SecProbe.io

May 6, 2014

Via E -mail
Paul Lammers, M.D., M.Sc.
President and Chief Executive Officer
Mirna Therapeutics, Inc.
2150 Woodward Street, Suite 100
Austin, TX 78744

Re: Mirna Therapeutics, Inc.
Amendment No. 2 to Draft Registration Statement on Form S -1
Submitted April 22, 2014
CIK No. 0001527599

Dear Dr. Lammers:

We have reviewed your amended confidential draft registration statement and have the
following additional comments. In some of our comments, we may ask you to provide us with
infor mation so we may better understand your disclosure.

Please respond to this letter by providing the requested infor mation and either sub mitting
an amended confidential draft re gistration state ment or publicly  filing your registration state ment
on EDGAR.  If you do  not believe our comments apply to your facts and circu mstances or do
not believe an  amendment is a ppropriate, please tell us why in your response.

After revie wing the infor mation you provide  in response to these com ments and your
amended confidential draft registration state ment or filed registration state ment, we may have
additio nal co mments.

Use o f Proceeds, page 63

1. Please revise your disclosure to allocate the amount of  proceeds from the offering you
will use:
 To complete the Phase 1 clinical trial for unresectable primary liver cancer or
metastatic solid tumors with liver involvement;
 To complete the Phase 1 clinical trial cohort for hematological malignancies;
 To init iate the Phase 2 clinical trial for unresectable primary liver cancer or
metastatic solid tumors with liver involvement; and
 To initiate the Phase 2 clinical trial cohort for hematological malignancies.

Please make any necessary conforming changes to your  Prospectus Summary as well.

Paul Lammers, M.D., M.Sc.
Mirna Therapeutics, Inc.
May 6 , 2014
Page 2

 Results of Operations
Comparison of Years Ended December  31, 2011 and 2012
Research and Development Expenses, page  78

2. Please refer to your response to prior comment 17.
 Your disclosure that provides several reasons for the $3.1 million increase in 2012
is vague.   Based on the information you provide in the table in your response, the
increase appears to be substantively due to the increases in fees for contract
research associations and other external costs. Revise your disc losure to quantify
the changes in each of these two categories and to explain the reason for the
increase in each category.
 In the asterisk to the table in your response, you indicate that cost reimbursements
are not earned until the cost is paid by the C ompany.   Clarify under research and
development costs in Note 2. Summary of Significant Accounting Policies in your
notes to financial statements, where you indicate that the proceeds from
government grants are accounted for as a reduction of research and development
expenses, whether you recognize the proceeds at the time you pay the cost or
when the reimbursement is received.

Business
MRX34 Clinical Development Program, page 98

3. We note your response to our prior comment 12 and your revised disclosure that some of
the adverse events reported “were characterized as severe and related to the
administration of MRX34.”  Please disclose what the serious adverse events were, and
disclos e the exact number of patients who experienced serious adverse events which were
determined to be related to treatment.  Please include similarly specific disclosure in the
risk factor on page 50.

If you intend to respond to these comments with an amend ed draft registration statement,
please submit it and any associated correspondence in accordance with the guidance we provide
in the Division’s October 11, 2012 announcement on the SEC website at
http://www.sec.gov/divisions/corpfin/cfannouncements/drsfil ingprocedures101512.htm.

Please keep in mind that we may publicly post filing review correspondence in
accordance with our December 1, 2011 policy
(http://www.sec.gov/divisions/corpfin/cfannouncements/edgarcorrespondence.htm). If you
intend to use Rule 83  (17 CFR 200.83) to request confidential treatment of information in the
correspondence you submit on EDGAR, please properly mark that information in each of your
confidential submissions to us so we do not repeat or refer to that information in our commen t
letters to you.

Paul Lammers, M.D., M.Sc.
Mirna Therapeutics, Inc.
May 6 , 2014
Page 3

 You may contact Ibolya Ignat at (202) 551 -3656 or Jim Rosenberg at (202) 551 -3679 if
you have questions regarding comments on the financial statements and related matters. Please
contact Austin Stephenson at (202) 551 -3192, Bryan Pitk o at (202) 551 -3203, or me at (202)
551-3715 with any other questions.

Sincerely,

         /s/ Bryan J. Pitko for

Jeffrey P. R iedler
Assista nt Direct or

cc: Via E -mail
 Alan C. Mendelson, Esq.
 Latham & Watkins LLP