SecProbe.io

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 SYNLOGIC, INC.
 PO Box 30 Winchester,
Massachusetts 01890 August 18, 2025 VIA EDGAR
 U.S. Securities and Exchange Commission Division of
Corporation Finance 100 F Street, N.E.
 Washington, D.C. 20549 Attention: Ms. Doris Stacey Gama
 Re: Synlogic, Inc. Registration Statement on Form
 S-3 Filed August 8, 2025
 File No. 333-289415 (the “Registration Statement”)
 Acceleration Request Ladies and
Gentlemen: In accordance with Rule 461 of Regulation C promulgated under the Securities Act of 1933, as amended, Synlogic, Inc. (the
“Registrant”) hereby respectfully requests that the Securities and Exchange Commission accelerate the effective date of the above-referenced Registration Statement to Wednesday, August 20, 2025, at 4:01 p.m., Eastern Time, or as
soon as thereafter practicable. The cooperation of the staff in meeting the timetable described above is very much appreciated.
 Please contact Nishant Dharia, Esq. of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., counsel to the Registrant, at (212) 692-8174 with any questions regarding this request.

 Very truly yours,

 SYNLOGIC, INC.

 /s/ Mary Beth Dooley

 Mary Beth Dooley Principal Executive Officer
and Principal Financial Officer

 cc:
 Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
 Daniel A. Bagliebter, Esq.
 Nishant Dharia, Esq.

<DOCUMENT>
<TYPE>TEXT-EXTRACT
<SEQUENCE>2
<FILENAME>filename2.txt
<TEXT>
 August 13, 2025

Mary Beth Dooley
Principal Executive Officer
Synlogic, Inc.
PO Box 30
Winchester, MA 01890

 Re: Synlogic, Inc.
 Registration Statement on Form S-3
 Filed August 8, 2025
 File No. 333-289415
Dear Mary Beth Dooley:

 This is to advise you that we have not reviewed and will not review your
registration
statement.

 Please refer to Rules 460 and 461 regarding requests for acceleration.
We remind you
that the company and its management are responsible for the accuracy and
adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action
by the staff.

 Please contact Doris Stacey Gama at 202-551-3188 with any questions.

 Sincerely,

 Division of
Corporation Finance
 Office of Life
Sciences
cc: Nishant Dharia, Esq.
</TEXT>
</DOCUMENT>

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 CHARDAN CAPITAL MARKETS, LLC

17 State Street, Suite 2130

 New
York, NY 10004

 September 26, 2023

 VIA EDGAR

 Securities and Exchange Commission

 Division of
Corporation Finance

 Office of Life Sciences

 100 F Street,
N.E.

 Washington, DC 20549

Re:
 Synlogic, Inc.

 Registration Statement on Form S-1, File
No. 333-274421

 REQUEST FOR ACCELERATION OF EFFECTIVENESS

Requested Date:         September 28, 2023

Requested Time:        5:00 p.m., Eastern Time

Ladies and Gentlemen:

 Pursuant to Rule 461
under the Securities Act of 1933, as amended (the “Securities Act”), the undersigned, as the underwriter of the proposed public offering of securities of Synlogic, Inc. (the “Company”), hereby join the Company’s request that
the effective date and time of the above-referenced registration statement on Form S-1 be accelerated so that it will be declared and become effective at 5:00 p.m., Eastern Time, on September 28, 2023, or
as soon thereafter as possible.

 The undersigned advises that it has complied and will continue to comply, with the requirements of Rule 15c2-8 under the Securities Exchange Act of 1934, as amended.

 Very truly yours,

CHARDAN CAPITAL MARKETS, LLC

By:

/s/ Shai Gerson

Name:

Shai Gerson

Title:

Managing Director

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 Synlogic, Inc.

301 Binney St., Suite 402

Cambridge, Massachusetts 02142

September 26, 2023

 VIA EDGAR

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 100 F Street, N.E.

 Washington, D.C. 20549

Attention: Cindy Polynice

Re:
 Synlogic, Inc.

 Registration Statement on Form S-1

 File No. 333-274421

 Request for Acceleration

Dear Ms. Polynice:

 Pursuant to Rule 461 of
Regulation C promulgated under the Securities Act of 1933, as amended, Synlogic, Inc. (the “Registrant”) hereby requests acceleration of the effective date of its Registration Statement on Form S-1
(File No. 333-274421), so that it may become effective at 5:00 p.m. (Washington, D.C. time) on September 28, 2023, or as soon thereafter as practicable.

Please call Daniel A. Bagliebter or Nishant M. Dharia of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., counsel to the Registrant, at
(212) 692-6856 or (212) 692-8174 with any comments or questions regarding this matter.

 Very truly yours,

Synlogic, Inc.

By:

/s/ Aoife Brennan MB, BCh, BAO, MMSc

Name: Aoife Brennan MB, BCh, BAO, MMSc

Title:   President and Chief Executive Officer

cc:
 Synlogic, Inc.

   Brendan St. Amant

 Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

     Daniel A. Bagliebter, Esq.

     Nishant M. Dharia, Esq.

United States securities and exchange commission logo
September 25, 2023
Michael Jensen
Chief Financial Officer
Synlogic, Inc.
301 Binney St., Suite 402
Cambridge, MA 02142
Re:Synlogic, Inc.
Form 10-K for the Fiscal Year Ended December 31, 2022
Filed March 29, 2023
File No. 001-37566
Dear Michael Jensen:
            We have completed our review of your filing.  We remind you that the company and its
management are responsible for the accuracy and adequacy of their disclosures, notwithstanding
any review, comments, action or absence of action by the staff.
Sincerely,
Division of Corporation Finance
Office of Life Sciences

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 September 20, 2023

CONFIDENTIAL – VIA EDGAR

 United States Securities
and Exchange Commission

 Division of Corporate Finance

Office of Life Sciences

 100 F Street, N.E.

Washington, D.C. 20549

 Attn: Vanessa Robertson

  Daniel Gordon

 Re: Synlogic,
Inc. Form 10-K for the fiscal year ended December 31, 2022

 Filed March 29, 2023

File No. 001-37566

Ladies and Gentlemen:

 On behalf of Synlogic, Inc. (the
“Company” or “Synlogic”), please find this letter in response to the comment letter, dated September 11, 2023, of the staff of the Division of Corporation Finance (the “Staff”) in reference to the Company’s
Annual Report on Form 10-K filed on March 29, 2023.

 In order to facilitate the Staff’s review, we have
repeated the comment in its entirety in italicized text followed by the Company’s response.

 Form 10-K for
the fiscal year ended December 31, 2022

 Management’s Discussion and Analysis of Financial Condition and Results of Operations

Financial Overview

 Research and Development Expense,
page 83

 Annual Report on Form 10-K

General

1.
 Please revise your future filings to break out the amounts incurred for internal research and development
expenses by nature or type of expense (i.e. employee related expenses) for each period presented.

Response: The Company acknowledges the Staff’s letter and confirms that it will revise its future filings to break out the
amounts incurred for internal research and development expenses by nature or type of expense (i.e. employee related expenses) for each period presented.

 301 Binney Street, Suite 402, Cambridge,
MA 02142 | www.synlogictx.com

 If you have any questions or comments in connection with this letter please contact the
undersigned by phone at (978) 269-7662 or via e-mail at Michael.jensen@synlogictx.com.

Sincerely,

 /s/ Michael Jensen

Michael Jensen

Chief Financial Officer

cc:
 Daniel Bagliebter, Esq., Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

Nishant Dharia, Esq., Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

 301 Binney Street, Suite 402, Cambridge,
MA 02142 | www.synlogictx.com

United States securities and exchange commission logo
September 14, 2023
Aoife Brennan
President, Chief Executive Officer and Director
SYNLOGIC, INC.
301 Binney Street, Suite 402
Cambridge, MA 02142
Re:SYNLOGIC, INC.
Registration Statement on Form S-1
Filed September 8, 2023
File No. 333-274421
Dear Aoife Brennan:
            This is to advise you that we have not reviewed and will not review your registration
statement.
            Please refer to Rules 460 and 461 regarding requests for acceleration.  We remind you
that the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
            Please contact Cindy Polynice at 202-551-8707 with any questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Nishant M. Dharia, Esq.

United States securities and exchange commission logo
September 11, 2023
Michael Jensen
Chief Financial Officer
Synlogic, Inc.
301 Binney St., Suite 402
Cambridge, MA 02142
Re:Synlogic, Inc.
Form 10-K for the fiscal year ended December 31, 2022
Filed March 29, 2023
File No. 001-37566
Dear Michael Jensen:
            We have limited our review of your filing to the financial statements and related
disclosures and have the following comment.  In our comment, we may ask you to provide us
with information so we may better understand your disclosure.
            Please respond to this comment within ten business days by providing the requested
information or advise us as soon as possible when you will respond.  If you do not believe our
comment applies to your facts and circumstances, please tell us why in your response.
            After reviewing your response to this comment, we may have additional comments.
Form 10-K for the fiscal year ended December 31, 2022
Management's Discussion and Analysis of Financial Condition and Results of Operations
Financial Overview
Research and Development Expense, page 83
1.Please revise your future filings to break out the amounts incurred for Internal research
and development expenses by nature or type of expense (i.e. employee related
expenses) for each period presented.
            In closing, we remind you that the company and its management are responsible for the
accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or
absence of action by the staff.
            You may contact Vanessa Robertson at 202-551-3649 or Daniel Gordon at 202-551-3486
with any questions.

