Document:

Exhibit 10.8

    

    

      Castle Biosciences, Inc.

      

      

      2019 Employee Stock Purchase Plan

      

      

      Adopted by the Board of Directors: July 11, 2019

      Approved by the Stockholders: July 11, 2019

      

      

      1.          General;
            Purpose.

      

      

      (a)          The Plan provides a means by which
          Eligible Employees of the Company and certain designated Related Corporations may be given an opportunity to purchase shares of Common Stock. The Plan permits the Company to grant a series of Purchase Rights to Eligible Employees under an
          Employee Stock Purchase Plan.

      

      

      (b)          The Company, by means of the Plan,
          seeks to retain the services of such Employees, to secure and retain the services of new Employees and to provide incentives for such persons to exert maximum efforts for the success of the Company and its Related Corporations.

      

      

      2.          Administration.

      

      

      (a)          The Board will 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)          The Board will have the power, subject
          to, and within the limitations of, the express provisions of the Plan:

      

      

      (i)          To determine how and when Purchase
          Rights will be granted and the provisions of each Offering (which need not be identical).

      

      

      (ii)         To designate from time to time which
          Related Corporations of the Company will be eligible to participate in the Plan.

      

      

      (iii)       To construe and interpret the Plan and
          Purchase Rights, and to establish, amend and revoke rules and regulations for its administration. The Board, in the exercise of this power, may correct any defect, omission or inconsistency in the Plan, in a manner and to the extent it deems
          necessary or expedient to make the Plan fully effective.

      

      

      (iv)         To settle all controversies regarding
          the Plan and Purchase Rights granted under the Plan.

      

      

      (v)          To suspend or terminate the Plan at
          any time as provided in Section 12.

      

      

      (vi)        To amend the Plan at any time as
          provided in Section 12.

      

      

      (vii)      Generally, to exercise such powers and
          to perform such acts as it deems necessary or expedient to promote the best interests of the Company and its Related Corporations and to carry out the intent that the Plan be treated as an Employee Stock Purchase Plan.

      

      

      (viii)      To adopt such procedures and sub-plans
          as are necessary or appropriate to permit participation in the Plan by Employees who are foreign nationals or employed outside the United States.

      
        
          

      

      (c)          The Board may delegate some or all of
          the administration of the Plan to a Committee or Committees. If administration is delegated to a Committee, the Committee will 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 any of the administrative powers the Committee is authorized to exercise (and references to the Board in this Plan and in any applicable Offering Document will
          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. Whether or not the Board has delegated administration of the Plan to a Committee, the Board will have the final power
          to determine all questions of policy and expediency that may arise in the administration of the Plan.

      

      

      (d)          All determinations, interpretations
          and constructions made by the Board in good faith will not be subject to review by any person and will be final, binding and conclusive on all persons.

      

      

      3.          Shares
            of Common Stock Subject to the Plan.

      

      

      (a)          Subject to the provisions of Section
          11(a) relating to Capitalization Adjustments, the maximum number of shares of Common Stock that may be issued under the Plan will not exceed 411,935 shares of Common Stock, plus the number of shares
          of Common Stock that are automatically added on January 1st of each year for a period of up to ten years, commencing on the first January 1 following the IPO Date and ending on (and including) January 1, 2029, in an amount equal to the lesser of
          (i) 1% of the total number of shares of Capital Stock outstanding on December 31st of the preceding calendar year, and (ii) 411,935 shares of Common Stock. Notwithstanding the foregoing, the Board
          may act prior to the first day of any calendar year to provide that there will be no January 1st increase in the share reserve for such calendar year or that the
          increase in the share reserve for such calendar year will be a lesser number of shares of Common Stock than would otherwise occur pursuant to the preceding sentence.

      

      

      (b)          If any Purchase Right granted under
          the Plan terminates without having been exercised in full, the shares of Common Stock not purchased under such Purchase Right will again become available for issuance under the Plan.

      

      

      (c)          The stock purchasable under the Plan
          will be shares of authorized but unissued or reacquired Common Stock, including shares repurchased by the Company on the open market.

