Sec Form 4 Filing - Christenson Johan @ Fusion Pharmaceuticals Inc. - 2020-06-30

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Christenson Johan 2. Issuer Name and Ticker or Trading Symbol Fusion Pharmaceuticals Inc. [ FUSN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O FUSION PHARMACEUTICALS INC., 270 LONGWOOD ROAD SOUTH 3. Date of Earliest Transaction (MM/DD/YY) 06/30/2020 (Street) HAMILTON, A6L8P 0A6 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Shares 06/30/2020 C 2,497,345 A 2,497,345 I See Footnote ( 2 ) Common Shares 06/30/2020 C 1,069,902 A 3,567,247 I See Footnote ( 2 ) Common Shares 06/30/2020 P 240,000 A $ 17 3,807,247 I See Footnote ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Class A Preferred Exchangeable Shares ( 1 ) ( 1 ) 06/30/2020 C 13,333,333 ( 1 ) ( 1 ) Common Shares 2,497,345 ( 1 ) 0 I See Footnote ( 2 ) Class B Preferred Exchangeable Shares ( 3 ) ( 3 ) 06/30/2020 C 5,712,216 ( 3 ) ( 3 ) Common Shares 1,069,902 ( 3 ) 0 I See Footnote ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Christenson Johan C/O FUSION PHARMACEUTICALS INC. 270 LONGWOOD ROAD SOUTH HAMILTON, A6L8P 0A6 X Signatures /s/ John Crowley, Attorney-in-Fact 07/02/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents Class A Preferred Exchangeable Shares of Fusion Pharmaceuticals (Ireland) Limited. The Class A Preferred Exchangeable Shares of Fusion Pharmaceuticals (Ireland) Limited are redeemable into Class A Preferred Shares of the Issuer. Upon the closing of the Issuer's initial public offering, the Class A Preferred Exchangeable Shares of Fusion Pharmaceuticals (Ireland) Limited were redeemed into Class A Preferred Shares of the Issuer on a one-for-one basis, which subsequently converted into Common Shares of the Issuer on a one-for-5.339 basis. The Class A Preferred Exchangeable Shares have no expiration date. ( 2 )The securities are held directly by HealthCap VII, L.P. ("HCLP"). HealthCap VII GP SA ("HCSA") is the sole general partner of HCLP and has voting and investment control over the Shares and Preferred Stock held by HCLP. The reporting person has an indirect interest in HCSA and is an employee of HealthCap VII Advisor AB. The reporting person disclaims beneficial ownership of Shares and Preferred Stock held by HCLP except to the extent of any pecuniary interest therein. ( 3 )Represents Class B Preferred Exchangeable Shares of Fusion Pharmaceuticals (Ireland) Limited. The Class B Preferred Exchangeable Shares of Fusion Pharmaceuticals (Ireland) Limited are redeemable into Class B Preferred Shares of the Issuer. Upon the closing of the Issuer's initial public offering, the Class B Preferred Exchangeable Shares of Fusion Pharmaceuticals (Ireland) Limited were redeemed into Class B Preferred Shares of the Issuer on a one-for-one basis, which subsequently converted into Common Shares of the Issuer on a one-for-5.339 basis. The Class B Preferred Exchangeable Shares have no expiration date.

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