Sec Form 4 Filing - MPM BioVentures 2014, L.P. @ Harpoon Therapeutics, Inc. - 2019-02-12

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person MPM BioVentures 2014, L.P. 2. Issuer Name and Ticker or Trading Symbol Harpoon Therapeutics, Inc. [ HARP] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MPM CAPITAL, 450 KENDALL STREET 3. Date of Earliest Transaction (MM/DD/YY) 02/12/2019 (Street) CAMBRIDGE, MA02142 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 02/12/2019 C 1,525,164 A 1,847,227 I See Footnote ( 2 ) ( 3 ) Common Stock 02/12/2019 C 1,578,751 A 3,425,978 I See Footnote ( 3 ) ( 4 ) Common Stock 02/12/2019 C 417,852 A 3,843,830 I See Footnote ( 3 ) ( 5 ) Common Stock 02/12/2019 X( 6 ) 432,119 A $ 0.0492 4,275,949 I See Footnote ( 3 ) ( 7 ) Common Stock 02/12/2019 S( 6 ) 1,524 D $ 14 4,274,425 I See Footnote ( 3 ) ( 8 ) Common Stock 02/12/2019 P 250,000 A $ 14 4,524,425 I See Footnote ( 3 ) ( 9 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A Preferred Stock ( 1 ) 02/12/2019 C 1,525,164 ( 1 ) ( 1 ) Common Stock 1,525,164 $ 0 0 I See Footnote ( 10 ) Series B Preferred Stock ( 1 ) 02/12/2019 C 1,578,751 ( 1 ) ( 1 ) Common Stock 1,578,751 $ 0 0 I See Footnote ( 10 ) Series C Preferred Stock ( 1 ) 02/12/2019 C 417,852 ( 1 ) ( 1 ) Common Stock 417,852 $ 0 0 I See Footnote ( 10 ) Common Stock Warrant (Right to Buy) $ 0.0492 02/12/2019 X( 6 ) 25,418 03/24/2015 03/24/2025 Common Stock 25,418 $ 0 0 I See Footnote ( 10 ) Common Stock Warrant (Right to Buy) $ 0.0492 02/12/2019 X( 6 ) 57,192 07/23/2015 07/23/2025 Common Stock 57,192 $ 0 0 I See Footnote ( 10 ) Common Stock Warrant (Right to Buy) $ 0.0492 02/12/2019 X( 6 ) 171,579 08/19/2015 08/19/2025 Common Stock 171,579 $ 0 0 I See Footnote ( 10 ) Common Stock Warrant (Right to Buy) $ 0.0492 02/12/2019 X( 6 ) 50,837 12/16/2015 12/16/2025 Common Stock 50,837 $ 0 0 I See Footnote ( 10 ) Common Stock Warrant (Right to Buy) $ 0.0492 02/12/2019 X( 6 ) 76,256 11/01/2016 11/01/2026 Common Stock 76,256 $ 0 0 I See Footnote ( 10 ) Common Stock Warrant (Right to Buy) $ 0.0492 02/12/2019 X( 6 ) 50,837 01/10/2017 01/10/2027 Common Stock 50,837 $ 0 0 I See Footnote ( 10 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MPM BioVentures 2014, L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM ASSET MANAGEMENT LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM BioVentures 2014 (B), L.P. C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM Asset Management Investors BV2014 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM BioVentures 2014 LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM BioVentures 2014 GP LLC C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X Foley Todd C/O MPM CAPITAL 450 KENDALL STREET CAMBRIDGE, MA02142 X Signatures /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. 02/14/2019 Signature of Reporting Person Date /s/ Ansbert Gadicke, managing member of MPM Asset Management 02/14/2019 Signature of Reporting Person Date /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. 02/14/2019 Signature of Reporting Person Date /s/ Howard Rubin, director of MPM Asset Management Investors BV2014 LLC 02/14/2019 Signature of Reporting Person Date /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC 02/14/2019 Signature of Reporting Person Date /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC 02/14/2019 Signature of Reporting Person Date /s/ Todd Foley 02/14/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )All series of convertible preferred stock automatically converted into the number of shares of the Issuer's common stock on a 1-for-1 basis, for no additional consideration, immediately prior to the closing of the Issuer's initial public offering and had no expiration date. ( 2 )The shares are held as follows: 1,382,777 by MPM BioVentures 2014, L.P. ("BV 2014"), 92,229 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 50,158 by MPM Asset Management Investors BV2014 LLC ("AM BV2014") and 322,063 by MPM Asset Management LLC ("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). Luke Evnin, Ansbert Gadicke and Todd Foley are the members of BV LLC and Luke Evnin and Anbert Gadicke are the members of AM LLC. ( 3 )Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. ( 4 )The shares are held as follows: 2,814,142 by BV 2014, 187,696 by BV 2014(B), 102,077 by AM BV2014 and 322,063 by MPM LLC. ( 5 )The shares are held as follows: 3,192,985 by BV 2014, 212,964 by BV 2014(B), 115,818 by AM BV2014 and 322,063 by MPM LLC. ( 6 )On February 12, 2019, BV 2014, BV 2014(B) and AM BV2014 exercised warrants to purchase an aggregate of 432,119 shares of the Issuer's common stock for $0.0492 per share. The warrants were exercised as follows: 391,784 by BV 2014, 26,129 by BV 2014(B) and 14,206 by AM BV2014. The exercise price was paid on a cashless basis, resulting in the Issuer's withholding of an aggregate of 1,524 of the warrant shares to pay the exercise price and issuing to the respective Reporting Persons the remaining 430,595 shares. ( 7 )The shares are held as follows: 3,584,769 by BV 2014, 239,093 by BV 2014(B), 130,024 by AM BV2014 and 322,063 by MPM LLC. ( 8 )The shares are held as follows: 3,583,391 by BV 2014, 238,998 by BV 2014(B), 129,973 by AM BV2014 and 322,063 by MPM LLC. ( 9 )The shares are held as follows: 3,810,051 by BV 2014, 254,116 by BV 2014(B), 138,195 by AM BV2014 and 322,063 by MPM LLC. ( 10 )No securities held by the Reporting Persons.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.