November 5, 2018

Mark Currie
Cyclerion Therapeutics, Inc.
301 Binney Street
Cambridge, MA 02142

       Re: Cyclerion Therapeutics, Inc.
           Draft Registration Statement on Form 10
           Submitted on October 9, 2018
           CIK 0001755237

Dear Dr. Currie:

       We have reviewed your 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
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

Draft Registration Statement on Form 10 submitted on October 9, 2018

Industry and Other Data, page i

1.     Please revise your statements that you have verified industry and market
data from third
       party sources to clarify that you are liable for the information
included in the registration
Cover page, page 1

2.     Please revise your disclosure to remove promotional statements
concerning Ironwood's
       anticipated profitability, strong revenue growth and expanding margins
as these
 Mark Currie
FirstNameTherapeutics, Inc.
Cyclerion LastNameMark Currie
Comapany 5, 2018
November NameCyclerion Therapeutics, Inc.
November 5, 2018 Page 2
Page 2
FirstName LastName
         statements are speculative and inappropriate for you to make. We will
not object to an
         objective discussion of Ironwood's continuing business and product
Information Statement Summary
Overview, page 11

3.       We note your statement that the presentation in your pipeline
development chart
         represents ongoing phases of development and does not correspond to
the initiation or
         completion of a particular phase. Please revise your pipeline
development chart so that the
         arrows correspond to the current stage of development. As an
illustrative example only,
         we note that you have not yet completed Phase 2 development for any of
your product
         candidates. Please revise your disclosure accordingly.
Value-Creating Enablers, page 13

4.       We note statements throughout your information statement that imply
you will be able to
         successfully progress your product candidates to commercialization in
a rapid or
         accelerated manner and/or mitigate risk of unsuccessful clinical
trials. As these statements
         are speculative and suggest that investors are afforded protection
from loss, please revise
         your disclosure here and throughout your information statement to
remove these
         implications. As a non-exhaustive list of illustrative examples only,
we note the following
           We leverage a diverse cross-disciplinary network of external
advisors and experts to
             advance our drug candidates quickly and with early, risk-reducing
clinical readouts.

           The collective experience and singular focus of the team in the
biology and
             pharmacology of the nitric oxide-cGMP pathway, as well as the
medicinal chemical
             insights around sGC stimulators, give us unique insights into the
mechanisms by
             which to realize the therapeutic potential of pharmacologically
tailored sGC
             stimulation. Further, this allows increasingly rapid discovery and
development of
             differentiated compounds optimized for their disease target.
           This program structure coupled with our streamlined governance is
designed to
             support high-velocity decision making and rapid rescaling and
redeployment of
5.       We note your description of your "best owner approach" whereby you
develop and
         commercialize product candidates independently or through a partner
depending on which
         path you believe will offer the greatest risk-adjusted value for our
stockholders and
         accelerates global patient access to our drugs. Please clarify whether
you have any
         partnerships related to any of your product candidates. If you do,
please describe these
         agreement and file them as exhibits to provide as with an analysis
supporting your
         determination that they are not required to be filed.
 Mark Currie
Cyclerion Therapeutics, Inc.
November 5, 2018
Page 3
Risks Related to our Business, page 14

6.       Please add a bullet point highlighting the risk of competition from
marketed products and
         product candidates in development, as discussed on page 39.
Risk Factors, page 20

7.       Please add a risk factor under an appropriate heading that discusses
the risk that you will
         be dependent on the intellectual property license agreement with
Ironwood. Once known,
         please expand your disclosure in the Business section to include all
of the material terms
         of the license agreement.
Our solution, page 90

8.       We note your disclosure that olinciguat has the potential for similar
efficacy in SCD
         patients. Efficacy determinations are the within sole authority of the
FDA. Please revise
         your disclosure to remove the implication that your clinical data
shows efficacy. Please
         revise similar statements throughout your information statement that
refer to your product
         candidate's potential for efficacy or clinical activity. We will not
object to an objective
         discussion of your observations in clinical and preclinical studies.
However, your
         disclosure should not indicate that the treatment resulted in the
       You may contact Sasha Parikh at 202-551-3627 or Angela Connell at
202-551-3426 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Christine Westbrook at 202-551-5019 or Suzanne Hayes at 202-551-3675
with any other

FirstName LastNameMark Currie                                  Sincerely,
Comapany NameCyclerion Therapeutics, Inc.
                                                               Division of
Corporation Finance
November 5, 2018 Page 3                                        Office of
Healthcare & Insurance
FirstName LastName