event the Company is relying on the exemption provided by Rule 12h-1(f) under the Exchange
Act, , and until such time as the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the Exchange Act, is no longer relying on the exemption provided by Rule 12h-1(f)(1) under
the Exchange Act or is no longer required to deliver information to Participants pursuant to Applicable Laws, the Company shall 

  
 - 12 - 

 
provide to each Participant the information described in paragraphs (e)(3), (4), and (5) of Rule 701 under the Securities Act to the extent required by, and in accordance with, the
requirements thereunder. The Company may request that Participants agree to keep the information to be provided pursuant to this section confidential. If a Participant does not agree to keep the information to be provided pursuant to this section
confidential, then the Company will not be required to provide the information unless otherwise required pursuant to Rule 12h-1(f)(1) under the Exchange Act or other Applicable Laws. 

(b) To the extent the Company is relying upon the exemption afforded by Section 25102(o) of the California Corporations Code with respect
to any Award, the Company shall furnish summary financial information (audited or unaudited) of the Company’s financial condition and results of operations, consistent with the requirements of Applicable Laws, at least annually to each
applicable Participant during the period such Participant has one or more Awards outstanding, and in the case of an individual who acquired Shares pursuant to the Plan, during the period such Participant owns such Shares; provided, however, the
Company shall not be required to provide such information if (i) the issuance is limited to key persons whose duties in connection with the Company assure their access to equivalent information or (ii) the Plan or any agreement complies
with all conditions of Rule 701 of the Securities Act; 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. 

24. Addenda. The Administrator may approve such addenda to the Plan as it may consider necessary or appropriate for the purpose of
granting Awards to Employees, Consultants or Directors, which Awards may contain such terms and conditions as the Administrator deems necessary or appropriate to accommodate differences in local law, tax policy or custom, which may deviate from the
terms and conditions set forth in this Plan. The terms of any such addenda shall supersede the terms of the Plan to the extent necessary to accommodate such differences but shall not otherwise affect the terms of the Plan as in effect for any other
purpose. 

  
 - 13 -EX-10.35

 Exhibit 10.35 

CARIBOU BIOSCIENCES, INC. 

2013 EQUITY INCENTIVE PLAN 

STOCK OPTION AGREEMENT 

Unless otherwise defined herein, the terms defined in the 2013 Equity Incentive Plan (the “Plan”) shall have the same defined
meanings in this Stock Option Agreement (the “Option Agreement”). 
  

	I.	 NOTICE OF STOCK OPTION GRANT 

 

							
		  	 Name:
	  	 	  	
				
		  	 Address:
	  	 	  	

 The undersigned Participant has been granted an Option to purchase Common Stock of the Company, subject to the
terms and conditions of the Plan and this Option Agreement, as follows: 
  

							
				
		  	 Date of Grant:
	  	 	  	
				
		  	 Vesting Commencement Date:
	  	 	  	
				
		  	Exercise Price per Share:	  	$	  	
				
		  	 Total Number of Shares Granted:
	  	 	  	
				
		  	Total Exercise Price: 	  	$	  	
				
		  	Type of Option:	  	                 Incentive Stock Option	  	
				
		  		  	                 Nonstatutory Stock Option	  	
				
		  	Term/Expiration Date:	  	 	  	

 Vesting Schedule : 

This Option shall be exercisable, in whole or in part, according to the following vesting schedule: 

[Twenty-five percent (25%) of the Shares subject to the Option shall vest on the one (1) year anniversary of the Vesting Commencement
Date, and one forty-eighth(1/48 ) of the Shares subject to the Option shall vest each month thereafter on the same day of the month as the Vesting Commencement Date (and if there is no corresponding day, on the last day of the month), subject to
Participant continuing to be a Service Provider through each such date.] 
 Termination Period : 

This Option shall be exercisable for three (3) months after Participant ceases to be a Service Provider, unless such termination is due to
Participant’s death or Disability, in which case this Option shall be exercisable for twelve (12) months after Participant ceases to be a Service Provider. Notwithstanding the foregoing sentence, in no event may this Option be exercised
after the Term/Expiration Date as provided above and this Option may be subject to earlier termination as provided in Section 13 of the Plan. 

