X0306 4 2021-12-20 0 0001745999 Beam Therapeutics Inc. BEAM 0001786322 Ciaramella Giuseppe C/O BEAM THERAPEUTICS INC., 26 LANDSDOWNE STREET CAMBRIDGE MA 02139 0 1 0 0 President & CSO Common Stock 2021-12-20 4 M 0 4289 7.22 A 67062 D Common Stock 2021-12-20 4 S 0 4289 85.20 D 62773 D Common Stock 2021-12-21 4 M 0 25104 7.22 A 87877 D Common Stock 2021-12-21 4 S 0 16456 85.38 D 71421 D Common Stock 2021-12-21 4 S 0 8648 86.29 D 62773 D Stock Option (Right to Buy) 7.22 2021-12-20 4 M 0 4289 0.00 D 2029-05-17 Common Stock 4289 117357 D Stock Option (Right to Buy) 7.22 2021-12-21 4 M 0 25104 0.00 D 2029-05-17 Common Stock 25104 92253 D The stock option exercises reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. Each sale price reported is a weighted average price. The Reporting Person undertakes to provide 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. The shares were sold in multiple transactions at prices ranging from $85.00 to $85.69, inclusive. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $85.00 to $85.99, inclusive. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $86.00 to $86.74, inclusive. The option vests as to 25% on the first anniversary of the of the vesting commencement date, October 1, 2019, and at a rate of 2.78% each month thereafter until the option is fully vested. By: /s/ Christine Bellon, Attorney-in-fact 2021-12-22