CytomX Therapeutics — Amendment No. 2 to a Schedule 13G/A reports that a group of Venrock-related entities and two individuals beneficially owned 9,982,124 shares of CytomX common stock as of March 31, 2026.
The filing states the group’s position consists of 2,107,644 shares held by Venrock Healthcare Capital Partners III, 210,912 shares held by VHCP Co-Investment Holdings III, and 7,663,568 shares held by Venrock Healthcare Capital Partners EG. The percentage figures are calculated using 170,186,742 shares outstanding as of February 28, 2026 plus 45,990,567 shares issued in a public offering that closed on March 19, 2026, producing the reported 4.6% ownership figure shown on the cover pages.
Positive
None.
Negative
None.
Insights
Venrock entities report a 4.6% passive stake in CytomX as of March 31, 2026.
The filing is a Schedule 13G/A group submission listing 9,982,124 shares beneficially owned in aggregate, with shared voting and dispositive power noted across the reporting persons. The ownership split among VHCP III, VHCP Co-Investment III and VHCP EG is explicitly disclosed.
Relevant dependencies include the share counts used to compute the percentage: 170,186,742 shares outstanding as of February 28, 2026 plus 45,990,567 shares issued in the issuer’s March public offering; timing and cash-flow treatment of those offering shares are provided by the prospectus supplement referenced in the filing.
This is a routine passive-ownership disclosure by an investment group, not an active transaction.
The report identifies shared dispositive and voting power of 9,982,124 shares as of March 31, 2026, and names the reporting persons and their organizational relationships (general partner/manager roles). The filing attaches powers of attorney and a joint filing agreement by reference.
Practical items to watch in subsequent filings include any amendment to the group’s ownership percentage or changes in sole versus shared power; such changes would appear in later Schedule 13 filings.
Key Figures
Reported aggregate beneficial ownership:9,982,124 sharesVHCP III holdings:2,107,644 sharesVHCP Co-Investment III holdings:210,912 shares+4 more
7 metrics
Reported aggregate beneficial ownership9,982,124 sharesas of March 31, 2026
VHCP III holdings2,107,644 sharesVHCP III beneficially owned
VHCP Co-Investment III holdings210,912 sharesVHCP Co-Investment Holdings III beneficially owned
VHCP EG holdings7,663,568 sharesVenrock Healthcare Capital Partners EG beneficially owned
Shares outstanding used for percentage170,186,742 sharesas of February 28, 2026 (plus offering shares)
Shares issued in public offering45,990,567 sharesissued in offering closed March 19, 2026
Reported ownership percentage4.6%cover page calculation basis described in filing
"Row 9 of each Reporting Person's cover page sets forth the aggregate number of shares beneficially owned"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
Schedule 13G/Aregulatory
"Amendment No. 2 to a Schedule 13G/A reports that the names of the persons filing this report (collectively, the "Reporting Persons")"
A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.
shared dispositive powerregulatory
"Shared Dispositive Power 9,982,124.00 appears on the cover rows for each Reporting Person"
cover page row referencesregulatory
"Row 9 of each Reporting Person's cover page to this /A sets forth the aggregate number of shares"
The Venrock group reported beneficial ownership of 9,982,124 shares as of March 31, 2026. The filing breaks this into 2,107,644, 210,912, and 7,663,568 share holdings across three Venrock entities.
How was the 4.6% ownership percentage calculated for CTMX?
The percentage uses 170,186,742 shares outstanding as of February 28, 2026 plus 45,990,567 shares issued in a public offering that closed on March 19, 2026. Those figures are cited in the filing as the denominator.
Who are the individuals named in the CTMX filing?
The filing names Nimish Shah and Bong Koh as voting members of the management entities. They are reported as United States citizens and as voting members of the VHCP management entities.
Does the filing show who controls voting or disposition of the shares?
Yes; the cover rows incorporated by reference show 0 sole voting/dispositive power and 9,982,124 shared voting and shared dispositive power for the reporting group as of the stated date.
Is this Schedule 13G/A an acquisition or a sale filing for CTMX?
This filing is a passive ownership report (Schedule 13G/A amendment) and discloses beneficial ownership as of a date; it does not report an acquisition or sale transaction in the filing text.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 2)
CytomX Therapeutics, Inc.
(Name of Issuer)
Common Stock, $0.00001 par value per share
(Title of Class of Securities)
23284F105
(CUSIP Number)
03/31/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
Venrock Healthcare Capital Partners III, L.P.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
VHCP Co-Investment Holdings III, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
Venrock Healthcare Capital Partners EG, L.P.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
VHCP Management III, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
VHCP Management EG, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
Nimish Shah
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
CUSIP Number(s):
23284F105
1
Names of Reporting Persons
Bong Y. Koh
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,982,124.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
9,982,124.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
9,982,124.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.6 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
CytomX Therapeutics, Inc.