 FirstName LastNameMichael Jensen
 Comapany NameSynlogic, Inc.
 September 11, 2023 Page 2
 FirstName LastName
Michael Jensen
Synlogic, Inc.
September 11, 2023
Page 2
Sincerely,
Division of Corporation Finance
Office of Life Sciences

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 SYNLOGIC, INC.

301 Binney Street, Suite 402

Cambridge, Massachusetts 02142

July 29, 2021

 VIA EDGAR

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 100 F Street, N.E.

 Washington, D.C. 20549

Attention: Ms. Abby Adams

Re:
 Synlogic, Inc.

Registration Statement on Form S-3

Filed July 23, 2021

File No. 333- 258151 (the “Registration Statement”)

Acceleration Request

 Ladies and
Gentlemen:

 In accordance with Rule 461 of Regulation C promulgated under the Securities Act of 1933, as amended, Synlogic, Inc. (the
“Registrant”) hereby respectfully requests that the Securities and Exchange Commission accelerate the effective date of the above-referenced Registration Statement to Friday, July 30, 2021, at 4:01 p.m., Eastern Time, or as soon as
thereafter practicable.

 The cooperation of the staff in meeting the timetable described above is very much appreciated.

Please contact Daniel A. Bagliebter of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., counsel to the Registrant, at (212) 692-6856 with any questions regarding this request.

Very truly yours,

SYNLOGIC, INC.

 /s/ Gregg Beloff

 Gregg Beloff

 Interim Chief Financial
Officer

cc:
 Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

 Matthew J. Gardella, Esq.

Daniel A. Bagliebter, Esq.

United States securities and exchange commission logo
July 28, 2021
Aiofe M. Brennen, MB,BCh,BAO,MMSc
Chief Executive Officer
Synlogic, Inc.
301 Binney St., Suite 402
Cambridge, Massachusetts 02142
Re:Synlogic, Inc.
Registration Statement on Form S-3d
Filed July 23, 2021
File No. 333-258151
Dear Dr. Brennen:
            This is to advise you that we have not reviewed and will not review your registration
statement.
            Please refer to Rules 460 and 461 regarding requests for acceleration.  We remind you
that the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
            Please contact Abby Adams at (202) 551-6902 with any questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Daniel Bagliebter, Esq.

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 SYNLOGIC, INC.

301 Binney Street, Suite 402

Cambridge, Massachusetts 02142

September 11, 2019

 VIA EDGAR

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 100 F Street, N.E.

 Washington, D.C. 20549

Attention: Ms. Tonya K. Aldave

                 Mr. Justin Dobbie

Re:
 Synlogic, Inc.

 Registration Statement on Form S-3

 Filed August 8, 2019, as amended on August 30, 2019

 File No. 333-233139 (the “Registration Statement”)

 Acceleration Request

Ladies and Gentlemen:

 In accordance with Rule 461 of Regulation
C promulgated under the Securities Act of 1933, as amended, Synlogic, Inc. (the “Registrant”) hereby respectfully requests that the Securities and Exchange Commission accelerate the effective date of the above-referenced Registration
Statement to Friday, September 13, 2019, at 4:00 p.m., Eastern Time, or as soon as thereafter practicable.

 The cooperation of the staff in meeting
the timetable described above is very much appreciated.

 Please contact Matthew J. Gardella of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.,
counsel to the Registrant, at (617) 348-1735 with any questions regarding this request.

Very truly yours,

SYNLOGIC, INC.

/s/ Todd Shegog

 Todd Shegog

 Chief Financial Officer and
Treasurer

cc:
 Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

 Matthew J. Gardella, Esq.

 Daniel A. Bagliebter, Esq.

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 One Financial Center

Boston, MA 02111

 617 542 6000

mintz.com

 August 30, 2019

 VIA
EDGAR & OVERNIGHT MAIL

 Securities and Exchange Commission

Division of Corporation Finance

 100 F Street, N.E. Washington,
D.C. 20549

 Attention: Tonya K. Aldave, Office of Healthcare & Insurance

Re:
 Synlogic, Inc.

Registration Statement on Form S-3

Filed August 8, 2019

File No. 333-233139

Ladies and Gentlemen:

 We are submitting this letter on behalf
of Synlogic, Inc. (the “Company”) in response to comments from the staff (the “Staff”) of the Securities and Exchange Commission (the “Commission”) received by letter dated August 20, 2019 from the Division of
Corporation Finance, Office of Healthcare & Insurance, to Aoife M. Brennan, President, Chief Executive Officer and Chief Medical Officer of the Company, relating to the above-referenced Registration Statement. In conjunction with this
letter, the Company is filing Amendment No. 1 to the Registration Statement (the “Amended Registration Statement”) with the Commission.

For convenient reference, we have reproduced below the Staff’s comment and the Company’s response is below it. This response is based on information
provided to Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. by representatives of the Company. As indicated below, the Company has responded to the Staff’s comment by making changes to the disclosure in the Amended Registration Statement
and future periodic filings.

 Registration Statement on Form S-3

General

 Comment 1: We note that your forum
selection provision identifies the Court of Chancery of the State of Delaware as the exclusive forum for certain litigation, including any “derivative action.” Please describe this provision and disclose whether this provision applies to
actions arising under the Securities Act or Exchange Act. In that regard, we note that Section 27 of the Exchange Act creates exclusive federal jurisdiction over all suits brought to enforce any duty or liability created by the Exchange Act or
the rules and regulations thereunder, and Section 22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all suits brought to enforce any duty or liability created by the Securities Act or the rules and
regulations thereunder. If the provision applies to Securities Act claims, please also revise your prospectus to state that there is uncertainty as to whether a court would enforce such provision and that investors cannot waive compliance with the
federal securities laws and the rules and regulations

BOSTON        LONDON        LOS
ANGELES        NEW YORK        SAN DIEGO        SAN FRANCISCO        WASHINGTON

MINTZ, LEVIN, COHN, FERRIS, GLOVSKY AND POPEO, P.C.

 August 30, 2019

Page 2

 thereunder. If this provision does not apply to actions
arising under the Securities Act or Exchange Act, please also tell us how you will inform investors in future filings that the provision does not apply to any actions arising under the Securities Act or Exchange Act.

Response 1: In response to the Staff’s comment, the Company has amended the Risk Factors section of the Amended Registration Statement on page
4. In addition to those risk factors incorporated by reference, the Risk Factors section in the Amended Registration Statement now physically includes the risk factor below It is a revised version of the Company’s existing risk factor on
this topic from its periodic reports. (For your ease of reference, the revisions are emphasized below by italicized text). As revised, we believe it addresses the Staff’s comment. Starting with its next Form 10-Q, the Company will also prospectively include this revised disclosure in the risk factor sections of its future quarterly and annual reports.

“Provisions of our charter documents or Delaware law could delay or prevent an acquisition of us, even if the acquisition would be
beneficial to our stockholders, and could make it more difficult for you to change management.

 Provisions in our
amended and restated certificate of incorporation and our amended and restated bylaws may discourage, delay or prevent a merger, acquisition or other change in control that our stockholders may consider favorable, including transactions in which our
stockholders might otherwise receive a premium for their shares. In addition, these provisions may frustrate or prevent any attempt by our stockholders to replace or remove our current management by making it more difficult to replace or remove our
Board of Directors. These provisions include:

•

 a classified board of directors so that not all directors are elected at one time;

•

 a prohibition on stockholder action through written consent;

•

 no cumulative voting in the election of directors;

•

 the exclusive right of our Board of Directors to elect a director to fill a vacancy created by the expansion of
our Board of Directors or the resignation, death or removal of a director;

•

 a requirement that special meetings of our Stockholders be called only by our Board of Directors, the chairman of
our Board of Directors, the chief executive officer or, in the absence of a chief executive officer, the president;

•

 an advance notice requirement for stockholder proposals and nominations;

•

 the authority of our Board of Directors to issue preferred stock with such terms as our Board of Directors may
determine; and

•

 a requirement of approval of not less than 66 2/3% of all outstanding shares of our capital stock entitled to
vote to amend any bylaws by stockholder action, or to amend specific provisions of our certificate of incorporation.

 In
addition, Delaware law prohibits a publicly held Delaware corporation from engaging in a business combination with an interested stockholder, generally a person who, together with its affiliates, owns or within the last three years has owned 15% or
more of the company’s voting stock, for a period of three years after the date of the transaction in which the person became an interested stockholder, unless the business combination is approved in a prescribed manner. Accordingly, Delaware
law may discourage delay or prevent a change in control of the company.

 In addition, our amended and restated certificate of
incorporation, to the fullest extent permitted by law, provides that the Court of Chancery of the State of Delaware will be the exclusive forum for: any derivative action or proceeding brought on our behalf; any action asserting a breach of

 August 30, 2019

Page 3

 fiduciary duty; any action asserting
a claim against us arising pursuant to the Delaware General Corporation Law, or the DGCL, our amended and restated certificate of incorporation, or our amended and restated bylaws; or any action asserting a claim against us that is governed by the
internal affairs doctrine. This exclusive forum provision does not apply to suits brought to enforce a duty or liability created by the Exchange Act. It could apply, however, to a suit that falls within one or more of the categories enumerated in
the exclusive forum provision and asserts claims under the Securities Act, inasmuch as Section 22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all suits brought to enforce any duty or liability created
by the Securities Act or the rule and regulations thereunder. There is uncertainty as to whether a court would enforce such provision with respect to claims under the Securities Act, and our stockholders will not be deemed to have waived our
compliance with the federal securities laws and the rules and regulations thereunder.