      

      

      4.          Grant
            of Purchase Rights; Offering.

      

      

      (a)          The Board may from time to time grant
          or provide for the grant of Purchase Rights to Eligible Employees under an Offering (consisting of one or more Purchase Periods) on an Offering Date or Offering Dates selected by the Board. Each Offering will be in such form and will contain such
          terms and conditions as the Board will deem appropriate, and will comply with the requirement of Section 423(b)(5) of the Code that all Employees granted Purchase Rights will have the same rights and privileges. The terms and conditions of an
          Offering shall be incorporated by reference into the Plan and treated as part of the Plan. The provisions of separate Offerings need not be identical, but each Offering will include (through incorporation of the provisions of this Plan by
          reference in the document comprising the Offering or otherwise) the period during which the Offering will be effective, which period will not exceed 27 months beginning with the Offering Date, and the substance of the provisions contained in
          Sections 5 through 8, inclusive.

      

      

      (b)          If a Participant has more than one
          Purchase Right outstanding under the Plan, unless he or she otherwise indicates in forms delivered to the Company: (i) each form will apply to all of his or her Purchase Rights under the Plan, and (ii) a Purchase Right with a lower exercise price
          (or an earlier-granted Purchase Right, if different Purchase Rights have identical exercise prices) will be exercised to the fullest possible extent before a Purchase Right with a higher exercise price (or a later-granted Purchase Right if
          different Purchase Rights have identical exercise prices) will be exercised.

      
        
          

      

      (c)         The Board will have the discretion to
          structure an Offering so that if the Fair Market Value of a share of Common Stock on the first Trading Day of a new Purchase Period within that Offering is less than or equal to the Fair Market Value of a share of Common Stock on the Offering
          Date for that Offering, then (i) that Offering will terminate immediately as of that first Trading Day, and (ii) the Participants in such terminated Offering will be automatically enrolled in a new Offering beginning on the first Trading Day of
          such new Purchase Period.

      

      

      5.          Eligibility.

      

      

      (a)          Purchase Rights may be granted only to
          Employees of the Company or, as the Board may designate in accordance with Section 2(b), to Employees of a Related Corporation. Except as provided in Section 5(b), an Employee will not be eligible to be granted Purchase Rights unless, on the
          Offering Date, the Employee has been in the employ of the Company or the Related Corporation, as the case may be, for such continuous period preceding such Offering Date as the Board may require, but in no event will the required period of
          continuous employment be equal to or greater than two years.  In addition, the Board may provide that no Employee will be eligible to be granted Purchase Rights under the Plan unless, on the Offering Date, such Employee’s customary employment
          with the Company or the Related Corporation is more than 20 hours per week, more than five months per calendar year or such other criteria as the Board may determine consistent with Section 423 of the Code.

      

      

      (b)          The Board may provide that each person
          who, during the course of an Offering, first becomes an Eligible Employee will, on a date or dates specified in the Offering which coincides with the day on which such person becomes an Eligible Employee or which occurs thereafter, receive a
          Purchase Right under that Offering, which Purchase Right will thereafter be deemed to be a part of that Offering. Such Purchase Right will have the same characteristics as any Purchase Rights originally granted under that Offering, as described
          herein, except that:

      

      

      (i)          the date on which such Purchase Right
          is granted will be the “Offering Date” of such Purchase Right for all purposes, including determination of the exercise price of such Purchase Right;

      

      

      (ii)         the period of the Offering with
          respect to such Purchase Right will begin on its Offering Date and end coincident with the end of such Offering; and

      

      

      (iii)        the Board may provide that if such
          person first becomes an Eligible Employee within a specified period of time before the end of the Offering, he or she will not receive any Purchase Right under that Offering.

      

      

      (c)          No Employee will be eligible for the
          grant of any Purchase Rights if, immediately after any such Purchase Rights are granted, such Employee owns stock possessing five percent or more of the total combined voting power or value of all classes of stock of the Company or of any Related
          Corporation. For purposes of this Section 5(c), the rules of Section 424(d) of the Code will apply in determining the stock ownership of any Employee, and stock which such Employee may purchase under all outstanding Purchase Rights and options
          will be treated as stock owned by such Employee.