	II.	 AGREEMENT 

1. Grant of Option . The Administrator of the Company hereby grants to the Participant named in the Notice of Stock Option Grant in Part
I of this Option Agreement (“Participant”), an option (the “Option”) to purchase the number of Shares set forth in the Notice of Stock Option Grant, at the exercise price per Share set forth in the Notice of Stock Option Grant
(the “Exercise Price”), and subject to the terms and conditions of the Plan, which is incorporated herein by reference. Subject to Section 18 of the Plan, in the event of a conflict between the terms and conditions of the Plan and
this Option Agreement, the terms and conditions of the Plan shall prevail. 
 If designated in the Notice of Stock Option Grant as an
Incentive Stock Option (“ISO”), this Option is intended to qualify as an Incentive Stock Option as defined in Section 422 of the Code. Nevertheless, to the extent that it exceeds the $100,000 rule of Code Section 422(d), this
Option shall be treated as a Nonstatutory Stock Option (“NSO”). Further, if for any reason this Option (or portion thereof) shall not qualify as an ISO, then, to the extent of such nonqualification, such Option (or portion thereof) shall
be regarded as a NSO granted under the Plan. In no event shall the Administrator, the Company or any Parent or Subsidiary or any of their respective employees or directors have any liability to Participant (or any other person) due to the failure of
the Option to qualify for any reason as an ISO. 
 2. Exercise of Option. 

(a) Right to Exercise . This Option shall be exercisable during its term in accordance with the Vesting Schedule set out in the Notice
of Stock Option Grant and with the applicable provisions of the Plan and this Option Agreement. 
 (b) Method of Exercise. This
Option shall be exercisable by delivery of an exercise notice in the form attached as Exhibit A (the “Exercise Notice”) or in a manner and pursuant to such procedures as the Administrator may determine, which shall state the
election to exercise the Option, the number of Shares with respect to which the Option is being exercised (the “Exercised Shares”), and such other representations and agreements as may be required by the Company. The Exercise Notice shall
be accompanied by payment of the aggregate Exercise Price as to all Exercised Shares, together with any applicable tax withholding. This Option shall be deemed to be exercised upon receipt by the Company of such fully executed Exercise Notice
accompanied by the aggregate Exercise Price, together with any applicable tax withholding. 
 No Shares shall be issued pursuant to the
exercise of an Option unless such issuance and such exercise comply with Applicable Laws. Assuming such compliance, for income tax purposes the Shares shall be considered transferred to Participant on the date on which the Option is exercised with
respect to such Shares. 
 3. Participant’s Representations. In the event the Shares have not been registered under the
Securities Act of 1933, as amended (the “Securities Act”), at the time this Option is exercised, Participant shall, if required by the Company, concurrently with the exercise of all or any portion of this Option, deliver to the Company his
or her Investment Representation Statement in the form attached hereto as Exhibit B . 
 4. Lock-Up Period.
Participant hereby agrees that Participant shall not 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, lend, or otherwise transfer
or dispose of, directly or indirectly, any Common Stock (or other securities) of the Company or enter into any swap, hedging or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any
Common Stock (or other securities) of the Company held by Participant (other than those included in the registration) for a period specified by the representative of the underwriters of Common Stock (or other securities) of the Company not to exceed
one hundred and eighty (180) days following the effective date of any registration statement of the Company filed under the Securities Act (or such other period as may be requested by the Company or the underwriters to accommodate regulatory
restrictions on (i) the publication or other distribution of research reports and (ii) analyst recommendations and opinions, including, but not limited to, the restrictions contained in NASD Rule 2711(f)(4) or NYSE Rule 472(f)(4), or any
successor provisions or amendments thereto). 
 Participant agrees to execute and deliver such other agreements as may be reasonably
requested by the Company or the underwriter which are consistent with the foregoing or which are necessary to give further effect thereto. In addition, if requested by the Company or the representative of the underwriters of Common Stock (or other
securities) of the Company, Participant shall provide, within ten (10) days of such request, such information as may be required by the Company or such representative in connection with the completion of any public offering of the

