X0306 4 2020-06-22 0 0001785173 89bio, Inc. ETNB 0001792061 DiRocco Derek C/O 89BIO, INC. 142 SANSOME STREET, 2ND FLOOR SAN FRANCISCO CA 94104 1 0 0 0 Stock Option (Right to Buy) 24.29 2020-06-22 4 A 0 7000 0.00 A 2030-06-22 Common Stock 7000 7000 I See footnote This option represents a right to purchase a total of 7,000 shares of the Issuer's Common Stock, which will vest in full on June 22, 2021, subject to the Reporting Person's continued service to the Issuer through such date. Under the Reporting Person's arrangement with RA Capital Management, L.P. (the "Adviser"), the Reporting Person holds the option for the benefit of the RA Capital Healthcare Fund, L.P. (the "Fund"), RA Capital Nexus Fund, L.P. (the "Nexus Fund") and a separately managed account (the "Account"). The Reporting Person is obligated to turn over to the Adviser any net cash or stock received from the option, which will offset advisory fees owed by the Fund, the Nexus Fund and the Account to the Adviser. The Reporting Person therefore disclaims beneficial ownership of the option and underlying common stock. /s/ Ryan A. Murr, as attorney-in-fact for Derek DiRocco 2020-07-14