(Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K Commission File Number 001-39344 Fusion Pharmaceuticals Inc. (Exact name of Registrant as specified in its Charter) (State or other jurisdiction of incorporation or organization) 270 Longwood Rd., S. Hamilton, ON, Canada L8P 0A6 (Address of principal executive offices) (Zip Code) Canada Not Applicable (I.R.S. Employer Identificati ...