  
 - 2 - 

 
Company’s securities pursuant to a registration statement filed under the Securities Act. The obligations described in this Section 4 shall not apply to a registration relating solely
to employee benefit plans on Form S-1 or Form S-8 or similar forms that may be promulgated in the future, or a registration relating solely to a Commission Rule 145 transaction on Form S-4 or similar forms that may be promulgated in the future. The
Company may impose stop-transfer instructions with respect to the shares of Common Stock (or other securities) subject to the foregoing restriction until the end of said one hundred and eighty (180) day (or other) period. Participant agrees
that any transferee of the Option or shares acquired pursuant to the Option shall be bound by this Section 4. 
 5. Method of
Payment . Payment of the aggregate Exercise Price shall be by any of the following, or a combination thereof, at the election of the Participant: 

(a) cash; 
 (b) check; 

(c) consideration received by the Company under a formal cashless exercise program adopted by the Company in connection with the Plan; or 

(d) surrender of other Shares which (i) shall be valued at its Fair Market Value on the date of exercise, and (ii) must be owned
free and clear of any liens, claims, encumbrances or security interests, if accepting such Shares, in the sole discretion of the Administrator, shall not result in any adverse accounting consequences to the Company. 

6. Restrictions on Exercise. This Option may not be exercised until such time as the Plan has been approved by the stockholders of the
Company, or if the issuance of such Shares upon such exercise or the method of payment of consideration for such shares would constitute a violation of any Applicable Law. 

7. Non-Transferability of Option. 

(a) This Option may not be transferred in any manner otherwise than by will or by the laws of descent or distribution and may be exercised
during the lifetime of Participant only by Participant. The terms of the Plan and this Option Agreement shall be binding upon the executors, administrators, heirs, successors and assigns of Participant. 

(b) Further, until the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the Exchange Act, or after the
Administrator determines that it is, will, or may no longer be relying upon the exemption from registration of Options under the Exchange Act as set forth in Rule 12h-1(f) promulgated under the Exchange Act (the “Reliance End Date”),
Participant shall not transfer this Option or, prior to exercise, the Shares subject to this Option, in any manner other than (i) to persons who are “family members” (as defined in Rule 701(c)(3) of the Securities Act) through gifts
or domestic relations orders, or (ii) to an executor or guardian of Participant upon the death or disability of Participant. Until the Reliance End Date, the Options and, prior to exercise, the Shares subject to this Option, may not be pledged,
hypothecated or otherwise transferred or disposed of, including by entering into any short position, any “put equivalent position” or any “call equivalent position” (as defined in Rule 16a-1(h) and Rule 16a-1(b) of the Exchange
Act, respectively), other than as permitted in clauses (i) and (ii) of this paragraph. 
 8. Term of Option . This Option may be
exercised only within the term set out in the Notice of Stock Option Grant, and may be exercised during such term only in accordance with the Plan and the terms of this Option Agreement. 

9. Tax Obligations. 
 (a)
Tax Withholding . Participant agrees to make appropriate arrangements with the Company (or the Parent or Subsidiary employing or retaining Participant) for the satisfaction of all Federal, state, local and foreign income and employment tax
withholding requirements applicable to the Option exercise. Participant acknowledges and agrees that the Company may refuse to honor the exercise and refuse to deliver the Shares if such withholding amounts are not delivered at the time of exercise.

  
 - 3 - 

 (b) Notice of Disqualifying Disposition of ISO Shares. If the Option granted to
Participant herein is an ISO, and if Participant sells or otherwise disposes of any of the Shares acquired pursuant to the ISO on or before the later of (i) the date two (2) years after the Date of Grant, or (ii) the date one
(1) year after the date of exercise, Participant shall immediately notify the Company in writing of such disposition. Participant agrees that Participant may be subject to income tax withholding by the Company on the compensation income
recognized by Participant. 
 (c) Code Section 409A. Under Code Section 409A, an Option that vests after
December 31, 2004 (or that vested on or prior to such date but which was materially modified after October 3, 2004) that was granted with a per Share exercise price that is determined by the Internal Revenue Service (the “IRS”)
to be less than the Fair Market Value of a Share on the date of grant (a “discount option”) may be considered “deferred compensation.” An Option that is a “discount option” may result in (i) income recognition by
Participant prior to the exercise of the Option, (ii) an additional twenty percent (20%) federal income tax, and (iii) potential penalty and interest charges. The “discount option” may also result in additional state income,
penalty and interest tax to the Participant. Participant acknowledges that the Company cannot and has not guaranteed that the IRS will agree that the per Share exercise price of this Option equals or exceeds the Fair Market Value of a Share on the
date of grant in a later examination. Participant agrees that if the IRS determines that the Option was granted with a per Share exercise price that was less than the Fair Market Value of a Share on the date of grant, Participant shall be solely
responsible for Participant’s costs related to such a determination. 
 10. Entire Agreement; Governing Law. The Plan is
incorporated herein by reference. The Plan and this Option Agreement constitute the entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of the Company and
Participant with respect to the subject matter hereof, and may not be modified adversely to the Participant’s interest except by means of a writing signed by the Company and Participant. This Option Agreement is governed by the internal
substantive laws but not the choice of law rules of California. 
 11. No Guarantee of Continued Service. PARTICIPANT ACKNOWLEDGES
AND AGREES THAT THE VESTING OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS EARNED ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (OR THE PARENT OR SUBSIDIARY EMPLOYING OR RETAINING PARTICIPANT) AND NOT THROUGH THE ACT OF
BEING HIRED, BEING GRANTED THIS OPTION OR ACQUIRING SHARES HEREUNDER. PARTICIPANT FURTHER ACKNOWLEDGES AND AGREES THAT THIS AGREEMENT, THE TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING SCHEDULE SET FORTH HEREIN DO NOT CONSTITUTE AN EXPRESS OR
IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS A SERVICE PROVIDER FOR THE VESTING PERIOD, FOR ANY PERIOD, OR AT ALL, AND SHALL NOT INTERFERE IN ANY WAY WITH PARTICIPANT’S RIGHT OR THE RIGHT OF THE COMPANY (OR THE PARENT OR SUBSIDIARY EMPLOYING OR
RETAINING PARTICIPANT) TO TERMINATE PARTICIPANT’S RELATIONSHIP AS A SERVICE PROVIDER AT ANY TIME, WITH OR WITHOUT CAUSE. 
 Participant
acknowledges receipt of a copy of the Plan and represents that he or she is familiar with the terms and provisions thereof, and hereby accepts this Option subject to all of the terms and provisions thereof. Participant has reviewed the Plan and this
Option in their entirety, has had an opportunity to obtain the advice of counsel prior to executing this Option and fully understands all provisions of the Option. Participant hereby agrees to accept as binding, conclusive and final all decisions or
interpretations of the Administrator upon any questions arising under the Plan or this Option. Participant further agrees to notify the Company upon any change in the residence address indicated below. 

  
 - 4 - 

					
	PARTICIPANT	 		 	CARIBOU BIOSCIENCES, INC.
			
	   
	 		 	   

	Signature	 		 	By
			
	   
	 		 	   

	Print Name	 		 	Print Name
			
	   
	 		 	   

	Residence Address	 		 	Title

  
 - 5 - 

 EXHIBIT A 

2013 EQUITY INCENTIVE PLAN 

EXERCISE NOTICE 
 Caribou Biosciences, Inc.

