X0306 4/A 2020-03-16 2020-03-18 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 2020-03-16 4 S 0 1754 45.7196 D 28350 D Common Stock 2020-03-16 4 S 0 3750 46.3569 D 24600 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 $45.05 to $46.01 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. Due to administrative error, stock options were incorrectly reported as exercised on the original Form 4 filed on March 18, 2020, 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 $46.08 to $46.60 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