SNNA Sienna Biopharmaceuticals Inc

As filed with the Securities and Exchange Commission on December 11, 2019

Registration No. 333-219609

Registration No. 333-223689

Registration No. 333-230257

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-219609

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-223689

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-230257

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

30699 Russell Ranch Road, Suite 140

Westlake Village, CA 91362

(818) 629-2256

(Address, including zip code and telephone number, including area code, of registrant’s principal executive office)

2010 Equity Incentive Plan, as amended

2017 Incentive Award Plan

2017 Employee Stock Purchase Plan

(Full title of the Plans)

Frederick C. Beddingfield III, M.D., Ph.D.

President and Chief Executive Officer

Sienna Biopharmaceuticals, Inc.

30699 Russell Ranch Road, Suite 140

Westlake Village, CA 91362

(818) 629-2256

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☒

DEREGISTRATION OF UNSOLD SECURITIES

These Post-Effective Amendments (these “Post-Effective Amendments”) filed by Sienna Biopharmaceuticals, Inc., a Delaware corporation (the “Registrant”), relate to the following Registration Statements on Form S-8 (each, a “Registration Statement,” and collectively, the “Registration Statements”) filed by the Registrant with the U.S. Securities and Exchange Commission (the “Commission”).

The Registrant has informed the Nasdaq Hearings Panel (the “Panel”) regarding the results of the auction process of the Registrant’s assets, pursuant to the Panel’s decision letter dated November 12, 2019. The Registrant has requested to withdraw from the hearing process and that its common stock be suspended effective December 13, 2019 (the “Delisting”).

In connection with the Delisting, the Registrant has terminated any and all offerings pursuant to the Registration Statements. In accordance with undertakings made by the Registrant in the Registration Statements to remove from registration, by means of a post-effective amendment, any of the securities that remain unsold at the termination of the offerings, the Registrant hereby removes from registration all Shares registered but unsold under the Registration Statements as of the date hereof.