(b)
Address of issuer's principal executive offices:
151 Oyster Point Blvd, Suite 400, South San Francisco, CA, 94080.
Item 2.
(a)
Name of person filing:
The names of the persons filing this report (collectively, the "Reporting Persons") are:
Venrock Healthcare Capital Partners III, L.P. ("VHCP III")
VHCP Co-Investment Holdings III, LLC ("VHCP Co-Investment III")
Venrock Healthcare Capital Partners EG, L.P. ("VHCP EG")
VHCP Management III, LLC ("VHCP Management III")
VHCP Management EG, LLC ("VHCP Management EG")
Nimish Shah ("Shah")
Bong Koh ("Koh")
The Reporting Persons are members of a group for the purposes of this Schedule 13G/A.
(b)
Address or principal business office or, if none, residence:
New York Office:
7 Bryant Park, 23rd Floor
New York, NY 10018
Palo Alto Office:
3340 Hillview Avenue
Palo Alto, CA 94304
(c)
Citizenship:
All of the entities were organized in Delaware. Shah and Koh are both United States citizens.
(d)
Title of class of securities:
Common Stock, $0.00001 par value per share
(e)
CUSIP No.:
23284F105
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
Row 9 of each Reporting Person's cover page to this Schedule 13G/A sets forth the aggregate number of shares of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
The Reporting Persons' ownership of the Issuer's securities consists of (i) 2,107,644 shares of common stock held by VHCP III, (ii) 210,912 shares of common stock held by VHCP Co-Investment III, and (iii) 7,663,568 shares of common stock held by VHCP EG.
VHCP Management III is the general partner of VHCP III and the manager of VHCP Co-Investment III. VHCP Management EG is the general partner of VHCP EG. Messrs. Shah and Koh are the voting members of VHCP Management III and VHCP Management EG.
(b)
Percent of class:
Row 11 of each Reporting Person's cover page to this Schedule 13G/A sets forth the percentages of the shares of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference. The percentage set forth in each row 11 is based upon the sum of (i) 170,186,742 shares of common stock outstanding as of February 28, 2026, as reported in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on March 16, 2026, and (ii) 45,990,567 shares of common stock issued in the Issuer's public offering of equity securities that closed on March 19, 2026, as reported in the Issuer's Prospectus Supplement dated March 17, 2026 filed with the SEC on March 18, 2026.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
Row 5 of each Reporting Person's cover page to this Schedule 13G/A sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
(ii) Shared power to vote or to direct the vote:
Row 6 of each Reporting Person's cover page to this Schedule 13G/A sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
(iii) Sole power to dispose or to direct the disposition of:
Row 7 of each Reporting Person's cover page to this Schedule 13G/A sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
(iv) Shared power to dispose or to direct the disposition of:
Row 8 of each Reporting Person's cover page to this Schedule 13G/A sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference
Item 5.
Ownership of 5 Percent or Less of a Class.
Ownership of 5 percent or less of a class
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
Not Applicable
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
Not Applicable
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
Venrock Healthcare Capital Partners III, L.P.
Signature:
/s/ Sherman G. Souther
Name/Title:
By VHCP Management III, LLC, its General Partner, By Sherman G. Souther, Authorized Signatory
Date:
05/15/2026
VHCP Co-Investment Holdings III, LLC
Signature:
/s/ Sherman G. Souther
Name/Title:
By VHCP Management III, LLC, its Manager, By Sherman G. Souther, Authorized Signatory
Date:
05/15/2026
Venrock Healthcare Capital Partners EG, L.P.
Signature:
/s/ Sherman G. Souther
Name/Title:
By VHCP Management EG, LLC, its General Partner, By Sherman G. Souther, Authorized Signatory
Date:
05/15/2026
VHCP Management III, LLC
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Authorized Signatory
Date:
05/15/2026
VHCP Management EG, LLC
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Authorized Signatory
Date:
05/15/2026
Nimish Shah
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Attorney-in-fact
Date:
05/15/2026
Bong Y. Koh
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Attorney-in-fact
Date:
05/15/2026
Exhibit Information
Exhibit 24.1 Power of Attorney for Bong Koh, dated May 20, 2025 (incorporated by reference to Exhibit 24.1 to Schedule 13G filed on May 20, 2025).
Exhibit 24.2 Power of Attorney for Nimish Shah, dated May 20, 2025 (incorporated by reference to Exhibit 24.2 to Schedule 13G filed on May 20, 2025).
Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to Schedule 13G filed on May 20, 2025).
