X0306 4 2021-04-15 1 0001708493 Harpoon Therapeutics, Inc. HARP 0001609492 MPM BioVentures 2014, L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001263048 MPM ASSET MANAGEMENT LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001609493 MPM BioVentures 2014 (B), L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001609495 MPM Asset Management Investors BV2014 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001765021 MPM BioVentures 2014 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001765091 MPM BioVentures 2014 GP LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001473930 Foley Todd C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner 0001134657 EVNIN LUKE C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE MA 02142 0 0 0 1 Former 10% Owner Common Stock 2021-04-13 4 S 0 1657 19.35 D 3223853 I See Footnote Common Stock 2021-04-13 4 S 0 286 20.08 D 3223567 I See Footnote Common Stock 2021-04-14 4 S 0 121 20.06 D 3223446 I See Footnote Common Stock 2021-04-14 4 S 0 1550 20.83 D 3221896 I See Footnote Common Stock 2021-04-15 4 S 0 1052 20.49 D 3220844 I See Footnote Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 on 3/16/2021. The shares were sold by MPM Asset Management LLC ("AM LLC"). The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.98 to $19.88 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 as follows: 2,657,097 by MPM BioVentures 2014, L.P. ("BV 2014"), 152,470 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 96,376 by MPM Asset Management Investors BV2014 LLC ("AM BV2014") and 317,910 by AM LLC. MPM BioVentures 2014 GP LLC and MPM BioVentures 2014 LLC ("BV LLC") are the direct and indirect general partners of BV 2014 and BV 2014(B). BV LLC is the manager of AM BV2014. Messrs. Evnin and Foley are the members of BV LLC and Mr. Evnin is a member of AM LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.89 to $20.50 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 as follows: 2,657,097 by BV 2014, 152,470 by BV 2014(B), 96,376 by AM BV2014 and 317,624 by AM LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.44 to $20.39 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 as follows: 2,657,097 by BV 2014, 152,470 by BV 2014(B), 96,376 by AM BV2014 and 317,503 by AM LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $20.52 to $21.18 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 as follows: 2,657,097 by BV 2014, 152,470 by BV 2014(B), 96,376 by AM BV2014 and 315,953 by AM LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $20.15 to $20.99 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 as follows: 2,657,097 by BV 2014, 152,470 by BV 2014(B), 96,376 by AM BV2014 and 314,901 by AM LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC, the general partner of MPM BioVentures 2014, L.P. 2021-04-15 /s/ Ansbert Gadicke, Member of MPM Asset Management LLC 2021-04-15 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC, the general partner of MPM BioVentures 2014 (B), L.P. 2021-04-15 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the manager of MPM Asset Management Investors BV2014 LLC 2021-04-15 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC 2021-04-15 /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC 2021-04-15 /s/ Todd Foley 2021-04-15 /s/ Luke Evnin 2021-04-15