Document:

EX-10.1

 Exhibit 10.1 

MYOKARDIA, INC. 

2012 EQUITY INCENTIVE PLAN 

ADOPTED BY THE BOARD OF DIRECTORS:
SEPTEMBER 7, 2012 
 APPROVED BY THE STOCKHOLDERS:
SEPTEMBER 7, 2012 
 TERMINATION DATE: SEPTEMBER 6, 2022 

AMENDED BY THE BOARD OF DIRECTORS:
OCTOBER 24, 2013 
 APPROVED BY THE STOCKHOLDERS:
OCTOBER 24, 2013 
 AMENDED BY THE BOARD
OF DIRECTORS: DECEMBER 12, 2014 
 AMENDED BY
THE BOARD OF DIRECTORS: APRIL 20, 2015 

APPROVED BY THE STOCKHOLDERS: APRIL 20, 2015 

1. GENERAL. 
 (a)
Definitions. Capitalized terms not otherwise defined herein shall have the meanings ascribed to them in Section 13 below. 

(b) Eligible Stock Award Recipients. The persons eligible to receive Stock Awards are Employees, Directors and Consultants. 

(c) Available Stock Awards. The Plan provides for the grant of the following Stock Awards: (i) Incentive Stock Options,
(ii) Nonstatutory Stock Options, (iii) Stock Appreciation Rights, (iv) Restricted Stock Awards, and (v) Restricted Stock Unit Awards. 

(d) Purpose. The Company, by means of the Plan, seeks to secure and retain the services of the group of persons eligible to receive
Stock Awards as set forth in Section 1(b), to provide incentives for such persons to exert maximum efforts for the success of the Company and any Affiliate, and to provide a means by which such eligible recipients may be given an opportunity to
benefit from increases in value of the Common Stock through the granting of Stock Awards. 
 2. ADMINISTRATION. 

(a) Administration by Board. The Board shall administer the Plan unless and until the Board delegates administration of the Plan to a
Committee or Committees, as provided in Section 2(c). 
 (b) Powers of Board. The Board shall have the power, subject to,
and within the limitations of, the express provisions of the Plan: 
 (i) To determine from time to time (A) which of the
persons eligible under the Plan shall be granted Stock Awards; (B) when and how each Stock Award shall be granted; (C) what type or combination of types of Stock Award shall be granted; (D) the provisions of each Stock Award granted
(which need not be identical), including the time or times when a person shall be permitted to receive cash or Common Stock pursuant to a Stock Award; (E) the number of shares of Common Stock with respect to which a Stock Award shall be granted
to each such person; and (F) the Fair Market Value applicable to a Stock Award. 

  
 1 

 (ii) To construe and interpret the Plan and Stock Awards granted under it, and to
establish, amend and revoke rules and regulations for administration of the Plan. The Board, in the exercise of this power, may correct any defect, omission or inconsistency in the Plan or in any Stock Award Agreement, in a manner and to the extent
it shall deem necessary or expedient to make the Plan or Stock Award fully effective. 
 (iii) To settle all controversies regarding
the Plan and Stock Awards granted under it. 
 (iv) To accelerate the time at which a Stock Award may first be exercised or the time
during which a Stock Award or any part thereof will vest in accordance with the Plan, notwithstanding the provisions in the Stock Award stating the time at which it may first be exercised or the time during which it will vest. 

(v) To suspend or terminate the Plan at any time. Suspension or termination of the Plan shall not impair rights and obligations under
any Stock Award granted while the Plan is in effect except with the written consent of the affected Participant. 
 (vi) To amend the
Plan in any respect the Board deems necessary or advisable, including, without limitation, amendments relating to Incentive Stock Options and certain nonqualified deferred compensation under Section 409A of the Code and/or to bring the Plan or
Stock Awards granted under the Plan into compliance therewith, subject to the limitations, if any, of applicable law. However, except as provided in Section 9(a) relating to Capitalization Adjustments, to the extent required by applicable law,
stockholder approval shall be required for any amendment of the Plan that either (A) materially increases the number of shares of Common Stock available for issuance under the Plan, (B) materially expands the class of individuals eligible
to receive Stock Awards under the Plan, (C) materially increases the benefits accruing to Participants under the Plan or materially reduces the price at which shares of Common Stock may be issued or purchased under the Plan, (D) materially
extends the term of the Plan, or (E) expands the types of Stock Awards available for issuance under the Plan. Except as provided above, rights under any Stock Award granted before amendment of the Plan shall not be impaired by any amendment of
the Plan unless (1) the Company requests the consent of the affected Participant, and (2) such Participant consents in writing.  

(vii) To submit any amendment to the Plan for stockholder approval, including, but not limited to, amendments to the Plan intended to
satisfy the requirements of Section 422 of the Code regarding Incentive Stock Options. 
 (viii) To approve forms of Stock Award
Agreements for use under the Plan and to amend the terms of any one or more Stock Awards, including, but not limited to, amendments to provide terms more favorable to the Participant than previously provided in the Stock Award Agreement, subject to
any specified limits in the Plan that are not subject to Board discretion; provided however, that, the rights under any Stock Award shall not be impaired by any such amendment unless (i) the Company requests the consent of the affected
Participant, and (ii) such Participant consents in writing. Notwithstanding the foregoing, subject to the limitations of applicable law, if any, and without the affected Participant’s consent, the Board may amend the

  
 2 

 
terms of any one or more Stock Awards if necessary to maintain the qualified status of the Stock Award as an Incentive Stock Option or to bring the Stock Award into compliance with
Section 409A of the Code. 
 (ix) Generally, to exercise such powers and to perform such acts as the Board deems necessary or
expedient to promote the best interests of the Company and that are not in conflict with the provisions of the Plan or Stock Awards. 

(x) To adopt such procedures and sub-plans as are necessary or appropriate to permit participation in the Plan by Employees, Directors
or Consultants who are foreign nationals or employed outside the United States. 
 (xi) To effect, at any time and from time to time,
with the consent of any adversely affected Participant, (A) the reduction of the exercise price (or strike price) of any outstanding Option or SAR under the Plan, (B) the cancellation of any outstanding Option or SAR under the Plan and the
grant in substitution therefore of (1) a new Option or SAR under the Plan or another equity plan of the Company covering the same or a different number of shares of Common Stock, (2) a Restricted Stock Award, (3) a Restricted Stock
Unit Award, (4) cash and/or (5) other valuable consideration (as determined by the Board, in its sole discretion), or (C) any other action that is treated as a repricing under generally accepted accounting principles;
provided, however, that no such reduction or cancellation may be effected if it is determined, in the Company’s sole discretion, that such reduction or cancellation would result in any such outstanding Option becoming subject to
the requirements of Section 409A of the Code. 
 (c) Delegation to Committee. The Board may delegate some or all of the
administration of the Plan to a Committee or Committees. If administration of the Plan is delegated to a Committee, the Committee shall have, in connection with the administration of the Plan, the powers theretofore possessed by the Board that have
been delegated to the Committee, including the power to delegate to a subcommittee of the Committee any of the administrative powers the Committee is authorized to exercise (and references in this Plan to the Board shall thereafter be to the
Committee or subcommittee), subject, however, to such resolutions, not inconsistent with the provisions of the Plan, as may be adopted from time to time by the Board. The Board may retain the authority to concurrently administer the Plan with the
Committee and may, at any time, revest in the Board some or all of the powers previously delegated. 
 (d) Delegation to an Officer.
The Board may delegate to one or more Officers of the Company the authority to do one or both of the following: (i) designate Officers and Employees of the Company or any of its Subsidiaries to be recipients of Options and Stock Appreciation
Rights (and, to the extent permitted by applicable law, other Stock Awards) and the terms thereof, and (ii) determine the number of shares of Common Stock to be subject to such Stock Awards granted to such Officers and Employees;
provided, however, that the Board resolutions regarding such delegation shall specify the total number of shares of Common Stock that may be subject to the Stock Awards granted by such Officer and that such Officer may not grant a
Stock Award to himself or herself. Notwithstanding the foregoing, the Board may not delegate authority to an Officer to determine the Fair Market Value pursuant to Section 13(s) below. 

  
 3 

 (e) Effect of Board’s Decision. All determinations, interpretations and constructions
made by the Board in good faith shall not be subject to review by any person and shall be final, binding and conclusive on all persons. 

(f) Arbitration. Any dispute or claim concerning any Stock Awards granted (or not granted) or any disputes or claims relating to or
arising out of the Plan shall be fully, finally and exclusively resolved by binding and confidential arbitration conducted pursuant to the rules of Judicial Arbitration and Mediation Services, Inc. (“JAMS”)
in Alameda County, California. The Company shall pay all arbitration fees. In addition to any other relief, the arbitrator may award to the prevailing party recovery of its attorneys’ fees and costs. By accepting a Stock Award, Participants and
the Company waive their respective rights to have any such disputes or claims tried by a judge or jury. 
 3. SHARES
SUBJECT TO THE PLAN. 
 (a) Share Reserve. Subject to the provisions
of Section 9(a) relating to Capitalization Adjustments, the aggregate number of shares of Common Stock that may be issued pursuant to Stock Awards beginning on the Effective Date shall not exceed twelve million six hundred seventy three
thousand three hundred ninety eight (12,673,398) shares (the “Share Reserve”). Furthermore, if a Stock Award (i) expires or otherwise terminates without having been exercised in full or (ii) is
settled in cash (i.e., the holder of the Stock Award receives cash rather than stock), such expiration, termination or settlement shall not reduce (or otherwise offset) the number of shares of Common Stock that may be issued
pursuant to the Plan. For clarity, the limitation in this Section 3(a) is a limitation in the number of shares of Common Stock that may be issued pursuant to the Plan. Accordingly, this Section 3(a) does not limit the granting of Stock
Awards except as provided in Section 7(a). 
 (b) Reversion of Shares to the Share Reserve. If any shares of Common Stock
issued pursuant to a Stock Award are forfeited back to the Company because of the failure to meet a contingency or condition required to vest such shares in the Participant, then the shares which are forfeited shall revert to and again become
available for issuance under the Plan. Also, any shares reacquired by the Company pursuant to Section 8(g) or as consideration for the exercise of an Option shall again become available for issuance under the Plan. Notwithstanding the
provisions of this Section 3(b), any such shares shall not be subsequently issued pursuant to the exercise of Incentive Stock Options.  

(c) Incentive Stock Option Limit. Notwithstanding anything to the contrary in this Section 3(c), subject to the provisions of
Section 9(a) relating to Capitalization Adjustments, the aggregate maximum number of shares of Common Stock that may be issued pursuant to the exercise of Incentive Stock Options shall be twenty-two million five hundred thousand
(22,500,000) shares of Common Stock.  
 (d) Source of Shares. The stock issuable under the Plan shall be shares of
authorized but unissued or reacquired Common Stock, including shares repurchased by the Company on the open market or otherwise. 

  
 4 

 4. ELIGIBILITY. 

(a) Eligibility for Specific Stock Awards. Incentive Stock Options may be granted only to employees of the Company or a “parent
corporation” or “subsidiary corporation” thereof (as such terms are defined in Sections 424(e) and (f) of the Code). Stock Awards other than Incentive Stock Options may be granted to Employees, Directors and Consultants;
provided, however, Nonstatutory Stock Options and SARs may not be granted to Employees, Directors and Consultants who are providing Continuous Service only to any “parent” of the Company, as such
term is defined in Rule 405, unless the stock underlying such Stock Awards is treated as “service recipient stock” under Section 409A of the Code because the Stock Awards are granted pursuant to a corporate transaction (such as a
spin off transaction) or unless such Stock Awards comply with the distribution requirements of Section 409A of the Code.  

(b) Ten Percent Stockholders. A Ten Percent Stockholder shall not be granted an Incentive Stock Option unless the exercise price of
such Option is at least one hundred ten percent (110%) of the Fair Market Value on the date of grant and the Option is not exercisable after the expiration of five (5) years from the date of grant. 

