Sec Form 3 Filing - MPM BioVentures 2014, L.P. @ Oncorus, Inc. - 2020-10-01

FORM 3 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

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1. Name and Address of Reporting Person MPM BioVentures 2014, L.P. 2. Issuer Name and Ticker or Trading Symbol Oncorus, Inc. [ ONCR] 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 ASSET MANAGEMENT LLC, 450 KENDALL STREET 3. Date of Earliest Transaction (MM/DD/YY) 10/01/2020 (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 115,823 I See footnote ( 1 ) ( 2 )

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-1 Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 1,783,879 I See footnote ( 2 ) ( 4 ) Series B Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 775,975 I See footnote ( 2 ) ( 5 ) Warrant (right to buy) $ 1.21 ( 6 ) 03/31/2031 Common Stock 42,655 I See footnote ( 2 ) ( 7 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MPM BioVentures 2014, L.P. C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE, MA02142 X Foley Todd C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM BioVentures 2014 (B), L.P. C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM Asset Management Investors BV2014 LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM BioVentures 2014 LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM BioVentures 2014 GP LLC C/O MPM ASSET MANAGEMENT LLC 450 KENDALL STREET CAMBRIDGE, MA02142 X MPM ASSET MANAGEMENT LLC C/O MPM ASSET MANAGEMENT LLC 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 10/01/2020 Signature of Reporting Person Date /s/ Todd Foley 10/01/2020 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. 10/01/2020 Signature of Reporting Person Date Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the manager of MPM Asset Management Investors BV2014 LLC 10/01/2020 Signature of Reporting Person Date /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC 10/01/2020 Signature of Reporting Person Date /s/ Ansbert Gadicke, managing director of MPM BioVentures 2014 LLC, the managing member of MPM BioVentures 2014 GP LLC 10/01/2020 Signature of Reporting Person Date /s/ Ansbert Gadicke, member of MPM Asset Management LLC 10/01/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares are held by MPM Asset Management LLC ("AM LLC"). Luke Evnin and Anbsert Gadicke are the members of AM LLC. ( 2 )Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. ( 3 )Each share of Series A-1 Preferred and Series B Preferred Stock is convertible at any time at the option of the holder, without payment of additional consideration, intoCommon Stock, on a one-for-one basis, has no expiration date and will automatically convert into shares of Common Stock upon the closing of theIssuer's initial public offering. ( 4 )The shares are held as follows: 1,382,943 by MPM BioVentures 2014, L.P. ("BV 2014"), 92,239 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 50,164 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 224,924 by MPM Sunstates Fund, L.P. ("MPM SunStates") and 33,609 by MPM Asset Management Investors Sunstates Fund LLC ("AM SunStates"). 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. MPM SunStates Fund GP LLC and MPM SunStates GP Managing Member LLC ("SunStates GP") are the direct and indirect general partners of MPM SunStates. SunStates GP is the manager of AM SunStates. Luke Evnin, Ansbert Gadicke and Todd Foley are the managing directors of BV LLC and Ansbert Gadicke is a member of SunStates GP. ( 5 )The shares are held as follows: 635,058 by BV 2014, 42,356 by BV 2014(B), 23,035 by AM BV2014, 65,708 by MPM SunStates and 9,818 by AM SunStates. ( 6 )Immediately exercisable. ( 7 )The warrants are held as follows: 24,611 by BV 2014, 1,641 by BV 2014(B), 892 by AM BV2014, 13,495 by MPM SunStates and 2,016 by AM SunStates.

Remarks: See Form 3 for MPM SunStates Fund, L.P for additional members of this joint filing

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).

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