Employment Letter dated May 31, 2017, between Oncternal Therapeutics, Inc. and James B. Breitmeyer, M.D., Ph.D

DUTIES. You shall continue to serve as, and shall perform such duties as are customarily associated with the position of, President and Chief Executive Officer and such other duties as are assigned to you by the Board of Directors of the Company (the “Board”). You shall report to the Board and shall perform your services on a full-time basis. You shall devote your full working time and attention to the business affairs of the Company.

COMPENSATION. Your compensation will be as follows:

BASE SALARY. You will receive an annual base salary of $475,000.00 for all hours worked to be paid in accordance with the Company’s customary payroll procedures.

ANNUAL BONUS. In addition to your base salary, you may be eligible to earn an annual cash performance bonus under the Company’s bonus plan, if and when such a bonus plan is approved from time to time by the Board. In the event the Board implements an annual bonus plan, your maximum annual bonus will be a percentage of your base salary actually paid for the year to which such annual bonus relates. The Board will consult with you in good faith in evaluating the annual target bonus amounts. You must be employed by the Company on the date of payment of such annual bonus in order to be eligible to receive such annual bonus. You hereby acknowledge and agree that nothing contained herein confers upon you any right to an annual bonus in any year, and that whether the Company pays you an annual bonus and the amount of any such annual bonus will be determined by the Company in its sole discretion.

BENEFITS. You shall be eligible to participate in all of the employee benefit plans or programs the Company generally makes available to similarly situated employees, pursuant to the terms and conditions of such plans. You will initially be entitled to 20 days of paid time off each year, accruing on a monthly basis, and all holidays observed by the Company each year. The Company reserves the right to change compensation and benefits provided to its employees from time to time in its discretion.

WITHHOLDING. All amounts payable to you will be subject to appropriate payroll deductions and withholdings.

SEVERANCE.

Subject to your continued compliance with the Company’s Proprietary Information and Inventions Agreement, if your employment is terminated by the Company without Cause (as defined below) (and other than by reason of your death or Disability (as defined below)) or you resign for Good Reason (as defined below), you shall be entitled to receive, in lieu of any severance benefits to which you may otherwise be entitled under any severance plan or program of the Company, the benefits provided below:

Your fully earned but unpaid base salary, through the date such termination is effective at the rate then in effect, and all other amounts or benefits to which you are entitled under any compensation, retirement or benefit plan of the Company at the time of your termination of employment in accordance with the terms of such plans, including, without limitation, any continuation of benefits required by COBRA or applicable law;

Your monthly base salary as in effect immediately prior to the date of your termination of employment for 6 months (the “Severance Period”), payable in accordance with the Company’s usual payroll practices (and in any event no less frequently than monthly), with the first installment commencing on the first payroll date that is 60 days following the date of your termination of employment (and any installment payments which would otherwise have been paid to you before the 60^th day following the date of your termination of employment will be paid together with the first installment) (provided, however, that in the event such termination by the Company without Cause or resignation for Good Reason occurs following the occurrence of either a Qualifying Financing(s) (as defined below) or a Change in Control (as defined below), the Severance Period shall be increased to 12 months and the cash severance shall instead be paid in a lump sum on the Company’s first regularly-scheduled payroll date after the effective date of the “Release” (as defined below)); and

For the Severance Period (or, if earlier, (1) the date on which the applicable continuation period under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”) expires or (2) the date you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or self-employment) (such period, the “COBRA Coverage Period”), if you and/or your eligible dependents who were covered under the Company’s health insurance plans as of the date of your termination of employment elect to have COBRA coverage and are eligible for such coverage, the Company shall pay for or reimburse you on a monthly basis for an amount equal to (A) the monthly premium you and/or your covered dependents, as applicable, are required to pay for continuation coverage pursuant to COBRA for you and/or your eligible dependents, as applicable, who were covered under the Company’s health plans as of the date of your termination of employment (calculated by reference to the premium as of the date of your termination of employment) less (B) the amount you would have had to pay to receive group health coverage for you

In addition, you shall be entitled to the following additional Stock Award (as defined below) acceleration under the circumstances described below:

Upon a Change in Control, 50% of your unvested Stock Awards shall be automatically accelerated immediately prior to the occurrence of such Change in Control.

In the event your termination by the Company without Cause or your resignation for Good Reason occurs within 90 days prior to or at any time following a Change in Control, the vesting and/or exercisability of all of your outstanding unvested Stock Awards (as defined below) shall be automatically accelerated in full on the later of (a) the date of your termination of employment or (b) the date of the Change in Control.