      

      

      (d)        As specified by Section 423(b)(8) of
          the Code, an Eligible Employee may be granted Purchase Rights only if such Purchase Rights, together with any other rights granted under all Employee Stock Purchase Plans of the Company and any Related Corporations, do not permit such Eligible
          Employee’s rights to purchase stock of the Company or any Related Corporation to accrue at a rate which exceeds $25,000 of Fair Market Value of such stock (determined at the time such rights are granted, and which, with respect to the Plan, will
          be determined as of their respective Offering Dates) for each calendar year in which such rights are outstanding at any time.

      
        
          

      

      (e)          Officers of the Company and any
          designated Related Corporation, if they are otherwise Eligible Employees, will be eligible to participate in Offerings under the Plan. Notwithstanding the foregoing, the Board may provide in an Offering that Employees who are highly compensated
          Employees within the meaning of Section 423(b)(4)(D) of the Code will not be eligible to participate.

      

      

      6.          Purchase
            Rights; Purchase Price.

      

      

      (a)          On each Offering Date, each Eligible
          Employee, pursuant to an Offering made under the Plan, will be granted a Purchase Right to purchase up to that number of shares of Common Stock purchasable either with a percentage or with a maximum dollar amount, as designated by the Board, but
          in either case not exceeding 15% of such Employee’s earnings (as defined by the Board in each Offering) during the period that begins on the Offering Date (or such later date as the Board determines for a particular Offering) and ends on the date
          stated in the Offering, which date will be no later than the end of the Offering.

      

      

      (b)          The Board will establish one or more
          Purchase Dates during an Offering on which Purchase Rights granted for that Offering will be exercised and shares of Common Stock will be purchased in accordance with such Offering.

      

      

      (c)          In connection with each Offering made
          under the Plan, the Board may specify (i) a maximum number of shares of Common Stock that may be purchased by any Participant on any Purchase Date during such Offering, (ii) a maximum aggregate number of shares of Common Stock that may be
          purchased by all Participants pursuant to such Offering and/or (iii) a maximum aggregate number of shares of Common Stock that may be purchased by all Participants on any Purchase Date under the Offering. If the aggregate purchase of shares of
          Common Stock issuable upon exercise of Purchase Rights granted under the Offering would exceed any such maximum aggregate number, then, in the absence of any Board action otherwise, a pro rata (based on each Participant’s accumulated
          Contributions) allocation of the shares of Common Stock available will be made in as nearly a uniform manner as will be practicable and equitable.

      

      

      (d)          The purchase price of shares of Common
          Stock acquired pursuant to Purchase Rights will be not less than the lesser of:

      

      

      (i)          an amount equal to 85% of the Fair
          Market Value of the shares of Common Stock on the Offering Date; or

      

      

      (ii)          an amount equal to 85% of the Fair
          Market Value of the shares of Common Stock on the applicable Purchase Date.

      

      

      7.          Participation;
            Withdrawal; Termination.

      

      

      (a)          An Eligible Employee may elect to
          authorize payroll deductions as the means of making Contributions by completing and delivering to the Company, within the time specified in the Offering, an enrollment form provided by the Company. The enrollment form will specify the amount of
          Contributions not to exceed the maximum amount specified by the Board. Each Participant’s Contributions will be credited to a bookkeeping account for such Participant under the Plan and will be deposited with the general funds of the Company
          except where applicable law requires that Contributions be deposited with a third party. If permitted in the Offering, a Participant may begin such Contributions with the first payroll occurring on or after the Offering Date (or, in the case of a
          payroll date that occurs after the end of the prior  Offering but before the Offering Date of the next new Offering, Contributions from such payroll will be included in the new Offering). If permitted in the Offering, a Participant may thereafter
          reduce (including to zero) or increase his or her Contributions. If specifically provided in the Offering, in addition to making Contributions by payroll deductions, a Participant may make Contributions through the payment by cash or check prior
          to a Purchase Date.

      
        
          

      

      (b)         During an Offering, a Participant may
          cease making Contributions and withdraw from the Offering by delivering to the Company a withdrawal form provided by the Company. The Company may impose a deadline before a Purchase Date for withdrawing. Upon such withdrawal, such Participant’s
          Purchase Right in that Offering will immediately terminate and the Company will distribute to such Participant all of his or her accumulated but unused Contributions and such Participant’s Purchase Right in that Offering shall thereupon
          terminate. A Participant’s withdrawal from that Offering will have no effect upon his or her eligibility to participate in any other Offerings under the Plan, but such Participant will be required to deliver a new enrollment form to participate
          in subsequent Offerings.