 This choice of forum provision may limit a
stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or any of our directors, officers, or other employees, which may discourage lawsuits with respect to such claims. Alternatively, if a court
were to find the choice of forum provisions contained in our restated certificate of incorporation to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which
could harm our business, results of operations and financial condition.

 Provisions in our charter and other provisions of Delaware law
could limit the price that investors are willing to pay in the future for shares of our common stock.”

*    *    *    *    *

We hope that the above responses and the related revisions reflected in the Amended Registration Statement will be acceptable to the Staff. Please do not
hesitate to contact me at (617) 348-1735 or MJGardella@mintz.com with any comments or questions regarding the Amended Registration Statement and this letter. We thank you for your time and attention.

Sincerely,

/s/ Matthew J. Gardella

Matthew J. Gardella

cc:
 Securities and Exchange Commission

Justin Dobbie

 Synlogic,
Inc.

 Maiken Keson-Brookes, General Counsel

Aoife M. Brennan, President, Chief Executive Officer and Chief Medical Officer

Todd Shegog, Chief Financial Officer

Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

Lewis J. Geffen

 Daniel A.
Bagliebter

August 20, 2019
Aoife Brennan
Chief Executive Officer
Synlogic, Inc.
301 Binney St., Suite 402
Cambridge, MA 02142
Re:Synlogic, Inc.
Registration Statement on Form S-3
Filed August 8, 2019
File No. 333-233139
Dear Dr. Brennan:
            We have limited our review of your registration statement to those issues we have
addressed in our comments.  In some of our comments, we may ask you to provide us with
information so we may better understand your disclosure.
            Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
            After reviewing any amendment to your registration statement and the information you
provide in response to these comments, we may have additional comments.
Registration Statement on Form S-3
General
1.We note that your forum selection provision identifies the Court of Chancery of the
State of Delaware as the exclusive forum for certain litigation, including any
“derivative action.”  Please describe this provision and disclose whether this provision
applies to actions arising under the Securities Act or Exchange Act.  In that regard, we
note that Section 27 of the Exchange Act creates exclusive federal jurisdiction over all
suits brought to enforce any duty or liability created by the Exchange Act or the rules and
regulations thereunder, and Section 22 of the Securities Act creates concurrent jurisdiction
for federal and state courts over all suits brought to enforce any duty or liability created by
the Securities Act or the rules and regulations thereunder.  If the provision applies to
Securities Act claims, please also revise your prospectus to state that there is uncertainty

 FirstName LastNameAoife Brennan
 Comapany NameSynlogic, Inc.
 August 20, 2019 Page 2
 FirstName LastName
Aoife Brennan
Synlogic, Inc.
August 20, 2019
Page 2
as to whether a court would enforce such provision and that investors cannot waive
compliance with the federal securities laws and the rules and regulations thereunder.  If
this provision does not apply to actions arising under the Securities Act or Exchange Act,
please also tell us how you will inform investors in future filings that the provision does
not apply to any actions arising under the Securities Act or Exchange Act.
            We remind you that the company and its management are responsible for the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action or absence of
action by the staff.
            Refer to Rules 460 and 461 regarding requests for acceleration.  Please allow adequate
time for us to review any amendment prior to the requested effective date of the registration
statement.
            Please contact Tonya K. Aldave at (202) 551-3601 or Justin Dobbie, Legal Branch Chief,
at (202) 551-3469 with any questions.
Sincerely,
Division of Corporation Finance
Office of Healthcare & Insurance
cc:       Daniel Bagliebter, Esq.

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 SYNLOGIC, INC.

301 Binney Street, Suite 402

Cambridge, Massachusetts 02142

August 28, 2018

 VIA EDGAR

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 100 F Street, N.E.

 Washington, D.C. 20549

Attention:
 Ms. Mary Beth Breslin

 Ms. Irene Paik

Re:
 Synlogic, Inc.

 Registration Statement on Form S-3

 Filed August 9, 2018, as amended on August 23, 2018

 File No. 333-226730 (the “Registration Statement”)

 Acceleration Request

Ladies and Gentlemen:

 In accordance with Rule 461 of
Regulation C promulgated under the Securities Act of 1933, as amended, Synlogic, Inc. (the “Registrant”) hereby respectfully requests that the Securities and Exchange Commission accelerate the effective date of the above-referenced
Registration Statement to Thursday, August 30, 2018, at 4:00 p.m., Eastern Time, or as soon as thereafter practicable.

 The Registrant hereby
authorizes Matthew J. Gardella of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., counsel to the Registrant, to orally modify or withdraw this request for acceleration on its behalf. The Registrant hereby acknowledges its responsibilities
under the Securities Act of 1933, as amended, and the Securities Exchange Act of 1934, as amended, as they relate to the proposed public offering of the securities specified in the Registration Statement.

The cooperation of the staff in meeting the timetable described above is very much appreciated.

Please contact Matthew J. Gardella of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. at (617) 348-1735 with
any questions regarding this request.

 Very truly yours,

SYNLOGIC, INC.

/s/ Aoife M. Brennan

 Aoife M. Brennan

 Interim President, Chief
Executive Officer and Chief Medical Officer

cc:
 Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

 Matthew J. Gardella, Esq.

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 One Financial Center

Boston, MA 02111

 617 542 6000

617 542 2241 fax

www.mintz.com

 August 23, 2018

 VIA EDGAR

 U.S. Securities and Exchange Commission

Division of Corporation Finance

 100 F Street, N.E. Washington,
D.C. 20549

 Attention: Irene Paik

 Re: Synlogic, Inc.

 Registration Statement on Form S-3

Filed August 9, 2018

 File No. 333-226730 (the “Registration Statement”)

 Dear Ms. Paik:

We are submitting this letter on behalf of Synlogic, Inc. (the “Company”) in response to comments from the staff (the “Staff”) of the
Securities and Exchange Commission (the “Commission”) received by letter dated August 17, 2018 (the “Comment Letter”) from the Division of Corporation Finance, Office of Healthcare and Insurance, to Aoife M. Brennan, Interim
President and Chief Executive Officer of the Company, relating to the above-referenced Registration Statement. In conjunction with this letter, the Company is filing Amendment No. 1 to the Registration Statement (the “Amended Registration
Statement”) with the Commission.

 For convenient reference, we have set forth below in italics each of the Staff’s comments set forth in the
Comment Letter and have keyed the Company’s responses to the numbering of the comments and the headings used in the Comment Letter. All of the responses are based on information provided to Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. by
representatives of the Company. Where appropriate, the Company has responded to the Staff’s comments by making changes to the disclosure in the Amended Registration Statement. Page numbers referred to in the responses reference the applicable
pages of the Amended Registration Statement.

 Mintz, Levin,
Cohn, Ferris, Glovsky and Popeo, P.C.

 BOSTON | LONDON | LOS ANGELES |
NEW YORK | SAN DIEGO | SAN FRANCISCO | STAMFORD | WASHINGTON

 August 23, 2018

 Page
 2

 Description of Purchase Contracts, page 22

Comment 1: We note your disclosure that you may issue purchase contracts for the purchase or sale of securities that may consist of securities of
third parties. Please advise us how you anticipate conducting such offerings under the registration and disclosure requirements of the Securities Act. For example, please advise us of the disclosure you will provide in the applicable prospectus
supplement or other offering materials, including, as necessary, any required financial statement and non-financial statement disclosure about the issuer of such securities. For guidance, please refer to the
Morgan Stanley & Co., Inc. no action letter (June 24, 1996) and Securities Act Sections Compliance and Disclosure Interpretation 203.03.

Response 1: The Company acknowledges the Staff’s comment and confirms that it does not wish to offer any third party securities underlying
purchase contracts. The Company has revised the Registration Statement to remove references to such third party securities. Please see the revised disclosure on page 22 of the Amended Registration Statement.

Comment 2: It is not clear how the purchase contracts you propose to issue should be characterized for purposes of the federal securities laws. For
example, the disclosure in the filing indicates that these contracts obligate you to purchase from holders, and obligate holders to sell to you, securities at a purchase price that may be fixed or may be determined by a specific formula. The
disclosure in the filing also indicates that these contracts may require you to make periodic payments to the holders or for holders to make periodic payments to you. Furthermore, the disclosure indicates that you may purchase contracts separately
or as part of units each consisting of a purchase contract and one or more securities, including U.S. Treasury securities. Finally, the disclosure in the filing indicates that these contracts may require the holders of the contracts to secure their
obligations in a specified manner. Based on this disclosure it appears that these contracts may have characteristics associated with forwards, options and security-based swaps. Please provide us with your legal analysis as to how these contracts
should be appropriately characterized under the federal securities laws.

 Response 2: In response to the Staff’s comment, the Company has
revised the Registration Statement to seek to register purchase contracts with respect to the future delivery of equity securities of the Company under the Registration Statement. As a result, the Company respectfully submits that the purchase
contracts are properly characterized as “investment contracts” as that term is used in Section 2(a)(1) of the Securities Act.

 The Company
has also revised the Registration Statement to, among other things, clarify that any purchase contracts the Company issues will be physically settled by delivery of the equity securities. Accordingly, such purchase contracts should be properly
excluded from the definition of “swap” under Section 1a(47)(B) of the Commodity Exchange Act and from the definition of “security-based swap” under Section 2(a)(17) of the Securities Act, Section 1a(42) of the
Commodity Exchange Act and Section 3(a)(68) of the Securities Exchange Act of 1934, as amended. Please see the revised disclosure on page 22 of the Amended Registration Statement.

