Exhibit 99.1

IN THE UNITED STATES BANKRUPTCY COURT

FOR THE DISTRICT OF DELAWARE

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In re:

SIENNA BIOPHARMACEUTICALS, INC.,

Debtor.¹

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Chapter 11

Case No. 19-12051 (MFW)

Objection Deadline: October 8, 2019 at 4:00 p.m. (ET)

Hearing Date: October 15, 2019 at 11:30 a.m. (ET)

Docket Ref. No. 40

NOTICE OF INTERIM ORDER (I) ESTABLISHING

NOTICE AND HEARING PROCEDURES FOR TRADING OF

SIENNA EQUITY SECURITIES AND (II) GRANTING RELATED RELIEF

TO ALL HOLDERS OF EQUITY INTERESTS IN SIENNA BIOPHARMACEUTICALS, INC.:

PLEASE TAKE NOTICE THAT on September 16, 2019 (the “Petition Date”), the above-captioned debtor and debtor in possession (the “Debtor”) commenced a case under chapter 11 of title 11 of the United States Code, 11 U.S.C. §§ 101-1532 (the “Bankruptcy Code”). Subject to certain exceptions, section 362 of the Bankruptcy Code operates as a stay of any act to obtain possession of property of the Debtor’s estate or of property from the Debtor’s estate or to exercise control over property of the Debtor’s estate.

PLEASE TAKE FURTHER NOTICE THAT on the Petition Date, the Debtor filed a motion seeking entry of an order pursuant to sections 105, 362, and 541 of the Bankruptcy Code (a) establishing notification and hearing procedures for trading of Sienna Biopharmaceuticals, Inc. (“Sienna”) equity securities and (b) granting related relief (the “Motion”).

PLEASE TAKE FURTHER NOTICE THAT on September 18, 2019, the United States Bankruptcy Court for the District of Delaware (the “Court”) entered an order establishing notification and hearing procedures for trading of Sienna equity securities [Docket No. 40] (the “Interim Order”), thereby approving the procedures set forth below in order to preserve the Debtor’s Tax Attributes (as defined in the Motion). A final hearing on the Motion will be held on October 15, 2019 at 11:30 a.m. (Eastern Time) (the “Final Hearing”). Any objections to the relief granted in the Interim Order must be filed with the Court and served upon counsel for the Debtor no later than seven (7) days prior to the Final Hearing (the “Objection Deadline”). If an objection is timely filed and served prior to the Objection Deadline, such objection will be heard at the Final Hearing on the Motion. If no objections are timely filed and served, Debtor’s counsel will file a certification of counsel to that effect attaching a final form of order.

¹	The last four digits of the Debtor’s federal tax identification number are 4627. The Debtor’s mailing address is 30699 Russell Ranch Road, Suite 140, Westlake Village, California 91362.

PLEASE TAKE FURTHER NOTICE THAT, pursuant to the Interim Order, the following procedures shall apply to holding and trading of Sienna equity securities:

Any purchase, sale, or other transfer of Sienna equity securities in violation of the procedures set forth herein (including the notice requirements set forth herein and in the Interim Order) shall be null and void ab initio as an act in violation of the automatic stay under sections 362 and 105(a) of the Bankruptcy Code.

Any person or entity (as defined in Treasury Regulations Section 1.382-3(a)(l)) who currently is or becomes a Substantial Shareholder (as defined in Paragraph (f) below) shall file with the Court, and serve on Debtor’s counsel, (i) Latham & Watkins LLP, 355 South Grand Avenue, Suite 100, Los Angeles, California 90071 (Attn: Peter M. Gilhuly and Ted A. Dillman), and (ii) Young Conaway Stargatt & Taylor, LLP, Rodney Square, 1000 North King Street, Wilmington, Delaware 19801 (Attn: Michael R. Nestor and Kara Hammond Coyle), a notice of such status, in the form of Exhibit 1 attached to the Interim Order, on or before the later of (i) 20 calendar days after the date of this Notice and (ii) 14 calendar days after becoming a Substantial Shareholder.

At least 14 calendar days prior to effectuating any transfer of equity securities (including Options to acquire such securities, as defined in Paragraph (f) below) that would result in an increase in the amount of Stock (as defined in Paragraph (f) below) beneficially owned by a Substantial Shareholder (as defined in Paragraph (f) below) or would result in a person or entity becoming a Substantial Shareholder, such Substantial Shareholder (or person or entity that may become a Substantial Shareholder) shall file with the Court, and serve on counsel to the Debtor, advance written notice, in the form of Exhibit 2 attached to the Interim Order, of the intended transfer of equity securities.

At least 14 calendar days prior to effectuating any transfer of equity securities (including Options to acquire such securities, as defined in Paragraph (f) below) that would result in a decrease in the amount of Stock (as defined in Paragraph (f) below) beneficially owned by a Substantial Shareholder (as defined in Paragraph (f) below) or would result in a person or entity ceasing to be a Substantial Shareholder, such Substantial Shareholder shall file with the Court, and serve on counsel to the Debtor, advance written notice, in the form of Exhibit 3 attached to the Interim Order, of the intended transfer of equity securities (the notices required to be filed and served under Paragraph (c) and this Paragraph (d), each a “Notice of Proposed Transfer”).

