Sec Form 4 Filing - ORBIMED ADVISORS LLC @ Silverback Therapeutics, Inc. - 2020-12-08

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

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1. Name and Address of Reporting Person ORBIMED ADVISORS LLC 2. Issuer Name and Ticker or Trading Symbol Silverback Therapeutics, Inc. [ SBTX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 601 LEXINGTON AVE., 54TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 12/08/2020 (Street) NEW YORK, NY10022 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 12/08/2020 P( 1 ) 238,100 A $ 21 507,423 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 ) Common Stock 12/08/2020 C 3,462,737 ( 4 ) A 3,970,160 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 ) Common Stock 12/08/2020 C 2,493,741 ( 4 ) A 6,463,901 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 ) Common Stock 12/08/2020 C 1,055,287 ( 4 ) A 7,519,188 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 ) Common Stock 12/08/2020 P( 1 ) 952,377 A $ 21 952,377 I By OrbiMed Partners Master Fund Limited ( 3 ) ( 5 ) Common Stock 269,323 I By OPI VI -IP HoldCo LLC ( 3 ) ( 6 )

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 ( 4 ) 12/08/2020 C 12,857,142 ( 4 ) ( 4 ) Common Stock 3,462,737 $ 0 0 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 ) Series B Preferred Stock ( 4 ) 12/08/2020 C 9,259,259 ( 4 ) ( 4 ) Common Stock 2,493,741 $ 0 0 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 ) Series C Preferred Stock ( 4 ) 12/08/2020 C 3,918,279 ( 4 ) ( 4 ) Common Stock 1,055,287 $ 0 0 I By OrbiMed Private Investments VI, LP ( 2 ) ( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ORBIMED ADVISORS LLC 601 LEXINGTON AVE., 54TH FLOOR NEW YORK, NY10022 X X OrbiMed Capital GP VI LLC 601 LEXINGTON AVE., 54TH FLOOR NEW YORK, NY10022 X X ORBIMED CAPITAL LLC 601 LEXINGTON AVE., 54TH FLOOR NEW YORK, NY10022 X X Signatures OrbiMed Advisors LLCBy: /s/ Douglas Coon, Chief Compliance Officer 12/08/2020 Signature of Reporting Person Date OrbiMed Capital GP VI LLC By: /s/ Doulglas Coon, Chief Compliance Officer 12/08/2020 Signature of Reporting Person Date OrbiMed Capital LLC, By: /s/ Douglas Coon, Chief Compliance Officer 12/08/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares were purchased in the Issuer's initial public offering. ( 2 )These securities are held of record by OrbiMed Private Investments VI, LP ("OPI VI"). OrbiMed Capital GP VI LLC ("GP VI") is the general partner to OPI VI and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VI. By virtue of such relationships, GP VI and OrbiMed Advisors may be deemed to have voting and investment power with respect to the shares held by OPI VI. Both GP VI and OrbiMed Advisors may be deemed to directly or indirectly, including by reason of their mutual affiliation, to be beneficial owners of the shares held by OPI VI. OrbiMed Advisors exercise investment and voting power through a management committee comprised of Carl L. Gordon, Jonathan T. Silverstein and Sven H. Borho, each of whom disclaims beneficial ownership of the shares of OPI VI. ( 3 )This report on Form 4 is jointly filed by GP VI, OrbiMed Advisors, and OrbiMed Capital LLC ("OrbiMed Capital"). Each of the Reporting Persons disclaim beneficial ownership of the securities reported herein for purposes of Rule16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. OrbiMed Advisors has designated a representative, Peter Thompson, an employee of OrbiMed Advisors, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for purpose of Section 16 of the Exchange Act, or for any other purpose. ( 4 )All outstanding shares of Preferred Stock automatically converted into shares of Common Stock immediately upon the closing of the Issuer's initial public offering, for no additional consideration at a rate of one share of Common Stock for each 3.713 shares of Preferred Stock, based on the conversion price currently in effect. The Preferred Stock has no expiration date. ( 5 )These securities are held of record by OrbiMed Partners Master Fund Limited ("OPM"). OrbiMed Capital is the investment advisor to OPM. OrbiMed Capital is a relying advisor of OrbiMed Advisors. OrbiMed Advisors and OrbiMed Capital exercise voting and investment power through a management committee comprised of Carl L. Gordon, Jonathan T. Silverstein and Sven H. Borho, each of whom disclaims beneficial ownership of the shares held by OPM. ( 6 )These securities are held of record by OPI VI - IP HoldCo LLC ("HoldCo"). OPI VI - IP TopCo LLC ("TopCo") is the sole member of HoldCo. OrbiMed Private Investments VI - IP, LP ("OPI VI IP") is the sole member of TopCo. GP VI is the general partner of OPI VI IP. OrbiMed Advisors is the managing member of GP VI. By virtue of such relationships, OrbiMed Advisors and GP VI may be deemed to have voting and investment power over the securities held by HoldCo and as a result, may be deemed to have beneficial owners hip over such securities. Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, Jonathan T. Silverstein and Sven H. Borho, each of whom disclaims beneficial ownership of the shares held by HoldCo.

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