X0306 4 2021-07-07 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 Common Stock 2021-07-07 4 M 0 25000 1.03 A 1046525 D Common Stock 2021-07-07 4 S 0 645 100.69 D 1045880 D Common Stock 2021-07-07 4 S 0 2300 101.27 D 1043580 D Common Stock 2021-07-07 4 S 0 100 102.00 D 1043480 D Common Stock 2021-07-07 4 S 0 2864 103.52 D 1040616 D Common Stock 2021-07-07 4 S 0 1336 104.40 D 1039280 D Common Stock 2021-07-07 4 S 0 1800 105.44 D 1037480 D Common Stock 2021-07-07 4 S 0 500 106.48 D 1036980 D Common Stock 2021-07-07 4 S 0 167 107.31 D 1036813 D Common Stock 2021-07-07 4 S 0 800 108.65 D 1036013 D Common Stock 2021-07-07 4 S 0 4800 109.58 D 1031213 D Common Stock 2021-07-07 4 S 0 3982 110.54 D 1027231 D Common Stock 2021-07-07 4 S 0 3456 111.51 D 1023775 D Common Stock 2021-07-07 4 S 0 2250 112.62 D 1021525 D Common Stock 223000 I By John M. Evans, III 2018 Irrevocable Trust Stock Option (Right to Buy 1.03 2021-07-07 4 M 0 25000 0.00 D 2028-07-13 Common Stock 25000 371345 D The stock option exercise reported in this Form 4 was effected pursuant to a 10b5-1 trading plan. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. The sale price reported is a weighted average price. The Reporting Person undertakes to provide to Beam Therapeutics Inc. ("BEAM"), any security holder of BEAM 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 range. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $100.25 to $100.99, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $101.00 to $101.85, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $103.21 to $103.96, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $104.00 to $104.96, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $105.02 to $105.98, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $106.12 to $106.77, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $107.29 to $107.33, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $108.32 to $108.99, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $109.01 to $109.98, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $110.04 to $110.99, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $111.04 to $111.99, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $112.00 to $112.99, inclusive. The option vests as to 25% on the first anniversary of the of the vesting commencement date, January 8, 2018, and at a rate of 2.78% each month thereafter until the option is fully vested. /s/ Christine Bellon, Attorney-in-fact 2021-07-08