 August 23, 2018

 Page
 3

 Comment 3: We note the reference to “other property” that may be included in the purchase
contracts. Please revise your disclosure to specify what other property may be included in the purchase contracts.

 Response 3: In response to
the Staff’s comment, the Company has removed from the Registration Statement references to “other property” that may be included in the purchase contracts. Please see the revised disclosure on page 22 of the Amended Registration
Statement.

*        *        *
 *        *

 We hope that the above responses and the related revisions reflected in the Amended Registration
Statement will be acceptable to the Staff. Please do not hesitate to contact me at (617) 348-1735 or MJGardella@mintz.com with any comments or questions regarding the Amended Registration Statement and
this letter. We thank you for your time and attention.

 Sincerely,

/s/ Matthew J. Gardella

 Matthew J. Gardella

cc:
 Securities and Exchange Commission

Mary Beth Breslin

Synlogic, Inc.

Aoife M. Brennan, Interim President and Chief Executive Officer

Todd Shegog, Chief Financial Officer

Maiken Keson-Brookes, General Counsel

August 17, 2018
Aiofe M. Brennan
Interim President and Chief Executive Officer
Synlogic, Inc.
301 Binney St., Suite 402
Cambridge, Massachusetts 02142
Re:Synlogic, Inc.
Registration Statement on Form S-3
Filed August 9, 2018
File No. 333-226730
Dear Dr. Brennan:
            We have limited our review of your registration statement to those issues we have
addressed in our comments.  In some of our comments, we may ask you to provide us with
information so we may better understand your disclosure.
            Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
            After reviewing any amendment to your registration statement and the information you
provide in response to these comments, we may have additional comments.
Registration Statement on Form S-3 filed August 9, 2018
Description of Purchase Contracts, page 22
1.We note your disclosure that you may issue purchase contracts for the purchase or sale
of securities that may consist of securities of third parties.  Please advise us how
you anticipate conducting such offerings under the registration and disclosure
requirements of the Securities Act.  For example, please advise us of the disclosure you
will provide in the applicable prospectus supplement or other offering materials,
including, as necessary, any required financial statement and non-financial statement
disclosure about the issuer of such securities.  For guidance, please refer to the Morgan

 FirstName LastNameAiofe M. Brennan
 Comapany NameSynlogic, Inc.
 August 17, 2018 Page 2
 FirstName LastName
Aiofe M. Brennan
Synlogic, Inc.
August 17, 2018
Page 2
Stanley & Co., Inc. no action letter (June 24, 1996) and Securities Act Sections
Compliance and Disclosure Interpretation 203.03.
2.It is not clear how the purchase contracts you propose to issue should be characterized
for purposes of the federal securities laws.  For example, the disclosure in the filing
indicates that these contracts obligate you to purchase from holders, and obligate holders
to sell to you, securities at a purchase price that may be fixed or may be determined by a
specific formula.  The disclosure in the filing also indicates that these contracts may
require you to make periodic payments to the holders or for holders to make periodic
payments to you.  Furthermore, the disclosure indicates that you may purchase contracts
separately or as part of units each consisting of a purchase contract and one or more
securities, including U.S. Treasury securities.  Finally, the disclosure in the filing indicates
that these contracts may require the holders of the contracts to secure their obligations in a
specified manner.  Based on this disclosure it appears that these contracts may have
characteristics associated with forwards, options and security-based swaps.  Please
provide us with your legal analysis as to how these contracts should be appropriately
characterized under the federal securities laws.
3.We note the reference to "other property" that may be included in the purchase
contracts.  Please revise your disclosure to specify what other property may be included in
the purchase contracts.
            We remind you that the company and its management are responsible for the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action or absence of
action by the staff.
            Refer to Rules 460 and 461 regarding requests for acceleration.  Please allow adequate
time for us to review any amendment prior to the requested effective date of the registration
statement.
            Please contact Irene Paik at 202-551-6553 or Mary Beth Breslin at 202-551-3625 with
any questions.
Sincerely,
Division of Corporation Finance
Office of Healthcare & Insurance
cc:       Matthew J. Gardella, Esq.

CORRESP
1
filename1.htm

CORRESP

 Synlogic, Inc.

200 Sidney Street, Suite 320

Cambridge, Massachusetts 02139

October 23, 2017

 VIA EDGAR

United States Securities and Exchange Commission

 Division of
Corporation Finance

 100 F Street, N.E.

 Washington, D.C.
20549

RE:
Synlogic, Inc.

 Registration Statement on Form
S-3

 File No. 333-220948

Acceleration Request

 Ladies and
Gentlemen:

 With respect to the above-referenced Registration Statement on Form S-3 (the
“Registration Statement”), and pursuant to Rule 461 of Regulation C promulgated under the Securities Act of 1933, as amended, the undersigned hereby respectfully requests, on behalf of Synlogic, Inc. (the “Company”), that the
Securities and Exchange Commission accelerate the effective date of the Registration Statement to Wednesday October 25, 2017, at 4:00 p.m. Eastern Time, or as soon as practicable thereafter.

The cooperation of the staff in meeting the timetable described above is very much appreciated.

Please call Matthew J. Gardella of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., counsel to the Company, at (617) 542-6000, with any comments or questions regarding the Registration Statement.

 Very truly yours,

SYNLOGIC, INC.

/s/ Todd Shegog

 Todd Shegog

 Chief Financial
Officer

cc:
Christine Westbrook, Securities and Exchange Commission

 Jose Carlos Gutierrez-Ramos.,
President and Chief Executive Officer, Synlogic, Inc.

 Matthew J. Gardella, Esq., Mintz, Levin, Cohn, Ferris, Glovsky and Popeo,
P.C.

 Lewis J. Geffen, Esq., Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

October 23, 2017
Carlos Gutierrez-Ramos
President and Chief Executive Officer
Synlogic, Inc.
200 Sidney Street, Suite 320
Cambridge, MA 02139
Synlogic, Inc.
Registration Statement on Form S-3
Filed October 13, 2017
File No. 333-220948Re:
Dear Dr. Gutierrez-Ramos:
            This is to advise you that we have not reviewed and will not review your registration
statement.
            Please refer to Rules 460 and 461 regarding requests for acceleration.  We remind you that
the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
            Please contact Christine Westbrook at (202) 551-5019 with any questions.
Division of Corporation Finance
Office of Healthcare & Insurance
cc: Matthew Gardella, Esq.

CORRESP
1
filename1.htm

Acceleration Request

 Mirna Therapeutics, Inc.

1250 South Capital of Texas Highway

Building 3, Suite 400

 Austin,
Texas 78746

 July 11, 2017

 VIA EDGAR

 Securities and Exchange Commission

 Division of
Corporation Finance

 100 F Street, N.E.

 Washington, D.C.
20549-6010

Re:
Mirna Therapeutics, Inc. Registration Statement on Form S-4 (File No. 333-218885)

Request for Acceleration of Effectiveness

Requested Date: July 13, 2017

Requested Time: 4:00 p.m. Washington, D.C. time

Ladies and Gentlemen:

 In accordance with Rule
461 promulgated under the Securities Act of 1933, as amended, Mirna Therapeutics, Inc. (the “Registrant”) hereby requests acceleration of the effective date of the Registration Statement on Form S-4 (File No. 333-218885), as
amended (the “Registration Statement”), so that it may become effective at 4:00 p.m. Washington, D.C. time on July 13, 2017, or as soon as possible thereafter.

The Registrant hereby authorizes Chad Rolston, of Latham & Watkins LLP, to orally modify or withdraw this request for acceleration.

 The Registrant hereby acknowledges that:

•

should the Securities and Exchange Commission (the “Commission”) or the staff of the Division of Corporation Finance (the “Staff”), acting pursuant to delegated authority, declare the
filing effective, it does not foreclose the Commission from taking any action with respect to the filing;

•

the action of the Commission or the Staff, acting pursuant to delegated authority, in declaring the filing effective, does not relieve the Registrant from its full responsibility for the adequacy and accuracy of the
disclosure in the filing; and

•

the Registrant may not assert Staff comments and the declaration of effectiveness as a defense in any proceeding initiated by the Commission or any person under the federal securities laws of the United States.

 We request that we be notified of such effectiveness by a telephone call to Mr. Rolston at (650) 463-3079, or in
his absence Bret Stancil, of Latham & Watkins LLP, at (650) 463-3087. We also respectfully request that a copy of the written order from the Commission verifying the effective time and date of such Registration Statement be sent to
Latham & Watkins LLP, attention: Chad Rolston, via facsimile at (650) 463-2600.

 Very truly yours,

Mirna Therapeutics, Inc.