      

      

      (c)          Purchase Rights granted pursuant to
          any Offering under the Plan will terminate immediately if the Participant either (i) is no longer an Employee for any reason or for no reason (subject to any post-employment participation period required by law) or (ii) is otherwise no longer
          eligible to participate. The Company will distribute to such individual all of his or her accumulated but unused Contributions.

      

      

      (d)         During a Participant’s lifetime,
          Purchase Rights will be exercisable only by such Participant. Purchase Rights are not transferable by a Participant, except by will, by the laws of descent and distribution, or, if permitted by the Company, by a beneficiary designation as
          described in Section 10.

      

      

      (e)          Unless otherwise specified in the
          Offering, the Company will have no obligation to pay interest on Contributions.

      

      

      8.          Exercise of Purchase Rights.

      

      

      (a)          On each Purchase Date, each
          Participant’s accumulated Contributions will be applied to the purchase of shares of Common Stock, up to the maximum number of shares of Common Stock permitted by the Plan and the applicable Offering, at the purchase price specified in the
          Offering. No fractional shares will be issued unless specifically provided for in the Offering.

      

      

      (b)          Unless otherwise provided in the
          Offering, if any amount of accumulated Contributions remains in a Participant’s account after the purchase of shares of Common Stock and such remaining amount is less than the amount required to purchase one share of Common Stock on the final
          Purchase Date of an Offering, then such remaining amount will be held in such Participant’s account for the purchase of shares of Common Stock under the next Offering under the Plan, unless such Participant withdraws from or is not eligible to
          participate in such next Offering, in which case such amount will be distributed to such Participant after the final Purchase Date without interest. If the amount of Contributions remaining in a Participant’s account after the purchase of shares
          of Common Stock is at least equal to the amount required to purchase one (1) whole share of Common Stock on the final Purchase Date of an Offering, then such remaining amount will be distributed in full to such Participant after the final
          Purchase Date of such Offering without interest.

      

      

      (c)          No Purchase Rights may be exercised to
          any extent unless the shares of Common Stock to be issued upon such exercise under the Plan are covered by an effective registration statement pursuant to the Securities Act and the Plan is in material compliance with all applicable federal,
          state, foreign and other securities and other laws applicable to the Plan. If on a Purchase Date the shares of Common Stock are not so registered or the Plan is not in such compliance, no Purchase Rights will be exercised on such Purchase Date,
          and the Purchase Date will be delayed until the shares of Common Stock are subject to such an effective registration statement and the Plan is in material compliance, except that the Purchase Date will in no event be more than 6 months from the
          Offering Date. If, on the Purchase Date, as delayed to the maximum extent permissible, the shares of Common Stock are not registered and the Plan is not in material compliance with all applicable laws, no Purchase Rights will be exercised and all
          accumulated but unused Contributions will be distributed to the Participants without interest.

      
        
          

      

      9.          Covenants
            of the Company.

      

      

      The Company will seek to obtain from each federal, state, foreign or other regulatory commission or agency having jurisdiction over the Plan such
        authority as may be required to grant Purchase Rights and issue and sell shares of Common Stock thereunder. If, after commercially reasonable efforts, the Company is unable to obtain the authority that counsel for the Company deems necessary for
        the grant of Purchase Rights or the lawful issuance and sale of Common Stock under the Plan, and at a commercially reasonable cost, the Company will be relieved from any liability for failure to grant Purchase Rights and/or to issue and sell Common
        Stock upon exercise of such Purchase Rights.

      

      

      10.          Designation of Beneficiary.

      

      

      (a)          The Company may, but is not obligated
          to, permit a Participant to submit a form designating a beneficiary who will receive any shares of Common Stock and/or Contributions from the Participant’s account under the Plan if the Participant dies before such shares and/or Contributions are
          delivered to the Participant. The Company may, but is not obligated to, permit the Participant to change such designation of beneficiary. Any such designation and/or change must be on a form approved by the Company.