(c) Consultants. A Consultant shall not be eligible for the grant of a Stock Award if, at the time of grant, either the offer or the
sale of the Company’s securities to such Consultant is not exempt under Rule 701 because of the nature of the services that the Consultant is providing to the Company, because the Consultant is not a natural person, or because of any other
provision of Rule 701, unless the Company determines that such grant need not comply with the requirements of Rule 701 and will satisfy another exemption under the Securities Act as well as comply with the securities laws of all other
relevant jurisdictions.  
 5. PROVISIONS RELATING TO OPTIONS
AND STOCK APPRECIATION RIGHTS. 
 Each Option or SAR shall be in such
form and shall contain such terms and conditions as the Board shall deem appropriate. All Options shall be separately designated Incentive Stock Options or Nonstatutory Stock Options at the time of grant, and, if certificates are issued, a separate
certificate or certificates shall be issued for shares of Common Stock purchased on exercise of each type of Option. If an Option is not specifically designated as an Incentive Stock Option, then the Option shall be a Nonstatutory Stock Option. The
provisions of separate Options or SARs need not be identical; provided, however, that each Option Agreement or Stock Appreciation Right Agreement shall conform to (through incorporation of provisions hereof by reference in the
applicable Stock Award Agreement or otherwise) the substance of each of the following provisions: 
 (a) Term. Subject to the
provisions of Section 4(b) regarding Ten Percent Stockholders, no Option or SAR shall be exercisable after the expiration of ten (10) years from the date of its grant or such shorter period specified in the Stock Award Agreement.

 (b) Exercise Price. Subject to the provisions of Section 4(b) regarding Incentive Stock Options granted to Ten Percent
Stockholders, the exercise price (or strike price) of each Option or SAR shall be not less than one hundred percent (100%) of the Fair Market Value of  

  
 5 

 
the Common Stock subject to the Option or SAR on the date the Option or SAR is granted. Notwithstanding the foregoing, an Option or SAR may be granted with an exercise price (or strike price)
lower than one hundred percent (100%) of the Fair Market Value of the Common Stock subject to the Option or SAR if such Option or SAR is granted pursuant to an assumption of or substitution for another option or stock appreciation right
pursuant to a Change In Control and in a manner consistent with the provisions of Sections 409A and 424(a) of the Code (whether or not such Stock Awards are Incentive Stock Options). Each SAR will be denominated in shares of Common Stock
equivalents. 
 (c) Consideration for Options. The purchase price of Common Stock acquired pursuant to the exercise of an Option
shall be paid, to the extent permitted by applicable law and as determined by the Board in its sole discretion, by any combination of the methods of payment set forth below. The Board shall have the authority to grant Options that do not permit all
of the following methods of payment (or otherwise restrict the ability to use certain methods) and to grant Options that require the consent of the Company to utilize a particular method of payment. The permitted methods of payment are as
follows: 
 (i) by cash, check, bank draft or money order payable to the Company; 

(ii) pursuant to a program developed under Regulation T as promulgated by the Federal Reserve Board that, prior to the issuance of
the stock subject to the Option, results in either the receipt of cash (or check) by the Company or the receipt of irrevocable instructions to pay the aggregate exercise price to the Company from the sales proceeds; 

(iii) by delivery to the Company (either by actual delivery or attestation) of shares of Common Stock; 

(iv) if the Option is a Nonstatutory Stock Option, by a “net exercise” arrangement pursuant to which the Company will
reduce the number of shares of Common Stock issuable upon exercise by the largest whole number of shares with a Fair Market Value that does not exceed the aggregate exercise price; provided, however, that the Company shall accept a
cash or other payment from the Participant to the extent of any remaining balance of the aggregate exercise price not satisfied by such reduction in the number of whole shares to be issued; provided, further, that shares of Common
Stock will no longer be subject to an Option and will not be exercisable thereafter to the extent that (A) shares issuable upon exercise are reduced to pay the exercise price pursuant to the “net exercise,” (B) shares are
delivered to the Participant as a result of such exercise, and (C) shares are withheld to satisfy tax withholding obligations; 

(v) in any other form of legal consideration that is specifically approved by the Board for any particular Option or for Options
generally (which may include, without limitation, according to a deferred payment or similar arrangement with the Optionholder; provided, however, that interest shall compound at least annually and shall be charged at the minimum rate
of interest necessary to avoid (A) the imputation of interest income to the Company and compensation income to the Optionholder under any applicable provisions of the Code, and (B) the classification of the Option as a liability for
financial accounting purposes). 

  
 6 

 (d) Exercise and Payment of a SAR. To exercise any outstanding Stock Appreciation Right,
the Participant must provide written notice of exercise to the Company in compliance with the provisions of the Stock Appreciation Right Agreement evidencing such Stock Appreciation Right. The appreciation distribution payable on the exercise of a
Stock Appreciation Right will be not greater than an amount equal to the excess of (A) the aggregate Fair Market Value (on the date of the exercise of the Stock Appreciation Right) of a number of shares of Common Stock equal to the number of
Common Stock equivalents in which the Participant is vested under such Stock Appreciation Right, and with respect to which the Participant is exercising the Stock Appreciation Right on such date, over (B) the strike price that will be
determined by the Board at the time of grant of the Stock Appreciation Right. The appreciation distribution in respect to a Stock Appreciation Right may be paid in Common Stock, in cash, in any combination of the two or in any other form of
consideration, as determined by the Board and contained in the Stock Appreciation Right Agreement evidencing such Stock Appreciation Right. 

(e) Transferability of Options and SARs. The Board may, in its sole discretion, impose such limitations on the transferability of
Options and SARs as the Board shall determine. In the absence of such a determination by the Board to the contrary, the following restrictions on the transferability of Options and SARs shall apply: 

(i) Restrictions on Transfer. An Option or SAR shall not be transferable except by will or by the laws of descent and
distribution and shall be exercisable during the lifetime of the Participant only by the Participant; provided, however, that the Board may, in its sole discretion, permit transfer of the Option or SAR to such extent as
permitted by Rule 701 and in a manner consistent with applicable tax and securities laws upon the Participant’s request. 

(ii) Domestic Relations Orders. Notwithstanding the foregoing, an Option or SAR may be transferred pursuant to a domestic relations
order; provided, however, that if an Option is an Incentive Stock Option, such Option may be deemed to be a Nonstatutory Stock Option as a result of such transfer. 

(iii) Beneficiary Designation. Notwithstanding the foregoing, the Participant may, by delivering written notice to the Company, in a
form provided by or otherwise satisfactory to the Company and any broker designated by the Company to effect Option exercises, designate a third party who, in the event of the death of the Participant, shall thereafter be entitled to exercise the
Option or SAR and receive the Common Stock or other consideration resulting from such exercise. In the absence of such a designation, the executor or administrator of the Participant’s estate shall be entitled to exercise the Option or SAR and
receive the Common Stock or other consideration resulting from such exercise. 
 (f) Vesting Generally. The total number of shares of
Common Stock subject to an Option or SAR may vest and therefore become exercisable in periodic installments that may or may not be equal. The Option or SAR may be subject to such other terms and conditions on the time or times when it may or may not
be exercised (which may be based on the satisfaction of performance goals or other criteria) as the Board may deem appropriate. The vesting provisions of individual Options or SARs may vary. The provisions of this Section 5(f) are subject to
any Option or SAR provisions governing the minimum number of shares of Common Stock as to which an Option or SAR may be exercised. 

  
 7 

 (g) Termination of Continuous Service. Except as otherwise provided in the applicable
Stock Award Agreement or other agreement between the Participant and the Company, in the event that a Participant’s Continuous Service terminates (other than for Cause or upon the Participant’s death or Disability), the Participant may
exercise his or her Option or SAR (to the extent that the Participant was entitled to exercise such Stock Award as of the date of termination of Continuous Service) but only within such period of time ending on the earlier of (i) the date
three (3) months following the termination of the Participant’s Continuous Service (or such longer or shorter period specified in the Stock Award Agreement, which period shall not be less than thirty (30) days if necessary
to comply with applicable state laws unless such termination is for Cause) or (ii) the expiration of the term of the Option or SAR as set forth in the Stock Award Agreement. If, after termination of Continuous Service, the Participant does not
exercise his or her Option or SAR within the time specified herein or in the Stock Award Agreement (as applicable), the Option or SAR shall terminate. 

(h) Extension of Termination Date. Except as otherwise provided in the applicable Stock Award Agreement or other agreement between the
Participant and the Company, if the exercise of an Option or SAR following the termination of the Participant’s Continuous Service (other than for Cause or upon the Participant’s death or Disability) would be prohibited at any time solely
because the issuance of shares of Common Stock would violate the registration requirements under the Securities Act, then the Option or SAR shall terminate on the earlier of (i) the expiration of a period of three (3) months after the
termination of the Participant’s Continuous Service during which the exercise of the Option or SAR would not be in violation of such registration requirements, or (ii) the expiration of the term of the Option or SAR as set forth in the
Stock Award Agreement. In addition, unless otherwise provided in a Participant’s Award Agreement, if the sale of any Common Stock received upon exercise of an Option or SAR following the termination of the Participant’s Continuous Service
(other than for Cause) would violate the Company’s insider trading policy, then the Option or SAR shall terminate on the earlier of (i) the expiration of a period equal to the applicable post-termination exercise period after the
termination of the Participant’s Continuous Service during which the exercise of the Option or SAR would not be in violation of the Company’s insider trading policy, or (ii) the expiration of the term of the Option or SAR as set forth
in the applicable Stock Award Agreement. 
 (i) Disability of Participant. Except as otherwise provided in the applicable Stock Award
Agreement or other agreement between the Participant and the Company, in the event that a Participant’s Continuous Service terminates as a result of the Participant’s Disability, the Participant may exercise his or her Option or SAR (to
the extent that the Participant was entitled to exercise such Option or SAR as of the date of termination of Continuous Service), but only within such period of time ending on the earlier of (i) the date twelve (12) months following
such termination of Continuous Service (or such longer or shorter period specified in the Stock Award Agreement, which period shall not be less than six (6) months if necessary to comply with applicable state laws), or (ii) the
expiration of the term of the Option or SAR as set forth in the 

  
 8 

 
Stock Award Agreement. If, after termination of Continuous Service, the Participant does not exercise his or her Option or SAR within the time specified herein or in the Stock Award Agreement (as
applicable), the Option or SAR shall terminate. 
 (j) Death of Participant. Except as otherwise provided in the applicable Stock
Award Agreement or other agreement between the Participant and the Company, in the event that (i) a Participant’s Continuous Service terminates as a result of the Participant’s death, or (ii) the Participant dies within the
period (if any) specified in the Stock Award Agreement after the termination of the Participant’s Continuous Service for a reason other than death, then the Option or SAR may be exercised (to the extent the Participant was entitled to exercise
such Option or SAR as of the date of death) by the Participant’s estate, by a person who acquired the right to exercise the Option or SAR by bequest or inheritance or by a person designated to exercise the Option or SAR upon the
Participant’s death, but only within the period ending on the earlier of (i) the date eighteen (18) months following the date of death (or such longer or shorter period specified in the Stock Award Agreement, which period shall
not be less than six (6) months if necessary to comply with applicable state laws), or (ii) the expiration of the term of such Option or SAR as set forth in the Stock Award Agreement. If, after the Participant’s death, the Option
or SAR is not exercised within the time specified herein or in the Stock Award Agreement (as applicable), the Option or SAR shall terminate.  

(k) Termination for Cause. Except as explicitly provided otherwise in a Participant’s Stock Award Agreement, if a
Participant’s Continuous Service is terminated for Cause, the Option or SAR shall terminate upon the termination date of such Participant’s Continuous Service, and the Participant shall be prohibited from exercising his or her Option or
SAR from and after the time of such termination of Continuous Service. 
 (l) Non-Exempt Employees. No Option or SAR granted to an
Employee who is a non-exempt employee for purposes of the Fair Labor Standards Act of 1938, as amended, shall be first exercisable for any shares of Common Stock until at least six months following the date of grant of the Option or SAR.
Notwithstanding the foregoing, consistent with the provisions of the Worker Economic Opportunity Act, in the event of the Participant’s death or Disability, upon a Change in Control in which the vesting of such Options or SARs accelerates, or
upon the Participant’s retirement (as such term may be defined in the Participant’s Stock Award Agreement or in another applicable agreement or in accordance with the Company’s then current employment policies and guidelines) any such
vested Options and SARs may be exercised earlier than six months following the date of grant. The foregoing provision is intended to operate so that any income derived by a non-exempt employee in connection with the exercise or vesting of an Option
or SAR will be exempt from his or her regular rate of pay.  
 (m) Early Exercise of Options. An Option may, but need not,
include a provision whereby the Optionholder may elect at any time before the Optionholder’s Continuous Service terminates to exercise the Option as to any part or all of the shares of Common Stock subject to the Option prior to the full
vesting of the Option. Subject to the “Repurchase Limitation” in Section 8(l), any unvested shares of Common Stock so purchased may be subject to a repurchase right in favor of the Company or to any other restriction the Board
determines to be appropriate.  

