United States securities and exchange commission logo

                            June 2, 2021

       Rachel Haurwitz, Ph.D.
       President and Chief Executive Officer
       Caribou Biosciences, Inc.
       2929 7th Street, Suite 105
       Berkeley, California 94710

                                                        Re: Caribou
Biosciences, Inc.
                                                            Draft Registration
Statement on Form S-1
                                                            Submitted May 7,
                                                            CIK No. 0001619856

       Dear Dr. Haurwitz:

              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

             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 on Form S-1

       Prospectus Summary
       Overview, page 1

   1.                                                   Your statements that
your allogeneic CAR-T cell therapies have "best-in-class" potential
                                                        imply the likelihood of
regulatory approval and comparisons to other products and
                                                        product candidates. The
statements are speculative in light of their regulatory status.
                                                        Please remove the
"best-in-class" references.
   2.                                                   Please make the
following changes to your pipeline table:
                                                            Include all
clinical stages that must be completed before commercialization (i.e., add
                                                            columns for Phases
2 and 3).
                                                            We note the table
entitled "Programs under AbbVie collaboration" with
 Rachel Haurwitz, Ph.D.
FirstName  LastNameRachel  Haurwitz, Ph.D.
Caribou Biosciences, Inc.
June 2, 2021NameCaribou Biosciences, Inc.
June 2,
Page 2 2021 Page 2
FirstName LastName
              "undisclosed" targets that are only discussed briefly in your
description of your
              collaboration and license agreement with AbbVie. To the extent
these are material
              programs, disclose the targets and provide descriptions of these
programs. Otherwise,
              please remove them from the table or explain the basis for your
belief that they are
              material and should be included in your pipeline table.
                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
the discovery
              phases. While we will consider your response, we do not currently
believe that
              the lead optimization is distinct from the discovery phase and
should thus be depicted
              under the discovery column. A textual discussion of the program
is likely a more
              appropriate place to make distinctions regarding different
segments within a
              particular phase.
3.       We note your disclosure here and throughout the filing that you are
focused on advancing
         treatments for "clinically validated targets." Please balance these
statements throughout
         your registration statement with the disclosure on page 22 that no
products that use novel
         genome-editing technologies have advanced into clinical trials or
received marketing
         approval in the United States.
4.       You note on page 2 and throughout your filing that the February 2021
         with AbbVie is " is an external validation of our chRDNA
genome-editing technology."
         Please revise this statement and similar statements on pages 98 and
116 to remove the
         "external validation" language, as efficacy determinations are the
exclusive purview of the
         FDA or other regulators.
5.       Please balance your disclosure on page 2 and throughout your filing
that "CB-010 is
         currently being evaluated in a phase 1 clinical trial in patients with
relapsed or refractory
         B cell non-Hodgkin lymphoma" with the fact that you have not yet
enrolled patients in
         this trial. We note your disclosure to this effect on page 26.
Risk Factors
Our rights to develop and commercialize our product candidates are subject...,
page 57

6.       Please provide additional risk factor disclosure about the dispute
with Intellia
         Therapeutics. Specifically, disclose whether your inability to reach a
"final resolution"
         with Intellia would hinder your ongoing Phase 1 trial of CB-010 and
whether you would
         be able to continue clinical development of CB-010 if this dispute is
not resolved.
Industry and Market Data, page 88

7.       We note your statements regarding market data used in the prospectus,
including that the
         sources of the information do not guarantee the accuracy or
completeness of the
         information and that investors are cautioned "not to give undue
weight" to estimates.
         Please revise these statements to eliminate any implication that
investors are not entitled
         to rely on the information included in your registration statement.
 Rachel Haurwitz, Ph.D.
FirstName  LastNameRachel  Haurwitz, Ph.D.
Caribou Biosciences, Inc.
June 2, 2021NameCaribou Biosciences, Inc.
June 2,
Page 3 2021 Page 3
FirstName LastName
Results of Operations
Licensing and Collaboration Revenue, page 104