      

      

      (b)          If a Participant dies, and in the
          absence of a valid beneficiary designation, the Company will deliver any shares of Common Stock and/or Contributions to the executor or administrator of the estate of the Participant. If no executor or administrator has been appointed (to the
          knowledge of the Company), the Company, in its sole discretion, may deliver such shares of Common Stock and/or Contributions to the Participant’s spouse, dependents or relatives, or if no spouse, dependent or relative is known to the Company,
          then to such other person as the Company may designate.

      

      

      11.          Adjustments upon Changes in Common Stock; Corporate Transactions.

      

      

      (a)          In the event of a Capitalization
          Adjustment, the Board will 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 by which the share reserve
          is to increase automatically each year pursuant to Section 3(a), (iii) the class(es) and number of securities subject to, and the purchase price applicable to outstanding Offerings and Purchase Rights, and (iv) the class(es) and number of
          securities that are the subject of the purchase limits under each ongoing Offering. The Board will make these adjustments, and its determination will be final, binding and conclusive.

      

      

      (b)          In the event of a Corporate
          Transaction, then: (i) any surviving corporation or acquiring corporation (or the surviving or acquiring corporation’s parent company) may assume or continue outstanding Purchase Rights or may substitute similar rights (including a right to
          acquire the same consideration paid to the stockholders in the Corporate Transaction) for outstanding Purchase Rights, or (ii) if any surviving or acquiring corporation (or its parent company) does not
          assume or continue such Purchase Rights or does not substitute similar rights for such Purchase Rights, then the Participants’ accumulated Contributions will be used to purchase shares of Common Stock within ten business days prior to the
          Corporate Transaction under the outstanding Purchase Rights, and the Purchase Rights will terminate immediately after such purchase.

      
        
          

      

      12.          Amendment, Termination or Suspension of the Plan.

      

      

      (a)          The Board may amend the Plan at any
          time in any respect the Board deems necessary or advisable. However, except as provided in Section 11(a) relating to Capitalization Adjustments, stockholder approval will be required for any amendment of the Plan for which stockholder approval is
          required by applicable law or listing requirements.

      

      

      (b)          The Board may suspend or terminate the
          Plan at any time. No Purchase Rights may be granted under the Plan while the Plan is suspended or after it is terminated.

      

      

      (c)          Any benefits, privileges, entitlements
          and obligations under any outstanding Purchase Rights granted before an amendment, suspension or termination of the Plan will not be materially impaired by any such amendment, suspension or termination except (i) with the consent of the person to
          whom such Purchase Rights were granted, (ii) as necessary to comply with any laws, listing requirements, or governmental regulations (including, without limitation, the provisions of Section 423 of the Code and the regulations and other
          interpretive guidance issued thereunder relating to Employee Stock Purchase Plans) including without limitation any such regulations or other guidance that may be issued or amended after the date the Plan is adopted by the Board, or (iii) as
          necessary to obtain or maintain favorable tax, listing, or regulatory treatment. To be clear, the Board may amend outstanding Purchase Rights without a Participant’s consent if such amendment is necessary to ensure that the Purchase Right and/or
          the Plan complies with the requirements of Section 423 of the Code.

      

      

      Notwithstanding anything in the Plan or any Offering Document to the contrary, the Board will be entitled to: (i) establish the exchange ratio
        applicable to amounts withheld in a currency other than U.S. dollars; (ii) permit Contributions in excess of the amount designated by a Participant in order to adjust for mistakes in the Company’s processing of properly completed Contribution
        elections; (iii) establish reasonable waiting and adjustment periods and/or accounting and crediting procedures to ensure that amounts applied toward the purchase of Common Stock for each Participant properly correspond with amounts withheld from
        the Participant’s Contributions; (iv) amend any outstanding Purchase Rights or clarify any ambiguities regarding the terms of any Offering to enable the Purchase Rights to qualify under and/or comply with Section 423 of the Code; and (v) establish
        other limitations or procedures as the Board determines in its sole discretion advisable that are consistent with the Plan. The actions of the Board pursuant to this paragraph will not be considered to alter or impair any Purchase Rights granted
        under an Offering as they are part of the initial terms of each Offering and the Purchase Rights granted under each Offering.

