United States securities and exchange commission logo





                            November 10, 2020

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

                                                        Re: 4D Molecular
Therapeutics Inc.
                                                            Draft Registration
Statement on Form S-1
                                                            Submitted October
14, 2020
                                                            CIK No. 0001650648

       Dear Dr. Kirn:

              We have reviewed your 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.

       Draft Registration Statement on Form S-1

       Prospectus Summary
       Overview, page 1

   1.                                                   Please balance the
disclosure in the summary with disclosure that your product candidates
                                                        are based on a novel
AAV gene therapy technology with which there is limited regulatory
                                                        and clinical experience
and that few gene therapy products have been approved by the
                                                        FDA or comparable
foreign regulatory agencies Therefore, it is difficult to predict how
                                                        long it will take to
development your product candidates and obtaining regulatory
                                                        approval. Also disclose
in the summary that the regulatory approval process for novel
                                                        product candidatescan
be more expensive and take longer than for other, better known or
                                                        extensively studied
therapeutic modalities. Finally, revise your disclosure on page 5 and
 David Kirn
FirstName LastNameDavid   Kirn
4D Molecular Therapeutics Inc.
Comapany 10,
November   Name4D
              2020 Molecular Therapeutics Inc.
November
Page 2    10, 2020 Page 2
FirstName LastName
         page 117 that you will "apply [y]our modular product design and
engineering approach to
         accelerate the pace of product development" to remove any implication
that you will be
         able to accelerate the development of your product candidates as such
statements are
         speculative.
2.       Please delete the statements that an evolved vector increases the
likelihood of success and
         could accelerate the pace of product development and that your
competitive advantages
         and experience uniquely position you to successfully create, develop
and manufacture
         targeted gene therapies. Given the number of product candidates that
never receive FDA
         approval, the time required to obtain approval and the number of
companies currently
         developing product candidates, your statements that you are in a
unique position, have an
         increased likelihood of success and can develop products more quickly
is not appropriate.
Our Therapeutic Vector Evolution Platform, page 2

3.       Please substantiate your statement that you have developed an
"industry-leading"
         collection of synthetic capsid sequences.
4.       Please revise your disclosure here and in the Business section to
provide appropriate
         context for various conclusions and predictions as to the performance
of your product
         candidates and revise and/or remove any statements that imply safety
or efficacy as safety
         and efficacy are determinations that are solely within the authority
of the FDA or similar
         foreign regulators. For example, we note statements that your vectors
"achieved enhanced
         delivery, increased transgene expression, reduced immunogenicity
and/or improved
         antibody resistance when compared to conventional AAV vectors," that
you expect to
         demonstrate improved safety and efficacy of your product candidates
versus conventional
         AAV vectors and various other claims regarding the superiority of your
product
         candidates to those using conventional AAV vectors, including certain
statements in the
         sections regarding competition and differentiation of your various
product
         candidates. Please revise your disclosure to remove any suggestion
that there is an
         expectation that your product candidates will be safe and effective or
will have improved
         safety and efficacy over conventional AAV vectors and instead refer to
the relevant
         objective data from your preclinical trials or studies that relate to
your product candidate's
         performance.
5.       We note your disclosure here and in the Business section regarding
preclinical head-to-
         head comparisons between your targeted and evolved vectors with
relevant conventional
         AAV vectors. If you have not conducted actual head-to-head trials,
please revise your
         disclosure to clearly state this fact and disclose why you believe
these comparisons
         are appropriate. If you provide disclosure regarding results from
other trials, expand your
         disclosure to provide the other information regarding these trials
that would help an
         investor make a meaningful comparison (e.g, number of subjects,
dosage, how the
         baseline was measured in each study, etc.).
Our Product Candidate Pipeline, page 3
 David Kirn
FirstName LastNameDavid   Kirn
4D Molecular Therapeutics Inc.
Comapany 10,
November   Name4D
              2020 Molecular Therapeutics Inc.
November
Page 3    10, 2020 Page 3
FirstName LastName

6.       We note your disclosure on page 166 that planning is underway for an
IND-enabling GLP
         toxicology and biodistribution study of 4D-710 in NHP. Please revise
the pipeline table to
         shorten the line for 4D-710 and revise the anticipated milestone
accordingly. We also note
         that you have included in your pipeline table 4D-710, 4D-135, 4D-3XX
and 4D-7XX, all
         of which appear to be in the discovery phase. Given the early-stage
development of these
         programs, please explain why each program is sufficiently material to
your business to
         warrant inclusion in your pipeline table.
7.       Please explain what is involved in "lead-optimization" and why you
believe this is a
         separate and distinct development phase, as opposed to part of vector
discovery and/or
         IND-Enabling studies.
Implications of Being an Emerging Growth Company, page 7

8.       Please supplementally provide us with copies of all written
communications, as defined in
         Rule 405 under the Securities Act, that you, or anyone authorized to
do so on your behalf,
         present to potential investors in reliance on Section 5(d) of the
Securities Act, whether or
         not they retain copies of the communications.
Risk Factors
Our success depends on our ability to protect our intellectual property and our
proprietary
technologies, page 51

9.       Please revise this risk factor to disclose the patent rights or
technologies subject to march-
         in rights.
Use of Proceeds, page 86

10.      Please revise to clarify whether you expect that you will able to
complete the IND-
         enabling studies for 4D-150 and 4D-710 and the Phase 1/2 clinical
trial for 4D-125 using
         the proceeds from this offering.
Business
Our Proprietary Therapeutic Vector Evolution Platform, page 140

11.      Please substantiate your statement that you have the "largest and most
diverse portfolio of
         targeted and evolved vectors in the field of gene therapy."
Competition and Differentiation: AAV Gene Therapy for wet AMD and Diabetic
Retinopathy,
page 150

12.      We note your disclosure that, to your knowledge, 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 and is the
first gene therapy
         product candidate for the eye to directly inhibit three different
angiogenic growth factor
         targets, including VEGF and PlGF. Please revise these statements to
eliminate any
 David Kirn
4D Molecular Therapeutics Inc.
November 10, 2020
Page 4
         implication that 4D-150 is effective and to provide the data that
support these claims.
Strategic Collaborations, page 172

13.      Please provide the current expiration date for the last-to-expire
licensed patent right under
         the Roche Agreement, the uniQure agreements and the UC Agreements.
       You may contact Jenn Do at 202-551-3743 or Jeanne Baker at 202-551-3691
if you have
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
questions.



FirstName LastNameDavid Kirn                                    Sincerely,
Comapany Name4D Molecular Therapeutics Inc.
                                                                Division of
Corporation Finance
November 10, 2020 Page 4                                        Office of Life
Sciences
FirstName LastName