Sec Form 4 Filing - Detheux Michel @ iTeos Therapeutics, Inc. - 2021-12-02

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

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1. Name and Address of Reporting Person Detheux Michel 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 X __ Officer (give title below) _____ Other (specify below) Chief Executive Officer (Last) (First) (Middle) 139 MAIN STREET 3. Date of Earliest Transaction (MM/DD/YY) 12/02/2021 (Street) CAMBRIDGE, MA02142 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 12/20/2021 M( 1 ) 9,111 A $ 4.3 87,311 D Common Stock 12/20/2021 S( 1 ) 9,111 D $ 43.94( 2 ) 78,200 D Common Stock 12/21/2021 M( 1 ) 19,226 A $ 4.3 97,426 D Common Stock 12/21/2021 S( 1 ) 13,646 D $ 44.15( 3 ) 83,780 D Common Stock 12/21/2021 S( 1 ) 5,580 D $ 45.06( 4 ) 78,200 D Common Stock 12/22/2021 M( 1 ) 1,663 A $ 4.3 79,863 D Common Stock 12/22/2021 S( 1 ) 1,514 D $ 44.31( 5 ) 78,349 D Common Stock 12/22/2021 S( 1 ) 149 D $ 44.92 78,200 D Common Stock 12/22/2021 S( 1 ) 5,007 D $ 44.62( 6 ) 73,193 D Common Stock 12/22/2021 S( 1 ) 9,493 D $ 45.37( 7 ) 63,700 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 (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 Stock Option (Right to Buy) $ 4.3 12/02/2021 G( 8 ) V 313,442 ( 9 ) 06/11/2025 Common Stock 403,442 $ 0 90,000 D Stock Option (Right to Buy) $ 4.3 12/02/2021 G( 8 ) V 313,442 ( 9 ) 06/11/2025 Common Stock 313,442 $ 0 313,442 I By MG3A( 8 ) Stock Option (Right to Buy) $ 4.23 12/02/2021 G( 8 ) V 185,000 ( 10 ) 05/01/2030 Common Stock 340,964 $ 0 155,964 D Stock Option (Right to Buy) $ 4.23 12/02/2021 G( 8 ) V 185,000 ( 10 ) 05/01/2030 Common Stock 185,000 $ 0 185,000 I By MG3A( 8 ) Stock Option (Right to Buy) $ 6.15 12/02/2021 G( 8 ) V 52,700 ( 11 ) 06/18/2030 Common Stock 70,244 $ 0 17,544 D Stock Option (Right to Buy) $ 6.15 12/02/2021 G( 8 ) V 52,700 ( 11 ) 06/18/2030 Common Stock 52,700 $ 0 52,700 I By MG3A( 8 ) Stock Option (Right to Buy) $ 19 12/02/2021 G( 8 ) V 776,600 ( 12 ) 07/23/2030 Common Stock 1,035,424 $ 0 258,824 D Stock Option (Right to Buy) $ 19 12/02/2021 G( 8 ) V 776,600 ( 12 ) 07/23/2030 Common Stock 776,600 $ 0 776,600 I By MG3A( 8 ) Stock Option (Right to Buy) $ 41.58 12/02/2021 G( 8 ) V 106,200 ( 13 ) 03/01/2031 Common Stock 144,000 $ 0 37,800 D Stock Option (Right to Buy) $ 41.58 12/02/2021 G( 8 ) V 106,200 ( 13 ) 03/01/2031 Common Stock 106,200 $ 0 106,200 I By MG3A( 8 ) Stock Option (Right to Buy) $ 4.3 12/20/2021 M( 1 ) 9,111 ( 9 ) 06/11/2025 Common Stock 9,111 $ 0 80,889 D Stock Option (Right to Buy) $ 4.3 12/21/2021 M( 1 ) 19,226 ( 9 ) 06/11/2025 Common Stock 19,226 $ 0 61,663 D Stock Option (Right to Buy) $ 4.3 12/22/2021 M( 1 ) 1,663 ( 9 ) 06/11/2025 Common Stock 1,663 $ 0 60,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Detheux Michel 139 MAIN STREET CAMBRIDGE, MA02142 Chief Executive Officer Signatures /s/ Adi Osovsky, as Attorney-in-Fact 12/22/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 18, 2021. ( 2 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $43.8 to $44.2, inclusive. The reporting person undertakes to provide to iTeos Therapeutics, Inc., any security holder of iTeos Therapeutics, Inc., 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 ranges set forth in this footnote. ( 3 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $43.8 to $44.79, inclusive. The reporting person undertakes to provide to iTeos Therapeutics, Inc., any security holder of iTeos Therapeutics, Inc., 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 ranges set forth in this footnote. ( 4 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $44.825 to $45.29, inclusive. The reporting person undertakes to provide to iTeos Therapeutics, Inc., any security holder of iTeos Therapeutics, Inc., 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 ranges set forth in this footnote. ( 5 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $43.85 to $44.73, inclusive. The reporting person undertakes to provide to iTeos Therapeutics, Inc., any security holder of iTeos Therapeutics, Inc., 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 ranges set forth in this footnote. ( 6 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $44.12 to $45.11, inclusive. The reporting person undertakes to provide to iTeos Therapeutics, Inc., any security holder of iTeos Therapeutics, Inc., 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 ranges set forth in this footnote. ( 7 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $45.15 to $45.83, inclusive. The reporting person undertakes to provide to iTeos Therapeutics, Inc., any security holder of iTeos Therapeutics, Inc., 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 ranges set forth in this footnote. ( 8 )The reporting person transferred these stock options to MG3A, a Belgian partnership of which the reporting person is the manager and the reporting person's spouse is the successor manager. ( 9 )One-fourth of the shares subject to the stock option vested on January 1, 2019. Thereafter, 1/48 of the shares subject to the stock option vest on a monthly basis, subject to the reporting person's continuous service relationship with the Issuer through each applicable vesting date. ( 10 )One-fourth of the shares subject to the stock option vested on May 1, 2021. Thereafter, 1/48 of the shares subject to the stock option vest on a monthly basis, subject to the reporting person's continuous service relationship with the Issuer through each applicable vesting date. ( 11 )One-fourth of the shares subject to the stock option vested on June 1, 2021. Thereafter, 1/48 of the shares subject to the stock option vest on a monthly basis, subject to the reporting person's continuous service relationship with the Issuer through each applicable vesting date. ( 12 )One-fourth of the shares subject to the stock option vested on July 23, 2021. Thereafte r, 1/48 of the shares subject to the stock option vest on a monthly basis, subject to the reporting person's continuous service relationship with the Issuer through each applicable vesting date. ( 13 )One-fourth of the shares subject to the stock option will vest on March 1, 2022, subject to the reporting person's continuous service relationship with the Issuer. Thereafter, 1/48 of the shares subject to the stock option vest on a monthly basis, subject to the reporting person's continuous service relationship with the Issuer through each applicable vesting 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).

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