  
 9 

 
Provided that the “Repurchase Limitation” in Section 8(l) is not violated, the Company shall not be required to exercise its repurchase right until at least
six (6) months (or such longer or shorter period of time required to avoid classification of the Option as a liability for financial accounting purposes) have elapsed following exercise of the Option unless the Board otherwise specifically
provides in the Option Agreement. 
 (n) Right of Repurchase. Subject to the “Repurchase Limitation” in
Section 8(l), the Option or SAR may include a provision whereby the Company may elect to repurchase all or any part of the vested shares of Common Stock acquired by the Participant pursuant to the exercise of the Option or SAR.  

(o) Right of First Refusal. The Option or SAR may include a provision whereby the Company may elect to exercise a right of first
refusal following receipt of notice from the Participant of the intent to transfer all or any part of the shares of Common Stock received upon the exercise of the Option or SAR. Such right of first refusal shall be subject to the
“Repurchase Limitation” in Section 8(l). Except as expressly provided in this Section 5(o) or in the Stock Award Agreement, such right of first refusal shall otherwise comply with any applicable provisions of the Bylaws of
the Company.  
 6. PROVISIONS OF RESTRICTED STOCK AWARDS
AND RESTRICTED STOCK UNITS. 
 (a) Restricted Stock Awards. Each
Restricted Stock Award Agreement shall be in such form and shall contain such terms and conditions as the Board shall deem appropriate. To the extent consistent with the Company’s Bylaws, at the Board’s election, shares of Common Stock may
be (x) held in book entry form subject to the Company’s instructions until any restrictions relating to the Restricted Stock Award lapse; or (y) evidenced by a certificate, which certificate shall be held in such form and manner as
determined by the Board. The terms and conditions of Restricted Stock Award Agreements may change from time to time, and the terms and conditions of separate Restricted Stock Award Agreements need not be identical; provided, however,
that each Restricted Stock Award Agreement shall conform to (through incorporation of the provisions hereof by reference in the agreement or otherwise) the substance of each of the following provisions: 

(i) Consideration. A Restricted Stock Award may be awarded in consideration for (A) cash or cash equivalents, (B) past or
future services actually or to be rendered to the Company or an Affiliate, or (C) any other form of legal consideration that may be acceptable to the Board in its sole discretion and permissible under applicable law. 

(ii) Vesting. Subject to the “Repurchase Limitation” in Section 8(l), shares of Common Stock awarded under the
Restricted Stock Award Agreement may be subject to forfeiture to the Company in accordance with a vesting schedule to be determined by the Board. 

(iii) Termination of Participant’s Continuous Service. If a Participant’s Continuous Service terminates, the Company may
receive through a forfeiture condition or a repurchase right, any or all of the shares of Common Stock held by the Participant that have not vested as of the date of termination of Continuous Service under the terms of the Restricted Stock Award
Agreement. 

  
 10 

 (iv) Transferability. Rights to acquire shares of Common Stock under the Restricted Stock
Award Agreement shall be transferable by the Participant only upon such terms and conditions as are set forth in the Restricted Stock Award Agreement, as the Board shall determine in its sole discretion, so long as Common Stock awarded under the
Restricted Stock Award Agreement remains subject to the terms of the Restricted Stock Award Agreement. 
 (v) Dividends. A Restricted
Stock Award Agreement may provide that any dividends paid on Restricted Stock will be subject to the same vesting and forfeiture restrictions as apply to the shares subject to the Restricted Stock Award to which they relate. 

(b) Restricted Stock Unit Awards. Each Restricted Stock Unit Award Agreement shall be in such form and shall contain such terms and
conditions as the Board shall deem appropriate. The terms and conditions of Restricted Stock Unit Award Agreements may change from time to time, and the terms and conditions of separate Restricted Stock Unit Award Agreements need not be identical,
provided, however, that each Restricted Stock Unit Award Agreement shall conform to (through incorporation of the provisions hereof by reference in the Agreement or otherwise) the substance of each of the following provisions: 

(i) Consideration. At the time of grant of a Restricted Stock Unit Award, the Board will determine the consideration, if any, to be
paid by the Participant upon delivery of each share of Common Stock subject to the Restricted Stock Unit Award. The consideration to be paid (if any) by the Participant for each share of Common Stock subject to a Restricted Stock Unit Award may be
paid in any form of legal consideration that may be acceptable to the Board in its sole discretion and permissible under applicable law. 

(ii) Vesting. At the time of the grant of a Restricted Stock Unit Award, the Board may impose such restrictions or conditions to the
vesting of the Restricted Stock Unit Award as it, in its sole discretion, deems appropriate. 
 (iii) Payment. A Restricted Stock
Unit Award may be settled by the delivery of shares of Common Stock, their cash equivalent, any combination thereof or in any other form of consideration, as determined by the Board and contained in the Restricted Stock Unit Award Agreement. 

(iv) Additional Restrictions. At the time of the grant of a Restricted Stock Unit Award, the Board, as it deems appropriate, may impose
such restrictions or conditions that delay the delivery of the shares of Common Stock (or their cash equivalent) subject to a Restricted Stock Unit Award to a time after the vesting of such Restricted Stock Unit Award. 

(v) Dividend Equivalents. Dividend equivalents may be credited in respect of shares of Common Stock covered by a Restricted Stock Unit
Award, as determined by the Board and contained in the Restricted Stock Unit Award Agreement. At the sole discretion of the Board, such dividend equivalents may be converted into additional shares of Common Stock

  
 11 

 
covered by the Restricted Stock Unit Award in such manner as determined by the Board. Any additional shares covered by the Restricted Stock Unit Award credited by reason of such dividend
equivalents will be subject to all the terms and conditions of the underlying Restricted Stock Unit Award Agreement to which they relate. 

(vi) Termination of Participant’s Continuous Service. Except as otherwise provided in the applicable Restricted Stock Unit Award
Agreement, such portion of the Restricted Stock Unit Award that has not vested will be forfeited upon the Participant’s termination of Continuous Service. 

(vii) Compliance with Section 409A of the Code. Notwithstanding anything to the contrary set forth herein, any Restricted Stock
Unit Award granted under the Plan that is not exempt from the requirements of Section 409A of the Code shall contain such provisions so that such Restricted Stock Unit Award will comply with the requirements of Section 409A of the Code.
Such restrictions, if any, shall be determined by the Board and contained in the Restricted Stock Unit Award Agreement evidencing such Restricted Stock Unit Award. For example, such restrictions may include, without limitation, a requirement that
any Common Stock that is to be issued in a year following the year in which the Restricted Stock Unit Award vests must be issued in accordance with a fixed pre-determined schedule. 

7. COVENANTS OF THE COMPANY. 

(a) Availability of Shares. During the terms of the Stock Awards, the Company shall keep available at all times the number of shares of
Common Stock reasonably required to satisfy such Stock Awards. 
 (b) Securities Law Compliance. The Company shall seek to
obtain from each regulatory commission or agency having jurisdiction over the Plan such authority as may be required to grant Stock Awards and to issue and sell shares of Common Stock upon exercise of the Stock Awards;
provided, however, that this undertaking shall not require the Company to register under the Securities Act the Plan, any Stock Award or any Common Stock issued or issuable pursuant to any such Stock Award.
If, after reasonable efforts, the Company is unable to obtain from any such regulatory commission or agency the authority that counsel for the Company deems necessary for the lawful issuance and sale of Common Stock under the Plan, the Company shall
be relieved from any liability for failure to issue and sell Common Stock upon exercise of such Stock Awards unless and until such authority is obtained. A Participant shall not be eligible for the grant of a Stock Award or the subsequent issuance
of Common Stock pursuant to the Stock Award if such grant or issuance would be in violation of any applicable securities law.  

(c) No Obligation to Notify. The Company shall have no duty or obligation to any Participant to advise such holder as to the time or
manner of exercising such Stock Award. Furthermore, the Company shall have no duty or obligation to warn or otherwise advise such holder of a pending termination or expiration of a Stock Award or a possible period in which the Stock Award may not be
exercised. The Company has no duty or obligation to minimize the tax consequences of a Stock Award to the holder of such Stock Award. 

  
 12 

 8. MISCELLANEOUS. 

(a) Use of Proceeds from Sales of Common Stock. Proceeds from the sale of shares of Common Stock pursuant to Stock Awards shall
constitute general funds of the Company. 
 (b) Corporate Action Constituting Grant of Stock Awards. Corporate action
constituting a grant by the Company of a Stock Award to any Participant shall be deemed completed as of the date of such corporate action, unless otherwise determined by the Board, regardless of when the instrument, certificate, or letter evidencing
the Stock Award is communicated to, or actually received or accepted by, the Participant.  
 (c) Stockholder Rights. No
Participant shall be deemed to be the holder of, or to have any of the rights of a holder with respect to, any shares of Common Stock subject to such Stock Award unless and until (i) such Participant has satisfied all requirements for exercise
of the Stock Award pursuant to its terms, if applicable, and (ii) the issuance of the Common Stock subject to such Stock Award has been entered into the books and records of the Company. 

(d) No Employment or Other Service Rights. Nothing in the Plan, any Stock Award Agreement or any other instrument executed thereunder
or in connection with any Stock Award granted pursuant thereto shall confer upon any Participant any right to continue to serve the Company or an Affiliate in the capacity in effect at the time the Stock Award was granted or shall affect the right
of the Company or an Affiliate to terminate (i) the employment of an Employee with or without notice and with or without cause, (ii) the service of a Consultant pursuant to the terms of such Consultant’s agreement with the Company or
an Affiliate, or (iii) the service of a Director pursuant to the Bylaws of the Company or an Affiliate, and any applicable provisions of the corporate law of the state in which the Company or the Affiliate is incorporated, as the case may be.

 (e) Incentive Stock Option $100,000 Limitation. To the extent that the aggregate Fair Market Value (determined at the time of
grant) of Common Stock with respect to which Incentive Stock Options are exercisable for the first time by any Optionholder during any calendar year (under all plans of the Company and any Affiliates) exceeds one hundred thousand
dollars ($100,000), the Options or portions thereof that exceed such limit (according to the order in which they were granted) shall be treated as Nonstatutory Stock Options, notwithstanding any contrary provision of the applicable Option
Agreement(s). 

  
 13 

 (f) Investment Assurances. The Company may require a Participant, as a condition of
exercising or acquiring Common Stock under any Stock Award, (i) to give written assurances satisfactory to the Company as to the Participant’s knowledge and experience in financial and business matters and/or to employ a purchaser
representative reasonably satisfactory to the Company who is knowledgeable and experienced in financial and business matters and that he or she is capable of evaluating, alone or together with the purchaser representative, the merits and risks of
exercising the Stock Award; and (ii) to give written assurances satisfactory to the Company stating that the Participant is acquiring Common Stock subject to the Stock Award for the Participant’s own account and not with any present
intention of selling or otherwise distributing the Common Stock. The foregoing requirements, and any assurances given pursuant to such requirements, shall be inoperative if (x) the issuance of the shares upon the exercise or acquisition of
Common Stock under the Stock Award has been registered under a then currently effective registration statement under the Securities Act, or (y) as to any particular requirement, a determination is made by counsel for the Company that such
requirement need not be met in the circumstances under the then applicable securities laws. The Company may, upon advice of counsel to the Company, place legends on stock certificates issued under the Plan as such counsel deems necessary or
appropriate in order to comply with applicable securities laws, including, but not limited to, legends restricting the transfer of the Common Stock.  

