United States securities and exchange commission logo

                              December 3, 2020

       David Kirn
       Chief Executive Officer
       4D Molecular Therapeutics Inc.
       5858 Horton Street #455
       Emeryville, CA 94608

                                                        Re: 4D Molecular
Therapeutics Inc.
Statement on Form S-1
                                                            Filed November 17,
                                                            File No. 333-250150

       Dear Dr. Kirn:

              We have reviewed your 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 amending your registration
statement and providing the
       requested information. 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

              After reviewing any amendment to your registration statement and
the information you
       provide in response to these comments, we may have additional comments.

       Registration Statement on Form S-1

       Prospectus Summary
       Our Therapeutic Vector Evolution Platform, page 2

   1.                                                   We note your revisions
in response to prior comment 4. Please revise your disclosure on
                                                        pages 2 and 118 where
you discuss your head-to-head comparisons with conventional
                                                        AAV vectors to state,
if true, that you have not conducted any clinical studies in patients
                                                        comparing your targeted
and evolved vectors to conventional AAV vectors. Please also
                                                        revise your disclosure
on pages 2 and 118 that you "expect" to demonstrate the superior
                                                        capabilities of your
targeted and evolved vectors and product candidates as you advance
                                                        through clinical trials
to remove the expectation regarding how your vectors and product
                                                        candidates will perform
in clinical trials as such statements are speculative.
 David Kirn
FirstName LastNameDavid    Kirn
4D Molecular  Therapeutics Inc.
December   Name4D
             2020 Molecular Therapeutics Inc.
Page 2    3, 2020 Page 2
FirstName LastName
Our Product Candidate Pipeline, page 3

2.       We note the added table depicting your most advanced discovery and
research programs.
         Additionally, we note that your filing does not include a discussion
of 4D-3XX or 4D-
         7XX, which implies that these programs are not sufficiently material
to your operations to
         warrant discussion. Please delete the references to these programs
from your summary.
3.       We note your response to comment 7 and believe TVP and Lead
Optimization should be
         depicted together under a column heading such as discovery or research
         development. A textual discussion of the program is a more appropriate
place to make the
         distinctions regarding different tasks within a particular phase.
Competition and Differentiation: AAV Gene Therapy for wet AMD and Diabetic
page 155

4.       We note your response to prior comment 12. Please revise your
statement that 4D-150
         would be the only AAV gene therapy asset in wet AMD and DR that has
shown superior
         transduction on human retinal cells ex vivo versus conventional AAV
vectors such as
         AAV2 to clarify, if true, that your statement is based solely on in
vitro studies you
         conducted comparing R100 to AAV2 discussed on page 138.
Principal Stockholders, page 222

5.       Please revise your disclosure to identify the natural person or
persons who have voting
         and investment control of the shares held by the entities affiliated
with BVF.
10. Redeemable Convertible Preferred Stock
Funding Agreement with CFF (unaudited), page F-39

6.       We note the $10.0 million received from CFF is to "be used to advance
the development
         program for 4D-710, the Company   s lead product in cystic fibrosis,
or any other
         therapeutic approved by the Program Advisory Group (   PAG   ) to
alleviate pulmonary
         complications of cystic fibrosis". With reference to the specific
terms of the Funding
         Agreement, please address the need to separately classify the $10.0
million as restricted
         cash. Refer to Rule 5-02.1 of Regulation S-X.
        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration

         You may contact Jenn Do at 202-551-3743 or Jeanne Baker at
202-551-3691 if you have
 David Kirn
4D Molecular Therapeutics Inc.
December 3, 2020
Page 3

questions regarding comments on the financial statements and related matters.
Please contact
Ada Sarmento at 202-551-3798 or Suzanne Hayes at 202-551-3675 with any other

FirstName LastNameDavid Kirn                               Sincerely,
Comapany Name4D Molecular Therapeutics Inc.
                                                           Division of
Corporation Finance
December 3, 2020 Page 3                                    Office of Life
FirstName LastName