 2929 7th Street, Suite 105 
 Berkeley, CA 94710 

Attention: President 
 1. Exercise of
Option. Effective as of today,                          ,
                     , the undersigned (“Participant”) hereby elects to exercise Participant’s option (the “Option”)
to purchase                      shares of the Common Stock (the “Shares”) of Caribou Biosciences, Inc. (the “Company”)
under and pursuant to the 2013 Equity Incentive Plan (the “Plan”) and the Stock Option Agreement dated
                                 ,
                    (the “Option Agreement”). 

2. Delivery of Payment. Participant herewith delivers to the Company the full purchase price of the Shares, as set forth in the Option
Agreement, and any and all withholding taxes due in connection with the exercise of the Option. 
 3. Representations of Participant.
Participant acknowledges that Participant has received, read and understood the Plan and the Option Agreement and agrees to abide by and be bound by their terms and conditions. 

4. Rights as Stockholder. Until the issuance of the Shares (as evidenced by the appropriate entry on the books of the Company or of a
duly authorized transfer agent of the Company), no right to vote or receive dividends or any other rights as a stockholder shall exist with respect to the Common Stock subject to an Award, notwithstanding the exercise of the Option. The Shares shall
be issued to Participant as soon as practicable after the Option is exercised in accordance with the Option Agreement. No adjustment shall be made for a dividend or other right for which the record date is prior to the date of issuance except as
provided in Section 13 of the Plan. 
 5. Company’s Right of First Refusal. Before any Shares held by Participant or any
transferee (either being sometimes referred to herein as the “Holder”) may be sold or otherwise transferred (including transfer by gift or operation of law), the Company or its assignee(s) shall have a right of first refusal to purchase
the Shares on the terms and conditions set forth in this Section 5 (the “Right of First Refusal”). 
 (a) Notice of
Proposed Transfer. The Holder of the Shares shall deliver to the Company a written notice (the “Notice”) stating: (i) the Holder’s bona fide intention to sell or otherwise transfer such Shares; (ii) the name of each
proposed purchaser or other transferee (“Proposed Transferee”); (iii) the number of Shares to be transferred to each Proposed Transferee; and (iv) the bona fide cash price or other consideration for which the Holder proposes to
transfer the Shares (the “Offered Price”), and the Holder shall offer the Shares at the Offered Price to the Company or its assignee(s). 

(b) Exercise of Right of First Refusal. At any time within thirty (30) days after receipt of the Notice, the Company and/or its
assignee(s) may, by giving written notice to the Holder, elect to purchase all, but not less than all, of the Shares proposed to be transferred to any one or more of the Proposed Transferees, at the purchase price determined in accordance with
subsection (c) below. 
 (c) Purchase Price. The purchase price (“Purchase Price”) for the Shares purchased by the
Company or its assignee(s) under this Section 5 shall be the Offered Price. If the Offered Price includes consideration other than cash, the cash equivalent value of the non-cash consideration shall be determined by the Board of Directors of
the Company in good faith. 

  
 - 6 - 

 (d) Payment. Payment of the Purchase Price shall be made, at the option of the
Company or its assignee(s), in cash (by check), 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
thirty (30) days after receipt of the Notice or in the manner and at the times set forth in the Notice. 
 (e) Holder’s Right
to Transfer. If all of the Shares proposed in the Notice to be transferred to a given Proposed Transferee are not purchased by the Company and/or its assignee(s) as provided in this Section 5, then the Holder may sell or otherwise transfer
such Shares to that Proposed Transferee at the Offered Price or at a higher price, provided that such sale or other transfer is consummated within one hundred and twenty (120) days after the date of the Notice, that any such sale or
other transfer is effected in accordance with any applicable securities laws and that the Proposed Transferee agrees in writing that the provisions of this Section 5 shall continue to apply to the Shares in the hands of such Proposed
Transferee. If the Shares described in the Notice are not transferred to the Proposed Transferee within such 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
before any Shares held by the Holder may be sold or otherwise transferred. 
 (f) Exception for Certain Family Transfers. Anything to
the contrary contained in this Section 5 notwithstanding, the transfer of any or all of the Shares during the Participant’s lifetime or on the 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 provisions of this Section 5. “Immediate Family” as used herein shall mean spouse, lineal descendant or antecedent, father, mother, brother or
sister. In such case, the transferee or other recipient shall receive and hold the Shares so transferred subject to the provisions of this Section 5, and there shall be no further transfer of such Shares except in accordance with the terms of
this Section 5. 
 (g) Termination of Right of First Refusal. The Right of First Refusal shall terminate as to any Shares upon
the earlier of (i) the first sale of Common Stock of the Company to the general public, or (ii) a Change in Control in which the successor corporation has equity securities that are publicly traded. 

