December 10, 2024

Michael Cloonan
President and Chief Executive Officer
Sionna Therapeutics, Inc.
21 Hickory Drive, Suite 500
Waltham, MA 02451

       Re: Sionna Therapeutics, Inc.
           Amendment No. 1 to Draft Registration Statement on Form S-1
           Submitted November 26, 2024
           CIK No. 0002036042
Dear Michael Cloonan:

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

       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 a 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 letter
and your
amended draft registration statement or filed registration statement, we may
have additional
comments. Unless we note otherwise, any references to prior comments are to
comments in
our October 10, 2024 letter.

Amendment No. 1 to Draft Registration Statement on Form S-1 submitted November
26,
2024
Risk Factors
We contract with third parties for the manufacture of our product candidates
for clinical drug
supply..., page 36

1.     We note your response to prior comment 13. Please revise your risk
factor to disclose
       the single services agreement with WuXi AppTec (HongKong) Limited, as
WuXi is a
       Chinese biotechnology company of concern named in the BIOSECURE Act,
which
       could impact the availability of U.S. government contracts, grants, and
loans. Please
       also revise your statement that the company has "in the past relied" on
foreign
 December 10, 2024
Page 2

       CDMOs in China.
General

2.     We note that you have removed all disclosure related to SION-638 from
the
       prospectus. We also note a press release dated January 3, 2024, which
       described SION-638 as your "lead candidate". In your response letter,
please explain
       the removal of the disclosure regarding this product candidate and
whether the
       company has discontinued its development.
       Please contact Jenn Do at 202-551-3743 or Angela Connell at 202-551-3426
if you
have questions regarding comments on the financial statements and related
matters. Please
contact Tamika Sheppard at 202-551-8346 or Laura Crotty at 202-551-7614 with
any other
questions.



                                                           Sincerely,

                                                           Division of
Corporation Finance
                                                           Office of Life
Sciences
cc:   Gabriela Morales-Rivera