      

      

      13.          Effective Date of Plan.

      

      

      The Plan will become effective immediately prior to and contingent upon the IPO Date. No Purchase Rights will be exercised unless and until the Plan
        has been approved by the stockholders of the Company, which approval must be within 12 months before or after the date the Plan is adopted (or if required under Section 12(a) above, materially amended) by the Board.

      
        
          

      

      14.          Miscellaneous Provisions.

      

      

      (a)          Proceeds from the sale of shares of
          Common Stock pursuant to Purchase Rights will constitute general funds of the Company.

      

      

      (b)          A Participant will not be deemed to
          be the holder of, or to have any of the rights of a holder with respect to, shares of Common Stock subject to Purchase Rights unless and until the Participant’s shares of Common Stock acquired upon exercise of Purchase Rights are recorded in the
          books of the Company (or its transfer agent).

      

      

      (c)          The Plan and Offering do not
          constitute an employment contract. Nothing in the Plan or in the Offering will in any way alter the at will nature of a Participant’s employment or be deemed to create in any way whatsoever any obligation on the part of any Participant to
          continue in the employ of the Company or a Related Corporation, or on the part of the Company or a Related Corporation to continue the employment of a Participant.

      

      

      (d)          The provisions of the Plan will be
          governed by the laws of the State of Delaware without resort to that state’s conflicts of laws rules.

      

      

      15.          Definitions.

      

      

      As used in the Plan, the following definitions will apply to the capitalized terms indicated below:

      

      

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

      

      

      (b)          “Capital Stock” means each and every class of common stock of the Company, regardless of the number of votes per share.

      

      

      (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 Purchase Right after the date the Plan is adopted by the
          Board without the receipt of consideration by the Company through merger, consolidation, reorganization, recapitalization, reincorporation, stock dividend, dividend in property other than cash, large nonrecurring cash dividend, stock split,
          liquidating dividend, combination of shares, exchange of shares, change in corporate structure or other similar equity restructuring transaction, as that term is used in Financial Accounting Standards Board Accounting Standards Codification Topic
          718 (or any successor thereto). Notwithstanding the foregoing, the conversion of any convertible securities of the Company will not be treated as a Capitalization Adjustment.

      

      

      (d)          “Code” means the Internal Revenue Code of 1986, as amended, including any applicable regulations and guidance thereunder.

      

      

      (e)          “Committee” means a committee of one or more members of the Board to whom authority has been delegated by the Board in accordance with Section 2(c).

      

      

      (f)          “Common Stock” means, as of the IPO Date, the common stock of the Company.

      

      

      (g)          “Company” means Castle Biosciences, Inc., a Delaware corporation.

      

      

      (h)          “Contributions” means the payroll deductions and other additional payments specifically provided for in the Offering that a Participant contributes to fund the exercise of a Purchase Right. A Participant may make
          additional payments into his or her account if specifically provided for in the Offering, and then only if the Participant has not already had the maximum permitted amount withheld during the Offering through payroll deductions.

      
        
          

      

      (i)          “Corporate Transaction” means the consummation, in a single transaction or in a series of related transactions, of any one or more of the following events:

      

      

      (i)          a sale or
          other disposition of all or substantially all, as determined by the Board in its sole discretion, of the consolidated assets of the Company and its subsidiaries;

      

      

      (ii)          a sale or other disposition of more
          than 50% of the outstanding securities of the Company;

      

      

      (iii)        a merger, consolidation or similar
          transaction following which the Company is not the surviving corporation; or

      

      

      (iv)        a merger, consolidation or similar
          transaction following which the Company is the surviving corporation but the shares of Common Stock outstanding immediately preceding the merger, consolidation or similar transaction are converted or exchanged by virtue of the merger,
          consolidation or similar transaction into other property, whether in the form of securities, cash or otherwise.

      

      

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

      

      

      (k)          “Eligible Employee” means an Employee who meets the requirements set forth in the document(s) governing the Offering for eligibility to participate in the Offering, provided
          that such Employee also meets the requirements for eligibility to participate set forth in the Plan.

      

      

      (l)           “Employee” means any person, including an Officer or Director, who is “employed” for purposes of Section 423(b)(4) of the Code by the Company or a Related Corporation. However,
          service solely as a Director, or payment of a fee for such services, will not cause a Director to be considered an “Employee” for purposes of the Plan.

