X0306 4/A 2019-12-16 2019-12-18 0 0001510487 Principia Biopharma Inc. PRNB 0001751790 Wolff Stefani C/O PRINCIPIA BIOPHARMA INC. 220 E. GRAND AVENUE SOUTH SAN FRANCISCO CA 94080 0 1 0 0 Chief Development Officer Common Stock 2019-12-16 4 S 0 4205 49.2903 D 31404 D Common Stock 2019-12-16 4 S 0 1300 49.8654 D 30104 D The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. Represents the weighted average sales price per share. The shares sold at prices ranging from $48.81 to $49.725 per share. Upon request by the Commission staff, Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. Includes 2,500 shares and 441 shares acquired under the Employment Stock Purchase Plan on May 15, 2019 and November 15, 2019 respectively. Due to administrative error, stock options were incorrectly reported as exercised on the original Form 4 filed on December 18, 2019, pursuant to a 10b5-1 transaction. That original Form 4 is hereby amended in its entirety. Represents the weighted average sales price per share. The shares sold at prices ranging from $49.855 to $49.87 per share. Upon request by the Commission staff, Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. /s/ Christopher Y. Chai, Attorney-in-Fact for Stefani Wolff 2020-06-17