X0306 4 2021-04-12 0 0001826457 Monte Rosa Therapeutics, Inc. GLUE 0001778843 Wallace Owen B. MONTE ROSA THERAPEUTICS, INC. 645 SUMMER STREET, SUITE 102 BOSTON MA 02210 0 1 0 0 Chief Scientific Officer Stock Option (Right to Buy) 6.14 2021-04-12 4 A 0 387069 0.00 A 2031-04-12 Common Stock 387069 387069 D Stock Option (Right to Buy) 19.00 2021-06-23 4 A 0 113298 0.00 A 2031-06-22 Common Stock 113298 113298 D On June 17, 2021, the Issuer completed a one-for-3.5305 reverse stock split of the Issuer's Common Stock (the "Reverse Split"). This amount has been adjusted to give effect to the Reverse Split. This transaction occurred prior to the Issuer's initial public offering, and is being reported on Form 4 solely for purposes of compliance with Rule 16a-2(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). The securities covered by such transaction were previously included on the Reporting Person's Form 3. 25% of this option shall vest and become exercisable on February 8, 2022, with the remainder vesting in 36 substantially equal monthly installments thereafter. 25% of this option shall vest and become exercisable on May 28, 2022, with the remainder vesting in 36 substantially equal monthly installments thereafter. /s/ Ajim Tamboli, Attorney-in-Fact 2021-06-25