X0306 4 2021-07-06 0 0001745999 Beam Therapeutics Inc. BEAM 0001396943 COOPER GRAHAM K C/O BEAM THERAPEUTICS INC., 26 LANDSDOWNE STREET CAMBRIDGE MA 02139 1 0 0 0 Common Stock 2021-07-06 4 M 0 2614 17.00 A 2614 D Common Stock 2021-07-06 4 S 0 614 115.38 D 2000 D Common Stock 2021-07-06 4 S 0 200 116.41 D 1800 D Common Stock 2021-07-06 4 S 0 200 118.35 D 1600 D Common Stock 2021-07-06 4 S 0 100 119.68 D 1500 D Common Stock 2021-07-06 4 S 0 200 120.39 D 1300 D Common Stock 2021-07-06 4 S 0 400 121.59 D 900 D Common Stock 2021-07-06 4 S 0 100 122.85 D 800 D Common Stock 2021-07-06 4 S 0 200 123.76 D 600 D Common Stock 2021-07-06 4 S 0 300 124.31 D 300 D Common Stock 2021-07-06 4 S 0 100 126.51 D 200 D Common Stock 2021-07-06 4 S 0 100 128.67 D 100 D Common Stock 2021-07-06 4 S 0 100 129.38 D 0 D Stock Option (Right to Buy) 17.00 2021-07-06 4 M 0 2614 0.00 D 2030-02-05 Common Stock 2614 16561 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 at prices ranging from $115.04 to $115.88, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $116.13 to $116.69, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $118.00 to $118.71, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $119.67 to $119.68, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $120.37 to $120.40, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $121.19 to $121.96, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $123.64 to $123.88, inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $124.28 to $124.33, inclusive. The option vests as to one third on the first anniversary of the of the vesting commencement date, February 5, 2020, and at a rate of 4.17% each month thereafter until the option is fully vested. By: /s/ Christine Bellon, Attorney-in-fact 2021-07-08