The Debtor shall have 14 calendar days after receipt of a Notice of Proposed Transfer to file with the Court and serve on such Substantial Shareholder (as defined in Paragraph (f) below) (or person or entity that may become a Substantial Shareholder) an objection to any proposed transfer of equity securities described in the Notice of Proposed Transfer on the grounds that such transfer may adversely affect the Debtor’s ability to utilize its Tax Attributes (as defined in the Motion). If the Debtor files an objection, such transaction will not be effective unless approved by a final and non-appealable order of the Court. If the Debtor does not object within such 14-day period, such transaction may proceed solely as set forth in the Notice of Proposed Transfer. Further transactions within the scope of this Paragraph (e) must be the subject of additional notices as set forth herein, with an additional 14-day waiting period.

For purposes of these procedures, (A) a “Substantial Shareholder” is any person or entity (as defined in Treasury Regulations Section 1.382-3(a)) which beneficially owns at least 4.5% of all issued and outstanding shares (equal to, as of August 27, 2019, approximately 1,391,000 shares²) of the common stock of Sienna (the “Stock”), and (B) “ownership” (or any variation thereof of the Stock and Options to acquire the Stock) shall be determined in accordance with applicable rules under Section 382 of title 26 of the United States Code, the Internal Revenue Code of 1986, as amended, Treasury Regulations promulgated thereunder, and rulings issued by the United States Internal Revenue Service, and thus, to the extent provided therein, from time to time shall include, without limitation, (i) direct and indirect ownership (e.g., a holding company would be considered to beneficially own all shares owned or acquired by its subsidiaries); (ii) ownership by the holder’s family members and persons acting in concert with the holder to make a coordinated acquisition of stock; and (iii) ownership of an Option to acquire the Stock, but only to the extent such Option is treated as exercised under Treasury Regulations Section 1.382-4(d). An “Option” to acquire stock includes all interests described in Treasury Regulations Section 1.382-4(d)(9), including any contingent purchase, warrant, convertible debt, put, stock subject to risk of forfeiture, contract to acquire stock, or similar interest, regardless of whether it is contingent or otherwise not currently exercisable.

PLEASE TAKE FURTHER NOTICE THAT, upon the request of any person, counsel to the Debtor, (i) Latham & Watkins LLP, 355 South Grand Avenue, Suite 100, Los Angeles, California 90071-1560 (Attn: Peter M. Gilhuly, Esq. and Ted A. Dillman, Esq. (emails: peter.gilhuly@lw.com and ted.dillman@lw.com)), and (ii) Young Conaway Stargatt & Taylor, LLP, Rodney Square, 1000 North King Street, Wilmington, Delaware 19801 (Attn: Michael R. Nestor and Kara Hammond Coyle (emails: mnestor@ycst.com and kcoyle@ycst.com)), will provide a form of each of the required notices described above.

²	Based upon 30,907,542 million shares of Sienna equity securities issued and outstanding as of August 27, 2019.

PLEASE TAKE FURTHER NOTICE THAT a copy of the Interim Order may be obtained free of charge online at https://dm.epiq11.com/Sienna.

FAILURE TO FOLLOW THE PROCEDURES SET FORTH IN THIS NOTICE SHALL CONSTITUTE A VIOLATION OF, AMONG OTHER THINGS, THE AUTOMATIC STAY PRESCRIBED BY SECTION 362 OF THE BANKRUPTCY CODE.

ANY PROHIBITED PURCHASE, ACQUISITION, ACCUMULATION, SALE, TRADE OR OTHER TRANSFER OF SIENNA EQUITY SECURITIES IN VIOLATION OF THE INTERIM ORDER SHALL BE NULL AND VOID AB INITIO AND MAY BE PUNISHED BY CONTEMPT OR OTHER SANCTIONS IMPOSED BY THE COURT.

PLEASE TAKE FURTHER NOTICE THAT the requirements set forth in this Notice are in addition to the requirements of applicable securities, corporate, and other laws, and do not excuse compliance therewith.


Dated: September 18, 2019 Wilmington, Delaware						YOUNG CONAWAY STARGATT & TAYLOR, LLP

						/s/ Kara Hammond Coyle
						Michael R. Nestor (No. 3526)
						Kara Hammond Coyle (No. 4410)
						1000 North King Street
						Wilmington, Delaware 19801
						Telephone: (302) 571-6600
						Facsimile: (302) 571-1253
						Email: mnestor@ycst.com
						kcoyle@ycst.com

						– and –

						LATHAM & WATKINS LLP


						Peter M. Gilhuly (pro hac vice admission pending)
						Ted A. Dillman (pro hac vice admission pending)
						355 South Grand Avenue, Suite 100
						Los Angeles, California 90071
						Telephone: (213) 485-1234
						Facsimile: (213) 891-8763
						Email: peter.gilhuly@lw.com
						ted.dillman@lw.com

						Proposed Counsel for Debtor and Debtor in Possession

Sienna Biopharmaceuticals, Inc. 8-K