X0306 4 2023-03-01 0 0001785173 89bio, Inc. ETNB 0001914164 Atkinson Edward Morrow III C/O 89BIO, INC. 142 SANSOME STREET, 2ND FLOOR SAN FRANCISCO CA 94104 1 0 0 0 Common Stock 2023-03-01 4 M 0 10000 4.44 A 10000 D Common Stock 2023-03-01 4 S 0 10000 13.60 D 0 D Stock Option (Right to Buy) 4.44 2023-03-01 4 M 0 10000 0.00 D 2032-02-16 Common Stock 10000 20000 D This transaction was executed pursuant to a Rule 10b5-1 trading plan in multiple trades at prices ranging from $13.49 to $14.83. The price reported above reflects the weighted average sales price. The reporting person hereby undertakes to provide upon request to the SEC staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transaction was effected. This option represents a right to purchase a total of 30,000 shares of the Issuer's Common Stock, which vests in equal installments on February 17, 2023, February 17, 2024 and February 17, 2025, subject to the Reporting Person's continued service to the Issuer through each vesting date. /s/ Ryan A. Murr, as attorney-in-fact for Edward Morrow Atkinson III 2023-03-03