As filed with the Securities and Exchange Commission on February 7, 2020

Registration No. 333-        

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

SALARIUS PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

2450 Holcombe Blvd.

Suite J-608

Houston, TX 77021

(346) 772-0346

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

David J. Arthur

President and Chief Executive Officer

2450 Holcombe Blvd.

Suite J-608

Houston, TX 77021

(346) 772-0346

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

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of the registration statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box.  ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☒  333-235879

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

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 the 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.  ☒

CALCULATION OF REGISTRATION FEE

This Registration Statement shall become effective upon filing with the Securities and Exchange Commission in accordance with Rule 462(b) under the Securities Act of 1933, as amended.

EXPLANATORY NOTE AND

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

This Registration Statement is being filed pursuant to Rule 462(b) under the Securities Act of 1933, as amended, and includes the registration statement facing page, this page, the signature page, an exhibit index and the required opinion and consents. This Registration Statement is being filed solely to register up to an aggregate of $3,680,000 in (i) additional Class A Units, with each Class A Unit consisting of one share of the Company’s common stock, par value $0.0001 per share (the “common stock”), one warrant to purchase one share of common stock, (ii) additional Class B Units, with each Class B Unit consisting of one share of the Company’s Series A convertible preferred stock, par value $0.0001 per share (the “Series A Preferred Stock”), one warrant to purchase one share of common stock, (iii) shares of Common Stock issuable upon conversion of the additional shares of Series  A Preferred Stock and (iv) shares of Common Stock issuable upon exercise of the warrants included in the additional Class A Units and Class B Units. This Registration Statement incorporates by reference the contents of, including all amendments and exhibits thereto, the Registration Statement on Form S-1 (Registration No. 333-235879), which was declared effective by the Securities and Exchange Commission on February 6, 2020 (the “Prior Registration Statement”).

The additional securities that are being registered are in an amount and at a price that together represent no more than 20% of the maximum aggregate offering price set forth in the Calculation of Registration Fee table contained in the Prior Registration Statement.

The required opinions and consents are listed on the Exhibit Index attached hereto and filed herewith.

EXHIBIT INDEX

II-1

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Houston, State of Texas on February 6, 2020.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities indicated on the dates indicated.