UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 21, 2017

Regulus Therapeutics Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (858) 202-6300

N/A

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company  ☒

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 13(a) of the Exchange Act.  ☒

On December 21, 2017, Regulus Therapeutics Inc. (the “Company”) received a letter (the “Notice”) from The Nasdaq Stock Market (“Nasdaq”) advising the Company that for 30 consecutive trading days preceding the date of the Notice, the bid price of the Company’s common stock had closed below the $1.00 per share minimum required for continued listing on The Nasdaq Global Market pursuant to Nasdaq Listing Rule 5450(a)(1) (the “Minimum Bid Price Requirement”).

The Notice has no effect on the listing of the Company’s common stock at this time, and the Company’s common stock continues to trade on The Nasdaq Global Market under the symbol “RGLS.”

Under Nasdaq Listing Rule 5810(c)(3)(A), if during the 180 calendar day period following the date of the Notice (the “Compliance Period”) the closing bid price of the Company’s common stock is at or above $1.00 for a minimum of 10 consecutive business days, the Company will regain compliance with the Minimum Bid Price Requirement and its common stock will continue to be eligible for listing on The Nasdaq Global Market absent noncompliance with any other requirement for continued listing.

If the Company does not regain compliance with the Minimum Bid Price Requirement by the end of the Compliance Period, under Nasdaq Listing Rule 5810(c)(3)(A)(ii) if on the last day of the Compliance Period the Company is in compliance with the market value of publicly held shares requirement for continued listing as well as all other standards for initial listing of its common stock on The Nasdaq Capital Market (other than the bid price requirement), the Company may apply to transfer the listing of its common stock to The Nasdaq Capital Market if the Company also provides written notice to Nasdaq of its intention to cure the deficiency during a second compliance period (by effecting a reverse stock split if necessary), at which point Nasdaq may grant the Company additional time to regain compliance with the Minimum Bid Price Requirement.

If the Company does not regain compliance with the Minimum Bid Price Requirement by the end of the Compliance Period and it determines not to submit a transfer application and make the required representation, the Company’s common stock will be subject to delisting.

The Company intends to monitor the closing bid price of its common stock and may, if appropriate, consider implementing available options to regain compliance with the Minimum Bid Price Requirement.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.