(g) Withholding Obligations. Unless prohibited by the terms of a Stock Award Agreement, the Company may, in its sole discretion,
satisfy any federal, state or local tax withholding obligation relating to a Stock Award by any of the following means or by a combination of such means: (i) causing the Participant to tender a cash payment; (ii) withholding shares of
Common Stock from the shares of Common Stock issued or otherwise issuable to the Participant in connection with the Stock Award; provided, however, that no shares of Common Stock are withheld with a value exceeding the minimum amount
of tax required to be withheld by law (or such lesser amount as may be necessary to avoid classification of the Stock Award as a liability for financial accounting purposes); (iii) withholding payment from any amounts otherwise payable to the
Participant; (iv) withholding cash from a Stock Award settled in cash; or (v) by such other method as may be set forth in the Stock Award Agreement. 

(h) Electronic Delivery. Any reference herein to a “written” agreement or document shall include any agreement or document
delivered electronically or posted on the Company’s intranet. 
 (i) Deferrals. To the extent permitted by applicable
law, the Board, in its sole discretion, may determine that the delivery of Common Stock or the payment of cash, upon the exercise, vesting or settlement of all or a portion of any Stock Award may be deferred and may establish programs and procedures
for deferral elections to be made by Participants. Deferrals by Participants will be made in accordance with Section 409A of the Code. Consistent with Section 409A of the Code, the Board may provide for distributions while a Participant is
still an employee or otherwise providing services to the Company. The Board is authorized to make deferrals of Stock Awards and determine when, and in what annual percentages, Participants may receive payments, including lump sum payments, following
the Participant’s termination of Continuous Service, and implement such other terms and conditions consistent with the provisions of the Plan and in accordance with applicable law. 

  
 14 

 (j) Compliance with Section 409A. To the extent that the Board determines that any
Stock Award granted hereunder is subject to Section 409A of the Code, the Stock Award Agreement evidencing such Stock Award shall incorporate the terms and conditions necessary to avoid the consequences specified in Section 409A(a)(1) of
the Code. To the extent applicable, the Plan and Stock Award Agreements shall be interpreted in accordance with Section 409A of the Code. 

(k) Compliance with Exemption Provided by Rule 12h-1(f). If: (i) the aggregate of the number of Optionholders and the number of
holders of all other outstanding compensatory employee stock options to purchase shares of Common Stock equals or exceeds five hundred (500), and (ii) the assets of the Company at the end of the Company’s most recently completed
fiscal year exceed $10 million, then the following restrictions shall apply during any period during which the Company does not have a class of its securities registered under Section 12 of the Exchange Act and is not required to file
reports under Section 15(d) of the Exchange Act: (A) the Options and, prior to exercise, the shares of Common Stock acquired upon exercise of the Options may not be transferred until the Company is no longer relying on the exemption
provided by Rule 12h-1(f) promulgated under the Exchange Act (“Rule 12h-1(f)”), except: (1) as permitted by Rule 701(c) promulgated under the
Securities Act, (2) to a guardian upon the disability of the Optionholder, or (3) to an executor upon the death of the Optionholder (collectively, the “Permitted Transferees”);
provided, however, the following transfers are permitted: (i) transfers by the Optionholder to the Company, and (ii) transfers in connection with a change of control or other acquisition involving
the Company, if following such transaction, the Options no longer remain outstanding and the Company is no longer relying on the exemption provided by Rule 12h-1(f); provided further,
that any Permitted Transferees may not further transfer the Options; (B) except as otherwise provided in (A) above, the Options and shares of Common Stock acquired upon exercise of the Options are restricted as to any pledge,
hypothecation, or other transfer, including any short position, any “put equivalent position” as defined by Rule 16a-1(h) promulgated under the Exchange Act, or any
“call equivalent position” as defined by Rule 16a-1(b) promulgated under the Exchange Act by the Optionholder prior to exercise of an Option until the Company is no longer relying on
the exemption provided by Rule 12h-1(f); and (C) at any time that the Company is relying on the exemption provided by Rule 12h-1(f), the Company shall
deliver to Optionholders (whether by physical or electronic delivery or written notice of the availability of the information on an internet site) the information required by Rule 701(e)(3), (4), and (5) promulgated under the
Securities Act every six (6) months, including financial statements that are not more than one hundred eighty (180) days old; provided, however, that the Company may condition the
delivery of such information upon the Optionholder’s agreement to maintain its confidentiality.  
 (l) Repurchase
Limitation. The terms of any repurchase right shall be specified in the Stock Award Agreement. The repurchase price for vested shares of Common Stock shall be the Fair Market Value of the shares of Common Stock on the date of repurchase. The
repurchase price for unvested shares of Common Stock shall be the lower of (i) the Fair Market Value of the 

  
 15 

 
shares of Common Stock on the date of repurchase or (ii) their original purchase price. However, the Company shall not exercise its repurchase right until at least six (6) months
(or such longer or shorter period of time necessary to avoid classification of the Stock Award as a liability for financial accounting purposes) have elapsed following delivery of shares of Common Stock subject to the Stock Award, unless otherwise
specifically provided by the Board. 
 9. ADJUSTMENTS UPON CHANGES IN COMMON
STOCK; OTHER CORPORATE EVENTS. 
 (a) Capitalization Adjustments. In
the event of a Capitalization Adjustment, the Board shall appropriately and proportionately adjust: (i) the class(es) and maximum number of securities subject to the Plan pursuant to Section 3(a), (ii) the class(es) and maximum number
of securities that may be issued pursuant to the exercise of Incentive Stock Options pursuant to Section 3(c), and (iii) the class(es) and number of securities and price per share of stock subject to outstanding Stock Awards. The Board
shall make such adjustments, and its determination shall be final, binding and conclusive.  
 (b) Dissolution or Liquidation.
Except as otherwise provided in the Stock Award Agreement, in the event of a dissolution or liquidation of the Company, all outstanding Stock Awards (other than Stock Awards consisting of vested and outstanding shares of Common Stock not subject to
a forfeiture condition or the Company’s right of repurchase) shall terminate immediately prior to the completion of such dissolution or liquidation, and the shares of Common Stock subject to the Company’s repurchase rights or subject to a
forfeiture condition may be repurchased or reacquired by the Company notwithstanding the fact that the holder of such Stock Award is providing Continuous Service, provided, however, that the Board may, in
its sole discretion, cause some or all Stock Awards to become fully vested, exercisable and/or no longer subject to repurchase or forfeiture (to the extent such Stock Awards have not previously expired or terminated) before the dissolution or
liquidation is completed but contingent on its completion.  
 (c) Change In Control. The following provisions shall apply to
Stock Awards in the event of a Change In Control unless otherwise provided in the instrument evidencing the Stock Award or any other written agreement between the Company or any Affiliate and the holder of the Stock Award or unless otherwise
expressly provided by the Board at the time of grant of a Stock Award. Except as otherwise stated in the Stock Award Agreement, in the event of a Change In Control, then, notwithstanding any other provision of the Plan, the Board shall take one or
more of the following actions with respect to Stock Awards, contingent upon the closing or completion of the Change In Control: 

(i) arrange for the surviving corporation or acquiring corporation (or the surviving or acquiring corporation’s parent company) to
assume or continue the Stock Award or to substitute a similar stock award for the Stock Award (including, but not limited to, an award to acquire the same consideration paid to the stockholders of the Company pursuant to the Change In Control); 

(ii) arrange for the assignment of any reacquisition or repurchase rights held by the Company in respect of Common Stock issued
pursuant to the Stock Award to the surviving corporation or acquiring corporation (or the surviving or acquiring corporation’s parent company); 

  
 16 

 (iii) accelerate the vesting, in whole or in part, of the Stock Award (and, if applicable,
the time at which the Stock Award may be exercised) to a date prior to the effective time of such Change In Control as the Board shall determine (or, if the Board shall not determine such a date, to the date that is five (5) days prior to
the effective date of the Change In Control), with such Stock Award terminating if not exercised (if applicable) at or prior to the effective time of the Change In Control; 

(iv) arrange for the lapse of any reacquisition or repurchase rights held by the Company with respect to the Stock Award; 

(v) cancel or arrange for the cancellation of the Stock Award, to the extent not vested or not exercised prior to the effective time of
the Change In Control, in exchange for such cash consideration, if any, as the Board, in its sole discretion, may consider appropriate; and 

(vi) make a payment, in such form as may be determined by the Board equal to the excess, if any, of (A) the value of the property
the holder of the Stock Award would have received upon the exercise of the Stock Award, over (B) any exercise price payable by such holder in connection with such exercise. 

The Board need not take the same action with respect to all Stock Awards or with respect to all Participants. 

(d) Additional Acceleration. A Stock Award may be subject to additional acceleration of vesting and exercisability upon or after a
Change in Control as may be provided in the Stock Award Agreement for such Stock Award or as may be provided in any other written agreement between the Company or any Affiliate and the Participant, but in the absence of such provision, no such
acceleration shall occur, other than as may be provided in accordance with Section 9(c) above.  
 10. TERMINATION
OR SUSPENSION OF THE PLAN. 
 (a) Plan Term. The Board
may suspend or terminate the Plan at any time. Unless sooner terminated by the Board pursuant to Section 2, the Plan shall automatically terminate on the day before the tenth (10th) anniversary of the earlier of (i) the date the Plan
is adopted by the Board, or (ii) the date the Plan is approved by the stockholders of the Company. No Stock Awards may be granted under the Plan while the Plan is suspended or after it is terminated. 

(b) No Impairment of Rights. Suspension or termination of the Plan shall not impair rights and obligations under any Stock Award
granted while the Plan is in effect except with the written consent of the affected Participant. 

  
 17 

 11. EFFECTIVE DATE OF PLAN. 

This Plan shall become effective on the Effective Date. 

12. CHOICE OF LAW. 

The law of the State of California shall govern all questions concerning the construction, validity and interpretation of this Plan, without
regard to that state’s conflict of laws rules. 
 13. DEFINITIONS. As used in the Plan, the following definitions shall apply to
the capitalized terms indicated below: 
 (a) “Affiliate” means, at the time of
determination, any “parent” or “majority-owned subsidiary” of the Company, as such terms are defined in Rule 405 of the Securities Act. The Board shall have the authority to determine the time or times at which
“parent” or “majority-owned subsidiary” status is determined within the foregoing definition.  
 (b)
“Board” means the Board of Directors of the Company. 
 (c)
“Capitalization Adjustment” means any change that is made in, or other events that occur with respect to, the Common Stock subject to the Plan or subject to any Stock Award after the Effective Date without
the receipt of consideration by the Company (through merger, consolidation, reorganization, recapitalization, reincorporation, stock dividend, dividend in property other than cash, stock split, liquidating dividend, combination of shares, exchange
of shares, change in corporate structure, or any similar equity restructuring transaction, as that term is used in Statement of Financial Accounting Standards No. 123 (revised). Notwithstanding the foregoing, the conversion of any convertible
securities of the Company shall not be treated as a Capitalization Adjustment. 
 (d) “Cause”
shall have the meaning ascribed to such term in any written agreement between the Participant and the Company defining such term and, in the absence of such agreement, such term means with respect to a Participant, the occurrence of any of the
following events: (i) such Participant’s commission of any felony or any crime involving fraud, dishonesty or moral turpitude under the laws of the United States or any state thereof; (ii) such Participant’s attempted commission
of, or participation in, a fraud or act of dishonesty against the Company; (iii) such Participant’s intentional, material violation of any contract or agreement between the Participant and the Company or of any statutory duty owed to the
Company; (iv) such Participant’s unauthorized use or disclosure of the Company’s confidential information or trade secrets; or (v) such Participant’s gross misconduct. The determination that a termination of the
Participant’s Continuous Service is either for Cause or without Cause shall be made by the Company in its sole discretion. Any determination by the Company that the Continuous Service of a Participant was terminated with or without Cause for
the purposes of outstanding Stock Awards held by such Participant shall have no effect upon any determination of the rights or obligations of the Company or such Participant for any other purpose. 

