X0306 4 2019-09-17 0 0001581280 Twist Bioscience Corp TWST 0001755793 Weiss Patrick C/O TWIST BIOSCIENCE CORPORATION 455 MISSION BAY BOULEVARD SOUTH SAN FRANCISCO CA 94158 0 1 0 0 SVP, R&D GM Data Storage Common Stock 2019-09-17 4 M 0 3682 5.95 A 108969 D Common Stock 2019-09-17 4 M 0 3682 8.82 A 112651 D Common Stock 2019-09-17 4 S 0 1641 29.545 D 111010 D Common Stock 2019-09-17 4 S 0 600 30.246 D 110410 D Common Stock 2019-09-17 4 S 0 3282 29.544 D 107128 D Common Stock 2019-09-17 4 S 0 1741 29.544 D 105387 D Common Stock 2019-09-17 4 S 0 100 30.282 D 105287 D Common Stock 2019-09-18 4 M 0 3682 5.95 A 108969 D Common Stock 2019-09-18 4 M 0 3682 8.82 A 112651 D Common Stock 2019-09-18 4 S 0 1841 29.963 D 110810 D Common Stock 2019-09-18 4 S 0 1641 29.852 D 109169 D Common Stock 2019-09-18 4 S 0 200 30.39 D 108969 D Common Stock 2019-09-18 4 S 0 1841 29.965 D 107128 D Common Stock 2019-09-18 4 S 0 1841 29.988 D 105287 D Employee Stock Option (right to buy) 5.95 2019-09-17 4 M 0 3682 0.00 D 2025-09-28 Common Stock 3682 31788 D Employee Stock Option (right to buy) 8.82 2019-09-17 4 M 0 3682 0.00 D 2027-09-28 Common Stock 3682 82888 D Employee Stock Option (right to buy) 5.95 2019-09-18 4 M 0 3682 0.00 D 2025-09-28 Common Stock 3682 28106 D Employee Stock Option (right to buy) 8.82 2019-09-18 4 M 0 3682 0.00 D 2027-09-28 Common Stock 3682 79206 D The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan previously adopted by the Reporting Person. Represents the aggregate of sales effected on the same day at different prices. Represents the weighted average sales price per share. The shares sold at prices ranging from $29.13 to $30.12 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $30.21 to $30.28 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $29.13 to $30.10 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $29.13 to $30.05 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $29.64 to $30.56 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $29.25 to $30.20 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $29.40 to $30.35 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. The option is immediately exercisable. 25% of the shares subject to the option vested on September 1, 2016, and 1/48th of the shares subject to the option vest on each monthly anniversary thereafter, subject to the Reporting Person's continuous service through each vesting date. The option is immediately exercisable. 10% of the shares subject to the option vested on September 29, 2017, 15% of the shares subject to the option vested on September 28, 2018, and 1/48th of the shares subject to the option vest on each monthly anniversary thereafter, subject to the Reporting Person's continuous service through each vesting date. /s/ William Solis, as Attorney-in-Fact for Patrick Weiss 2019-09-19