X0306 4/A 2021-05-04 2021-05-07 0 0001708493 Harpoon Therapeutics, Inc. HARP 0001816744 Viney Joanne L. 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 Director Stock Option (Right to Buy) 23.20 2021-05-04 4 A 0 2571 0.00 A 2031-05-03 Common Stock 2571 2571 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. 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 related to the calculation date of the Black-Scholes value. The number of shares underlying the option was erroneously reported as 2,653 on the original Form 4 filed on May 7, 2021 due to an administrative error related to the calculation date of the Black-Scholes value. 50% of the shares subject to the option are fully vested and exercisable, and 25% will vest and become exercisable on September 30, 2021 and December 31, 2021, subject to the continuous service of the Reporting Person on each vesting date. /s/ Joanne L. Viney by Christopher Whitmore, Attorney-in-Fact 2021-05-14