X0306 4/A 2021-05-04 2021-05-07 0 0001708493 Harpoon Therapeutics, Inc. HARP 0001590157 Robbins Andrew R C/O HARPOON THERAPEUTICS, INC. 131 OYSTER POINT BOULEVARD, SUITE 300 SOUTH SAN FRANCISCO CA 94080 1 0 0 0 Director Stock Option (Right to Buy) 23.20 2021-05-04 4 A 0 10167 0.00 A 2031-05-03 Common Stock 10167 10167 D This option was erroneously reported with a price of $22.50 on the original Form 4 filed on May 7, 2021 due to an administrative error. The stock option will fully vest and become exercisable on May 3, 2022, subject to the continuous service of the Reporting Person with the Issuer on such date. The original Form 4 filed on May 7, 2021 erroneously reported this vesting date as May 4, 2022. /s/ Andrew R. Robbins by Christopher Whitmore, Attorney-in-Fact 2021-05-14