SEC Form 4

FORM 4		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 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* ORBIMED ADVISORS LLC (Last) (First) (Middle) 601 LEXINGTON AVENUE, 54TH FLOOR (Street) NEW YORK NY 10022 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol SI-BONE, Inc. [ SIBN ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 10/19/2018
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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		605,964	A	(1)	605,964	I	By OrbiMed Private Investments V, LP(2)(3)
Common Stock	10/19/2018		C		179,404	A	(4)	785,368	I	By OrbiMed Private Investments V, LP(2)(3)
Common Stock	10/19/2018		P		200,000	A	$15	985,368	I	By OrbiMed Private Investments V, LP(2)(3)

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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 6 Preferred Stock	(1)	10/19/2018		C			572,326	(1)	(1)	Common Stock	605,964	(1)	0	I	By OrbiMed Private Investments V, LP(2)(3)
Series 7 Preferred Stock	(4)	10/19/2018		C			179,404	(4)	(4)	Common Stock	179,404	(4)	0	I	By OrbiMed Private Investments V, LP(2)(3)

1. Name and Address of Reporting Person* ORBIMED ADVISORS LLC (Last) (First) (Middle) 601 LEXINGTON AVENUE, 54TH FLOOR (Street) NEW YORK NY 10022 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer X Director 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* OrbiMed Capital GP V LLC (Last) (First) (Middle) 601 LEXINGTON AVENUE, 54TH FLOOR (Street) NEW YORK NY 10022 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer X Director 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. 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.

2. Shares held by OrbiMed Private Investments V, LP. ("OPI V"). OrbiMed Capital GP V LLC ("GP V") is the general partner of OPI V and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP V. By virtue of such relationships, GP V and OrbiMed Advisors may be deemed to have voting and investment power with respect to the shares held by OPI V and as a result may be deemed to have have beneficial ownership of such shares. OrbiMed Advisors exercises investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein. David P. Bonita, a member of the Issuer's board of directors, is an employee of OrbiMed Advisors.

3. This report on Form 4 is jointly filed by GP V and OrbiMed Advisors. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-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. This report shall not be deemed an admission that any such entity is a beneficial owner of such securities for purpose of Section 16 of the Exchange Act, or for any other purpose.

4. The Issuer's 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.

Remarks:

	/s/ Douglas Coon, as attorney-in-fact	10/19/2018
	** Signature of Reporting Person	Date
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.