6. 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. 
 7. Restrictive Legends and Stop-Transfer Orders . 

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

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT”) AND MAY NOT BE OFFERED, SOLD
OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE
THEREWITH. 
 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN RESTRICTIONS ON TRANSFER AND A RIGHT OF FIRST REFUSAL HELD BY
THE ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER. SUCH TRANSFER RESTRICTIONS AND RIGHT OF FIRST
REFUSAL ARE BINDING ON TRANSFEREES OF THESE SHARES. 

  
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 THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER FOR A
PERIOD OF TIME FOLLOWING THE EFFECTIVE DATE OF THE UNDERWRITTEN PUBLIC OFFERING OF THE COMPANY’S SECURITIES SET FORTH IN AN AGREEMENT BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES AND MAY NOT BE SOLD OR OTHERWISE DISPOSED OF BY THE
HOLDER PRIOR TO THE EXPIRATION OF SUCH PERIOD WITHOUT THE CONSENT OF THE COMPANY OR THE MANAGING UNDERWRITER. 
 (b)
Stop-Transfer Notices. 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)
Refusal to Transfer. 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 Exercise Notice 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. 

8. Successors and Assigns. The Company may assign any of its rights under this Exercise Notice to single or multiple assignees, and
this Exercise Notice shall inure to the benefit of the successors and assigns of the Company. Subject to the restrictions on transfer herein set forth, this Exercise Notice shall be binding upon Participant and his or her heirs, executors,
administrators, successors and assigns. 
 9. Interpretation. Any dispute regarding the interpretation of this Exercise Notice shall
be submitted by Participant or by the Company forthwith to the Administrator, which shall review such dispute at its next regular meeting. The resolution of such a dispute by the Administrator shall be final and binding on all parties. 

10. Governing Law; Severability. This Exercise Notice is governed by the internal substantive laws, but not the choice of law rules, of
California. In the event that any provision hereof becomes or is declared by a court of competent jurisdiction to be illegal, unenforceable or void, this Exercise Notice shall continue in full force and effect. 

11. Entire Agreement. The Plan and Option Agreement are incorporated herein by reference. This Exercise Notice, the Plan, the Option
Agreement and the Investment Representation Statement constitute the entire agreement of the parties with respect to the subject matter hereof and supersede in their entirety all prior undertakings and agreements of the Company and Participant with
respect to the subject matter hereof, and may not be modified adversely to the Participant’s interest except by means of a writing signed by the Company and Participant. 

  
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	Submitted by:	 		 	  Accepted by:
			
	PARTICIPANT	 		 	  CARIBOU BIOSCIENCES, INC.

							
				
	   
	 		 	 By:
	 	   

	Signature	 		 	
			
	   
	 		 	  

	Print Name	 		 	Print Name
			
	Address:	 		 	  

		 		 	Title
				
	 	 		 		 	
			
	 	 		 	Address:
			
	 	 		 	 2929 7th Street, Suite 105 
Berkeley, CA 94710

			
		 		 	  

		 		 	Date Received

  
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 EXHIBIT B 

INVESTMENT REPRESENTATION STATEMENT 

PARTICIPANT : 
 COMPANY : CARIBOU BIOSCIENCES, INC. 

