X0306 4 2021-12-20 0 0001808865 iTeos Therapeutics, Inc. ITOS 0001457477 Hallal David C/O ITEOS THERAPEUTICS, INC. 139 MAIN ST. CAMBRIDGE MA 02142 1 0 0 0 Common Stock 2021-12-20 4 M 0 20000 4.30 A 20000 D Common Stock 2021-12-20 4 M 0 30000 2.95 A 50000 D Common Stock 2021-12-20 4 S 0 50000 43.57 D 0 D Stock Option (Right to Buy) 4.30 2021-12-20 4 M 0 20000 0.00 D 2025-06-11 Common Stock 20000 114682 D Stock Option (Right to Buy) 2.95 2021-12-20 4 M 0 30000 0.00 D 2029-12-04 Common Stock 30000 37039 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $43.25 to $44.19, 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 July 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. One-fourth of the shares subject to the stock option vested on December 5, 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 2021-12-22