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                            August 18, 2023

       Ken Song, M.D.
       President and Chief Executive Officer
       RayzeBio, Inc.
       5505 Morehouse Drive, Suite 300
       San Diego, CA 92121

                                                        Re: RayzeBio, Inc.
                                                            Amendment No. 3 to
Draft Registration Statement on Form S-1
                                                            Submitted August 4,
2023
                                                            CIK No. 0001825367

       Dear Ken Song:

             We have reviewed your amended 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.

       Amendment No. 3 to Draft Registration Statement on Form S-1, submitted
August 4, 2023

       Prospectus Summary, page 1

   1.                                                   We note your response
to prior comment 4 and your revised disclosure on page 3 noting
                                                        that the terms "partial
response" and "objective response rate" are defined by "RECIST
                                                        v1.1." Please revise
your disclosure further to specifically define these terms as they
                                                        appear in RECIST v1.1.
   2.                                                   We note your response
to prior comment 3 and your disclosure that you "believe [you]
                                                        have established a
leadership position in the emerging radiopharmaceutical therapeutics
                                                        modality through a
product-centric approach and have created a pipeline of multiple drug
                                                        and development
candidates in therapeutic areas with significant market opportunities."
                                                        Please revise to
describe what a product-centric approach means and how this differs from
 Ken Song, M.D.
RayzeBio, Inc.
August 18, 2023
Page 2
      or is superior to the approach of your competitors such that you believe
you are a leader in
      this space.
Our Programs, page 2

3.    We note your response to prior comment 5. With respect to the SSTR2 -
RYZ101 for
      "other cancers" row, we note your added disclosure that you "are
conducting analyses to
      assess SSTR2 expression in other cancers for purposes of determining
whether any other
      cancers may be suitable for further development." Please revise to state
which cancers
      you are analyzing at this time and additional detail concerning your
analyses conducted
      thus far. The "next generation binder" for "multiple cancers" row lacks
both a drug
      candidate and a more specific indication than "multiple cancers," you do
not plan to
      nominate a development candidate for this program until mid-next year and
there is little
      disclosure regarding this program. The "other" row similarly lacks a
target, a drug
      candidate and a more specific indication than "multiple cancers" and has
a "next
      anticipated milestone" of "n/a." Please remove your "next generation
binder" for
      "multiple cancers" row and "other" row for "multiple cancers" from the
pipeline table as
      these programs continue to not appear sufficiently material. You may
describe these in
      your disclosure, but they do not appear to be material enough for
inclusion in the pipeline
      table.
Phase 1b portion of the ACTION-1 trial in patients with GEP-NETs, page 129

4.    We note your response to prior comment 13 and your revised disclosure
noting that the
      starting dose for this trial was selected "based on prior third party
clinical experience with
      Ac225 DOTATE through academic clinical centers outside the United States
via
      compassionate use." Please revise this disclosure to provide further
details about the
      "prior clinical experience" noted here, including, but not limited to,
the data produced by
      those third parties.
       You may contact Gary Newberry at 202-551-3761 or Kevin Vaughn at
202-551-3494 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Joshua Gorsky at 202-551-7836 or Margaret Schwartz at 202-551-7153 with
any other
questions.



                                                             Sincerely,
FirstName LastNameKen Song, M.D.
                                                             Division of
Corporation Finance
Comapany NameRayzeBio, Inc.
                                                             Office of Life
Sciences
August 18, 2023 Page 2
cc:       Terren J. O'Connor, Esq.
FirstName LastName