Sec Form 4 Filing - GADICKE ANSBERT @ iTeos Therapeutics, Inc. - 2025-05-13

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

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person GADICKE ANSBERT 2. Issuer Name and Ticker or Trading Symbol iTeos Therapeutics, Inc. [ ITOS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner _____ Officer (give title below) X __ Other (specify below) Former 10% Owner (Last) (First) (Middle) C/O MPM BIOIMPACT LLC, 399 BOYLSTON STREET, SUITE 1100 3. Date of Earliest Transaction (MM/DD/YY) 05/13/2025 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 05/13/2025 S 1,031,931 ( 1 ) ( 2 ) D $ 8.06 ( 3 ) 3,452,797 I See Footnote ( 4 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other GADICKE ANSBERT C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 BOSTON, MA02116 Former 10% Owner MPM BioImpact LLC C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 BOSTON, MA02116 Former 10% Owner Oncology Impact Fund (Cayman) Management L.P. C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 BOSTON, MA02116 Former 10% Owner UBS Oncology Impact Fund L.P. C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 BOSTON, MA02116 Former 10% Owner Signatures /s/ Ansbert Gadicke 05/15/2025 Signature of Reporting Person Date /s/ Ansbert Gadicke, Managing Partner of MPM BioImpact LLC, the General Partner of Oncology Impact Fund (Cayman) Management L.P., the General Partner of UBS Oncology Impact Fund L.P 05/15/2025 Signature of Reporting Person Date /s/ Ansbert Gadicke, Managing Partner of MPM BioImpact LLC, the General Partner of Oncology Impact Fund (Cayman) Management L.P. 05/15/2025 Signature of Reporting Person Date /s/ Ansbert Gadicke, Managing Partner of MPM BioImpact LLC 05/15/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares were sold as follows: 355,406 by MPM BioVentures 2014, L.P. ("BV 2014"), 22,386 by MPM BioVentures 2014 (B), L.P. ("BV 2014(B)"), 12,233 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 224,467 by MPM BioVentures 2018, L.P. ("BV 2018"), 11,267 by MPM BioVentures 2018(B), L.P. ("BV 2018(B)"), 4,432 by MPM Asset Management Investors BV2018 LLC ("AM BV2018") and 401,740 by UBS Oncology Impact Fund L.P. ("UBS Oncology"). MPM BioVentures 2014 GP LLC and MPM BioVentures 2014 LLC ("BV 2014 LLC") are the direct and indirect general partners of BV 2014 and BV 2014(B). BV 2014 LLC is the manager of AM BV2014. MPM BioVentures 2018 GP LLC and MPM BioVentures 2018 LLC ("BV 2018 LLC") are the direct and indirect general partners of BV 2018 and BV 2018(B). BV 2018 LLC is the manager of AM BV2018. Ansbert Gadicke is a managing director of BV 2014 LLC and BV 2018 LLC. ( 2 )MPM BioImpact LLC ("BioImpact") is the General Partner of Oncology Impact Fund (Cayman) Management L.P., the General Partner of UBS Oncology Impact Fund, L.P. Ansbert Gadicke is a managing partner of BioImpact. Each of the Reporting Persons disclaims beneficial ownership of the securities herein except to the extent of his or its respective pecuniary interest therein, if any. ( 3 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.73 to $8.34 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. ( 4 )The shares are held as follows: 1,189,174 by BV 2014, 74,903 by BV 2014(B), 40,931 by AM BV2014, 751,056 by BV 2018, 37,699 by BV 2018(B), 14,831 by AM BV2018 and 1,344,203 by UBS Oncology. Each of the Reporting Persons disclaims beneficial ownership of the securities herein except to the extent of his or its respective pecuniary interest therein, if any.

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.