Amended and Restated Employment Letter Agreement, dated September 25, 2019, by and between Azmi Nabulsi, M.D., M.P.H. and the Registrant

Employment Letter

BASE SALARY. You will receive an annual base salary of $470,000 for all hours worked, less taxes, authorized withholdings and other legally required deductions. You will be paid in accordance with the Company’s customary payroll procedures as established and modified from time-to-time. Your base salary will be subject to annual review by and at the sole discretion of the Board of Directors (the “Board”) or its compensation committee.

ANNUAL BONUS. In addition to your base salary, you may be eligible to earn, for each fiscal year of the Company ending during the term of your employment with the Company, an annual cash performance bonus under the Company’s bonus plan, as approved from time to time by the Board. Your target annual bonus will be forty percent (40%) of your base salary actually paid for the year to which such annual bonus relates (your “Target Bonus”). Your actual annual

bonus will be determined on the basis of your and/or the Company’s attainment of financial or other performance criteria established by the Board or its designee in accordance with the terms and conditions of such bonus plan. 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 also be entitled to vacation and/or paid time off each year in accordance with Company policy 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.

ACCRUED OBLIGATIONS. If your employment terminates for any reason, you are entitled to 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 accrued but unpaid paid time off and any continuation of benefits required by applicable law (the “Accrued Obligations”).

NON-CIC SEVERANCE BENEFITS. In addition to your Accrued Obligations, subject to your continued compliance with the Proprietary Information and Inventions Assignment Agreement, as described below, and the effectiveness of your Release, as defined below, if, following the Employment Start Date, your employment is involuntarily terminated by the Company without Cause (as defined below) (and other than by reason of your death or disability) or you resign for Good Reason (as defined below)(either such termination, a “Qualifying Termination”), and such Qualifying Termination does not occur during the Change in Control Period (as defined below), you shall be entitled to receive, as the sole severance benefits to which you are entitled, the benefits provided below (the “Non-CIC Severance Benefits”):

An amount equal to 9 months’ base salary (at the rate in effect immediately prior to the date of your termination of employment, or in the case of a material diminution in your base salary which would give rise to Good Reason for your resignation, the base salary in effect prior to such material diminution), which amount will be paid over a period of 9 months following your termination of employment in accordance with the Company’s standard payroll practices, with the first such installment occurring on the first regularly-scheduled payroll date following the date your Release becomes effective (which first installment will include any installments that would have occurred prior to such date but for the fact your Release was not yet effective);

An amount equal to your Target Bonus for the calendar year in which your termination date occurs, prorated for the portion of the calendar year in which your termination date occurs that has elapsed prior to such termination, plus any unpaid annual bonus for the calendar year prior to the year in which your Qualifying Termination occurs, to the extent you are entitled to such bonus and if such bonus has not already been paid, which amount(s) will be paid in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective, but in no event more than 75 days following your termination date;

For the 9 month period beginning on the date of your termination of employment (or, if earlier, (a) the date on which the applicable continuation period under the Consolidated Omnibus Budget Reconciliation Act of 1985, as amended (“COBRA”) expires, or (b) the date on which 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 (i) 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 (ii) the amount you would have had to pay to receive group health coverage for you and/or your covered dependents, as applicable, based on the cost sharing levels in effect on the date of your termination of employment. If any of the Company’s health benefits are self-funded as of the date of your termination of employment, or if the Company cannot provide the foregoing benefits in a manner that is exempt from Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), or that is otherwise compliant with applicable law (including, without limitation, Section 2716 of the Public Health Service Act), instead of providing the payments or reimbursements as set forth above, the Company shall instead pay to you the foregoing monthly amount as a taxable monthly payment for the COBRA Coverage Period (or any remaining portion thereof). You shall be solely responsible for all matters relating to continuation of coverage pursuant to COBRA, including, without limitation, the election of such coverage and the timely payment of premiums. You shall notify the Company immediately if you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or self-employment; and

Notwithstanding anything else set forth herein, in the Plan or in any award agreement, such number of the unvested Stock Awards (as defined below) then held by you (including the Stock Options) will vest on the effective date of your Release as would have vested during the 9-month period following your Qualifying Termination had you remained employed by the Company during such period. 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.