      

      

      (m)         “Employee Stock Purchase Plan” means a plan that grants Purchase Rights intended to be options issued under an “employee stock purchase plan,” as that term is defined in
          Section 423(b) of the Code.

      

      

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

      

      

      (o)          “Fair Market Value” means, as of any date, the value of the Common Stock determined as follows:

      

      

      (i)          If the Common Stock is listed on any
          established stock exchange or traded on any established market, the Fair Market Value of a share of Common Stock will be, unless otherwise determined by the Board, the closing sales price for such
          stock as quoted on such exchange or market (or the exchange or market with the greatest volume of trading in the Common Stock) on the date of determination, as reported in such source as the Board
          deems reliable. Unless otherwise provided by the Board, if there is no closing sales price for the Common Stock on the date of determination, then the Fair Market Value will be the closing sales price on the last preceding date for which such
          quotation exists.

      
        
          

      

      (ii)          In the absence of such markets for
          the Common Stock, the Fair Market Value will be determined by the Board in good faith in compliance with applicable laws and in a manner that complies with Sections 409A of the Code.

      

      

      (iii)        Notwithstanding the foregoing, for
          any Offering that commences on the IPO Date, the Fair Market Value of the shares of Common Stock on the Offering Date will be the price per share at which shares are first sold to the public in the Company’s initial public offering as specified
          in the final prospectus for that initial public offering.

      

      

      (p)          “IPO Date” means the date of the underwriting agreement between the Company and the underwriter(s) managing the initial public offering of the Common Stock, pursuant to which
          the Common Stock is priced for the initial public offering.

      

      

      (q)          “Offering” means the grant to Eligible Employees of Purchase Rights, with the exercise of those Purchase Rights automatically occurring at the end of one or more Purchase
          Periods. The terms and conditions of an Offering will generally be set forth in the “Offering Document” approved by the Board for that Offering.

      

      

      (r)          “Offering Date” means a date selected by the Board for an Offering to commence.

      

      

      (s)           “Officer” means a person who is an officer of the Company or a Related Corporation within the meaning of Section 16 of the Exchange Act.

      

      

      (t)          “Participant” means an Eligible Employee who holds an outstanding Purchase Right.

      

      

      (u)          “Plan” means this Castle Biosciences, Inc. 2019 Employee Stock Purchase Plan.

      

      

      (v)          “Purchase Date” means one or more dates during an Offering selected by the Board on which Purchase Rights will be exercised and on which purchases of shares of Common Stock
          will be carried out in accordance with such Offering.

      

      

      (w)        “Purchase Period” means a period of time specified within an Offering, generally beginning on the Offering Date or on the first Trading Day following a Purchase Date, and ending on a Purchase Date. An Offering may
          consist of one or more Purchase Periods.

      

      

      (x)          “Purchase Right” means an option to purchase shares of Common Stock granted pursuant to the Plan.

      

      

      (y)          “Related Corporation” means any “parent corporation” or “subsidiary corporation” of the Company whether now or subsequently established, as those terms are defined in Sections
          424(e) and (f), respectively, of the Code.

      

      

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

      
        
          

      

      (aa)       “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 will 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%). For purposes of the foregoing clause (i), the Company will be deemed to “Own” or have “Owned” such securities if the Company, 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.

          

        

      (bb)       “Trading Day” means any day on which the exchange(s) or market(s) on which shares of Common Stock are listed, including but not limited to the NYSE, Nasdaq Global Select Market,
          the Nasdaq Global Market, the Nasdaq Capital Market or any successors thereto, is open for trading.Exhibit 10.18

    

     

    

    
      Castle Biosciences, Inc.

      Non-Employee Director Compensation Policy

      Adopted:  July 11, 2019

      

      

      Each member of the Board of Directors (the “Board”) of Castle Biosciences, Inc. (the “Company”) who is a non-employee director of the Company (each
        such member, a “Non-Employee Director”) will receive the compensation described in this Non-Employee Director Compensation
        Policy (the “Director Compensation Policy”) for his or her Board service following the closing of the initial public offering of the Company’s common stock (the “IPO”).

