Page 1

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 ( Mark One ) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FORM 10 - K FOR THE FISCAL YEAR ENDED DECEMBER 31 , 2020 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM Delaware ( State or Other Jurisdiction of Incorporation or Organization ) or 10628 Science Center Drive , Suite 225 San Diego CA ( Address of Principal Executive Offices ) Title of Each Class Common Stock , par value $ 0.001 per share Regulus Therapeutics Inc. ( Exact name of registrant as specified in its charter ) Commission file number : 001-35670 ΤΟ ( 858 ) 202-6300 ( Registrant's Telephone Number , Including Area Code ) Securities registered pursuant to Section 12 ( b ) of the Act : 26-4738379 ( I.R.S. Employer Identification No. ) 92121 ( Zip Code ) Trading Symbol ( s ) RGLS Securities registered pursuant to Section 12 ( g ) of the Act : None Name of Each Exchange on Which Registered The Nasdaq Stock Market LLC Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No ý No ý Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . Yes Indicate by check mark whether the registrant : ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes ý No