X0306 4 2022-03-01 0 0001808865 iTeos Therapeutics, Inc. ITOS 0001816213 McGrath Yvonne 321 ARSENAL STREET WATERTOWN MA 02472 0 1 0 0 Chief Scientific Officer Common Stock 2022-03-01 4 M 0 10000 4.24 A 10000 D Common Stock 2022-03-01 4 S 0 10000 36.757 D 0 D Stock Option (Right to Buy) 4.24 2022-03-01 4 M 0 10000 0.00 D 2030-05-01 Common Stock 10000 85123 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $36.69 to $36.95, 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 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. /s/ Adi Osovsky, as Attorney-in-Fact 2022-03-02