Upon the termination of your employment by reason of your death or Disability (as defined below), the vesting and/or exercisability of all of your outstanding unvested Stock Awards (as defined below) shall be automatically accelerated in full on the date of your termination of employment.

The foregoing provisions are hereby deemed to be a part of each Stock Award and to supersede any less favorable provision in any agreement or plan regarding such Stock Award. For purposes of this Agreement, “Stock Awards” means all stock options, restricted stock and such other awards granted pursuant to the Company’s stock option and equity incentive award plans or agreements and any shares of stock issued upon exercise thereof; provided, however, “Stock Awards” shall not include the founders’ shares issued to you pursuant to that certain Restricted Stock Purchase Agreement dated as of February 26, 2016, as amended, the terms of which agreement shall govern the accelerated vesting of such shares.

As a condition to your receipt of any post-termination payments and benefits pursuant to the preceding paragraphs, you shall execute and not revoke a general release of all claims in favor of the Company (the “Release”) in a form acceptable to the Company. In the event the Release does not become effective within the 55-day period following the date of your termination of employment, you will not be entitled to the aforesaid payments and benefits.

For purposes of this Agreement, “Cause” means any of the following: (a) your unauthorized use or disclosure of confidential information or trade secrets of the Company or any material breach of a written agreement between you and the Company, including without limitation a material breach of any employment, consulting, confidentiality, non-compete, non-solicit or similar agreement; (b) your commission of, indictment for or the entry of a plea of guilty or nolo contendere by you to, a felony under the laws of the United States or any state thereof or any crime involving dishonesty or moral turpitude (or any similar crime in any jurisdiction outside the United States); (c) your gross negligence or willful misconduct or your willful or repeated failure or refusal to substantially perform assigned duties; or (d) any act of fraud, embezzlement, material misappropriation or dishonesty committed by you against the Company. The foregoing definition shall not in any way preclude or restrict the right of the Company or any successor or affiliate thereof to discharge or dismiss you for any other acts or omissions, but such other acts or omissions shall not be deemed, for purposes of this Agreement, to constitute grounds for termination for Cause.

For purposes of this Agreement, a “Change in Control” shall have the meaning given to such term in the Company’s 2015 Equity Incentive Plan.

For purposes of this Agreement, “Disability” shall mean a permanent and total disability within the meaning of Section 22(e)(3) of the Code, as it may be amended from time to time.

For purposes of this Agreement, “Good Reason” shall mean the occurrence of any of the following events or conditions without your consent: (a) a change in your position with the Company (or its subsidiary employing you) that materially reduces your authority, duties or responsibilities; (b) a material diminution in the level of your base compensation, except in connection with a general reduction in the base compensation of the Company’s personnel with similar status and responsibilities; (c) a relocation of your place of employment by more than 50 miles, provided that such change, reduction or relocation is effected by the Company (or its subsidiary employing you) without your consent; or (d) any material breach by the Company of its obligations to you under this agreement. Notwithstanding the foregoing, Good Reason shall only exist if you shall have provided the Company with written notice within 60 days of the initial occurrence of any of the foregoing events or conditions, and the Company or any successor or affiliate fails to eliminate the conditions constituting Good Reason within 30 days after receipt of written notice of such event or condition from you. Your resignation from employment with the Company for “Good Reason” must occur within six months following the initial occurrence of one of the foregoing events or conditions.

For purposes of this Agreement, “Qualifying Financing(s)” shall mean the consummation of one or more equity financings yielding, within any 6 month period, aggregate gross proceeds to the Company of at least $20,000,000 in which investors purchase shares of the Company’s Series C preferred stock or other equity securities.