  
 18 

 (e) “Code” means the
Internal Revenue Code of 1986, as amended, as well as any applicable regulations and guidance thereunder. 
 (f)
“Committee” means a committee of one (1) or more Directors to whom authority has been delegated by the Board in accordance with Section 2(c). 

(g) “Common Stock” means the common stock of the Company. 

(h) “Company” means MyoKardia, Inc., a Delaware corporation. 

(i) “Consultant” means any person, including an advisor, who is (i) engaged by the Company or an Affiliate
to render consulting or advisory services and is compensated for such services, or (ii) serving as a member of the board of directors of an Affiliate and is compensated for such services. However, service solely as a Director, or payment of a
fee for such service, shall not cause a Director to be considered a “Consultant” for purposes of the Plan.  

(j) “Continuous Service” means that the Participant’s service with the Company or an Affiliate, whether as
an Employee, Director or Consultant, is not interrupted or terminated. A change in the capacity in which the Participant renders service to the Company or an Affiliate as an Employee, Director, or Consultant or a change in the Entity for which the
Participant renders such service, provided that there is no interruption or termination of the Participant’s service with the Company or an Affiliate, shall not terminate a Participant’s Continuous Service; provided, however,
if the Entity for which a Participant is rendering service ceases to qualify as an Affiliate, as determined by the Board in its sole discretion, such Participant’s Continuous Service shall be considered to have terminated on the date such
Entity ceases to qualify as an Affiliate. For example, a change in status from an employee of the Company to a consultant of an Affiliate or to a Director shall not constitute an interruption of Continuous Service. To the extent permitted by law,
the Board or the chief executive officer of the Company, in that party’s sole discretion, may determine whether Continuous Service shall be considered interrupted in the case of (i) any leave of absence approved by the Board or chief
executive officer, including sick leave, military leave or any other personal leave, or (ii) transfers between the Company, an Affiliate, or their successors. Notwithstanding the foregoing, a leave of absence shall be treated as Continuous
Service for purposes of vesting in a Stock Award only to such extent as may be provided in the Company’s leave of absence policy, in the written terms of any leave of absence agreement or policy applicable to the Participant, or as otherwise
required by law. 
 (k) “Change In Control” means the occurrence, in a single transaction or in a series of
related transactions, of any Deemed Liquidation Event (as defined in the Company’s Amended and Restated Certificate of Incorporation as in effect from time to time), other than a liquidation or dissolution addressed by Section 9(b) above.

 (l) “Director” means a member of the Board. 

(m) “Disability” means the inability of a Participant to engage in any substantially gainful activity by reason
of any medically determinable physical or mental impairment which can be expected to result in death or which has lasted or can be expected to last for a continuous 

  
 19 

 
period of not less than twelve (12) months as provided in Sections 22(e)(3) and 409A(a)(2)(c)(i) of the Code and shall be determined by the Board on the basis of such medical
evidence as the Board deems warranted under the circumstances. 
 (n) “Effective Date” means the effective
date of this Plan, which is the earlier of (i) the date that this Plan is first approved by the Company’s stockholders, or (ii) the date this Plan is adopted by the Board. 

(o) “Employee” means any person employed by the Company or an Affiliate. However, service solely as a Director,
or payment of a fee for such services, shall not cause a Director to be considered an “Employee” for purposes of the Plan. 

(p) “Entity” means a corporation, partnership, limited liability company or other entity. 

(q) “Exchange Act” means the Securities Exchange Act of 1934, as amended, and the rules and regulations
promulgated thereunder. 
 (r) “Exchange Act Person” means any natural person, Entity or “group”
(within the meaning of Section 13(d) or 14(d) of the Exchange Act), except that “Exchange Act Person” shall not include (i) the Company or any Subsidiary of the Company, (ii) any employee benefit plan of the
Company or any Subsidiary of the Company or any trustee or other fiduciary holding securities under an employee benefit plan of the Company or any Subsidiary of the Company, (iii) an underwriter temporarily holding securities pursuant to a
registered public offering of such securities, (iv) an Entity Owned, directly or indirectly, by the stockholders of the Company in substantially the same proportions as their Ownership of stock of the Company; or (v) any natural person,
Entity or “group” (within the meaning of Section 13(d) or 14(d) of the Exchange Act) that, as of the Effective Date, is the Owner, directly or indirectly, of securities of the Company representing more than
fifty percent (50%) of the combined voting power of the Company’s then outstanding securities. 
 (s) “Fair
Market Value” means, as of any date, the value of the Common Stock determined by the Board in compliance with Section 409A of the Code or, in the case of an Incentive Stock Option, in compliance with Section 422 of the Code.

 (t) “Incentive Stock Option” means an option that qualifies as an “incentive stock option”
within the meaning of Section 422 of the Code and the regulations promulgated thereunder. 
 (u) “Nonstatutory Stock
Option” means an Option that does not qualify as an Incentive Stock Option. 
 (v) “Officer”
means any person designated by the Company as an officer. 
 (w) “Option” means an Incentive Stock Option or
a Nonstatutory Stock Option to purchase shares of Common Stock granted pursuant to the Plan. 

  
 20 

 (x) “Option Agreement” means a written agreement between the
Company and an Optionholder evidencing the terms and conditions of an Option grant. Each Option Agreement shall be subject to the terms and conditions of the Plan. 

(y) “Optionholder” means a person to whom an Option is granted pursuant to the Plan or, if applicable, such
other person who holds an outstanding Option. 
 (z) “Own,” “Owned,”
“Owner,” “Ownership” A person or Entity shall be deemed to “Own,” to have “Owned,” to be the “Owner” of, or to have acquired “Ownership” of securities if such
person or Entity, directly or indirectly, through any contract, arrangement, understanding, relationship or otherwise, has or shares voting power, which includes the power to vote or to direct the voting, with respect to such securities. 

(aa) “Participant” means a person to whom a Stock Award is granted pursuant to the Plan or, if applicable, such
other person who holds an outstanding Stock Award. 
 (bb) “Plan” means this MyoKardia, Inc. 2012 Equity
Incentive Plan. 
 (cc) “Restricted Stock Award” means an award of shares of Common Stock which is granted
pursuant to the terms and conditions of Section 6(a). 
 (dd) “Restricted Stock Award Agreement” means a
written agreement between the Company and a holder of a Restricted Stock Award evidencing the terms and conditions of a Restricted Stock Award. Each Restricted Stock Award Agreement shall be subject to the terms and conditions of the Plan. 

(ee) “Restricted Stock Unit Award” means a right to receive shares of Common Stock which is granted pursuant to
the terms and conditions of Section 6(b). 
 (ff) “Restricted Stock Unit Award Agreement” means a
written agreement between the Company and a holder of a Restricted Stock Unit Award evidencing the terms and conditions of a Restricted Stock Unit Award grant. Each Restricted Stock Unit Award Agreement shall be subject to the terms and conditions
of the Plan. 
 (gg) “Rule 405” means Rule 405 promulgated under the Securities Act. 

(hh) “Rule 701” means Rule 701 promulgated under the Securities Act. 

(ii) “Securities Act” means the Securities Act of 1933, as amended. 

(jj) “Stock Appreciation Right” or “SAR” means a right to receive the appreciation on
Common Stock that is granted pursuant to the terms and conditions of Section 5. 
 (kk) “Stock Appreciation Right
Agreement” means a written agreement between the Company and a holder of a Stock Appreciation Right evidencing the terms and conditions of a Stock Appreciation Right grant. Each Stock Appreciation Right Agreement shall be subject to the
terms and conditions of the Plan. 

  
 21 

 (ll) “Stock Award” means any right to receive Common Stock granted
under the Plan, including an Incentive Stock Option, a Nonstatutory Stock Option, a Restricted Stock Award, a Restricted Stock Unit Award, or a Stock Appreciation Right. 

(mm) “Stock Award Agreement” means a written agreement between the Company and a Participant evidencing the
terms and conditions of a Stock Award grant. Each Stock Award Agreement shall be subject to the terms and conditions of the Plan. 
 (nn)
“Subsidiary” means, with respect to the Company, (i) any corporation of which more than fifty percent (50%) of the outstanding capital stock having ordinary voting power to elect a majority of the board of
directors of such corporation (irrespective of whether, at the time, stock of any other class or classes of such corporation shall have or might have voting power by reason of the happening of any contingency) is at the time, directly or indirectly,
Owned by the Company, and (ii) any partnership, limited liability company or other entity in which the Company has a direct or indirect interest (whether in the form of voting or participation in profits or capital contribution) of more than
fifty percent (50%) . 
 (oo) “Ten Percent Stockholder” means a person
who Owns (or is deemed to Own pursuant to Section 424(d) of the Code) stock possessing more than ten percent (10%) of the total combined voting power of all classes of stock of the Company or any Affiliate. 

  
 22 

 MYOKARDIA, INC. 

STOCK OPTION GRANT NOTICE 

(2012 EQUITY INCENTIVE PLAN) 

MYOKARDIA, INC., a Delaware corporation (the “Company”), pursuant to its 2012
Equity Incentive Plan (as amended and/or restated as of the “Date of Grant” set forth below, the “Plan”), hereby grants to the Optionholder set forth below an option to purchase the number of shares of the
Company’s Common Stock set forth below. This option is subject to all of the terms and conditions as set forth herein and in the Stock Option Agreement, the Plan, and the Notice of Exercise, all of which are attached hereto and incorporated
herein in their entirety. 
  

			
	Optionholder:	  	  

	Date of Grant:	  	  

	Vesting Commencement Date:	  	  

	Number of Shares Subject to Option:	  	  

	Exercise Price (Per Share):	  	  

	Total Exercise Price:	  	  

	Expiration Date:	  	  

  

					
	Type of Grant:	  	x    Incentive Stock Option1	  	 ̈    Nonstatutory Stock Option
			
	Exercise Schedule:	  	 ̈    Same as Vesting Schedule	  	x    Early Exercise Permitted until XXXXX, 60 days           after the grant date.
		
	Vesting Schedule:	  	1/4th of the shares initially subject to the Option shall vest on the first (1st) anniversary of the Vesting
Commencement Date and thereafter, 1/48th of the shares initially subject to the Option shall vest on each monthly anniversary of the Vesting Commencement Date, in each case subject to the
condition that Optionholder is, on such vesting date, providing Continuous Service.
		
	Payment:	  	By one or a combination of the following items (described in the Option Agreement):
		
		  	x    By cash or check
		  	x    Pursuant to a Regulation T Program if the Shares are publicly traded
		  	x    By delivery of already-owned shares if the Shares are publicly traded
		  	 ̈     By deferred payment
		  	 ̈     By net exercise

 Additional Terms/Acknowledgements: The undersigned Optionholder acknowledges receipt of, and understands and agrees to,
this Stock Option Grant Notice, the Stock Option Agreement and the Plan. Optionholder acknowledges and agrees that, except to the extent permitted by the Plan, this Stock Option Grant Notice and the Stock Option Agreement may not be modified,
amended or revised except in a writing signed by Optionholder and a duly authorized officer of the Company. Optionholder further acknowledges that as of the Date of Grant, this Stock Option Grant Notice, the Stock Option Agreement, and the Plan set
forth the entire understanding between Optionholder and the Company regarding the acquisition of stock in the Company and supersede all prior oral and written agreements, promises and/or representations on that subject with the exception of
(i) options previously granted and delivered to Optionholder under the Plan or the Prior Plan (as defined in the Plan), and (ii) the following agreements only: 
  

									
	                OTHER AGREEMENTS:	  	NONE	  	
			
	MYOKARDIA, INC.	  		  	OPTIONHOLDER:
					
	Signed:	  	  
	  		  	Signed:	  	  

	Name and Title:	  	  
	  		  	Date:	  	  

	Date:	  	  
	  		  		  	

 ATTACHMENTS:   Stock Option Agreement, 2012 Equity Incentive Plan and Notice of
Exercise 
  

	1 	If this is an Incentive Stock Option, it (plus other outstanding Incentive Stock Options) cannot be first exercisable for more than $100,000 in value (measured by exercise price) in any calendar year. Any excess
over $100,000 is a Nonstatutory Stock Option. 