/s/ Paul
Lammers

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

President and Chief Executive Officer

cc:
Mark Roeder, Latham & Watkins LLP

 Chad Rolston, Latham & Watkins LLP

Bret Stancil, Latham & Watkins LLP

Matt Gardella, Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

June 30, 2017
Paul  Lammers
President & Chief Executive Officer
Mirna Therapeutics, Inc.
1250 South Capital of Texas Highway
Building 3, Suite 400
Austin, TX 78746
Mirna Therapeutics, Inc.
Registration Statement on Form S-4
Filed June 21, 2017
File No. 333-218885Re:
Dear Dr. Lammers:
        This is to advise you that we have not reviewed and will not review your registration
statement.
        Please refer to Rules 460 and 461 regarding requests for acceleration.  We remind you
that the company and its management are responsible for the accuracy and adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action by the staff.
        Please contact Jeffrey Gabor at (202) 551-2544 with any questions.
Division of Corporation Finance
Office of Healthcare & Insurance

CORRESP
1
filename1.htm

Mirna Therapeutics, Inc.
 2150 Woodward Street, Suite 100
 Austin, TX 78744

September 25, 2015

VIA EDGAR AND E-MAIL

United States Securities and Exchange Commission
 Division of Corporation Finance
  100 F Street, N.E.
 Washington, D.C. 20549-6010

Attention:

Jeffrey P. Riedler,   Assistant Director

Tara Keating Brooks

Bryan Pitko

Sasha Parikh

Jim Rosenberg

Re:

Mirna Therapeutics, Inc.   Registration Statement on Form S-1 (Registration No. 333-206544)

Ladies and Gentlemen:

In accordance with Rule 461 of Regulation C of the General Rules and Regulations under the Securities Act of 1933, as amended, we hereby request acceleration of the effective date of the Registration Statement on Form S-1 (File No. 333-206544) (the “Registration Statement”) of Mirna Therapeutics, Inc. (the “Company”).  We respectfully request that the Registration Statement become effective as of 4:00 p.m., Washington, D.C. time, on September 29, 2015, or as soon as practicable thereafter.  Once the Registration Statement has been declared effective, please orally confirm that event with our counsel, Latham & Watkins LLP, by calling Mark Roeder at (650) 463-3043.

The Company acknowledges the following:

·                              should the Securities and Exchange Commission (the “Commission”) or the staff, acting pursuant to delegated authority, declare the filing effective, it does not foreclose the Commission from taking any action with respect to the filing;

·                              the action of the Commission or the staff, acting pursuant to delegated authority in declaring the filing effective, does not relieve the Company from its full responsibility for the adequacy and accuracy of the disclosure in the filing; and

·                              the Company may not assert staff comments and the declaration of effectiveness as a defense in any proceeding initiated by the Commission or any person under the federal securities laws of the United States.

Thank you for your assistance in this matter.

Very truly yours,

MIRNA THERAPEUTICS, INC.

By:

/s/ Paul Lammers

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

President and Chief   Executive Officer

CC:

Alan Fuhrman, Mirna   Therapeutics, Inc.

Jon Irvin, Mirna   Therapeutics, Inc.

Alan C.   Mendelson, Esq., Latham & Watkins LLP

Mark V.   Roeder, Esq., Latham & Watkins LLP

Thomas   Holden, Esq., Ropes & Gray LLP

September 25, 2015

Securities and Exchange Commission

100 F Street, N.E.

Washington, D.C.  20549

Re:                             Mirna Therapeutics, Inc.

Registration Statement on Form S-1 (SEC File No. 333-206544) (the “Registration Statement”)

Ladies and Gentlemen:

In connection with the above-referenced Registration Statement, and pursuant to Rule 461 under the Securities Act of 1933, as amended (the “Act”), we hereby join in the request of Mirna Therapeutics, Inc. that the effective date of the Registration Statement be accelerated so that it will be declared effective at 4:00 p.m., Washington, D.C. time, on September 29, 2015 or as soon thereafter as practicable.

Pursuant to Rule 460 under the Act, we wish to advise you that we have distributed approximately 1,687 copies of the preliminary prospectus dated September 18, 2015 (the “Preliminary Prospectus”) through the date hereof, to underwriters, dealers, institutions and others.

In connection with the Preliminary Prospectus distribution for the above-referenced issue, the prospective underwriters have confirmed that they are complying with the 48-hour requirement as promulgated by Rule 15c2-8 under the Securities Exchange Act of 1934, as amended.

Very truly yours,

Citigroup Global Markets Inc.

Leerink Partners LLC

For themselves and as representatives of the several underwriters

By:

CITIGROUP GLOBAL MARKETS INC.

By:

/s/ Jennifer Jarrett

Name: Jennifer Jarrett

Title: Managing Director

By:

LEERINK PARTNERS LLC

By:

/s/ John I. Fitzgerald, Esq.

Name: John I. Fitzgerald, Esq.

Title: Managing Director

[Signature Page to Mirna Therapeutics, Inc. S-1 Acceleration Request]

CORRESP
1
filename1.htm

[***] CERTAIN INFORMATION IN THIS DOCUMENT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTION.

140 Scott Drive

Menlo Park, California 94025

Tel:   +1.650.328.4600  Fax: +1.650.463.2600

www.lw.com

FIRM   / AFFILIATE OFFICES

Abu Dhabi

Milan

Barcelona

Moscow

Beijing

Munich

Boston

New Jersey

September 2,   2015

Brussels

New York

Century City

Orange County

Chicago

Paris

Dubai

Riyadh

Düsseldorf

Rome

Frankfurt

San Diego

Hamburg

San Francisco

Hong Kong

Shanghai

Houston

Silicon Valley

London

Singapore

Los Angeles

Tokyo

Madrid

Washington, D.C.

VIA EDGAR AND HAND DELIVERY

File No. 054663-0010

United States Securities and Exchange Commission

Division of Corporation Finance

100 F Street, N.E.

Washington, D.C. 20549-6010

Attention:

Jeffrey P. Riedler, Assistant Director

FOIA Confidential Treatment
   Requested Under 17 C.F.R. § 200.83

Tara Keating   Brooks

Bryan Pitko

Sasha Parikh

Jim Rosenberg

Re:

Mirna Therapeutics, Inc.

Stock-Based Compensation

Registration Statement on   Form S-1 (File No. 333-206544)

Ladies and Gentlemen:

On behalf of Mirna Therapeutics, Inc. (the “Company” or “Mirna”), we submit this letter (this “Letter”) to the staff (the “Staff”) of the Securities and Exchange Commission (the “Commission”).  The Company originally filed the above-referenced Registration Statement on Form S-1 (the “Registration Statement”) with the Commission on August 24, 2015.

The purpose of this Letter is to provide supplemental information to the Staff with respect to the accounting treatment for stock-based compensation for its consideration during the review cycle so that the Company may be in a position to print a preliminary prospectus as promptly as practicable.  We are respectfully requesting confidential treatment for certain portions of this Letter pursuant to Rule 83 promulgated by the Commission, 17 C.F.R. §200.83.  This Letter is accompanied by such request for confidential treatment because of the commercially sensitive

September 2, 2015

Page 2

nature of the information discussed in this Letter.  A redacted letter will be filed on EDGAR, omitting the confidential information contained in this Letter.

The Company’s discussion of stock-based compensation is primarily contained within the section of the Registration Statement entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Critical Accounting Policies and Estimates—Stock-Based Compensation” (the “MD&A”) and Note 2, Summary of Significant Accounting Policies in the Financial Statements included in the Registration Statement (the “Financial Notes”) and appears on pages 79, 80 and F-8 through F-10 of the Registration Statement.

The Company supplementally advises the Staff that, while not reflected in the Registration Statement, based on discussions with the Company’s Board of Directors and reflecting the input from the lead underwriters for its initial public offering (the “IPO”), the Company currently anticipates an approximate price range of $[***] to $[***] per share for the Company’s common stock (the “Preliminary IPO Price Range”), with a midpoint of the anticipated range of approximately $[***] per share (the “Preliminary Assumed IPO Price”).  The Preliminary IPO Price Range and Preliminary Assumed IPO Price do not reflect any stock split that the Company might effect prior to the Commission’s declaration of effectiveness of the Registration Statement.  The Company currently anticipates implementing an approximate [***] to [***] reverse stock split, which would result in a post-split Preliminary IPO Price Range of $[***] to $[***] per share, with a midpoint of $[***] per share.  For consistency with the Registration Statement, all data in this letter is reflected on a pre-split basis.

The Company’s final post-split Preliminary IPO Price Range remains under discussion between the Company and the lead underwriters, and a bona fide price range will be included in an amendment to the Registration Statement prior to any distribution of the preliminary prospectus in connection with the Company’s road show.

As set forth in the MD&A on page 80 of the Registration Statement, the Company recorded stock-based compensation expense related to options granted of $0.2 million and $0.4 million in the years ended December 31, 2013 and 2014, and $0.4 million for the six months ended June 30, 2015, respectively. On a percentage basis, the recorded stock-based compensation expense for the year ended December 31, 2014 and six months ended June 30, 2015 represents approximately 2.6% and 3.5% of total net loss for those periods, respectively.

STOCK OPTION GRANTS IN PRECEDING 12 MONTHS

The following table summarizes by grant date the number of shares of common stock underlying stock options granted during the twelve months preceding, and the period subsequent to, the most recent balance sheet date included in the Registration Statement, as well as the associated per share exercise price and the estimated fair value per share of the Company’s common stock to determine stock-based compensation expense for financial reporting purposes:

Option Grant Dates

Number of Shares
   Underlying Options

Exercise Price
   Per Share

Fair Value — Financial
   Reporting Purposes

November 5,   2014

256,000

$

0.52

$

0.52

March 1,   2015

964,000

$

0.41

$

0.41

June 4,   2015

3,957,750

$

0.43

$

0.43

[***] CERTAIN INFORMATION IN THIS DOCUMENT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTION.