CIC SEVERANCE BENEFITS. In addition to your Accrued Obligations, subject to your continued compliance with the Proprietary Information and Inventions Assignment Agreement, as described below, and the effectiveness of your Release, if your Qualifying Termination occurs following the Employment Start Date and during the Change in Control Period, you shall be entitled to receive, as the sole severance benefits to which you are entitled and in lieu of any Non-CIC Severance Benefits, the benefits provided below (the “CIC Severance Benefits”) (and for the avoidance of doubt: (a) in no event will you be entitled to both the Non-CIC Severance Benefits and the CIC Severance Benefits, and (b) if the Company has commenced providing the Non-CIC Severance Benefits to you prior to the date that you become eligible to receive the CIC Severance Benefits, the Non-CIC Severance Benefits previously provided to you shall reduce the CIC Severance Benefits provided below by the amount of such Non-CIC Severance Benefits already provided to you):

An amount equal to 12 months’ base salary (at the rate in effect immediately prior to the date of your termination of employment, or in the case of a material diminution in your base salary which would give rise to Good Reason for your resignation, the base salary in effect prior to such material diminution), which amount will be paid over a period of 12 months following your termination of employment in accordance with the Company’s standard payroll practices, with the first such installment occurring on the first regularly-scheduled payroll date following the date your Release becomes effective (which first installment will include any installments that would have occurred prior to such date but for the fact your Release was not yet effective);

An amount equal to your Target Bonus for the calendar year in which your termination date occurs, plus any unpaid annual bonus for the calendar year prior to the year in which your Qualifying Termination occurs, to the extent you are entitled to such bonus and if such bonus has not already been paid, which amount(s) will be paid as follows: (a) an amount equal to your Target Bonus for the calendar year in which your termination date occurs, prorated for the portion of the calendar year in which your termination date occurs that has elapsed prior to such termination, plus any unpaid annual bonus for the calendar year prior to

the year in which your Qualifying Termination occurs, to the extent you are entitled to such bonus and if such bonus has not already been paid, which amount(s) will be paid in a lump sum on the first regularly-scheduled payroll date following the date your Release becomes effective, but in no event more than 75 days following your termination date, and (b) any remaining portion of your Target Bonus for the calendar year in which your termination date occurs (above the prorated portion payable pursuant to clause (a)), will be paid on the first regularly-scheduled payroll date following the later of (i) the date your Release becomes effective or (ii) the date of the Change in Control;

For the 12 month period beginning on the date of your termination of employment (or, if earlier, (a) the date on which the applicable continuation period under COBRA expires, or (b) the date on which you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or self-employment) (such period, the “CIC 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 (i) 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 (ii) the amount you would have had to pay to receive group health coverage for you and/or your covered dependents, as applicable, based on the cost sharing levels in effect on the date of your termination of employment. If any of the Company’s health benefits are self-funded as of the date of your termination of employment, or if the Company cannot provide the foregoing benefits in a manner that is exempt from Section 409A of Code, or that is otherwise compliant with applicable law (including, without limitation, Section 2716 of the Public Health Service Act), instead of providing the payments or reimbursements as set forth above, the Company shall instead pay to you the foregoing monthly amount as a taxable monthly payment for the CIC COBRA Coverage Period (or any remaining portion thereof). You shall be solely responsible for all matters relating to continuation of coverage pursuant to COBRA, including, without limitation, the election of such coverage and the timely payment of premiums. You shall notify the Company immediately if you become eligible to receive the equivalent or increased healthcare coverage by means of subsequent employment or self-employment; and

Notwithstanding anything else set forth herein, in the Plan or in any award agreement, any unvested Stock Awards then held by you (including the Stock Options) will vest on the later of (i) the effective date of your Release or (ii) the date of the Change in Control. 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.