 ATTACHMENT I 

STOCK OPTION AGREEMENT 

FOR INCENTIVE STOCK OPTION OR NONSTATUTORY
STOCK OPTION 
 (2012 EQUITY INCENTIVE PLAN) 

Pursuant to your Stock Option Grant Notice to which this Stock Option Agreement is attached as Attachment I (“Grant
Notice”) and this Stock Option Agreement, MyoKardia, Inc., a Delaware corporation (the “Company”), has granted you an option under its 2012 Equity Incentive Plan as amended and/or restated as of the Date of Grant
set forth on the Grant Notice (the “Plan”) to purchase the number of shares of the Company’s Common Stock indicated in your Grant Notice at the exercise price indicated in your Grant Notice. Defined terms not explicitly
defined in this Option Agreement but defined in the Plan shall have the same definitions as in the Plan. 
 The details of your option are
as follows: 
 1. VESTING. Subject to the limitations contained herein, your option will vest as provided in your
Grant Notice, provided that vesting will cease upon the termination of your Continuous Service. 
 2. NUMBER
OF SHARES AND EXERCISE PRICE. The number of shares of Common Stock subject to your option and your exercise price per share referenced in your Grant Notice may be
adjusted from time to time for Capitalization Adjustments. 
 3. EXERCISE RESTRICTION FOR
NON-EXEMPT EMPLOYEES. In the event that you are an Employee eligible for overtime compensation under the Fair Labor Standards Act of 1938, as amended (i.e., a “Non-Exempt
Employee”), you may not exercise your option until you have completed at least six (6) months of Continuous Service measured from the Date of Grant specified in your Grant Notice, notwithstanding any other provision of your option.

 4. EXERCISE PRIOR TO VESTING (“EARLY
EXERCISE”). If permitted in your Grant Notice (i.e., the “Exercise Schedule” indicates “Early Exercise Permitted”) and subject to the provisions of your option, you may elect at any time that is
both (i) during the period of your Continuous Service and (ii) during the term of your option, to exercise all or part of your option, including the unvested portion of your option; provided, however, that: 

(a) a partial exercise of your option shall be deemed to cover first vested shares of Common Stock and then the earliest vesting
installment of unvested shares of Common Stock; 
 (b) any shares of Common Stock so purchased from installments that have not vested
as of the date of exercise shall be subject to the purchase option in favor of the Company as described in the Company’s form of Early Exercise Stock Purchase Agreement; 

(c) you shall enter into the Company’s form of Early Exercise Stock Purchase Agreement with a vesting schedule that will result in
the same vesting as if no early exercise had occurred; and 

 (d) if your option is an Incentive Stock Option, then, to the extent that the aggregate
Fair Market Value (determined at the time of grant) of the shares of Common Stock with respect to which your option plus all other Incentive Stock Options you hold are exercisable for the first time by you during any calendar year (under all plans
of the Company and its Affiliates) exceeds one hundred thousand dollars ($100,000), your option(s) or portions thereof that exceed such limit (according to the order in which they were granted) shall be treated as Nonstatutory Stock Options. 

5. METHOD OF PAYMENT. Payment of the exercise price is due in
full upon exercise of all or any part of your option. You may elect to make payment of the exercise price in cash or by check or in any other manner permitted by your Grant Notice. 

6. WHOLE SHARES. You may exercise your option only for whole shares of Common Stock. 

7. SECURITIES LAW COMPLIANCE. Notwithstanding anything to the contrary contained herein,
you may not exercise your option unless the shares of Common Stock issuable upon such exercise are then registered under the Securities Act or, if such shares of Common Stock are not then so registered, the Company has determined that such exercise
and issuance would be exempt from the registration requirements of the Securities Act. The exercise of your option also must comply with other applicable laws and regulations governing your option, and you may not exercise your option if the Company
determines that such exercise would not be in material compliance with such laws and regulations. 
 8. TERM. 

(a) You may not exercise your option before the commencement of its term or after its term expires. The term of your option commences
on the Date of Grant and expires upon the earliest of the following: 
 (i) immediately upon the termination of your Continuous
Service for Cause; 
 (ii) three (3) months after the termination of your Continuous Service for any reason other than Cause,
Disability or death, provided that if during any part of such three (3)-month period you may not exercise your option solely because of the condition set forth in the preceding paragraph relating to “Securities Law Compliance,” your option
shall not expire until the earlier of the Expiration Date or until it shall have been exercisable for an aggregate period of three (3) months after the termination of your Continuous Service; 

(iii) twelve (12) months after the termination of your Continuous Service due to your Disability; 

(iv) eighteen (18) months after your death if you die during your Continuous Service; 

(v) the Expiration Date indicated in your Grant Notice; or 

 (vi) the day before the tenth
(10th) anniversary of the Date of Grant. 
 (b) Notwithstanding the
foregoing, if you die during the period provided in Section 8(a)(ii) or 8(a)(iii) above, the term of your option shall not expire until the earlier of eighteen (18) months after your death, the Expiration Date indicated in your Grant
Notice, or the day before the tenth (10th) anniversary of the Date of Grant. 

(c) If your option is an Incentive Stock Option, note that, to obtain the federal income tax advantages associated with an Incentive
Stock Option, the Code requires that at all times beginning on the date of grant of your option and ending on the day three (3) months before the date of your option’s exercise, you must be an employee of the Company or an Affiliate,
except in the event of your death or Disability. The Company has provided for extended exercisability of your option under certain circumstances for your benefit but cannot guarantee that your option will necessarily be treated as an Incentive Stock
Option if you continue to provide services to the Company or an Affiliate as a Consultant or Director after your employment terminates or if you otherwise exercise your option more than three (3) months after the date your employment
terminates. 
 9. EXERCISE. 

(a) You may exercise the vested portion of your option (and the unvested portion of your option if your Grant Notice so permits) during
its term by delivering a Notice of Exercise (in a form designated by the Company) together with the exercise price to the Secretary of the Company, or to such other person as the Company may designate, during regular business hours, together with
such additional documents as the Company may then require. 
 (b) By exercising your option you agree that, as a condition to any
exercise of your option, the Company may require you to enter into an arrangement providing for the payment by you to the Company of any tax withholding obligation of the Company arising by reason of (1) the exercise of your option,
(2) the lapse of any substantial risk of forfeiture to which the shares of Common Stock are subject at the time of exercise, or (3) the disposition of shares of Common Stock acquired upon such exercise. 

(c) If your option is an Incentive Stock Option, by exercising your option you agree that you will notify the Company in writing within
fifteen (15) days after the date of any disposition of any of the shares of the Common Stock issued upon exercise of your option that occurs within two (2) years after the date of your option grant or within one (1) year after such
shares of Common Stock are transferred upon exercise of your option. 
 (d) By exercising your option you agree that you shall not
sell, dispose of, transfer, make any short sale of, grant any option for the purchase of, or enter into any hedging or similar transaction with the same economic effect as a sale, any shares of Common Stock or other securities of the Company held by
you, for a period of one hundred eighty (180) days following the effective date of a registration statement of the Company filed under the Securities Act or such longer period as necessary to permit compliance with NASD Rule 2711 or NYSE Member
Rule 472 and similar rules and regulations (the “Lock-Up Period”); provided, however, that nothing contained in this section shall prevent the exercise of a repurchase option, if any, in

 
favor of the Company during the Lock-Up Period. You further agree to execute and deliver such other agreements as may be reasonably requested by the Company and/or the underwriter(s) that are
consistent with the foregoing or that are necessary to give further effect thereto. In order to enforce the foregoing covenant, the Company may impose stop-transfer instructions with respect to your shares of Common Stock until the end of such
period. The underwriters of the Company’s stock are intended third party beneficiaries of this Section 9(d) and shall have the right, power and authority to enforce the provisions hereof as though they were a party hereto. 

10. TRANSFERABILITY. Your option is not transferable, except by will or by the laws of descent and distribution, and is
exercisable during your life only by you. Notwithstanding the foregoing, by delivering written notice to the Company, in a form satisfactory to the Company, you may designate a third party who, in the event of your death, shall thereafter be
entitled to exercise your option. In addition, if permitted by the Company you may transfer your option to a trust if you are considered to be the sole beneficial owner (determined under Section 671 of the Code and applicable state law) while
the option is held in the trust, provided that you and the trustee enter into a transfer and other agreements required by the Company. 

11. TRANSFER RESTRICTIONS. You acknowledge and agree that, upon exercise of the option, the Shares shall
be subject to the limitations on transfer set forth in the Company’s Bylaws, any agreement between you and the Company or otherwise created by applicable securities laws. The certificates representing Shares issued upon exercise of your option
shall bear on their face the legends relating to such transfer restrictions. 
 12. OPTION NOT
A SERVICE CONTRACT. Your option is not an employment or service contract, and nothing in your option shall be deemed to create in any way whatsoever any obligation on your part to continue in the
employ of the Company or an Affiliate, or of the Company or an Affiliate to continue your employment. In addition, nothing in your option shall obligate the Company or an Affiliate, their respective stockholders, Boards of Directors, Officers or
Employees to continue any relationship that you might have as a Director or Consultant for the Company or an Affiliate. 
 13.
WITHHOLDING OBLIGATIONS. 
 (a) At the time you exercise your option, in whole or in part, or at
any time thereafter as requested by the Company, you hereby authorize withholding from payroll and any other amounts payable to you, and otherwise agree to make adequate provision for (including by means of a “cashless exercise” pursuant
to a program developed under Regulation T as promulgated by the Federal Reserve Board to the extent permitted by the Company), any sums required to satisfy the federal, state, local and foreign tax withholding obligations of the Company or an
Affiliate, if any, which arise in connection with the exercise of your option. 
 (b) Upon your request and subject to approval by
the Company, in its sole discretion, and compliance with any applicable legal conditions or restrictions, the Company may withhold from fully vested shares of Common Stock otherwise issuable to you upon the exercise of your option a number of whole
shares of Common Stock having a Fair Market Value, determined by the Company as of the date of exercise, not in excess of the minimum amount of tax required to be withheld by law (or such lower amount as may be necessary to avoid

 
classification of your option as a liability for financial accounting purposes). If the date of determination of any tax withholding obligation is deferred to a date later than the date of
exercise of your option, share withholding pursuant to the preceding sentence shall not be permitted unless you make a proper and timely election under Section 83(b) of the Code, covering the aggregate number of shares of Common Stock acquired
upon such exercise with respect to which such determination is otherwise deferred, to accelerate the determination of such tax withholding obligation to the date of exercise of your option. Notwithstanding the filing of such election, shares of
Common Stock shall be withheld solely from fully vested shares of Common Stock determined as of the date of exercise of your option that are otherwise issuable to you upon such exercise. Any adverse consequences to you arising in connection with
such share withholding procedure shall be your sole responsibility. 
 (c) You may not exercise your option unless the tax
withholding obligations of the Company and/or any Affiliate are satisfied. Accordingly, you may not be able to exercise your option when desired even though your option is vested, and the Company shall have no obligation to issue a certificate for
such shares of Common Stock or release such shares of Common Stock from any escrow provided for herein unless such obligations are satisfied. 

14. TAX CONSEQUENCES. You hereby agree that the Company does not have a duty to design or
administer the Plan or its other compensation programs in a manner that minimizes your tax liabilities. You shall not make any claim against the Company, or any of its Officers, Directors, Employees or Affiliates related to tax liabilities arising
from your option or your other compensation. In particular, you acknowledge that this option is exempt from Section 409A of the Code only if the exercise price per share specified in the Grant Notice is at least equal to the “fair market
value” per share of the Common Stock on the Date of Grant and there is no other impermissible deferral of compensation associated with the option. Because the Common Stock is not traded on an established securities market, the Fair Market Value
is determined by the Board, perhaps in consultation with an independent valuation firm retained by the Company. You acknowledge that there is no guarantee that the Internal Revenue Service will agree with the valuation as determined by the Board,
and you shall not make any claim against the Company, or any of its Officers, Directors, Employees or Affiliates in the event that the Internal Revenue Service asserts that the valuation determined by the Board is less than the “fair market
value” as subsequently determined by the Internal Revenue Service. 
 15. NOTICES. Any notices
provided for in your option or the Plan shall be given in writing and shall be deemed effectively given upon receipt or, in the case of notices delivered by mail by the Company to you, five (5) days after deposit in the United States mail,
postage prepaid, addressed to you at the last address you provided to the Company. 
 16. GOVERNING PLAN
DOCUMENT. Your option is subject to all the provisions of the Plan, the provisions of which are hereby made a part of your option, and is further subject to all interpretations, amendments, rules and regulations,
which may from time to time be promulgated and adopted pursuant to the Plan. In the event of any conflict between the provisions of your option and those of the Plan, the provisions of the Plan shall control. 