To the extent applicable, this Agreement shall be interpreted in accordance with Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), and Department of Treasury regulations and other interpretive guidance issued thereunder. To the extent that any provision in this Agreement is ambiguous as to its compliance with Section 409A of the Code, the provision shall be read in such a manner that no payments payable under this Agreement shall be subject to an “additional tax” as defined in Section 409A(a)(1)(B) of the Code. For purposes of Section 409A of the Code, the right to a series of installment payments under this Agreement shall be treated as a right to a series of separate payments. For purposes of this Agreement, all references to your “termination of employment” shall mean your “separation from service” (as defined in Treasury Regulation Section 1.409A-1(h)). If you are a “specified employee” (as defined in Section 409A of the Code), as determined by the Company in accordance with Section 409A of the Code, on the date of your termination of employment, to the extent that the payments or benefits under this Agreement are subject to Section 409A of the Code and the delayed payment or distribution of all or any portion of such amounts to which you are entitled under this Agreement is required in order to avoid a prohibited distribution under Section 409A(a)(2)(B)(i) of the Code, then such portion deferred pursuant to this paragraph shall be paid or distributed to you in a lump sum on the earlier of (a) the date that is six months and one day following your “separation from service” (as defined in Treasury Regulation Section 1.409A-1(h)), (b) the date of your death or (c) the earliest date as is permitted under Section 409A of the Code. Any remaining payments due under this Agreement shall be paid as otherwise provided herein.

Any reimbursement of expenses or in-kind benefits payable under this Agreement shall be made in accordance with Treasury Regulation Section 1.409A-3(i)(1)(iv) and shall be paid on or before the last day of your taxable year following the taxable year in which you incurred the expenses. The amount of expenses reimbursed or in-kind benefits payable in one year shall not affect the amount eligible for reimbursement or in-kind benefits payable in any other taxable year of yours, and your right to reimbursement for such amounts shall not be subject to liquidation or exchange for any other benefit.

SECTION 280G; LIMITATIONS ON PAYMENT.

If any payment or benefit you will or may receive from the Company or otherwise (a “280G Payment”) would (a) constitute a “parachute payment” within the meaning of Section 280G of the Code, and (b) but for this sentence, be subject to the excise tax imposed by Section 4999 of the Code (the “Excise Tax”), then any such 280G Payment provided pursuant to this Agreement (a “Payment”) shall be equal to the Reduced Amount. The “Reduced Amount” shall be either (x) the largest portion of the Payment that would result in no portion of the Payment (after reduction) being subject to the Excise Tax or (y) the largest portion, up to and including the total, of the Payment, whichever amount (i.e., the amount determined by clause (x) or by clause (y)), after taking into account all applicable federal, state and local employment taxes, income taxes, and the Excise Tax (all computed at the highest applicable marginal rate), results in your receipt, on an after-tax basis, of the greater economic benefit notwithstanding that all or some portion of the Payment may be subject to the Excise Tax. If a reduction in a Payment is required pursuant to the preceding

Notwithstanding any provision herein to the contrary, if the Reduction Method or the Pro Rata Reduction Method would result in any portion of the Payment being subject to taxes pursuant to Section 409A that would not otherwise be subject to taxes pursuant to Section 409A, then the Reduction Method and/or the Pro Rata Reduction Method, as the case may be, shall be modified so as to avoid the imposition of taxes pursuant to Section 409A as follows: (A) as a first priority, the modification shall preserve to the greatest extent possible, the greatest economic benefit for you as determined on an after-tax basis; (B) as a second priority, Payments that are contingent on future events (e.g., being terminated without Cause), shall be reduced (or eliminated) before Payments that are not contingent on future events; and (C) as a third priority, Payments that are “deferred compensation” within the meaning of Section 409A shall be reduced (or eliminated) before Payments that are not deferred compensation within the meaning of Section 409A.

Unless you and the Company agree on an alternative accounting firm or law firm, the accounting firm engaged by the Company for general tax compliance purposes as of the day prior to the effective date of the Change in Control transaction shall perform the foregoing calculations. If the accounting firm so engaged by the Company is serving as accountant or auditor for the individual, entity or group effecting the Change in Control transaction, the Company shall appoint a nationally recognized accounting or law firm to make the determinations. The Company shall bear all expenses with respect to the determinations by such accounting or law firm required to be made hereunder. The Company shall use commercially reasonable efforts to cause the accounting or law firm engaged to make the determinations hereunder to provide its calculations, together with detailed supporting documentation, to you and the Company within 15 calendar days after the date on which your right to a 280G Payment becomes reasonably likely to occur (if requested at that time by you or the Company) or such other time as requested by you or the Company.

If you receive a Payment for which the Reduced Amount was determined pursuant to clause (x) above and the Internal Revenue Service determines thereafter that some portion of the Payment is subject to the Excise Tax, you agree to promptly return to the Company a sufficient amount of the Payment (after reduction pursuant to clause (x) above) so that no portion of the remaining Payment is subject to the Excise Tax. For the avoidance of doubt, if the Reduced Amount was determined pursuant to clause (y) above you shall have no obligation to return any portion of the Payment pursuant to the preceding sentence.