X0306 4 2021-11-30 0 0001808865 iTeos Therapeutics, Inc. ITOS 0001729505 MPM BIOVENTURES 2018, L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001818702 MPM BioVentures 2018 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 0001818701 MPM BioVentures 2018 GP LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 1 0 Common Stock 2021-11-30 4 S 0 5861 34.62 D 3012959 I See Footnote Common Stock 2021-11-30 4 S 0 28076 35.19 D 2984883 I See Footnote Common Stock 2021-12-01 4 S 0 6042 33.82 D 2978841 I See Footnote Common Stock 2021-12-01 4 S 0 5457 34.61 D 2973384 I See Footnote Common Stock 2021-12-01 4 S 0 896 35.34 D 2972488 I See Footnote Common Stock 2021-12-02 4 S 0 29757 33.74 D 2942731 I See Footnote Common Stock 2021-12-02 4 S 0 7430 34.83 D 2935301 I See Fpotnote Transaction effected pursuant to a plan established pursuant to Rule 10b5-1. The shares were sold as follows: 3,494 by MPM BioVentures 2014, L.P. ("BV 2014"), 120 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 2,206 by MPM BioVentures 2018, L.P. ("BV 2018") and 41 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.93 to $34.92 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. The shares are held as follows: 1,707,933 by BV 2014, 97,289 by, 58,786 by AM BV2014, 1,078,695 by BV 2018, 48,966 by BV 2018(B) and 21,290 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. The shares were sold as follows: 16,733 by BV 2014, 576 by AM BV2014, 10,569 by BV 2018 and 198 by AM BV2018. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $34.93 to $35.465 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. The shares are held as follows: 1,691,200 by BV 2014, 97,289 by BV 2014(B), 58,210 by AM BV2014, 1,068,126 by BV 2018, 48,966 by BV 2018(B) and 21,092 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. The shares were sold as follows: 3,600 by BV 2014, 124 by AM BV2014, 2,274 by BV 2018 and 44 by AM BV2018. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.26 to $34.22 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. The shares are held as follows: 1,687,600 by BV 2014, 97,289 by BV 2014(B), 58,086 by AM BV2014, 1,065,852 by BV 2018, 48,966 by BV 2018(B) and 21,048 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. The shares were sold as follows: 3,251 by BV 2014, 112 by AM BV2014, 2,053 by BV 2018 and 41 by AM BV2018. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $34.30 to $35.17 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. The shares are held as follows: 1,684,349 by BV 2014, 97,289 by BV 2014(B), 57,974 by AM BV2014, 1,063,799 by BV 2018, 48,966 by BV 2018(B) and 21,007 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. The shares were sold as follows: 534 by BV 2014, 18 by AM BV2014, 337 by BV 2018 and 7 by AM BV2018. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $35.30 to $35.77 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. The shares are held as follows: 1,683,815 by BV 2014, 97,289 by BV 2014(B), 57,956 by AM BV2014, 1,063,462 by BV 2018, 48,966 by BV 2018(B) and 21,000 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. The shares were sold as follows: 17,728 by BV 2014, 611 by AM BV2014, 11,197 by BV 2018 and 221 by AM BV2018. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.19 to $34.17 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. The shares are held as follows: 1,666,087 by BV 2014, 97,289 by BV 2014(B), 57,345 by AM BV2014, 1,052,265 by BV 2018, 48,966 by BV 2018(B) and 20,779 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. The shares were sold as follows: 4,427 by BV 2014, 152 by AM BV2014, 2,796 by BV 2018 and 55 by AM BV2018. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $34.25 to $35.14 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. The shares are held as follows: 1,661,660 by BV 2014, 97,289 by BV 2014(B), 57,193 by AM BV2014, 1,049,469 by BV 2018, 48,966 by BV 2018(B) and 20,724 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. See Form 4 for MPM BioVentures 2014, L.P for additional members of this joint filing. /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. 2021-12-02 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2018 LLC 2021-12-02 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC 2021-12-02