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 OF SECURITIES
                                                                                  
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      
1. Name and Address of Reporting Person * MPM BIOVENTURES 2018, L.P. 2. Issuer Name and Ticker or Trading Symbol iTeos Therapeutics, Inc. [ ITOS ] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable)_____ Director                    __X__ 10% Owner
_____ Officer (give title below)    _____ Other (specify below)
(Last)         (First)         (Middle)
C/O MPM CAPITAL, 450 KENDALL STREET
3. Date of Earliest Transaction (MM/DD/YYYY)
9/16/2021
(Street)
CAMBRIDGE, MA 02142
(City)       (State)       (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)
 
6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person
_ X _ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. 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  9/16/2021    S(1)    21253 (2) D $28.47 (3) 3467323  I  See Footnote (4)
Common Stock  9/17/2021    S(1)    45698 (5) D $28.82 (6) 3421625  I  See Footnote (7)
Common Stock  9/20/2021    S(1)    10602 (8) D $27.03 (9) 3411023  I  See Footnote (10)
Common Stock  9/20/2021    S(1)    13701 (11) D $27.84 (12) 3397322  I  See Footnote (13)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Trans. Date 3A. Deemed Execution Date, if any 4. Trans. 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 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 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

Explanation of Responses:
(1)  Transaction effected pursuant to a plan established pursuant to Rule 10b5-1.
(2)  The shares were sold as follows: 12,662 by MPM BioVentures 2014, L.P. ("BV 2014"), 436 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 7,997 by MPM BioVentures 2018, L.P. ("BV 2018") and 158 by MPM Asset Management Investors BV2018 LLC ("AM BV2018"). 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. Messrs. Evnin and Foley are managing directors of BV 2014 LLC and BV 2018 LLC.
(3)  The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $27.885 to $28.69 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: 1,969,301 by BV 2014, 107,713 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 67,782 by AM BV2014, 1,243,769 by BV 2018, 54,213 by MPM BioVentures 2018(B), L.P. ("BV 2018(B)") and 24,545 by AM BV2018. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein.
(5)  The shares were sold as follows: 27,226 by BV 2014, 937 by AM BV2014, 17,195 by BV 2018 and 340 by AM BV2018.
(6)  The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.50 to $29.11 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.
(7)  The shares are held as follows: 1,942,075 by BV 2014, 107,713 by BV 2014(B), 66,845 by AM BV2014, 1,226 574 by BV 2018, 54,213 by BV 2018(B) and 24,205 by AM BV2018. 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.
(8)  The shares were sold as follows: 6,317 by BV 2014, 217 by AM BV2014, 3,990 by BV 2018 and 78 by AM BV2018.
(9)  The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $26.535 to $27.52 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.
(10)  The shares are held as follows: 1,935,758 by BV 2014, 107,713 by BV 2014(B), 66,628 by AM BV2014, 1,222,584 by BV 2018, 54,213 by BV 2018(B) and 24,127 by AM BV2018. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein.
(11)  The shares were sold as follows: 8,163 by BV 2014, 281 by AM BV2014, 5,156 by BV 2018 and 101 by AM BV2018.
(12)  The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $27.53 to $28.39 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.
(13)  The shares are held as follows: 1,927,595 by BV 2014, 107,713 by BV 2014(B), 66,347 by AM BV2014, 1,217,428 by BV 2018, 54,213 by BV 2018(B) and 24,026 by AM BV2018. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein.

Remarks:
See Form 4 for MPM BioVentures 2014, L.P for additional members of this joint filing.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director 10% Owner Officer Other
MPM BIOVENTURES 2018, L.P.
C/O MPM CAPITAL
450 KENDALL STREET
CAMBRIDGE, MA 02142

X

MPM BioVentures 2018 LLC
C/O MPM CAPITAL
450 KENDALL STREET
CAMBRIDGE, MA 02142

X

MPM BioVentures 2018 GP LLC
C/O MPM CAPITAL
450 KENDALL STREET
CAMBRIDGE, MA 02142

X


Signatures
/s/ Ansbert Gadicke, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC, the general partner of MPM BioVentures 2018, L.P. 9/20/2021
**Signature of Reporting Person Date
/s/ Ansbert Gadicke, managing director of MPM BioVentures 2018 LLC 9/20/2021
**Signature of Reporting Person Date
/s/ Ansbert Gadicke, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC 9/20/2021
**Signature of Reporting Person Date
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