September 2, 2015

Page 3

ANTICIPATED ACTIONS

The Company currently anticipates that the final Preliminary IPO Price Range (and related stock split) will be finalized and approved by the Company’s Board of Directors on or about September 8, 2015.

The remainder of this letter will outline the Company’s historical fair value determination practice and methodologies, as well as provide an explanation as between the difference between the Preliminary Assumed IPO Price and the fair value determination with respect to the option awards granted in early June 2015.

HISTORICAL FAIR VALUE DETERMINATION AND METHODOLOGY

As previously disclosed, the Company has historically determined the fair value of its common stock using methodologies, estimates and assumptions consistent with the American Institute of Certified Public Accountants 2013 Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation (the “AICPA Practice Guide”).  In addition, the Company’s Board of Directors also considered numerous objective and subjective factors, along with input from management and third-party valuations, to determine the fair value of the Company’s common stock as disclosed in the Registration Statement.

As noted in the Financial Notes, the Company has applied the probability-weighted expected return method (“PWERM”).  The Company elected to utilize the PWERM method as estimates regarding potential outcomes were considered reasonable. At each grant date, the Board of Directors considered whether any events occurred that would trigger any material changes to the business or would require adjustment to the estimated fair value from the previous valuation date. Under the PWERM valuation method, the per share value of the common stock is estimated based upon the probability-weighted present value of expected future equity values for the common stock, under various possible future liquidity event scenarios, discounted at risk-adjusted rates of return which take into consideration the rights and preferences of each class of stock.

On June 4, 2015, the Company’s Board of Directors granted stock options at an exercise price equal to the estimated fair value as determined by a Company valuation, dated May 28, 2015, which valuation was as of March 31, 2015 (the “March 2015 Valuation”).

The March 2015 Valuation was derived using the PWERM method and was based on the closing of the Company’s issuance of shares of Series D Preferred Stock (the “Series D Financing”), which had an initial closing of approximately $35.5 million on March 31, 2015 at a price per share of $0.611. The transaction was believed to be representative of an arm’s length transaction, as more than half of the aggregate amount raised included participation from new outside investors, and therefore indicative of the estimated fair value of a share of common stock

September 2, 2015

Page 4

as of the investment date. In addition, the March 2015 Valuation reflected, due to the passage of time, additional accrued growth of Company’s accruing paid-in-kind dividend in connection with the conversion of all shares of Series C and Series D Preferred Stock into shares of common stock immediately prior to the consummation of the Company’s proposed IPO, pursuant to the Company’s certificate of incorporation.

In performing such analysis, the PWERM valuation method was used to correlate the price per share of the Series D Financing with the following five potential future liquidity events:

(i) an initial public offering occurring by October 31, 2015 (the “2015 IPO”);

(ii) an initial public offering occurring during the first quarter of 2016, after a private financing in the first quarter of 2015 and receipt of results from the Company’s Phase 1 safety study of its lead product candidate (the “2016 IPO”);

(iii) additional private financing during the fourth quarter of 2016, and an initial public offering during the third quarter of 2017 concurrent with the Company’s Phase 2 trial of its lead product candidate (the “2017 IPO”);

(iv) additional private financing and FDA approval of one or more of the Company’s product candidates, followed by a structured acquisition or initial public offering by 2019 (the “2019 M&A/IPO”); and

(v) inability to achieve FDA approval for any of the Company’s product candidates, enter into a structured acquisition, or complete an initial public offering (the “Dissolution”).

For each of these potential events, the Company estimated the total proceeds to be distributed to equity holders and, ultimately, a present value estimate of the indicated value per share of common stock. A probability weighting of the applicable liquidity event was applied and resulted in the probability weighted indicated value per share.

The following table sets forth the results of the PWERM method analysis that was utilized in the March 2015 Valuation and subsequently used by the Company to determine the resulting Indicated Value of a Share of Common Stock (in millions, except per share data):

PWERM METHOD

2015 IPO

2016 IPO

2017 IPO

2019
   M&A/IPO

Dissolution

Total Estimated   Proceeds to be Distributed to Equity Holders

$

[***

]

$

[***

]

$

[***

]

$

[***

]

$

[***

]

Indicated Per   Share Value of Common Stock

$

[***

]

$

[***

]

$

[***

]

$

[***

]

$

[***

]

Probability   Weight Assigned

[***

]%

[***

]%

[***

]%

[***

]%

[***

]%

Probability   Weighted Indicated Value of a Share of Common Stock

$

[***

]

$

[***

]

$

[***

]

$

[***

]

$

[***

]

Indicated Value   of a Share of Common Stock

$

0.43

[***] CERTAIN INFORMATION IN THIS DOCUMENT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTION.

September 2, 2015

Page 5

DISCUSSION OF MOST RECENT FAIR VALUE DETERMINATION

In connection with preparing for a proposed IPO and the preparation of the Company’s financial statements to be included in the Registration Statement, the Company completed a valuation of its common stock, dated August 12, 2015, which valuation was as of June 30, 2015 (the “June 2015 Valuation”), pursuant to which, among other things, the probability of the 2015 IPO increased to [***]% and the probability of the 2016 IPO increased to [***]%.  Between March 31, 2015 and June 30, 2015, the Company took certain steps towards initiating and completing its proposed IPO, including holding an organizational meeting on June 19, 2015 and completing subsequent rounds of the Series D Financing, and received positive safety and other data from its ongoing Phase 1 clinical trial of its lead product candidate.

The following table sets forth the results of the PWERM method analysis that was utilized in the June 2015 Valuation and subsequently used by the Company to determine the Indicated Value of a Share of Common Stock as of June 30, 2015 (in millions, except per share data):

PWERM METHOD

2015 IPO

2016 IPO

2017 IPO

2019
   M&A/IPO

Dissolution

Total Estimated   Proceeds to be Distributed to Equity Holders

$

[***

]

$

[***

]

$

[***

]

$

[***

]

$

[***

]

Indicated Per Share   Value of Common Stock

$

[***

]

$

[***

]

$

[***

]

$

[***

]

$

[***

]

Probability   Weight Assigned

[***

]%

[***

]%

[***

]%

[***

]%

[***

]%

Probability   Weighted Indicated Value of a Share of Common Stock

$

[***

]

$

[***

]

$

[***

]

$

[***

]

$

[***

]

Indicated Value   of a Share of Common Stock

$

[***

]

PRELIMINARY ASSUMED IPO PRICE

On August 14, 2015, at a meeting of the Board of Directors, the Company and the lead underwriters for the Company’s IPO discussed the anticipated Preliminary IPO Price Range. On August 28, 2015, the lead underwriters for the Company’s IPO presented an update regarding the Preliminary IPO Price Range to certain members of the Board of Directors.  On August 31, 2015, at a meeting of the Board of Directors, the underwriters presented the Preliminary IPO Price Range for discussion with the Company.  As noted above under “Anticipated Actions,” the Company currently anticipates that the final Preliminary IPO Price Range (and related stock split) will be finalized and approved by the Company’s Board of Directors on or about

[***] CERTAIN INFORMATION IN THIS DOCUMENT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTION.

September 2, 2015

Page 6

September 8, 2015. Further, the anticipated Preliminary IPO Price Range is $[***] to $[***] per share, with a Preliminary Assumed IPO Price of approximately $[***] per share.  The foregoing prices per share do not reflect any stock split that the Company might affect prior to the Company’s IPO.

The following table summarizes the Company’s anticipated pre-offering equity values (based on the low-end, mid-point and high-end of the Preliminary IPO Price Range) (in millions, except per share data).

Low-End

Mid-Point

High-End

Pre-Offering   Equity Value

$

[***

]

$

[***

]

$

[***

]

Pre-Offering   Equity Value Per Share

$

[***

]

$

[***

]

$

[***

]

COMPARISON OF IPO PRICE RANGE AND ESTIMATED EQUITY FAIR VALUE PER SHARE

The Company notes that, as is typical in initial public offerings, the estimated Preliminary IPO Price Range was not derived using a formal valuation of fair value, but was determined by discussion between the Company and the underwriters.  The Company believes the difference between the Preliminary IPO Price Range and the earlier valuation report primarily results from consideration of a number of factors.  First, the valuation methodology used by the underwriters is based on quantitative and qualitative factors, which differ from the methodologies of the Company’s valuation specialists for the valuation reports. Additionally, the underwriters necessarily assume that an IPO has occurred and an active and liquid market for the stock has developed and, as such, the underwriters do not utilize any discounts for lack of marketability or probabilities for alternative outcome scenarios. Next, from June thr

CORRESP
1
filename1.htm

August 24,   2015

VIA EDGAR AND FEDERAL EXPRESS

United States Securities and Exchange   Commission
   Division of Corporation Finance
   100 F Street, N.E.
   Washington, D.C. 20549-6010

140 Scott Drive

Menlo Park, California 94025

Tel: +1.650.328.4600 Fax:   +1.650.463.2600

www.lw.com

FIRM / AFFILIATE OFFICES

Abu Dhabi

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San   Francisco

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London

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Washington,   D.C.

Attention:

Jeffrey P. Riedler, Assistant Director

File No. 053734-0005

Austin Stephenson

Bryan Pitko

Ibolya Ignat

Jim Rosenberg

Re:

Mirna   Therapeutics, Inc.