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 reasonably acceptable to the Company in order to effectuate a valid general release of claims. In the event the Release does not become effective within the 60-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 commission of an act of fraud, embezzlement or dishonesty, or the commission of some other illegal act by you, that has a demonstrable adverse impact on the Company or any successor or affiliate thereof; (b) your conviction of, or plea of “guilty” or “no contest” to, a felony or any crime involving fraud, dishonesty or moral turpitude under the laws of the United States or any state thereof; (c) any intentional, unauthorized use or disclosure by you of confidential information or trade secrets of the Company or any successor or affiliate thereof; (d) your gross negligence, insubordination or material violation of any duty of loyalty to the Company or any successor or affiliate thereof, or any other demonstrable material misconduct on your part; (e) your ongoing and repeated failure or refusal to perform or neglect of your duties as required by this Agreement or your ongoing and repeated failure or refusal to comply with the instructions given to you by the Board, which failure, refusal or neglect continues for 15 days following your receipt of written notice from the Board stating with specificity the nature of such failure, refusal or neglect; provided that it is understood that this clause (e) shall not permit the Company to terminate your employment for Cause solely because of (i) your failure to meet specified performance objectives or achieve a specific result or outcome, or (ii) Company’s dissatisfaction with the quality of services provided by you in the good faith performance of your duties to the Company; or (f) your willful, material breach of any material Company policy or any material provision of this Agreement or the Proprietary Information and Inventions Assignment Agreement. Prior to the determination that “Cause” under clauses (d), (e) or (f) has occurred, the Company shall (i) provide to you in writing, in reasonable detail, the reasons for the determination that such “Cause” exists, (ii) other than with respect to clause (e) above which specifies the applicable period of time for you to remedy your breach, afford you a reasonable opportunity to remedy any such breach, (iii) provide you an opportunity to be heard prior to the final decision to terminate your employment hereunder for such “Cause” and (iv) make any decision that such “Cause” exists in good faith. 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, “Change in Control” shall have the meaning set forth in the Plan. If a Change in Control would give rise to a payment or settlement event with respect to any payment or benefit that constitutes “nonqualified deferred compensation,” the transaction or event constituting the Change in Control must also constitute a “change in control event” (as defined in Treasury Regulation §1.409A-3(i)(5)) in order to give rise to the payment or settlement event for such payment or benefit, to the extent required by Section 409A.

For purposes of this Agreement, “Change in Control Period” means the three months prior to or 24 months following a Change in Control.

For purposes of this Agreement, “Good Reason” means any of the following without your written consent: (a) a material diminution in your authority, duties or responsibilities; (b) a material diminution in your base compensation (and you and the Company agree that any diminution of 10% or more shall be considered material for this purpose, regardless of whether such diminution occurs due to a single reduction or a series of reductions in your base compensation), unless such a reduction is imposed across-the-board to senior management of the Company; (c) a material change in the geographic location at which you must perform your duties (and you and the Company agree that a relocation of the geographic location at which you must perform your duties to a location that increases your one-way commute from your residence by more than 25 miles as compared to your principal place of employment prior to such relocation shall be considered material for this purpose); or (d) any other action or inaction that constitutes a material breach by the Company or any successor or affiliate of its obligations to you under this Agreement. You must provide written notice to the Company of the occurrence of any of the foregoing events or conditions without your written consent within 60 days of the occurrence of such event. The Company or any successor or affiliate shall have a period of 30 days to cure such event or condition after receipt of written notice of such event from you. Your termination of employment by reason of resignation from employment with the Company for Good Reason must occur within 30 days following the expiration of the foregoing 30-day cure period.

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, including the Stock Options.

To the extent applicable, this Agreement shall be interpreted in accordance with Section 409A of the Code and Department of Treasury regulations and other interpretive guidance issued thereunder. The intent of the parties is that payments and benefits under this Agreement comply with, or be exempt from Section 409A of the Code and, accordingly, to the maximum extent permitted, this Agreement shall be interpreted to be in compliance with such intention. To the extent that any provision in this Agreement is ambiguous as to its compliance with or exemption from 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, any 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)) (“Separation from Service”). 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 Separation from Service, to the extent that the payments or benefits under this Agreement are “non-qualified deferred compensation” 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 6 months and one day following your Separation from Service, (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.

To the extent that the payments or benefits under this Agreement are “non-qualified deferred compensation” subject to Section 409A of the Code, if the period during which you may deliver the Release required hereunder spans two calendar years, the payment of your post-termination benefits shall occur (or commence) on the later of (a) January 1 of the second calendar year, or (b) the first regularly-scheduled payroll date following the date your Release becomes effective.

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.

/s/ David Socks

/s/ Azmi Nabulsi