X0306 4 2021-08-02 0 0001661460 Poseida Therapeutics, Inc. PSTX 0001765987 Ostertag Eric C/O POSEIDA THERAPEUTICS, INC. 9390 TOWNE CENTRE DRIVE, STE 200 SAN DIEGO CA 92121 1 1 1 0 Chief Executive Officer Common Stock 2021-08-02 4 S 0 7167 8.13 D 3748876 I See footnote Common Stock 2021-08-03 4 S 0 10401 7.99 D 3738475 I See footnote Common Stock 2021-08-02 4 S 0 6570 8.13 D 3440382 I See footnote Common Stock 2021-08-03 4 S 0 9535 7.99 D 3430847 I See footnote Common Stock 542985 D Common Stock 629194 I See footnote Common Stock 961445 I See footnote Common Stock 200696 I See footnote The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 23, 2020. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $8.03 to $8.28 per share, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held in the name of the Eric Ostertag Living Trust dated March 30, 2016, of which the reporting person is the sole trustee. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.85 to $8.12 per share, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held in the name of Titan, LLC, which is owned by the Ostertag Descendents' Trust, of which the reporting person's minor daughter is the sole beneficiary. The reporting person disclaims beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of the securities for purposes of Section 16 or for any other purpose. The shares are held in the name of Twin Prime Investments, an entity wholly owned by the reporting person. The shares are held in the name of the Ostertag Family Trust dated March 30, 2016, of which the reporting person is a trustee. The shares are held in the name of Transposagen Biopharmaceuticals, Inc., of which Dr. Ostertag is a majority stockholder. /s/ Harry J. Leonhardt, Attorney-in-Fact 2021-08-04