August 30, 2018

Thomas Gad
Founder, Chairman, President and Head of Business Development
Y-mAbs Therapeutics, Inc.
750 Third Avenue
9th Floor
New York, NY 10017

       Re: Y-mAbs Therapeutics, Inc.
           Registration Statement on Form S-1
           Filed August 24, 2018
           File No. 333-226999

Dear Mr. Gad:

       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
response.

       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

Summary
Overview, page 1

1.     Please expand your revised disclosure regarding the end points of the
Phase 2 Study 12-
       230 to define complete and partial tumor response. Please also revise
your disclosure here
       and in the Business section where you present efficacy results from your
studies to define
       these terms, as well as "stable disease." Also disclose the portion of
overall responses
       where you observed a complete response compared to a partial response.
 Thomas Gad
Y-mAbs Therapeutics, Inc.
August 30, 2018
Page 2
MabVax Sublicense Agreement, page 155

2.    Please revise your disclosure to include the royalty term and when the
MabVax-MSK
      license terminates or expires. Please also file this agreement as an
exhibit or tell us why
      you believe that you are not required to do so pursuant to Item
601(b)(10) of Regulation
      S-K.
        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
statement.

       You may contact Rolf Sundwall at 202-551-3105 or Kevin Vaughn at
202-551-3494 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Ada D. Sarmento at 202-551-3798 or Mary Beth Breslin at 202-551-3625
with any
otherquestions.



                                                            Sincerely,
FirstName LastNameThomas Gad
                                                            Division of
Corporation Finance
Comapany NameY-mAbs Therapeutics, Inc.
                                                            Office of
Healthcare & Insurance
August 30, 2018 Page 2
cc:       Dwight A. Kinsey, Esq.
FirstName LastName