As filed with the Securities and Exchange Commission on March 29, 2016

Registration No. 333-                

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Mirna Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

2150 Woodward Street, Suite 100

Austin, TX 78744

(512) 901-0900

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

2015 Equity Incentive Award Plan

2015 Employee Stock Purchase Plan

(Full Title of the Plan)

Paul Lammers, M.D., M.Sc.

President & Chief Executive Officer

Mirna Therapeutics, Inc.

2150 Woodward Street, Suite 100

Austin, TX 78744

(512) 901-0900

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

Copies to:

Alan C. Mendelson, Esq.
Mark V. Roeder, Esq.
Latham & Watkins LLP
140 Scott Drive
Menlo Park, CA 94025
Telephone: (650) 328-4600
Facsimile: (650) 463-2600

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

CALCULATION OF REGISTRATION FEE

(1)           Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the “Securities Act”), this registration statement shall also cover any additional shares of the Registrant’s common stock that become issuable under the 2015 Equity Incentive Award Plan (the “2015 Plan”) and the 2015 Employee Stock Purchase Plan (the “ESPP”) by reason of any stock dividend, stock split, recapitalization or similar transaction effected without the Registrant’s receipt of consideration which would increase the number of outstanding shares of common stock.

(2)           Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rule 457(c) and Rule 457(h) promulgated under the Securities Act. The offering price per share and the aggregate offering price for shares reserved for future issuance under the 2015 Plan and ESPP are based on the average of the high and the low price of Registrant’s common stock as reported on NASDAQ on March 24, 2016. The chart below details the calculations of the registration fee:

(3)           Represents the additional shares of common stock available for future issuance under the 2015 Plan resulting from an annual increase as of January 1, 2016.

(4)           Represents the additional shares of common stock available for future issuance under the ESPP resulting from an annual increase as of January 1, 2016.

Proposed sale to take place as soon after the effective date of the

registration statement as awards under the plans are exercised and/or vest.

EXPLANATORY NOTE

This Registration Statement on Form S-8 is being filed for the purpose of registering an additional 1,249,832 shares of the Registrant’s common stock issuable under the following employee benefit plans for which a Registration Statement of the Registrant on Form S-8 (File No. 333-207299) is effective: (i) the 2015 Equity Incentive Award Plan, as a result of the operation of an automatic annual increase provision therein, which added 1,041,527 shares of common stock, and (ii) the 2015 Employee Stock Purchase Plan, as a result of the operation of an automatic annual increase provision therein, which added 208,305 shares of common stock.

INCORPORATION BY REFERENCE OF CONTENTS OF REGISTRATION STATEMENT ON FORM S-8

Pursuant to Instruction E of Form S-8, the contents of the Registration Statement on Form S-8 filed with the Securities and Exchange Commission on November 12, 2014 (File No. 333-207299) are incorporated by reference herein.

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Signatures

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant has duly caused this Registration Statement on Form S-8 to be signed on its behalf by the undersigned, thereunto duly authorized, in Austin, Texas, on March 29, 2016.

Power of Attorney

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Paul Lammers, Alan Fuhrman and Jon Irvin, and each of them acting individually, as his or her true and lawful attorneys-in-fact and agents, each with full power of substitution, for him or her in any and all capacities, to sign any and all amendments to this Registration Statement, including post-effective amendments or any abbreviated registration statement and any amendments thereto filed pursuant to Rule 462(b) increasing the number of securities for which registration is sought, and to file the same, with all exhibits thereto and other documents in connection therewith, with the SEC, granting unto said attorneys-in-fact and agents, with full power of each to act alone, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully for all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or his, her or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, this Amendment to Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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Exhibit Index

#Indicates management contract or compensatory plan.

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Exhibit 5.1

Mirna Therapeutics, Inc.

2150 Woodward Street, Suite 100

Austin, TX 78744

Re:                             Registration Statement on Form S-8; 1,249,834 shares of Common Stock of Mirna Therapeutics, Inc., par value $0.001 per share

Ladies and Gentlemen:

We have acted as special counsel to Mirna Therapeutics, Inc., a Delaware corporation (the “Company”), in connection with the registration by the Company of 1,249,834 shares of common stock of the Company, par value $0.001 per share (the “Shares”), issuable under the 2015 Equity Incentive Award Plan (the “2015 Plan”) and 2015 Employee Stock Purchase Plan (the “ESPP” and together with the 2015 Plan, the “Plans”).

The Shares are included in a registration statement on Form S—8 under the Securities Act of 1933, as amended (the “Act”), filed with the Securities and Exchange Commission (the “Commission”) on March 29, 2016 (the “Registration Statement”).  This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or the related prospectuses, other than as expressly stated herein with respect to the issue of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter.  With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters.  We are opining herein as to the General Corporation Law of the State of Delaware (the “DGCL”), and we express no opinion with respect to any other laws.

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, when the Shares shall have been duly registered on the books of the transfer agent and registrar therefor in the name or on behalf of the purchasers and have been issued by the Company against payment therefor (not less than par value) in the circumstances contemplated by the Plans, assuming in each case that the individual issuances, grants or awards under the Plans are duly authorized by all necessary corporate action and duly issued, granted or awarded and exercised in accordance with the requirements of law and the Plans (and the agreements and awards duly adopted thereunder and in accordance therewith), the issue and sale of the Shares will have been duly authorized by all necessary corporate action of the Company, and the Shares will be validly issued, fully paid and nonassessable.  In rendering the foregoing opinion, we have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the DGCL.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act.  We consent to your filing this opinion as an exhibit to the Registration Statement.  In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the 2015 Equity Incentive Award Plan and 2015 Employee Stock Purchase Plan of Mirna Therapeutics, Inc. of our report dated March 29, 2016 with respect to the financial statements of Mirna Therapeutics, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2015, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Austin, Texas

March 29, 2016