Registration   Statement on Form S-1

Filed   on August 24, 2015

CIK No. 0001527599

Ladies and Gentlemen:

On behalf of Mirna Therapeutics, Inc. (the “Company”), we are hereby filing a Registration Statement on Form S-1 (the “Registration Statement”). The Company most recently submitted a Draft Registration Statement on Form S-1 on July 15, 2015 (the “Draft Submission”) to the U.S. Securities and Exchange Commission (the “Commission”) on a confidential basis. The Registration Statement has been revised to reflect the Company’s responses to the comment letter to the Draft Submission received on August 12, 2015 from the staff of the Commission (the “Staff”). For your convenience, we are providing by overnight delivery a courtesy package that includes ten copies of the Registration Statement, five of which have been marked to show changes from the Draft Submission, as well as copy of this letter.

For ease of review, we have set forth below each of the numbered comments of your letter in bold type followed by the Company’s responses thereto.

Prospectus Summary, page 1

1.              We refer to your product pipeline table on pages 1 and 87 and specifically to your indication that several of the programs related to undisclosed microRNA.  Please revise your pipeline table to identify each undisclosed microRNA and therapeutic category.  Unless a therapeutic category and a compound have been identified, the product appears too preliminary for inclusion in the table.  Accordingly, please identify the target microRNA and therapeutic category in the table or alternately, eliminate these candidates from the table.

August 24, 2015

Page 2

Response:  In response to the Staff’s comment, the Company has revised the pipeline table on pages 1 and 87 of the Registration Statement.

Stock-Based Compensation, page 79

2.              We may have additional comments on your accounting for equity issuances including stock compensation and beneficial conversion features.  Once you have an estimated offering price, please provide us an analysis explaining the reasons for the differences between recent valuations of your common stock leading up to the IPO and the estimated offering price.

Response:  In response to the Staff’s comment, the Company confirms that it will provide to the Staff the requested analysis under separate supplemental cover.

Business

MRX34 Clinical Development Program, page 99

3.              Please revise your disclosure in this section to disclose the initial filing date of your IND and a description of the approved Phase 1 trial by the FDA and any subsequent amendment(s) to the trial protocol.

Response:  In response to the Staff’s comment, the Company has revised page 99 of the Registration Statement.

Our Patent Portfolio, page 108

4.              Please revise your disclosure to specify when the patents licensed from Yale with respect to the uses of let-7 microRNA are expected to expire.

Response:  In response to the Staff’s comment, the Company has revised page 113 of the Registration Statement.

Strategic Partnerships and Collaborations, page 120

5.              We refer to your last risk factor on page 45 and note that you highlight a license from Merck as important to your business.  We also note your cross-reference to the disclosure under the heading “Business—Strategic Partnerships and Collaborations” for a full description of the Merck agreement including the material terms and obligations, and termination provisions.  The disclosure appearing under this heading does not appear to include any information concerning the Merck agreement.  Accordingly, please revise this section to disclose the material terms and obligations of your agreement with Merck.  In addition, please file the agreement as an exhibit to the registration statement.

Response:  In response to the Staff’s comment, the Company respectfully notes to the Staff that the reference to the Merck agreement was included erroneously. Accordingly, the Company has revised page 45 of the Registration Statement.

August 24, 2015

Page 3

Exhibit Index

6.              Please file your sublease and the amended service agreement with Asuragen as an exhibit to your Form S-1 in accordance with Item 601 of Regulation S-K.

Response:  In response to the Staff’s comment, the Company has filed the sublease and the amended service agreement with Asuragen as Exhibits 10.11, 10.1(A) and 10.1(B), respectively, to the Registration Statement.

* * *

We hope the foregoing answers are responsive to your comments. Please do not hesitate to contact me by telephone at (650) 463-3043 or by fax at (650) 463-2600 with any questions or comments regarding this correspondence.

Very   truly yours,

/s/   Mark V. Roeder

Mark   V. Roeder

of   LATHAM & WATKINS LLP

cc:

Paul   Lammers, M.D., M.Sc., Mirna Therapeutics, Inc.

Jon   Irvin, Mirna Therapeutics, Inc.

Scott   D. Elliot, Esq., Ropes & Gray LLP

Patrick   O’Brien, Esq., Ropes & Gray LLP

Mail Stop 4720

August 12, 2015

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. 4 to Draft Registration Statement on Form S -1
Submitted July 15, 2015
CIK No. 0001527599

Dear Dr. Lammers :

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

Please respond to this letter by providing the requested information and either submitting
an amended draft registration statement or  publicly  filing your registration statement on
EDGAR.  If you do not believe our comments apply to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.

After reviewing the information you provide in response to these  comments  and your
amended draft registration statement or filed registration statement,  we may have  additional
comments.

Prospectus Summary, page 1

1. We refer to your product pipeline table  on pages 1 and 87  and specifically to your
indication that several of the programs related to undisclosed microRNA .  Please revise
your pipeline table to identify each undisclosed microRNA and therapeutic category.
Unless a therapeutic category and a comp ound have been identified, the product appears
too preliminary for inclusion in the table.  Accordingly, please identify the target
microRNA and therapeutic category in the table or alternately, eliminate these candidates
from the table.

Paul Lammers, M.D., M.Sc.
Mirna Therapeutics, Inc.
August 12, 2015
Page 2

 Stock -Based C ompensation, page 79

2. We may have additional comments on your accounting for equity issuances including
stock compensation and beneficial conversion features. Once you have an estimated
offering price, please provide us an analysis explaining the reasons f or the differences
between recent valuations of your common stock leading up to the IPO and the estimated
offering price.

Business

MRX34 Clinical Development Program , page 99

3. Please revise your disclosure in this section to disclose the initial filing d ate of your IND
and a description of the approved Phase 1 trial by the FDA and any subsequent
amendment(s) to the trial protocol.

Our Patent Portfolio, page 10 8

4. Please revise your disclosure to specify when the patents licensed from Yale with respect
to the uses of let -7 microRNA are expected to expire

Strategic Partnerships and Collaborations , page 120

5. We refer to your last risk factor on page 45  and note that you highlight a license from
Merck as important to your business.  We also note your cross -reference to the disclosure
under the heading “ Business —Strategic Partnerships and Collaborations” for a full
description of the Merck agreement inclu ding the material terms and obligations, and
termination provisions .  The disclosure appearing under this heading does not appear to
include any information concerning the Merck agreement.  Accordingly, please revise
this section to disclose the material t erms and obligations of your agreement with Merck.
In addition, please file the agreement as an exhibit to the registration statement.

Exhibit Index

6. Please file your  sublease and the amended service agreement with Asuragen as an exhibit
to your Form S -1 in accordance with Item 601 of Regulation S -K.

Paul Lammers, M.D., M.Sc.
Mirna Therapeutics, Inc.
August 12, 2015
Page 3

 You may contact Sasha Parikh at (202) 551 -3627 or Jim Rosenberg at (202)  551-3679 if
you have questions regarding comments on the financial statements and related matters. Please
contact Tara Keating  Brooks at (202) 551 -8336 , Bryan Pitko at (202) 551 -3203, or me at (202)
551-3715 with any other questions.

Sincerely,

 /s/ Bryan J. Pitko for

Jeffrey P. Riedler
Assistant Director
Office of Healthcare and Insurance

cc:   Via E -mail
Mark V. Roeder
Latham & Watkins LLP

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

April 9 , 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.
Confidential Draft Registration Statement on Form S -1
Submitted March 12, 2014
CIK No. 0001527599

Dear Dr. Lammers:

We have reviewed your confidential draft registration statement and have the following
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 publicl y 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 res ponse to these com ments and your
amended confidential draft registration state ment or filed registration state ment, we may have
additio nal co mments.

General

1. Please sub mit all outstanding exhibits as soon as prac ticable.  We may have further
comments upon  examination of these exhibits.

2. Please provide us proofs of all graphic, visual or photographic information you will
provide in the printed prospectus prior to its use, for example in a preliminary prospectus.
Please note that we may have comments regardi ng this material.

3. Please supplementally provide us with copies of all written communications, as defined
in Rule 405 under the Securities Act, that you, or anyone authorized to do so on your
behalf, present to potential investors in reliance on Section 5( d) of the Securities Act,
whether or not they retain copies of the communications. Similarly, please

Paul Lammers, M.D., M.Sc.
Mirna Therap eutics, Inc.
April 9 , 2014
Page 2

 supplementally provide us with any research reports about you that are published or
distributed in reliance upon Section 2(a)(3) of the Securities Act of 1 933 added by
Section 105(a) of the Jumpstart Our Business Startups Act by any broker or dealer that is
participating or will participate in your offering.

Prospectus Summary, page 1

4. We note your statement here and throughout the registration statement th at you are a
“leading clinical stage biopharmaceutical company developing a broad pipeline of
microRNA -based oncology therapeutics.”  In light of the early -stage development of your
product candidates and the fact that you have only one product candidate i n clinical trials,
please revise your disclosure to delete reference to being a “leading” clinical stage
biopharmaceutical company.

5. Please revise your disclosure to identify the other scientists and leading academic
institutions who have reached conclus ions about the key role that microRNAs play in
tumor suppression.

6. Please define the term “transient transfection” at your first reference on page 4.

7. We note your inclusion of a pipeline chart on this page and on pages 82 and 95 and, in
particular, your in clusion of certain early development programs which rely on
undisclosed microRNA.  Please revise your pipeline chart to identify the applicable
microRNA or microRNA mimic for each program and disclose the relevant potential
indication(s) that will be pursu ed for each program, if known.  In the alternative, please
remove reference to such programs in light of their very early stage of development and
the lack of information with respect to the microRNA relied upon for these programs.

