September 13, 2019

David Socks
President and Chief Executive Officer
Phathom Pharmaceuticals, Inc.
70 Williow Road
Suite 200
Menlo Park, CA 94025

       Re: Phathom Pharmaceuticals, Inc.
           Amendment No. 1 to Draft Registration Statement on Form S-1
           Submitted August 30, 2019
           CIK No. 0001783183

Dear Mr. Socks:

      We have reviewed your amended draft registration statement and have the
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. Unless we note otherwise, our references to prior comments are to
comments in our
August 22, 2019 letter.

Amendment No. 1 to Draft Registration Statement on Form S-1

Critical Accounting Policies and Significant Judgments and Estimates
Fair Value of Warrant Liabilities and Convertible Promissory Notes , page 99

1.     We acknowledge your response to prior comment 9 where you explain that
you do not
       believe that the requested sensitivity analysis would satisfy the
principles in SEC Release
       No. 33-8350 due to the reasons listed. You further state that you
believe that the
       preparation of a meaningful and reasonable quantitative sensitivity
analysis for the fair
       value of the warrant liabilities and the convertible promissory notes is
impractical due to
       the numerous interrelated inputs that go into your highly complex
models. Please tell us
 David Socks
Phathom Pharmaceuticals, Inc.
September 13, 2019
Page 2
      how your disclosures made In Note 1 of your combined financial statements
under Fair
      Value Measurements starting on page F-9 comply with the requirements of
ASC 820-10-
      50-2, including sub-point g. that requires certain disclosures to be made
when there
      are interrelationships between inputs used to arrive to fair value. If
you continue to
      believe that providing the requested disclosure is impractical, please
explain to us and
      disclose the factors you consider and procedures you undertake to attempt
to develop the
      required disclosure.
PPI Limitations, page 108

2.    We note your disclosure that you commissioned a third-party U.S. market
      study. With respect to the statements in your prospectus that are based
on this third-party
      research, please revise to clarify whether such statements are statements
of the third party
      or statements of the registrant. If your disclosure attributes a
statement to the third party,
      please revise your filing to identify such third party and file a consent
from such third
      party. Please see Securities Act Rule 436 and Question 233.02 of the
Securities Act Rules
      Compliance and Disclosure Interpretations.
       You may contact Ibolya Ignat at 202-551-3636 or Lisa Vanjoske at
202-551-3614 if you
have questions regarding comments on the financial statements and related
matters. Please
contact Ada D. Sarmento at 202-551-3798 or Suzanne Hayes at 202-551-3675 with
any other

FirstName LastNameDavid Socks
                                                             Division of
Corporation Finance
Comapany NamePhathom Pharmaceuticals, Inc.
                                                             Office of
Healthcare & Insurance
September 13, 2019 Page 2
cc:       Cheston J. Larson, Esq.
FirstName LastName