February 13, 2020

Jasbir Seehra, Ph.D.
Chief Executive Officer
Keros Therapeutics, Inc.
99 Hayden Avenue, Suite 120, Building E
Lexington, MA 02421

       Re: Keros Therapeutics, Inc.
           Draft Registration Statement on Form S-1
           Submitted January 21, 2020
           CIK No. 0001664710

Dear Dr. Seehra:

       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
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

Draft Registration Statement Submitted on January 21, 2020

Our Biological Focus, page 2

1.     Please provide context for the strategic goals in the bulleted
discussion on page 2 to
       explain how each of the goals relates to the current offer. If the goals
will not be
       addressed with the proceeds of the offer, please disclose that these
goals will not be
       achievable without additional funding.
Our Pipeline, page 3

2.     We note the inclusion of ActRII and "Multiple ActRII variants" in the
table on page 3.
       Please expand the table and your disclosure to provide more information
about the
       company's progress with respect to pre-clinical trials for these
applications. If you have
 Jasbir Seehra, Ph.D.
FirstName LastNameJasbir Seehra, Ph.D.
Keros Therapeutics, Inc.
Comapany NameKeros Therapeutics, Inc.
February 13, 2020
Page 2
February 13, 2020 Page 2
FirstName LastName
         undertaken IND enabling studies for any of the treatments listed in
the table, please
         describe these studies in the disclosure. Alternatively, please state
in the disclosure
         surrounding the table where you are in the IND process.
3.       Please balance the pipeline table disclosure by stating the
approximate number of patients
         worldwide who could benefit from each of the therapies in the table or
otherwise clarify
         your estimate of the potential market size for each therapy. In this
regard, we note your
         statements (e.g., page 1) that you are focusing on "novel treatments
for patients suffering
         from hematological and musculoskeletal disorders with high unmet
medical need," as well
         as your statements that the total worldwide number of FOP patients may
be approximately
4.       Please add to the table a column for Phase 3.
Implications of Being an Emerging Growth Company, page 5

5.       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, page 11

6.       We note that there are references to foreign regulators and foreign
markets throughout the
         Risk Factors and other sections of your prospectus. Please revise to
explain what non-US
         markets, if any, you plan to enter, and what steps you have taken to
attain the necessary
         regulatory and patent approvals.
7.       We note references throughout the prospectus to risks and benefits
associated with orphan
         drug status. Given the small number of patients who may benefit from
certain of the
         treatments you are developing, please provide more information
concerning whether the
         company currently intends to seek orphan drug status for any of its
product candidates.
8.       We note your disclosure in the Risk Factors and throughout the
prospectus regarding the
         company's having conducted its phase 1 clinical trials in Australia,
through its Australian
         subsidiary, together with the information that foreign trials may not
be acceptable to the
         FDA. Please revise throughout the prospectus to include information
about how you will
         replicate the trials in the US, if necessary to gain FDA approval, and
how you will pay for
         the additional trials.
9.       We note your disclosure on page 60 and on page 150 that your exclusive
forum provision
         does not apply to actions arising under the Securities Act or the
Exchange Act. Please
         ensure that the exclusive forum provision in the bylaws (as effective
on the closing of the
         offering) states this clearly, or tell us how you will inform
investors in future filings that
         the provision does not apply to any actions arising under the
Securities Act or Exchange
 Jasbir Seehra, Ph.D.
Keros Therapeutics, Inc.
February 13, 2020
Page 3
Management's Discussion and Analysis of Financial Condition and Results of
Determination of the Fair Value of Common Stock , page 83

10.      Once you have an estimated offering price or range, please explain to
us the reasons for
         any significant differences between the recent valuations of your
common stock leading
         up to your initial public offering and the estimated offering price.
Please also explain
         reasons for significant differences between prices at which you sold
preferred stock and
         valuations of common shares. This information will help facilitate our
review of your
         accounting for equity issuances.
Consolidated Financial Statements
Note 2. Research and Development Costs , page F-10

11.      For all periods presented, please disclose the amount of income earned
and costs incurred
         related to research and development activities of the Novo Nordisk
license agreement.
         Refer to ASC 730-20-50-1.

12.      Please provide us mockups of any pages that include any additional
pictures or graphics to
         be presented, including any accompanying captions. Please keep in
mind, in scheduling
         your printing and distribution of the preliminary prospectus, that we
may have comments
         after our review of these materials.
       You may contact Christie Wong at 202-551-3684 or Brian Cascio at
202-551-3676 if you
have questions regarding comments on the financial statements and related
matters. Please
contact Julia Griffith at 202-551-3267 or Dietrich King at 202-551-8071 with
any other

FirstName LastNameJasbir Seehra, Ph.D.                        Sincerely,
Comapany NameKeros Therapeutics, Inc.
                                                              Division of
Corporation Finance
February 13, 2020 Page 3                                      Office of Life
FirstName LastName