SEC Form 3

FORM 3

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

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1. Name and Address of Reporting Person* ARCH Venture Partners VIII, LLC (Last) (First) (Middle) C/O ARCH VENTURE PARTNERS 8755 W. HIGGINS ROAD, SUITE 1025 (Street) CHICAGO IL 60631 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 07/26/2017	3. Issuer Name and Ticker or Trading Symbol Sienna Biopharmaceuticals, Inc. [ SNNA ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year) 07/26/2017
			6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series A-3 Preferred Stock	(1)	(1)	Common Stock	2,538,641	(1)	I	See Footnote(1)

Explanation of Responses:

1. This amendment is filed solely to include a copy of a power of attorney form which was inadvertently omitted from the original filing. One line in the original filing has been restated without restating the original footnotes in order to gain access to the filing system. None of the information in the body of the original filing is incorrect or being amended via this amendment.

	ARCH Venture Fund VIII, L.P. By: ARCH Venture Partners VIII, L.P. By: /s/Mark McDonnell, as Attorney-in-Fact for Keith Crandell, the Managing Director of ARCH Venture Partners VIII LLC, the GP of ARCH Venture Partners VIII, L.P., the GP of ARCH Venture Fu	07/31/2017
	ARCH Venture Fund VIII Overage, L.P. By: ARCH Venture Partners VIII, LLC By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, the Managing Director of ARCH Venture Partners VIII LLC, the GP of ARCH Venture Fund VIII Overage, L.P.	07/31/2017
	ARCH Venture Partners VIII, L.P. By: ARCH Venture Partners VIII, LLC By: /s/ Mark McDonnell as Attorney-in-Fact for Keith Crandell, the Managing Director of ARCH Venture Partners VIII, LLC, the GP of ARCH Venture Partners VIII, L.P.	07/31/2017
	ARCH Venture Partners VIII, LLC By: /s/ Mark McDonnell as Attorney-in-Fact for Keith Crandell, the Managing Director of ARCH Venture Partners VIII, LLC	07/31/2017
	/s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell	07/31/2017
	/s/ Mark McDonnell, as Attorney-in-Fact for Clinton Bybee	07/31/2017
	** 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 5 (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.