Risk Factors
“We hav e incurred significant losses since inception…,” page 10

8. Please revise your risk factor disclosure to include your total accumulated deficit to date.

“We are highly dependent on the services of our President and Chief Executive Officer, Paul
Lammers, M.D., M.Sc., and other key executives and scientists…,” page 32

9. Please identify the other key executive and scientists upon which you are highly
dependent.

“If we are unable to obtain and maintain sufficient patent protection for our technology and
produ ct candidates…,” page 37

10. Please revise your risk factor discussion to include a brief discussion of your most
material patents, the product candidates or technology to which they relate, the

Paul Lammers, M.D., M.Sc.
Mirna Therap eutics, Inc.
April 9 , 2014
Page 3

 jurisdiction in which they were granted, and the expected expira tion date of the patent
protection.

“If we breach any of the agreements under which we license the use, development and
commercialization rights to our product candidates…,” page 43

11. Please revise your risk factor disclosure to provide a brief description  of the license
agreements upon which you are principally reliant including the product candidates
and/or technology covered and the material terms and obligations under such agreements.

“If approved, MRX34 or any future products may cause or contribute t o adverse medical
events…,” page 50

12. We note your disclosure that some participants in your Phase 1 clinical trial of MRX34
have reported adverse effects after being treated with MRX34.  Please revise your risk
factor disclosure to provide the following in formation:

 the number of patients who have experienced an adverse event;
 the specific adverse events experienced;
 whether any such events were characterized as severe;
 whether such adverse events were determined to be related to the administration
of MRX 34; and
 whether, and if so, how, such events impact your assessment of the safety profile
for MRX34.

Please also include th is information with respect to adverse events in the other locations
of the prospectus in which you discuss the Phase 1 clinical  trial of MRX34.

“We may be subject to claims challenging the inventorship or ownership of our patents…,” page
44

13. Please revise your risk factor to discuss the extent to which your financial obligations to
Yale are related to your leading product candidates and, if so, please include a description
of any such financial obligations.

Use of Proceeds, page 62

14. We note that you intend to use a specific amount of proceeds from the offering to fund
clinical development expenses for MRX34.  Please expand  your disclosure to indicate
whether you expect the proceeds from this offering together with existing cash and cash
equivalents to enable you to complete the Phase 1 trial.  If not, please disclose what the
offering proceeds and your existing cash will al low you to accomplish as to the Phase 1
trial.

Paul Lammers, M.D., M.Sc.
Mirna Therap eutics, Inc.
April 9 , 2014
Page 4

 15. Pursuant to the requirements of Item 504 of Regulation S -K, where you have identified
the specific purposes for which you intend to use the offering proceeds, you must
disclose the approximate amount of proc eeds intended to be used for each such purpose.
In this regard, please provide an estimate of the amount of proceeds that you intend to use
for the development of each of your product candidates in preclinical development.
Please make any necessary confo rming changes to your Prospectus Summary as well.

Managements’ Discussion and Analysis of Financial Condition and Results of Operations
Critical Accounting Policies and Estimates
Stock -based Compensation, page 74

16. Please note that we are deferring final e valuation of stock compensation and related costs
until an amendment including your estimated offering price has been filed.  Advise us of
any new option grants or other equity issuances and include the date of grant or issuance,
the exercise price, the fa ir value of the equity instrument at the date of grant and how you
determined the fair value.  Please provide us with a quantitative and qualitative analysis
explaining the difference between the estimated offering price and the fair value of most
recent e quity issuance.

Results of Operations
Research and Development Expenses, pages 75 and 77

17. To help us better understand your research and development expenses for each of the
three years and your explanations of the year over year changes, please provide us a
schedule for each year that provides a break -down of research and development expenses
showing at a minimum the following categories: salaries and personnel -related costs,
consulting fees, fees paid for contract research services, the costs of laboratory equipment
and facilities, license fees and other external costs.  For each category, sho w the amount
of government grant reimbursement.  Reconcile each year to total research and
development expenses shown in your statements of operations.

Business
Overview, page 81

18. We note your disclosure that MRX34 has shown a manageable safety profile  through the
first 45 weeks of your Phase 1 clinical trial.  Please revise your disclosure to explain what
constitutes a “manageable” safety profile.  Please also discuss the specific experiences of
your subjects which led you to reach this conclusion.  In  this regard, please provide a full
discussion of the adverse events experie nced by patients in your Phase 1  trial, to date.
Such discussion should include all information highlighted in our comment above with
respect to your risk factor at page 50.

19. We n ote your reference to the published reports from microRNA scientists at numerous
research institutions with respect to the key role miR -34 plays in controlling oncogene

Paul Lammers, M.D., M.Sc.
Mirna Therap eutics, Inc.
April 9 , 2014
Page 5

 expression.  Please identify the scientists and institutions to which you are referring , the
publications in which the reports were published, and whether such publications were
peer-reviewed.

MRX34 Clinical Development Program, page 96

20. We note your reference to certain ongoing Phase 2 clinical trials for a product known as
PNT2258 with re spect to the delivery abilities of Smarticles.  Please revise your
disclosure to identify the company conducting such trials.

21. We note disclosure on page 76 indicating that an Investigational New Drug (IND)
application for MRX34 was filed in 2013.  Please disclose the date the application was
filed, the identity of the filer, and the relevant indication(s).  In particular, please
specifically disclose whether you were required to file a separate IND for the
hematological malignancies cohort added to your Ph ase 1 trial.  If not, please explain
why.

22. We note your disclosures throughout the prospectus, including on page 81, that you
expect completed results in the Phase 1 trial in the liver -based cohort by the end of the
first quarter of 2015 and completed re sults from the hematological malignancy cohort in
mid-2015.  Please disclose whether interim or preliminary data are expected to be
available for either cohort and if so, when such data will become available.

23. You disclose on page 97 that the secondary o bjectives of the Phase 1 trial for MRX34
relate to pharmacokinetics, pharmacodynamics, and clinical activity.  On page 4 of your
prospectus summary, you disclose that safety is also an objective of this trial.  Please
disclose here whether you intend to as sess safety of treatment with MRX34 as a
secondary objective of this trial.

Combination Therapy for MRX34, pages 99 -100

24. We note your disclosure that cell culture and animal liver cancer models have shown that
MRX34 could be more effective when used in combination with sorafenib.  Please
disclose the observations from these earlier studies that you believe support this
conclusion.

Manufacturing
Drug Product, page 101

25. Please disclose all material terms of your manufacturing and supply agreement with
Polymun.  Please include a description of all material rights and obligations of the parties,
as well as a discussion of the agreement’s termination and duration provisions.  Please
additionally file the agreement as an exhibit to your registration statemen t pursuant to

Paul Lammers, M.D., M.Sc.
Mirna Therap eutics, Inc.
April 9 , 2014
Page 6

 Item 601(b)(10) of Regulation S -K.  Alternatively, if you do not believe you are
substantially dependent on the agreement, please advise us as to the basis of your beliefs.

Our Patent Portfolio, page 102

26. Please revise your disclosure to specify when the patents licensed from Yale with respect
to the uses of let -7 microRNA are expected to expire.

Strategic Partnerships and Collaborations
Yale University, page 115

27. Please disclose what patents are subject to the Yale license agreement and which of your
product candidates are reliant on such patents.  In particular, please clarify whether any of
the underlying patent rights relate to your primary product candidate, MRX34, and
confirm whether the specified royalty provisions are also applicab le to net sales of
MRX34.

28. Please revise your disclosure to discuss how the termination of your patent rights under
the Yale license agreement impacts your corresponding patent rights under the Asuragen
license agreement, and vice versa.

CPRIT, page 116

29. We note your disclosed obligation to pay CPRIT a portion of your revenue from sales of
certain products.  Please clarify whether your royalty obligations are applicable to sales
of MRX34.

Director Compensation, page 126

30. Please file the January 2013 directors’ compensation policy referenced on this page as an
exhibit to your registration statement.

Terms and Conditions of Employee Arrangements with our NEOs, page 129

31. Please file the employment agreements with your NEOs as exhibits to your registra tion
statement.

Shares Eligible for Future Sale
Lock -up Agreements, page 152

32. Please file the form of lock -up agreement as an exhibit to your registration statement.

Paul Lammers, M.D., M.Sc.
Mirna Therap eutics, Inc.
April 9 , 2014
Page 7

 Financial Statements
Notes to Financial Statements
3. Cancer Prevention and Research Institute of Texas Grant and Other Grants, page F -14

33. Please refer to your disclosure that, under the terms of the award, the Company is
required to pay to CPRIT a portion of its revenues from sales of certain products by the
Company, or received from the Company's licensees or sublicensees, at a percentage in
the low single digits until the aggregate amount of such payments equals a specified
multiple of the grant amount, and thereafter at a rate of less than one percent, subject to
the Company's right, un der certain circumstances, to make a one -off payment in a
specified amount to CPRIT to buy out such payment obligations.  Disclose your
accounting policy with respect to these terms.
9. Stock Option Plans, page F -19
34. Please include the disclosures required  by ASC 718 -10-50-2.d. and e.

If you intend to respond to these comments with an amended draft registration statement,
please submit it and any associated correspondence in accordance with the guidance we provide
in the Division’s October 11, 2012 announ cement on the SEC website at
http://www.sec.gov/divisions/corpfin/cfannouncements/drsfilingprocedures101512.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
confi dential submissions to us so we do not repeat or refer to that information in our comment
letters to you.

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 Pitko 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