United States securities and exchange commission logo





                              May 1, 2020

       John Valliant
       Chief Executive Officer
       Fusion Pharmaceuticals Inc.
       Two International Place, Suite 2310
       Boston, MA 02110

                                                        Re: Fusion
Pharmaceuticals Inc.
                                                            Draft Registration
Statement on Form S-1
                                                            Submitted April 3,
2020
                                                            CIK No. 0001805890

       Dear Mr. Valliant:

              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

       Background on Radiopharmaceuticals, page 2

   1.                                                   We note that you
highlight the worldwide sales of two third-party drugs, including one
                                                        drug that treats bone
metastases and another beta-emitting drug that is approved to treat a
                                                        subset of
neuroendocrine cancers. Please revise to remove this disclosure from the
                                                        Summary or explain to
us why you believe it is appropriate to highlight these particular
                                                        sales figures in your
Summary.
 John Valliant
FirstName LastNameJohn Valliant
Fusion Pharmaceuticals Inc.
Comapany NameFusion Pharmaceuticals Inc.
May 1, 2020
Page 2
May 1, 2020 Page 2
FirstName LastName
Our Platform, page 3

2.       We note your discussion on pages 4 and 5 indicating that you plan to
use imaging
         diagnostics to identify patients who are more likely to respond to
your therapies and that
         for FPI-1434, only those patients who meet predefined tumor uptake and
         dosimetry standards would be advanced into your clinical trials.
Please tell us, and revise,
         as applicable, to discuss whether the market for your drug may be
limited by patient
         specific factors, such as a person's ability to tolerate radiation.
3.       We note your disclosure that FPI-1434 is in development for the
treatment of solid tumors
         expressing IGF-1R, which is overexpressed in multiple types of common
solid tumors.
         Please revise here, and elsewhere as applicable, to indicate whether
you will be required
         to conduct separate clinical trials for each common solid state
tumors. As applicable,
         indicate whether you currently plan to conduct Phase 2 trials
targeting one or more of the
         solid state tumors discussed in the prospectus. If you will need to
conduct additional
         development work in order to identify the tumors to be targeted in a
Phase 2 trial, please
         discuss.
4.       We refer to the disclosure contained in the second bullet point under
the heading. Your
         disclosure in this section highlights the ability of Fast-Clear linker
technology to use
         multiple targets and classes of targeting molecules; however, it is
not clear from your
         disclosures that you or any third parties have tested this technology
in humans and/or have
         clinical data to support such performance claims. Please revise this
disclosure, and others
         contained in the Summary, to balance and provide context to any
performance claims
         concerning this technology.
Our Corporate History and Team, page 6

5.       Please describe the spin-out from the Centre for Probe Development and
         Commercialization that formed the Company. Please include a
description of the timing
         and terms of the spin-out.
Our Strategy, page 6

6.       With reference to your disclosure on page 29, please revise the third
bullet point on page 6
         to clarify that you expect to initially seek approval of some product
candidates as second-
         or third-line therapies for patients who have failed other approved
treatments.
Risks Associated with our Business, page 7

7.       With reference to your risk factor disclosure on page 19, please
revise the Summary to
         highlight that there have been limited assessments of the long-term
safety of targeted
         alpha emitting isotope therapies in humans, and that there may be
long-term effects from
         treatment with any of your future product candidates. Also, revise the
Summary to
         highlight your belief that you were a PFIC in 2019 and the adverse tax
consequences to
         investors resulting from a PFIC classification in any given tax year,
including additional
 John Valliant
FirstName LastNameJohn Valliant
Fusion Pharmaceuticals Inc.
Comapany NameFusion Pharmaceuticals Inc.
May 1, 2020
Page 3
May 1, 2020 Page 3
FirstName LastName
         reporting requirements.
Capitalization, page 83

8.       We note that all outstanding preferred shares, including the preferred
shares issued upon
         the redemption of the preferred exchangeable shares, will be converted
into common
         shares upon the closing of the offering. Please clarify in your
disclosures what will
         happen with the preferred share tranche rights upon the closing of the
offering.
Critical Accounting Policies and Signficant Judgments and Estimates, page 106

9.       Once you have an estimated offering price or range, please explain to
us how you
         determined the fair value of the common stock underlying your equity
issuances since
         January 1, 2019 and the reasons for any differences between the recent
valuations of your
         common stock leading up to the IPO and the estimated offering price.
This information
         will help facilitate our review of your accounting for equity
issuances including stock
         compensation and beneficial conversion features.
Business
Our TAT Platform, page 120

10.      We note your statement that the Fast-Clear linker was observed in
preclinical studies to
         clear 3.1 times the amount of non-tumor localized TATs compared to the
most widely
         used commercial linkers. Please revise your disclosure in this section
to describe the
         preclinical studies, the specific results and who conducted such
studies.
Note 14. Net Loss per Share and Unaudited Pro Forma Net Loss per Share, page
F-35

11.      We note on page F-8 that the pro forma balance sheet has been prepared
to give effect,
         upon the closing of a qualified IPO, to an additional 97,562.979
common shares. Please
         explain how you calculated the pro forma weighted average share amount
of 89,590,040
         on page F-36.
Exhibits

12.      Please file the Master Services Agreement and the Supply Agreement
with the Centre for
         Probe Development and Commercialization as exhibits to the
registration statement.
13.      Please file your license agreements with Genentech and MediaPharma, or
explain to us
         why they should not be filed pursuant to Regulation S-K, Item
601(b)(10).
General

14.      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.
 John Valliant
Fusion Pharmaceuticals Inc.
May 1, 2020
Page 4

        You may contact Nudrat Salik at (202) 551-3692 or Vanessa Robertson at
(202) 551-
3649 if you have questions regarding comments on the financial statements and
related
matters. Please contact Christopher Edwards at (202) 551-6761 or Joe McCann at
(202) 551-
6262 with any other questions.



FirstName LastNameJohn Valliant                          Sincerely,
Comapany NameFusion Pharmaceuticals Inc.
                                                         Division of
Corporation Finance
May 1, 2020 Page 4                                       Office of Life
Sciences
FirstName LastName