X0306 4 2022-01-14 0 0001808865 iTeos Therapeutics, Inc. ITOS 0001816215 Lager Joanne Jenkins 139 MAIN STREET CAMBRIDGE MA 02142 0 1 0 0 Chief Medical Officer Common Stock 2022-01-14 4 M 0 3500 4.30 A 3500 D Common Stock 2022-01-14 4 S 0 2777 39.25 D 723 D Common Stock 2022-01-14 4 S 0 723 39.58 D 0 D Stock Option (Right to Buy) 4.30 2022-01-14 4 M 0 3500 0.00 D 2025-06-11 Common Stock 3500 185938 D The transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 23, 2021. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $38.47 to $39.46, 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $39.48 to $39.68, 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. One-fourth of the shares subject to the stock option vested on April 1, 2020. 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 /s/ Adi Osovsky, as Attorney-in-Fact 2022-01-18