SECURITY : COMMON STOCK 
 AMOUNT : 

DATE : 
 In connection with the purchase of the
above-listed Securities, the undersigned Participant represents to the Company the following: 
 (a) Participant is aware of the
Company’s business affairs and financial condition and has acquired sufficient information about the Company to reach an informed and knowledgeable decision to acquire the Securities. Participant is acquiring these Securities for investment for
Participant’s own account only and not with a view to, or for resale in connection with, any “distribution” thereof within the meaning of the Securities Act of 1933, as amended (the “Securities Act”). 

(b) Participant acknowledges and understands that the Securities constitute “restricted securities” under the Securities Act and
have not been registered under the Securities Act in reliance upon a specific exemption therefrom, which exemption depends upon, among other things, the bona fide nature of Participant’s investment intent as expressed herein. In this
connection, Participant understands that, in the view of the Securities and Exchange Commission, the statutory basis for such exemption may be unavailable if Participant’s representation was predicated solely upon a present intention to hold
these Securities for the minimum capital gains period specified under tax statutes, for a deferred sale, for or until an increase or decrease in the market price of the Securities, or for a period of one (1) year or any other fixed period in
the future. Participant further understands that the Securities must be held indefinitely unless they are subsequently registered under the Securities Act or an exemption from such registration is available. Participant further acknowledges and
understands that the Company is under no obligation to register the Securities. Participant understands that the certificate evidencing the Securities shall be imprinted with any legend required under applicable state securities laws. 

(c) Participant is familiar with the provisions of Rule 701 and Rule 144, each promulgated under the Securities Act, which, in substance,
permit limited public resale of “restricted securities” acquired, directly or indirectly from the issuer thereof, in a non-public offering subject to the satisfaction of certain conditions. Rule 701 provides that if the issuer qualifies
under Rule 701 at the time of the grant of the Option to Participant, the exercise shall be exempt from registration under the Securities Act. In the event the Company becomes subject to the reporting requirements of Section 13 or 15(d) of the
Securities Exchange Act of 1934, ninety (90) days thereafter (or such longer period as any market stand-off agreement may require) the Securities exempt under Rule 701 may be resold, subject to the satisfaction of the applicable conditions
specified by Rule 144, including in the case of affiliates (1) the availability of certain public information about the Company, (2) the amount of Securities being sold during any three (3) month period not exceeding specified
limitations, (3) the resale being made in an unsolicited “broker’s transaction”, transactions directly with a “market maker” or “riskless principal transactions” (as those terms are defined under the
Securities Exchange Act of 1934) and (4) the timely filing of a Form 144, if applicable. 
 In the event that the Company does not
qualify under Rule 701 at the time of grant of the Option, then the Securities may be resold in certain limited circumstances subject to the provisions of Rule 144, which may require (i) the availability of current public information about the
Company; (ii) the resale to occur more than a specified period after the purchase and full payment (within the meaning of Rule 144) for the Securities; and (iii) in the case of the sale of Securities by an affiliate, the satisfaction of
the conditions set forth in sections (2), (3) and (4) of the paragraph immediately above. 

  
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 (d) Participant further understands that in the event all of the applicable requirements of
Rule 701 or 144 are not satisfied, registration under the Securities Act, compliance with Regulation A, or some other registration exemption shall be required; and that, notwithstanding the fact that Rules 144 and 701 are not exclusive, the Staff of
the Securities and Exchange Commission has expressed its opinion that persons proposing to sell private placement securities other than in a registered offering and otherwise than pursuant to Rules 144 or 701 shall have a substantial burden of proof
in establishing that an exemption from registration is available for such offers or sales, and that such persons and their respective brokers who participate in such transactions do so at their own risk. Participant understands that no assurances
can be given that any such other registration exemption shall be available in such event. 
  

	
	PARTICIPANT
	
	Signature
	
	   

	Print Name
	
	Date

  
 - 11 -

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