X0306 4/A 2020-02-05 2020-08-17 0 0001745999 Beam Therapeutics Inc. BEAM 0001786304 Evans John M. C/O BEAM THERAPEUTICS INC. 26 LANDSDOWNE STREET CAMBRIDGE MA 02139 1 1 0 0 CEO Stock Option (Right to Buy) 0.67 2020-02-05 4 A 0 99336 0.00 A 2028-05-08 Common Stock 99336 99336 D Stock Option (Right to Buy) 4.22 2020-02-05 4 A 0 53964 0.00 A 2029-02-13 Common Stock 53964 53964 D On August 17, 2020, the reporting person filed a Form 4 which inadvertently omitted certain options held by the reporting person on such date (the "Original Form 4"). On May 8, 2018, the reporting person was granted an option to purchase 198,672 shares of common stock of Beam Therapeutics Inc. (the "Company"). The option award vests (i) fifty percent (50%) upon the Company achieving a certain development milestone related to base editing applications, and (ii) fifty percent (50%) upon the achievement of a closing price hurdle following the Company's initial public offering ("IPO") (which closing price hurdle has been achieved) (the "Price Condition"). The portion of the award subject to satisfaction of the Price Condition is scheduled to vest in three equal installments on December 21, 2021, June 30, 2022 and December 31, 2022. Upon the closing of the IPO, vesting of the portion of the option award subject to condition (ii) was tied only to the passage of time and the market price of the Company's securities and thus, 50% of the option award became reportable. (Continued from Footnote 2) The Original Form 4 failed to report the portion of the option award that became reportable upon the closing of the Company's IPO. On February 13, 2019, the reporting person was granted an option to purchase 107,929 shares of common stock of the Company. The option award vests (i) fifty percent (50%) upon the Company achieving a certain development milestone related to base editing applications, and (ii) fifty percent (50%) upon the achievement of a closing price hurdle following the Company's IPO (which closing price hurdle has been achieved). The portion of the award subject to satisfaction of the Price Condition is scheduled to vest in three equal installments on December 21, 2021, June 30, 2022 and December 31, 2022. Upon the closing of the IPO, vesting of the portion of the option award subject to condition (ii) was tied only to the passage of time and the market price of the Company's securities and thus, 50% of the option award became reportable. The Original Form 4 failed to report the portion of the option award that became reportable upon the closing of the Company's IPO. By: /s/ Christine Bellon, Attorney-in-fact 2021-09-21