CytomX (CTMX) CMO sells 21,279 shares to cover RSU tax obligations

Rhea-AI Filing Summary

CytomX Therapeutics Chief Medical Officer Yu‑Waye Chu reported an open-market sale of 21,279 shares of common stock at $6.423 per share. According to the filing, the shares were sold solely to cover tax and other government withholding obligations tied to vesting restricted stock units. After this transaction, Chu directly holds 189,446 shares, which includes 149,833 RSUs that may settle in stock as they vest.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Chu Yu-Waye

(Last) (First) (Middle)

C/O CYTOMX THERAPEUTICS, INC.

151 OYSTER POINT BLVD, SUITE 400

(Street)

SOUTH SAN FRANCISCO CALIFORNIA 94080

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
CytomX Therapeutics, Inc. [ CTMX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Medical Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/17/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	03/17/2026		S(1)		21,279	D	$6.423	189,446(2)	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. The shares were sold solely to satisfy tax or other government withholding obligations in connection with the vesting of restricted stock units ("RSUs").

2. Includes 149,833 RSUs.

	/s/ Christopher Ogden, as Attorney-in-Fact for Yu-Waye Chu	03/19/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did CytomX (CTMX) report for Yu-Waye Chu?

CytomX reported that Chief Medical Officer Yu-Waye Chu sold 21,279 shares of common stock at $6.423 per share. The filing states the sale was solely to satisfy tax and other government withholding obligations related to vesting restricted stock units.

Was the CTMX insider sale by Yu-Waye Chu a discretionary stock sale?

The filing indicates it was not a discretionary sale. It states the shares were sold solely to satisfy tax or other government withholding obligations arising from the vesting of restricted stock units, which is a common, mechanistic step when equity awards vest.

How many CytomX (CTMX) shares does Yu-Waye Chu hold after the reported sale?

After the transaction, Yu-Waye Chu directly holds 189,446 shares of CytomX common stock. This figure includes 149,833 restricted stock units (RSUs), which represent additional stock-based awards that can convert into shares as they vest over time.

What price did Yu-Waye Chu receive per share in the CTMX stock sale?

The reported sale price was $6.423 per share of CytomX common stock. This price applied to the 21,279 shares sold to meet tax and other government withholding obligations associated with the vesting of restricted stock units granted as compensation.

What are the restricted stock units (RSUs) mentioned in the CTMX insider filing?

The filing notes that Yu-Waye Chu’s holdings include 149,833 RSUs. RSUs are stock-based awards that typically convert into common shares as they vest over time, forming a significant part of the executive’s equity compensation and potential future share ownership.

Does the CTMX Form 4 show any option exercises or derivative transactions?

The Form 4 data shows no derivative transactions or option exercises for this event. It reports only a single non-derivative open-market sale of 21,279 common shares, undertaken to satisfy tax and other withholding obligations related to vesting restricted stock units.