November 27, 2018

Alison Lawton
Chief Executive Officer
Kaleido Biosciences, Inc.
65 Hayden Avenue
Lexington, MA 02421

       Re: Kaleido Biosciences, Inc.
           Amendment No. 2 to Draft Registration Statement on Form S-1
           Submitted November 21, 2018
           CIK No. 0001751299

Dear Ms. Lawton:

     We have reviewed your amended draft registration statement and have the
following
comment.

       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 comment applies 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 this comment
and your
amended draft registration statement or filed registration statement, we may
have additional
comments.

Amendment No. 2 to Draft Registration Statement on Form S-1 submitted on
November 21,
2018

Prospectus Summary
Overview, page 1

1.     We note your response to our prior comment one that you anticipate
beginning clinical
       trials under an IND prior to commencing the roadshow. However, to the
extent you do
       not begin clinical trials by the time you publicly file your
registration statement, please
       revise the first sentence of the first paragraph to clarify that you are
a non-IND clinical
       stage healthcare company.
 Alison Lawton
Kaleido Biosciences, Inc.
November 27, 2018
Page 2

        You may contact Keira Nakada at 202-551-3659 or Jim Rosenberg at
202-551-3679
if you have questions regarding comments on the financial statements and
related matters.
Please contact Irene Paik at 202-551-6553 or Erin Jaskot at 202-551-3442 with
any other
questions.



                                                          Sincerely,
FirstName LastNameAlison Lawton
                                                          Division of
Corporation Finance
Comapany NameKaleido Biosciences, Inc.
                                                          Office of Healthcare
& Insurance
November 27, 2018 Page 2
cc:       Kingsley L. Taft - Goodwin Procter LLP
FirstName LastName