Filed Pursuant to Rule 424(b)(3)

Registration No. 333-206873

PROSPECTUS SUPPLEMENT NO. 7 DATED APRIL 7, 2016

TO

PROSPECTUS DATED JANUARY 15, 2016

(AS SUPPLEMENTED)

ARCH THERAPEUTICS, INC.

PROSPECTUS

Up to 25,590,599 Shares of Common Stock

This Prospectus Supplement No. 7 supplements the prospectus of Arch Therapeutics, Inc. (“the “Company”, “we”, “us”, or “our”) dated January 15, 2016 (as supplemented to date, the “Prospectus”) with the following additions and changes:

This Prospectus Supplement No. 7 should be read in conjunction with the Prospectus, which is required to be delivered with this Prospectus Supplement. This Prospectus Supplement updates, amends and supplements the information included in the Prospectus. If there is any inconsistency between the information in the Prospectus and this Prospectus Supplement, you should rely on the information in this Prospectus Supplement.

This Prospectus Supplement is not complete without, and may not be delivered or utilized except in connection with, the Prospectus, including any amendments or supplements to it.

Investing in our common stock involves a high degree of risk. Before making any investment in our common stock, you should carefully consider the risk factors for our common stock, which are described in the Prospectus, as amended or supplemented.

You should rely only on the information contained in the Prospectus, as supplemented or amended by this Prospectus Supplement No. 7 and any other Prospectus Supplement or amendment thereto. We have not authorized anyone to provide you with different information.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this Prospectus Supplement No. 7 is April 7, 2016

INDEX TO FILINGS

ANNEX A

AMENDMENT TO SELLING SECURITYHOLDER INFORMATION

This Prospectus Supplement No. 7 is being filed in connection with several changes to the selling securityholder information as set forth in the Prospectus dated January 15, 2016 (as supplemented to date, the “Prospectus”) resulting from Michael A. Parker’s transfer of the 5,000,000 shares of Common Stock and Series D Warrants exercisable for up to an additional 5,000,000 shares of Common Stock that the Company issued to him in connection with the closing of the 2015 Private Placement Financing. In particular, in March 2016, Mr. Parker transferred (i) 5,000,000 shares of Common Stock to Tungsten III, LLC (“Tungsten”), an Arizona limited liability company of which Michael Parker is the sole manager (the “Tungsten Shares”); (ii) Series D Warrants exercisable for up to 4,500,000 shares of Common Stock to Tungsten; (iii) Series D Warrants exercisable for up to 455,000 shares of Common Stock to C. Richard Childress; and (iv) Series D Warrants exercisable for up to 45,000 shares of Common Stock to Mark C. Schmitt (the “Schmitt Warrants”). The Tunsten Shares and the Schmitt Warrants were transferred without registration rights under the 2015 Registration Rights Agreement, and therefore are not being registered in the 2015 Registration Statement of which this Prospectus forms a part.

As a result of Mr. Parker’s transfers, the selling securityholders table appearing under the heading “SELLING SECURITYHOLDERS” in the Prospectus is hereby amended by (x) deleting the row for Mr. Parker from the selling securityholders table; (y) adding the rows set forth in the table below for Tungsten and Mr. Childress immediately after the row for “Intracoastal Capital, LLC” of the selling securityholders table; and (iii) replacing the current “Total” row of the selling securityholders table with the revised “Total” row in the table below: