SEC FORM 3

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^*

Burow Kristina

(Last)

(First)

(Middle)

C/O ARCH VENTURE PARTNERS

8755 W. HIGGINS ROAD, SUITE 1025

(Street)

CHICAGO

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)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

5. If Amendment, Date of Original Filed (Month/Day/Year)

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)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	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)
Series A-3 Preferred Stock	⁽¹⁾	⁽²⁾	Common Stock	2,538,641	⁽¹⁾	I	See Footnote⁽³⁾
Series A-3 Preferred Stock	⁽¹⁾	⁽²⁾	Common Stock	563,072	⁽¹⁾	I	See Footnote⁽⁴⁾
Series B Preferred Stock	⁽¹⁾	⁽²⁾	Common Stock	211,934	⁽¹⁾	I	See Footnote⁽³⁾
Series B Preferred Stock	⁽¹⁾	⁽²⁾	Common Stock	319,421	⁽¹⁾	I	See Footnote⁽⁴⁾

Explanation of Responses:

1. The shares of the Issuer's Preferred Stock automatically convert into shares of the Issuer's Common Stock, for no additional consideration, on a 1:1 basis immediately prior to the consummation of the Issuer's initial public offering.

2. The expiration date is not relevant to the conversion of these securities.

3. The shares are directly held by ARCH Venture Fund VIII, L.P. ("ARCH VIII"). ARCH Venture Partners VIII, L.P. (the "GPLP"), as the sole general partner of ARCH VIII, may be deemed to beneficially own certain of the shares held by ARCH VIII. ARCH Venture Partners VIII, LLC ("GPLLC"), as the sole general partner of GPLP, may be deemed to beneficially own the shares held by GPLP. The Reporting Person has an interest in the GPLP and the GPLLC, but does not have voting or investment control over the shares held by ARCH VIII. The Reporting Person disclaims beneficial ownership of such shares except to the extent of any pecuniary interest therein.

4. The shares are directly held by ARCH Venture Fund VIII Overage, L.P. ("ARCH Overage"). GPLLC, as the sole general partner of ARCH Overage, may be deemed to beneficially own the shares held by ARCH Overage. The Reporting Person has an interest in the GPLLC, but does not have voting or investment control over the shares held by ARCH Overage. The Reporting Person disclaims beneficial ownership of such shares except to the extent of any pecuniary interest therein.

	/s/ Timothy K. Andrews, attorney-in-fact for Kristina Burow	07/26/2017
	** 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.