X0306 4 2020-03-27 0 0001426800 ASSEMBLY BIOSCIENCES, INC. ASMB 0001663018 Colonno Richard James C/O ASSEMBLY BIOSCIENCES, INC. 331 OYSTER POINT BLVD., FOURTH FLOOR SOUTH SAN FRANCISCO CA 94080 0 1 0 0 EVP & CSO, Virology Ops Common Stock 2020-03-27 4 A 0 17000 0.00 A 144821 D Common Stock 2020-03-31 4 S 0 7812 15.044 D 137009 D Stock Option (right to buy) 14.45 2020-03-27 4 A 0 34000 0.00 A 2030-03-27 Common Stock 34000 34000 D Grant of restricted stock units. The restricted stock units vest in four equal installments, assuming continuous service on each vesting date, as follows: March 29, 2021; March 29, 2022; March 29, 2023; and March 29, 2024. The sale reported on this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.77 to $15.55, inclusive. The reporting person undertakes to provide 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. Grant of stock options. The stock options vest over four years, assuming continuous service on each vesting date, as follows: 25% vest on March 29, 2021; and the remaining 75% vest in 36 approximately equal monthly installments, with the options becoming fully vested on March 29, 2024. /s/ John O. Gunderson, as Attorney-in-Fact 2020-03-31