Sec Form 4 Filing - Skyline Venture Partners V LP @ SI-BONE, Inc. - 2018-10-19

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 Skyline Venture Partners V LP 2. Issuer Name and Ticker or Trading Symbol SI-BONE, Inc. [ SIBN] 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) 525 UNIVERSITY AVENUE, SUITE 1350 3. Date of Earliest Transaction (MM/DD/YY) 10/19/2018 (Street) PALO ALTO, CA94301 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 10/19/2018 C 2,213,425 A 2,213,425 I By Skyline Venture Partners V, L.P. ( 2 ) Common Stock 10/19/2018 C 792,195 A 3,005,620 I By Skyline Venture Partners V, L.P. ( 2 ) Common Stock 10/19/2018 C 690,689 A 3,696,309 I By Skyline Venture Partners V, L.P. ( 2 ) Common Stock 10/19/2018 C 398,676 A 4,094,985 I By Skyline Venture Partners V, L.P. ( 2 ) Common Stock 10/19/2018 P 325,000 A $ 15 4,419,985 I By Skyline Venture Partners V, L.P. ( 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 Warrant (right to buy) $ 9.1 10/19/2018 X 39,421 ( 4 ) ( 4 ) Series 5 Preferred Stock 39,421 $ 0 0 I By Skyline Venture Partners V, L.P. ( 2 ) Series 5 Preferred Stock $ 9.1 10/19/2018 X 39,421 ( 1 ) ( 1 ) Common Stock 39,421 $ 0 816,099 I By Skyline Venture Partners V, L.P. ( 2 ) Series 5 Preferred Stock ( 1 ) 10/19/2018 S( 5 ) 23,904 ( 1 ) ( 1 ) Common Stock 23,904 $ 14 792,195 I By Skyline Venture Partners V, L.P. ( 2 ) Series 4 Preferred Stock ( 1 ) 10/19/2018 C 2,213,425 ( 1 ) ( 1 ) Common Stock 2,213,425 ( 1 ) 0 I By Skyline Venture Partners V, L.P. ( 2 ) Series 5 Preferred Stock ( 1 ) 10/19/2018 C 792,195 ( 1 ) ( 1 ) Common Stock 792,195 ( 1 ) 0 I By Skyline Venture Partners V, L.P. ( 2 ) Series 6 Preferred Stock ( 3 ) 10/19/2018 C 652,347 ( 3 ) ( 3 ) Common Stock 690,689 ( 3 ) 0 I By Skyline Venture Partners V, L.P. ( 2 ) Series 7 Preferred Stock ( 1 ) 10/19/2018 C 398,676 ( 1 ) ( 1 ) Common Stock 398,676 ( 1 ) 0 I By Skyline Venture Partners V, L.P. ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Skyline Venture Partners V LP 525 UNIVERSITY AVENUE, SUITE 1350 PALO ALTO, CA94301 X Skyline Venture Management V, LLC 525 UNIVERSITY AVENUE, SUITE 1350 PALO ALTO, CA94301 X Freund John Gordon 525 UNIVERSITY AVENUE, SUITE 1350 PALO ALTO, CA94301 X X KANEKO YASUNORI 525 UNIVERSITY AVENUE, SUITE 1350 PALO ALTO, CA94301 X Signatures Skyline Venture Partners V, L.P., By: Skyline Venture Management V, LLC, Its: General Partner, By: /s/ Kerensa Kenny, Attorney-in-Fact 10/19/2018 Signature of Reporting Person Date Skyline Venture Management V, LLC, By: /s/ Kerensa Ke nny, Attorney-in-Fact 10/19/2018 Signature of Reporting Person Date /s/ John G. Freund, /s/ Kerensa Kenny, Attorney-in-Fact 10/19/2018 Signature of Reporting Person Date /s/ Yasunori Kaneko, /s/ Kerensa Kenny, Attorney-in-Fact 10/19/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Issuer's Series 4 Preferred Stock, Series 5 Preferred Stock and Series 7 Preferred Stock automatically converted into an equal number of shares of Issuer's common stock immediately upon the closing of the Issuer's initial public offering and has no expiration date. ( 2 )Shares held by Skyline Venture Partners V, L.P. ("SVP V"). Skyline Venture Management V, LLC ("LLC") is the general partner of SVP V and as such may be deemed to have voting and investment power with respect to the securities of SVP V. John G. Freund, a member of the Issuer's board of directors, together with Yasunori Kaneko, are the managing directors of LLC and each may be deemed to have voting and investment power with respect to the securities held by SVP V. Dr. Freund and Mr. Kaneko disclaim beneficial ownership of such securities, except to the extent of their pecuniary interest therein. ( 3 )The Issuer's Series 6 Preferred Stock automatically converted into approximately 1.05878 shares of Issuer's common stock immediately upon the closing of the Issuer's initial public offering and has no expiration date. ( 4 )Shares subject to the warrant are immediately exercisable. The warrant will expire in connection with the closing of the Issuer's initial public offering. ( 5 )Immediately prior to the closing of the Issuer's initial public offering, SVP V exercised a warrant to purchase 39,421 shares of Series 5 Preferred Stock at an exercise price of $9.10 per share. The exercise price was paid on a net exercise cashless basis calculated using the Issuer's initial public offering price of $15.00, resulting in the Issuer withholding 23,904 of the warrant shares to pay the exercise price and issuing SVP V the remaining 15,517 shares.

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