 ATTACHMENT II 

MYOKARDIA, INC. 

2012 EQUITY INCENTIVE PLAN 

 ATTACHMENT III 

NOTICE OF EXERCISE 

(2012 EQUITY INCENTIVE PLAN) 

 

					
	MyoKardia, Inc.	 		  	
	400 East Jamie Court	 		  	
	Suite 102	 		  	
	South San Francisco, CA 94080	 		  	
  Date of Exercise:                      
    

 Ladies and Gentlemen: 

This constitutes notice under my stock option that I elect to purchase the number of shares for the price set forth below. 

 

					
	Type of option (check one):	  	Incentive   ̈	  	Nonstatutory   ̈
			
	Stock option dated:	  	                     	  	
			
	Number of shares as to which option is exercised:	  	                     	  	
			
	Certificates to be issued in name of:	  	                     	  	
			
	Total exercise price:	  	$                   	  	
			
	Cash payment delivered herewith:	  	$                   	  	

 By this exercise, I agree (i) to provide such additional documents as you may require pursuant to the
terms of the 2012 Equity Incentive Plan, (ii) to provide for the payment by me to you (in the manner designated by you) of your withholding obligation, if any, relating to the exercise of this option, and (iii) if this exercise relates to
an incentive stock option, to notify you in writing within fifteen (15) days after the date of any disposition of any of the shares of Common Stock issued upon exercise of this option that occurs within two (2) years after the date of
grant of this option or within one (1) year after such shares of Common Stock are issued upon exercise of this option. 

I hereby make the following certifications and representations with respect to the number of shares of Common Stock of the
Company listed above (the “Shares”), which are being acquired by me for my own account upon exercise of the Option as set forth above: 

I acknowledge that the Shares have not been registered under the Securities Act of 1933, as amended (the “Securities
Act”), and are deemed to constitute “restricted securities” under Rule 701 and Rule 144 promulgated under the Securities Act. I warrant and represent to the Company that I have no present intention of distributing or selling
said Shares, except as permitted under the Securities Act and any applicable state securities laws. 

 I further acknowledge that I will not be able to resell the Shares for at least ninety
days (90) after the stock of the Company becomes publicly traded (i.e., subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934) under Rule 701 and that more restrictive conditions apply
to affiliates of the Company under Rule 144. 
 I further acknowledge that all certificates representing any of the Shares subject to
the provisions of the Option shall have endorsed thereon appropriate legends reflecting the foregoing limitations, as well as any legends reflecting restrictions pursuant to the Company’s Certificate of Incorporation, Bylaws and/or applicable
securities laws. 
 By exercising this option I agree that I shall not sell, dispose of, transfer, make any short sale of, grant any
option for the purchase of, or enter into any hedging or similar transaction with the same economic effect as a sale, any shares of Common Stock or other securities of the Company held by me, for a period of one hundred eighty (180) days
following the effective date of a registration statement of the Company filed under the Securities Act or such longer period as necessary to permit compliance with NASD Rule 2711 or NYSE Member Rule 472 and similar rules and regulations (the
“Lock-Up Period”); provided, however, that nothing contained in this section shall prevent the exercise of a repurchase option, if any, in favor of the Company during the Lock-Up Period. I further agree
to execute and deliver such other agreements as may be reasonably requested by the Company and/or the underwriter(s) that are consistent with the foregoing or that are necessary to give further effect thereto. To enforce the foregoing covenant, the
Company may impose stop-transfer instructions with respect to my shares of Common Stock until the end of such period. The underwriters of the Company’s stock are intended third party beneficiaries of this Section 9(d) and shall have the
right, power and authority to enforce the provisions hereof as though they were a party hereto. 
  

	
	Very truly yours,EX-10.3

 Exhibit 10.3 

THIRD ROCK VENTURES 

455 MISSION BAY BLVD. SOUTH 

SUITE575 
 SAN FRANCISCO, CA 94158

 June 8, 2012 
 Robert S. McDowell 

Dear Bob, 
 We are pleased to offer you
employment with MyoKardia (“the Company”) on the following terms. This employment offer is contingent upon the incorporation of MyoKardia and qualification to do business in the state of California. We anticipate these conditions being met
by July 31,2012. If these conditions are not met, the terms below will not be in force or effect. 
 1. Position. Your initial title will be
Vice President, Drug Discovery, and you will initially report to the Company’s acting Chief Executive Officer. This is a full-time position. While you render services to the Company, you will not engage in any other employment, consulting or
other business activity (whether full-time or part-time) that would create a conflict of interest with the Company. By signing this letter agreement, you confirm to the Company that you have no contractual commitments or other legal obligations that
would prohibit you from performing your duties for the Company. 
 2. Cash Compensation. The Company will pay you a starting salary at the rate of
$260,000 per year, payable in accordance with the Company’s standard payroll schedule. This salary will be subject to adjustment pursuant to the Company’s employee compensation policies in effect from time to time. It is expected that,
when an annual bonus program is approved by the Board of Directors, you will be eligible for a target bonus of 20% of your annual compensation, based upon the achievement of corporate and individual goals, as agreed by the Board of Directors. You
will be eligible to participate each year in any annual bonus plan adopted by the Company and the Company, subject to financial, business, and other circumstances and factors. 

3. Employee Benefits. As a regular employee of the Company, you will be eligible to participate in a number of Company-sponsored benefits. If the
Company does not have a health benefits program in place by the time you join, and you elect to have health insurance provided by the Company, you will be reimbursed for COBRA premiums (amount to be determined). Once the Company has a health
benefits program you will be expected to join the program if you elect to have health benefits provided by the Company. In addition, you will be entitled to 20 days of paid time off in accordance with the Company’s policy. 

4. Stock Options. Subject to the approval of the Company’s Board of Directors or its Compensation Committee, you will be granted an option to
purchase 320,000 shares of the Company’s Common Stock. The exercise price per share will be determined by the Board of Directors or the Compensation Committee when the option is granted. The option will be subject to the terms and conditions
applicable to options granted under the Company’s Stock 

 
Plan (the “Plan”), as described in the Plan and the applicable stock option agreement. You will vest in 25% of the option shares after 12 months of continuous service, and the balance
will vest in equal quarterly installments over the next 36 months of continuous service, as described in the applicable stock option agreement. 
 5.
Employee Confidentiality and Assignment Agreement. Like all Company employees, you will be required, as a condition of your employment with the Company, to sign the Company’s standard Employee Confidentiality and Assignment Agreement, a
copy of which is attached hereto as Exhibit A. 
 6. Background Check. The Company may conduct a background or reference check (or both). If so, then
you agree to cooperate fully in those procedures, and this offer is subject to the Company’s approving the outcome of those checks, in the discretion of the Company. 

7. Employment Relationship. Employment with the Company is for no specific period of time. Your employment with the Company will be “at
will,” meaning that either you or the Company may terminate your employment at any time and for any reason, with or without cause. Any contrary representations that may have been made to you are superseded by this letter agreement. This is the
full and complete agreement between you and the Company on this term. Although your job duties, title, reporting relationship, compensation and benefits, as well as the Company’s personnel policies and procedures, may change from time to time,
the “at will” nature of your employment may only be changed in an express written agreement signed by you and a duly authorized officer of the Company (other than you). 

8. Taxes. All forms of compensation referred to in this letter agreement are subject to reduction to reflect applicable withholding and payroll taxes
and other deductions required by law. You agree that the Company does not have a duty to design its compensation policies in a manner that minimizes your tax liabilities, and you will not make any claim against the Company or its Board of Directors
related to tax liabilities arising from your compensation. 
 9. Interpretation, Amendment and Enforcement. This letter agreement and Exhibit A
constitute the complete agreement between you and the Company, contain all of the terms of your employment with the Company and supersede any prior agreements, representations or understandings (whether written, oral or implied) between you and the
Company. This letter agreement may not be amended or modified, except by an express written agreement signed by both you and a duly authorized officer of the Company. The terms of this letter agreement and the resolution of any disputes as to the
meaning, effect, performance or validity of this letter agreement or arising out of, related to, or in any way connected with, this letter agreement, your employment with the Company or any other relationship between you and the Company will be
governed by California law, excluding laws relating to conflicts or choice of law. 
 * * * * * 

We hope that you will accept our offer to join the Company. You may indicate your agreement with these terms and accept this offer by signing
and dating both the enclosed duplicate original of this letter agreement and the enclosed Proprietary Information and Inventions Agreement and returning them to me. This offer, if not accepted, will expire at the

  
 2 

 
close of business on June 12, 2012. As required by law, your employment with the Company is contingent upon your providing legal proof of your identity and authorization to work in the
United States. Your employment is also contingent upon you being able to start working with the Company upon its incorporation and qualification to do business in California. 

If you have any questions, please call me at 415 766 3637. 

 

	
	 Very truly yours,

	
	 THIRD ROCK VENTURES

	
	 /s/ Charles Homcy

	 By: Charles Homcy

	 Title: Venture Partner

 I have read and accept this employment offer: 
  

	
	 /s/ Robert S. McDowell

	Robert S. McDowell

 Attachment 
 Exhibit A:
Employee Confidentiality and Assignment Agreement 

  
 3 

 MyoKardia, Inc. 

Employee Confidentiality and Assignment Agreement 

In consideration and as a condition of my employment or continued employment by MyoKardia, Inc. (the
“Company”), I agree as follows: 

 

 1. Proprietary Information. I agree that all information, whether or not in writing, concerning
the Company’s business, technology, business relationships or financial affairs which the Company has not released to the general public (collectively, “Proprietary Information”) is and will be the exclusive property of the Company.
By way of illustration, Proprietary Information may include information or material which has not been made generally available to the public, such as: (a) corporate information, including plans, strategies, methods, policies,
resolutions, negotiations or litigation; (b) marketing information, including strategies, methods, customer identities or other information about customers, prospect identities or other information about prospects, or market analyses or
projections; (c) financial information, including cost and performance data, debt arrangements, equity structure, investors and holdings, purchasing and sales data and price lists; and (d) operational and technological
information, including plans, specifications, manuals, forms, templates, software, designs, methods, procedures, formulas, discoveries, inventions, improvements, concepts and ideas; and (e) personnel information, including personnel
lists, reporting or organizational structure, resumes, personnel data, compensation structure, performance evaluations and termination arrangements or documents. Proprietary Information also includes information received in confidence by the Company
from its customers or suppliers or other third parties. 
 2. Recognition of Company’s Rights. I will not, at any time, without the
Company’s prior written permission, either during or after my employment, disclose any Proprietary Information to anyone outside of the Company, or use or permit to be used any Proprietary Information for any purpose other than the performance
of my duties as an employee of the Company. I will cooperate with the Company and use my best efforts to prevent the unauthorized disclosure of all Proprietary Information. I will deliver to the Company all copies of Proprietary Information in my
possession or control upon the earlier of a request by the Company or termination of my employment. 
 3. Rights of Others. I understand that
the Company is now and may hereafter be subject to non-disclosure or confidentiality agreements with third persons which require the Company to protect or refrain from use of proprietary information. I agree to be bound by the terms of such
agreements in the event I have access to such proprietary information. 
 4. Commitment to Company; Avoidance of Conflict of Interest. While
an employee of the Company, I will devote my full-time efforts to the Company’s business and I will not engage in any other business activity that conflicts with my

 
duties to the Company. I will advise the chief executive officer of the Company or his or her nominee at such time as any activity of either the Company or another business presents me with a
conflict of interest or the appearance of a conflict of interest as an employee of the Company. I will take whatever action is requested of me by the Company to resolve any conflict or appearance of conflict which it finds to exist. 

