Washington, D.C. 20549


Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB Number: 3235-0287
Estimated average burden
hours per response: 0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
1. Name and Address of Reporting Person*
Dubois-Stringfellow Nathalie

(Last) (First) (Middle)


(City) (State) (Zip)
2. Issuer Name and Ticker or Trading Symbol
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director 10% Owner
X Officer (give title below) Other (specify below)
SVP-Chief Development Officer
3. Date of Earliest Transaction (Month/Day/Year)
4. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
X Form filed by One Reporting Person
Form filed by More than One Reporting Person
Rule 10b5-1(c) Transaction Indication

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 08/25/2023 F 1,462(1) D $0.77 140,634(2)(3) D
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year) 7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Explanation of Responses:
1. Represents shares underlying the portion of a restricted stock unit ("RSU") grant that vested on August 25, 2023, which were surrendered by the Reporting Person solely for mandatory tax withholding purposes using the Issuer's closing stock price on August 25, 2023 of $0.77/share, pursuant to the terms of the Issuer's Amended and Restated 2018 Equity Incentive Plan, as amended (the "2018 EIP"). This required tax withholding transaction is deemed to constitute a disposition of these shares to the Issuer for reporting purposes and does not represent a discretionary trade by the Reporting Person in the open market or otherwise.
2. Includes: (a) 2,766 shares resulting from the August 25, 2023 vesting installment of the Reporting Person's February 25, 2022 RSU grant, and the remaining 25,369 shares will vest in successive equal quarterly installments through February 25, 2025, (b) 8,001 shares subject to Reporting Person's February 25, 2021 RSU grant that will vest in one final installment on February 25, 2024 and (c) 53,438 shares subject to Reporting Person's February 24, 2023 RSU grant that will vest as to one-quarter (1/4) of the shares on the first anniversary of the grant date, and the remainder of the shares will vest in 8 successive equal quarterly installments thereafter. The vesting of all such RSU grants is subject to the Reporting Person's Continuous Service (as defined in the 2018 EIP) through each such date and subject to acceleration as provided in the 2018 EIP.
3. Includes 5,000 shares acquired on May 31, 2023 under the Issuer's 2020 Employee Stock Purchase Plan.
Nathalie Dubois-Stringfellow, by /s/ Ron A. Metzger, Attorney-in-Fact 08/29/2023
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.