X0407 4 2023-06-08 0001835597 PepGen Inc. PEPG 0001763307 McArthur James G 321 HARRISON AVE., 8TH FLOOR C/O PEPGEN INC. BOSTON MA 02118 1 1 President and CEO 1 Common Stock 2023-06-08 4 M 0 2381 2.71 A 2381 D Common Stock 2023-06-08 4 S 0 2381 16.0386 D 0 D Stock Option (Right to Buy) 2.71 2023-06-08 4 M 0 2381 0 D 2031-03-21 Common Stock 2381 325054 D The transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 8, 2022. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $16.00 to $16.10, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, 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 set forth in this footnote. This stock option vests over four years following the vesting commencement date (January 21, 2021) with 25% of such shares vesting on the first anniversary of the vesting commencement date, and the remaining shares vesting in 36 equal monthly installments, subject to continued service through each vesting date. /s/ Noel Donnelly, as Attorney-in-Fact 2023-06-09