December 17, 2018

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

       Re: Cyclerion Therapeutics, Inc.
           Amendment No. 1 to Draft Registration Statement on Form 10
           Submitted on December 6, 2018
           CIK 0001755237

Dear Dr. Currie:

      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.

Amendment No. 1 to Draft Registration Statement on Form 10 submitted December
6, 2018

Exhibit 99.1
Information Statement Summary
Cyclerion
Overview, page 12

1.     We note your response to comment 5 and your disclosure that you intend
to out license
       praliciguat to a "leader in cardiometabolic diseases." Please revise
your disclosure to
       remove the implication that you have a prospective agreement with a
licensee or
       collaboration partner for this product candidate. Alternatively, please
tell us the basis for
       this statement.
 Mark Currie
Cyclerion Therapeutics, Inc.
December 17, 2018
Page 2
Unaudited Pro Forma Combined Financial Statements
Notes to Unaudited Pro Forma Combined Financial Data, page 65

2.    Regarding pro forma adjustment (C), you include the shares to be issued
in the intended
      private placement in determining the number of Cyclerion shares of common
stock used
      to compute basic earnings per share. Please tell us how you determined
that the private
      placement is factually supportable and directly attributable to the
separation transaction.
      Please also tell us how you determined that it was appropriate to include
these shares in
      your pro forma EPS calculation given that the proceeds from the issuance
of these shares
      are not reflected as an adjustment in your pro forma Statement of
Operations.
Business
Praliciguat for Cardiometabolic Diseases
Our Solution, page 96

3.    We note your response to comment 8 and your disclosure that results of
your Phase 2a
      study of praliciguat suggested that patients had improvements in insulin
sensitivity and in
      endothelial function. Please revise your disclosure to remove the
implication that
      treatment with praliciguat resulted in the measurements cited. You may
describe any
      objective observations from the trials without indicating that
praliciguat is responsible for
      these observations.
       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
questions.



                                                             Sincerely,
FirstName LastNameMark Currie
                                                             Division of
Corporation Finance
Comapany NameCyclerion Therapeutics, Inc.
                                                             Office of
Healthcare & Insurance
December 17, 2018 Page 2
cc:       Will Michener, Esq.
FirstName LastName