5. Developments. I will make full and prompt disclosure to the Company of all inventions, discoveries, designs, developments, methods,
modifications, improvements, processes, algorithms, databases, computer programs, formulae, techniques, trade secrets, mask works, graphics or images, and audio or visual works and other works of authorship (collectively “Developments”),
whether or not patentable or copyrightable, that are created, made, conceived or reduced to practice by me (alone or jointly with others) or under my direction during the period of my employment. I acknowledge that all work performed by me is on a
“work for hire” basis, and I hereby do assign and transfer and, to the extent any such assignment cannot be made at present, will assign and transfer, to the Company and its successors and assigns all my right, title and interest in all
Developments that (a) relate to the business of the Company or any customer of or supplier to the Company or any of the products or services being researched, developed, manufactured or sold by the Company or which may be used with such
products or services; or (b) result from tasks assigned to me by the Company; or (c) result from the use of premises or personal property (whether tangible or intangible) owned, leased or contracted for by the Company
(“Company-Related Developments”), and all related patents, patent applications, trademarks and trademark applications, copyrights and copyright applications, and other intellectual property rights in all countries and territories worldwide
and under any international conventions (“Intellectual Property Rights”). 
 To preclude any possible uncertainty, I have set forth on
Exhibit A attached hereto a complete list of Developments that I have, alone or jointly with others, conceived, developed or reduced to practice prior to the commencement of my employment with the Company that I consider to be my
property or the property of third parties and that I wish to have excluded from the scope of this Agreement (“Prior Inventions”). If disclosure of any such Prior Invention would cause me to violate any prior confidentiality agreement, I
understand that I am not to list such Prior Inventions in Exhibit A but am only to disclose a cursory name for each such invention, a listing of the party(ies) to whom it belongs and the fact that full disclosure as to such inventions
has not been made for that reason. I have also listed on Exhibit A all patents and patent applications in which I am named as an inventor, other than those which have been assigned to the

 

 
Company (“Other Patent Rights”). If no such disclosure is attached, I represent that there are no Prior Inventions or Other Patent Rights. If, in the course of my employment with
the Company, I incorporate a Prior Invention into a Company product, process or machine or other work done for the Company, I hereby grant to the Company a nonexclusive, royalty-free, paid-up, irrevocable, worldwide license (with the full right to
sublicense) to make, have made, modify, use, sell, offer for sale and import such Prior Invention. Notwithstanding the foregoing, I will not incorporate, or permit to be incorporated, Prior Inventions in any Company-Related Development without the
Company’s prior written consent. 
 As required pursuant to Section 2872 of the California Labor Code (a copy of which is attached as
Exhibit B), I acknowledge that the Company has notified me that the provisions of this paragraph 5 do not apply to an invention which qualifies fully under the provisions of Section 2870 of the California Labor Code. Specifically,
such provisions do not apply to, and I am not required to transfer to the Company, any invention developed entirely on my own time without using the Company’s equipment, supplies, facilities, or trade secret information except for those
inventions that either (a) relate at the time of conception or reduction to practice of the invention to the Company’s business, or actual or demonstrably anticipated research or development of the Company; or (b) result from any work
performed by me for the Company. However, I will also promptly disclose to the Company any such Developments for the purpose of determining whether they qualify for such exclusion. I understand that to the extent this Agreement is required to be
construed in accordance with the laws of any state which precludes a requirement in an employee agreement to assign certain classes of inventions made by an employee, this paragraph 5 will be interpreted not to apply to any invention which a court
rules and/or the Company agrees falls within such classes. I also hereby waive all claims to any moral rights or other special rights which I may have or accrue in any Company-Related Developments. 

6. Documents and Other Materials. I will keep and maintain adequate and current records of all Proprietary Information and Company-Related
Developments developed by me during my employment, which records will be available to and remain the sole property of the Company at all times. 
 All
files, letters, notes, memoranda, reports, records, data, sketches, drawings, notebooks, layouts, charts, quotations and proposals, specification sheets, program listings, blueprints, models, prototypes, or other written, photographic or other
tangible material containing Proprietary Information, whether created by me or others, which come into my custody or possession, are the exclusive property of the Company to be used by me only in the performance of my duties for the Company. Any
property situated on the Company’s premises and owned by the Company, including without limitation computers, disks and other storage media, filing cabinets or other work areas, is subject to inspection by the Company at any time with or
without notice. In the event of the termination of my employment for any reason, I will deliver to the Company all files, letters, notes, memoranda, reports, records, data, sketches, drawings, notebooks, layouts, charts,

 
quotations and proposals, specification sheets, program listings, blueprints, models, prototypes, or other written, photographic or other tangible material containing Proprietary Information, and
other materials of any nature pertaining to the Proprietary Information of the Company and to my work, and will not take or keep in my possession any of the foregoing or any copies. 

7. Enforcement of Intellectual Property Rights. I will cooperate fully with the Company, both during and after my employment with the Company,
with respect to the procurement, maintenance and enforcement of Intellectual Property Rights in Company-Related Developments. I will sign, both during and after the term of this Agreement, all papers, including without limitation copyright
applications, patent applications, declarations, oaths, assignments of priority rights, and powers of attorney, which the Company may deem necessary or desirable in order to protect its rights and interests in any Company-Related Development. If the
Company is unable, after reasonable effort, to secure my signature on any such papers, I hereby irrevocably designate and appoint each officer of the Company as my agent and attorney-in-fact to execute any such papers on my behalf, and to take any
and all actions as the Company may deem necessary or desirable in order to protect its rights and interests in any Company-Related Development. 
 8.
Non-Solicitation. 
 During my employment and for a period of one year following the termination of my employment for any reason (the
“Restricted Period”), I will not directly or indirectly solicit, entice or attempt to persuade any other employee or consultant of the Company to leave the Company for any reason or otherwise participate in or facilitate the hire, directly
or through another entity, of any person who is employed or engaged by the Company or who was employed or engaged by the Company within six months of any attempt to hire such person. I acknowledge and agree that if I violate any of the provisions of
this paragraph 8, the running of the Restricted Period will be extended by the time during which I engage in such violation(s). 
 9. Government
Contracts. I acknowledge that the Company may have from time to time agreements with other persons or with the United States Government or its agencies which impose obligations or restrictions on the Company regarding inventions made during
the course of work under such agreements or regarding the confidential nature of such work. I agree to comply with any such obligations or restrictions upon the direction of the Company. In addition to the rights assigned under paragraph 5, I also
assign to the Company (or any of its nominees) all rights which I have or acquired in any Developments, full title to which is required to be in the United States under any contract between the Company and the United States or any of its agencies.

 10. Prior Agreements. I hereby represent that, except as I have fully disclosed previously in writing to the Company, I am not bound by the
terms of any agreement with any previous employer or other party to refrain from using or disclosing any trade secret or confidential or proprietary

 

 
information in the course of my employment with the Company or to refrain from competing, directly or indirectly, with the business of such previous employer or any other party. I further
represent that my performance of all the terms of this Agreement as an employee of the Company does not and will not breach any agreement to keep in confidence proprietary information, knowledge or data acquired by me in confidence or in trust prior
to my employment with the Company. I will not disclose to the Company or induce the Company to use any confidential or proprietary information or material belonging to any previous employer or others. 

11. Remedies Upon Breach. I understand that the restrictions contained in this Agreement are necessary for the protection of the business and
goodwill of the Company and I consider them to be reasonable for such purpose. Any breach of this Agreement is likely to cause the Company substantial and irrevocable damage and therefore, in the event of such breach, the Company, in addition to
such other remedies which may be available, will be entitled to specific performance and other injunctive relief, without the posting of a bond. I further agree that if any action at law or in equity is necessary to enforce or interpret the terms of
this Agreement, the prevailing party shall be entitled to reasonable attorney’s fees, costs, and disbursements in addition to any other relief to which such party may be entitled. 

12. Use of Voice, Image and Likeness. I give the Company permission to use any and all of my voice, image and likeness, with or without using my
name, in connection with the products and/or services of the Company, for the purposes of advertising and promoting such products and/or services and/or the Company, and/or for other purposes deemed appropriate by the Company in its reasonable
discretion, except to the extent expressly prohibited by law. 
 13. Publications and Public Statements. I will obtain the Company’s
written approval before publishing or submitting for publication any material that relates to my work at the Company and/or incorporates any Proprietary Information. To ensure that the Company delivers a consistent message about its products,
services and operations to the public, and further in recognition that even positive statements may have a detrimental effect on the Company in certain securities transactions and other contexts, any statement about the Company which I create,
publish or post during my period of employment and for six (6) months thereafter, on any media accessible by the public, including but not limited to electronic bulletin boards and Internet-based chat rooms, must first be reviewed and approved
by an officer of the Company before it is released in the public domain. 
 14. No Employment Obligation. I understand that this Agreement
does not create an obligation on the Company or any other person to continue my employment. I acknowledge that, unless otherwise agreed in a formal written employment agreement signed on behalf of the Company by an authorized officer, my employment
with the Company is at will and therefore may be terminated by the Company or me at any time and for any reason, with or without cause.

 15. Survival and Assignment by the Company. I understand that my obligations under this Agreement
will continue in accordance with its express terms regardless of any changes in my title, position, duties, salary, compensation or benefits or other terms and conditions of employment. I further understand that my obligations under this Agreement
will continue following the termination of my employment regardless of the manner of such termination and will be binding upon my heirs, executors and administrators. The Company will have the right to assign this Agreement to its affiliates,
successors and assigns. I expressly consent to be bound by the provisions of this Agreement for the benefit of the Company or any parent, subsidiary or affiliate to whose employ I may be transferred without the necessity that this Agreement be
resigned at the time of such transfer. 
 16. Disclosure to Future Employers. I will provide a copy of this Agreement to any prospective
employer, partner or coventurer prior to entering into an employment, partnership or other business relationship with such person or entity. 
 17.
Severability. In case any provisions (or portions thereof) contained in this Agreement shall, for any reason, be held invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect
the other provisions of this Agreement, and this Agreement shall be construed as if such invalid, illegal or unenforceable provision had never been contained herein. If, moreover, any one or more of the provisions contained in this Agreement shall
for any reason be held to be excessively broad as to duration, geographical scope, activity or subject, it shall be construed by limiting and reducing it, so as to be enforceable to the extent compatible with the applicable law as it shall then
appear. 
 18. Interpretation. This Agreement will be deemed to be made and entered into in the State of California, and will in all respects
be interpreted, enforced and governed under the laws of the State of California, without regard to conflict of law principles. 

 

 I UNDERSTAND THAT THIS AGREEMENT AFFECTS IMPORTANT RIGHTS. BY SIGNING BELOW, I CERTIFY THAT I HAVE READ IT
CAREFULLY AND AM SATISFIED THAT I UNDERSTAND IT COMPLETELY. 
 IN WITNESS WHEREOF, the undersigned has executed this agreement as a
sealed instrument as of the date set forth below. 
  

			
	Signed:	 	  

		
	Date:	 	  

 EXHIBIT A 

MyoKardia, Inc. 
 333 Allerton Avenue 

South San Francisco, CA 94080 USA 
 Attention: Board of Directors

 Directors: 
 The following is a complete list of all Prior
Inventions (as defined in paragraph 5 of the attached Employee Confidentiality and Assignment Agreement): 
  

					
	  
	 	No Prior Inventions or Patent Rights	  	
			
	  
	 	Prior Inventions (listed below)	  	

  

	
	  

	
	  

	
	  

	
	  

 

					
	  
	 	Number of additional sheets attached	  	

  

			
	Very truly yours,
	
	  

	Employee Signature
	
	  

	Employee Name
	
	  

	Date

 EXHIBIT B 

California Labor Code – CAL. CIV. Code 2872 
 If an
employment agreement entered into after January 1, 1980, contains a provision requiring the employee to assign or offer to assign any of his or her rights in any invention to his or her employer, the employer must also, at the time the
agreement is made, provide a written notification to the employee that the agreement does not apply to an invention which qualifies fully under the provisions of Section 2870. In any suit or action arising thereunder, the burden of proof shall
be on the employee claiming the benefits of its provisions.

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00249-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00249-of-00352.parquet"}]]