September 10,
2018

Frederic Chereau
President and Chief Executive Officer
LogicBio Therapeutics, Inc.
610 Main Street, 3rd Floor
Cambridge, MA 02139

       Re: LogicBio Therapeutics, Inc.
           Draft Registration Statement on Form S-1
           Submitted August 13, 2018
           CIK No. 0001664106

Dear Mr. Chereau:

       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 submitted August 13, 2018

Our GeneRide Technology, page 1

1.     Please revise your pipeline table on pages 3 and 82 to remove the
programs that are in the
       discovery phase. Because you have not identified a product candidate or
target indication
       for these programs, it is premature to include them in a product
pipeline table. In addition,
       please revise the column headings to eliminate the implication that your
candidates may
       be closer to regulatory approval and commercialization than they are.
For instance, we
       note that with the use of separate columns for sub-phases of the
preclinical stage, it
       appears the preclinical stage is shorter than the clinical stage and
that a candidate that has
 Frederic Chereau
FirstNameTherapeutics, Inc. Chereau
LogicBio LastNameFrederic
Comapany 10, 2018
September NameLogicBio Therapeutics, Inc.
September 10, 2018 Page 2
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FirstName LastName
         completed the preclinical stage may be halfway through the development
process. Also,
         revise to create separate columns for phases 1 and 2.
Prospectus Summary
Overview, page 1

2.       Please revise the Prospectus Summary to disclose that you license your
core technology
         from Stanford University and the University of Texas and include
disclosure where
         appropriate regarding the risks of licensing such technology.
Risks Associated with Our Business, page 3

3.       Please expand the ninth bullet point in this section to provide
specific examples of the risk
         of not being able to maintain necessary rights to your product
candidates. In particular,
         please address the fact that you only have a non-exclusive license
from the NIH to the
         therapeutic transgene included in LB-001 for non-clinical, research
uses and not for
         clinical or commercial uses, as well as any risks stemming from your
license of your core
         technology from Stanford University and the University of Texas.
Implications of Being an Emerging Growth Company, page 4

4.       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.
Use of Proceeds, page 64

5.       Please revise your disclosure in this section to indicate how far the
proceeds from the
         offering will allow you to proceed in the Phase 1/2 clinical trial for
LB-001 in MMA.
         Please also disclose the amount and sources of other funds needed to
complete the
         Phase 1/2 clinical trial. Refer to Instruction 3 to Item 504 of
Regulation S-K.
6.       We note you will use a portion of offering proceeds for discovery and
preclinical
         development of additional product candidates using GeneRide
technology. To the extent
         offering proceeds will be used to advance any of the product
candidates you have already
         identified, such as LB-101 and LB-201, please revise to specify the
candidates, the
         amount of proceeds to be allocated to each, and how far in their
development you expect
         to reach with the proceeds.
Management's Discussion and Analysis of Financial Condition and Results of
Operations
Critical Accounting Policies and Significant Judgments and Estimates
Stock-Based Compensation, page 77

7.       Once you have an estimated offering price range, please explain to us
the reasons for any
         differences between the recent valuations of your common stock leading
up to the IPO
 Frederic Chereau
LogicBio Therapeutics, Inc.
September 10, 2018
Page 3
      and the midpoint of the estimated offering price range. This information
will help
      facilitate our review of your accounting for equity issuances.
Business
License Agreements, page 105

8.    We note your disclosure on page 38 that you currently have a
non-exclusive license from
      the NIH to an engineered methylmalonyl-CaA mutase gene, the therapeutic
transgene
      included in LB-001. Please include a description of the material terms of
the license
      agreement and file the agreement as an exhibit to the registration
statement, or tell us why
      this is not required. See Item 601(b)(10) of Regulation S-K.
9.    Please revise your disclosure to include the aggregate milestone payments
due under each
      of the license agreements and the royalty term of the license agreement
with Stanford.
Exhibits

10.   Please file the employment agreements described in page 127 as exhibits
to the
      registration statement. Refer to Item 601(b)(10) of Regulation S-K.
Please also file the
      January 2016 consulting agreements referenced in Note 13 to the financial
statements and
      the research agreement referenced in Note 15, or tell us why they are not
required to be
      filed.
General

11.   Please provide us proofs of all graphics, visual, or photographic
information you will
      provide in teh printed prospectus prior to its use, for example in a
preliminary prospectus.
        You may contact Franklin Wyman at 202-551-3660 or Angela Connell at
202-551-3426
if you have questions regarding comments on the financial statements and
related
matters. Please contact Irene Paik at 202-551-6553 or Mary Beth Breslin at
202-551-3625 with
any other questions.



                                                            Sincerely,
FirstName LastNameFrederic Chereau
                                                            Division of
Corporation Finance
Comapany NameLogicBio Therapeutics, Inc.
                                                            Office of
Healthcare & Insurance
September 10, 2018 Page 3
cc:       Marc Rubenstein, Ropes & Gray LLP
FirstName LastName