8.       Please describe and quantify for us revenue by license and
collaboration agreement for
         each period presented that includes reference to related information
in Note 4. In addition,
         clarify whether the "Private Company" is a related party, as
referenced on page F-8, or an
         unaffiliated company, as referenced on page F-21. Revise your
disclosure accordingly.
Management's Discussion and Analysis of Financial Condition and Results of
Critical Accounting Policies and Significant Judgments and Estimates
Stock-Based Compensation Expense, page 112

9.       Once you have an estimated offering price range, please explain to us
the reasons for any
         differences between recent valuations of your common stock leading up
to the planned
         offering and the midpoint of your estimated offering price range. This
information will
         facilitate our review of your accounting for stock compensation.
Please discuss with the
         Staff how to submit your response.
Strategic Agreements, page 143

10.      Please revise the descriptions of your strategic agreements as
appropriate to revise any
         references to "low-double-digit" and "mid-double-digit" royalties to a
royalty range within
         ten percentage points (for example, between twenty and thirty percent)
and to disclose
         the expected expiry of the last-to-expire patent licensed under the
11.      With respect to the Collaboration and License Agreement with AbbVie,
please disclose
         the fee that AbbVie must pay to expand from two Program Slots and the
         aggregate commercial milestones you may receive under the agreement.
12.      With respect to your Exclusive License Agreement with MSKCC, please
revise your
         disclosure to clarify whether the IPO would trigger a success payment.
13.      Please expand your discussion of the ProMab Agreement to disclose the
upfront payment,
         royalty term, and termination provisions.
14.      With respect to the Pioneer Agreement, please disclose the "certain
events" that permit
         either party to terminate the agreement.
Intellectual Property, page 147

15.      Please expand your intellectual property discussion to disclose the
number and type of
         patents that cover each of your product candidates and programs,
whether they are owned
         or licensed, the related jurisdiction, and the expiration year.
 Rachel Haurwitz, Ph.D.
FirstName  LastNameRachel  Haurwitz, Ph.D.
Caribou Biosciences, Inc.
June 2, 2021NameCaribou Biosciences, Inc.
June 2,
Page 4 2021 Page 4
FirstName LastName
Legal Proceedings
Intellia Arbitration, page 167

16.      Please disclose, if known, a general timeframe for when you expect to
negotiate economic
         terms based on the revised scope of the leaseback and whether you
believe that agreeing
         to these terms will resolve the conflict underlying the Intellia
Arbitration. If not, please
         expand your disclosure to discuss how the interim award determining
that the two patent
         families are included in the Intellia License Agreement impacts any
licenses or
         sublicenses that you have granted, if at all.
Licensing Agreement Transaction, page 193

17.      You disclose that you have a license agreement with a "private
company" controlled by
         Anterra that provides for milestone payments and royalty payments for
future sales of
         licensed products. Please disclose the material terms of the license
agreement, including
         the milestone payments and the royalty range, and file the agreement
as an exhibit or tell
         us why you believe such filing is not required. Refer to Item
601(b)(10) of Regulation S-
Principal Stockholders, page 197

18.      Please identify in footnotes to the table all natural persons who have
voting and/or
         investment power over the shares held by F-Prime Capital Partners.
Financial Statements
Note 2. Summary of Significant Accounting Policies
Revenues, page F-9

19.      Please expand your disclosures to describe the nature of your
         obligation associated with maintenance fees and when you satisfy your
         obligation. In this regard, while you disclose herein that you
recognize revenues
         associated with annual maintenance fees on a point in time basis on
each anniversary date,
         you also disclose on page F-23 that your deferred revenue primarily
results from customer
         payments received upfront for maintenance fees because these
performance obligations
         are satisfied over time. Please address this apparent discrepancy.
Refer to your disclosure
         on page 111 as well.

20.      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.
 Rachel Haurwitz, Ph.D.
Caribou Biosciences, Inc.
June 2, 2021
Page 5

       You may contact Franklin Wyman at 202-551-3660 or Jeanne Baker at
202-551-3691 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Dillon Hagius at 202-551-7967 or Irene Paik at 202-551-6553 with any
other questions.

FirstName LastNameRachel Haurwitz, Ph.D.
                                                          Division of
Corporation Finance
Comapany NameCaribou Biosciences, Inc.
                                                          Office of Life
June 2, 2021 Page 5
cc:       Ashok Mukhey
FirstName LastName