      

      

      The Director Compensation Policy will be effective upon the execution of the underwriting agreement in connection with the IPO (the date of such
        execution being referred to as the “IPO Date”). The Director Compensation Policy may be amended at any time in the sole
        discretion of the Board or the Compensation Committee of the Board.

      

      

      A Non-Employee Director may decline all or any portion of his or her compensation by giving notice to the Company prior to the date cash is to be paid or
        equity awards are to be granted, as the case may be.

      

      

      Annual Cash Compensation

      

      

      Commencing at the beginning of the first calendar quarter following the IPO Date, each Non-Employee Director will receive the cash compensation set forth
        below for service on the Board.  The annual cash compensation amounts will be payable in equal quarterly installments, in arrears following the end of each quarter in which the service occurred, pro-rated for any partial months of service.  All
        annual cash fees are vested upon payment.

      

      

      
        
          	1.	
                  Annual Board Service Retainer:

                

        

      

      a.          All Eligible Directors:
          $36,000

      

      

      
        
          	2.	
                  Annual Board Chair Service Retainer (in addition to Board Service Retainer):

                

        

      

      a.          Chair of the Board:
          $40,000

      

      

      3.          Annual Committee Member Service Retainer:

      a.          Member of the Audit
          Committee: $7,500

      b.          Member of the
          Compensation Committee: $5,000

      c.          Member of the Nominating
          and Corporate Governance Committee: $4,000

      

      

      
        
          	4.	
                  Annual Committee Chair Service Retainer (in addition to Committee Member Service
                        Retainer):

                

        

      

      a.          Chair of the Audit
          Committee: $7,500

      b.          Chair of the
          Compensation Committee: $5,000

      c.          Chair of the Nominating
          and Corporate Governance Committee: $4,000

      
        1.

        
          

      

      
      Equity Compensation

      

      

      Equity awards will be granted under the Company’s 2019 Equity Incentive Plan (the “Plan”), adopted in connection with the IPO.  All stock options granted under this policy will be Nonstatutory Stock Options (as defined in the Plan), with a term of ten
        years from the date of grant and an exercise price per share equal to 100% of the Fair Market Value (as defined in the Plan) of the underlying common stock of the Company on the date of grant.

      

      

      (a)          Automatic
          Equity Grants.

                

      

      (i)          Initial Grant for New Directors.   Without any further action of the Board, each person who, after the IPO Date, is elected or appointed for the first time to be a
          Non-Employee Director will automatically, upon the date of his or her initial election or appointment to be a Non-Employee Director (or, if such date is not a market trading day, the first market trading day thereafter), be granted a Nonstatutory
          Stock Option to purchase 30,895 shares of common stock of the Company (the “Initial Option Grant”).  Each Initial Option
          Grant will vest in a series of 36 successive equal monthly installments over the three-year period measured from the date of grant.

                

      

      (ii)        Annual Grant.  Without any further action of the Board, at the close of business on the date of each Annual Meeting of Stockholders following the IPO, each person
          who is then a Non-Employee Director will automatically be granted a Nonstatutory Stock Option to purchase 15,448 shares of common stock (the “Annual Option Grant”).  Each Annual Option Grant will vest on the one-year anniversary of the date of grant.

                

      

      (b)          Vesting; Change in Control.  All vesting is subject to the Non-Employee Director’s “Continuous Service” (as defined in the Plan) on each applicable vesting date.  Notwithstanding the foregoing vesting schedules, for each Non-Employee Director who remains in Continuous Service with
          the Company until immediately prior to the closing of a “Change in Control” (as defined in the Plan), the shares subject to
          his or her then-outstanding equity awards that were granted pursuant to this policy will become fully vested immediately prior to the closing of such Change in Control.

               

      

      (c)          Remaining Terms.  The remaining terms and conditions of each award, including transferability, will be as set forth in the Company’s Director Option Grant Package in
          the form adopted from time to time by the Board.

            

      

      Expenses

      

      

      The Company will reimburse Non-Employee Director for ordinary, necessary and
          reasonable out-of-pocket travel expenses to cover in-person attendance at and participation in Board and committee meetings; provided, that the Non-Employee Director timely submit to the Company appropriate documentation substantiating such expenses in accordance with the Company’s travel and expense
          policy, as in effect from time to time.

      

      

    

  

  2.

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